Document vQez5djXqaobLeZZzjBeNgdR

FILE NAME: Welding (WELD) DATE: 1937 DOC#: WELD030 DOCUMENT DESCRIPTION: Unpublished Report - Dust in Production of Oil Products - See pgs. 35-38 & Other Pages on Asbestos Insulation  -fj-M 5 ~Z-~r.S - 3 & r .:-V" . " & W ? k * ` ` . : M %h s . ' >i * . .v . ' .. * ' * . -.' - ..:<> ' ':..i?O:V.*/'<&"..**.`vr.;.-..TsV.;*--. *;#% *..'` v -- * ... * . 'v : ' - J ; > v > V v . 4* * ' * ' " DUST PRODUCING OPERATIONS ./ : - - ' J r- :' v : ' ' IN T H E : \ ; J-'-, .',V ''../jr.Y: \ & ; PRODUCTION OF PETR0LF.M PRDUtS T '! AND ASSOCIATED ACTIVITIES^ :?3 ' ' , I` 'If Ni*.? te T'*3 > 3A . A:M EDICO-SAFETYS U R V 't ^ * - >-5-.ih*:^..*:v -* BY v* " Roy S. Bon3b) M , ./E .M /, :.7 yC > T /:'., --v.'' l 'chief s a f e t y inspector .. W/VCWACW. COMPANY W . J . ) : . , .* . v... - ;VV;K - "'Y V * V- <' .'''il* .' "****., S M^r -* a FOREWORD BY - Willard J. Dho, M j * Ct.EFNNEFRRAlI MFEnD/ICAAlL O/tRECTTOO tJT; :E STANDARD CUL COMPANY j ' T ', " {. * \ I .Y- A -V* STANDARD IL COMPANY (N. J.) *t S*3 0 R O C K E FELLE R P L A Z A - ;.- NEW Y O R K ,N . Y, . ^ JULY - 1 9 3 7 V Y'* . T ' > * '* 4>i * --i V . .\ . *g r *T^*f "` - *' . *ho Part of this uluitTINMAYBE' OUf^lcToe 5 ^ . `CL;< t - WITHOUTYtWtTnTEoHi Pcw. -ss'iO.H'sC^-Ti&-i-:' i-Y-P '-o'IC-.i.;/ ^ .. A*<**-0-' t v. *.. *..:..'*Sfv* .iir;-i-v- - ^^ :v - I'.**V* . $Mm V;- yt\ FOREWORD B eoause i t is th e duty o f in d u s tr y to p r o te c t i t s employees and beo au se no com prehensive survey o f th e h azard s in c id e n t to oc c u p a tio n a l d u s t problem s had y e t b een made, i t was f e l t t h a t h e re was a n o p p o rtu n ity to re n d e r a s e r iv c e t o th e p e tro leu m in d u s try and i t s em ployees by making suoh a su rv ey . I t is hoped th a t th e inform ation p resen ted in th is b u lle tin w ill a s s i s t i n f in d in g p ro p e r answ ers t o some o f th e many q u e s tio n s w hich h av e r e c e n tly a r i s e n c o n ce rn in g t h e h e a l th h a z a rd s o f employ ees whose work in v o lv es exposure to d u sts o f v a rio u s o rig in . An a t te m p t h a s b e e n made t o c o n s o l i d a t e o p in io n s from t h e m ost e x p e r ie n c e d s tu d e n ts o f o c c u p a tio n a l- d u s t p ro b lem s t o show t h e r e l a t i v e h a z a rd s o f d u s ts and th e d u r a tio n o f ex p o su re which may prove ha m in i to the worker. Furtherm ore, a study of th e p rev alen ce o f d u st p a rtic le s oc cu rrin g in v ario u s operations in the petroleum in d u stry has been made and in c lu d e d in t h i s r e p o r tj a ls o a d e s c r ip t io n o f th e p ro te c tiv e d e v ic e s and equipment provided fo r th e p r o te c tio n of th e workmen, T his re p o rt should serve as a guide to o p eratin g executives and s a fe ty en g in eers in handling p erso n n el and in p ro v id in g adequate p r o t e c t i o n i n d u s ty o c c u p a tio n s . I t s h o u ld a l s o r e s o l v e many o f th e fe a rs and q u estio n s o f in d u s tria l w orkers in th e se occupations. The stu d y confirm s an opinion th a t d u sty o ccu p atio n s, th o r oughly u n d ersto o d and in t e ll ig e n tl y h an d led should r e s u l t in no serious d is a b ility . W i l l a r d J . Denno, M. D, G en eral M edical D ire c to r S ta n d a rd O il Company (N. J. ) MEDICO - SAFETY MEMORANDUM I DUST PRODUCING OPERATIONS IN THE PRODUCTION OF PETROLEUM PRODUCTS AND ASSOCIATED ACTIVITIES CONTENTS PAGE INTRODUCTION PART I - DUST AS A HEALTH HAZARD I II w III - IV - V - WRY IS THE DUST PROBLEM SO IMPORTANT?........... WHAT IS MEANT B I DUST ? . . o a t . . . . . . a . . . s e e s a a . a . . . s o WHAT ARE THE PHYSIOLOGICAL EFFECTS PRODUCED BY The I n h a l a t i o n o f D u s t....................... 044*O04a 9 9 9 9 9 9 9 9 9 # *99 S ilic o s is in G eneral.. . . . . . . . 4 # * * a 9 0 4 4 0 9 0 0 * 0 O 9 9 O * 4 i4 ee F irs t N atio n al S ilic o s is C onference.. . . . 4 0 0**00#00*O00 S ilicato sis. 9 * 9 9 9 9 9 9 *99*9 A s h e s t o s i s . . . 99. . 99 . 99. . . . . . . . . . . . . . 909900d9994de WHAT IS THE MAXIMUM PERMISSABLE DUST CONCENTRATION? Form ula For D e te r m in in g Maximum P e r m i s s i b l e C o n c e n tr a tio n o f S i l i c a i n The A ir B r e a t h e d . . . ............ .. 9009099990949 Safe Dust C o n c e n tra tio n s, Im pringer Sam ples. 9 00 99 0 0 0 9 # 0 0 0 HOW MAY THE CONCENTRATION AND CHARACTER OF INDUSTRIAL DUSTS BE DETERMINED?I 9 O 4 4 0 9 4 9 O 9 O 0 O 0 9 0 0 9 0 0 90 The Im p in g er-A p p aratu s The Z eiss K o n im e te r... 4 *94*09090090400 99*9999999*90000 The B ausch & Lamb D ust C o u n te r ......................... 4 0 0 4 * 0 4 9 0 9 0 0 9 *004409 2 2 3 4 4 5 7 7, 8 9 9 10,11 11 11 PART II - DUST PRODUCING OPERATIONS STUDIED WHAT ARE THE PRINCIPAL DUST PRODUCING OPERATIONS? I SAND-BLASTING. 13-15 II FILTERING OPERATIONS. 0000090090 15-27 A - F ilte r C lay o r F u lle rs Earth? What i s F i l t e r C la y o r F u l l e r s E a r t h ? . . O O 0 0 <3 o < 0 0 0 0 0 00000 How i s F i l t e r C la y M ined a n d P r e p a r e d ? . 0 o 0 0 0 4 e $ 0 < 9 0 S 0 9 9 9 0 9 0 9 0 How i s F i l t e r C la y Used? 9 0 0 0 0 9 0 0 0 0 Q 0 0 0 0 0 0 0 0 0 BS 0 0 0 3 11B u rn in g '1 C l a y . . . . . . . . 90 00 0 04 < 0 09 0 0 0 0 Charging F i l t e r s . . . . . . 099 0 4 0 9 4 9 9 e 0 Dumping F i l t e r s . . . . . . . . . . . . . . . . . . . . . . . . 9 0 0 0 0*00000 C om position o f F ilte r House A ir Borne D ust 4 0 0 0 0 00 0 0 0 9 C ontrol o f F i l t e r Clay Du s t . . . . . . . . . . . . . . . 15.16 16.17 17.18 18.19 19.20 20.21 21 22 B C ontact C lay? Main C o n s titu e n ts o f C o n tact C lays. . . . . . . . . . . What i s " F i l t r o l " and How i s i t P r o d u c e d ? . . . What i s th e C hem ical C om position o f F i l t r o l ? . How i s C o n ta c t C lay U s e d ? . . . . . . . . . . . . . . . . . . . . 0 9 00 22.23 23.24 24.25 25.26 -2 - PAGE C - Bone B la c k o r C h arred Bone* How i s Bone B la c k U s e d ............. ...................... ................................................. 26 I I - INSULATING OPERATIONS* A - What P h y s i o l o g i c a l R e a c tio n s a r e P ro v o k e d by I n s u l a t i n g Materi als?i***************#* 27 B - What A re The P r in c i p a l I n s u l a t i n g O p e ra tio n s and How Much D ust i s P ro d u ced D u rin g S u ch O p e r a t i o n s ? . . . . ............ * I n s u l a t i n g 12" S team L in e s ........................ ......................... .................... .. In s u la tin g a 750-Pound C racking C o il A c c u m u l a to r .......... In s u la tin g T re a tin g P la n t Acid S u c tio n L i n e . . . . . . . . . . . . . . . I n s u l a t i n g C ra c k in g C o il Hot O il L i n e s . . . . . . . . . ....................... D ism a n tlin g or Removing Old I n s u l a t i o n . . . . . . . . . . . . . . . . . . . . C rushing Scrap Ashestos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C ru sh in g Old Cork In s u la tio n # 27 27.28 28 28 28 28.29 29 29 IV - G1711TING OPERATI OHS t What I s G u n ite and How I s I t A p p l i e d ? .............................................. 29,30 30 V WELDING AND CUTTING OPERATIONS; A - W elding O p eratio n s; 1. E l e c t r i c Arc W elding..................................... What a r e C oated E l e c t r o d e s ? . ........................................................ What do These E le c tr o d e s C o n ta in an d What P r o d u c ts R e s u lt From T h e ir U se ?................. Viliat i s The Amount and What A re th e C h a r a c te r is t ic s o f Fumes o r D ust Produced By The V a rio u s E l e c t r i c Arc W eld in g O p e r a tio n s .............. What P h y sio lo g ic a l E ffe c ts on W elders is P ro d u c e d by The Use o f C o ated E l e c t r o d e s . . . . . . . ....... .. ,, 2. Oxy-Ae e t y 1 ene W e ld in g ............................................................................... .. Fumes o r Dust Produced by O xy-A cetylene We l d i n g . . , . . 30 30,31 31,32 32-35 35-37 37 37 B - Burning o r C u ttin g O p eratio n s; 1. W ith Oxy-Ac e t y 1e n e . . . . . . . o . . . . . . . . . ~ 3 7 ,3 8 Fumes or Dust P roduced by O xy-A cety len e B u r n i n g . . . . . . . . . . 38 2. W ith N a tu r a l G a s ....................................... .............................. .................. . . 38 C - H ealth H azards Produced by W elding and C u ttin g O p eratio n s., 38 VI - GRINDING OPERATIONS; What i s The C o m p o sitio n o f G rin d in g W heels? . . . . . . . . . Is A brasive Dust Harmful?,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - What a r e t h e More F re q u e n tly Used Types o f G rin d e rs . th e Q u an tity and C haracter o f th e Dust th e y Produce?.. . . . . . . , 39 39,40 40 r1 3 3 iV"s. 3 3 3 3 3 3 3 3 3 3 1 3 1 9 1 1 1 1 a a 3 3 3 3 3- A - TANDEM FLOOR TOOL GRINDERS. ............................ D u st Produced by Tandem F lo o r G rin d ers. B - TANDEM BENCH GRINDERS.................................................................... .. D u st P roduced by Tandem B ench G r in d e r s ............ ...................... C h a r a c te r is t ic s o f Dust Produced by Tandem B ench G rin d e rs , .......................................................... ......................... SINGLE FLOOR TOOL GRINDERS............................... D ust Produced by S ingle F lo o r G rinders. C h a r a c t e r i s t i c s o f D ust P ro d u c e d .............. * s *9 a * D - UNIVERSAL GRINDERS............................... ........... D u st P roduced By U n iv e rs a l G r in d e r s . . . C h a r a c t e r s i t i c s o f D ust P ro d u c e d ............ ** E - SURFACE GRINDERS............... .................................... D u st Produced b y S u r f a c e G r i n d e r s , .......... F - LANDIS TOOL GRINDERS........................... ................ D ust Produced by Landis Tool G rin d e rs.. a aaa * G =. YANKEE DRILL GRINDER. D ust Produced by Yankee D r ill G rin d er.. H - AUTOMATIC CIRCULAR SAW SHARPENING MACHINE, . . . o o o a a D ust Produced by Yankee D r ill G r i n d e r . . . . . . . 0*09 I - AUTOMATIC BAND SAW GRINDER. . o e o a D u st Produoed b y A utom atic Band Saw G rin d e r, J - AUTOMATIC BAND SAW LAP GRINDER.___ a a a e o a * * * D ust Produced by Lap G rinder K - PLANING KNIFE BLADE GRINDER. D ust Produced by Blade G r i n d e r . , o o a oa L - LINDERMAN CUTTER GRINDER.. . . . . . . . D ust Produced by C u tter G rinder, a a a o O o o o a a a O O 0 ' a a e a a o o o a a a -o a o a aa M GANG SAW BLADE GRINDER.. . . o o e OO 0 0 0 6 0 0 0 0 ' D u s t P ro d u ced b y Gang Saw B la d e G r i n d e r , . a e f l o o a e a e o o N EDGER SAW GRINDER. . . . . . . . . . . . . . . . 6S o 9 a B D u st P roduced b y E dger Saw G r i n d e r . . , . , CIRCULAR SLAB CUT-OFF SAW GRINDER. . . . . . . D u st Produced b y C u t-O ff Saw G rin d e r. . P - "HOG KNIFE" GRINDER,. . . . . . . . . . . . . . . . . . D ust Produced by "Hog K nife" G rinder, Q - CUTTER GRINDER, . . 9 9 9 0 I D ust Produced by C utter G rinder. . 0 0 0 0 0 0 91 What P r e c a u t i o n s S h o u ld Be A d opted F o r S a fe g u a rd in g T h o se Who Use G rin d in g W heels?. . . . . . . . . . . . . . . . . . . . . . V II AV - ~4~ PAGE C ontrol o f Dust from G rin d in g W heels. 48 HANDLING POWDERED OR PULVERIZED MATERIALS; A - LIME; (1) H ydrated Lime. . . . . . . . . . . . . . . . . . . . . . . . . ..0 ( 2) Lump Q uick Lime. .......................... .. What P h y s i o l o g i c a l E f f e c t i s P ro d u ced b y Lime D u s t . . . . . . . . . . . B - METALLIC ZINC DUST; T y p ic a l S c re e n A n a l y s i s . .......................... .. Dust Produced. . . . . . . . . . . . . . . . . . . . . . . . 90 What P h y s io lo g i c a l E f f e c t i s P roduced b y Z in c D u st, 49.50 50.51 51 51 51 51 C - ASBESTOS "FLOAT"; Dust Produced. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 9 0 0 0 0 9 9 P hysiological E ffect of ^sbestos P a r t i c l e s . . . . . . . . . M t * M 9 M ( 51,52 52 D - GROUND MICA; D ust P ro d u c e d ................... .. 0 0 0 0 0 9 9 4 O O 0 0O a * 0 0 * 09 52 P h y sio lo g ic a l E ffe c t of Mica Dust O 090O 990000000999O 52 E - SULPHUR; ( 1 ) S u lp h u r F l o u r ..................................... a a. O e e 0 0 6 0 e d 0 0 * 9 9 9 4 <l * 0 0 0 0 ( 2 ) C ru d e S u lp h u r ................... .................. s v a a e a a s e e a o a e e 0 0 0 0 0 P h y s i o l o g i c a l E f f e c t o f S u l p h u r . . . a e t. a 9 0 0 0 0 0 0 9 0 9 0 0 a O d o 52 5 2 ,,553 53 F - LITHARGE; D ust P ro d u ced . ...................................... .. N e c e s s a ry P r e c a u t io n a r y M easu res When Handl in g L ith a rg e ... . . . . . . . . . . . . . . . . . 09 9 0 6 0 0 0 53 9 0 0 0 9 a 53.54 G - SODA ASH; Dust Produced.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 a a0 0 0 a 54.55 H - TALC o r "SOAPSTONE"; Dust Produo e d . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 P h y sio lo g ic a l E ffe o ts Produced by Talo D u s t... 9 0 0 0 0 0 9 9 0 0 0 55 I - GRAPHITE; D u st Produc ed. ........................................... .. eooaooeoaooooi 55,56 J - SLATE FLOUR; D ust Produced.". . . . . . . . . . . . . . . . . . . . . eo 0 e0 o0 56 E ffe o t o f S la te F lo u r on th e Lungs. 57 K - GRINDING DERRIS ROOT; Dust P r o d u c e d . . . . . . . . . . To What E x te n t i s D e rris T o x i c ? . . . 9dd0aa0000 D9o9oeeooe 57 67 L - GRINDING FYRETHRUM FLOWERS; Dust Produced. , 57,58 M - MIXING AND PACKING "FLIT" POWDER; Dust Produced.. . . . . . . . 900009000 F illin g Cans. . . . . . . . . . 00 00 09 58 a a 58 -5. PAGE V I I I - CLEANING TUBES AND DRUMS? I _ CRACKING COIL SOAKING DRUMS? D u st P ro d u c e d ................. #90 0 0 9 9 0O09*800 58,59 I I - CRACKING COIL TUBES? Dust Producod. , , . . . . . . . . . . . . . . . . . . . . . . ...,.# 59 I I I - WATER HEADERS AND BOILER TUBES? D ust P r o d u c e d ......................................... ................ ............................................. 59 C o m p o s itio n o f D u st from F ro n t W ater W all H e a d e r . . . . . ................... 60 IX ~ FOUNDRY OPERATIONS? A POURING MOLTEN METAL INTO SAND MOULDS.......... 9 0 0 4 9 * 9 9 0 9 9 0 0 B "SHAKING OUT" CASTINGS................... .................. C CLEANING CASTINGS? " 0 0 0 9 t 9 il 0 0 ( a ) P r e l i m i n a r y C l e a n i n g .......................... ........ ? 4 4 4 8 9 0 9 0 4* 0 9 9 9 ] T um blast. . . . . a . . . . . . . . . . . , . . 0 O O 0 0 * 9 9 O * O 9 . * O O ( o ) S ly T u m b lin g M i l l . ........................................ (d ) Tumbling B a rre ls . 9099O90499499000O0 (e) A ir-B lasting. e 4 a 4 4 4 4 >444 ( f ) Rough Snagging Wheels. . . . . . . . . . . . . . . 9 * 9 9 9 9 0 9 9 0 0 0 9 0 9 9 ( g) F in e S nagging and P o lis h in g W heels.. 0 9 0 9 9 0 9 9 9 9 0 9 0 9 0 0 0 9 ( h ) C one G r in d in g W h e e ls ................................ . O 0 * a * 0 9 0 # 0 f t 0 9 9 A v e r a g e D u s t i n e s s o f C le a n in g Room A i r . . 0 0 4 I 4 0 0 9 * 0 0 0 0 9 9 9 D CORE MAKING,...................................................... ... E SEPARATION OF BRASS FOUNDRY SKIMMINGS. 0* 990 0 0 0 0 0 0 0 9 9 00 90 0 0 0 00 0 60,61 61 61 61,62 62 62 62.63 63 63.64 64 64 64.65 65 ' X - MASON8S OPERATIONS? I II III IV V VI TEARING OUT STILL FIRE BOXES.. . . . . . CHIPPING OR CUTTING CONCRETE.............. CHIPPING MORTAR FROM BETWEEN BRICK. CRUSHING FIRE BRICK,................................. SHAPING FIRE BRICK ON 'EMERY WHEEL.. DISMANTLING MASONRY................ 9 9 * 0 909 0 9 0 9 4 0 0 9 0 0 0 0 9 0 9 0 0 0 0 0 O O 0 0 0 O 0 0 0 9 9 99 0 0 0 0 9 0 0 0 9 99 90 00 0 0 0 9 0 0 9 0 9 0 0 9 0 0 e 0 0 9 0 9 * 0 Od0# * 09000 0 0 0 0 9 9 S 09 9 0 0 0 0 0 9 9 9 0 0 0 0 0 0 40OO9O09O009O0O0OO90O004 65 65 65,66 66 66 66 XI WOODWORKING OPERATIONS? A BOX SHOOK MANUFACTURE R@S S L Y / 0 9 4 0 0 4 8 O 0 0 9 4 4 < 9 9000 * 00008 0000990*4*9000* ~ ^1} ) (c ) (d) R .ip S L W iH ^ 0 * o s a 4 D 8 < 9 0 9 0 4 0 0 0 G ut o f Sawing . P3.EU3.ing a * 0 0 0 0 0 0 9 0 0 0 0 0 * o 0000909800 9 6 0 0 4 009 09 Dus t i n e s s o f S h o o k - F a c to r y A ir 4 4 9 9 3 4 8 9 9 0900000009000000 0 o e e 0 e o o a 0 o <9 a o 14 9 0 0 * 9 9 0 0 0 8 4 * 0 9 0 0 400* 00*0990804000 67 67 67 67,68 68 B - BELT SANDERS, SAND DISCS AND SPINDLES OR CYLINDERS? B e l t Sand e r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 (b ) Sand D iscs o r W h e e l s 68, 69 & j (o) Sand Spindles or C y lin d ers.. . . . . . . . , 69,70 C - MAKING WOODEN CRATES? (a ) Band Saws.. . . . . . . . 70 (b) R a ilro a d Saws. . . . . 70 -6 - ROCK EXCAVATION: A - DRILLING................................... B - RT,AST TNG................................. c - MUCKING..................................... D - DUST CONTROL MEASURES; ( a ) Wet D r i l l i n g and W e ttin g Down Rock W alls an d Muck P ile s (b ) G eneral V entilation ...**.. ( c) Dust E xhaust Hoods on D r i l l s and Cither Mucking O p eratio n s and L ocal S ources o f D u s t , . . . . . , . . . . . . (d ) P e rs o n a l P ro te c tio n by Means o f R e s p ira to rs and P o s i t i v e - P r e s s u r e M asks. ................................................. PAGE 70 71 71 71 71 71,72 72 PART III - MEASURES FOR REDUCTION OF THE DUST HAZARD HOW CAR THE DUST HAZARD B REDUCED? A DESIGN PLANT FOR DUST CONTROL... 74 B PROVIDE BUILDING VENTILATION............................... 74 C STORE DUSTY MATERIALS IN DUST-TIGHT B IN S.. 74 D ENCLOSE FATERIAL HANDLING EQUIRIENT............... e a 9 74 S ISOLATE DUSTY PROCESSES...... .............................. a I > < 74 F PROVIDE WET METHODS OF OPERATION...................... a 74 G DESIGN EQUIPMENT TO CONTROL DUST. 10 9 75 H PROVIDE EXHAUST SYSTEMS.. . 4 f ( 75 I ESTABLISH MAINTENANCE AND GOOD HOUSEKEEPING PROCEDURE,. 75 J PROVIDE RESPIRATORS. . . . . . . 0 ft 0 9 ' 76 ( a ) A ir P u r if y in g Types q f R e s p i r a t o r s ............ ............... .. ( b ) S u p p lie d A ir R e s p i r a t o r s .......................... ........... .. The A ir L in e R e s p i r a t o r , ................................................. A b ra s iv e B l a s t i n g R e s p i r a t o r ................................. ................ ( c ) A cceptance and Use o f P e rs o n a l R e s p ira to ry P r o t e c t i o n b y W orkm en,............................................ ( d ) U se, M a in te n a n c e and C a re o f R e s p i r a t o r s .......................... 76,77 77 78,79 79 79,80 80 WHAT MEDICAL CONTROL SHOULD BE EXERCISED IN THE SELECTION AND SUPERVISION OF MEN WORKING ON DUSTY JOBS?, ................................... PHYSICAL EXAMINATIONS. . . o * . . . . . . . . . . . . . . * * DESIRABLE PHYSICAL QUALIFICATIONS,................................................. RE-EXAMINATIONS........................................................ ..................................... T H E LIMITATIONS 80,81 80 81 81 CONCLUSION. 81,82 STANDARD OIL COMPANY ( Incorporated in New Jersey ) 30 Rockefeller Plaza New York, N. Y. MEDICO - SAFETY MEMORANDUM DUST PRODUCING OPERATIONS IN THE PRODUCTION OF PETROLEUM PRODUCTS AND ASSOCIATED ACTIVITIES INTRODUCTION - Long lo o k e d upon a s o b j e c t i o n a b l e , d u s t to d a y i s a l s o r e c o g n i z ed as dangerous - e s p e c ia lly w ith reg ard to o c c u p a tio n a l d ise a se (P neum oconiosis) and d u st explosions. S ince th e dust encountered in th e production of Petroleum products and a s s o c ia te d o p e ra tio n s a re n o n -ex p lo siv e under o rd in a ry w orking c o n d itio n s, no fu rth e r a tte n tio n w ill be devoted to th is phase o f th e d u st hazard. S tu d ie s have re v e a le d th a t th e tim e elem ent (ex p o su re) and th e c o n c e n tra tio n and si ze of th e d u st p a r tic le s are m ajor fa c to rs in producing h e a lth h azard s. Here to f o r e d if f ic u lty has been encountered in determ in in g ac tu a l d u st c o n c e n tra tio n s and s iz e s o f th e p a r ti c le s , b u t re c e n tly developed in stru m e n ts such as th e Z eiss Konim e te r and t h e B au sch & Lomb Dust C o u n te r make i t p o s s i b l e t o o b t a i n d u s t c o u n ts and e stim a te s iz e o f dust p a rtic le s w hich, w hile n o t a b so lu te ly a c c u ra te , are in d ic a tiv e o f the d u stin ess of th e area. The d a ta p re s e n te d in th i s memorandum a r e b a s e d upon m a te r ia l ta k e n from th e a v a ila b le li te r a t u r e on th e su b je c t, upon f ie ld in v e s tig a tio n s and conferences w ith te c h n ic a l s p e c i a l i s t s and upon 1008 a c tu a l d u st c o u n ts made w ith a Z e iss K onim eter, u s in g a 20 to 30 m icro n (a m icron i s a b o u t l/2 5 ,0 0 0 o f an in c h ) p o r c e la in f i l t e r . In th e re p o r t o f th e P re v e n tiv e E n g in eerin g Committee o f th e A ir H ygiene F o u n d atio n , P ro fe s s o r P h ilip D rinker o f H arvard, chairm an, and o th e r te c h n ic a l s p e c i a l i s t s on th e Com m ittee w rite s " I f th e b reath in g o f dust causes d is a b ility o f any s o rt - s ilic o s is is o n ly one m a n if e s ta t io n - th e n i t fo llo w s t h a t t h e r e m ust b e some d e g re e o f a i r c le a n lin e s s frofn w hich no d i s a b i l i t y w ill r e s u l t to th e av erag e man d u rin g th e average w orking p e rio d . "There is no s a tis f a c to r y m edical answer a t p re se n t to th is q u estio n , b u t th e e n g in e e r is m aking a bad m ista k e i f he l e t s men b re a th e heavy d u s t concen tr a tio n s o f any m a te ria l. I f no o th e r reason fo r d u st c o n tro l can be found, th e n one s h o u ld r e a d t r a n s c r i p t s o f some o f t h e r e c e n t s u i t s a t common la w i n w h ic h f a n t a s t i c dam ages f o r a l l e g e d s i l i c o s i s w e re g r a n te d t o men who b r e a t h e d d u s t c o n ta in in g l i t t l e o r no s i l i c a . The C o u rts and C om pensation b o ard s a r e n o t im p re s s e d w ith s u b t l e d i s t i n c t i o n s b e tw e e n d u s t s w ith 10? and 40% q u a r t z , e s p e c ia lly when m e d ic a l e x p e rts a r e r e l u c t a n t to make d e f i n i t e sta te m e n ts as to th e com parative sig n ific a n c e o f such d iffe re n c e s . " i t would be w e ll to r e a l iz e t h a t men w orking in d u sty tr a d e s s u f f e r f a r m ore from r e s p i r a t o r y t r o u b l e s o f a l l k in d s t h a n do men who w ork i n c l e a n a i r . The evidence th a t ex ce ssiv e d u s tin e s s o f any k in d i s harm ful is beyond a rg u - ft -2 PART I - DUST AS A HEALTH HAZARD I - WHY IS THE DUST PROBLEM SO IMPORTANT? - A lth o u g h th e s u b j e c t o f th e o f w orkers in dusty tra d e s has been reo eiT in g co n sid erab le a tte n tio n from students o f' i n d u s t r i a l h y g ien e f o r a number of y e a r s , th e s e rio u s n e s s o f th i s problem was n o t f u l l y r e a l i s e d u n t i l i t was b ro u g h t s h a r p ly t o o u r a t t e n t i o n by th e c o n s ta n t ly growl in g c o u n try - w id e wave o f l a w s u i t s i n s t i t u t e d i n b e h a l f o f t h e v ic tim s i n o u r common law c o u rts , by th e m agnitude o f th e generous v e r d ic ts awarded by th e ju r i e s and by a re c e n t d e c is io n of th e F ed eral C irc u it Court re v e rs in g th e s u b s ta n tia l award of a j u r y i n a New J e r s e y c a s e ( P e n n s y lv a n ia P u l v e r i z i n g Company v s , E ld r e d G. B u t l e r ) . Owing to th e s e d ev elo p m en ts, th e problem c a n n o t b e ig n o re d o r b ru sh e d a s id e as m erely a n o th e r form o f " ra c k e te e rin g " b y u n sc ru p u lo u s law y ers and c o n s p irin g d o o to rs . Dodging th e issu e cannot provide the needed so lu tio n because even th e m ost unscrupulous law yers oannot c re a te a p ath o lo g ic lung a t w ill and, furtherm ore, even th e most skep t i c o f c o ro n ers fre q u e n tly fin d s h im se lf c o rro b o ra tin g a d ia g n o s is by h is postm ortem exam ination, E nlightened in d u s tr ia lis ts and th e m edical p ro fe ssio n as w ell as th e bench and b a r , have came to th e r e a l i z a t i o n t h a t exposure t o o e r ta in k in d s o f d u st, such as th o se c o n ta in in g c o n s id e ra b le am ounts o f q u artz ( s i l i c a ) , has in c re a se d th e u n h ealth y b o d ily c o n d itio n and d e a th ra te from re s p ira to ry d is e a s e s i w hile m e tallio d u s ts , suoh as le ad and i t s compounds, have been a sso c ia te d w ith g en eral system io p o is o n in g o f w o rk e rs. " S i l i c o s i s " i s now a d e f i n i t e l y r e c o g n iz e d d is e a s e w hich i s d e stin e d to become one o f th e forem ost and m ost serio u s o f o ccu p atio n al d isea se s of th e fu tu re because th e number o f w orkers in d u sty tra d e s is la rg e r th a n alm ost any o th e r group exposed to a s in g le known in d u s t r i a l hazard . The M oC affrey A ct, whioh beoam e e f f e c t i v e S ep tem b er 1 , 19 3 5 , am en d in g t h e New Y ork C o m p e n sa tio n Law, in c lu d e d s i l i c o s i s as an o c c u p a tio n a l d is e a s e s u b je c t to com pensation h e a lth S ix te e n s ta te s , as w ell as th o se o f th e F ed eral Government and o f H aw aii, P u e r to R ic o , an d th e P h i l i p p i n e I s la n d s (U. S. D ept, o f L abor B u ll.N o .6 2 5 ,B u r.L ab o r S ta t i s t i c s ) , have Workmen's C om pensation A cts w hioh in o lu d e co m p en sa tio n f o r o c c u p a tio n a l d ise a se s, e ith e r expressly or by ju d ic ia l in te rp re ta tio n , o r sp e c ific occupational disease acts, II - WHAT IS MEANT BY "DUST"? A c c o rd in g t o W eb ster* s U n a b rid g e d D ic t io n a r y , "D ust" may be d e fin e d as f in e , d ry p a r t i c l e s o f e a r th o r o th e r m a tte r so comminuted t h a t th e y may b e r a is e d and w afted b y th e w indj t h a t w hich i s crum bled t o m inute p o r t i o n s | fin e , powder. As p o in te d ' o u t by P h i l i p D rinker in a p ap er re a d b e fo re th e Chem ioal S e c tio n of th e N a tio n a l S a fe ty C ongress (h eld in A tla n tic C ity , O ctober, 1 9 3 6 ), d u s ts in c lu d e a l l ty p e s o f d ry e a rth y p a r tio le s sm a ll enough to b e blown about by o rd in a ry a i r c u rre n ts . D ust su sp e n sio n s may be g e n e ra te d as th e r e s u l t of g rin d in g b la s t in g , o r com m inuting p ro c e s s $ or th e y may r e s u l t from th e h a n d lin g o f fin e ly d iv id e d m a te ria ls as in m ixing .p ro c e sse s, in sw eeping, o r th e blow ing about of wood f l o u r , p l a n t p o l l e n s , o r common ro a d d u s t . T h ere i s n o c h e m io a l l i m i t a t i o n im p lie d by th e te rm "d u st" w h ile th e ran g e in s iz e o f d u st p a r tio le s extends from th e s u b - m ic r o s c o p ic t o s m a ll sa n d g r a i n s , Mr. D. H a r r in g to n , C h ie f H e a lth an d S a f e ty B ra n o h , U, S. B u re a u o f M ines a d v i s e s t h a t d u s t a s a p p lie d t o h e a l t h and r e s p i r a t o r y c o n d itio n s may be w et as w e ll as d ry . Under some c o n d itio n s , suoh f o r exam ple as in w et d r i l l i n g i n m ines, th e e sc a p in g a i r from th e d r i l l h o le may ( i n f a c t g e n e ra lly do es) c o n ta in a c e r ta in amount o f en trapped s o lid m a te ria l w hich undoubtedly is wet r a t h e r th a n d r y , y e t i t re m a in s in t h e a i r s u f f i c i e n t l y lo n g in some in s ta n c e s a t l e a s t to be b re a th e d by th e w orkers t o c o n tr ib u te to p o s s ib le h e a lth tr o u b le . The s i z e o f d u st o f im portance from a h y g ien io sta n d p o in t a re th o se under te n m icrons. In f a c t , th e s iz e s found in in d u s tr i a l atm ospheres are u n d er two m iorons f o r th e l a r g e r m a jo r ity o f p a r t i c l e s , sa y 90 t o 95 p e r c e n t, F h y s io lo g io a lly , t h e r e a r e a l m ost as many d i f f e r e n t c l a s s i f i c a t i o n s o f d u s t as th e re a r e a u th o rs on th e s u b je c t. H ow ever, a c c o r d in g t o P r o f e s s o r D rin k e r (" D u s t, Fumes an d Smoke", I n t e r n a t i o n a l La b o r O ffic e , O ccupation and H ealth V o l.1, 930, P.603) a l l o f th e se c la s s if ic a tio n s -3 - a re w ith o u t much p r a c t i c a l im p o rtan ce, sin o e i n d a i l y p r a c tio e in in d u s try th e harm ful e f f e c t i s ex ero ised m ore fre q u e n tly by d u sts m o stly o f mixed o rig in . B esid es, what is m ost im p o rtan t is th e p h y s ic a l and chem ical c o n s titu tio n of th e d u sts and consequent l y t h e i r a c t i o n on t h e s y s te m . Ill - WHAT ARE THE PHYSIOLOGICAL EFFECTS PRODUCED BY THE INHALATION OF DUST? - To be harm ful from a r e s p ir a to r y v iew p o in t, d ust m ust be of s u f f ic ie n t fln e ss to pass through th e n asal f i l t e r s and be re ta in e d in th e a lv e o li (m inute a i r sacs) of the lu n g s. P a rtic le s found in au to p sied lungs are o f th e o rd er o f one m icron (a m icron i s l/lOOO o f a m illim e te r o r about l/2 5 ,0 0 0 of an in c h ) o r l e s s in s iz e - ab o u t th e s i z e o f t h e common b a c t e r i a . Some d u s t p a r t i c l e s fo u n d i n lu n g s a r e a s l a r g e as fiv e or s ix m icrons a lth o u g h th e se s iz e s are ra th e r ex c e p tio n a l. There a re fiv e d i s t i n o t types o f re a o tio n produced in man as th e r e s u lt of in h a l in g d u s t. T hese r e a c tio n s may be b r o a d ly c l a s s i f i e d , b ased on t h e p rim ary c a u s e , as follow st (a ) Those w hich r e s u l t in lu n g f i b r o s i s , ooramonly r e f e r r e d t o as pneu m o c o n io s is . T h e se d u s ts c o n t a i n f r e e s i l i c a , a s b e s t o s , e t c . How ev er, i t i s n o t n ecessary fo r fib ro u s tis s u e to be formed in o rd er fo r the d is e a s e to be c la sse d as "Pneum oconiosis". (b ) Those whioh a re to x io and a re absorbed in to th e blood stream such as le a d , cadmium, e tc . ( o ) Those w hioh r e s u l t i n w h at i s commonly r e f e r r e d t o a s m e ta l fume fever] such as zino oxide, eto, (d ) Those whioh a re a lle r g ic in c h a ra c te r, such organic d u s ts as p o lle n , p u lv e r i z e d wood and f l o u r , e t c . The b r e a t h i n g o f p u l v e r i z e d wood and flo u r is fre q u e n tly asso ciated w ith tu b e ro u lo sis. ( e ) Those commonly r e f e r r e d t o as "n u isan ce d u s ts " . T hese may cause i r r i t a t i o n o f th e r e s p ir a to r y t r a o t or p assag es and may oause con sid erab le discom fort, a lso headaches of th e dry "nasal" passage or s in u s ty p e an d e x p o su re t o them may be a s s o c i a t e d w ith a h ig h i n cidence of re s p ira to ry illn e s s . The r a t e and e x te n t o f th e s e re a c tio n s a re dependent upon th e r e s is ta n c e o f th e in d i v id u a l, th e exposure p e rio d (c o n c e n tra tio n o f p a r t i c l e s and le n g th o f exposure) tem p e ra tu re and hum idity o f th e a i r , r a t e o f work, and th e p e rc e n ta g e o f in g re d ie n ts whioh a re harm ful. Owing t o th e le n g th o f tim e re q u ir e d to o b ta in a r e a c tio n b y in h a la tio n m eth ods, th e U nited S ta te s B ureau of M ines and th e P u b lic H e a lth S e rv ic e adopted ab o u t tw elv e y e a rs ago, a m ethod o f in je c tin g sm all q u a n titie s o f th e d u s ts to be stu d ie d in to th e p e rito n e a l c a v ity of guinea p ig s, ("R esponse o f P e rito n e a l T issue o f Dusts I n tr o d u c e d a s F o re ig n B o d ie s" b y D r. Jo h n W. M i l l e r , D r. R. R. S a y e r s and Vim. P .Y a n t, Jour.A m er,M ed.A ssoc, S ep t, 22,1934 - Y ol. 103,pps. 907-911), I t was found th a t id e n - ' t i c a l r e a c t i o n s o c c u r i n e a c h an i ma l i n j e c t e d w ith t h e same d u s t u n d e r th e same con d i t i o n s and exam ined i n th e same tim e i n t e r v a l a f t e r i n j e c t i o n , T hese r e a c tio n s w ere e s s e n t i a l l y th e same m ic r o s c o p ic a lly as t h a t produced in th e lu n g s and th e g ro ss ap p e a ra n c e o f th e d u s t n o d u le s was s u f f i c i e n t l y d i f f e r e n t i a t e d t o a f f o r d a m eans o f c la s s ify in g th e p h y sio lo g ic a l response to th e d u sts. There a re th re e types of reactio n s An a b s o rp tio n or d is s o lu tio n of th e d u s t, A p ro life ra tiv e reaction. An i n e r t r e a c t i o n -4 - In th e in e rt re a c tio n , th e dust n e ith e r caused an in c re a se in th e siz e o f th e nodules n o r d is a p p e a re d from th e t i s s u e s ; in s te a d t h e r e was m ore o r le s s a change i n i t s d is trib u tio n . S oapstone, carborundum (S ilic o n C arb id e), je w e le r's rouge (F e rric O xide), a n th ra c ite co al, bitum inous coal and c e rta in f i l t e r c lay s have in e rt re a c tio n s, C alc i te , lim e sto n e , p re c ip ita te d , calcium c a rb o n a te , gypsum, and P o rtla n d Cement e x h ib it ed an a b so rp tio n re a c tio n . Q u artz, c h a t, c e r t a in f i l t e r c la y s and f l i n t produced a p ro life ra tiv e reaction, The p h y s i o l o g i c a l re s p o n s e t o t h e i n j e c t e d d u s t s w e re found s u f f i c i e n t l y w e ll marked in 90 days to determ in e th e ty p e o f re a c tio n , p a r tic u la r ly where th e re a c tio n was one o f a b s o r p tio n o r p r o l i f e r a t i o n . S in c e th e r e a c tio n e l i c i t e d by d u s t was o o n stan t and uniform in a l l o f th e anim als in je c te d w ith th e d u st, i t is b eliev ed th a t th is response of p e rito n e a l tis s u e to v ario u s d u sts can be used as a t e s t tp de te rm in e th e p o s s ib le harm fulnes's o f i n d u s tr i a l d u s ts . The fib ro s is -p ro d u c in g p ro p e rtie s o f a G eorgia f i l t e r clay (30-60 mesh grade) a sam ple o f American c o n ta c t clay and a German c o n ta c t c la y were te s te d b y th e I n t r a p e r i t o n e a l M ethod, tu id e r t h e d i r e c t i o n o f D r. R. R. S a y e r s , M e d ic a l O f f i c e r i n C h arg e, U. S. P u b lic H e a lth S e r v ic e . The G e o rg ia f i l t e r c l a y showed a n i n e r t r e a c t i o n w ith a s lig h t tendency tow ards a p r o lif e r a tio n in th e 90-day te s t . The American con t a c t c la y showed an i n e r t r e a c tio n w ith ev id en ce o f same s l i g h t a b so rp tio n or d is a p p e a ra n c e o f some p a r t o f d u s t i n th e 180-day t e s t s . The German c o n ta c t c la y c a u se d th e form ation of lig h t yellow ish-brow n nodules and as th e in te rv a l between th e in je c tio n and th e ex am ination in c re a se d th e n o d u les became somewhat f la tte n e d , b u t th e amount o f d u s t and th e ap p ro x im ate s iz e o f th e n o d u le rem ain ed th e same th ro u g h o u t th e e n tire period (90-days) of the te s t. T his can be considered an in e rt reac tio n ; b u t as th e d u st does n o t d isa p p e a r from th e peritoneum i t should be co n sid ered as po te n tia l ly harm ful though not as dangerous as pure s ilic a . In commenting on th e r e s u l t s o f th e t e s t s w ith th e G eorgia f i l t e r c la y and th e A m erican co n tact c la y , D octor Sayers ad v ised th a t th e r e s u lt s of th e t e s t in d ic a te d t h a t th e f i l t e r c la y is more harm ful th an th e American c o n ta c t clay because th e d u st rem a in s i n e r t i n t h e t i s s u e s a s t h i s was t h e l a r g e s t p o r t i o n o f th e d u s t and th e in e r t ap p earan ce o f th e le s io n s was th e m ost pro m in en t. The m o d ific a tio n o f th e re a c tio n in th e f i l t e r clay can be a ttrib u te d to th e presence of 5-10 per cent, q u artz ( P e tr o g r a p h ic ) , Gypsum in th e A m erican c o n ta c t c la y may a c c o u n t f o r th e s l i g h t ab s o rp tiv e reac tio n . D octor Sayers advises th a t an in e r t d u s t, i f b reath ed in s u f f i c ie n t c o n c e n tra tio n , may be h arm fu l. These t e s t s w ere made in acco rd an ce w ith th e p ro c e d u r e d e s c r ib e d i n R e p r in t # 1 6 0 8 , P u b lic H e a lth R e p o r t s , V ol. 4 9 , No. 3, J a n u a ry 19, 1934, pps, 80-89. The in h a la tio n o f d u s t g iv es r i s e to "P neum oconiosis" a term d e riv e d from th e G reek pneunon, lu n g s and k o n is , d u s t, and u sed to d e s ig n a te a p a th o lo g io a l c o n d itio n o f th e lu n g s caused by th e in h a la tio n o f any d u st. I t in c lu d e s SILICOSIS, a ohro n io disease, of th e lungs caused by th e in h a la tio n o f m inute p a rtic le s of fre e s ilio a ( S i02) d u st which produces a perm anent in q a p a c ita tin g a l t e r a t i o n o f th e lu n g tis s u e ; ANTHRACOSIS, t h e b la c k lu n g o f th e m in e r du t o c o a l d u s t j ANTHRACO-SILICOSIS, th e new est o f our m ineral d u st a ffe c tio n s and in tro d u c e d by th e U nited Stages P ublic H ealth S ervice as a r e s u lt o f th e ir s tu d ie s in th e A n th ra c ite D is tric t o f Pennsyl vania, This a ffe c tio n is th e re s u lt o f b reath in g a n th ra c ite coal dust th a t contains s i l i c a . The common name f o r t h e a f f e c t i o n i s " M in e r s ' A sth m a"; CHALICOSIS, t h e g ra y - b la c k lu n g o f th e ' s t o n e - c u t t e r due t o s to n e d u s tj ASBESTOSIS; i n a s b e s to s w o rk e rs due t o a s b e s to s d u s t j SIDEROSIS, d u e t o b r e a t h i n g d u s ts o f ir o n o re (The lu n g s a r e y e llo w o r re d from m e t a l l i c o x id e s g e n e r a l l y o f i r o n . ) j BYSSINOSIS, due t o o o t t o n p a r t i c l e s and v e g e t a b l e f i b r e d u s t, and PNEUMONOULTRAMICROSCOPICSILICOVOLCANOKONIOSIS, a s p e c i a l fo rm o f s i l i c o s i s c a u s e d b y u l t r a - m i c r o s c o p i c p a r t i c l e s o f silic e o u s vo lcan ic d u st. S ilic o s is , A sbestoeis, and S ilico-A nthracosis are th e only th r e e forms of pneum oconiosis which re q u ire p r a c t ic a l a tte n tio n . -5 - While th e ty p e o f pulm onary le s io n depends on th e p a r t i c u l a r d u st in h a le d , th e u n d e rly in g p a t h o lo g ic a l p r in c i p le i s th e same i n a l l form s o f t h e d is e a s e , nam ely, an u ltim a te fib ro s is and replacem ent o f th e e la s tic lung tis s u e by a hard u n y ield in g f i b ro u s t i s s u e . A ll o c c u p a tio n s t h a t e x p o se men t o l a r g e am ounts o f d u s t may g iv e r i s e t o p n e u m o c o n io sis b u t n o t n e c e s s a r i l y t o s i l i c o s i s . I t i s now g e n e r a l l y a g r e e d t h a t in o rd er to produce th e l a t t e r , ( s i l i c o s i s ) in h a le d s i l i c a d u st m ust reach th e lungs in a ch em ically uncom bined c o n d itio n , in v ery f in e p a r tic le s n o t more th a n te n m iorons (10/25,000 in c h ) in diam eter and in s u f f ic ie n t amount and over a s u f f ic ie n tly long p erio d o f tim e. In re la tiv e ly re c e n t l i t e r a t u r e i t appears th a t th e proponents o f t h e id e a t h a t o n ly " f r e e s i l i c a " i s h a rm fu l a r e b e g in n in g t o h av e some d o u b ts and t o h av e th e th o u g h t t h a t p o s s ib ly some s i l i c a t e s may u n d er some c o n d itio n s b e harm fu l, G enerally speaking, the necessary len g th o f exposure to produce s ilic o s is is in d ire c t proportion to th e size of th e d u st p a rtic le s and inverse p roportion to the d u st c o n c e n tra tio n and th e amount o f f r e e s i l i c a in th e dust. S i l i c o s i s i s c h a r a c te riz e d a n a to m ic a lly by a g e n e ra liz e d f ib r o s is o f th e lungs and c lin ic a lly by sh o rt n ess o f b re a th , d ecreased ch est expansion and a p ro g re ssiv e ly le sse n e d c a p a c ity fo r work w hich i s out o f p ro p o rtio n to th e o b je c tiv e p h y s io a l fin d in g s . The e f f e c t of ex posure to d u st such as s ilic a is cum ulative, th e ra p id ity of developm ent o f th e d is e a se d ep en d in g upon t h e tim e and am ount o f i n h a la ti o n . S i l i c o s i s may d e v e lo p to th e p o in t o f cau sin g symptoms only a f t e r s e v e r a l y e a r s exposure t o s i l i c i o u s d u s t, b u t i t may be p r o g r e s s iv e i n some c a se s ev en a f t e r e x p o s u re h as ceased and may c a u s e symp- . toms o r beoome d is a b lin g long a f t e r th e workman h a s l e f t th e en v iro n m en t t h a t caused t h e c o n d i tio n . Some may im prove o r a t l e a s t re m a in s t a t i o n a r y i n t h e a b s e n c e o f in f e c t i o n . W a tk in s - P itc h f o r d ( J .I n d , Hyg. 9 ,1 0 9 - 1 9 2 7 ) t e l l s o f W elsh m in ers who p assed t h e p h y s i o a l e x a m in a tio n f o r e n l i s t m e n t i n th e B r i t i s h Army, f o u g h t th ro u g h t h e W orld War, th e n came back t o E ngland, and d ie d o f s i l i c o s i s . U n f o r tu n a te ly , i t i s n o t s ta te d w hether th e se persons died from s ili c o s is com plicated w ith tu b e rc u lo s is . B rit t o n an d Head ( J , Am, M ed .A sso c, 96, 1928 - 1 931) g iv e m ore d e t a i l e d d e s c r i p t i o n s o f s im ila r la te n t cases in th e U nited S ta te s . S i l i c o s i s in G e n eral - I t i s g e n e ra lly a g re e d th a t s i l i c o s i s may b e d e fin e d as "A o h ro n ic d i s e a s e due to th e b r e a t h in g o f a i r c o n ta in in g s i l i c a (S i02), ch ara cterized anatom ically by g en era lize d fib ro tic changes and m ilia ry n o dules in b oth lu n g s, and c lin ic a lly by sh o rtn e ss of b re a th , d ecreased oh est expansion, le sse n e d c a p a c ity fo r w ork, ab sence o f fe v e r, in c re ased s u s c e p tib ility to tu b e rc u lo s is (some of a l l o f which may be p r e s e n t) , and by c h a r a c te r i s t ic ro e n tg e n o lo g ical findings. " In o th e r w ords, s i l i c o s i s i s a d i 3 ea.se o f t h e lu n g s i n w hich th e n o rm al lung t i s s u e i s r e p la c e d b y s c a r t i s s u e d u e t o b r e a t h i n g a i r c o n t a i n i n g s i l i o a d u s t . Un f o r tu n a te ly th e r e i s no known cu re f o r s i l i c o s i s - b u t SILICOSIS and n e a rly a l l o t h e r form s o f d u s t d i s e a s e s CAN BE PREVENTED, R eco g n izin g t h e w ide i n t e r e s t and even h y s t e r i a among a p p re h e n siv e em ployers a g a i n s t whom c la im s h a d b een f i l e d b y a la rm e d w o r k e r s , and t h e n e c e s s i t y o f th o u g h t f u l c o n s id e ra tio n o f th e s i l i c o s i s problem , th e S e c re ta ry o f L abor on A p ril 14, 1936 c a lle d th e F i r s t N a tio n a l S il i c o s i s C onference a tte n d e d by more th a n 300 p erso n s re p re s e n tin g w o rk ers, em ployers, S ta te and F ed eral A gencies, In su ra n c e com panies, and o th e r in te r e s te d g ro u p s. Four Com m ittees were o rg a n iz e d to stu d y s p e c ific phases of th e s i l i c o s i s problem s and assem ble th e e s s e n tia l f a c ts about s i l i c o s i s in a s e rie s o f re p o rts] a lso to p re se n t sp e c ific su g g estio n s fo r s ilic o s is p rev en tio n and s t r a i g h te n o u t o th e r d i f f i c u l t i e s t h a t s i l i c o s i s h as c re a te d . R e p o rts made by th e s e C om m ittees w ere fo rm a lly ad o p ted a t a second c o n fe re n c e held F e b ru a ry 2nd and 3rd 1937 i n W ash in g to n , fro m w hich we q u o te ? -6 - "W hile a few p e rs o n s may s t i l l b e o f th e o p in io n t h a t s u c h w o rk e rs " (W orkers having s i l i c o s i s ) " a r e ' through* and doomed to an e a r ly d e a th , every study conducted th u s fa r confirm s th e f a c t th a t th e g re a t m a jo rity o f th e se men w i l l n o t n e c e s s a r i l y p r o g r e s s from b a d t o w o rse. P e rh a p s i t may be w ise t o t r a n s f e r some w o rk e rs t o o t h e r em ploym ent, b u t many may be c o n tin u e d a t t h e i r re g u la r occupations i f known m ethods a re a p p lie d to c o n tro l th e d u st and i f s p e c ia l c a re is em ployed to p re v e n t th e developm ent o f tu b e r c u lo s is , pneumonia and o th e r lung c o m p lic a tio n s". "C o n trary to p o p u lar b e lie f, s i l i c o s i s i s slow to d ev elo p . U su ally i t tak es seven y ears or more o f exposure to s i l i c a dust fo r a w orker to c o n tra c t th e d ise a se . I t is sa id th a t a few cases have been known to develop in as sh o rt a p erio d as l - l /2 y e a rs, b u t th e s e were under extrem e and unusual co n d itio n s. On t h e o th e r h an d , many w o rk e rs h av e la b o r e d u n d er o r d i n a r y e x p o s u re s t o s i l i c a f o r more th a n 30 y e a r s w ith o u t d e m o n s tr a tin g an y t r o u b l e w h a te v e r t h a t could be diagnosed as s ilic o s is " . For th e convenient d iag n o sis of s ili c o s is or o f s ili c o s is com plicated by tu b e r c u lo s is , th e pulm onary changes a re c l a s s i f i e d in th r e e s ta g e s by D rinker & Hatch ( " I n d u s tr ia l Dust" - 1936), In th e f i r s t s ta g e , th e d is e a s e produces no d ia b ili ty . The v ic tim can work ju s t as w ell a s ev er. In th e second s ta g e , h is r e s p ir a tio n is a f f e c te d ; he is b o th ered by dyspnea or la b o re d b re a th in g . In th e th i r d sta g e dys pnea becomes sev ere and he is li k e l y to c o n tra c t pulm onary tu b e rc u lo s is , g e n e ra lly w ith f a t a l r e s u lts . W hether he c o n tra c ts tu b e rc u lo s is or n o t, th e advanced s i l i c o tic is fa r below norm al and is v e ry s u s c e p tib le to a l l r e s p ir a to r y d ise a se s. These th re e sta g e s of s i l i c o s i s can be d is tin g u is h e d by X -ray. Acom parison o f th e X -ray p la te s o f a s ilic o tic w ith th o se of a norm al p erso n o f lik e age and physique shows, in th e f i r s t s ta g e , d is tin c tiv e shadows, evenly d is trib u te d in both lu n g s . T hese may be m is s e d or m i s i n t e r p r e t e d by any b u t a n e x p e r t ; b u t t h e changes in th e second and th ir d - s ta g e s a re obvious even to a layman. I t i s , of c o u rse, es s e n t i a l t h a t th e X -ray p l a t e s be p r o p e r ly made. Dr. P a n c o st and Dr, P e n d e rg ra s s o f th e U n iv ersity o f Pennsylvania have given ex ten siv e study to th e in flu en ce of X-ray te c h n iq u e on th e d ia g n o sis o f s i l i c o s i s . P en d erg rass is o f th e o p in io n t h a t shadows and appearances o f f ib r o s is can be a c tu a lly produced by th e te c h n iq u e employed. Under o th e r c o n d itio n s, e x istin g f ib r o s is can be e n tir e ly m issed by use o f im proper te c h n iq u e . S i l i c a t e s a s a c l a s s a r e b y no means h a r m le s s . I t was p o in t e d o u t b y Dr, R, R. S a y e r s (U .S, P u b lic H e a lth B u l l e t i n 2 2 1 ) t h a t M in ers * C o n su m p tio n was r a t h e r com mon in t h e Broken H i l l d i s t r i c t o f A u s t r a li a w here th e ro ck c o n ta in s c o n s id e ra b le s i l l i m a n i t e (AI2 S iO s), fib ro u s ' s i l i c a t e , and a r a th e r low p e rc e n ta g e o f q u a rtz ( 1 2 . 2 3 / ) , The s t u d i e s o f Badham (R e p t. D ir , Gen. Pub, H e a lth , New S o u th W ales) g iv e con s i d e r a b l e s u p p o r t t o W. R, J o n e s ' ( J . Hyg. 15, 3 0 7 - 1933) c o n t e n t i o n t h a t s i l i c a t e s , p a r t i c u l a r l y th e f ib r o u s v a r i e t i e s , may w e ll b e th e c a u se o f pulm onary d i s a b i l i t y , Badham i n 1927 co in ed th e word SILICATOSIS t o co v er d i s a b i l i t y from t h e in h a la ti o n o f s i l i c a t e s . O th e r s i l i c a t e s s u c h a s T a lc (H2 Mg ( S i 0 3 ) ) 4 J S h a le ; K a o lin (H4 Alp S i2 0 g )| F e ld s p a r; C r y o lite , (Na3 AlFg ) j and p u re M ica g iv e much le s s s p e c if i c changes th a n q u a rtz . A m oderate f i b r o s i s may ap p ea r a f t e r exposure t o numerous m a te r ia ls b u t th is f ib r o s is is u s u a lly not d is a b lin g . A ccording to Dr. Lanza, " S ilic a to s is " i s n o t a recognized term in th is c o u n try and d is a b i lit y from th e in h a la tio n o f s i l i c a te s has not been proven. Dr, C ary P,, McCord ( in d . Med, J u l y 19 3 3 , p p s. 4 -1 2 ) s t a t e s t h a t a l l s i l i c a t e s ta k e n in to th e lu n g s, o f p a r ti c le s i z e cap a b le o f p a ssin g th e c e l lu la r membranes, are l i k e l y t o induce some f i b r o s i s i n e x c e ss o f norm al b u t th e p ro g re s s o f su ch s i l i c a to s is is not n early so rap id as fo r s ilic o s is . T uberculosis ra te s are high in s i l i c a te u s in g in d u s tr ie s . A n teced en t tu b e r c u lo s is , q u ie s c e n t, may f l a r e up as a r e s u lt -7 - o f exposure to s ilic a te dusts A sb esto sis - A ccording to a u th o r itie s c ite d by D rin k er & H atch in th e ir book " In d u s tria l D usts", th e pathology produced by asbestos is n o t lik e th a t of s ilic o s is . Dr, L, U, G a rd n e r o f S a r a n a c Lake i s o f t h e o p in io n t h a t t h e a s b e s t o s f i b e r s g ro u p ab o u t th e neck o f an a lv e o lu s and s h u t i t o f f , c a u sin g w hat i s known as " A te le c ta s is . T here is no d e f in ite m ig ra tio n or tr a n s p o r ta tio n o f th e d u s t p a r ti c le s to th e lymph n o d e s and no f ib r o u s n o d u le s . As t h e a t e l e c t a t i c a r e a s i n c r e a s e t h e r e d u c t io n i n lu n g a r e a c a u s e s s e r i o u s d y sp n ea o r l a b o r e r e d b r e a t h i n g . D r. A, J. L an za (U, S, H e a lth R epts. , 50j 1 - 1935) su g g ests th a t th e enlarged h e a rts noted fre q u e n tly in h is c a s e s o f second stag e A s b e s to s is may b e due to th e in c re a s e d lo a d on th e h e a rt. I t t a k e s m ore w ork t o pump b lo o d th r o u g h t h e f ib r o s e d th a n th r o u g h t h e n o rm al lu n g . Re c e n t p a th o lo g ic a l s tu d ie s from human lu n g s from c a se s o f a s b e s to s is have in d ic a te d a d if f u s e ty p e o f i n t e r s t i t i a l f i b r o s i s w ith a c e r t a i n amount o f emphysema. IV - WHAT IS THE MAXIMUM PERMISS ABLE DUST CONCENTRATION? - T h e re a p p e a rs t o be a w ide v a r i a t i o n in th e maximum c o n c e n tr a tio n o f d u s t w h ich m ig h t b e in h a le d w ith o u t s u b s e q u e n t i n j u r y t o w orkm en, Some d u s ts ( a s le a d ) a r e d e te r m in e d b y ch e m ic a l m ethods and th e c o n c e n tra tio n s in a i r a re recorded g ra v im e tric a lly as m illigram s per c u b ic m e te r. However, t h e a v a ila b le in fo rm a tio n on th e am ount o f le a d d u st t h a t is harm ful and th e m ethods o f d eterm in in g le a d a re b e t te r and more a c c u ra te than th o se fo r s ilic a dust. I t is ra th e r w ell agreed th a t an in ta k e of about 1.5 m illigram s of le a d a day, w hether th i s is acq u ired by b reath in g d u s t o r by d rin k in g w ater th a t con t a i n s le a d , i s th e maximum a llo w a b le q u a n t ity . O th e rs ( a s s i l i c a , w here s iz e i s a fa c to r in determ ining dangerous p a r tic le s ) , are u su a lly given by count. N either m ethod t e l l s th e w hole s to r y , b u t in b o th c a se s i t may b e p o s s ib le t o secu re th e in form ation necessary fo r th e purpose. The maximum s i l i c a d u s t c o n c e n t r a t i o n c o n s id e r e d p e r m i s s i b l e i n th e a i r b r e a t h ed by a workman a t any p o in t in th e norm al b re a th in g zone has n o t been d e f in ite ly e s ta b lish e d . There is co n sid era b le d if fer ence of opinion reg ard in g th e range of par t i c l e s th a t a re counted when u sin g th e P u b lic H ealth S e rv ic e te c h n iq u e and l i g h t f i e l d il lu m in a tio n . B lo o m fie ld o f th e U n ited S ta te s P u b lic H e a lth S e rv ip e and Brown o f th e U n ite d S ta te s B u re a u o f M ines c o n te n d t h a t th e y c o u n t p a r t i c l e s freon one m i c ro n and upw ard, or ev en 0 .7 m icron and upward. The I n d u s t r i a l Commission o f Wis c o n s in and i t s A d v iso ry C om m ittee, com posed o f b o th em p lo y ers and s c i e n t i s t s , how e v e r , a g r e e d i n 1932 on a t e n t a t i v e f i g u r e o f 15 m i l l i o n c o u n t a b le p a r t i c l e s u n d e r 10 m icro n s i n lo n g e s t d im e n s io n w ith f r e e s i l i c a c o n te n t o f 35 p e r c e n t i n a c u b ic fo o t o f a i r as determ ined by U nited S ta te s Public H e a lth S e rv ic e tech n iq u e. V a ria tio n s in f r e e s i l i c a c o n te n t w ill make p ro p o rtio n a l in v e rs e changes in th is s ta n d a rd . In th e case of p ra c tic a lly pure s il i c a , th e p erm issib le d u st count should probably n e v e r ex ceed 5 ,0 0 0 ,0 0 0 c o u n t a b l e p a r t i c l e s . By c o u n t a b l e p a r t i o l e s i s m eant t h o s e p a r ti c le s betw een 0.5 t o 10 m icrons in th e lo n g e st dim ension. P a r tic le s of th i s s i z e a r e th e ones t h a t a r e b e lie v e d to c a u s e th e g r e a t e s t damage and form no v i s i b l e oloud. Dust p a rtio le s s m a lle r than 0 .5 m icrons in th e lo n g e st dim ension are n o t o r d in a r i ly co u n tab le. D u st p a r tic le s la r g e r than 10 m icrons in lo n g e s t dim ension do n o t o rd in a rily reach p a rts o f th e lung where they can produce in ju ry of a re s p ira t o r y n a tu re . M ost i n d u s t r i a l d u sts h av e b u t few p a r t i o l e s above tw o o r th r e e m i c r o n s i n s i z e . They a r e u s u a l l y a b o u t 90 t o 95 p e r c e n t , b e lo w tw o o r t h r e e m ic ro n s and 50 p e r c e n t, below a b o u t 0 .5 to 0 ,7 m icro n s. An e x c e p tio n t o t h i s would b e a d u s t sam ple ta k e n clo se to th e p o in t o f g en era tio n o f d u st and b e fo re th e la rg e r p a r tic le s had tim e to s e t t l e out o f th e a ir . In South A frica th e fig u re is 1 m illig ra m p e r cu b ic m eter (o r 300 p a r tic le s p e r cu b ic c e n tim e te r, o r a p p ro x im a te ly 8 ,5 m illio n p e r c u b ic f o o t .) Dr. Lanza found in 1917 in th e Jo p lin , M isso u ri d i s t r i c t th a t w ith good en g in eerin g p ra c tic e , a fig u re of 1 m illig ram p e r 100 l i t e r s o f a i r could be a tta in e d , T his value a t tr ib u t ed t o L anza a p p e a rs to o h ig h i n co m p ariso n w ith th e S o u th A fric a n s ta n d a rd s . As th e r e -8 - a re 1 ,0 0 0 l i t e r s in a cu b ic m eter, i t would in d ic a te t h a t L a n z a 's e s tim a tio n re p re se n ts som ething of th e o rd er o f 80 m illio n p a r ti c le s p e r cu b ic fo o t. W ith good en \ g in eerin g p ra c tic e , low er co n cen tratio n s than th is can be obtained. In fa c t th e ex . y p erie n c e in South A fric a and a ls o th e p re se n t ex p erien ce in th is co u n try in d ic a te s I th a t i t can re a d ily be k e p t below o n e-ten th o f th is v a lu e by u sin g o rd in ary good p r a c tic e s . The U nited S tates P u b lic H ealth S e rv ic e in i t s re c e n t study in th e an th r a c ite reg io n of P ennsylvania, found th a t 50 m illio n p a r tic le s per cubic fo o t w ith 5 per c e n t, q u artz in th e co arse d u st and 10 m illio n p a r t i c l e s per cubic fo o t w ith 35 p e r c e n t, q u a rtz w ere a p p a r e n tly s a t i s f a c t o r y and o f te n w ere a t t a i n e d . The f i g u r e o f 10-20 m illio n p a r t i c l e s per cu b ic fo o t fo r g r a n it e d u s t w ith 35 p e r c e n t, q u a rtz c o n te n t is o fte n quoted from th e Vermont g r a n ite s tu d ie s o f th e U nited S ta te s P u b lio H e a lth S e r v ic e . From a c o n s i d e r a t i o n o f g e n e r a l e x p e r ie n c e , Cummings s u g g e s ts 6 m i l lio n p a r tic le s per cubic fo o t as a th resh o ld fo r d u sts high in q uartz. This fig u re is based upon a com bination of South A fric a , A u s tra lia n and American ex p erien ce b u t I lack s e n tir e ly any p u b lish ed d a ta in i t s su p p o rt. 1 A ccording to s tu d ie s quoted by P h ilip D rin k er and Theodore Hatch in th e i r book " in d u s tr ia l D usts" 10 to 20 m illio n p a r ti c le s p er c u b ic fo o t by th e im pinger sam pling m ethod, lig h t f ie ld co u n tin g is a reasonable fig u re fo r cement and lim esto n e. Recent work by D reessen confirm s th e u n iv e rs a lly accep ted o p in io n th a t d u sts h ig h in c a lc ite s and low in q u a rtz do n o t produce d is a b lin g f ib r o s is . The th re s h o ld fig u re o f 0,15 m illig ram per cubic m eter is given fo r lead d u st, presum ably lith a rg e and w hite lead , I or othei soluble lead s a lts . I I t sh o u ld be n o te d t h a t many o f th e d a ta w ere n o t d eterm in e d as th e H e d ic a l req u irem en t, b u t as b ein g a tta in a b le in good p r a c tic e and a p p a re n tly s a tis f a c to r y i from a s a fe ty stan d p o in t. I t should be fu rth e r n o ted th a t th e accepted fig u re s are only r e la tiv e due to th e in d e fin ite powers o f r e s is ta n c e of an in d iv id u a l which a re I an unknown q u a n tity . One in d iv id u a l m ight r e s i s t a p r o p o rtio n o f 200 p a r t i c l e s p er cu b ic c e n tim e te r, w h ile a n o th e r would r e a c t u n fa v o ra b ly to 50 p a r ti c le s , The work I e r ' s p h y sical co n d itio n p rio r to th e exposure is o f g re a t im portance, since a young, h ealth y in d iv id u al u su ally can stand a hig h er co n ce n tratio n or longer exposure before 1 th e f i r s t sta g e o f s i l i c o s i s is developed. However, f a r g re a te r in flu e n c e th a n p h y sical co n d itio n m ight be the a b ility o f th e nose and re s p ira to ry passages to a r I re s t dust. s In t h e i r re p o rt to th e N a tio n a l S i l i c o s i s C onference th e Committee on Pre v e n tio n o f S ilic o s is th ro u g h M edical C ontrol p o in te d out th a t sin ce stan d ard s of sa fe I atm ospheric d u st c o n c e n tra tio n , based on m edical fin d in g s have been e s ta b lis h e d fo r on ly a few in d u s tr ia l d u s ts , and in view o f th e f a c t th a t c o n sid e ra b le stu d y and in I v e s t i g a t i o n w i l l be r e q u ir e d to e s t a b l i s h s ta n d a rd s f o r o th e r in d u s t r i a l d u s ts , some t e n t a t i v e s ta n d a r d would be u s e f u l. I t was a l s o s t a t e d t h a t t h i s a r b i t r a r y s ta n d a rd I sh o u ld be based upon w hat i s b e lie v e d to be w ith in th e l i m i t s of good e n g in e e rin g p ra c tic e provided, i t w ill la rg e ly co n tro l the s ilic o s is hazard for most in d u s tria l I exposures. They, th e re fo re , su g g est th a t I "The maximum p e r m i s s i b l e c o n c e n t r a t i o n o f s i l i c a i n th e a i r b r e a th e d m ig h t be expressed by the follow ing f o r m u l a , ( D e t e r m i n a t i o n of dust co n cen tratio n I acco rd in g to tech n iq u e d escrib e d by U nited S ta te s P u b lic H ealth s e rv ic e in R e p r i n t No. 1520 from P u b lic H e a lth R e p o r ts , M arch 1 8 , 1932)? I M u ltip ly th e percentage o f free s i l i c a by th e t o t a l p a rtic le dust c o u n t. I f th e r e s u l t i s u n d e r 5 m i l l i o n , th e c o n d i t i o n may be con sidered perm issible. If th e re su lt is over 5 m illio n , th e condition may be c o n sid e re d to o high. For exam ple, I 1.0% f r e e s i l i c a w ith a n a v e ra g e t o t a l d u s t c o n c e n t r a t i o n o f 30 m illio n p a r t i c l e s p e r cu b ic f o o t would g iv e ,1 0 tim es -9 - 30 m illio n , w hich e q u a ls 3 m illio n (good p r a c tio e ) j 30$, w ith av era g e t o t a l d u st c o n c e n tra tio n o f 50 m illio n , would e q u a l . 3 tim e s 50, o r 15 m i l l i o n 9 ( u n s a t i s f a c t o r y ) T h is fo rm u la i s n o t a p p l i c a b l e t o a n y d u s t c o n t a i n i n g l e s s th a n 6$ free silica " T heodore H atch in h is a r t i o l e "Some F undam ental D ata on M echanical D ust T raps" (Tech Pub, No. 6 3 7 -A* 6 0 , Amer. I n s t , Min. & M et. E n g rs . , A u g ., 193 6 ) g iv e s t h e s e S a fe D ust C o n c e n t r a t i o n s , Im p in g er Samp l e s i ( L i g h t F i e l d , Low Power C o u n ts, ) Kind of Dust Maximum P e r m is s ib le C o n c e n t r a ti o n C o n ta in in g no S i l i c a . ...................................... C o n tain in g any sm all amount o f s ilio a * f r e e combined. . . . . . . . . . C o n ta in in g 20 t o 40 p e r c e n t. Free S ilic a , . . # . G re a te r th a n 40 per cen t. F re e S i l i c a . . . . ............................. 9 50 m illio n s p er c u b ic fo o t 9 30 11 un It 9 10 It nn 11 5 It n it It ( P r e f e r a b ly a s much l e s s a s p o s s ib le ) D r. R. R, S a y e r s , M ed ica l O f f i c e r in C h a rg e , I n d u s t r i a l H ygiene an d S a n i t a t i o n , U .S, P ublic H ealth Service in answer to a q u estio n as to p erm issible d u stin e ss w rites* "D uring re c e n t y e a r s , i t h as b e e n custom ary to recommend th r e s h o ld or p erm issib le dust lim its ranging from fiv e to te n m illio n p a r tio le s per cubio fo o t as determ ined by Public H ealth S ervice technique, e sp e c ia lly w ith d u st in which th e p erce n tag e o f f r e e s i l i c a is above f iv e p e r c e n t. There is no b asis fo r th e a p p lic a tio n o f th is c r ite r io n to a l l d u sts, b u t i t is g e n e ra lly c o n sid e re d a sa fe p r a c tic e and one which can be a tta in e d in most in d u s trie s by ex h au st v e n tila tio n , w e ttin g , or oth er m ethods o f dust co n tro l." As p o in te d out b y D rin k er and H atch ( " I n d u s t r ia l D ust" - 1956) i t i s u n fo rtu n a t e l y im p o s s ib le to e v a l u a te d u s t e x p o su re s w ith th e a r i t h m e t i c a l n i c e t y t h a t we sh o u ld have l i k e d y e t i t i s commonly c la im e d - by laym en - th a t p ro lo n g e d ex p o su re t o low c o n c e n tra tio n s is j u s t as s e rio u s as s h o rt exposures to heavy c o n c e n tra tio n s. T his claim i s c o n tra ry to a fundam ental law o f physiology. In d is o u s s in g th e sub je c t C lark and D rinker ( " I n d u s tr ia l M edicine" - 1935) rem ark th a t " . . . a su b -th re s h o ld stim u lu s (d u st in h a la tio n ) fo r a long tim e produces no re a c tio n w hereas a r e la t i v e l y b r i e f s u p e r - th r e s h o ld stim u lu s may cau se a r e a c tio n " . I f w o rk ers a re exposed t o sudden heavy c o n c e n tra tio n s , th e th re s h o ld v a lu e s su g g ested p re v io u s ly would be c o rre s p o n d in g ly low ered. However, m ost th r e s h o ld v a lu e s a r e Weighed -- an a v e ra g e o f th e ranges. V - HOW MAY THE CONCENTRATION AND CHARACTER OF INDUSTRIAL DUSTS BE DETERMINED? The p r o p e r tie s o f a d u st which d eterm in e i t s harm fu ln ess have been shown to be i t s com position, co n cen tratio n (th e q u a n tity suspended in th e in d u s tria l atm osphere), and i t s p a r ti c le s iz e . The methods used fo r th e d e te rm in a tio n o f th e c o n c e n tra tio n and c h a ra c te r of in d u s tria l d u sts v ary from a ro u tin e d u st count for th e purpose o f e v a lu a tin g th e e ffic ie n c y o f d u st c o n tro l methods to a d e ta ile d stu d y o f b o th th e c o n c e n tra tio n and the c h a ra c te r of th e d u st in connection w ith m edical and en g in eer in g survey s. The Im pinger A pparatus developed a t th e U n ited S ta te s B ureau o f M ines, P itts b u rg h Experim ent S ta tio n by George Smith and Leonard G reeriburg, (D escrib ed in R e p r i n t No, 1628 from t h e P u b lio H e a lth R e p o rts V o l. 4 7 , No, 1 2 , M arch 1 8 , 1932 pp, 654-675) has b een employed f o r more th a n 13 y e a rs a s a s ta n d a rd in s tru m e n t f o r d u st s tu d ie s . In th is ap p aratu s samples o f a i r are drawn in to an im pinger tube and fla sk w here th e d u st p a r tio le s a re throw n o r im pinged on a p rep ared w e tte d g la ss c o lle c t in g p la te , The r a te o f a i r flow i s fix e d a t one cubic fo o t p er m inute w h ile the d u ra tio n o f th e sam pling p erio d is dependent upon th e d u st co n c e n tra tio n . The a ir passes through an o rific e in th e bottom of the im pinger tube and s trik e s g la ss col l e c t i n g p l a t e w hioh i s subm erged i n 3 cm. d e p th o f d i s t i l l e d w a te r or some o th e r f lu id w ith s a tis fa c to ry w ettin g p ro p e rtie s , ( i f w ater is used as th e flu id in the im pinger, s ili c a p a rtic le s are d isso lv ed -- hence not a v a ila b le fo r counting -- unless th e la b o ra to ry (co u n tin g ) work i s done w ith in a few hours o f ta k in g th e sam ple, ) T h is a ffo rd s th e means fo r a c c u r a te ly d eterm in in g th e q u a n tity and s iz e o f th e par t i c l e s . The liq u id is th e n th o ro u g h ly shaken to o b ta in a u n ifo rm d is tr i b u tio n of th e p a r t i c l e s j f i l t e r e d to remove th o s e over 40 m icrons i n .s i z e and ag ain a g ita te d . Sam ples o f ap p ro x im ately 1 cc, a re ta k e n by means o f a p ip e tte and placed i n Sedgw ic k - R a f te r c o u n tin g c e l l s . The u s e o f a s u i t a b l e m icro sco p e eq u ip p ed w ith a W hipple m icrom eter d isc to aid in counting, w ill perm it th e d eterm in atio n of the number of p a r t i c l e s in one q u a r te r o f th e m ic ro s c o p ic f i e l d . From t h i s f ig u r e , th e number o f p a r t i o l e s o f d u s t in 1 cu, f t . can be c a lc u la te d . One s p e c ia l ad v an tag e o f t h i s ap p a ra tu s is th e fa c t th a t a n a ly s is o f th e sample can be determ ined by c o u n tin g , by w eig h in g or by chem ical a n a ly s is . The im pinger m ethod is n e ith e r sim ple n o r extrem e l y com plexj how ever, r e l i a b l e r e s u l t s c a n be o b ta in e d o n ly by w e ll t r a i n e d , compe t e n t and ex p erien ced in v e s tig a to r s . However, owing to th e w ide use o f th e im pinger in previous in v estig atio n s th a t have been c o rre la te d w ith the p ath o lo g ical findings, an im pinger should be used fo r any in v e s tig a tio n w hich is to in o lu d e p a th o lo g ic a l f in d in g s o r w here th e r e s u l t s a re t o be in tro d u c e d as ev id en ce i n c o u rt. Some s ta t e co d es on d u st c o n tro l re c o g n iz e th e im p in g er m ethod. The U n ited S ta te s B ureau of M ines has p r a c tic a lly com pleted th e developm ent o f a "M idget" im pinger w hich has most o f th e 'g o o d c h a r a c te r is tic s of th e im pinger b u t la c k s m ost o f i t s draw backs. This m id g e t im p in g er w ill soon be a v a ila b le and w ill g r e a tly s im p lify b o th sam p lin g and c o u n tin g . O ther devices a re a lso a v a ila b le fo r sam pling o f d u st over a continuous p eriod, nam ely, th e e le c tric p r e c ip ita to r , th e paper th im b le, th e e le c tr o s ta tic p r e c ip ita to r , and th e h o t w ire th erm al p r e c i p ita to r . The E n g lish a re w orking on a d u s t sam pling in stru m e n t which p r e c ip ita te s th e d u s t from th e a i r by th e rm a l means ("P h y sic a l M ethods f o r t h e E s tim a tio n o f t h e D u st H azard s i n I n d u s t r y " , b y H, L. G reen and H. H. W atson, P riv y C o u n c il, M e d ic a l R e s e a rc h C o u n c il, S p e c i a l S e r i e s No, 1 9 9 , H is M ajesty * s S ta tio n e ry O f f ic e , London, (1 9 3 5 )). The U.S. .B ureau o f M ines has been u s ing an e le c tric p re c ip ita to r sim ila r to those described by D rinker ("A ltern atin g C u r r e n t P r e c i p i t a t o r f o r S a n i t a r y A i r A n a ly s is ! I - An I n e x p e n s iv e P r e o i p i t a t o r U n it" by P. D rin k e r, Jour, In d . Byg, , V ol. 14, 1932, p, 364) f o r c o l l e c t i n g sam ples o f th e t e s t suspensions used in te s tin g m echanical f i l t e r re s p ira to rs fo r p e rm is sib ility , A number o f in s tru m e n ts a re a v a i la b l e fo r making d u s t d e te rm in a tio n s f o r con t r o l p u rp o s e s . Among t h e s e i s t h e K o n im e te r w h ich c a l l s f o r b u t l i t t l e s k i l l i n sam pling. I t is lig h t, sim p le and quick to h an d le, needs no power fo r o p e ra tio n and r e q u ir e s only a m icroscope fo r co u n tin g th e p a r tic le s . The Z e iss K onim eter c o n s is ts o f a m icroscope w hich g iv e s a m a g n ific a tio n of 200X, an a i r pump, a d u s t f i l t e r to remove v ery co arse dust p a r tic le s , a sam ple d isc and a m icrom eter ru le d in square m i l l i m e t e r s . The a i r pump d r iv e s a m e asu re d q u a n t i t y o f a i r a g a i n s t th e sam p le d is c w hich is covered w ith a s tic k y su b sta n c e (g ly c e rin e j e l l y ) . T his sample form s a d u st s p o t w hich can be examined under th e m icroscope fo r a g e n e ra l id e a o f th e n a tu re of th e d u s t and th e r e la tiv e q u a n titie s p re s e n t, or f o r an a c tu a l m easure, a " d u st count", w hich shows how many d u s t p a r t i c l e s a r e p r e s e n t i n one c u b ic c e n t i m e t e r o r i n one l i t r e o f th e a i r samples examined. The K onim eter h as been used v e ry w idely in -1 1 - South A fric a (F in a l R ep o rt o f th e Miners* P h th is is P re v e n tio n C om m ittee, Johannes b u r g , 1919, p. 1 0 ) and a l s o i n C anada. The U. S. B ureau o f M ines h a s a l s o u sed i t i n some o f i t s d u s t s tu d ie s . I n d is c u s s in g t h e v a lu e o f t h e K onim eter i n t h e i r r e c e n t book " I n d u s t r i a l D u st" (M cG raw -H ill Book Co. , Hew Y ork an d London - 193 6 ) P h i l i p D rinker and Theodore H atch o f th e H arvard School of P u b lic H ealth w rites " I t i s th e m ost compact and sim ple sam pling d e v ic e . Space is provided fo r t h i r t y sam ples on a s in g le d iso and no a u x ilia ry so u rce o f power is req u ire d fo r i t s o p e ra tio n . Grab sam ples can be c o lle c te d w ith speed and th e flu c tu a tio n s in d u stin ess and th e d ev elo p m en t o f d u st flo o d s can be re v e a le d in a way t h a t i s im p o s s ib le w ith more cumbersome a p p a ra tu s . South A frican ex p erien ce inv o lv in g th e c o lle c tio n o f thousands o f sam ples has shown th a t th e fig u re o f m e rit g iv e n by th e Koni m eter is d ir e c tly re la te d to th e amount o f p h th is is - produc ing dust in th e a ir . I t is a v alu ab le ro u tin e sam pling in stru m en t b u t b eca u se o f i t s low and s e le c tiv e e f f ic ie n c y , th e counts re p o rte d a re p ro b ab ly ,,co n sid erab ly below th e tru e le v e l and th e y a re n o t e a s ily compared w ith d a ta o b ta in e d in E n g la n d , f o r e x a m p le , w ith t h e Owens a p p a r a t u s , o r i n t h e U nited S ta te s w ith th e im pinger," E xperience has shown th a t c o n tra ry to D rin k e r's s ta te m e n t, th e K onim eter i f p ro p erly used, w ill give r e s u lts th a t agree very w ell w ith those obtained by th e use o f t h e Im p in g e r. The U. S. B u re a u o f M ines E x p e rim e n t S t a t i o n a t P i t t s b u r g h i n m aking some c o m p a ra tiv e s tu d ie s w ith th e K onim eter and th e Im p in g e r found t h a t an a v e ra g e o f f iv e K onim eter d e te r m in a tio n s was w ith in a b o u t two p e r c e n t, o f one im p in g er d e te rm i n a tio n . The re a so n f o r ta k in g an average o f in d iv id u a l r e s u l t s o b ta in e d by th e Koni m e te r, f o r com parison w ith th o s e o f th e Im pinger, is due to th e f a c t th a t th e Koni m e ter ta k e s an in s ta n ta n e o u s g ra b sample o f sm all volum es and owing t o th e h e tro g e n e ous n a tu re o f d u s t in a i r g ra b sam ples do n o t r e p r e s e n t th e av erag e c o n d itio n s . The Im pinger tak es a continuous sam ple of r a th e r la rg e volum es and is th e re b y re p re se n ta ti v e o f th e av erag e. For th e s e reaso n s, i f i t is d e s ire d to compare Konim eter r e s u lts w ith Im pinger r e s u lts i t is n ecessary to take s e v e r a l K onim eter samples d u rin g t h e c o u r s e o f t h e Im p in g e r s a m p le , in o r d e r t o o b t a i n a v e r a g e c o n d i t i o n s . Vie h a v e no c o r r e la tin g in fo rm a tio n o f th e K onim eter w ith th e 20 t o 30 m icron p o rc e la in f i l t e r a g a in s t th e sta n d a rd im pinger method. A Z e iss K onim eter, u s in g a 20 to 30 m icron p o r c e la in f i l t e r was used in m aking a c tu a l d u st co u n ts in ou r v a rio u s d u st p ro d u cin g o p e ra tio n s . The p a r ti o le s iz e and s iz e c l a s s i f i c a t i o n was e s tim a te d r a th e r th a n a c c u r a te ly m easured and computed. Only p a r tic le s te n m icrons or le s s in s i ze were counted s in c e i t is g e n era lly agreed th a t d u st p a rtic le s la rg e r th an te n m icrons in s iz e a re n o t p a r tic u la r ly pathogenic. O th e r m eth o d s i n common u s e a r e t h e Owens j e t d u s t s a m p le r ( " J e t D ust C o u n tin g A p p a ra tu s " by J . S. Owens, J o u r . In d . Hyg. ,V o l. 1 4 ,1 9 3 2 ,P. 5 2 2 ) , w h ich h a s r e c e n t l y b e e n m anufactured in th is co u n try and th e photographic d u st c o u n te r, developed by F ick len and 0 tt,, The 'Owens j e t d u s t c o u n te r i s u s e d i n t h i s c o u n tr y t o c o l l e c t sam ples f o r p a rtic le size d is trib u tio n determ inations. I t is used p rin c ip a lly in A ustralia fo r d e te rm in a tio n o f number c o n c e n tr a tio n o f a tm o sp h e ric d u s t o f i n d u s t r i a l h y g ie n ic im p o rta n c e . The l a t e s t d e v ic e f o r d e te r m in in g d u s t c o n c e n t r a t i o n s i s t h e B ausoh & Lomb D ust C ounter w hich was p la c e d on th e m ark et a few m onths ago. T his in stru m e n t con s i s t s o f a d a r k - f ie ld m ic ro sc o p e m ag n ify in g 200X, and a n im p in g in g a p p a ra tu s mounted on a common b a s e . The b a s e i s a h o llo w cham ber w ith t h e b o tto m h in g e d t o p ro v id e e a s y a c c e s s t o t h e d a r k f i e l d c o n d e n s e r an d a c i r c u l a r g l a s s sp e c im e n s l i d e . By m eans o f a hand pump, w hich is p a r t o f th e im p in g in g d e v ic e , a sam ple o f a i r i s drawn th ro u g h a m o isten in g chamber which has a t i t s low er end a narrow s l i t . The d u st i s d ep o sited through th is s l i t on to th e o ir c u la r specim en s lid e in th e form o f a ribbon. The s lid e can be ro ta te d u n t i l th e sam ple comes in to p ro p er p o s itio n fo r view ing w ith t h e m ic ro s c o p e , o r a maximum o f tw e lv e s a m p le s c a n b e c o l l e c t e d on th e s l i d e and th e n view ed. The s lid e s a re q u ic k ly rem ovable and re p la c e a b le . T his d u st c o u n te r is n o t designed fo r accu rate dust determ ination b u t ra th e r as an inexpensive device for roughly checking d u st c o n d itio n s. I t has n o t been a v a ila b le long enough fo r a thorough te s t in actual practice. The p r i n c i p a l o b j e c t i o n t o in s tr u m e n ts l i k e th e B au sch & Lomb D u st C o u n te r and t h e Owens j e t d u s t s a m p le r f o r d e te r m in in g num ber c o n c e n t r a t i o n i s t h a t t h e i r d u s t c o lle c tin g e ffic ie n c y decreases w ith an in c re a se in th e atm ospheric d u st concentra tio n and th e f a c t th a t th ey ta k e grab samples Sinoe th e m ajor p o rtio n o f dust p re s e n t in in d u s tr ia l atm ospheres is sm all enough to gain entrance to th e lungs, very l i t t l e a tte n tio n need be given to determ ina tio n s of the exact sizes of p a rtic le s. PART II - DUST PRODUCING OPERATIONS STUDIED WHAT ARE THE PRINCIPAL DUST PRODUCING OPERATIONS? - I n o r d e r t o d e te rm in e to what ex ten t i f any, w orkers in th e production o f petroleum products and asso ciated a c t i v i t i e s a re exposed to th e hazard o f b re a th in g d u s t, a su rv ey o f a l l d u s t produc in g o p e r a t io n s was made a t t h e v a r i o u s p l a n t s c o n c e rn e d . T h e se o p e r a t i o n s , l i s t e d in order of th e ir apparent degree of d u stin e ss, a re: I - SAND - BLASTING Due t o th e l a r g e amount o f f i n e l y d iv id e d s i l i c a d u s t p ro d u o ed by th e im p act o f th e g ra in s o f sand on th e su rfa c e o f th e o b je c t being clean ed , s a n d -b la s tin g is th e most dangerous s ili c o s is hazard encountered in our survey. S an d -b lastin g is used r a th e r e x te n siv e ly a t o il r e f in e r ie s fo r clean in g in s id e so ak in g drums, bubble to w ers, t a r s e p a ra to rs , run-down pans and s to ra g e tanks fo r m e tal in s p e c tio n and to perm it th e a p p lic a tio n o f g unite lin in g as a means of p rev en tin g co rro sio n , Header boxes or other sim ilar p a rts , tubes in bracking c o il f ir e boxes and re tu rn bends are san d -b laste d to p erm it a d e ta ile d and thorough exam ination fo r cracks and de f e c ts . S a n d -b la stin g i s a ls o employed in th e rem oval o f c o rro s io n from under f l o a t ing ro o f ta n k s; for rem oving roughness or r u s t from s te e l shapes o r ro d s; fo r clean ing b e l l caps, bubble p la te s , tr a y s , and pipe p r io r to p u ttin g them back in serv ice} a ls o on th e ends of tu b e s p re p a ra to ry to p la c in g them fo r r o l l i n g ; and fo r c le a n in g c a s tin g s which are to o la rg e or f r a g i l e to w ith sta n d b ein g tum bled. I t h as been u sed , to a lim ite d e x te n t fo r c le a n in g b u ild in g s and re n d e rin g window g la ss opaque. The c ra c k in g c o i l t u b e s , p ip e , b e l l cap s, t r a y s , h e a d e r-b o x e s and s i m i l a r ob je c ts a re u s u a lly sa n d b la s te d o u t-d o o rs in th e open a i r or in a more or le s s open s h e d , b o th lo c a tio n s b e in g a s f&r rem oved as f e a s i b l e from an y sh o p s, p ro c e s s u n it s o r o th e r w orking p la c e s. Coarse r iv e r sand is d isch arg e d th ro u g h a o n e -h a lf to th re e q u a r te r in c h n o zzle w ith com pressed a i r under a p re s s u re of 30 t o 90 pounds p e r s q u a re in ch . The men a t th e n o z z le s s ta n d to th e windward s id e o f t h e i r w ork and w ear a "H ealth g u ard " (C h icag o Eye S h ie ld Company) m ask, a S ly Sand B la s t H elm et o r a F r e s h A ir Hose Mask c o v e re d w ith a c a n v a s hood. The men a t t h e Sand B la s t M achines w ear " D u st S a fe " g o g g le s and a TL S. A, " Comfo" R e s p i r a t o r , The M ine S a f e ty A p p lia n c e s Company now h as a s a n d - b l a s t hood t h a t i s m e e tin g w ith c o n s id e r a b le a p p ro v a l b y in d u s try and a ls o by th e U n ited S ta te s Navy D epartm ent, A blow er i s a v a ila b le f o r s u p p ly in g a i r t o th e s e hoods t h a t c le a n s th e a i r . T h is same b lo w e r c a n be u se d i n connection w ith a ir-lin e re sp ira to rs. When s a n d - b la s ti n g i s done i n s i d e o f drums h av in g more th a n one o p en in g , such as so ak in g drums, an a i r siphon is p la c e d in th e low er m anhole w hich draws o u t th e d u st and allow s a co n tin u o u s c ir c u la tio n o f fre s h a i r through th e drum. In drums w here th e sip h o n cannot be used, th e a i r c i r c u la t io n is poor and th e .m e n work in s h i f t s ra n g in g from 30 m in u te s to an h o u r, d ep en d in g on th e s iz e o f th e drum and th e amount of a ir c irc u la tio n in sid e. They also wear an approved s a n d -b la s t helm et, l These sa n d -b la stin g jobs are n o t continuous ro u tin e o p e ra tio n s but a re p er fo rm ed when n e c e s s a r y b y men s e l e c t e d fro m th e Common L ab o r g a n g s o r t h e M ason' s De p a rtm e n t, The work is r o ta t e d so t h a t in most c a s e s i t o ccu p ies le s s th a n tw e n ty p e r c e n t , o f t h e w o rk e r1 s tim e and t h e r e i s an i n t e r v a l o f 15 t o 20 d ays b e tw e e n s a n d - b l a s t i n g jo b s . C o n s e q u e n tly , on t h e a v e r a g e , no one man i s e x p o se d t o m o re th a n | a com bined t o t a l of 400 hours d u rin g th e co u rse o f a y ear. In d is c u s s in g r o t a t i o n " o f men on s a n d - b l a s t i n g jo b s . Dr. G ehrm ann, M ed ic a l D ir e c t o r o f t h e du P ont Company w rote: " I t m ust be b o rn e in mind t h a t s i l i c o s i s i s a c u m u lativ e d is e a s e a n d , t h e r e f o r e , th e r o t a t i o n o f men i n t h i s ty p e o f w ork canno-h h n o n n cirio ro ^ -1 4 - as e n t ir e ly p re v e n tiv e . Assuming th a t a man works in an atm osphere o f s i l ic a d u s t fo r s e v e ra l m onths, d u rin g which tim e he is bound to ab so rb a c e r t a i n amount o f th e d u s t which p roduces perm anent damage in M s lu n g s j he i s th e n removed and th e p o s s i b i l i t i e s a re t h a t th e damage w hich is a lre a d y done w i l l be s u f f i c i e n t t o c o n t i n u e on and p r o g r e s s t o t h e p o i n t w h ere i n l a t e r y e a rs he w ill develop symptoms. " T h e r e f o r e , i f we ta k e t o r o t a t i n g men i n t h i s ty p e o f w ork we a r e fa c in g th e p o s s ib ility o f, in l a t e r y ears, developing a la rg e number of c a s e s o f a m o d e ra te s i l i c o s i s w i t h some p e rm a n e n t d i s a b i l i t y . The o n ly s a fe ex p ed ien t which can be used i s com plete p re v e n tio n and t h i s can only be done by e lim in a tin g th e d u s t." : ..... D u rin g our s u rv e y we fo u n d t h a t men engaged i n s a n d - b l a s t i n g , t h a t i s h a n d lin g th e n o z z le o r a tte n d in g th e s a n d - b la s t m achine, w ere more or l e s s p ro p e rly p ro te c te d w hile a c tu a lly doing th e work b u t o f te n tim es th e y removed t h e i r p r o te c tiv e eq u ip ment b e fo re g e ttin g co m p letely away from th e w orking area , A la r g e amount o f v e ry sm all p a r tic le s i s produced by a n a ly sis o f d u st samples c o lle c te d b o th outdoors and indoors th e f o llo w in g d i s t r i b u t i o n (P u b lic H e a lth B u l l e t i n No, 217 ~ quency b a s i s was found* s a n d -b la s tin g . In an during sand-blasting, p, 52) on a s i z e fre S ize Group in M icrons Per Cent o f Total 0, 00 0. 50 1, 00 1. 50 2. 00 2 .5 0 3. 00 3, 50 4, 00 4. 50 5 .0 0 5 ,5 0 - ,, 0 . 9 9 ............................ ............................ -- - 1. 99. ..................................... ........................ ?k.O 4JCP 4 9 3 99 4B44 4 4 9 0 ** - 99 a 4 e * o o 4 e s * * 4 $ 5 49 B3 13d99d*e 949i 6e o*6 1, 4 19. 7 34. 7 20. 3 12.6 5, 2 2. 8 1.6 1.1 0, 2 0, 2 0. 2 W hile i t has been estim ated th a t f r e e s i l i c a d u st p a r ti c le s , 1 m icron i n d ia m e te r, r e q u ire 8 hours to f a ll 6 f t . in s t i l l a i r j p a r tic le s 5 m icrons in diam eter re q u ire l e s s th a n 1 h o u r to f a l l th e same d is ta n c e . C o n sid e rin g t h i s f a c t , i t i s a p p a re n t th a t th e d u s t hazard from a p a r tic u la r o p eratio n may, even th o u g h c a rrie d o u t fo r s h o rt p e rio d s , be acu te th ro u g h o u t th e working day. In view o f th e f a c t t h a t th e con d itio n o f s t i l l a ir is ra re ly , i f e v e r achieved, and th a t dangerous p a rtic le s e x ist in s iz e s below one m icron, i t is e v id e n t th a t a h azard e x ists. F o rtu n a te ly m ost o f th e o u ts id e s a n d -b la stin g is done in more or le s s is o la te d lo c a tio n s which makes i t r a th e r im probable th a t th e re w ill be any u n sa fe s i l i c a d u st exposure t o o th e r workmen. However, should i t become n e c e s s a ry f o r any work to be done in th e v ic in ity of s a n d -b la s tin g o p eratio n s e ith e r on p ro cess u n its or th e sand b l a s t sh e d s o r y a rd s , i t sh o u ld be remembered t h a t th e r e may be s i l i c a d u s t in th e / u even though i t can n o t be seen. D ust counts as high as 5 ,3 4 4 ,1 6 0 p a r tic le s te n |j rons o r le s s p er cu b ic fo o t w ere found in sam ples ta k e n a b o u t 50 f e e t "downwind" ^.Vv^nd b lo w in g about 15 to 20 m ile s p e r hour) w h ile s a n d - b la s tin g c ra c k in g c o i l tu b e s j about 95% o f th e se d u st p a r tic le s appeared an g u lar c r y s ta llin e u nder th e K onim eter m icroscope and were about fiv e m icro n s or le s s in s iz e . Sam ples ta k e n about 100 f e e t "downwind" from s a n d - b la s tin g o p e r a t io n had c o u n ts as h ig h a s 1 ,8 1 2 ,4 8 0 p a r t i c l e s p er cubic fo o t. -1 5 - Dust count? as h ig h as 1 3 ,9 3 3 ,4 4 0 and a s low as 453,120 p a r t i c l e s p er cubic I ^ o t were found in sam ples ta k e n d u rin g th e f i l l i n g o f th e Send B la st M achine feed f: U p p ers. The h ig h c o u n ts w ere fo u n d when sa n d was s h o v e l l e d i n t o a s m a ll c i r c u l a r ^ '^scree n and shaken by hand, th e lo w er c o u n ts , when th e sa n d was sim p ly s h o v e lle d in to th e hopper. The average d u st produced by f i l l i n g or ch arg in g th e S and-B lasting M achines was 4 ,9 5 0 ,3 1 6 p a r t i c l e s , te n m icrons o r l e s s , p e r cu b ic fo o t. Dust counts as high as 4,984,320 p a r tic le s , te n m icrons o r le s s , were found in s a m p le s ta k e n i n s i d e a S a n d - B la s t in g Room w h ile c l e a n i n g c a s t i n g s . The a v e r a g e d u s t i n t h i s room d u r in g s a n d - b l a s t i n g was 3 ,8 7 3 ,6 2 5 p a r t i c l e s p e r c u b ic f o o t . About 80% o f th e se p a r tic le s were a n g u la r c r y s ta llin e th re e m icrons or le s s in s i z e and about 20% a p p e a re d ro u n d ed , q u a r t z - l i k e c r y s t a l s a b o u t t e n m ic ro n s i n s i z e . T h e re w ere a few r u s t- lik e s c a le s over te n m icrons in s iz e and a v e ry la rg e number o f m inute dark m e ta llic p a rtic le s to o sm all to be counted a c c u ra te ly . The d u stin ess o f th is opera tio n could be g re a tly reduced by th e use o f s te e l a b ra siv e s ex clu siv ely . A ll of th e sam ples fo r d u s t counts r e f e r r e d to above were tak en a t face le v e l i n th e v i c i n i t y o f workmen, A 6 , 000, 000- d u s t p a r t i c l e s p e r c u b ic f o o t i s t h e t e n t a t i v e maximum a llo w a b le l i m i t o f d u st p a r ti c le s c o n ta in in g f r e e s i l i c a o f a s i z e le s s th a n 10 m icrons recom mended fo r sa n d -b la stin g . II - FILTERING OPERATIONS The p ro cess of f i l t e r i n g is e x te n s iv e ly u sed in th e r e f in in g of petroleum P roducts to im prove th e c o lo r s t a b i l i t y and to remove im p u ritie s from m otor lu b r i- In ts and p a r a f f i n e w axes. The t h r e e m a te r ia ls m ost commonly vised fo r t h i s purpose a re F ilt e r Clay or F u lle rs E a rth , C o n tact Clay and Bone B lack. C o n sid erab le dust is produced by th e h an d lin g , ch arg in g and re c o n d itio n in g o f th e se m a te ria ls. A - FILTER CLAY OR FULLERS EARTH; What is F i l t e r C lay o r F u lle r s E a rth ? F i l t e r c l a y can n o t b e id e n t i f i e d from chem ical com position b u t c o n s is ts of s i l i c a , alum ina, ir o n and a lk a lin e e a rth s in v a ry in g p e rc e n ta g e s. The d is tin g u is h in g p r o p e r tie s a r e la c k o f p l a s t i c i t y and th e power to remove c o lo r from o i l s . There a re numerous d e p o s its of th i s c la y and o th e r f i l t e r i n g e a rth s in th e U n ited S ta te s} th e o ld e s t' and among th e m ost e x te n siv e a re th o s e found c lo s e t o th e F lo r id a - G e o r g ia l i n e , One o f t h e s e , a t A tta p u lg u s , G e o rg ia , s u p p l i e s a m a jo r p o r t i o n o f t h e c la y u sed b y t h e a f f i l i a t e d S ta n d a rd O il Company (New J e r s e y ) o r g a n i z a t i o n s . A t t h e m ine t h i s m a t e r i a l c o n t a in s on an a v e ra g e a p p r o x i m a te ly 32% s i l i c a and 45% m o i s t u r e . The a v e r a g e c o m p o s itio n a f t e r b e in g p r o c e s s e d and prepared for shipm ent is ap proxim ately; SiC>2. . . . .................................................. AlgOg............ . . . .................................... Fe203. . ..................................................... MgO. . . a . . . e t a . . . . . . . . . . . . . . . . Combined M o istu re . . . . . . . . . . . . . Free M o is t ur e . . . . . . . . . . . . . . . . . 67. 46 p er cen t 10. 08 ii it 2. 49 u 11 4. 09 it u 5, 61 n tr 6. 28 u it The c o m p a ra tiv e ly low d u s t c o u n ts found even in p la c e s w here th e r e was c le a n in g and a ` leep in g is no d o u b t due to th e f a c t th a t t h i s f i l t e r c la y is o f a r a th e r c o a rse n a ^ | ^ 6r e and w ith o u t a p p r e c i a b l e am o u n t o f f i n e s . There appears to be a w ide v a r ia tio n in th e com position and fre e s i l i c a con t e n t o f f i l t e r c la y s u sed i n E u ro p ean r e f i n e r i e s . "T erraria" a German F i l t e r c la y used in Poland shows; L o ss i n c a l c i n a t i o n ......... . . . . . . . . . 605 p e r c e n t F re e S i l i c a ( S i 0 2 ) ................................. 8 3 ,2 7 " " J A I2O3 and F6203................................. ...... 8 , 27 " " The f i l t e r c la y used in Roumania is r e p o r te d as h av in g 6 0 ,4 p er c e n t, f r e e s i l i c a o r 75,5% t o t a l s i l i c a t e s , " G ra n o s il" c l a y u s e d i n B elgium c o n ta in s ft t o t a l p e rc e n ta g e of 7 3 -1 /2 p e r cen t, o f s i l i c a t e s e x p re sse d as S i0 2 , The p e rc e n ta g e o f f r e e s i l i c a was not d e te rm in e d . How i s F i l t e r C la y M ined and P re p a re d ? - The d e p o s i t v a r i e s from 2 t o 12 f e e t in t h i c k n e s s , p r o b a b ly a v e r a g in g a b o u t 7 f e e t . T h e r e i s a n o v e rb u rd e n o f a b o u t 35 f e e t w hich i s removed b y an e l e c t r i c a l l y o p e ra te d d ra g l i n e o r a steam s h o v e l. The o la y is lo a d ed in to sm a ll c a r s , tra n s p o rte d to th e w et c la y sh ed where i t i s dumped on to th e d ry in g flo o r and d rie d fo r th re e days. I t is th e n picked up by orange p e e l b u ck ets, loaded in to p o rta b le d is trib u to rs and d e liv e re d to b e lt conveyors w hich d is c h a rg e t h e e a r t h i n t o r o l l e r c r u s h e r s where i t i s re d u c e d t o s i z e s up t o a maximum o f two in c h e s . From th e s e c ru s h e rs th e c la y goes t o seco n d ary c ru s h e rs w here i t i s r e d u ced t o a maximum o f o n e in c h . S in c e th e c la y i s m ore o r l e s s damp v e r y l i t t l e d u st is produced. The c la y is th e n tra n s fe rre d to tandem o i l - f i r e d ro ta r y d ry e rs , 50 t o 60 f e e t lo n g and s ix t o sev en f e e t in d ia m e te r. In th e 20 m inutes re q u ir e d fo r th e c la y to p ass th ro u g h th e d ry e rs th e v o l a t i l e and m o is tu re co n te n t i s reduced 40 t o 50 p e r c e n t, t o a maximum o f 15 p e r c e n t. T he a v e ra g e d u s t te n m ic ro n s o r l e s s in s i z e in sam ples ta k e n a t v a r io u s p o in ts aro u n d th e d ry e rs and c o n v e y o rs was 1 ,5 6 4 ,9 6 9 p a r ti c le s p er cu b ic fo o t. This r a th e r low d u st co u n t is th e r e s u l t o f th e in s ta lla tio n of hoods w ith ducts to exhaust fans placed over th e discharge p o in ts to th e conveyors o r e le v a to rs . About Q5% of th e s e d u s t p a r tic le s were an g u lar c r y s ta l lin e in appearanoe under th e K onim eter m icroscope and about fiv e microns or le s s in Izej about 15% were over te n m icrons in s iz e . The la rg e r p a r tic le s had rough edges Sind a p p e a re d t o c o n t a i n s e v e r a l s m a ll a i r b u b b le s . The c la y i s removed fro m th e d ry e rs to h o t ro c k c o o lin g ta n k s , th e n to a v i b r a t i n g sc re e n . The o v e rs iz e i s n e x t p u lv e r i z e d i n a r o l l e r m i l l and t h e p ro d u c t c o n v e y e d t o a s i f t e r . An e x h a u s t s y ste m f o r th e m i lls and e le v a to r s h as b een i n s t a l l e d . T h is p ro c e ss may be re p e a te d u n t i l th e d e s ir e d s iz e m a t e r i a l h as b een o b ta in e d and g ra d e d t o s ta n d a rd mesh s i z e s , t h e b e t t e r known o f w hich a r e 1 5 -3 0 , 3 0 -6 0 , 60-90, an d t h e 200 mesh. The 60-90 g ra d e i s p ro b a b ly t h e m o st commonly u se d i n t h e p e tro le u m i n d u s t r y v>hen d e c o lo r in g b y p e r c o l a ti o n , and th e 200 when c o n ta c tin g . However, th e 30-60 i s p r e f e r r e d by m ost o f our r e f i n i n g u n it s i n th e U n ite d S ta t e s . The s iz e s e l e c t e d i s a p p a r e n tly d e te rm in e d la rg e ly by th e ty p e o f re b u rn in g equipm ent. S c re e n t e s t s a r e made h o u rly to in s u re t h a t th e s iz e s a re w ith in th e s p e c i f i c a tio n s . Here 'a re two ty p i c a l s c re e n analyses} 30 - 60 GRADE FILTER CLAY Mesh P er Cent, Over 30 . , 30 - 40. 40 - 60. 60 - 82. T hru 82 . . T o tal 9 ,7 47. 5 40. 3 1. 5 1.0 100, 0 -1 7 - FIUES (100 - u p ) GRADE FILTER CLAY Mesh Over 97 ............ 97 - 1 5 7 ___ 157 - 2 0 0 ___ Thru 2 0 0 ............ T otal Per Cent. 0.6 22.7 8.0 68.7 100,0 There is v ery l i t t l e dust produced by th e s if ti n g operation. A ll of th e conn e c tio n s a re d esig n ed to be d u s t tig h t b u t th e re is some leakage. Samples o f a i r ta k en a t v a rio u s p o in ts around th e s i f t e r s w h ile in o p e ra tio n had an average o f 2,208,960 dust p a r tic le s le s s than ten m icrons per cubic foot. About 85$ of th e se d u st p a r tic le s w ere s lig h tly angular c r y s ta llin e in appearance and fiv e m icrons or le s s in s i z e j abo u t 15$ were s lig h tly rounded sem i-opaque te n m icrons or over in s iz e . The la r g e r p a r tic le s had sm all cracks or f is s u r e s and s e v e ra l sm all a i r b u b b les. Hen spend about two hours a day c le a n in g , r e p a ir in g or re p la c in g s i l k sc re e n s in th e s i f t e r s . Samples ta k e n during th i s o p e ra tio n co n tain ed an av erag e of 2,039,040 d u st p a r tic le s le s s than te n m icrons p er cubic fo o t. About 97$ o f th e se d u st p a r tic le s w ere angular c ry s ta llin e in appearance and fiv e m icrons or le s s in s i z e j about 3$ were opaque over fiv e m icrons in s iz e . A f te r b e in g s i f t e d and graded th e c l a y i s ready f o r shipm ent. The 30-60 mesh g rad e is p la c e d in b u rla p bags h o ld in g 128 pounds and lo a d ed in to r a il r o a d box o a r s j b o u t 400 bags t o a c a r on an av era g e. D ust co u n ts o f sam ples ta k e n d u rin g th e f i l i ng o f t h e b ag s w ith th e 3 0 -6 0 mesh g ra d e show t h a t t h e r e a r e from 7 ,5 8 9 ,7 6 0 t o 9,968,640 d u st p a r tic le s le s s than ten m icrons per cubio fo o t which in d ic a te s th a t a l l men engaged in bagging and h a n d lin g b ag s in th i s a re a should w ear approved r e s p i r a t o r s s u c h as t h e "M. S. A, Comfo", A bout 8 0 $ o f th e d u s t p a r t i c l e s i n sam p les t a k e n during th e f il lin g and han d lin g of the bags appear s lig h tly angular c r y s ta llin e under t h e m ic ro s c o p e and a r e f i v e m ic ro n s o r l e s s i n s i z e j 20$ a r e ro u n d ed c r y s t a l l i n e , t e n m icrons or over in size. B ulk L o ading o f r a i l r o a d box c a rs w ith th e 30-60 mesh g rad e produces clo u d s o f d u s t, b u t a m ajor p o rtio n o f th is du st i s a p p a re n tly la rg e r th an 30 m icrons in s iz e as sam ples tak en d u rin g th is bulk lo ad in g had an average of only 6,853,440 p a r tic le s , te n m icrons or le s s in s i z e p er cubic fo o t. The F ines (100-up) grade is p u t in to 128-pound c o tto n bags. D ust counts in sam ples ta k e n d u rin g t h i s o p e ra tio n showed t h a t th e r e w ere from 4 ,6 4 4 ,4 8 0 to 1 4 ,2 1 6 ,6 4 0 d u st p a r tic le s le s s th an te n m icrons per cubic foot in th e a i r being b reathed by th e f i l l e r s , w eighers, sew ers and tru c k e rs. About 80$ o f th e se p a rtic le s were rounded, sem i-opaque c r y s ta llin e in appearance under th e Konim eter m icroscope and fiv e m icrons or le s s in s i z e j 20$ were sem i-opaque c r y s t a l l i n e from a b o u t seven to f i f t e e n m icrons in siz e . There w ere a lso a la rg e number o f v ery sm all p a r tic le s about one m icron or le s s in size How i s F i l t e r C lay U sed? - Upon a r r i v a l a t t h e r e f i n e r y , t h e b ag s o f c l a y a r e removed from th e box cars by a crew of men u s u a lly from th e G eneral Labor D epartm ent! 4' " jo b b e in g r o t a t e d so t h a t th e same men do n o t do t h i s p a r t i c u l a r o p e r a tio n more y jn. p e rh a p s tw e lv e h o u rs tw i c e a y e a r on a n a v e ra g e . G oggles and "M. S. A. Comfo" jj^ p p ir a to r s a re g e n e ra lly pro v id ed . The c la y is e ith e r tru ck ed o r dragged to an aH e v a t o r o r c o n v e y o r h o p p er and dumped and t h e b a g s a r e p i l e d f o r s to r a g e . A t p o i n t s where th e c la y is receiv ed in b ulk, i t is unloaded by a la rg e wooden scoop p u lle d by a m otor d riv e n d ra g -lin e . U nloading, h a n d lin g , and dumping th e c la y is one o f th e -1 8 - d u s tie s t p a rts o f th e f il te r in g o p eratio n . The amount of d u s t produced is of course i t m pendent on how th e work i s done, th e v e n t i l a t i o n p ro v id e d , and th e c a r e u sed by th e d o in S H ere a r e scans a v e ra g e d u s t c o u n ts o f p a r t i c l e s l e s s th a n t e n mi~ .^ ro n s in sam ples taken d u rin g th e unloading o f bags of 30-60 mesh A ttapulgus clay P a rtic le s Per Cubic Foot U nloading and dumping b ag s (128 lb s . ) in to Hopper a t a S o u th e r n R e f i n e r y . ................................................. Dumping c la y from Bags in t o E le v a to r H opper a t a N o r th e r n R e f i n e r y . ................................. ............. .. H a n d lin g bags from S to ra g e and Dumping i n t o E le v a to r H opper a t a n o t h e r N o r th e r n R e f i n e r y . ........................ I n s id e Box C ar D uring U n l o a d i n g . . 9. . . . . . . . . . . . . " " 11 I n F i l t e r House Passageway b e in g used to T ruck Clay to E lev ato r hopper. . . . . . . . . . . . . . . . . . . . . . . . . A v e ra g e D ust P ro d u ced w h ile sw e ep in g up* i n s i d e c a r a f t e r unloading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5,403,456 2 ,2 3 7 ,2 8 0 755,150 1 ,1 1 0 ,1 4 4 372,924 339,840 651,360 A p p aren tly u n lo ad in g c la y in th e b u lk i s le s s d u s ty th a n h a n d lin g and dumping o f th e c la y in b ag s. Samples ta k e n d u rin g th e u n lo ad in g o f b u lk cla y gave th e s e average counts o f d u st under te n m icrons in size? I n s i d e c a r d u r i n g u n lo a d in g ............. ................................... 962, 880 p a r t i c l e s p e r c u b ic f o o t O utside " " " ................................................... 6 2 3 ,0 4 0 " " " " There i s o f co u rse more dust produced in th e v ic in it y o f b u lk u n lo ad in g th a n i s p ro duced when h a n d lin g and dumping c la y in bags. A f te r dum ping, th e new c la y is ta k e n by e le v a to r s and co n v ey o rs t o s to r a g e b in s w hich hold about 20 to n s each. This is a ls o a d u sty o p e ra tio n due to th e f a ilu r e to cover th e sto ra g e bin s or to p lace hoods over th e ju n c tio n p o in ts of e le v a to rs and b e l t co n v ey o rs. Samples ta k e n d u rin g th e f i l l i n g o f s to ra g e b in s w ith new c la y had th e s e av erag e d u s t counts of p a r ti c le s le s s th a n 10 m icrons in sizes: D ust " " " over " 11 Face B ins around e le v a to r s And co n v ey o rs d u ring f i l l i n g a t a N o r th e r n R e f in e r y ................. .. " & Conveyors w h ile f i l l i n g a t an o th er N orthern R e fin e ry . ......... .............................. .. " & Conveyors w h ile f i l l i n g a t a S o u th e rn R e f i n e r y .................................................... L e v e l on Walkway o v e r S to ra g e B in s N o rth e rn R e fin e ry w h ile F i l l i n g B i n . ........................ . . . . . . . . . . . . . . 1 ,9 1 0 ,4 3 2 4 ,2 7 5 ,8 4 2 4 ,5 3 1 ,2 0 0 2 ,3 0 7 ,7 7 6 D ust Counts as h ig h as 8,609,280 p a r tic le s p er cubic fo o t w ere found in sam ples tak en n e a r t h e d is c h a r g e o f one b e l t c o n v e y o r i n t o t h e to p o f a s t o r a g e bin A bout 90% o f th e s e d u st p a r tic le s appeared a n g u la r c r y s ta l lin e under th e Konim eter m icroscope and w ere f i v e m icro n s o r le s s in s i z e j a b o r t 10% w ere b la c k , o p aq u e, many s c a l e - l i k e in ap p earan ce and te n m icrons o r over in size "BURNING" CLAY - From t h e s t o r a g e b in s t h e c la y i s c o n d u c te d by c h u t e s a n d /o r 1^yc o n v e y 0 r s and e l e v a t o r s t o g as o r o i l f i r e d Wedge B u rn e rs o r R o ta ry B u rn e rs o r K iln s in w hich i t i s "burned" or r o a s te d , and th e n d isc h a rg e d in t o r o ta r y c o o le rs where i t i s c o o le d . Where a l l o p en in g s, c h u te s and e le v a to r o u tle ts a s w ell as th e ends o f r o ta r y c o o le rs a re p ro p erly en clo sed and an ex h au st duct is p la c e d over th e b u rn er, v ery l i t t l e d u st (an average of only 604,160 p a r tic le s , te n m icrons or le s s in s iz e -1 9 - p er cubic fo o t) is produced and no re s p ira to ry p ro te c tio n i s n ecessary . Three types a of burners or k iln s are used to reco n d itio n f i l t e r clay . Average d u st counts of p Jam ples tak en d u rin g th e o p e ra tio n o f th e se b u rn e rs g iv e a com parison o f th e amount o f dust ( p a rtic le s te n m icrons or le s s per cubic fo o t) produced by each; Type o f F urnace Feeding; About Furnace C oolers T otal General A v erag e___ Herman-Frasoh O il or Gas F i r e d . ................. Wedge Gas F ir e d ...................... R o ta ry " " ...................... 2,624,320.... 5 ,3 9 9 ,6 8 0 ___ 2 ,0 6 7 ,3 6 0 ___ 3 , 7 0 0 , 4 8 0 . . . , 2 ,7 3 2 ,8 8 0 ......... 1 , 5 2 2 , 4 5 9 . . . . 2 ,1 0 8 ,5 9 0 ......... 1 , 0 7 0 , 0 4 6 . . . . 3 ,1 1 5 ,2 0 0 .____ 2,990,542 2,395,971 1,818,206 The p re s e n t p r a c t ic e o f u s in g a com pressed th e v ario u s flo o rs o f th e Furnace House a t one o f je c tio n a b le due to th e ex ce ssiv e d u st (12,687,360 cu b ic fo o t) which is s t i r r e d up. a i r hose to c le a n up th e c la y on th e R e f in e r ie s i s p a r t i c u l a r l y ob p a r tic le s te n m icrons or le ss per About 90$ of th e d u st p a r ti c le s in''sam ples ta k e n d u rin g th e burning o f f i l t e r d a y were angular tra n s p a re n t c r y s ta llin e in appearance and fiv e m icrons or le s s in s iz e j 5% were round opaque, te n m icrons or over and 5% were rounded sem i-opaque, te n m icrons or over in siz e . Exposure to dust produced by burning or re c o n d itio n in g cla y is ra th e r lim ite d . U su a lly th e r e i s one fire m a n fo r each s h i f t o f e ig h t h o u rs , th r e e s h i f t s p e r 24 h o u rs and a p o rte r fo r th e day s h i f t only. Since one o f th e p o r te r ' s m ain jobs is to " c le a n - u p 1.' he i s exposed m ore c o n t in u o u s ly t o d u s t t h a n a r e t h e fire m e n , j CHARGING FILTERS - The c o o l e d , b u rn ed c l a y (3 0 -6 0 g r a d e ) i s conveyed t o th e f i l t e r s by means o f e le v a to r s and b e l t conveyors and charged th rough c h u te s from th e conveyor b e l t trip p e r a t a ra te o f from one and a q u a rte r to e ig h t tons per hour. These v e s s e ls hold from sev en to f i f t y to n s each. The amount o f d u st produced d u rin g th e charging operation depends upon th e grade o f cla y being handled, th e 'r a te of ch arg in g , th e p o s itio n o f th e c la y on th e conveyor b e l t , th e c o n d itio n o f th e convey o r b e lt, tr i p p e r and c h a rg in g c h u te j a ls o w hether th e to p manhole o f th e f i l t e r is l e f t open d u rin g th e f i l l i n g . A g e n e ra l av era g e o f 54 d u st counts made of sam ples ta k e n d u rin g th e ch arg in g o f f i l t e r s a t a l l o f our p la n ts u sin g 30-60 mesh A ttap u lg u s F i l t e r Clay was 3 ,7 1 7 ,8 8 4 p a r t i c l e s te n m icrons o r le s s in s i z e p er cu b ic fo o t. The amount o f d u st produced by th e ch arg in g o p e ra tio n v a rie s co n sid erab ly a t th e v ario u s p la n ts as is shown by th e s e a v e ra g e s; R efinery C harging Rate P a rtic le s per cubic foot B aton Rouge Bayway Bayonne E ag le Works 8 tons per hour 1-1/4 " 3-1/2 " " 0 II 11 11 4 ,2 7 1 ,4 1 3 2 ,4 3 5 ,5 2 0 2,242,944 1,042,976 I t is th e g en era l b e lie f th a t th e more tim es a c la y has been used and reco n d itio n e d , th e le s s d u st is produced d u rin g i t s handling. Our stu d y does not confirm th is be l i e f as a p p lic a b le to d u s t produced w hile charging f i l t e r s . Averages of d u st counts in sam ples taken d u rin g t h i s o p e ra tio n were; $ 1 Clay. . . . . . . . . . . . . . . . . . 2,242,944 p a r ti c le s per cubic fo o t # 3 " . . . . . . ____. . . ------- - 4 ,6 0 4 ,8 3 2 " " " " # 10 " ....................................... .. 3 ,8 9 6 ,8 3 2 " " " " 20- A ccording to an a n a ly s is o f p a r tic le s i z e made by th e Bayonne L a b o ra to ry o f a sam ple o f Raw (3 0 -6 0 g ra d e A tta p u lg u s C la y ) N o ,1 , No*3, an d No, 8 Wedge c l a y s , t h e follow ing is th e siz e c la s s ific a tio n or d is trib u tio n : j ) Raw C lay #1 C lay #3 Clay #8 Clay C oarser than 100 mesh 98 . 5$. . ........... .. 99 . 4 $ ___ * * . 98 7%a * . . 9 8 ,3 $ Diam eter o f P a r tic le s Raw C la y #3 Clay #8 Clay M illim eters M icrons Per Cent P er Cent Per Cent _ .1 4 9 .0 7 4 .0 4 4 .035 .025 .015 .0 0 5 to ,074 " .044 " -,0 3 5 " .025 " .015 " ,005 " ,001 149 to 74 74 It 44 44 II 35 35 1! 25 25 1! 15 15 It 5 5 U 1 0.14355 0.55095 0.29760 0.21555 0.17550 0 11640 0. 00045 1. 00750 0.17186 0.05369 0.03887 0.01729 0. 01027 0. 00052 0, 54159 0,08449 0. 04585 0.01603 0.00847 0. 00336 0. 00021 About 85$ o f th e d u st p a rtic le s in sam ples taken d u rin g the charging of #3 c la y were s lig h t ly a n g u la r in appearance and f iv e m icrons o r le s s in s i z e j 15$ were rounded sem i-opaque, te n m icrons or over in s iz e . About 75$ o f th e p a rtic le s in sa m p le s ta k e n d u r in g t h e c h a r g in g o f =-10 c l a y w ere s l i g h t l y a n g u la r c r y s t a l l i n e , f i v e m icrons or le s s in s i z e j a b o u t 20$ were over t e n m icrons in s i z e and w ere sem i-opaque abo u t 5$ were round sem i-opaque between fiv e and te n m icrons in siz e . A ll of th e la r g e r p a r t i c l e s ap p ear to c o n ta in sm all b u b b le s. T here a re numerous sm a ll b la c k specks about o n e-q u arter m icron in size. C harging o f f i l t e r s i s u s u a lly done by one man p e r s h i f t f o r each f i l t e r house. There a r e th r e e s h i f t s a day, These men have an av erag e s e r v ic e o f ab o u t 20 y e a rs and work e ig h t hours a s h i f t , nine s h i f t s out o f fo u rte e n , V e n tila tio n is pro v id ed in th e newer f i l t e r houses by e i^ ite e n -in c h ro o f ven t i l a t o r s e x te n d in g a b o u t tw e lv e in ch es above t h e ro o f and a l s o by windows which oc cupy about 80$ of the w all space in fro n t of th e top of th e f il te r s , DUMPING FILTERS - A f t e r t h e f i l t e r s a r e c h a rg e d w i t h c l a y th e y a r e p l a t e d up \ and th e o il is allow ed to p e rc o la te through th e clay fo r s e v e ra l hours, th e le n g th o f tim e depending upon th e n a tu re o f th e o i l ru n and th e " y ie ld " o f th e c la y . The o i l i s a l l d rain ed o ff and th e clay is then washed w ith n ap h th a or "V arsol" and steam ed t o remove a l l t r a c e o f th e n a p h th a . A fte r t h i s t h e f i l t e r i s dumped on t o a can v as 1 b e lt conveyor and th e clay retu rn ed to the k iln fo r bu rn in g or reco n d itio n in g . F ilte r c la y is used as many a s fo u rte e n tim es b e fo re i t i s f i n a l l y d isc a rd e d . In o rd e r to I determ ine what e f f e c t th e re c o n d itio n in g o f f i l t e r clay had on i t s fre e s ili c a con t e n t sam p les w ere a n a ly z e d by t h e New York S t a t e D ep artm en t o f L ab o r, D iv is io n o f I n 1 d u s tr ia l Hygiene w ith th i s r e s u lt : I Times B urned $ Free S ilic a I Raw C l a y . . . . . . . . . . . . . . . . 6. 30 \ O nce............................. 8 .5 0 1 { . J T h re e .................. .. 9, 20 E i g h t . . . ....................... .. 9, 30 I C onsiderable steam i s u s u a l l y given o f f during t h e dumping which probably 1 explains th e sm aller d u s t count (a general average o f only 2,518,781 p a rtic le s te n miororis o r le s s in s iz e p e r oubic f o o t) th a n w ould b e expected. The d u s tie s t p a r t o f th e f i l t e r dumping o p e r a tio n i s sw eep in g up th e f lo o r under th e f i l t e r s a f t e r dump in g is com pleted. Sam ples tak en d u rin g th is sweeping or clean in g up had as h ig h as 16,638,880 p a r tic le s p e r oubic f o o t, although th e g e n e ra l average o f sam ples ta k e n d u rin g dumping a t th e v a rio u s r e f i n e r i e s was 2 ,5 1 4 ,8 1 6 p a r t i c l e s p e r cxibic fo o t. About 95$ of th e se dust p a rtic le s are s lig h tly angular c ry s ta llin e in appearance under th e K onim eter m iorosoope and a re above fiv e m iorons o r le s s in s i z e j about 5$ a re rounded sem i-opaque over fiv e m icro n s in s iz e . O c c a sio n a lly th e c la y d o esn 't "flow" when th e f i l t e r is opened and m ust be s ta r te d "flow ing" by means of an iro n b a r. This a c tio n cau ses some d u s t (2 ,8 8 8 ,6 4 0 p a r t i c l e s p er c u b ic f o o t) b u t n o t as much a s pounding th e bottom and low er s id e s w ith a s le d g e (4 ,2 4 8 ,0 0 0 p a r t i c l e s p e r cubic f o o t) as i s some tim es done. A fter th e clay has run o u t, th e in s id e o f ;th e f i l t e r is swept out w ith a broom w hich produces a l i t t l e d u s t (an av erag e o f 792,960 p a r tic le s p er cubic f o o t) . The f i l t e r is th en p la te d up and is ready f o r rech a rg in g . The work o f dumping f i l t e r s is done by one man per s h i f t , f o r each f i l t e r house. T hese men have an a v e ra g e s e r v ic e o f a b o u t t e n y e a rs and work e ig h t h o u rs a s h i f t , n in e s h i f t s out o f fo u rte e n . Thqy a re exposed to d u st le s s th a n 60 p er cen t, o f th e ir w orking tim e. Spent clay is used to a lim ite d ex ten t fo r packing around v alv es and f ir e hy d ra n ts to p rev en t fre e z in g ] also fo r c e rta in o th er sm all absorbing job such as on th e w arehouse flo o rs o f some of th e la r g e r bulk s a le s p la n ts where lu b r ic a tin g o ils a re tr a n s f e r r e d from b a r r e l s o r drums to s m a lle r c o n ta in e r s , or lo ad ed in to f iv e g a llo n oans from b u lk . Most o f th e sp e n t c la y is d is p o s e d o f, how ever, by dumping i t on n earb y Company p ro p e rty and, to a l e s s e r e x te n t on r a i l r o a d p ro p e rty n e a r r i v e r b an k s. C om position o f F i l t e r House A ir Borne D ust; Samples o f d u s t from A tta p u lg u s C lay, w hich had s e t t l e d on th e to p s o f e le v a to r h o u sin g s and on g ir d e r s o v er th e s to r a g e b in s In f i l t e r h o u se s, w ere su b m itte d t o th e U nited S ta te s B ureau o f M ines Ex perim ent S ta tio n fo r p etro g rap h ic exam ination. O rd in arily p o s itiv e re s u lts a re not obtained in p etrographic te s ts for th e id e n tific a tio n of m inerals in atm ospheric dust. However, th e sam ples su b m itted were co arse enough to give r e s u lts in m ost c a se s. In stu d y in g th e r e s u lts o f th e p e tro g ra p h ic exam inations i t should be borne in mind th a t th e samples subm itted were s e ttle d dust, and th a t th e y are n o t re p re s e n ta tiv e of th e c o m p o sitio n o f th e d u st t h a t would be b re a th e d g e n e r a lly owing t o th e d i f f e r e n t i a l s e t t l i n g ra te s and th e ease w ith w hich th e v ario u s m in eral c o n s titu e n ts can be crush ed to a powder. " M o n tm o r illo n ite " ((M g, Ca) 0. A l2 O3 , 5 S i 02 nH20 -- n = 5 t o 8 ) i s t h e m in e r a l t h a t i s c h a r a c t e r i s t i c of many ty p e s o f f u l l e r s e a r th . Hot a l l o f th e l e s s im p o rta n t m in erals found were f u lly id e n tifie d . Clay d u st from to p s h e ll of e le v a to r - Top # 2 , H erm an-Frasch Purnaoe3 Q uartz - 10$ M ontm orillonite - 80$ C a lc ite , M icro clin e and U n id e n tifie d - 10$ D ust from accu m u latio n on g ir d e r over c la y s to ra g e b in s - #4 F i l t e r House. Q uartz - 10$ M ontm orillonite - 70$ P o ssib ly o th e r c la y m in erals p re s e n t, opaque - 20$ D ust from ac c u m u la tio n on g ir d e r over c la y s to ra g e b in s - #1 F i l t e r House, Q uartz ~ Over 1$ Opaque - 40$ M ontm orillonite - 55$ U n id en tified - 5$ C o n tro l of F i l t e r Clay Dust? Dust in a f i l t e r p la n ts r e s u lts p r in c ip a lly from th e o p e ra tio n o f th e c la y h a n d lin g m a ch in ery . The c o n d itio n is a g g ra v a te d by th e p r e s e n t p r a c t i c e a t some r e f i n e r i e s by u s in g an a i r h o se t o blow accu m u lated d u s t and s p ille d clay from equipm ent, w a lls and flo o r s . H andling a fin e lig h t d u st producing m a te ria l, such as f i l t e r c la y , in a system w hich in clu d es open b e lt conveyors is in h e re n tly a du sty o p eratio n , (12,687,360 p a r tic le s , te n m icrons or le s s in s iz e , per c u b ic f o o t) . I t is d i f f i c u l t t o p re v e n t some d u st frcsn b e in g g e n e ra te d a t u n lo a d in g p o in ts where th e clay f a l l s in to chutes or b in s , b u t i t can and should be c o n tro lle d by means o f hoods, e n c lo su re s, and adequate ex h au st system s w ith e f f e c tiv e d u st c o lle c to rs. - T here w i l l alw ays be an i r r e d u c i b l e minimum o f s p i l l a g e and d u s t s e ttle m e n t w herever dusty m a te ria l is handled in system s such as e x is t in most re fin e ry f i l t e r h o u ses. This i s an economic w aste and in o r e a s e s th e d i f f i c u l t y o f th e d u s t c o n tro l p ro b lem . U n le s s t h e p r e s e n t p r a c t i c e o f c l e a n i n g d u s t s p i l l a g e b y b lo w in g w ith com p r e s s e d a i r i s changed, th e n e c e s s a r y p e r i o d i c c le a n in g wi-11 c o n tin u e t o be a v e r y d u sty and u n h ealth fu l o p eratio n even though a l l p recau tio n s have been taken to pre v e n t th e escape o f d u st from c la y h an d lin g equipm ent. A modern in d u s tr ia l vacuum c le a n in g system would do th e jo b e f f i c i e n t l y , w ith o u t c r e a tin g any d u s t. The p r in c ip a l so u rce o f d u s t in f i l t e r b u ild in g s is th e b e l t conveyor which is u s u a lly lo c a te d a t th e to p o f th e b u ild in g . G usts o f wind from th e m o n ito r blow th e c la y and d u st from th e b e l t. A c e r ta in am ount of d u st is a ls o g e n e ra te d by c la y f a l l in g in to th e tr ip p e r ch u te (6 ,0 6 0 ,4 8 0 p a r ti c le s per cubic fo o t) and d isc h a rg in g from th e trip p e r chute in to th e ch u te lead in g to th e various f i l t e r s (7,306,560 p a rtic le s p er cubic fo o t). This could be c o n sid e ra b ly reduced by in s e rtin g canvas o r sh e e t iro n co n n ectio n s betw een th e ends o f th e tr ip p e r chutes and th e chutes to th e f i l t e r s , and by usin g a p ro p erly designed b e lt tr ip p e r on th e conveyer b e lt. Bins f o r th e sto ra g e o f f i l t e r c la y sh o u ld be C losed w ith s te e l decks having th e sm a lle st p o ssib le openings in the form o f chutes to rece iv e clay from th e convey e rs. I f care were taken n o t to overflow th e b in s, th e d u st and s p illa g e could be g re a tly reduced. For com plete c o n tro l o f d u st, an ex h au st system equipped w ith d u st c o lle c to r, fa n , d u cts and hoods should be in s ta lle d to remove d u s t from th e p o in ts o f o rig in , such a s, a l l unloading p o in ts (ex cep t m ovable tr ip p e r s ) of each b e lt conveyer in th e b u i l d i n g , new c l a y b in s and b u rn e d c la y b i n s . One e s ti m a t e w hich h a s b e e n p re p a re d fo r such an in s ta lla tio n c a lls fo r an exhaust system w ith a cap a city o f approxim ately 1 5,000 cu b ic f e e t of d u s t la d e n a i r p er m in u te , and is b a se d on m a in ta in in g an inw ard flo w o f a i r a t openings i n t o hoods and b in s a t a recommended v e l o c i t y o f 200 f e e t o r more p er m in u te. In c o n s id e rin g d u s t c o l le c t o r s , i t sh o u ld be borne in mind th a t th e cy clo n e ty p e w ill n o t remove th e fin e d u st p a r ti c le s (te n m iorons o r le s s in s i z e ) w hich a re most in ju rio u s to h e a lth , and th a t th e c lo th bag ty p e f i l t e r has been proven to be more su c c e ssfu l in rem oving th e s e fin e p a r tic le s . Under e x is tin g c o n d itio n s a t most p la n ts i t is alm ost im p o ssib le to keep th e p l a n t s c le a n , r e g a r d l e s s o f how c a r e f u l l y t h e equipm ent i s o p e ra te d . However, t h e i n s t a l l a t i o n of a vacuum system and adequate d u s t c o lle c to r s should encourage o p e ra to rs t o e x e r c is e more c a re in th e o p e ra tio n o f equipm ent and th u s cu t down th e amount o f d u st and s p illa g e . B - CONTACT CLAYt Most c o n ta c t c la y s , p a r ti c u la r ly in th e U nited S ta te s , a re acid tr e a te d "Ben to n i te " , B e n to n ite is a n o n - r e f r a c to r y c la y , a double s i l i c a t e o f iro n and aluminum, d e riv e d from th e sh ale of th e F o rt Benton fo rm atio n in th e upper M issouri v a lle y . -2 3 - T here appears to be a w ide v a ria tio n in th e com position and fre e s i l i c a con t e n t o f American and E uropean c o n ta c t or a c tiv a te d c la y s. " F ilt r o l " an e x te n siv e ly .used Am erican c o n ta c t c la y i s re p o rte d to c o n ta in about 57$ fr e e .s i lic a ( s i l i c a which ' is in so lu b le in concentrated hydrochloric a c id ), "M ilw hite", another extensively used A m erican c o n ta c t c la y , c o n ta in s 65$ fre e s i l i c a . The c o n ta c t c la y s l i s t e d a re th o se m ost ex ten siv ely used in Europe % Insoluble in C o n c e n tra te d HCL In so lu b le in C oncentrated HCL an d 5 % NAp. CO5 . " Iv ry " Clay ( F r e n c h ) . . . . . . , . "T errana Extra" (G erm an),... " C l a r i t " ( I t a l i a n ) . , ___ . . . . 7 5 .0 $ ............................. 6 4 .4 $ ............................. 4 9 .5 $ .............................. 6 4 .6 $ 2 7 ,2 $ 5 0 .6 $ " T o n s il AC", a n o th e r F rench c o n ta c t c la y , has 6 1 .7 5 $ f r e e s i l i c a . The main c o n s ti tu e n t s o f " P e t r i s i l " , a German c o n ta c t c la y , are* T o t a l S i l i c a . ...............,k........... .... Lime (C a O )...................................... Aluminum and Iro n O x id e s.. . , Loss on ig n itio n (W a te r).... 51, 57$ 0 .6 3 $ 18, 83$ 2 3 .6 2 $ The b a la n c e p ro b ab ly c o n s is ts o f p o tassiu m and sodium oxides. The fo llo w in g i s th e r e s u l t o f a p e tro g ra p h ic ex am in atio n o f " P e t r i s i l " w hich was made a t th e U n ite d S ta te s B ureau of M ines experim ent s ta tio n s Q u a r t z . . . , , 4, 5$ M o n tm o r i llo n i te ............ 90$ U n id en tified M inerals, . .. .. .. 5$ The use o f c o n ta c t clay fo r im proving th e c o lo r of lu b ric a tin g o ils is a r e cen t developm ent. A t p re se n t th e p r ic e o f c o n ta c t c la y is so low th a t i t is used only once and then discarded. A lth o u g h th e r e a r e many c o n ta c t c la y s on th e m ark et, a la r g e p e rc e n ta g e o f t h a t u sed by th e S tan d ard g ro u p i s known a s " F i l t r o l " , c o n s e q u e n tly t h i s was in c lu d e d in our dust studies. What i s " F i l t r o l " an d How i s i t P ro d u ced ? " F i l t r o l " i s a p u lv e r i z e d a c i d t r e a t ed B e n to n ite , used as a d e c o lo riz e r, ab so rb en t and d eo d o riz er in th e re fin in g and p r e p a r a tio n o f b o th o rg a n ic and in o rg a n ic o ils . I t comes from "open c u t" m ines in M is s is s ip p i and C a lif o r n ia , and occurs in beds a b o u t two and o n e -h a lf f e e t th ic k u n d er a n o v e r-b u rd e n o f some e ig h te e n to tw e n ty -fiv e f e e t . T here h as b een some doubt as to i t s o r ig in , b u t i t i s now b e lie v e d to have b een v o lc a n ic d u s t tr a n s p o r te d by t h e a i r and d e p o s ite d u n d e r t h e w a te r s o f e i t h e r a l a k e o r a s e a . Raw B e n to n ite i s mined and loaded onto tru c k s w ith steam sh o v els, and th e n tak en to th e px-eparation p la n t. A t r a c t o r scoop l i f t s th e raw m a te ria l from th e s to ra g e shed flo o r and p la c e s , i t in a hopper o u t o f which i t i s fed in to an e le v a to r by means o f a s te e l pan feed e r , The e l e v a to r d is c h a r g e s i n t o a c r u s h e r w hich b re a k s th e m a t e r i a l down s u f f i c i e n t ly to enable i t to pass through a screen (th re e meshes to an in ch ) onto a b e lt con v ey er w hich ta k e s i t to a p re-m ix er where i t is mixed w ith w ater to form a " s lu rry " . This s lu r r y is passed in to la rg e wooden tan k s and t r e a t e d w ith d i l u t e su lp h u ric a c id -2 4 - a g ita te d w ith a i r and steam* I t is th e n dumped in to th ic k e n e r s , w ashed, and d e l iv e r ed to an O liv e r f i l t e r From th e r e i t goes in tu r n to a pug m i ll, d ry in g to w er, cag e and imp m i l l , and c l a s s i f i e r . The f i n i s h e d p r o d u c t i s p la c e d i n a b i n w here i t i s p u t in to f i f t y pound B a te s V alve p ap er bags b y means o f a B ates Bag P ack er. I t i s shipped in r a ilr o a d box c a rs , each having a c a p a c ity o f from 1600 to 2000 bags. The th r e e grades o f " F i l t r o l " in g r e a te s t demand ares GRADE (Per cent, th ru 200 m esh ) Per cent, of T otal P ro d u c tio n C o arser Than 200 Mesh 200 - 325 Mesh F in e r Than 325 Mesh 86 - 88 76 - 88 90 - 93 I 80 1 4 .0 $ . 16.0# 70, 0% 16 23 0% 24,09S 53.09t I 6 8, 0% 2 3 ,0% 69.09? I The o n ly r e a l d u s t p ro d u cin g o p e ra tio n s in th e p ro d u c tio n o f F i l t r o l a re th e ! f i l l i n g , s ta c k in g and h a n d lin g o f th e f i f t y pound b a g s. Samples o f d u s t ta k e n d u rin g th e se operations, rev ealed th e follow ingt" 1 Op e r a t i o n P a rtic le s per cu ft. i Average d u st f i l l i n g bags w ith 85-88 grade 10,416,096 1 " " p ack in g room w hile f i l l i n g bags 9 ,5 7 2 ,1 8 0 " " produoed in handling of f ille d bags 5 ,8 4 5 ,2 4 8 I An e x h a u s t s y s te m h a s b e e n i n s t a l l e d t o re d u c e an d c o n t r o l t h e d u s t p ro d u c e d I d u rin g th e packing of F iltr o l, This c o n sists of a m etal hood above th e f il lin g tu b es in fro n t of th e m achine, w ith a b a sin below. A sev en -in ch d u ct le a d s from th e b a s in 1 and a s ix -in c h duot to a canopy in back of th e packer, b o th connecting w ith a te n - in c h m ain d u c t w hioh r u n s t o a S tu r te v a n t F an (1750 R. P.M. ) d e s ig n e d t o h a n d le 1 ,6 2 0 1 cubic f e e t o f a i r per m inute a g a in s t fo u r-in c h w ater s t a t i c p ressu re. A cyclone d u st c o lle c to r removes th e la r g e r p a r tic le s from th e a ir b e fo re d e liv e rin g i t to a tu b u la r 1 clo th dust co llecto r. 1 About s ix ty per c en t, o f th e dust p a r tic le s o f sam ples taken during th e f i l li n g o p e ra tio n a r e s l i g h t l y an g u la r c r y s ta l lin e in ap p earan ce under th e K onim eter m i I cro sco p e, and a r e about two m icrons or le s s in siz e s ap p ro x im ate ly tw enty per c e n t, a p p e a r to be rounded c r y s t a l l i n e , g l a s s - l i k e , b u t w ith r a th e r smooth edges, and over 1 te n m iorons in s iz e . There a re a la rg e number of v ery sm all gray p a rtio le s (about tw e n ty per c e n t. ) to o m in u te and too numerous to count a c c u ra te ly . .1 What i s th e C hem ical C om position o f " F i l t r o l " ? Below is th e r e s u l t o f an an 1 a ly s is by a com mercial chem ical la b o ra to ry in Los A ngeles, C a lifo rn ia , o f a sam ple of F iltr o l from th e Jackson (M ississip p i) p la n tt I P er Cent, 1 S ilic a (S i02) . . . . . . . . . . . 56, 90 * Alumina (A 1 2 0 3 ).. . . . . . . . 99 4 0 9 e 0 15. 97 F e rric Oxide (F egO g).. . . 1. 44 T itanium Oxide (T i0 2 ) .. 0. 10 Calcium Oxide (C aO )... . , OOO9O0O00 2 82 d Magnesium O xide (M gO)... 3 55 M anganese D io x id e (MnOg) .t Carbon D ioxide ( C 0 g ) .... Potassium Oxide (K gO )... 0. 03 .t r -2 5 - t^ j I P er Cent Sodium O xide (N a2 0 )................................................ Chlorine (C l).................................................... P h o s p h o ric A n h y d rid e (P 2O5 ) ............................. S u lp h u r ic A n h y d rid e (SO3 ) . ............................... T o ta l i g n i t i o n l o s s ................... F re e M o is tu r e .............................................................. 0 ,0 4 0 63 20. 00 12 23 " I t is custom ary to s e p a ra te ly re p o rt m a te ria ls such as S ilic a (S i02) an d A lum ina ( A I 2O3 ) in u l t i m a t e a n a l y s i s a lth o u g h t h e e le m e n ts a r e known t o be in com bination wi+h one a n o th e r. I t i s d i f f i c u l t to g e t an a n a ly sis o f free S ilic a and sin ce th e q u an tity contained in F ilt r o l would be v e ry s m a ll, we have n o t a tte m p te d t o have t h i s p a r t i c u l a r a n a ly s is made," The fo llo w in g i s th e r e s u l t o f an a n s ly s i. o f "S u p e r - F i l t r o l " w hich was made in Frances Per Cent, M o is tu r e a t 120 d e g r e e s C ............................... Loss on i g n i t i o n . ..................................................... I n s o l u b l e i n c o n c e n tr a te d H C L ...................... (T o tal S ilic a and u n attack ed c r y s ta ls ) I n s o l u b l e i n HCL and i n a 5% Na2 C03 s o l u t i o n . (S ile y , q u artz and unattacked c r y s ta ls ) 16, 5 33.5 5 5 .0 15, 0 A m icro sco p ic exam ination shows a few p a r ti c le s w ith "acute angles". An e x a m in a tio n made by t h e U n ite d S t a t e s B u re a u o f M ines E x p e rim e n t S t a t i o n i n P itts b u r g h , P e n n sy lv a n ia showed t h a t F i l t r o l c o n ta in s m ore th a n 1% q u a r tz , 95% M o n tm o r i llo n i te ((M g, Ca) 0 . A l203~5S i 02-riH20---n=5 t o 8 ) and 5% u n i d e n t i f i e d m i n e r a ls , A s i m i l a r e x a m in a tio n of A tta p u lg u s F in es (200 m esh) showed 5% q u a r tz and 95% Mont m orillonite How i s C o n ta c t C lay Used? The c l a y i s m ix ed w ith o i l , a g i t a t e d and h e a t e d , and e i t h e r allo w ed to s e t t l e o r ru n th ro u g h a f i l t e r p re s s . I t is th e n d isc a rd e d . The c la y is e i th e r dumped d ir e c tly in t o th e o i l o r p la c e d in a hopper from which i t flow s in to in d u c to rs o r m ix in g cham bers where i t i s m ixed w ith th e o i l and th e n pumped to a f i l t e r ta n k . The o n ly d u sty o p e ra tio n s a re th e u n lo a d in g o f th e m a te ria l and dumping i t in to th e hoppers o r m ixing cham bers. The h ig h e r d u st counts w ith th e c o n ta c t c la y as compared to f i l t e r cla y is probably due to th e f a c t th a t i t is a fin e r m a te ria l, o r a t l e a s t d is in te g r a te s more e a s ily th a n th e f i l t e r c la y s stu d ie d , Sam ples ta k e n d u rin g th e dumping o f F i l t r o l and A tta p u lg u s F ines in to a re a c tio n chamber gave th e follow ing d u s t counts. Op e r a t i o n P articles per cu, f t. A verage d u st produced w h ile dumping 50 pound bags of "F iltro l". 6 ,7 6 8 ,4 8 0 A verage dust produced w h ile dumping 100 pound bags of "A ttapulgus F i n e s " , . . . . . . . . . . . . . . . , 9 ,2 6 0 ,6 4 0 -2 6 - Under th e K onim eter M icroscope th e p a r t i c l e s were rounded in ap p earan ce. The " A tta - pulgus F ines" ap p eared more c r y s ta l lin e and a n g u lar, and had a g r e a te r p ro p o rtio n of p a r tic le s fiv e m icrons or le s s in s iz e th a n d id th e " F iltr o l" , The counts in d ic a te 4i t h a t m ore d u s t r e s u l t s from dum ping A tta p u lg u s F in es t h a n fro m dum ping F i l t r o l a c t i vated clay. Dumping f i f t y pound b ag s o f "M ilw h ite " (90% th ro u g h 200 m e sh ), a T exas c o n ta c t c la y , in to th e feed hoppers to th e in d u c to rs o r m ixing chambers is an exceed in g ly d u sty o p e ra tio n , Samples ta k e n d u rin g t h i s o p e ra tio n had as high as 14,046,720 p a r t i c l e s te n m icro n s or le s s i n s iz e p e r cu b ic fo o t, Samples ta k en in th e m iddle of th e room ju s t a f t e r t h i r t y bags had been dumped in to th e hopper had 5 5 ,8 4 7 ,0 4 0 p a r t i c l e s p e r c u b ic f o o t. U nder t h e K o n im e te r M ic ro s c o p e , a b o u t 90/2 o f t h e s e p a r t i c l e s a p p e a re d s l i g h t l y c r y s t a l l i n e , and w ere f i v e m ic ro n s o r l e s s in s i z e ; 10 ;o w ere ro u n d , sem i-opaque, te n to tw enty m icrons in s iz e . There were a ls o a few s c a le li k e p a r tic le s. F o u rteen men w ith an a v e ra g e s e r v ic e c r e d i t o f s i x y e a rs a re in v o lv e d in t h i s o p e r a tio n . T h ree men a r e exposed to th e d u s t d u rin g s i x h o u rs o f eac h e ig h t h o u r s h if t fo r nine o f th e fo u rte e n s h if ts d u rin g th e 85^ of th e tim e th e f il te r in g p la n t i s i n o p e r a t io n . They w ear H. S. A. "Comfoil r e s p i r a t o r s . A fte r e x te n siv e stu d y and in v e s tig a tio n th e lo c a l management has made a rra n g e m ents to re c e iv e th e clay in tank cars s im ila r to th o se m anufactured by th e G eneral A m erican Tank C ar Company, T h ese c a rs a r e s e lf - u n lo a d in g and w i l l d is c h a r g e in t o an e n c lo se d hopper. The c la y w i l l then be tr a n s p o r te d to s to r a g e b in s by means o f a screw conveyor com pletely en clo sed in te n -in c h tu b in g . I t w ill be w ithdraw n from th e bottom of th e b in s , passing through w eighing s c a le s, in to th e in d u c to rs where i t w ill be m ixed w ith th e o il. This w ill provide a com pletely clo sed system ana should elim in ate a ll a ir contam ination, C - BONE BLACK OK CHAFJRLD BODE* R efined wax is f i l t e r e d th ro u g h bone b la c k or c h a rre d bone to im prove i t s c o lo r. T h is m a te r ia l i s o b ta in e d from v a rio u s m eat packing firm s in f in e ly woven c o f fe e bags t h a t h o ld ab o u t 150 pounds each An open b e l t con v ey er and e le v a to r c a r r y th e bone d ir e c tly from th e r e a c tiv a tin g fu rn a c e to th e covered f i l t e r charg in g hopper. M etal ch u tes le a d d ir e c tly from th is hopper in to f i l t e r s w hich hold ab o u t 3,000 potm ds o f bone b la c k . Upon c o m p le tio n o f f i l t r a t i o n th e bone is w ashed w ith " V a rso l" , steam ed f o r a b o u t 24 h o u rs , washed w ith h o t w a te r, steam ed fo r two h o u rs m ore, and th e n dumped upon b e l t c o n v ey e rs w hich c a r r y i t to th e r e a c tiv a t in g fu r n a c e which i s gas f ir e d . The bone goes through th e fu rn ace a t a tem p eratu re o f ab o u t 1100 degrees F a h re n h e it and a t th e r a t e o f about 250 pounds p er hour. Bone b la c k c an he used over and over ag ain . Three men one on each s h i f t , w ith an av erag e se rv ic e c r e d it of f if te e n y ears, a re engaged in th is o p eratio n . Their period o f exposure to dust is about one hour p e r s h if t. The g r e a te s t amount o f d u st produced r e s u lt s from th e open co n v ey ers, p a r tic u la r ly in dumping th e m a te r ia l from th e fu rn a c e onto th e conveyer b e lt. Samples ta k e n d u rin g th is o p eratio n had as high as 11,044,800 p a r tic le s o f te n m icrons or le s s in siz e p er cubic fo o t. C onsiderable d u st (14,273,280 p a r tic le s p er cubio fo o t) a lso a r is e s from th e open h atch o f th e f i l t e r charging hopper d u rin g f i l l i n g . An e i g h t - i n c h m o to r d r i v e n e x h a u s t f a n h a s b e e n i n s t a l l e d t o su c k b a c k t h e d u s t from w h ere t h e e l e v a t o r b u c k e ts dump th e r e a c t i v a t e d bone i n t o th e c h u te t o t h e c h a rg in g hopper. The d u s t lo s s from t h i s f i l t e r i n g o p e ra tio n is e s tim a te d to be a b o u t 1500 pounds p er month, ' Under th e K onim eter M icroscope ab o u t of th e d u st p a r tic le s of sam ples tak en '^`d u r in g th e r e a c t i v a t i o n o f b o n e b la c k a p p e a r t o be b la c k , o p aq u e, s c o t - l i k e , an d a r e fiv e m icrons o r le s s in s iz e ; 5% a re rounded, sem i-opaque, te n m ic ro n s,o r more in s iz e . The a n g u la r c r y s t a l l i n e and l i g h t grey p a r t i c l e s which c o n s titu te ab o u t 30% a re pro b ab ly bone ash III INSULATING OPERATIONS In su la tio n plays an im p o rtan t p a rt in th e p ro o essin g of petroleum products* The two types o f in s u la tin g m a te r ia l m ost fre q u e n tly used a re "Sponge F e lt" (a s b e s to s w ith ground sponge to g iv e dead a i r space and th u s in c re a se th e e ffe c tiv e n e s s o f th e in s u la tio n ) and a m ix tu r e o f 85$ m agnesia and 1 5 % a s b e s to s . Rock wool i s used to a c o n s id e ra b ly l e s s e r d eg re e . In th e o rd in a ry com m ercial form , Rock Wool, as used' a t our r e fin e rie s , does not p resen t a d ust hazard. I t i s a lso used fo r house In s u la tio n , and is a v a ila b le in sm all nodule form which can be blown in to p lao e. "85$ magnesia" is a m ix tu re o f m agnesia and g ran u la ted a sb e sto s and p ressed in to blocks of v a rio u s s iz e s and shapes (u su a lly 16" x 18" x l - l / 2 " ) . The m ost d u st oomes from d ism a n tlin g o ld in s u l a t i o n and g rin d in g s c ra p m a te r ia l f o r use as a p la s t e r o r " g a n is te r" . The a v e ra g e s e r v ic e o f men engaged in in s u la tin g o p e ra tio n s i s a b o u t f i f t e e n y e a r s . M ost o f t h e s e men h av e b e e n t r a n s f e r r e d fro m th e Common L abor D epartm ent, They work n in e o u t o f f o u rte e n e ig h t-h o u r s h i f t s , i n gangs o f from two t o s ix men, and a re a c tu a lly exposed to d u s t fo r l e s s th a n s ix ty p e r cen t, o f t h e i r w o rk in g tim e . G oggles a r e so m etim es p ro v id e d , an d o c c a s i o n a l l y MSA "Comfo" R e s p ir a t o r s , b u t t h i s equipm ent i s n o t u s e d a s muoh as i t s h o u ld b e . G e n e ra lly s p e a k in g , a b o u t 86$ o f t h e i r w ork i s w ith sp o n g e f e l t and 1 5 $ w i t h 85$ m a g n e sia i n s u l a t i o n . At one o f the la r g e r so u th e rn r e f in e r ie s about 300,000 square fe e o f sponge f e l t and 5 0 ,0 0 0 sq u are f e e t o f 86$ m a g n e sia a r e h an d led a y e a r . A - What P h y s io lo g ic a l R eactio n s a re Provoked by I n s u la tin g M a te ria ls? A ccording t o Dr, L eroy U, G a rd n e r ( J o u r a . I n d u s t , Hyg, Mar, 1 9 3 7 ,V o l. 1 9 , No. 3 , P 1 2 l) a s b e s to s d u s t w ith i t s fib ro u s p a r tic le s does n o t seem to be r e a d ily handled by th e p ro te c tiv e mechanism of th e lu n g s. Q uoting from h is a r tic le ? "They a re n o t removed to th e lym phoid t i s s u e b u t rem ain in c o n ta c t w ith th e d e lic a te w a lls o f th e a i r sp aces. They become surrounded by an iro n -c o n ta in in g co atin g th a t fra c tu re s and g iv e s -ris e to th e pecu l i a r s tr u c tu re s known as * a s b e s to s is b o d ie s* , The f ib e r s a re i r r i ta tin g , perhaps because o f t h e i r form, and th e y e x c ite a f ib r o s is which begins ab o u t th e te rm in a l b ro n c h io le s and sp re a d s to form d i f fu se patches in th e parenchyma. O ften th e d is tr ib u tio n is su b -p le u ra l. In th e p re se n c e o f in f e c tio n , th e r e a c tio n to a s b e s to s d u s t i s muoh more sev ere th a n th a t caused by th e d u s t a lo n e ," There i s n o th in g in th e p e r tin e n t l i t e r a t u r e , nor does th e B ureau o f Mines know o f any evidenoe, w hich would d em o n strate m a g n e site (a n a tu r a l magnesium carbon a t e ) to be harm ful. I t w ould f a l l in th e c la s s o f "n u isan o e d u s ts " such as gypsum. W hile many of th e s o -c a lle d "n u isan o e d u sts" have n ev e r been found to be h arm fu l, i t is th e o p inion o f most in v e s t ig a t o r s in th e f i e l d o f i n d u s tr i a l hygiene t h a t no work e r sh o u ld be exposed t o any d u s t i n a c o n c e n tr a tio n ex o eed in g 75 o r 100 m illio n s o f p a rtio le s per cubio fo o t of a i r . B - What a r e t h e P r i n c i p a l I n s u l a t i n g Op e r a t i o n s and How Much D ust i s P roduced D u rin g S uch Op e r a t i o n s ? T h ere i s , o f c o u rs e , a w id e v a r i a t i o n in th e am ount o f in s u l a tio n work and th e am ount o f d u s t produced. A few exam ples, however, w ill give a good g en eral idea? INSULATING 12" STEAM LINES? 6" x 18" x l - l / 2 " b lo c k s o f 86$ mag n e sia a re tie d on th e steam lin e w ith 14-gauge g alv an ized w ire and covered w ith ro o fin g paper to make i t w aterp ro o f. O ften tim es t h i s work i s perform ed on s c a f f o ld s tw elv e to f i f t e e n f e e t above th e g ro u n d , w ith men ly in g on t h e i r b a c k s under th e l i n e p a r t o f th e tim e. -2 8 - C onsiderable d u st (as h igh as 18,124,800 p a r tic le s o f le s s th an te n m icrons p er cubic fo o t) re s u lts from tapping th e blocks in to place. Samples ta k e n d u rin g th e e n tire o p e ra tio n had an average co n cen tra tio n of 6,881,760 p a r tic le s per cubic fo o t. About 90$ of th e se dust p a r tic le s were s l i g h t l y an g u lar, c r y s ta llin e in appearanoe and above fiv e m icrons or le s s in size (as seen under th e Konim eter M ioroscope)j 5 $ w ere ro u n d ed o p a q u e , t e n m ic ro n s o r m ore i n s i z e ; and 6$ w ere opaque s c a le - lik e , f iv e m icrons o r more in s iz e . Samples tak en w h ile ap plying a sb e sto s sponge f e lt to a 12 " steam lin e had a d u st concen tr a tio n as high as 23,788,800 p a r tic le s o f te n m icrons o r le s s in s iz e per cubic fo o t. The average was 1 2 ,574,080 p a r tic le s p er cubic f o o t. T hese d u s t c o n c e n tra tio n s a r e c o n s id e re d to o h ig h f o r work ing w ithout adequate p ro tec tio n . INSULATING A 750-P0UND CRACKING COIL ACCUMULATORS 6" x 36" b lo c k s of Johns-M anville "F ire F elt" are f i r s t ap p lie d and p la ste re d w ith e x t r a AA R u b b e ro id A s b e s to s Cement an d w a te r p r o o f e d w ith J o h n s M anville " In su lk o te " . The d u s tin e s s o f h a n d lin g th e s e m a te ria ls has been considerably reduced since th e m anufacturers began shipping th e " F ire F e lt" in card b o ard carto n s c o n ta in in g th i r t e e n or tw enty b lo c k s, and th e p l a s t e r in hundred-pound paper bags. Samples taken durin g t h i s o p e ra tio n had an average d u st c o n c e n tra tio n o f 4,502,880 p a r tic le s , te n m icrons or less in s iz e per cubic fo o t. About 75$ of th e s e d u s t p a r tic le s w ere s lig h t ly an g u lar in ap p ea ran ce, fiv e m i crons or le s s in s iz e j 10$ were s c a le - lik e j opaquej and 15$ were ro d -lik e and fib ro u s. INSULATING TREATING PLANT ACID SUCTION LINE* S e c t io n s o f "Sponge F e lt P ipe Cover" a r e c u t to f i t p ip e le n g th s w ith an o rd in a ry carp en t e r ' s hand saw. T h is o p e ra tio n p ro d u ces on a n a v e ra g e 8 2 1 ,280 p a r t i c l e s o f d u st, te n m icrons or le s s in s iz e , p er cubic fo o t. Under th e K onim eter M icrosoope a l l o f th e se p a r tic le s a re s lig h tly a n g u lar, c r y s t a l l i n e in a p p e a ra n c e , and f iv e m icrons o r l e s s in s iz e . The blo ck s or se c tio n s o f th e pipe cover a re h eld in p la c e by w rapping #16 gauge galv an ized w ire about each one. INSULATING CRACKING COIL HOT OIL LINESt A l l h o t o i l l i n e s a t c r a c k in g c o ils a re in s u la te d w ith 2" a s b e s to s tu b in g (85$ m agnesia and 15$ asb esto s) held in p la c e by fine copper w ire. S ections of th e tubing a re cut to f i t p a r tic u la r areas by means o f an o rd in a ry c a rp e n te r's hand saw. T his p ro d u c e s 7 ,7 8 8 ,0 0 0 p a r t i o l e s o f d u s t, t e n m icro n s o r le s s in s iz e , per cu b ic fo o t. Under th e m icroscope, 90$ o f th e se d u st p a r tic le s appeared to be rounded c r y s ta llin e and about th re e m i crons or le s s in s iz e . Each se c tio n o f tu b in g is pounded in to place w ith the open hand so th a t i t f i t s snugly a g a in s t th e pipe, and th e n w ired in to p o s itio n . The d u st produced from b o th o f th e se o p e ra tio n s averages about 3,379,520 p a rtic le s per cubic fo o t. Under th e m icro scope, approxim ately 80$ or 90$ o f th e d u st p a r tic le s appear c r y s ta l li n e , more o r le s s a n g u la r, and fiv e m iorons o r le s s in s iz e j th e r e m aining 10$ or more a re rounded in ap p earan ce, and over te n m icrons in size. DISMANTLING OR REMOVING OLD INSULATION As a g e n e r a l r u l e , th e d ism a n tlin g o r rem oval o f old in s u la tio n is a more d u sty o p eratio n th a n th e a p p l i c a t i o n o f new in s u la tio n . The o ld i n s u l a t i o n i s chopped o r c u t w ith a h a tc h e t o r sm all h an d -ax e, and p rie d lo o se and p u lle d o ff w ith th e hands. This produces d u st c o n c e n tra tio n s as h ig h as 6,890,560 p a r tic le s , te n m icrons or le s s in s iz e , per cubic fo o t. In I ! I 8 I I I I I I B B B t I t t t I J: Jt J: Jfc Jfc J: Jt Jt Jt r -2 9 - \ J uy d ism an tlin g an old craoking c o il 4" t a r lin e , th e average d u st concen t r a t i o n was 2 ,3 2 2 ,2 4 0 p a r t i c l e s p e r c u b ic f o o t. In ap p ea ran ce th e s e p a r tio le s were c le a r c ry s ta llin e , r a th e r rounded, and fiv e m icrons or l e s s i n s i z e . No f i b r e s w ere o b s e rv e d i n any o f t h e d u s t sa m p le s from d ism a n tlin g o p e ra tio n s . A fte r a few weeks or months s e rv ic e , in s u la tio n on h o t lin e s d rie s out and appears to d is in te g ra te . This is prob ab ly due to th e fa c t th a t such in s u la tio n is u su a lly covered w ith a w e a th e r-p ro o f m a te ria l whioh p re v e n ts a b s o rp tio n o f m o istu re from th e a ir. l CRUSHING SCRAP ASBESTOS} S c ra p a s b e s t o s i n s u l a t i o n , u s u a l l y t h e 85$ m agnesia ty p e , is crushed in a b e lt- d r iv e n W illiam s cru sh er to pass - th ro u g h a so re e n w ith o n e-in ch h o le s o r s lo ts , and is th e n mixed w ith new a s b e s to s t o make i n s u la tin g p l a s t e r . T h is o p e ra tio n , w hich i s a v e ry d u sty one, is perform ed by two men, w ith an average s e rv io e c r e d i t o f a b o u t tw e lv e y e a r s . G oggles and MSA, "Comfo" o r W ills o n D u st R e s p i ra to rs are worn. C onsiderable d u st is produced in b reaking up th e s c r a p i n s u l a t i o n by hand p r i o r t o c r u s h i n g (1 0 ,1 9 5 ,'200 p a r t i c l e s , t e n m icrons o r l e s s , per cu b ic f o o t) , and a ls o when fe e d in g th e c ru sh e r whioh i s done b y s h o v e llin g th e b ro k en -u p p ie c e s in to th e hopper and poking them down w ith a s h o rt wooden s t i o k (14,839,680 p a r tio le s p er cubic fo o t). D ust counts as high as 27,527,040 p a rtic le s per cubic fo o t were found in sam ples tak en from over th e hopper. These d u st con c e n tra tio n s a re dangerously high. About 95% o f th e se p a rtic le s are sh a rp ly a n g u la r, c r y s ta llin e in ap p earan ce and f iv e m icrons o r le s s in s iz e j 5% a re opaque s c a le - lik e , s ix m icro n s o r more in s iz e . C rushing sorap asb esto s is not a steady ro u tin e o p eratio n , th e exposure varying from e ig h t h o u rs a month to about tw e lv e hours a week, CRUSHING OLD CORK INSULATION} T h is o p e r a t i o n i s p erfo rm e d a p p r o x i m ately tw ic e a y e a r and ta k e s about tw en ty or t h i r t y m inutes. The in s u l a t i o n is o ru sh e d on a b e l t - d r i v e n W illiam s c ru s h e r, by th e same men who o r u s h th e s c r a p a s b e s to s . T h is c r u s h e d c o rk i s u sed f o r i n s u l a t i n g lin e s in th e c o ld s e ttlin g p la n t. The av erag e amount of dust produced is 20,016,178 p a r tio le s , te n m icrons o r le s s in s iz e per cubic fo o t. About 80$ of th e p a rtio le s are s lig h tly an g u lar, c ry s ta llin e , in ap- p e a ra n o e , and f i v e m icrons o r l e s s in s i z e ] 20$ a r e ro u n d , sem i-o p aq u e, te n m iorons or more. There are a lso a la rg e number of very sm all b lack or dark grey specks, * IV - GUNITING OPERATION W hat i s G u n ite an d How i s i t App l i e d ? - G u n ite i s a m ix tu re o f a p p r o x im a te ly one p a r t (one 94 pound b ag ) of P o rtla n d Cement and two p a r ts (tw elv e scoop s h o v e ls ) of clean sh arp sand. The sand and cement a re m ixed d ry , shoveled in to th e hopper o f a G unite m achine, u sin g w ater under about 40-pounds p er square inch p ressu re and com pressed a i r a t t h i r t y to n in e ty pounds p er sq u are inch. I t is ap p lied under p re s su re, as a se m i-flu id , a g a in st th e su rfa c e to be p ro te c te d (visually process equipm ent, suoh a s , c ra c k in g o o il soaking drums and s to r a g e ta n k s ) . In p r a c tic a lly every c a s e where g u n itin g is done, i t follow s im m ediately, a f te r th e sand b la s tin g job used to c le a n th e s u ra c e . I n m ost c a s e s , th e work i s p e rfo rm e d by th e same crew , The i n d i v id u a l h o ld in g th e g u n ite n o zzle is provided w ith th e same p ro te c tio n as is th e ,,. o p e ra o f th e sand b l a s t n o zzle, and th e men te n d in g th e g u n ite m achines a re p ro v id e d w ith r e s p ir a to r s and a re re q u ire d to u se them w h ile a c tu a lly h a n d lin g th e sand " ,x' | and cem en t. T h is i n v o l v e s m ix in g t h e m a t e r i a l s an d c h a r g in g them i n t o t h e m a c h in e s (th e two d u s t i e s t p a r ts o f a g u n itin g jo b ). Sam ples ta k e n d u rin g th e s e o p e ra tio n s showed th e fo llo w in g d u s t counts o f p a r ti c le s te n m icrons o r le s s in size* -3 0 - Op e r a t i o n P a r t i c l e s p e r ovu f t . S creening sand p rio r to m ixing w ith cem ent.. M ix in g b a t c h ................... ................................................... S h o v e lin g m ix i n t o h o p p e r................. ....................... 2,493,160 1 ,6 9 9 ,2 0 0 6 ,4 8 5 ,2 8 0 About 40$ o f th e d u st p a r tic le s in sam ples taken w hile m ixing th e b atch and f i l l i n g th e hopper were c r y s ta l lin e , q u a r tz - lik e in ap p earan ce, and a b o u t fiv e mi cro n s in s iz e . The rem ainder were d ark g rey in c o lo r and below one m ioron in s iz e . The d u s t p a r t i c l e s ' i n a i r ooming o u t o f th e bottom m anhole of a so a k in g drum b e in g g u n ited averaged 528,640 p a r tic le s p er cubic fo o t, and w ere s lig h tly an g u lar, c r y s ta l lin e in appearance and four m icrons o r le s s in s iz e , A g u n ite crew c o n s is ts of s ix men. The av era g e se rv io e c r e d i t of th e men in t h e Crews s t u d i e d was e i g h t y e a r s . Two " n o z z le -m e n " who " s p e l l " e a c h o th e r e v e ry two o r th re e h o u rs apply th e g u n ite. T here i s one man a t th e g u n ite m aohine, and t h r e e men so re e n th e sand and mix i t w ith cement. Only about 25$ o f t h e i r w orking tim e , o r n in e h o u rs per week p e r man, i s dpvoted to g u n itin g . R em oval o f G u n ite L i n i n g* P n e u m a tio c h i s e l s a r e u s e d t o rem ove g u n it e l i n i n g , Samples ta k e n from in s id e a crack in g c o il t a r s e p a ra to r during th is o p e ra tio n had as h ig h as 1 6 ,595,520 p a r tic le s o f d u st, te n m icrons or le s s in B ize, per oubio fo o t, and an av erag e of 10,804,080 p a r tic le s per cubic fo o t. About 75$ o f th e s e p a r tic le s w ere rounded, a n g u la r, m ore or le s s opaque, in a p p e a ra n c e , one m ioron o r le s s in s iz e , and 25$ w ere a n g u la r, q u a r tz - lik e , ab o u t te n m iorons or le s s in s iz e , A chem i c a l a n a l y s i s o f t h e g u n i t e l i n i n g show ed t h a t i t c o n t a in e d 68, 2$ f r e e s i l i c a . F o u r 'p from th e P la n t Labor D epartm ent, w ith an av era g e s e rv io e o f sev en y e a r s , spend Jo u t tw en ty h o u rs p er week rem oving g u n ite li n in g s from p rooess equipm ent,, An a i r syphon p ro v id es v e n tila tio n , and th e men a re re q u ire d to u se th e goggles and r e s p ir a to r s w hich a r e fu rn is h e d them, V - WELDING AND CUTTING OPERATIONS W elding h as never b een c o n sid e re d a d u st-p ro d u c in g o p eratio n . However, our s tu d ie s and th o s e o f o th e rs in d ic a te t h a t th e u se o f th e modern c o a te d e le c tr o d e s or rods p roduces a la r g e amount o f d u s t in a d d itio n to th e fumes w hich a r e ev o lv ed , An e le c tr ic arc is used fo r m ost o f th e w elding around r e fin e rie s . There a re a number o f w eld in g jo b s , however, fo r which o x y -a c e ty le n e is used O xy-acetylene is a lso used fo r p ra c tic a lly a ll burning or c u ttin g . A WELDING OPERATIONS; 1 ELECTRIC ARC WELDING; E l e c t r i c a r c w e ld in g i s u se d an a l l t y p e s o f c o n s t r u c t i o n and r e p a ir work. The av era g e s e r v ic e o f th e e l e c tr i c w eld ers is ab o u t two y e a rs and m ost o f them came from th e L abor D epartm ent, h av in g been d eveloped in to w elders a t th e in d iv id u a l p la n ts . They a re exposed to p a rtic u la te m atter generated by th e w elding o p eratio n on an average of s ix hours per s h i f t , n in e s h if ts out of fo u rte e n , This p a rtic u la te m a tte r is o r d in a r i ly r e f e r r e d to as "fumes o r sm okes". The p a r t i c l e s when found have a much s m a lle r s iz e ran g e th a n t h a t o f d u s t, suoh a s s i l i c a . W ith same o p e r a tio n s t h e r e may a l s o be some d u s t p r e s e n t, b u t th e p ro d u c t form ed from 'v o l a t i l i z i n g th e m e ta l and ro d c o a tin g s i s commonly term ed a "fum e". A ll w elders a re provided w ith approved hand s h ie ld or helm ets equipped w ith #10 Noviweld le n s . W elding in shops is done in canvas o r wooden b o o th s. A steam o r a i r syphon is in s ta lle d when any a rc w elding i s done in s id e of c lo se d v e s s e ls such as drums o r tow ers What a r e C oated E le c tro d e s ? Coated e le c tro d e s a r e m etal w elding rods co v ered N E E c RZ RZ RtZ RZ RZ Rl Jfc Jfcz Jt lr " 31- w ith a com position which p re v e n ts o x id a tio n and p erm its th e fo rm atio n o f s tro n g e r and `p o r e u n ifo rm w e ld s. What Do These E l e c t r o d e s C o n ta in and W hat P ro d u c ts R e s u lt From T h e i r TJse? I n g e n e ra l, th e co atin g s u sed in modern coated w elding e le c tro d e s a re p a te n te d or tra d e s e c re ts , w ith sp ecial v ir tu e s a ttr ib u te d to each. O bviously, i t is in a d v isab le to p u t in t o th e s e c o a tin g s m a t e r i a l s w h ich m ig h t p ro d u ce p ro d u c ts h arm fu l t o man. N ev erth eless, chem ical a n a ly se s o f b o th th e c o a tin g s and t h e i r p ro d u cts in d ic a te th a t th e c o n tin u a l use of same o f th e se rods m ight p o s sib ly le ad to co m p lica tio n s. Most o f th e a rc w elding a t our a f f i l i a t e d p la n ts i s done w ith #5 F leetw eld c o ated e le c tro d e s which come in two s iz e s (5 /3 2 " and 3 /l 6 " ) and w ith G en eral E le c t r i c W-20 5 /3 2 " c o a te d r o d s . - O th e r ro d s som etim es u s e d a r e # 4 S ta in w e ld Ka2S a l l o y w elding ro d , 5/32" S tain w eld A rods fo r s ta in le s s s te e l, and Murex N iokel S te e l c o a t ed ro d s . Among th e c o n s t i t u e n t s o f some o f t h e s e e l e c t r o d e s c o a t i n g s a re s Coated E le c tro d e Brand SiOz Per Cent. F lu o rin e Calcium F luoride " F le e tw e ld " , L in c o ln E l e c t r i c Co......................3 0 .2 8 "M urex", A m erican M e ta l & T h e rm ite Co..........28 .0 5 "USS C r-N i 1 8 - 8 " , Amer. S t e e l & W ire Co, . . . 3 7 , 20 " S ta in w e ld " , L in c o ln E l e c t r i c C o . . . ...............12,1 0 1 " R e z ista l K-A-25", C ru cib le S te e l Co.....,2 4 .0 3 21,20 13.40 14, 50 43, 50 present A ll o f th e above c o a tin g s also' c o n ta in Iro n Oxide (F6203) M anganese O xide, e i t h e r Mn203 o r MnO o r b o t h , and Aluminum O xide (A I2 O3 ) , i n v a r y in g p e r centages. The c o m p o sitio n o f th e f lu x e s o r c o a tin g s u sed in G & E ty p e s W-20, W-22 and W-23 i s n o t a v a i l a b l e , b u t i t i s known t h a t th e y c o n ta in am ounts o f f r e e s i l i c a t e s and f r e e s i l i c a . . A ccording to d e te rm in a tio n s made by th e G eneral E le c tr ic Company, th e maximum c o n c e n tr a tio n o f f r e e s i l i c a on a n y o f t h e i r e le c tr o d e s u n d e r a p a r t i c u l a r s e t o f c o n d i tio n s i s 1 ,5 7 5 ,0 0 0 p a r t i c l e s p e r c u b ic f o o t o f a i r w i t h W-20, 7 7 8 ,0Q0 w ith W-22, and 1 ,0 9 3 ,0 0 0 w ith W-23 u n d e r o th e r c o n d itio n s th e c o n c e n tr a ti o n s m ig h t be h i g h e r o r lo w er th a n th o s e g iv e n . The maximum p e r m i s s i b le c o n c e n t r a t i o n a s l i s t e d by t h e M e tr o p o lita n L i f e In s u r a n c e Company i s 7 ,0 0 0 ,0 0 0 p a r t i c l e s p e r c u b ic f o o t o f a ir. C oatings a lso c o n ta in c o tto n f ib e r , c e llu lo s e , or o th e r o rg an ic p u lp which c r e a t e s fum es, b u t s i n c e we a r e o n ly c o n c e rn e d w ith d u s t i n t h i s s tu d y a l l fume p r o ducing m a te ria ls w ill re c e iv e no fu rth e r co n sid eratio n . W elding c o r r o s io n - r e s is tin g s te e l w ith co ated c o r r o s io n - r e s is tin g s te e l e le c tr o d e s form s a s la g , among th e m ajo r c o n s titu e n ts o f w hich a r e t " S ta in w e ld " USS CR-Ni 1 8 -8 " R e z i s t a l " F l u o r i n e ( F ) ......... .......................................... ft 6 S ilic a (SO2) . . . . . . . . . . . . . . . . . . . . . . I r o n , Chromium and M anganese O xides C alcium Oxide (CaO). 1 1 . 4%. 9 0 0 0 00 69 6/Oa e 0 0 ft a o 0 . .14 9% 2 5 . 1 % ft ft 0 .9 9 3 80 $ e 0 ft 9 0 0 ft a o 13 22$ o a$ 0 9 24$ 2% ft O Q 0 ft ft 0 a 0 1 6 . Z % 5 0 , 7 % a a o09a e 28 Oj&s 9 ft ft ft o 0 9 e e 26 TI% '} The m ajor c o n s titu e n ts o f d u s ts se p a ra te d from atm osphere by g ra v ity and c o l le c te d from th e bottom s o f w elding chambers a f t e r w elding c o r r o s io n - r e s is tin g s te e l p la te s w ith coated c o rro s io n -re s is tin g s te e l w elding rods are? " 32- " S ta in w e ld " USS CR-Ni 1 8 -8 " R e z i s t a l " I J h-J.y1" S i l i c a (SiO ) ............................................ 1 1 .0 $ .............................. C aloium F lu o r id e (C aF ) ......................... 4 0 .5 $ .................... O xides o f I r o n , Aluminum andN ic k e l, 3 0 ,2 $ ................... 1 9 . 6 $ ................ 1 1 ,4 $ 5 2 .1 $ 1 0 .0 $ 23,4$ 36.6$ The fo llo w in g i s an in te r e s tin g com parison betw een th e co m p o sitio n s o f d u st formed when u s in g b a re m ild s t e e l e le c tro d e s and when u s in g c o a te d e le c tro d e s fo r w elding g alvanized s te e lt Brand "Fleetw eld" "W ilson" "Murex" Bare E lectrodes $ ZnO $ Feg03 7 9 .2 6 2 ,6 60.5 20,0 60.5 40.0 Coated E le c tro d e s $ ZnO $ F e203 6 7 .5 78. 8 72.0 3 1 ,9 21.5 2 8 ,0 I n v e s t i g a t i o n s h a v e shown t h a t t h e r e may b e a s much a s a f iv e p e r c e n t, v a r i a t i o n in co m p o sitio n o f d u s t produced by th e same make and k in d o f e le c tr o d e when used under co n stan t co n d itio n s but by d iffe re n t operators. F e r r ic oxide (Fe2Q3) w hich em anates from a l l w eld in g a r c s , r e g a rd le s s o f th e type o f co atin g , is d isa g re e a b le b u t not harm ful. C o n cen tratio n s of iro n oxide o f about te n m illig ram s per cubic m eter a re said to be e n tire ly n o n -in ju rio u s to th e re s p ira to ry organs. B rea th in g th e dense clo u d s o f fumes of zinc o x id e , form ed when th e zin c o f th e g a lv a n iz e d c o a tin g i s b o i l e d o f f by th e h e a t o f th e w e ld in g a r c , c a u se s w hat i s com.o n ly known as "fume f e v e r" . This is evidenced by n au sea fo llo w ed by c h i l l s and un p le a s a n t f e v e r. The fume f e v e r does no l a s t i n g harm e x c e p t a f t e r p ro lo n g e d ex p o su re, and th e e f f e c ts a re n o t cu m u lativ e. O rdinary v e n tila tio n , which is n e c e ssa ry in any w e ld in g 'o p e r a tio n , i s c o n s id e re d a d e q u a te to p re v e n t fume fe v e r. W hat I s The Amount And W hat A re The C h a r a c t e r i s t i c s o f D ust P roduc ed By The V arious E le c tr ic Arc W elding O p eratio n s? There i s a w ide v a r ia tio n in th e amount and c h a ra c te r o f d u st produced by d if f e r e n t types of rods on d if f e r e n t m a te ria ls under d iffe re n t operating conditions. FUME, OR DUST PRODUCED BY ARC WELDING M a te ria l Being E le c tro d e S ize o f P a r tic le s W elded Used E lectro d e Per cu, f t . R ivets in sid e Cross C o il Drum, G-E W-20 C o ated 5 /3 2 " 2 0 ,0 5 0 ,5 6 0 M ild S te e l Blanks In s id e B o p th , G-E W-20 C oated 5/32" 1 4 ,8 3 9 ,6 8 0 C h a ra c te ris tic s o f Dust P a rtic le s , (S izes and Per centages E stim ated) A bout 98$ singular c r y s ta l lin e , 5 m icrons or le ss in s iz e j 2$ rounded sem i-opaque, 10 m icrons or more in siz e . About 80$ round black or red d is h brown sp eck s, 1 m icrons or l e s s in s iz e j 20$ s l i g h t l y angu l a r c r y s ta llin e , 10 m icrons or le s s b u t m ostly about 5 m icrons and la rg e number re d d is h brown specks to o sm all and numerous to count. -3 3 - FUME OR DUST PRODUCED BY ARC WELDING ( C o n t i n u e d ) M a te ria l Being E le c tro d e Size of P a r tic le s Welded Used E lectro d e P er cu. f t . 1/4" B oiler P late Inside Booth* #5 F le e tw eld C oated 5/52" 1 1 1 ,4 4 1 ,2 8 0 1-1/4" Ilild S te e l Expan sion Jo in t In s id e Bootln #5 F le e tw eld C o ated 3/16" 19,861,793 1/2" R olled S teel (5 5 ,0 0 0 /f p e r sq, iru T e n sile strength) In s id e 6+Foot Dia, drum n e a r head o f closed end. #5 F lee tw eld C o ated W elding Flange on 4" S tee l Line Pipe, In s id e Booth* Mur ex C o ated 5/8" B oiler P la te Inside B o o th . #5 F le e tw eld C o ated 3/16" 2 ,2 6 5 ,6 0 0 3/32" 2 ,7 5 6 ,4 8 0 5/32" 490,880 W elding Riv e ts in C ourtney Edge In s id e Crack in g C oil S o a k in g Drum. #5 F le e tw eld C o ated 5/32" 6 ,4 5 6 ,9 6 0 C h a ra c te ris tic s of Dust P a rtic le s , (Sizes and Per centages Estim ated) About 8 0 /angular c ry s ta llin e , 3 m icrons or le s s in siz e ; 10% round sem i-opaque, 10 m icrons o r more in siz e ? 10% opaque s c a le l i k e , 10 mi cro n s o r le ss in s iz e . Count le s s number o f m inute p ar t i c l e s , re d d ish brown smudge. About 95 / angular c ry s ta l lin e , 3 m icrons or le s s in s iz e j 5% rounded sem i-opaque , 10 m icrons o r le s s . Count le s s number of p a r tic le s re d d is h brown smudge. A ll p a rtic le s 5 m icrons or le s s in s iz e ; about 10/ an g u lar sem i-opaque. A ll p a r tic le s 2 m icrons or less in sizej slig h tly angular, g la ss-1 ikej dark g rey smudge. About 7 5 / round, m e ta llic opaque, 5 m icrons in s iz e j 25% sem i-opaque, c ry s ta l lin e , C ountless number o f m inute p a rtic le s About 90% sharply angular c ry s ta llin e , about 1 m icron or le s s in s iz e j 10/ rounded sem i-opaque, 5 mi crons o r more. C ountless number of m inute p a r tic le s .  34- ! M a t e r i a l B ein g FEUlIe-IEc t rOoRd eDUST SPiRz Oe DUoCf ED BYP aArRtCi c Wl eEsLDINGC(hCaornatci nt eu reids)t i c s o f D u st -1 W elded Used E le c tro d e P er cu, f t . P a r tic le s , (S iz e s and Per centages E stim ated) 1 18-8 S ta in le s s Stainw eld 5/32" 849,600 About 60$ s lig h tly angular 1 S te e l Band a t A Top o f Soaking C oated sem i-opaque, 5 m icrons or le s s in s iz e j 20$ rounded, 1 Drum M anhead over 10 m icro n sj 20$ -very g la s s - lik e , 10 m i- V crons or le ss. 1/2" B o ile r P la te to 6" G-E W20 C o ated 3/16" 23,222,400 About 80$ sesmi-opaque, re d d ish brown rounded, c r y s ta l- mm Pipe In sid e Booth lin e , 5 m icrons or le s s j 20$ round glo b u les o f m etal 5 ft m icrons o r more in s iz e . C ountless number o f sm all ft p articles. ft 1/2" B o iler R oebling 5/32" 26,592,480 About 90$ b lack opaque, 1 P la te to 6" Iron m icron or le s s in s iz e j 5$ ft Pipe In sid e Rod Booth, roundedm etallio globular, 5 m icrons or le s s j 5$ s lig h t ft: ly angular, sem i-opaque, c ry s ta llin e , 3 m icrons or ft le s s . C ountless number re d d is h brown p a r t i c l e ? , ' ft Back W elding F leetw eld 5/32" 382,496 About 95$ b lack opaque ft a F lange on 6" Standard #7 C o ated m e ta llic , 2 m icrons or le ss j 5$ angular c ry s ta llin e , ft P ip e in Outs id e W elding 5 m icrons or le s s . Count- le s s number o f re d d ish Kl Shop brown p a r tic le s . ft Back W elding E L eetw eld 5 /3 2 " 1 ,0 0 0 ,6 4 0 About 95$ b lack opaque a F lan g e on #7 m e ta llic , 2 m icrons o r ft 6" Standard C o ated le s s j 5 $ angular c ry sta - Pipe In sid e ll in e , 5 m icrons or le s s . ft Booth C ountless number o f black p a rtic le s. ft W elding R iv- Fleetw eld 5/32" 6 ,2 5 3 ,0 5 6 About 95$ an g u lar c r y s ta l- fcj ets Inside C racking #7 C oated lin e , 5 m icrons or le s s , m ostly around 2 m icro n sj5 $ ft C oil Vapor- sem i-opaque, round, 5 m i- iz e r (M ild crons. C ountless number of S te e l Alumi num C oated) black p a rtic le s . ft 3C3 -3 5 - FUME OR DUST PRODUCED BY ARC WELDING ( C o n t i n u e d ) M a te ria l Being E le c tro d e S ize of W elded Used E le c tro d e W elding 2" R ing on 1" M ild S te e l B oiler P late In s id e Booth, Fleetw eld #7 C o ated 3 /6 " M ild S te e l So ra p P la te s I n s id e Booth, KagS S te e l In s id e B o o th , Stainw eld A C o ated Stainw eld A Coated 5/32" 5/32" P articles Per cu, ft. 2 7 ,6 6 2 ,9 7 6 2 ,6 0 5 ,4 4 0 1 2 ,4 6 0 ,8 0 0 C h a ra c te ris tic s of Dust P a r tic le s . (S iz e s and P er centages E stim ated) A ll p a rtic le s le ss than 2 m icrons. 70$ round, opaquej 30$ s lig h tly angular, c ry s ta l lin e , C ountless number of black p a rtic le s , reddish brown smudge. A ll p a rtic le s black opaque, 2 m icrons or le ss in siz e . About 80$ an g u lar opaque, 2 m icro n s o r l e s s j 20$ s l i g h t ly angular c ry s ta llin e , 5 m icrons or le ss . C ountless number black p a r tic le s , brow nish grey smudge. The U, S.N avy r e c e n t l y c o n d u c te d some e x t e n s i v e t e s t s w ith c o a t e d e le c tr o d e s ,, and found th a t th e q u a n tity o f d u st or fumes developed w h ile w elding on g alv an ized s t e e l p l a t e was g r e a te r th a n when b a r e s t e e l p la te s w ere u sed and th e d u s t rem ain ed in su sp e n sio n f o r f a r lo n g e r p e rio d s o f tim e . I t was a ls o found t h a t th e av era g e s iz e o f th e d u s t p a r t i c l e s was 0 .2 7 m icro n s and t h a t th e re w ere 130,000 p a r t i c l e s u n d er fo u r m icro n s d ia m e te r p er c u b ic c e n tim e te r. Q uoting th e Navy r e p o r tt !,I t i s a p p a re n t t h a t c o n s id e r a b le q u a n t i t i e s o f d u s t a r e found i n any a ro w elding o p e ra tio n . The d u s t formed when o p e ra tin g on p la in m ild s te e l or c o rro sio n r e s is tin g s te e l is la rg e ly d eriv ed from th e flu x co atin g on th e e le c tro d e s , as is shown by th e co m p o sitio n o f th e s e d u s ts " . What P h y s io lo g ic a l E ffe c t on W elders i s Produced by The Use o f C oated E l e c t r o d e s . A c c o rd in g t o a s tu d y made by D o c to rs A. T. D oig and A. P. G. M cL aughlin on lungs o f E le c tr ic Arc W elders (L an cet - V .20j 771 - 775 (A p ril 4, 1 9 3 6 )), d e f i n i t e pulm onary le sio n s w hich gave r i s e to s tr ik i n g X -ray changes in th e appearance o f th e lu n g s w ere found in w e ld e rs w hich had b re a th e d +he d u s t or fume from co ated e le c tro d e s . Q uoting D octors Doig and M cLaughlins "The e le c tro d e s o r w elding rods w hich c o n ta in a co re of m etal and an o u te r co v erin g are consumed g ra d u a lly by th e h e a t g en era ted (about 1500C. ) d u rin g th e w elding o p e ra tio n . The m e tal in th e core o f th e rod becomes m olten and, a s s is te d by th e flu x contained in the covering, spreads over th e s u r f a c e o f th e m e ta l w hich i s b e in g w elded. The fume is t h e r e f o r e made up o f th e v o la tiliz e d c o n s titu e n ts of th e coverings of th e rods to g e th e r w ith fin e p a r tic le s o f oxidized m e tal, u s u a lly in th e form of iro n oxides. In a d d itio n th e fumes p ro b ab ly c o n ta in g a se s such as n itro g e n p e ro x id e and ozone which a re form ed by th e a c tio n o f an e l e c tr i c sp a rk on th e a i r . The com position o f the coverings o f th e e le c tro d e s or w elding rods becomes, in th e c irc u m s ta n c e s , a m a tte r o f some im p o rta n c e . Many s u b s ta n c e s , a l l o f w h ich we do n o t p ro p o s e t o e n u m e ra te , a r e u se d . The b a s i s o f t h e m a j o r i t y o f th e co v erin g s is sodium s i l i c a t e w hich a c ts as a flu x . A gain, th e -3 6 coverings of a c e r ta in type o f e le c tro d e co n tain asb esto s. The rods a re sometimes dipped in a m ix tu re c o n ta in in g powdered a sb e sto s and sodium s i l i c a te , o r a s b e s to s y a r n is wound round th e rod and fix e d by sodium s i l i c a t e . I n some c a se s th e a s b e s to s c o m p le te ly co v ers t h e ro d s, and i n o th e rs i t i s m e re ly a co rd w h ich i s wound s p i r a l l y ab o u t th e ro d . "The co m p o sitio n o f th e fumes a ris in g from e l e c tr i c w eld in g e le c tro d e s h a s n o t y e t b e e n f u l l y i n v e s t i g a t e d , Mr, L ,C , M cN air, H.M E n g in e e r in g I n s p e c to r o f F a c to r ie s , has however had p a r t i a l a n a ly s is made o f th e fumes evolved from an a s b e s to s -c o v e re d e le c tro d e and some a s b e s to s f ib r e s w ere fo u n d . When t h e p a r t i c u l a t e m a t t e r o f t h e fum es was c o l l e c t e d i n a n O wen's d u st-co u n ter, i t was seen th a t a la rg e p ro p o rtio n c o n siste d o f iro n oxide I p a rtic le s , w ith an o ccasio n al asb esto s fib re, I "The X -ray appearances in th e w ell-m arked cases d if f e r from th e u su al p ic tu re o f a s b e s to s is . In none o f th e p o s itiv e cases and in o n ly one o f I th e su sp ic io u s c a se s was th e re any b lu rrin g o f th e d iap h rag m atic shadow, and in no case was th e h e a r t o u tlin e d b lu rre d . The l i n e o f th e i n t e r l o I b a r septum (a f e a t u r e p re s e n t in a nfonber o f f ilm s o f c a s e s o f a s b e s to s is ) i s seen in o n ly one p o s i t i v e c a s e . The o p a c i tie s i n th e f ilm s a r e n o t a c I cen tu ate d a t th e b a se s of th e lu n g s, but on th e c o n tra ry th e upper lung f ie ld s appear to be th e e a r lie s t, and in e s ta b lis h e d c a se s, m ost m arkedly I a ffe c te d . B efore a s b e s to s is can be elim inated from the d if f e r e n tia l d ia g n o sis i t m ust be remembered th a t th e a s b e s to s fib re s a re b ein g su b jected I t o in te n s e h e a t and a r e n o t i n th e same p h y s ic a l s t a t e a s th e f i b r e s w hich a re inhaled by w orkers in an asb esto s factory. I t is p o ssib le th a t a I ty p ic a l p ic tu re o f a sb e sto sis m ight be produced by th e in h a la tio n of a l te r ed asb e sto s. M erewether. says th a t - 'th e ra d io g ra p h ic ap p earan ces o f th e I developed or advanced s ta te s of a sb e sto sis a re d is tin c tiv e , although th ey a re n o t s p e c ific . W hile, as is th e case w ith s i l i c o s i s , c e r ta in ra d io - 1 grap h ic appearances-m ay be looked upon as ty p ic a l o f th e d is e a s e , fre q u e n t ly m o d ific a tio n s o f and d e p a rtu re from th e ty p ic a l p ic tu r e o c c u r' , The I X -ray appearances in our cases m ost clo sely resem ble those o f a fin e s i l i - o o s is , b u t th e c l i n i c a l f e a tu r e s show two im p o rta n t d if f e r e n c e s . In th e I f i r s t p la c e , t h e e l e c t r i c w e ld e r s whom we exam ined a r e a l l i n good h e a l t h and a r e f i t t o w ork. The o n ly symptoms o b se rv e d w ere s l i g h t cough and I m orning e x p e c to ra tio n , and in th e f i r s t case a sm all haem optysis occurred. T h is man has n o t b e e n away from work even f o r a day s in c e h e was f i r s t K seen in June, 1933, and h is h e a l th a t th e p r e s e n t tim e is good. None o f th e men s u ffe rs from dyspnaea. Secondly none o f them has concom itant X pulm onary tu b e rc u lo s is , t "M iliary tu b e rc u lo s is can be ruled out o f th e d if f e r e n tia l diagno s i s f o r c lin ic a l re a s o n s , and to same e x te n t on th e r a d io lo g ic a l appear X a n c e s . None o f t h e c a s e s show s t h e d y s p n a e a , c y a n o s i s , and t a c h y c a r d i a o f acu te or su b acu te m ilia ry tu b e rc u lo s is . C hronic or h ealed m ilia ry tu b e rc u lo s is is r a r e and i t is d if f i c u lt to im agine th a t a c o n d itio n of s u c h r a r i t y w ould b e fo u n d i n 6 o u t o f one g ro u p o f 16 men. I n t h e I X -ray film s of th e w eld ers' c h e sts th e fin e o p a c itie s are irre g u la r in s iz e and shape, w hereas in m ilia ry tu b e rc u lo s is o f th e lung th e shadows a re more uniform , I; "A f u r t h e r p o s s i b l e e x p l a n a ti o n o f th e X - r a y a p p e a r a n c e s i n t h i s se rie s of cases is th a t the in h a la tio n of sm all q u a n titie s of n itro u s X: fumes to g e th e r w ith th e superadded e f f e c t o f f in e iro n o x id e d u s t m ig h t s e t up sm all area s o f chronic inflairaratory change, co n g estio n , o r f i b ro s is in th e lu n g s. A gain, th e iro n oxide p a r ti c le s m ig h t be opaque to th e X -rays and p ro d u ce th e p ic tu re w ith o u t th e a s s o c ia te d p resen ce Xr o f .f i b r o s i s and c o n g e s tio n . 2. OXY-ACETYLENE '.ELDING; O x y -a c e ty le n e w e ld in g i s m ore o r l e s s c o n f in e d t o sm all re p a ir jo b s or to c e rta in emergency o p e ra tio n s where a rc w elding is n o t a v a ila b le o r p r a c t i c a l . Exposure o f men d o in g w elding is more or le s s irre g u l a r , They u s tia lly w ear Am erican O p tic a l Company or W illso n W elding G oggles w ith ifjr4 N oviw eld l e n s . The am ount o f d u s t p ro d u c e d by o x y - a c e ty le n e w e ld in g is considerably le ss th an th a t caused by th e use of coated electro d es in arc w elding, and v a rie s c o n sid e ra b ly w ith th e s ty le t i p and w elding rod being used as w ell as th e m a te r ia l w elded, as is shown by th e fo llo w in g ta b le t DUST PRODUCED BY OXY-ACETYLENE WELDING M a te ria l Being Welded W elding Rod Tip Used P a rtic le s Per Cvu F t. C h a ra c te ris tic s o f Dust P a rtic le s (S izes and Per centages E stim ated) G alvanized M etal Hood W elding Shop. Norway 5/32" A ireo #4 396,480 A b o u t 70/o s l i g h t l y a n g u l a r , sem i-opaque, g re y is h , 5 m i cro n s or le s s ; 20$ rounded sem i-opaque, g rey ish cry s t a l l i n e , 10 m icrons o r more; 10% amorphous, s c a le - lik e ; 10 m icrons or more in siz e . l/4 " x 2" Bar Iro n , Welding Shop. Oxweld co p p e riz e d s te e l 3/16" A ireo #8 509,760 A bout 80% b la c k opaque, 1 m icron or less in siz e ; about 20% rounded, c ry s ta llin e ; 5 m icrons or le ss in size. l / 2 , r B oiler P late, Soft S te e l, Weld in g Shop, Oxweld co p p e riz e d steel l/8 " Oxweld 1 ,0 1 9 ,5 2 0 About 80% round, sem i-opaque, 5 m icrons or le ss in siz e ; 10% angular c ry s ta llin e . C ountless number o f sm all black p a rtic le s. l/8 " Galvan ized Sheet I r o n , Weld in g Shop, Oxweld c o p peri zed s te e l, l/8 " Oxweld 1 ,3 5 9 ,3 6 0 About 80% rounded, sem i opaque, dark grey, 1 m icron or le s s in size; 10$ s lig h tly a n g u la r c r y s ta l lin e , 3 mi crons or le ss; 10% sharply an g u la r c r y s ta l lin e , 5 m i crons or le ss; countless number of sm all dark grey p a rtic le s W elding T eeth on Band Saw. Simmons Saw W elding Rod, 3 /6 4 " Aero plane #2 1 ,4 7 2 ,6 4 0 About 98% round b la c k opaque, ab o u t 1 m icron o r le s s in siz e ; 2% slig h tly angular, c r y s ta llin e , 3 m icrons o r le ss in size. B - BURNING OR CUTTING OPERATIONS; 1 WITH OXY-ACETYLENEt The o x y - a c e ty le n e t o r c h i s u sed b o th in th e c o n s t r u c t i o n -3 8 - and th e d e m o litio n o f p ro cess equipm ent and works s tr u c tu r e s . I t a ls o p la y s an im p o rta n t p a r t in emergency and rescu e work. Goggles w ith shade #5 Noviw eld le n s a r e p ro v id e d and t h e i r u s e i s r e q u ir e d . At th e l a r g e r p la n ts men w ith an average s e rv ic e c re d it of s ix years spend about th re e -fo u rth s of th e ir w orking tim e on c u ttin g o r burning o p e ra tio n s (about h a lf th e ir tim e i s g iv e n to " b u rn in g s te e l " fo r new c o n s tr u c tio n ) . The amount o f d u s t pro duced is u su ally g re a te r than th a t caused by o x y-acetylene w elding. DUST PRODUCED BY OXY-ACETYLENE BURNING M a te ria l Being P articles Burned - - T ip Used p e r cu, f t . C h a ra c te ris tic s of Dust P a rtic le s (S izes and Percentages E stim ated) B u rn in g 6" Flues (1-1/2" th ic k ) Out of S hell S till. Oxweld #2 1 ,8 6 9 ,1 2 0 A bout 75/o ro u n d b l a c k , 2 m ic ro n s or le ss in s iz e j 20% s lig h tly a n g u lar, c r y s ta llin e , 2 m icrons or le s s j 5% opaque, s c a le -lik e , \ various siz e s. l/2 " B oiler P late (so ft s te e l) Oxweld #4 2 ,7 1 8 ,7 2 0 About 90% sem i-opaque, b lack , 2 m icrons or le ss 10% round, dark grey, over 5 m icrons in siz e . 2 WITH NATURAL GAS? A l a r g e p a r t o f th e b u r n in g o r c u t t i n g a t one o f t h e la r g e r so u th ern r e f in e r ie s is done w ith oxygen and n a tu ra l gas (60 pounds p er sq u are in c h p re s s u re ), A s p e c ia l to rc h w ith a l / l 6 " x 5 /l6 " t i p made in t h e r e f i n e r y sh o p s i s u sed . Two men w ith a n a v e r a g e s e r v i c e o f t h i r t e e n y e a r s spend a m a jo r p o r t i o n o f t h e i r w o rk in g tim e on t h i s n a t u r a l gas., They w ear goggles w ith #5 shade Noviweld le n s . Sam ples ta k e n w h ile b u rn in g h o le s i n 3" s ta n d a r d p ip e i n th e y a rd o u t s i d e o f w e ld in g sh o p w ith o x y g en a,nd n a t u r a l gas had a c o n c e n tra tio n o f 471,811 p a r tic le s , te n m icrons or le s s in s iz e , p e r cu b ic fo o t. About 15% of th e s e p a r ti c le s w ere s lig h t ly a n g u la r c r y s t a l l i n e in appearance u nder th e Konim eter m icroscope, and were fiv e m icrons or le s s in s iz e j 25% were rough s c a le - lik e , opaque, te n m icrons o r le s s in siz e . T here w ere a ls o many m inute p a r t i c l e s , - HEALTH HAZARDS PRODUCED BY WELDING AND BURNING OPERATIONS .A lthough o u r stu d y was co n fin e d to th e fumes o r d u s t produced by W elding and C u ttin g o pera ti o n th e p b s s ib ility o f lead p o iso n in g from w elding or c u ttin g iro n p la te s th a t have been p re v io u s ly coated w ith red le ad should be p o in ted o u t. Lead p o is o n in g from t h i s s o u r c e i s r a t h e r common, e s p e c i a l l y i n c u t t i n g up o ld s c r a p , b r id g e s , ta n k s , and o th e r ir o n s tr u c tu r e s t h a t have th ro u g h many y e a rs o f use rece iv ed p ro te c tiv e co atin g s o f red le a d . The a c tio n o f th e flam e v o l a t i l i z e s t h i s le a d m a te r ia l and c r e a te s a smoke th a t i s p o iso n o u s. The same h aza rd e x is ts in c u ttin g out r i v e t s in new s tr u c tu r e s . I t sh o u ld a ls o b e p o in ted o u t t h a t some o f th e w eld in g ro d s c o n ta in m anganese which is v e ry poisonous when ta k en in to th e body. There is an ap p a re n t hazard from v o la tiliz in g th is m a te ria l, o r ra th e r changing i t to th o o x id e o f m anganese, and b re a th in g th e fumes produced. There a re f u r th e r dangers from carbon m onoxide and oxygen d e fic ie n c y owing to th e u se o f g a s - c u ttin g or w elding flam es in s id e sm all tanks o r s im ila r co n fin ed spaces. I t is becom ing more and more reco g n ized t h a t persons engaged in c u ttin g and w elding o p e ra tio n s, e ith e r by a rc or flam e, should have re s p ira to ry p ro te c t i o n , in a l l work w here th e re i s a p o s s i b i l i t y o f th e workmen b r e a th in g fumes and d u sts created . VI - GRINDING OPERATIONS Power g rin d e rs a re perhaps th e m ost u n iv e rs a lly used of th e sm all pow erd r iv e n to o ls The u s u a l power g rin d e r, commonly known a s th e emery w heel, c o n s i s t s o f a c a s t m e tal stan d and two a b ra siv e w heels mounted on a through s h a f t which is e ith e r b e lt o r m otor d riv en . There are a ls o sev eral g rin d in g w heels, such as a re found on m achine to o l equipm ent where g rin d in g tak es th e p la c e o f la th e and p la n e r work. A ll g rin d in g o p e ra tio n s produce d u s t to a g re a te r o r le s s e r degree, depending on th e co m p o sitio n and c o n s tru c tio n of th e w heel, the- m a te ria l b e in g ground and th e v e n tila tio n or exhaust hoods provided, ...W hat i s th e C om position of G rin d in g W heels? G rin d in g w heels a re made o f e ith e r b a u x ite which i s m ined, or s i l i c o n c a rb id e which is made by h e a tin g a m ix t u r e o f q u a r t s s a n d , c o k e and common s a l t i n a n e l e c t r i o f u r n a c e . The b a u x i t e o r s ilic o n c a rb id e are cru sh ed to th e d e sire d g ra in s iz e , m ixed w ith an ad h esiv e sub s ta n c e c a lle d a bond, and formed in to w heels, d is c s , cones o r c y lin d e rs . There a re many w h eels i n w hich t h e b in d e r is s h e l l a c , ru b b e r, b a k e l i t e and o th e r o rg a n ic cam" pounds. B a u x ite w heels a r e known in th e shop as "Alundum" and " A lo x ite " , w h ile s i l i c o n c a r b id e w heels a r e known as "C ry sto lo n " and "Carborundum ", Alundum w heels sh o u ld be u sed on m a te r ia l o f low t e n s i l e s tr e n g th s such as c a s t iro n , b r a s s , alu m i num, copper and marble I s A b r a s iv e D ust H arm fu l? A c c o rd in g t o Dr, W. I r v i n g C la r k i n a p a p e r r e a d a t a m e e tin g o f G overnm ent O f f i c i a l s i n I n d u s t r y (B o s to n - May 2 1 , 1931) t h e a r t i f i c a l a b r a s iv e s , aluminum o x id e and s i l i c o n c a rb id e do n o t c o n ta in f r e e s i l i c a and t h e i r d u st can n o t produce s ilic o s is . The d u st, lik e any o th e r inorganic d u s t, can, however, i f b reath ed fo r a long period of tim e in la rg e q u a n titie s , produce an X -ray p ic tu re s im ila r to th a t o f e a rly s il i c o s i s . This p ic tu re ohanges v ery s lig h tly as y e a rs of exposure in c re a se , and a t no tim e a re th e nodules, c h a r a c te r is tic o f s i l i c o s is , ev id en t. U nlike s ili c o s is , th e re is no pro g ress in th e process a f te r exposu re ceases and th e re ap p ears to be no marked p h y sic a l d is a b i lit y . A lthough th e re i s no s i l i c o s i s , th e X -ra y s do show s ig n s o f -pneum oconiosis. Carborundum d u s t, ch em ically , is s ilic o n carb id e. A ccording to M ille r and S ayers (U ,S, P u b ,H ealth Rep. V ol. 49 #3 o f Jan , 19, 1934) carborundum d u s t when in je c te d in to th e p e r ito n e a l c a v ity o f g u in e a p ig s produced no r e a c tio n and was term ed " in e r t" . D usts such as q u artz and f l i n t - s i l i c o s i s producing d u sts - produced a p ro life ra tiv e reaction, th a t h ig h p a rt L e ro y U, G ard n er (U. S, P u b ,H e a lth Rep. V o l, 50 $21 o f May 2 4 , 1 9 3 5 ) r e p o r t s carborundum p ro d u ces p r a c t i c a l l y no r e a c tio n when in h a le d b y g u in e a p ig s i n c o n c e n tra tio n s over a p e rio d o f tim e. Q uoting from Dr, G ardner' s a r t i c l e , th e p e rta in in g to carborundum dusts "The d u st w hich does reac h th e tra c h e o b ro n c h ia l lymph nodes a p p a re n t ly la ck s th e proper physiochem ical p ro p e rtie s to stim u la te any b u t a very s lig h t p ro life ra tio n of connective tis s u e . In the lungs, th e re is prac ti c a l l y no fib ro s is , " The Jo u rn a l o f th e American M edical A sso c ia tio n (N otes and Q ueries 103, 1472, 1934) makes t h i s sta te m e n t re g a rd in g th e h e a lth h azard o f b re a th in g dus from a r t i f ic ia l abrasives? "Only s i l i c a (SiO g) is capable o f in d u cin g s i l i c o s i s , b u t any o th e r m in e ra l d u s t under c o n d itio n s o f p ro lo n g e d and g ro ss exposure may cau se some in c re a s e in pulm onary f ib r o s is . I f th e r e l a t i v e p o t e n tia l harm o f s i l i c a i s r a te d as 100, th e s e o th e r n o n - to x ic m in e ra l d u s ts may be r a te d -4 0 - only on th e order o f 5 o r 10. " D e sp ite t h i s co m p arativ ely low r a tin g o f h arm fu ln ess o f th e s e d u s ts i t is g e n e ra lly considered ad v isab le to use d u st hoods and exhausts w herever p ra c tic a l as th e re is c lin ic a l evidence th a t w orkers exposed to heavy c o n c e n tra tio n s of du st of any k in d a re more lia b le to develop d is e a s e s a f f e c tin g th e n o se, th r o a t and c h e s t d u r in g th e w in te r months th a n th o s e n o t exposed t o d u s t. Dr, C la rk b e lie v e s th a t an e f f o r t should be made to keep th e d u s t count below tw enty m illio n p a r ti c le s of le s s th a n te n m icrons p er cubic fo o t o f a ir . l 1 , What a r e th e More F re q u e n tly Used Types o f G rin d e rs , th e Q u a n tity and C h arac ter o f t h e D ust They Produce? The g r in d e r s m ost commonly found i n t h e r e f i n e r i e s and a s s o c ia te d a c tiv itie s are* ~ A - TANDEM FLOOR TOCL GRINDERS: Tandem f l o o r t o o l g r i n d e r s , t h e m ost f r e q u e n tly used ty p e, a re in m ost c a se s m o to r-d riv en and o p e ra te a t a speed o f from \ 1450 t o 1850 RFM. The ty p e o f w h e e l o r g r in d in g m ed ia s e l e c t e d d ep e n d s upon th e ma t e r i a l to be ground. G e n e ra lly sp eak in g , th e w heels found in m ost o f th e machine I shop s and wood w orking sh o p s aro u n d o u r r e f i n e r i e s u sed : I l - l / 2 " x 10" N orton Alundum (Grade P, G r it 46) w heels fo r sharpening to o ls and f o r g en eral s e rv ic e g rin d in g , i 1 -1 /2 " to 3" x 14" Carborundum w heels f o r m isc e lla n e o u s I g rin d in g , I 3" x 16" C arborundum ( G r i t 30, G rade K) w h eels f o r g r i n d in g la th e and o th er m achine to o ls. I Som etim es two d i f f e r e n t w heels a r e u sed on tandem to o l g r in d e r s j f o r exam ple, a 2" x 8 14" g r a in 24, grade Q N orton Alundum v i t r i f i e d w heel on one s id e and a 2" x 14" g r a in 4 4 , g ra d e M Alundum w heel on th e o th e r s id e . 1 The amount of d u st produced by th e o p e ra tio n o f tandem to o l g rin d e rs depends 1 p rim a rily upon th e com position o f th e w heel and the hardness and c h a ra c te r of the o b je c t b ein g ground. T h e o re tic a lly , th e o p eratin g speed and th e p re ssu re should I a ls o be d eterm in in g f a c to r s , b u t th e s e w ere n o t s tu d ie d . The fo llo w in g a r e average d u st co u n ts of p a r tic le s te n microns" o r le s s p e r cubic fo o t in sam ples ta k e n in th e I b r e a th in g zone o f th e p e rso n u s in g th e g rin d e r d u rin g th e g rin d in g o f v a rio u s ob je c ts on v a rio u s w heels o f tandem flo o r g rin d e rs: 1 P a rtic le s per 1 Op e r a t i o n cubic foot 1 G r in d in g C a st I r o n on 2" x 12" A l o x i t e (46M G r i t ) W h e e l . . , . . . . . 1 1 ,6 4 8 ,9 6 0 11 a S te e l S leeve on a l/2 " x 10" Carborundum W heel.. . . . . . 8 ,1 2 7 ,8 4 0 1 h It H ard S t e e l C h is e l on a 5/ 8" x 8 - l / 2 " Alundum W h e e l,, . 7 ,4 7 6 ,4 8 0 n II " " " " 1/ 2" x 10" Carborundum W heel.. 1 ,6 7 0 ,8 8 0 1 II " " " " " 3 /4 " x 10" " .. 906,240 11 II P neum atic T ool S t e e l C h is e l on a 3 - l / 2 " x 14" N o rto n 1 I Alumdum (3836 - 0, 5B) W heel, .................................................. ...... 1 ,8 6 9 ,1 2 0 11 II C h is e l B ar on t h e same w h e e l (3836 - 0. 5B A lum dum )., 4 ,1 3 4 ,7 2 0 1 IS II T ool S te e l C h is e l on a 1" x 10" C arborundum ( G r a in 46m) W h e e l . . . . . . , 2,594,112 1! T ool S te e l on a 2" x 14" Alundum (24 g r a in ,g r a d e Q) Wheel 396,480 it II II II II ^44 II I! H 1,019.520 * 1! a Lathe Tool on a l/2 " x 12" " (G rad e P ) W h e e l.. .3. 3. 9. .,8 4 0 It 11 h it ^ 11 p ^ 11 fi fi 9 fi 9 1 ,3 3 1 ,0 4 0 O peration (C ontinued) P arti les per cubic fo o t G rinding a L a th e T o o l on a 3" x 16" C arborundum ( g r i t 3 0 , g ra d e K) W heel................. M ild S t e e l on a l - l / 2 " x 10" Alundum W heel............................... S t e e l D ies on a 3" x 14" C arborundum W heel................................ S q u a rin g Shear B lades on a l l / 2 " x l6 " Carborundum Wheel. 362,496 6 ,6 5 5 ,2 0 0 56,640 2 ,5 7 7 ,1 2 0 D ust P ro d u ced By Op e r a t i o n o f Tandem F lo o r G r in d e r s . As w ould b e e x p e c te d , th e r e is a w ide v a r ia tio n in th e appearance o f th e d u st p a r tio le s under th e Konim eter m icroscope. These exam ples however, w ill give an id e a o f th e c h a r a c te r is tic s o f th e d u st produced d u rin g th e o p e ra tio n o f Tandem F lo o r G rin d e rsi S M aterial Being Ground S ize of W heel Type o f Wheel C h a ra c te ris tic s of Dust P a rtic le s . (S izes and P ercentages E stim ated) 1" x 3" M ild S te e l Bar 1 -1 /2 " x 10" Alundum (G rit 46, Grade P) About 70$ angular c ry s ta llin e , 6 m ic ro n s o r l e s s i n s iz e ? 30$ me t a l l i c sh red sj 10$ w hite opaque, s l i g h t l y a n g u la r, over 10 m icrons? many sm a ll b la c k specks Tool S teel 2" x 14" Alundum v i t rifie d (G rit 4 4 ,G rade M) About 90$ angular c ry s ta llin e , 2 m icrons or le s s in size? 10$ opaque, 1 m icron or le ss in siz e . Tool S teel (Sam e ma t e r i a l as above) 2" x 14" Alundum v i t rifie d (G rit 24, G rade Q) About 60$ round, sem i-opaque, 10 m icrons or le s s in size? 40$ an g u lar opaque, 5 m icrons o r le s s in size L athe Tool 3" x 16" Carborundum ( G r it 30 Grade K) About 75$ round, c ry s ta llin e , 5 m icrons in size? 25$ s lig h tly a n g u la r. C h isel Bar Pneum atic Hand Tool S teel C hisel 2-1/2 x 14" Alundum (3836-0. 5B) 2- I / 2 " x 14" Alundum (3836-0. 5B) About 70$ s lig h tly angular, 3 m icrons in size? 30$ black, opaque, m etallio . About 98$ round, black, opaque, one m icron or le ss in siz e . Lathe Tool Lathe Tool (Same as above) I - I / 2 " x 12" Alundum (Grade P) I - I / 2" x 12" Alundum (G rade R) About 50$ angular c ry s ta llin e , 2 m icrons or le s s in size? 50$ round, b la c k , m e ta llic , 1 m i cron or le ss in size. About 75$ angular c ry s ta llin e , 2 mioronB o r le s s in s iz e ? 25$ round, b la c k , m e ta llic , 1 m i cron or le s s in size DUST PRODUCED BY TANDEM FLOOR GRINDERS ( C o n c lu d e d ) M a te ria l Being Ground Cast Iron S ize of W heel Type o f Wheel 2" x 12" A loxite (G rit 46, G rade H) C h a ra c te ris tic s o f Dust P a r tic le s . (S iz e s and Percentages E stim ated) About 85$ sh a rp ly a n g u la r, c ry s ta l l i n e , 5 m icrons or le s s j 10$ rounded angular c ry s ta llin e , over 10 m icronsj 5$ opaque s c a le - lik e m e ta llic , 10 m icrons o r le ss} la r g e number o f b la c k m e ta llic specks. Where "hard" w heels a re u sed f o r g rin d in g s o f t c a s t s t e e l , a b o u t 98$ o f th e d u s t p a r t i c l e s a re m e ta llic and le s s th a n o n e -h a lf m icron in size* W ith th e e x c e p tio n o f a v e r y small.^ num ber o f men who d e v o te a b o u t 95$ o f t h e i r w orking tim e to a c tu a l g rin d in g , th e re i s a v e ry wide v a r ia tio n in th e number o f men exposed and th e le n g th o f su ch ex p o su re t o d u s t p ro d u ced by th e o p e r a tio n o f tandem f lo o r to o l g r in d e r s . In only one c a s e was a r e s p i r a t o r worn. G oggles have been provided and th e ir use re q u ire d in most cases B - TANDEM BENCH GRINDERS; T h ese g r i n d e r s a r e s m a ll i n s i z e and a r e u s e d f o r sh arp en in g sm all to o ls and li g h t g rin d in g . They a re a l l m otor d riv e n and o p e ra te a t a b o u t 3400 R ,P .M, D i f f e r e n t g r a d e w h eels a r e u s e d , u s u a l l y l - l / 8 " x 8" C arborundum (G rain #80) on one s id e , and on th e o th e r a 1" x 8" Carborundum (G rain # 9 0 ). The am ount o f d u s t p ro d u c e d b y th e o p e r a t i o n o f ta n d em b e n c h g r i n d e r s v a r i e s w ith t h e ma t e r i a l b eing ground and th e co m p o sitio n of th e wheel, but. th e se average d u st counts are fa irly rep resen tativ e; O peration P articles per cu. ft. G rinding " " " Cold " l/2 " Hard C h isel on l~ l/8 " G rain #80 Carborundum W h e e l.,.. " " 1" x 8" " #90 " " ... B o ile r P la te on 1" x 8"#90 " " .... S te e l C h is e l on 5/8" x 8 ~ l/2 " Alundum ( G r a in 46., G rade P ) ............ .............................. ................ 6 ,9 0 9 ,4 4 0 8 ,4 0 1 ,6 0 0 1 2 ,4 6 0 ,8 0 0 7 ,4 7 6 ,4 8 0 Dust p a r tic le s in sam ples tak en d u rin g th e o p e ra tio n o f th e tandem bench grinder have th e follow ing c h a ra c te ristic s ; M a te ria l Being Ground Size of W heel Medium S t e e l Cold C h is e l l~ l/2"x8" Type o f Wheel Carborundum (#80 G rain) Medium S te e l Cold C h isel ( Same t o o l a s Above) CO K f-- Carborundum (#90 G rain) C h a ra c te ristic s of Dust P a rtic le s . (S izes and P ercentages E stim ated) About 75$ s lig h tly a n g u la r c ry s t a l l i n e , 5 m icrons or le s s in s iz e j 20$ round opaque, m e ta llic , one m icron o r le ss} 5$ sem i opaque, over 10 m icrons and look lik e chips of glass. About 80$ round opaque, 2 m icrons o r le s s in size} 20$ s lig h tly angu l a r c ry s ta llin e , 5 m icrons or le s s in size -4 3 - DUST PRODUCED BY TANDEM BENCH GRINDERS (C o n c lu d e d ! M aterial Being Ground Size of Wheel l/2 " Soft S teel B oiler P la te (Taking o ff rough edges) 1" x 8" Hard S te e l C hisel 5/8" X 8- I / 2" Type of Wheel Carborundum (#90 G rain) Alundum (G rain 46, Grade P) C h a ra c te ristic s of Dust P a rtic le s . (S izes and Percentages E stim ated) About 90$ round, b lack , m e ta llic , 2 m icrons or le ss in size? 10$ s lig h tly angular c ry s ta llin e , 5 m icrons or le ss in s iz e . About 85$ round, b lack opaque, 2 m icrons o r le ss in size? 15$ rounded c r y s ta llin e , 10 m icrons or over. C - SINGLE FLOOR TOOL GRINDERS; T h e re a r e o n ly a few s i n g l e f l o o r g r i n d e r s i n u s e . They ra n g e i n s i z e from 1" x id " m o t o r - d r i v e n (1750 RFM) t o 2 - l / 2 " x 20" b e l t - d r i v e n (1 2 5 0 RFM). The l a r g e r s i z e i s u s e d f o r h e a v y g r in d i n g su ch a s b la n k s and la rg e to o ls? the sm aller sizes fo r sharpening to o ls and m iscellaneous grind in g , The w heel on th e la r g e g rin d e r is Carborundum ($9G G ra in ), For th e s m a lle r s iz e c la s s G rain 46, Grade M Carborundum w heels a re used on th e 1" x 10" and G rain 24, G rad e'Q Alundum w heels in th e l ~ l/ 2 " x 14" s iz e . Sam ples ta k e n d u rin g th e o p e ra tio n of S in g le Floor G rinders had d u st counts as follow s; Op e r a t i o n P a rtic le s per cu, f t . G rinding " " T o o l S te e l on l - l / 2 " x 14" Alundum Wheel (G rain 24, Grade Q ) . ............ C h ise l on 1" x 10" Carborundum Wheel ( G r a in 4 6 , G rad e M ) .................... l / 2 " x 4" M ild S te e l Bar on 2 - l / 2 x 20" Carborundum Wheel (G ra in 9 0 ) , . . . . . . . 679,680 2 ,5 9 4 ,1 1 2 4 ,4 5 1 ,9 0 4 The hoods w hich alm ost com pletely en clo se th e s e wheels a c t as p r a c tic a l d u st c o lle c to rs. Dust p a r tic le s produced by th e fo reg o in g g rin d in g had th e se c h a r a c te r is tic s when examined u n d er th e K onim eter m icroscopes M a te ria l Being Ground Hard S te e l Tool B it Size of Wheel I - I / 2" X 14" Type o f Wheel Alundum (G rain 24, Grade Q) I / 4" x 2" M ild S teel Bar 1" x 10" 1/ 2"x4" M ild S teel Bar 2 - 1 /2 " x20'^ Carborundum (G rain 46, G rad e M) Carborundum! (G rain 90) C h a ra c te ristic s of Dust P a rtic le s , (S izes and P ercen tag es E stim ated ) A ll p a r tic le s were 2 m icrons or le s s in s iz e . About 60$ were an g u lar c ry s ta llin e ? 40$ were rounded opaque. A bout 98$ w ere b la c k opaque, 2 mi crons or le ss in size? 2% s lig h tly a n g u la r,5 m icrons or le s s in siz e . About 85$were s lig h tly angular c r y s ta llin e , 5 m icrons o r le s s in siz e ja b o u t 15$b lack sem i-opaque, an g u lar m e ta llic , 2 m icrons or le ss in size. \ D - UNIVERSAL GRINDERSt As th e name w ould i n d i c a t e , u n i v e r s a l g r i n d e r s a r e jed fo r a w ide v a r ie ty o f p u rp o ses and th e re f o r e a re in more c o n tin u o u s opera ti o n th a n a re th e o th e r g rin d e rs , w ith th e ex cep tio n o f th e tandem f lo o r to o l g rin d ers T h ere a re two ty p e s o r m akes, th e Brown & Sharpe U n iv e rs a l G rin d e r w hich has an o p e r a t i n g sp eed o f 3750 RPM. and t h e G rand R ap id s U n iv e r s a l G r in d e r w h ich o p e r a t e s a t a b o u t 3850 RPM. The f o llo w in g a b r a s i v e w h e e ls a r e used} l/? ." x 5" N o rto n Co. 3846 J 5B Alundum w h eel f o r g r i n d i n g hardened carbon to o l s te e l, 1 /2 " x 7" N o rto n Co. 3846 I 8B Alundum w h eel f o r g r i n d i n g high speed to o l s te e l. - - w ; -- - - 2" x 3 - l / 2 " C arborundum Co. g r i t 4 0 1 -P -2 5 , ty p e 12 A loxite wheel fo r g rin d in g case hardened s te e l. l / 4 " x 10" C arborundum Co. w h eel u sed f o r c u t t i n g . 1" x 10" " " " " to o ls , ream ers, d ie s and d r i l l b its . " sharpening Samples tak en d u rin g the o p e ra tio n of th e v a rio u s U n iv e rs a l g rin d e rs had d u st counts as follows* O peration P a rtic le s per cu. f t. D re s sin g l / 2 " x 7" Alundum (3846 I 8B) Wheel w ith a ''Diamond P o i n t " . .......................................................................... ( E v id e n tly th e c lo u d s o f d u s t w hich come o f f d u rin g d r e s s in g have p a r t i c l e d l a r g e r th a n 30 m ic ro n s) G rin d in g High Speed T ool S te e l on l / 2 " x 7" Alundum Wheel (3 8 4 6 1 8B ) . . . . . . . * . . . . . " H ardened C arbon Tool S t e e l on 1 /2 " x 5 " Alundum Wheel - ( 3846 J 5B ). . . ........................................................... " Case Hardened S te e l on 2" x 3 - l / 2 " A lo x ite ( G r i t 401 - P - 25 Type 2 ) . . . . . . . .......... C u ttin g o f f Tool S te e l w ith l / 4 " ?x 10" Carborundum W heel,., 1 ,3 9 7 ,1 2 0 1 ,8 4 6 ,4 6 4 6 ,6 8 3 ,5 2 0 84,960 1 ,4 1 6 ,0 0 0 D ust p a rtic le s in sam ples tak en du rin g th e o p e ra tio n o f U n iv ersal g rin d ers have th ese c h a ra c te ristic s * M a te ria l Being Ground Size of Wheel Type o f Wheel D re ssin g Wheel l/2 " x 7" W ith a "Diamond P o in t" Alundum (3846 I 8B) High Speed j Tool S te e l (a L andis Pipe C haser) 1 /2" x 7 " Alundum (3846 I 8B) C h a ra c te ristic s of Dust P a rtic le s (S izes and P ercen tag es E stim ated ) About 80$ s lig h tly angular cry s ta llin e , About 3 m icrons in siz e j 20$ b lack opaque, round, about 1 m icron or le s s in size About 60$ opaque an g u lar, about 2 m icrons or le ss in s iz e j 40$ s lig h tly angular, c ry s ta llin e , 5 m icrons or over in s iz e . -4 5 - < Dust p a r tic le s in sam ples ta k en d u rin g th e o p e ra tio n o f U n iv ersal g rin d e rs Aave th e s e c h a r a c t e r i s t i c s (C o n tin u ed )? M a te ria l Being Ground Hardened Car bonated S tee l (P ip e G rip fo r P ip e M achine) Size of Wheel I / 2" x 5" Type o f Wheel Alundum (3846 J 5B) Case Hardened S te e l (Plung ers for F ill in g Machine) 2" x 3- I / 2" A lo x ite ( G r i t 4 0 1 -P-^ 25 Type 12) C h a ra c te ris tic s of Dust P a rtic le s . (S izes and Percentages E stim ated) About ZO% angular c ry s ta llin e , about 2 m icrons or le s s in siz e j 10% round b la ck opaque, le s s th an 1 m icro n in s iz e . Numerous b la c k specks too sm all to count. Several la rg e oblong b la c k opaque p ar t i c l e s ab o u t 20 m icrons wide and 35 o r 40 m icro n s long A ll p a r t i c l e s b la c k o paque,' 1 mi cron o r le s s in size E - SURFACE GRINDERS? S u r f a c e g r i n d e r s a r e u s e d a lm o s t e x c l u s i v e l y on v a l v e s and dies They a r e eq u ip p ed w ith e i t h e r l / 2 " x 8" N o rto n Alundum (1946H) w heels o r l / 2 " x 4" t o 6" C arborundum ( A l o x i t e ) w h e e ls. No d u s t c o l l e c t o r s a r e p r o v id e d , t h e d u st being throw n out in to th e atm osphere. - Samples ta k e n d u rin g th e o p e ra tio n of su rfa c e g rin d e rs had th e fo llo w in g d u st c o n c e n tra tio n (10 m icrons or le s s ) i Op e r a t i o n P a rtic le s per cu, f t. G rinding S o ft C ast S te e l V alve on l/2 " x 6" Carborundum A lo x ite W heel. " T o o l S te e l D ie on l / 2 " x 8" Alundum (1946H) D re ssin g S u rfa c e o f l / 2 " x 8" Alundum Wheel w ith a "Diamond PA! Tp{-^ A V / A J. 1 U * 566,400 1 ,0 1 9 ,5 2 0 1 ,1 3 2 ,8 0 0 A bout 10%, o f t h e p a r t i c l e s from g r i n d i n g t h e s t e e l d i e w ere m e t a l l i c , 3 m i c r o n s o r l e s s , w h e re a s 98?S o f t h e p a r t i c l e s from g r i n d i n g t h e s o f t s t e e l v a lv e w ere m e t a l l i c . Many o f th e p a r t i c l e s w ere to o s m a ll t o i d e n t i f y o r c o u n t a c c u r a te ly . F - LANDIS TOOL GRINDERS? L a n d is t o o l g r i n d e r s a r e u s u a l l y e q u ip p e d w ith tw o d iffe re n t ty p es o f w heels, one fo r sid e grin d in g and th e o th e r th e o rd in ary type, l - l / 2 " x 12" Carborundum A lo x it e ( G r it 40, G rade H, Bond 33) i s vised fo r g e n e ra l p u rp o se g rin d in g such a s b u l l c h i s e l s , diamond p o in ts , c o ld c h i s e l s , fla n g e s and s c ra p p e rs . The S ide G rin d in g Type i s u s u a lly a 2 - l/ 2 " x 1 -1 /2 " x 12" G r it 46A-P P678 A lo x it e b r a n d AA w h e e l u s e d f o r g r i n d i n g L a n d is d i e s . A t one p l a n t th e w h eels o f th e Landis to o l g rin d e r a re en clo sed by hoods a t th e re a r o f each o f w hich is a tta c h e d a tw o -in ch p ip e co n n ected to a th re e -in c h p ip e which d isc h a rg e s in to a sew er. S uction is induced by a stream of com pressed a i r from a h a lf-in c h pipe in s e rte d in th e tw o-inch p ip e ju s t back of th e hand. This arrangem ent a c ts as a sy phon and p u lls th e d u st away from th e p erso n u sin g th e g rin d er Samples ta k e n d u r'/ing th e o p e ra tio n o f L an d is to o l g rin d e rs had d u s t c o n c e n tra tio n s as follow s? -4 6 - Op e r a t i o n P a rtic le s per cu, f t. D re a s in g l - l / 2 " x 12" A lo x it e W heel ( G r it 4 0 , G rad e H, Bond 3 3 ) , ............................... .. (E v id en tly p a r tic le s in th e cloud of d u st throw n o ff by th e 2 -1 /2 " x 6" M e tc a lf Emery Wheel D re s se r a r e la r g e r th a n 30 m icrons in s iz e ) G rin d in g "Diamond P o in t" C h ise l on l - l / 2 " x 12" A lo x ite Wheel ( G r i t 4 0 , G rade H )............................................................................................... G rinding 2 -l/2 " x 6" Landis d ie on 2 ~ l/2 "'X l - l / 2 " x 12" A l o x i t e W heel ( G r i t 46A-P P 6 7 8 )..................... .......................................... 226,560 2 ,0 6 7 ,3 6 0 755,203 Under th e K onim eter m icroscope d ust p a r tic le s in sam ples ta k e n w h ile d re s s in g th e l - l / 2 " x 12" A lo x ite Wheel appeared s l i g h t l y angxilar w ith a y e llo w is h tin g e and were fiv e m icrons o r le s s in siz e . About 15% o f th e p a rtic le s from g rin d in g th e L a n d is d i e w ere ro u n d , o p aq u e, an d l q s s th a n 1 m ic ro n i n s i z e j 25%> w ere s l i g h t l y a n g u la r c r y s t a l l i n e , le s s th a n 2 m icrons. P a r t i c l e s from g rin d in g th e diamond p o in t c h is e l were le s s q u a rtz -lik e th an th o se from g rin d in g th e die. T his d iffe re n c e i s , o f c o u r s e , due t o d i f f e r e n c e i n t h e c o m p o s itio n o f t h e tw o w h e e ls . On a n a v e r a g e , L andis to o l g rin d e rs a r e used ab o u t tw enty hours a week, u s u a lly by d i f f e r e n t men, G -- YANKEE DRILL GRINDER; U sed f o r g r i n d i n g a l l ty p e s o f d r i l l b i t s . Has a s i d e g r in d i n g ty p e 1" x 1 - 1 /2 " x 9" Carborundum A l o x i t e ( G r i t 3 0 , G rade M, Bond 2 8 ) W heel, O p e r a tin g sp e e d 1735 RR1, On a n a v e ra g e a Y ankee D r i l l G r in d e r r u n s a b o u t th r e e hours a day and is used by fo u r d iffe re n t men w ith an average s e rv ic e of tw elve years. Samples ta k en d u rin g th e g rin d in g o f a 2 -5 /1 6 " high speed d r i l l had an ave rag e of 1,000,829 p a r tic le s , te n m icrons or le s s , p er cubic fo o t. About 10% of th e se d u st p a rtic le s a re s lig h tly c r y s ta llin e in appearance, fiv e m icrons or le s s " in s iz e j ZO% w ere rounded, sem i-o p aq u e, over te n m icrons in s iz e . T here w ere a ls o a few s m a ll m e t a l l i c s h r e d s . No e x h a u s t o r d u s t c o l l e c t o r i s u se d i n t h i s g r in d i n g . H - AUTOMATIC CIRCULAR SAW SHARPENING MACHINE; T h e re a r e a num ber o f t h e s e g r in d e r s i n use in th e wood w o rk in g o p e ra tio n s - su c h as in th e p r o d u c tio n o f wooden b a rre ls , boxes and c ra te s - c lo se ly asso ciated w ith th e re fin in g of petroleum pro d u cts, Since th ey a re au to m atic when once p u t in o p e ra tio n , th e re is v ery l i t t l e d u st hazard except w here no ex h au st or dust c o lle c to r s have been in s ta lle d and th e d u s t p ro d u ced i s th ro w n i n t o th e f i l i n g room a tm o s p h e re . A u to m a tic C i r c u l a r Saw S h a rp e n in g M achines a r e eq u ip p ed w ith l/ 4 " x 8" N o rto n Alundum W heels (G ra in 60, G rade N ), 3 /8 " x 8" N o r to n Alundum (1946 M) w h e e ls , o r l / 2 " x 6" C arborundum w h e e ls . The av erag e d u st pro d u ced d u rin g o p e ra tio n o f th e s e m achines i s ; Wheel P a rtic le s per cu, ft. l / 2 " x 6" C arborundum . ........................ 1/4" x 12" " .................................... 3 /8 " x 8" Alundum (1946M ). ............ ............ l/4 " x 8" " ( G r a in 6 0 , G rade N) .. 1,923,280 . . 3,568,320 .. 2,095,680 1 ,4 6 1 ,3 1 2 A bout 98% o f d u s t p a r ti c le s in sam ples ta k e n w h ile sh arp en in g c ir c u la r saws on th e Carborundum w heels were b lack m e ta llic in ap p earan ce, and one m icron o r le s s i n s i z e . A bout 75%> o f t h e p a r t i c l e s from t h e A lundum w h e e ls w ere ro u n d e d c r y s t a l l i n e , 6 m icrons o r under in s iz e , and 25% round b la ck m e ta llic , about one m icron or le s s in s iz e . There w ere a number o f sm all m e ta llic sh red s in th e sam ples from th e th ic k e r ( 3/ 8" x 8 ") w heel. I -- AUTOMATIC BAND SAW GRINDER; A f te r t h e Band Saw h a s b e e n i n s e r t e d and t h e -4 7 - m achine a d ju s te d , t h i s g rin d e r works a u to m a tic a lly . The wheel o r d in a r ily used i s a l / 2 " x 8" G r a in 5 0 , G rade N N o rto n Company Alundum. The w heel i s r e f a c e d o r d r e s s e d w ith a H e tc a lf Emery Wheel D re sse r a b o u t tw ic e a day. The av erag e d u s t produced by th is d re ssin g o p e ra tio n is 2,284,480 p a r tic le s le s s th a n te n m icrons per cubic fo o t. About 95$ o f th e s e d u st p a r tic le s are s h a rp ly an g u lar c r y s ta llin e in appearance under th e K onim eter m icroscope, and about fiv e m icrons or le s s in s iz e . The d u st produced d u rin g th e s h a rp e n in g or g rin d in g o f th e b an d saw b la d e i s on a n a v e ra g e only 877,920 p a r tic le s p er cubic fo o t. About 50$ o f th e se p a r tic le s appear a n g u la r c r y s t a l l i n e and ab o u t 50$ round b la c k opaque A ll o f them a re ab o u t two m icrons or le s s in Size, J - AUTOMATIC BAND SAW LAP GRINDERt Used t o g r in d ends o f band saw p r e p a r a t o r y t o w e ld in g them t o g e t h e r . The g r in d in g w h eel u s u a ll y u sed i s 5 /8 " x 10" G ra in 4 6 , G rade M, N o rto n Company Alundum, No d u s t c o l l e c t o r i s p ro v id e d a l th o u g h a d u s t co u n t as h ig h a s 1 6 ,1 4 2 ,4 0 0 p a r t i c l e s , t e n m icro n s o r l e s s , was found i n one sam ple ta k e n in f r o n t o f th e w heel w hile i t was i n o p e ra tio n . The av erag e d u s t produced by th is la p g rin d e r was 4,9 8 4 ,3 2 0 p a r t i c l e s per cu b ic fo o t. About 80$ o f th e s e d u st p a r t i c l e s w ere sem i-opaque, s l i g h t l y a n g u la r i n a p p e a ra n c e , and two m icro n s or l e s s in s iz e j 20$ w ere b lack opaque, about one m icron or le ss in siz e . K - PLANING KNIFE BIADE GRINDERt U se s a l / 2 " x 8" G rain 4 6 , G rade N, N o rto n Company Alundum w h e e l. O p e r a tin g sp e e d 3000 RPM, No hood o r an y o t h e r p r o t e c t i o n . A verage d u s t p ro d u ced w h ile s h a rp e n in g a P la n e r K n ife B lad e was 5 6 6 ,4 0 0 p a r t i c l e s , te n m icrons o r le s s p er cubic fo o t. About 60$ o f th e s e d u st p a r tic le s were s l i g h t l y a n g u la r c r y s t a l l i n e in ap p ea ran ce and a b o u t two m icro n s or le s s in s i z e j 40$ w ere opaque o f v a rio u s s iz e s from ab o u t seven m icro n s o r l e s s . There w ere a few sm a ll m etallic shreds. L - LINDERMAN CUTTER GRINDER; S h a rp e n s c u t t e r s from th e L in d erm an m a ch in e f o r to n g u e in g and g ro o v in g . G rin d e r u se s a l / 2 " x 6" N orton Alundum (G ra in 6 0 ,Grade N) cup w h eel. O p e r a tin g s p e e d 3000 RPM. T h e re i s a hood g u ard o v e r t h e t o p o f t h e g rin d in g w heel, b u t no exh au st or d u st c o lle c to r, alth o u g h dust counts as high as 14,386,560 p a r tic le s , te n m icrons or le s s , were found a t the fro n t o f th e g rin d e r in | o p e ra tio n , and 12,57 4 ,0 8 0 p a r tic le s per cu b ic fo o t in th e back. The av erag e d u st produced was 9 ,1 3 7 ,9 2 0 p a r t i c l e s p e r c u b ic fo o t. A bout 70$ o f th e s e d u s t p a r t i c l e s | a re round sem i-opaque i n ap p earan ce u n d er th e K onim eter m icroscope, and th r e e mi crons or le s s in siz e j 20$ a re round, g lo b u lar lik e p a rtic le s , seven m icrons or le ss | in s iz e j and 10$ a re m e ta llic shreds ab o u t two m icro n s wide and 20 to 30 m icrons long. T here a re many m inute c r y s t a l l i n e p a r t i c l e s to o sm all and too numerous to count ao- g c u ra te ly . | M GANG SAW BLADE GRINDER; U ses a 5 /8 " x 10" G r a in 50, G rade M, N o rto n Company A1undrum w h e e l, o p e r a t i n g a t 1800 RPM, A r a t h e r c ru d e d u s t c o l l e c t o r h a s | been in s ta lle d , b u t th e average dust (8,760,320 p a r tic le s per cubic fo o t) produced by th is g rin d er in o p eratio n in d ic a te s th a t i t is inadequate. About 90$ of the | d u s t p a r t i c l e s i n s a m p le s ta k e n d u r in g t h e g r in d i n g o f a Gang Saw B la d e w ere semi opaque in ap p ea ran ce and a b o u t two m icrons o r l e s s in s i z e j 10$ w ere b la c k round, 1 opaque, one m icron o r le s s in s iz e . There w ere numerous m inute b la c k specks to o sm all to count acc u ra te ly . 1 N EDGER SAW GRINDER; Uses a 3/ 8" x 8" G r a in 6 0 , G rade N, N o rto n Company | . Alundum w h e e l, o p e r a t i n g a t 1650 RPM, No h o o d o r a n y o t h e r d u s t c o l l e c t o r f o r t h i s g rin d e r, The low d u st c o u n t, an av erag e o f only 4 5 3,120 p a r tic le s , te n m icrons o r le s s Per cub ic fo o t, in d ic a te s th a t th e re is very l i t t l e re a l need fo r such equip m ent. The d u s t p a r t i c l e s p ro d u c e d w h ile g r i n d i n g a n E d g e r Saw B la d e a r e a n g u l a r | c r y s t a l l i n e , a b o u t two m icro n s or le s s in s iz e . 0 - CIRCULAR SLAB CUT-OFF SAW GRINDER; U ses a 3 /4 " x 10" G ra in N. N o rto n -4 8 - Company Alundum w h eel o p e r a t i n g a t 1650 RFM, A r a t h e r i n e f f e c t i v e d u s t c o l l e c o r as Ibeen in s t a l l e d , b u t th e av erag e h ig h d u s t c o n c e n tra tio n (1 0 ,9 3 1 ,5 2 1 p a r ti c le s per -o u b ic f o o t) shows t h a t i t i s in a d e q u a te . About 80% o f th e d u s t p a r t i c l e s in samp es ta k e n d u r in g t h e s h a r p e n in g o f a C i r c u l a r S la b C u t - o f f Saw w ere^ o p aq u e i n a p p e a ra n c e , two m icro n s or le s s in s iz e j 20% w ere s l i g h t l y a n g u la r c r y s t a l l i n e , f iv e m icrons or le s s in s iz e . There were a lso a la rg e number o f m in u te b lack opaque p a r tic le s . P - "HOG KNIFE" GRINDER; U ses a 1 - 1 /2 " x 24" Carborundum w h e e l o p e r a t in g a t 300 RFM. T h is g r i n d e r i s c o m p le te ly e n c lo s e d b y a m e ta l h o o d , b u t th e d u s t $.s d i s charged o n to th e flo o r th ro u g h an opening in th e low er p a rt of th e hood. The average d u st produced by th e o p e ra tio n of t h i s g rin d er is 1,869,120 p a r tic le s p er cubic fo o t. About 75% of th e se dust p a r tic le s were an g u la r c r y s ta llin e in appearance under t h e K o n im e te r m ic ro s c o p e an d f o u r m ic r o n s o r l e s s i n s i z e j Z5%> w e re ro u n d , b la c k opaque, two m iorons or le s s in s iz e . Q - CUTTER GRINDER;*. U ses a 3 - l / 2 " x 2 - l / 2 " x l / 2 " N o rto n Alundum w h e e l (3846 K B 5 ). The amount of d u st produced depends upon th e m a te ria l b ein g ground as is shown by th e fo llo w in g ; * I I G rinding a s te e l counter sink. ............ .. 7 3 6 ,3 2 0 p a r t i c l e s p e r c u , f t . " " " ream er.. . . . . . ............ .1 ,0 1 9 ,5 2 0 " " " I The d u s t p a r t i c l e s a re a b o u t 98/. opaque m e ta llic in ap p earan ce and ab o u t one m icron or less in size. I W hat P r e c a u tio n s S h o u ld Be A d o p te d F o r S a f e g u a r d in g T h o se Who Use G r in d in g J/h eels? A u th o r it ie s g e n e r a lly a g r e e ( Jo u r. In d u st Hyg. Vol, V II No. 8 A ugust 1925 I p. 351) t h a t w o rk e rs who h a b i t u a l l y u s e g r in d i n g w h e e ls w i l l r u n b u t s l i g h t r i s k o f dev elo p in g pneum oconiosis i f th e y u se c e r t if ie d a b ra siv e r a th e r th a n san d sto n e w heels I f o r a l l g rin d in g o p e ra tio n s and i f th e m achines upon which th e a r t i f i c i a l a b ra siv e w heels a re mounted a re p ro p e rly hooded and e x c e ss iv e d u st removed by s u c tio n . I C o n tro l o f D ust From G rin d in g , P o lis h in g and B u ffin g W heels. E x h au st system s 8 fo r g rin d in g , p o lish in g and b u ffin g w heels v a ry w id ely in d esig n . In th e case of g rin d in g , th e hoods used serve n o t o n ly to p ro v id e means f o r c a p tu rin g th e d u st b u t 8 a ls o a c t to 'p ro te c t th e w orker in c a s e th e w heel b u r s ts . The c h ie f d i f f i c u l t y to be overcom e i n g r in d i n g w h e e ls , .a c c o r d in g t o U. S. P u b lic H e a lth B u l l e t i n No. 217, "The 1 D eterm in atio n and C ontrol of I n d u s tr ia l Dust" (1 9 3 5 ), is th e outw ard sweep o f a i r , a fan a c tio n , due to th e rev o lv in g w heel. T his e f f e c t is v ery marked w ith h igh speed I and rough w heels and i s so s tro n g t h a t i n many in s ta n c e s i t is s u f f i c i e n t to c o u n te r a c t th e norm al inw ard flo w o f a i r . The same e f f e c t e x is ts w ith p o lis h in g and b u ffin g 1 w heels b u t to a le s s marked d eg ree. X P r a c tic a lly a l l in d u s tr ia l S ta te s have codes re g u la tin g th e c o n s tru c tio n and d u s t co n n ectio n s fo r g rin d in g , p o lis h in g and b u ffin g wheels. They a lso r e g u la te th e 1 a i r re q u ire d fo r w heels o f v a rio u s s iz e s in term s o f s ta t ic s u c tio n in th e connect in g d u c ts. These codes p o sse ss no u n ifo rm ity . However, th e re q u ire m e n ts d e s ig n a t I ed by S ta te codes must be follow ed. I n S ta te s w here no codes have been adopted i t is d e s ira b le to pro v id e ex h au sts on a l l g rin d in g w heels w ith a s u c tio n a t th e con s n e c tio n t o th e hood s u f f i c i e n t t o p ro d u ce a d i f f e r e n c e o f le v e l o f a t l e a s t two in c h e s o f w a te r betw een th e two s id e s o f a U -shaped tu b e . 1 J f A number of th e w heels have been provided w ith su c tio n exhaust produced by a I m otor d riv e n fan or a hood, w ith a tw o -in ch p ip e one end o f which is immersed in a b u c k e t o f w a te r. The d u s t is draw n i n b y th e r a p id r e v o lu tio n o f th e w h eels (1750 x RPM). T h is s im p le a rra n g e m e n t i s p a r t i c u l a r l y e f f e c t i v e . T h ree s a m p le s ta k e n n e a r th e d isch arg e of a m otor d riv en s u c tio n fan connected w ith th e hood o f l - l / 2 " x 10" -4 9 - Alundum ( G r i t 4 6 , Grade P) w h eel w h ile a t o o l was b e i n g s h a rp e n e d h ad a n a v e ra g e o f , 2 ,0 7 6 ,9 8 9 p a r ti c le s p er cu b ic fo o t w hich would have o th e rw ise been throw n in to th e |5, / m a c h in e shop a tm o sp h e re , As p o in t e d o u t b y Dr. W, I r v i n g C la r k i n h i s p a p e r "D u st H a z a rd s and t h e P re v e n tio n o f I n ju r y from th e Same" r e a d a t a m e etin g o f G overnm ent O f f i c i a l s in In d u s t r y a t B o s to n , H ass, on May 21, 1 9 3 1 , t h e m o st e f f e c t i v e m eth o d o f rem o v in g f i n e p a r tic le s o f d u st is by s u c tio n a p p lie d as c lo se as p o s s ib le to th e p o in t where th ey a re g en erated and th e amount o f th i s s u c tio n is g re a t enough to overcome th e d is p e rs in g a c tio n upon th e d u st o f th e work b e in g done. The v e lo c ity a t th e a i r d u c ts o f an e f f ic ie n t d u st rem oving tu b e should be 1500 lin e a r f e e t p er m inute. Q uoting Dr. C la rk ; "No m a t t e r how w e ll a workman i s p r o te c te d h e s h o u ld b e k e p t u n d e r m edical su p erv isio n and have a p erio d ic exam ination o f h is h e a rt and lu n g s. I n a d d itio n , th e X -ra y should be employed f r e e ly in o r d e r t o d e t e c t e a r l y s ig n s o f f i b r o s i s in t h e lu n g s and t o show a r y s ig n s o f e a r l y p u lm o n ary t u b e r c u l o s i s . I n my e x p e r ie n c e w ith w orkers exposed to inorganic d u st, n o n -silico u s in c h a ra c te r, a y e a rly p h y sical exam ination w ith an X-ray every second year a f te r te n y e a rs exposure is s u f f i c i e n t b u t i t m ust be remembered th a t th i s is th e r e s u l t o f work in a fa c to ry w here th e c h a ra c te r o f th e d u s t is r e l a t i v e l y h arm less and where e x c e lle n t d u s t remov in g d ev ices a re in s ta lle d on ev e ry machine where i t is p o ssib le . Where f r e e s i l i c a i s p r e s e n t in la r g e q u a n t iti e s th e ex am in atio n s sh o u ld b eg in a f t e r two o r th r e e y e a rs ex p o su re and an X -ray should be taken every year. Dr. C la r k a l s o s t a t e s t h a t men who a r e a s th m a ti c , who s u f f e r from c h ro n ic b r o n c h i t i s , o r who h a v e h a d p u lm o n ary t u b e r c u l o s i s s h o u ld n o t work a t a d u s ty jo b . VII - HANDLING POWDERED OR PULVERIZED MATERIAL A la rg e amount o f powdered or p u lv e riz e d m a te ria ls are used in th e tre a tm e n t o f petroleum pro d u cts and b o ile r w ater and in th e m anufacture of g reases and in se c tic id e s . In m ost cases approved re s p ira to ry p ro te c tio n is provided and i t s use re q u ired when h an d lin g th e m a te ria ls . Exposure to d u st i s u su a lly in te rm itte n t and of s h o r t d u r a tio n . Anong th e pow dered o r p u lv e riz e d m a te r ia ls used in th e r e f in in g of petroleum products and a s s o c ia te d a c t i v i t i e s are A - LIME; Lime i s e x t e n s i v e l y u s e d i n t h e h y d ra te d form and t o a muoh l e s s e r de gree as Im p quicklim e, 1 Hy d r a t e d L im e; Used i n t h e p r e p a r a t i o n o f lim e s o a p g r e a s e an d t h e manu fa c tu re of p re ssu re gun and cup g reasej a ls o in th e treatm en t o f b o ile r feedw ater to " so fte n it " . I t comes in f i f t y pound paper bags by r a ilr o a d , u su a l ly abo u t 1,000 bags to a c a r. A ccording to a chem ical a n a ly sis of a ty p ic a l sam ple, hydrated lim e c o n ta in s; FegOgAlgOg, GaO, o & a O a 30 p e r c e n t. o 73* 64 I t fl MgO, . . . . . . . . . . . . . . . * * 0 93 IT 11 Insoluble S ilic a v V R esidue. . . . . 1*01 It 11 (Rem ainder m o stly M oisture and V o la tile M atter) From 150 to 350 pounds o f lim e a r e used p e r b a tc h in th e m a n u fa c tu re o f g re a s e s . -5 0 - The sack s o f lim e a r e u s u a lly opened and dumped i n t o th e m ix in g k e t t l e . Con; sid e ra b le dust (as h ig h as 34,890,240 p a rtic le s le s s th an te n m icrons per cuy b ic fo o t in one sam ple) is produced by th is o p e ra tio n . The a v era g e d u st pro duced i s 4,733,305 p a r tic le s per cubic fo o t and th e average exposure per b atch i s a b o u t f iv e m in u te s . The number o f b a tc h e s made p e r week v a r i e s from one t o tw e n t y - f i v e . No r e s p i r a t o r s a r e worn by men dum ping h y d r a te d li m e a t any o f th e p o in ts where i t i s used w ith th e ex cep tio n o f B aton Rouge w here th e wear in g o f t h e MSA "Comfo" r e s p i r a t o r i s r e q u ir e d . A b o u t 85% o f t h e d u s t p a r t i c l e s i n sam ples ta k e n w h ile dumping lim e in m ixing k e t t l e s a re s l i g h t l y an g u la r, s lig h tly opaque, c r y s ta llin e , in appearance under th e K onim eter m icroscope,and fiv e m icrons or le s s in size} 15% are rounded, sem i-opaque, w ith a m e ta llic g rey ish color, te n m icrons or over. There a re a lso a c o u n tle ss number o f very sm all p a rtic le s. Only a sm a ll q u a n t ity of H y d rated Lime i s u se d i n th e tr e a tm e n t o f b o i l e r feed w ater. About 70 pounds o f lim e is mixed p er b a tc h and a b o u t s ix b a tc h e s a r e made every day (24 h o u rs). The m ixing is done by one man on each s h i f t . A lth o u g h th e e x p o su re i s v e ry s h o r t , th e men a t I n g l e s i d e R e f in e r y w ear W ills o n " D u s t- tite " r e s p ir a t o r s w hile dumping lim e. The av era g e d u s t produced d u rin g th i s o p e ra tio n is only 657,024 p a r tic le s , te n m icrons or l e s s , p e r cubic fo o t. T his low d u st c o n c e n tra tio n is th e r e s u lt of a s p ra y o f w a te r from a two in ch p ip e acro ss th e h a tc h o f the m iking tank ju s t below th e opening w hile sacks are b e in g dumped. C o n seq u en tly , th e m a te r ia l is w et a lm o st a s soon a s th e lim e is in troduced. About 95% o f the d u st p a rtic le s in sam ples ta k en w hile th e lim e was b e in g dumped in to th e m ixing ta n k were se m i-a n g u la r c r y s t a l l i n e in a p p e a r a n c e , and from f iv e m icro n s or l e s s in s iz e , and 5 % w ere ro u n d opaque, two m iorons or less in siz e . 2. Lump Q u ick lim e? U sed t o " s o f t e n " b o i l e r f e e d w a te r . The lim e u sed f o r t h i s p u rp o s e i s O y s te r S h e l l Lump Q u ic k lim e {91% CaO), I t comes i n f i f t y pound p a p e r - lin e d b u r la p b a g s , and e i g h t bags a re u s u a l l y used p e r b a tc h . One b a tc h i s made p e r s h i f t . The dumping and m ixing r e q u ir e s about t e n m in u tes p e r b a tc h , and th e man d o in g t h i s work i s p r o te c te d by r u b b e r ty p e g o g g le s , b u t no r e s p i r a t o r , The a v e ra g e d u s t produced by h an d lin g t h e b ag s o f lum p O y ster S h e ll Q uicklim e is 2,605,440 p a r tic le s per cubic fo o t. The average d u s t produced w h ile dumping th e b a g s o f lump O y ste r S h e ll Q u ic k lim e i n t o t h e m ix in g ta n k is 294,528 p a r tic le s , le s s than te n m icrons, per c u b ic fo o t. The h an d lin g and dumping o f t h i s Clyster S h e ll Quifiklim e produoes l e s s d u st th a n i s produced by t h e h y d r a te d lim e u s u a l l y u sed . About 95%, o f t h e d u s t p a r t i c l e s in s a m p le s ta k e n during th e dumping of O yster S h ell Q uicklim e in to th e m ix in g k e t t l e ap pear s lig h tly a n g u lar, c ry s ta llin e under the K onim eter m icroscope, and a re fiv e m io ro n s o r l e s s i n s i z e 2%, a r e ro u n d , s e m i-o p a q u e , o v er t e n m ic ro n s i n s i z e j an d 5%, a r e b la c k o p aq u e s c a l e - l i k e , f i v e m ic ro n s o r l e s s i n size What Phy s i l o g i c a l E f f e c t i s Produced b y Lim e D u st? A c c o rd in g t o t h e I n t e r n a t i o n a l L abor O f f i c e (O c c u p a tio n and H e a lth , Vol I I , 1 9 3 4 ) p a r t i c l e s o f lim e m ix w ith th e sw eat o f workmen h a n d lin g i t and i r r i t a t e th e unoovered p o res o f th e sk in } l e s i o n s o f t h e m uoous m em branes a r e a l s o s e t up. We a r e t o l d t h a t ; "The a c tio n o f q u ick lim e is due p a r tl y t o i t s a v id ity f o r w ater (d eh y d ratio n ), to th e h eat given o ff in i t s re a c tio n w ith w ater, and p a r tly to th e p e c u lia r c a u s tic ity o f th e a lk a lin e oxides or a lk a lin e e a rth s . Q uicklim e ex erts e s s e n tia lly a lo c a l a c tio n (on th e s k in and mucous membranes) i r r i t a t i n g and c a u s tic , w hich i s n a tu r a lly le s s marked in th e c a se o f sla k e d lim e. M ilk o f lim e is a f e e b le c a u s tic a c tin g only on th e mucous membranes. The d i l u t e ly e s are only c a u s tic to th e s k in a f t e r p ro lo n g ed ac tio n and e s p e c ia lly when th e y are warn. -5 1 - "In p ra c tic e i t is th e dust of quicklim e and slak ed lim e, given o f f in th e co u rse o f m anufacture and m a n ip u la tio n , which g ives r i s e to th e w ell known le s io n s . T his very fin e d u st i s d e p o s it ed r e a d i l y on t h e mucous membranes and s k in . When in h a le d i t may p e n e t r a t e as f a r as th e r e s p i r a t o r y t r a c t . " A lthough lim e has a tendency to i r r i t a t e th e mucous membranes o f th e r e s p ir a to ry t r a c t , i t is n o t co n sid ered p a r tic u la r ly hazardous when b reath ed in sm all q u a n t i t i e s a t i n t e r m i t t e n t i n t e r v a l s . H ow ever, c o m p lic a tio n s may r e s u l t when a la rg e amount o f th e d u st i s b re a th e d more o r le s s r e g u la r ly . T h ere fo re , i t is d e s i r a b l e t o w ear an a p p ro v e d r e s p i r a t o r s u c h a s t h e MSA "Comfo11 o r t h e W ills o n "D ust-tite". B - METALLIC ZINC DUST? M e ta l li c z in c d u s t (90% th r o u g h .300 m esh) i s a n im p o r ta n t c o n s titu e n t in P ip e T hread C o atin g Compound. A bout 1500 pounds o f t h i s m a te r ia l i s used p er b a tc h , and a b o u t f i f t y b a tc h e s a re made p e r m onth. The z in c d u s t comes i n 400 pound wooden kegs o r 500 pound s te e l drums. A ccording to a chem ical a n a ly s is , t h i s zin c d u s t i s 99. 20%m e ta ll ic z in c and 0 ,8 0 ^ zin o o x id e (ZnO). The p a r t i c l e s iz e d is tr ib u tio n of a ty p ic a l sam ple as determ ined by a sta n d a rd screen a n a ly sis is t A ll through 120 mesh sc re e n 3 76% r e t a i n e d 2.04^ " 22.24$ " on 200 mesh " 250 " " 325 " The zinc d u s t i s dumped from th e keg or drum o n to a m e ta l s h e e t in f r o n t o f th e k e t t l e and s h o v e le d in to th e k e t t l e b y two o r t h r e e men ( w ith an av e ra g e s e r v ic e o f /about th re e m onths) from th e G eneral Labor D epartm ent. T his is a very d u sty opera t i o n . One sa m p le ta k e n d u r in g th e s h o v e li n g o f z in c d u s t h ad a s h ig h a s 6 8 ,7 6 0 ,9 6 0 p a rtic le s p er cubic fo o t of a i r th e average c o n c e n tra tio n b ein g 28,331,328 p ar t i c l e s , l e s s th a n te n m ic ro n s, per cu b ic fo o t. The workmen a re exposed to t h i s d u s t a b o u t t h i r t y m in u tes p e r b a tc h or ap p ro x im a te ly 2 ~ l/2 h o u rs p er month. They w ear d u st r e s p ir a to r s . About 95% o f th e se d u st p a r t i c l e s a r e d ark g rey , opaque, an g u la r in appearance under th e K onim eter m icroscope, and about f iv e m icrons o r le s s in s iz e ; 5% ap p ea r s l i g h t l y a n g u la r, c r y s ta l lin e , te n m icro n s o r le s s in s iz e . The c r y s ta llin e m a te ria l i s probably zin c oxide. What P h y s io lo g ic a l E f f e c t i s Produoed by Zinc D u st? A lthough z in c o x id e (ZnO) produces d e f in i te p h y s io lo g ic a l e f f e c ts , m e ta llic zin c d u s t does n o t seem to a f f e o t th e p erso n b re a th in g i t o th e r th an th a t cau sed by th e in h a la tio n o f any i n e r t d u s t. N e v e rth e le s s some in v e s t ig a t o r s a re o f th e o p in io n t h a t zino i s n o t e n t i r e l y i n e r t and harm less. C e rta in ly i t is not as harm ful as lead o r a rs e n ic , b u t th e U nited S ta te s P ublic H ealth S erv ice has c e rta in lim ita tio n s on th e amount o f zino th a t is p e r m itte d i n d r in k in g w a te r. A ccording t o Nuck, E, Remy, an d F. F o ltzm an n ( J o u r . I n d u s t, Hyg. , V o l . 1 2 , 19 3 0 , p a g e 171 Ab, ) Z in c d u s t c a n c a u s e lu n g t r o u b l e a f t e r b ein g in h aled in la rg e q u a n titie s . Zinc d u st is a ls o v e ry d e f in ite ly ex p lo siv e. C. - ASBESTOS 11FLOAT"? F l o a t a s b e s to s i s u se d i n t h e m a n u fa c tu r e o f t r a c t o r l u b r i c a n ts, I t comes in 150 pound c lo th bags by r a ilr o a d , ab o u t 2000 bags to a c a r. From 200 to 3000 pounds a r e u sed p e r b a tc h and from tw o t o f i f t e e n b a tc h e s a r e made p e r month. The b ag s o f a s b e s to s f l o a t a re dumped in to th e m ixing k e t t l e by th r e e men w ith an a v e ra g e s e r v ic e o f tw elve y e a rs . These la b o r e r s a re exposed to d u s t ^<fabout fo rty m in u tes p er b a tc h . Dust c o n c e n tra tio n as hig h as 8,269,440 p a r ti c le s , te n m icrons o r l e s s in s i z e , per cu b ic fo o t a re produced d u rin g th e dumping o f a s b e s t o s f l o a t , t h e a v e ra g e b e i n g 3 ,0 5 8 ,5 6 0 p a r t i c l e s p e r c u b ic f o o t . A bout 98?2 o f th ese p a rtic le s a re s lig h tly angular, round, tra n s p a re n t in appearance under th e K onim eter m icro sco p e, and two m icrons or l e s s in s iz e ? 2% a re round, sem i-opaque, p la te lik e , fiv e m icrons or over in size, Reoent in v e stig a tio n s have in d icate d th a t the in h a la tio n o f asb esto s p a rtic le s te n m icrons o r le s s in s iz e is even more h azard o u s th a n was o r ig i n a ll y b e lie v e d , and th a t in o rd er to prevent harm ful e f f e c ts co n c e n tra tio n s should be kep t below fiv e m illio n p a r ti c le s (10 m icrons o r l e s s ) per cu b ic fo o t. The p h y s io lo g ic a l e ffe c ts h a v e a l r e a d y b e e n d is c u s s e d u n d e r "ASBESTOSIS" s o n eed n o t b e g iv e n an y f u r t h e r con s i d e r a t i o n . Men h a n d lin g a s b e s to s f l o a t sh o u ld b e re q u ir e d t o w ear ap p ro v ed r e s p i rato rs. D GROUND MICA? G round m ica (8 0 m esh) i s u s e d i n th e m a n u fa c tu r e o f a x l e g r e a s e . I t comes i n 100 pound b u rla p bags. About f i f t y pounds o f ground m ica is used p er b a tc h a n d .a n av erag e o f fiv e b a tc h e s a re made p e r month. The period, o f exposure w ill n o t exceed te n m inutes a b a tc h . H andling ground m ica produces an average of 2,577,120 p a r tic le s te n m icrons o r le s s in s iz e , p er cubic fo o t. About 60$ of th e se p a rtic le s are tra n sp a re n t irre g u la rly shaped sc a le lik e in appearance under the K onim eter m icroscope, and fiv e m icro n s or le s s in s iz e j a b o u t 40$ a re over te n mi c ro n s in s 1ee. The tr a n s p a r e n t p la te s have sm a ll lin e s o r f is s u r e s and ap p ear to co n tain sm all a ir bubbles, k A lthough ground m ica h as n e v e r b een c o n s id e re d a h azard o u s d u s t, some r e c e n t s tu d ie s made among th e w orkers in N o rth C a ro lin a in d i c a te t h a t c o n tin u e d ex p o su re to l a r g e q u a n t i t i e s o f ground m ic a o v e r a p e r io d o f y e a r s w i l l p ro d u o e a f i b r o s i s . How ever, th e re is v ery l i t t l e p ro b a b ility o f any tro u b le where c o n c e n tra tio n s a re kept b elow 1 0 ,0 0 0 ,0 0 0 p a r t i c l e s p e r c u b ic f o o t o f a i r an d w h ere t h e e x p o s u re t o m ic a dusfc is such a sm all p ercen tag e o f th e em ployee^ w orking tim e, E - SULPHUR? S u lp h u r f l o u r i s u s e d f o r s u l p h u r i z i n g c u t t i n g o i l s and i n p re p a ra tio n of s p e c ia l lu b ric a n ts fo r hypoid g ears. Crude su lp h u r is used m anufacture of su lp h u ric acid and in th e trea tm e n t of g aso lin e and naphtha moval o f im p u rities such as the m ercaptans. th e in the for re S u lp h u r Flour? S u lp h u r f lo u r comes in p a p e r - lin e d wooden b a r r e l s , 100-pound c lo th bags, o r 150-pound b u rla p bags. About 2500 pounds o f th is su lp h u r is dumped in to th e m e ltin g k e t t l e b y two men w ith an av e ra g e s e r v ic e o f tw elv e y e a r s , once a day. T heir ex p o su re to th e d u st which r e s u lts from h an d lin g and dumping th e b a g s , an a v e ra g e o f 1 ,5 4 0 ,6 0 8 p a r t i c l e s , te n m icro n s or l e s s , p er cu b ic f o o t, is ab o u t f i f t e e n m in u tes per man p e r s h i f t on an ave r a g e . No g o g g le s o r r e s p i r a t o r s a r e w orn. A bout 90$ o f th e d u s t p a r t i c l e s in sam ples ta k e n d u rin g th e dumping of th e su lp h u r f lo u r w ere s l i g h t l y angu l a r c r y s t a l l i n e in ap p earan ce u n d er th e K onim eter m icroscope, and f iv e mi cro n s o r le s s in s iz e j 10$ w ere sem i-opaque, rounded, and over fiv e m icrons in s iz e . The la r g e r p a r ti c le s ap p ea r t o c o n ta in sm a ll a i r bubbles There w ere a lso a number o f very sm all speoks. A bout 370 pounds o f f lo u r s u lp h u r i s u sed p e r b a tc h in th e p re p a r a tio n o f h y p o id g e a r l u b r i c a n t . Two b a t c h e s a r e made p e r week on a n a v e r a g e . The ex posure t o th e su lp h u r d u s t i s only a b o u t two h o u rs p er week on an av e ra g e . S inoe th e su lp h u r i s dumped in to drums of o i l b ein g a g ita te d by a ra p id ly re v o lv in g p ro p e lle r ty p e m ixer more d u st is produced th a n where th e bags a re sim ply dumped in to a k e t tle . Sam ples ta k e n d u rin g t h i s o p era tio n had as h igh as 6,910,080 p a r tic le s , te n m icrons or le s s in s iz e , per c u b ic f o o t. The a v e ra g e was 3 ,7 8 3 ,5 5 2 p a r t i c l e s per c u b ic fo o t. The d u s t p a r tic le s had th e same c h a r a c te r is tic s as th o s e given in th e p re c e d in g . f paragraph. Crude Sulphur? Crude su lp h u r comes in box c a rs holding about 90,000 pounds, u s u a lly from E ree p o rt, Texas. Towers a re f i l l e d w ith t h i s su lp h u r by fo u r -o o - men w ith an av erag e s e r v ic e of e ig h t years* I t r e q u ir e s about tw o h o u rs to f i l l a to w e r w ith a b o u t 1 0 ,0 0 0 pounds o f cru d e s u lp h u r . Two to w e r s a r e c h a r g , ed e v e ry week* C o n s e q u e n tly , t h e men a r e exposed a b o u t f o u r h o u r s a week t o th e s u lp h u r d u s t cau sed by b re a k in g up th e lumps (4 ,3 0 4 ,6 4 0 p a r t i c l e s , te n m i crons o r le s s , per cubic fo o t) and sh o v elin g the cru d e sulphur in to th e tow er e le v a to r (an average o f 3,357,640 p a r tic le s per cu b ic fo o t). The amount of d u s t produoed by t h i s o p e ra tio n is somewhat reduced by th e steam tu rn e d on in sid e th e e le v a to r s h a ft to prevent dust explosions. About 60$ of the d u st p a r t i c l e s i n sam p les t a k e n w h ile t h e to w e r waB b e i n g f i l l e d w e re s l i g h t l y angu l a r c r y s ta l lin e in ap p earan ce under th e Konimeter m lcrosoope and fiv e m icrons or le s s in s iz e j 35$ w ere rounded, sem i-opaque, te n m icrons or over in s iz e j and -6$ were opaque sc a le lik e , between fiv e and tw elve m icrons in s iz e . Sulphur dust p a r tic le s are ex p lo siv e b u t o therw ise a re n o t con sid ered hazard ous any m ore t h a n any o f t h e o th e r " n u is a n c e 1' d u s t s , a l th o u g h th e y w i l l i r r i t a t e t h e muoous membranes and th e ey es a f t e r s l i g h t ex p o su re. C o n seq u en tly , i t i s a d v is a b l e t o w ear ru b b e r ty p e g o g g le s and a p p ro v e d r e s p i r a t o r s , s u c h a s th e MSA Comfo ty p e . In an a r t i c l e by Aldo C e s ta ri (Aroh, In te rn , Hharmacadynamie, 1933, v o l, 46, pp. 300-314) i t is stated " In tra tra c h e a l in je o tio n of su lfu r suspensions brings about ex c re tio n o f hydrogen s u lfid e in a period o f 60 hours. There are s lig h t exudative and in f i ltr a t iv e reac tio n s in the lungs. I t is supposed th a t a substance sim ila r to g lu tath io n e reduces the s u lfu r to hydrogen su lfid e , " - LITHARGE L i t h a r g e i s ad d ed t o th e P lu m b ite o r " D o c to r" S o l u t i o n t o a s s i s t i n th e rem oval of m ercaptans, o th e r su lp h u r compounds and u n sa tu ra te d hydrocarbons from g a s o lin e and n aphtha. From one to fiv e 600-pound drums o f li th a r g e a r e used in a b a to h , depending upon th e sto o k to be tr e a te d and th e c o n d itio n o f th e "D octor So l u t i o n " , The l i t h a r g e i s removed from th e drum a sh o v e l a t a tim e , and ab o u t f i f t e e n m in u tes a r e re q u ire d to dump one b a to h , A b a to h i s made onoe a week on an av era g e. The av era g e s e rv ic e of th e men in v o lv ed in th is o p e ra tio n is seven y e a rs . They wear MSA Comfo r e s p i r a t o r s w i t h a n a p p ro v e d l e a d f i l t e r an d r u b b e r ty p e g o g g le s . A ll o f th e work o f adding li th a r g e is done in th e open a i r on a p latfo rm a t th e to p s o f th e so lu tio n tanks. The A verage d u st produoed d u rin g th e dumping o r sh o v e lin g o f l i t h a r g e in to th e s o lu tio n ta n k is 3 ,077,480 p a r tic le s , te n m iorons or le s s in s iz e , per cubio fo o t, although th e re were as high as 9,288,960 p a r tic le s per cubic fo o t d u rin g th e o p eratio n , A rough estim atio n of th is lith a rg e co n cen tratio n in d io ates th e presence o f from fiv e to f ifte e n m illig ram s o f le a d per te n cubic m eters - th e amount th a t an a v era g e p erso n d o in g m o d erate work w ould b re a th e in one day. This is in excess o f 1 ,5 m illig r a m s i n te n o u b ic m e te rs w hich i s th e maximum a llo w a b le l i m i t s e t by th e U n ited S ta te s P u b lic H e a lth S erv ice, A bout 80$ o f th e s e d u st p a r tio le s w e re .rounded, tr a n s p a r e n t, o r y s ta l lin e in app earan ce u n d er th e K onim eter m icro sco p e, and f iv e mi o rons o r le s s in siz e j a b o u t 15$ were over te n m icrons and appeared to c o n ta in sm all a i r b u b b le sj 6$ were d ark opaque s c a le - lik e , from fiv e to te n m iorons in s iz e , U e c e s s a r y P r e c a u t i o n a r y M easu res When H a n d lin g L i t h a r g e. L i t h a r g e i s a com pound o f le a d , and c o n seq u en tly th e re is th e p o s s ib ility o f le ad p o iso n in g u n le ss a /ew sim p le p re c a u tio n s a r e o b serv ed t o p re v e n t th e e n tra n c e o f le a d in to th e body ' ?by s w a llo w in g m in u te p a r t i c l e s o f t h e l i t h a r g e d u s t , b y i n h a l i n g th e d u s t , o r by a b s o rp tio n from th e sk in when h an d lin g th e lith a rg e * An e f f o r t should be made to cau se as l i t t l e d u st as p o s s ib le . In s tru c tio n s issu e d by the M edical D epartm ent re q u ire that -5 4 - i I " 1 . Ho em ployee s h a l l h a n d le l i t h a r g e u n t i l he h a s b e e n exam ined \ and c e r t i f i e d as p h y s ic a lly q u a l if ie d b y th e Company D octor { / "2. Em ployees m ust be s e n t to th e Company D o cto r f o r p h y s ic a l ex - | am in atio n a t l e a s t every s ix months o r a t th e f i r s t s ig n o f i l l health, 8 "3 , R e s p i r a t o r s - An a p p ro v e d ty p e o f l e a d d u s t r e s p i r a t o r , p r o p e r - | ly a d ju s te d , s h a ll b e worn when h a n d lin g li th a r g e . A ll r e s p i r a to r s s h a l l be th o ro u g h ly c le a n e d w ith so ap and warm w a te r, | "4, C lo th in g - U n io n a lls , cap s o r some head c o v e rin g and g a u n t le t | glov es s h a l l be worn when h a n d lin g l i t h a r g e . Upon th e com ple tio n of t h i s o p e ra tio n th e o u ter c lo th in g m ust be removed and | placed in a lo c k er used fo r th is purpose only. U n io n alls should be washed a t le a s t once a week, 1 "5, B athing and lo ck er f a c i l i t i e s - A co n v en ien tly lo o ated lo o k e r | and was h room s h a l l be d e sig n a te d f o r u se o f em ployees hand lin g lith a rg e . S ep arate lockers should be provided fo r s tr e e t | c lo th e s , work c lo th e s , and one f o r U n io n a lls worn when hand lin g li th a r g e . In p la n ts where men a re h a n d lin g l i t h a r g e | th ro u g h o u t th e s h i f t , o n ly two lo c k e rs n eed b e p ro v id e d . The f lo o r s o f th e lo c k e r rooms where th e men ch an g e t h e i r d u s t | covered U nionalls and th e benches s h a ll be thoroughly m oisten ed b e fo re b ein g c le a n e d , | "6, P ersonal c le a n lin e ss - General perso n al c le a n lin e ss is of f i r s t | im portance, I (a ) Hands m ust be th o ro u g h ly washed on th e co m p letio n o f th e lith a r g e han d lin g o p eration. Hands must a ls o be th o ro u g h ly ( washed b efo re e a tin g or p la c in g a n y th in g in th e mouth. A s p e c ia l e f f o r t sh o u ld be made t o c le a n th e f in g e r n a i l s so | as to remove any lith a r g e , I (b) Never e a t u n til lith a r g e covered c lo th in g has been removed and th e hands washed, (c ) T eeth should be brushed a t l e a s t tw ioe a day and th e te e th | and gums k e p t i n good c o n d itio n . (d) The m outh should be rin se d th o ro u g h ly b e fo re e a tin g . (e ) Never use to b a cco in any form w h ile w orking in and around lith a rg e ," ( The r e s p o n s i b i l i t y f o r t h e c a r e f u l o b s e r v a n c e o f ALL o f t h e s e i n s t r u e - tio n s should be placed upon th e foreman, K G -- SODA ASH; Soda a s h (58^? Na.g0 ) i s u sed t o fo rm a s o l u t i o n f o r n e u t r a l i z i n g a c i d o i l . T h irty 200-pound c lo th bags o f soda ash a r e dumped in to a ta n k o f w a te r p er ( jb a tc h by s ix men, w ith an av erag e s e rv ic e o f f iv e y e a r s , from th e G en eral Labor De- ^ p a r t m e n t j th r e e b a tc h e s a week. Men exposed t o d u s t r e s u l t i n g from o p en in g and | dumping th e bags o f so d a ash a b o u t f iv e h o u rs a week, E ig h t men spend a b o u t h a l f a d ay a m onth u n lo a d in g b a g s from r a i l r o a d box c a r s . The men who do t h e u n lo a d in g w ear MSA Comfo r e s p i r a t o r s and a r e n o t th e sam e men as t h o s e d o in g t h e m ix in g who do n o t w ear any r e s p i r a t o r s o r g o g g le s . The a v e ra g e d u s t p ro d u c e d by th e dumping an d g - 55- m ixing o p eratio n is 1,003,337 p a r tic le s , le s s th a n te n m icrons, per cubic fo o t of a ir. These p a rtio le s a re a ll s lig h tly an g u lar, c ry s ta llin e in appearance under th e K onim eter m io ro sc o p e and about f iv e m icrons in s iz e . Many a r e t r a n s p a r e n t, g la s s l i k e . T h e re a r e a- num ber o f s m a ll b la c k s p e c k s , II - TALC o r " SOAPSTONE"; P u lv e r iz e d t a l c o r " s o a p s to n e " i s u se d a s a f i l l e r i n t h e m a n u fa c tu re o f " h o t n e c k " g r e a s e s u se d i n t h e s t e e l m i l l s . A c co rd in g t o R, B, Ladoo (U .S . B u re a u o f M ines B u i, No. 213, 1919) o r d i n a r y t a l c o r s o a p s to n e i s S t e a t i t e (h y d ro u s m agnesium s i l i c a t e - H2M gg(SiO g)4.), I n t h e form o f pow der, t h e t a l o i s g r e y is h w h ite . A s s o c ia te C hem ist F r e d e r ic k Goldman o f th e U ,S, B ureau o f M ines, whp made a ch em ica l a n a ly s is o f sam ples o f t a l c as m ark eted , re p o rts* -- 3 "r-j - - : SiO g............ .................. .. 4 6 .0 4 p e r c e n t CaO.......... .. ................ .. 4, 39 " " MgO............................... 2 6 .2 0 " " Combined O x id e s.. . . . 1 5,64 " " G rease m akers u s u a lly c o n sid e r th e com p o sitio n o f "so ap sto n e" which th e y use as ap p ro x im ately 90$ magnesium s i l i c a t e and 10$ c alciu m c arb o n a te. I t comes in 90-pound paper bags, 700 bags to a box c a r. About 7200 pounds a re used p er b a tc h and one b a tc h is made a day on a n av erage. The "so a p sto n e " i s dumped in to th e m ixing k e t t l e by two men w ith an a v e ra g e s e r v ic e o f t e n y e a r s . T h is dumping which r e q u ir e s a b o u t a n h our p e r b a tc h i s a r a t h e r d u s ty o p e r a tio n . One sam ple ta k e n a t f a c e l e v e l j u s t a f te r a bag had been dumped had as h ig h as 2 2 ,9 9 5 ,8 4 0 p a r ti c le s , te n m icrons o r le s s i n s iz e , p e r cubic f o o t o f a ir . The av e ra g e d u s t produced was 1 3 ,0 6 4 ,9 6 0 d u s t p a r t i c l e s per cubic fo o t. About 98$ o f th e se d u st p a r tic le s were tra n s p a re n t, c r y s ta l lin e , irre g u la r ly shaped p la te s and ro d s, in appearance under th e K onim eter m icro scope. Most o f th e se p a r tic le s (ab o u t 98$) w ere fiv e m icrons or le s s in s iz e , th e rem ainder b e in g te n m icro n s or o v e rj ab o u t 2$ w ere s c a le - lik e , sem i-opaque, f iv e mi crons or le ss in siz e , P h y s io lo g i o a l E f f e c t s P roduoed By T alo D u s ts , A bout tw o y e a r s ago Dr. W. C, D re e s s e n , P a s s e d A s s i s t a n t S urgeon, an d J , M. D a l l a V a ll e , A s s i s t a n t S a n i t a r y E n g i n e e r, U nited S ta te s P u b lic H ealth S e rv ic e , made a stu d y to a s c e r ta in w h eth er th e re is a connection between ta lc dust exposure and th e r e la tiv e ly h ig h tu b e rc u lo s is d e a th r a t e in M urray C ounty, G eorgia, w here two t a l o m i lls and m ines a re lo c a te d . They found ( R e p r in t No, 1669 from th e P u b l i c H e a lt h R e p o rts V o l. 5 0 , No, 5 , Feb. 1, 1935, pages 131-143)* " P h y s i c a l a n d r o e n tg e n o lo g io e x a m in a tio n s w ere made o f 66 men and women who w e re ex p o sed o r h a d b e e n e x p o s e d t o t a l c d u s t. I n th e h ig h e r d u s t g ro u p s c o m p risin g 33 men, 8 w ere found to have Pneumo c o n io sis I and 8 to have Pneum oconiosis I I or I I I , S ix of th e t h i r t e e n ex am in ed w ere d ia g n o s e d a s h a v in g P n e u m o c o n io sis I . No advanced s ta g e s o f th e d is e a s e were found in th i s group. In th e g ro u p exposed to low c o n c e n tr a tio n s o f d u s t, no P neum oconiosis was found," The f in a l c o n c lu s io n o f t h i s stu d y was th a t a lth o u g h G eorgia t a l c a p p ea rs to be "more in ju rio u s th a n tr e m o lite ta lc " th e h ig h tu b e rc u lo s is m o r ta lity r a te in th e County "could not be a ttrib u te d to the ta lc in d u stry ". In v e s tig a to rs have su g g ested , how ever, th a t f o r more or le s s co n tin u o u s expo su res c o n c e n tra tio n s o f ta lc or "soapstone" d u st should not exceed 15,000,000 p ar tio le s , te n m icrons or le s s in s iz e , per cubic fo o t o f a ir. I - GRAPHITE* Pow dered g r a p h i t e (8 0 $ t o 8 5 $ g r a p h i t i c c a rb o n and 15$ p r o b a b ly magnesium s i l i c a t e ) is used in th e m an u factu re o f s p rin g and p re ssu re lu b r ic a n ts . I t -56- oomes in m e ta l drums o r 100-pound p a p er lin e d b a g s. About 3700 pounds o f powdered g ra p h ite i s used p er b a tc h and one b a tc h is made p er day on an average. The jr a p h ite i s dumped in to th e m ixing k e t t l e by men w ith an av e ra g e s e rv ic e o f seven l ^ e a r s . T h is o p e r a t i o n r e q u i r e s a b o u t f o r t y m in u te s p er b a t c h p e r man on a n a v e ra g e . T hree men a re u s u a lly engaged in t h i s dumping. They wear r e s p ir a to r s w h ile hand lin g and dumping g ra p h ite , which is n o t a p a r ti c u la r ly d u sty o p e ra tio n , The average d u st produced is 1,803,080 p a r tic le s , te n m icrons o r le s s , per cubic fo o t o f a ir. A ll o f th e s e d u st p a r tic le s a re rounded or s lig h t ly an g u lar, b la c k opaque, amorphous, sooty or dark grey in appearance under th e K onim eter m icroscope, and th re e m icrons or le ss in size. <J - SLATE FLOUR? S l a t e f l o u r (3 0 0 m esh) g iv e s r i g i d i t y t o a s p h a l t on " f a s t s u r faces" such as ste e p ro o fs and pipe lin e s , and p rev en ts i t s running o ff. I t also produces d e s ir a b le w eath erin g p ro p e rtie s , M ix tu re s as low as 10$ s la te f lo u r and a s h ig h a s 40$ a r e vised. An a v e ra g e o f two to n s o f s l a t e f l o u r i s u sed t o ea c h s t i l l w hich av erag es ab o u t 800 b a r r e ls of steam reduced a s p h a lt. Since th e s l a t e f lo u r is in tro d u c e d by th e u se of c lo s e d "pipe l i n e s and c e n t r i f u g a l pumps, th e only d u st produced is th a t w hich r e s u lts d u rin g th e u n lo a d in g o f th e sacks and dumping them in to th e hop p er. The s l a t e f l o u r comes in 50-pound p ap er b a g s, 750 b a g s to a r a ilr o a d box c a r. Four men w ith an average* s e r v ic e o f about a y e a r, open th e bags and dump th e s l a t e f lo u r d i r e c t l y in t o a hopper from w hich i t i s siphoned by camp re s s e d a i r to a s to r a g e ta n k h o ld in g ab o u t 15 t o n s . About f o u r c a rlo a d s a month a re re c e iv e d and an av erag e o f about 5 ~ l/2 hours is req u ired to unload each c a r. About one and th r e e - q u a r te r m illio n pounds were dumped d u rin g th e la s t q u a r te r p e r io d . The men w ear MSA Comfo r e s p i r a t o r s . A s c r e e n a n a l y s i s o f t h i s s l a t e f l o u r showed t h a t 9 9 .7 $ p assed th ro u g h a 200 mesh s c re e n and 9 6 ,8$ th ro u g h a 325 mesh s c r e e n . Due t o t h e f i n e n e s s o f s l a t e f l o u r and i t s low b u lk d e n s i t y ( 1 ,0 4 ) con sid e ra b le d u st, an average of 12,007,680 p a r tic le s , ten m icrons or le ss in s iz e , |er cu b ic fo o t o f a i r , and counts as h ig h as 16,53 8 ,8 8 0 p a r t i c l e s per cu b ic fo o t, a re produced d u rin g dumping th e sacks and f i l l i n g th e s to ra g e ta n k . About 98$ of th ese dust p a rtic le s are s lig h tly an g u lar, tra n sp a re n t, c ry s ta llin e in appearance under th e K onim eter m icroscope, and f iv e m icrons o r le s s in s iz e ) 2$ a re sem i-opaque, s l i g h t l y a n g u la r. T here w ere a few p l a t e l i k e p a r t i c l e s w hich ap p eared t o c o n ta in sm all a ir b u b b les, and a la rg e number o f sm all b la c k p a rtic le s . A p etro g ra p h ic exam ination made of a s l a t e flo u r sam ple a t the U nited S ta te s Bureau c f Mines E xperim ent S ta tio n in P itts b u r g h , P en n sy lv an ia showed t h a t i t con t a i n e d m ore th a n 1 $ Q u a r tz ( S i 0 2 ) 3 0 $ S e r i c i t e (K2 O-3A I2 O3-6 SiOg-gHgO), 40$ opaque and 30$ f iv e d i f f e r e n t u n id e n tif ie d c o n s titu e n ts . A ch em ical a n a ly s is o f s l a t e g r a n u le s and f l o u r ( J o u r . I n d u s t . Hyg. V o l. XV. ,No, 2 ,M ar, 1933, p, 6 7 ) r e p o r t s t h e s e c o n s titu e n ts? S ilio o n D ioxide . . . . . . . . 5 9 . 27$ Titanium D io x id e.. . . . . . . 0, 99$ Aluminum O xide. . . . . . . . . . 18. 81$ F e rric O xide.. . . . . . . . . . . 1, 12$ F erro u s Oxide . . . . . . . . . . 6, 58$ Managanous O x id e.. . . . . . . 0. 13$ C alciu m O x id e.......... .. 0. 42$ Barium Oxide. . . . . . . . . . . . 0. 05$ M agnesium O x id e ,...............2, 21$ P o ta s s iu m O x id e .. . . . . . . 3, 75$ Sodium O xide. ..........1, 88$ W ater below 110C. . . . . 0, 32$ " above 11 . . . . . . 3 ,9 8 $ Phosphoric O xide.. . . . . , 0 . 11$ Carb on D io x id e.. . . . . . . . 0, 21$ F e rric S ulphide.. .. .. .. 0 .1 5 $ S p ecific G ravity - 2,795 "The s ilic o n found, though expressed in th e chem ical a n a ly sis as s ilic o n d io x id e, is not d iffe re n tia te d chem ically as to the forms p re s e n t in th e o rig in a l m in e ra ls, w hether fre e s i l i c a or silic a te , " E f f e c t o f S la te F lo u r on The Lungs - In h is paper " E f f e c ts o f C e r ta in S i l i c a t e Dusts in th e Lungs" read b e fo re th e I n d u s tr ia l Hygiene S ectio n o f th e Am erican P ublic H e a lth A s s o c i a t i o n a t W a sh in g to n , D. C. on O c to b e r 27, 1 9 3 2 , Dr, Waldemar C. D re e sse n Of t h e U n ite d S t a t e s P u b l i c H e a lth S e r v ic e , r e p o r t i n g th e r e s u l t s o f h i s s tu d ie s o f 'w orkers exposed to s la t e d u s t, w ro tet "O f th e 48 c a s e s o f pneum oconiosis o b serv ed , a l l w ere in th e f i r s t sta g e except 5 cases. In g e n era l, th e pneum oconiosis observed in th e e a rly or f i r s t sta g e cases resem bled th a t induced by cem ent d u st. The b ro n c h ia l s t r i a t i o n s , however, w ere somewhat more promi n e n t. There was alw ays a m oderate b i l a t e r a l in c re a s e i n th e s iz e and d e n sity o f th e h i l a r shadows w ith ac c e n tu a tio n s o f b ro n c h ia l s tr ia tio n s w hich extended w ell out in to each lu n g f ie ld . The l i n e a r s t r i a t i o n s seemed " s o f t e r " in a p p e a ra n c e and la c k e d some of. th e sharpness o f d e t a il w hich is u su a lly observed in th e X -rays of i n d i v i d u a l s who h av e i n h a l e d s i l i c a d u s t. T h is d i f f u s e , f i n e . g e n e ra liz e d f i b r o s i s was c h ie f ly co n fin e d to th e low er tw o - th ir d s o f th e lung f ie ld s , " In th e second sta g e an in creased prom inence o f th e above m ention ed c h a r a c t e r i s t i c s vas p r e s e n t w ith th e a p p e a ra n c e o f f l a k e l i k e , dappled areas o f in creased d en sity in both lung fie ld s . In th e t h i r d stag e th e s e dappled a re a s seemed to conglom erate, and in th is manner gave way to m a ssiv e , clouded a re a s o f in c re a s e d d e n s ity ." Dr. D reessen found t h a t a lth o u g h th e s i l i c a t e d u s ts o f s l a t e "in d u ce a f in e d if f u s e , b i l a t e r a l f ib r o s is o f th e lungs which is d e f in ite ly dem onstrable in th e X -ray" w orkers exposed to s l a t e d u s t do n o t b e g in to show d e f in i te f i r s t s ta g e pneumoconio sis u n t i l a f t e r m ore t h a n t e n y e a r s ' e x p o s u re . He d id n o t f i n d an y e v id e n c e t h a t che r e s u lta n t pneum oconiosis had led to d is a b ility . K - GRIIIDIMG PERRIS ROOTt D e r r is r o o t i s u sed i n t h e m a n u fa c tu r e o f i n s e c t i c i d e s . I t comes in 500-pound b a le s from th e Dutch E ast In d ie s . In o rd er to reduce d u s t, th e b a le s a r e th o ro u g h ly w e tte d w ith w h ite o il . The r o o t is ground a t th e r a te o f 500 pounds an hour t o p a s s th ro u g h a 3 /8 " - s o r e e n . One man w ith t h r e e y e a r s ' s e r v ic e is exposed to an average d u st co n c e n tra tio n of 1,604,800 p a r tic le s , te n m icrons or l e s s , p e r c u b ic f o o t o f a i r . A bout 80% o f t h e s e d u s t p a r t i c l e s a r e r a t h e r ro u n d , c r y s ta l lin e in appearance under th e Konim eter m icroscope, and about fiv e m icrons i n s i z e j 20% a r e s h a r p ly a n g u l a r , f i v e m ic ro n s o r l e s s i n s i z e . T he p a r t i c l e s a p p ear to be more in o rg an ic th a n o rg an ic in c h a ra c te r. E v id en tly th e lig h te r ro o t d u s t p a r tic le s a re e ith e r la rg e r th a n 30 m icrons and w ere, th e re fo re , f i l t e r e d out by th e K onim eter f i l t e r o r were c a rrie d out by th e exhaust v e n tila tio n , th u s le av in g th e d i r t o r s o il which had adhered to th e ro o ts . The g rin d e r i s lo c a te d in a sm all room w e ll v e n tila te d by means o f a 3 0 -in c h m o to r-d riv e n fan . T his e x p la in s th e low d u st c o n c e n tra tio n in th e sam ples ta k e n d u rin g th e g rin d in g o p e ra tio n . The o p erato r w ears ru b b e r g lo v e s, c o v e r - a l ls , and i s p ro v id ed w ith a fre s h a i r hose ty p e o f mask w hile grinding. To W hat E x te n t i s D e r r is T o x ic? A cco rd in g t o r e c e n t s tu d ie s by t h e U n ited S t a t e s D e p artm en t o f A g r i c u l t u r e ( i n d u s t , & Eng. Chem. V o l. 2 8 , N o .7 , J u l y 1936, pps. 815-821) D erris is a p o ssib le h e a lth hazard to those engaged in m illin g , grind i n g , and d i l u t i n g i t (Derris) without t h e use o f suitable protective m easures P h a rm a c o lo g ic a l s tu d ie s show t h a t D e rris and i t s w ater e x tr a c ts a f f e c t th e r e s p ir a - p ry c e n te r which i s i n i t i a l l y s tim u la te d and th e n , a f t e r f a t a l d o se s, com pletely R e p re sse d , w ith d e a th r e s u ltin g . D e rris d u st when a p p lie d t o th e a rm p its was a ls o Jxound to provoke a "m ild ev an escen t i r r i t a t i o n . " L_ - GRINDING PYRETHRUH FLOWERS; P y re th ru m f lo w e r s a r e a n im p o r ta n t s o u r c e o f one o f th e e s s e n t i a l i n g r e d i e n ts o f i n s e c t i c i d e s . They come from Jap an i n m at co v ere d h a l e s w e ig h in g a b o u t 450 pounds. On a n a v e r a g e , a b o u t t e n b a l e s a r e g ro u n d p e r s h if t. Opening th e b a le s o f com pressed flo w e rs is th e d u s tie s t p a rt o f th e opera tio n , producing on an average 2,039,040 p a r ti c le s , te n m icrons or l e s s , per cubic foot of a ir. About 85$ of th ese p a rtic le s a re angular, c ry s ta llin e in appearance under th e K onim eter m icroscope, and th re e m icrons o r le s s in s iz e j ab o u t 15$ are f l a t round p a r t i c l e s and d is c s and s h re d s , t e n m icrons o r ls s s . The c r y s t a l l i n e ap p earin g d u s t p ro b ab ly o rig in a te s from th e s o i l w hich h as blown on th e flow ers or p la n ts , One man i s ex p o sed p e r s h i f t f o r a b o u t fo u r h o u rs a day d u r in g a n in e m onth p e r io d . He w e a rs a W i l l s o n d u s t r e s p i r a t o r . The g r i n d e r i s e n c lo s e d i n a m e ta l housing connected by a fo u rte e n -in c h duct to a s ix te e n -in c h m otor d riv e n exhaust fan. Pyrethrum d u st others in the le a s t] some in d iv id u a ls to in pyrethrum d u st. seems to i r r i t a t e th e s k in of some in d iv id u a ls as a m atter of fa c t i t causes an a lle rg ic type such an ex ten t th a t i t is in a d v isab le fo r suoh and not a f f e c t o f r e a c tio n i n `? p erso n s to work M - MIXING AND PACKING " FLIT" POWDER; " F l i t " pow der i s a m ix tu r e o f p u l v e r i z e d d e r r ls ro o t, py reth ru m flo w ers and o th e r' in g re d ie n ts . I t is mixed in a s p e c ia l room p ro v id e d w ith e x h a u st v e n t i l a t i o n b y a man w e a rin g a r e s p i r a t o r . The d u s t i e s t p a r t o f th i s o p e ra tio n is s i f t i n g th e p u lv e riz e d d e r r is and pyrethrum which produces an average o f 8,722,560 p a rtic le s , te n m icrons or le s s , per cubic fo o t of a ir . About 95$ of th e se d u st p a rtic le s are a n g u la r, c r y s ta llin e in appearance under th e K onim eter m icroscope, and about th re e m icrons in s iz e j about 5$ a re le s s c r y s ta llin e and more opaque, fiv e m icrons or le s s in s iz e . F i l l i n g Cans; T h re e -q u a rte r and two and o n e -q u a rte r ounce t i n cans a re f i l l ed by au to m atic m achines, th e f i l l e r ends o f which a re en clo sed in a m e ta l housing w ith a fo u r-in c h exhaust d u c t to a fo u rte e n -in c h m o to r-d riv e n fan. T hat t h i s ex h a u st arrangem ent is f a i r l y e ffe c tiv e i s shown by an av erag e d u st c o n c e n tra tio n in sam ples ta k e n a t face le v e l of the o p e ra to r d u rin g th e f i l l i n g o p e ra tio n of 1,755-,840 p a r t i c l e s , te n m icrons o r le s s , p e r cubic fo o t o f a i r . The g i r l a t th e S ealer wears a b ag-type d u st re s p ira to r, VIII - CLEANING TUBES AN D DRUMS C O N T E N T S C lean in g tu b e s and drums of b o ile r s and p ro c e ss equipm ent i s a r o u tin e o p era tio n which produces c o n s id e ra b le d u s t b e lo n g in g more to th e "n u isan ce" c la s s th a n to th e f ib r o s is c a u sa tio n group. N ev erth e less, c o n s id e ra tio n should be g iven to keeping su ch d u s t down t o a minimum o f n o t more th a n 1 0 ,0 0 0 ,0 0 0 p a r t i c l e s p e r c u b ic f o o t due to th e number o f men engaged in th i s work and t h e i r more o r le s s c o n tin u o u s ex posure I. - CRACKING COIL SOAKING DRUMS; C ra c k in g c o i l s o a k in g drums " c o k e -u p " once a month, so th a t in many cases th e y a r e alm o st co m p letely f i l l e d w ith th e ex c e p tio n o f an opening down through th e c e n te r no g r e a te r th a n tw elve in c h es in diam e t e r . A t m ost p la n ts , t h i s coke is removed by a s p e c ia l m achine] a t - t h e o th e r s , men w ith an av era g e s e rv ic e o f te n y ears a r e r e g u la r ly engaged in c le a n in g th e s e drums by means o f a c o n c r e te b u s te r ty p e o f p n eu m atic c h i s e l , s t a r t i n g a t th e to p o f th e drum, One man works in s id e and tw o o u ts id e a t th e to p m anhole. The te m p e ra tu re in s id e th e drum i s about 90 d eg rees F a h re n h e it, E ach man works h a l f an h our in s id e and is th e n r e l i e v e d f o r a b o u t an h o u r . On an a v e r a g e , each man w orks a b o u t two and a h a l f h o u rs p e r s h i f t , two s h i f t s a week, A "b o a tsw a in " c h a ir i s used to g e t in and o u t o f th e drum. They w ear "h a rd b o ile d " h ats and l i f e - b e l t s . E x c e lle n t v e n t ila t io n i s p ro v id ed by a steam or an a i r syphon placed in th e bottom m anhole o f th e drum, as a r e s u l t o f w hich samples ta k e n a t fa c e le v e l o f men d u rin g th e o p e ra tio n o f th e pneum atic c h is e l had an average o f only 311,520 dust p a r ti c le s , te n m icrons or le s s , per cubic fo o t of about under th e Konim eter m icroscope, and about fiv e m icrons or le s s in s iz e ; 35$ were round, sem i-opaque, c r y s ta llin e , abo u t te n m icrons or over) and about 5$ w ere sm all x b la c k p a r tic le s . There were a ls o a few b la c k s c a le - lik e p a r ti c le s over t e n m icrons j i n s i z e . The m a jo r p o r t i o n o f t h i s d u s t i s p r o b a b ly coke o r c a rb o n and t h e s c a l e l i k e p a r ti c le s a r e , no do u b t, m e ta l from th e s id e s of th e drum o r from th e o h is e l. I I . - CRACKING COIL TUBES? T h ere a r e 183 tu b e s i n a h ig h p r e s s u r e c r a c k in g c o il u n it. A fte r running from tw en ty to tw e n ty -fiv e days, depending upon th e c h a r a c te r o f th e sto ck b e in g run, th e te m p eratu re and p re ssu re , th e petroleum coke which i s d e p o site d on th e tu b e s must be removed. L ib e rty a ir - d r iv e n tu b e c le a n e rs w ith cone and s ta r c u tte rs operated by men w ith an average se rv ic e of s ix y e a rs are used fo r t h i s purpose. The men work in gangs o f s i x t o e ig h t and a re exposed to d u st about s i x hours every two s h i f t s on an av era g e, They w ear n e ith e r g o g g les n o r r e s p i r a to r s although a d u st samle ta k e n ,,im m ediately a fte r.-re v e rs in g th e c le a n in g m achine w hile in a tu b e contained as high as 9,062,400 p a rti le s , te n m icrons or le s s in s iz e , p er cubic fo o t. A bout 30$ o f th e s e dust p a r tic le s a re b la c k , opaque i n a p p e a ra n c e u n d e r t h e K onim eter m ic ro s c o p e , an d two m ic ro n s o r l e s s i n s i z e ; 40$ a re an g u lar, tra n s p a re n t, p la te - lik e , te n m icrons or la rg e r) and 30$ a re an g u lar, tran sp are n t c ry s ta llin e , fiv e m icrons or le ss in size, `t Samples ta k e n on th e C le a n in g P la tfo rm w h ile c le a n in g C racking C o il Furnace tu b e s a t a N orthern re fin e ry had an average o f 113,280 p a r tic le s per cubic fo o t. N in ety -eig h t per cent, of th e se d u st p a rtic le s were rounded c r y s ta llin e in appearance under th e m icroscope and fiv e m icrons or le s s in s iz e . Samples ta k en in th e passage way b a c k o f th e fu rn a c e w h ile tu b e s w ere b e in g c le a n e d had as h ig h as 1 ,0 7 6 ,1 6 0 p a r tic le s , ten m icrons or le ss in s iz e , per cubic foot of a ir. This in d ic a te s th a t th e men in th e passagew ay, back o f th e fu rn a c e a r e exposed to more d u st th a n th o s e on th e c le a n in g p la tfo rm . I I I . , - WATER HEADERS AND BOILER TUBES? T ubes and h e a d e r s a r e c le a n e d tw io e a y e a r by means o f a i r - d r i v e n tu r b in e s . I t h as been found t h a t c le a n in g can be done m ore e f f e c tiv e ly i f done dry r a th e r th a n w et b ecau se th e d u st can be blow n out. I f w a te r w ere u se d , th e lo o se n e d m a te r ia l would so o n form a p a s te w hioh-w ould be sm ear ed back on th e tubes by th e a c tio n o f th e c le a n in g tu rb in e. R egardless o f th e d u st which is produced in c o n c e n tra tio n s as high as 30,359,040 p a r ti le s , te n m icrons or l e s s in s iz e p e r cu b ic fo o t of a i r , workmen p r e f e r w orking in d ry drums r a th e r th a n in w et ones. E ig h t men (two on each tu r b in e ) a r e engaged in t h i s c le a n in g o p e ra tio n w h ic h r e q u i r e s a b o u t tw e lv e days a y e a r . Men w ith an a v e r a g e s e r v i c e o f f i f t e e n y e a r s a r e assig n ed t o t h i s jo b from th e L abor D epartm ent, The te m p e ra tu re in s id e o f th e drums o r h ead ers is a b o u t 70 d e g re e s F a h re n h e it. In acc o rd an ce w ith th e u s u a l p ra c t i c e , men o p e ra tin g th e tu r b in e s , in s id e th e drum or h e a d e r, work ab o u t te n m in u tes a n d a r e r e l i e v e d f o r t e n m in u te s b y t h e i r c o -w o rk e rs who a s s i s t i n h a n d lin g th e a i r h o se in and o u t o f th e drum m anhole. R e s p ir a to r s have been p ro v id ed i n m ost c a s e s b u t a re n o t alw ays worn. The a v e ra g e d u s t p ro d u ced w h ile c le a n in g w a te r-h e a d e rs and b o i l e r tu b es i n sam ples ta k en from? Lovier P la t f o r m , F r o n t W ater H e a d e r................................... 1 8 ,3 0 6 ,0 4 8 p a r ts p e r cu f t . I n #2 Drum W hile C le a n in g W ater W all and T u b e s , , , , 5 ,6 6 4 ,0 0 0 " " " I n s i d e M anhole Drum #3 W hile B e in g C le a n e d . . . . . . . . 2 8 ,3 2 0 ,0 0 0 11 " About 40$ of th e du st p a r tic le s in th e sam ples ta k en on th e low er fro n t w ater-h ea d er platform, while header was being c l e a n e d , w e re ro u n d e d , d a r k r e d i n a p p e a r a n c e u n d e r t h e K onim eter m icro sco p e, and a b o u t two m icro n s i n s iz e ; 50$ w ere opaque, more o r \ le s s a n g u la r, and about fiv e m icrons in s iz e ) 10$ were c r y s ta llin e , s l i g h t l y a n g u la r, _.y an d o v e r te n m ic ro n s i n s i z e . A b o u t 65$ o f t h e p a r t i c l e s i n th e sam p le ta k e n i n s i d e -j-2 drum d u rin g c l e a n in g w ere b la c k , opaque, a n g u l a r , l e s s th a n tw o m ic ro n s i n s i z e j and ab o u t 15$ w ere round, more or l e s s opaque, o v er te n m icro n s. The c o n c e n tra tio n o f d u s t INSIDE t h e drum d u r in g c l e a n i n g a p p e a r s t o d e c r e a s e w ith t h e d i s t a n c e from t h e m an h o le a s i s d e m o n s tra te d b y t h e s e c o u n ts i n sam p les from Drum $ 2 ( R ile y B o il er); L ooation P a r tic le s pe r cu. f t. I n s id e ManI;ol About 8 f t. Inside n Xn I h It 1 fi It It D r u m , . , . . ............................. . ............................................... ir O $ 0 O e O a * 0 9 9 e * 4 0 4 * * * * * * 9 9 4 9 4 u Il P 4. it it if 1 9 ,2 5 7 ,6 0 0 4 ,0 7 8 ,0 8 0 2 ,2 6 5 ,6 0 0 1 ,5 8 5 ,9 2 0 1 ,1 3 2 ,8 0 0 The d u s t p a r t i c l e s from in s id e th e drum a p p e a r b la c k , a n g u la r and w ere le s s th a n two m iorons i n siz e -' - The d u s t fro m th e s e c le a n in g o p e ra tio n s a r e supposed to b e la r g e ly th e r e s u lts o f m etal c o rro s io n and sedim ent ( la r g e ly C alcium C arbonate and Calcium P hosphate) d ep o sited by th e tr e a te d B o ile r Feed W ater. A p e tro g ra p h ic exam ination o f a sam ple o f d u st from th e F ro n t W ater W all H eader was made b y .th e U n ite d S ta te s B u reau o f M ines E x p erim en t S t a t i o n a t P i tt s b u r g h , P e n n s y lv a n ia , who r e p o r te d ; Q u a rtz (S iO g ) ............................. v............................. Opaque o r C oated w ith Opaque M a te r ia l.. U n i d e n t i f i e d C l a y - l i k e . ................................. 1 p er oent. 90 " 11 9" " A cco rd in g to a ch em ica l a n a ly s is o f th i s same m a te r ia l made by a r e g u la r r e f in e r y ch em ist u sin g th e m ethod o f A dolph Knopf, U .S. P u b lic H e a lth S e rv ic e , th e d u st c o n ta in e d ; F re e S i l i c a ............................................................... 0 ,7 0 p e r c e n t . Combined S i l i c a ...................................................... 41. 01 " " A lthough th e a n a ly s is o f th e d u st shows a low f r e e s i l i c a c o n te n t, th e h ig h d u s t c o n c e n tr a tio n s fo u n d and th e p o s s i b i l i t y t h a t a t tim e s su ch c o n c e n tr a tio n s may be h ig h e r than those found, dem onstrate th e d e s ir a b ility o f w earing re s p ira to rs re g a rd le ss o f th e kind o f d u st encountered. ' IX - FOUNDRY OPERATIONS During re c e n t y e a rs c o n sid e ra b le a tte n tio n has been focused upon th e h e a lth of foundry w orkers by th e o p e ra tio n of! th e s o -c a llo d " S ili c o s i s R acket" which has ex tr a c te d la rg e sums of money from th e Foundry In d u stry , I t is d i f f i c u l t to is o la te t h i s ty p e o f work which g iv e s r i s e to a v e r y g e n e ra l e x p o su re t o d u s t w h ich may in v o lv e a l l w o rk ers employed i n th e foundry. In many c a s e s th e w o rk er is in such c lo s e c o n t a c t w ith th e duty a tm o sp h e re as t o c a u s e s e r io u s ex p o su re. Much p r o g r e s s h as b e e n made in re d u c in g t h e d u s t i n e s s o f o u r foundry o p e r a tio n s and p la n s a r e now b e in g co n sid ered w hich w ill f u r th e r safeguard o u r foundry w orkers. The fo llo w in g is a b r ie f o u tlin e o f foundry d u st producing o p eratio n s; A, - POURING MOLTEN METAL INTO SAND MOULDS - A b o u t 1 9 ~ l/2 t o n s o f m e ta l a r e poured p e r " h e a t" . T h ir ty - f iv e men w ith an av erag e s e r v ic e o f tw e lv e y e a rs spend about one and a h alf h o u rs pouring and s ix and a h a lf hours m oulding p er day, fiv e days a week. G oggles, a s b e s to s le g g in g s and c o n g re s s -ty p e shoes a r e worn by th e men h an d lin g th e m olten m e tal. About QO% o f th e m oulding san d , which is th e p rin c ip a l so u rce o f d u s t, is fre e s i l i c a (SiO g). D uring th e p o u rin g o p eratio n th e foundry a i r appears to be f u l l of d u s t and smoke, how ever, sam ples ta k e n d u rin g t h i s work a v e r- Jaged only 396,480 p a r tic le s te n m icrons or le s s in s iz e p e r cubic fo o t of a ir . P rac t i c a l l y a l l o f th e se d u st p a r tic le s appeared an g u lar, c r y s ta l lin e u nder th e K onim eter m io ro so o p e and were ab o u t two m icro n s o r l e s s in s iz e . -61- g iv e n a p e t r o g r a p h ic e x a m in a tio n by th e U, S, B ureau o f M ines E x p e rim e n t S t a t i o n in P i t t s b u r g h , P e n n s y lv a n ia who r e p o r t e d 50$ q u a r tz (S i0 2 )} 15$ C la y M in e r a l n o t com^ p l e t e l y i d e n t i f i e d , K a o l i n i t e i s AlgOg. 2 SiO 2 2H2Oj 5$ C a l o i t e (Ca COg ) and 30$ Opaque. B, - "SHAKING OUT" CASTINGS - A f te r p o u r in g , t h e c a s t i n g s a r e a llo w e d t o c o o l, th en th e moulds a r e l i b e r a l l y sp rin k led w ith w ater from a hose. The bands or d am p s a re removed and th e f la s k is thrown over and bro k en open. The rough c a s tin g s a r e p u lle d o u t , p i l e d u p and tr u c k e d to t h e C le a n in g Room. " S h a k in g O ut" i s con sid e re d one o f th e s e rio u s occupationA l d ise a se h aza rd s encountered in in d u stry and th e d u s tie st o p eratio n in fo u n d eries but due to th e thorough w ettin g and care fu l h a n d lin g by th e men, sam ples ta k e n d u rin g th e o p e ra tio n had an average o f only 858,230 d u st p a r t i c l e s t e n m icrons o r le s s p er c u b ic fo o t o f a i r . The im pinger ~ method would no doubt r e v e a l much h ig h e r c o u n ts. About 98$ o f th e d u s t p a r t i c le s w ere s lig h tly an g u lar c r y s ta l lin e in appearance under th e K onim eter m icroscope and w ere one m icro n or l e s s i n s iz e . "S haking Out" i s r a th e r h o t work, th e men p e r s p ir e f re e ly so th a t i t would be d i f f i c u l t to e n fo rc e th e w earing o f goggles and r e s p i r a t o r s . Tw elve men w ith an a v e ra g e s e r v ic e o f e ig h t y e a r s work on t h i s jo b , e ig h t h o u rs p er s h i f t , fiv e s h i f t s p er week. A fte r th e c a s tin g s have b een removed th e m oulding sand is a g a in w etted and th o ro u g h ly worked over w ith a m o to r-d riv en sand c u tte r w hich is a s e r ie s o f re v o lv in g b la d e s , s im ila r t o th o s e on a lawn mower, o p e ra te d by an e le o tr io m otor, m ounted on a ru b b e r - tir e d fo u r-w h eeled c a rria g e which moves back and fo rth over th e m oulding f l o o r . M o is tu re t e s t s a r e made and when t h e s e t e s t s i n d i c a t e 4 .6 t o 5 .6 m o is tu r e th e sand is co n sid ered ready fo r th e m oulders. D uring th e o p eratio n of th is sand cub\ t e r , th e o p erato r is exposed to an average d u st c o n c e n tra tio n of 1,529,280 p a r tic le s te n m icrons o r l e s s p e r cu b ic fo o t. These p a r t i c l e s w ere le s s th a n twc m icrons and w ere s lig h tly a n g u la r c r y s t a l l i n e in appearance under th e Konim eter m icroscope. C. - CLEANING CASTINGS - V a rio u s m ethods a r e u se d t o c l e a n c a s t i n g s depend in g on th e i r s i z e and sh ap e. A ll o f th e s e m ethods produce m ore o r le s s d u s t some o f w hich can be ta k e n c a re o f by ex h au st v e n t ila t io n s , o th e rs can n o t. The m ethods m ost commonly em ployed are? (a) P re lim in a ry C lean in g - C astin g s a re brought from th e moulding f lo o r d u rin g t h e n i g h t and d e p o s i t e d i n t h e C le a n in g Room, The f o llo w in g m o rn in g th e c o r e s a r e knocked o u t, t h e s p ru e s and g a te s a r e broken o f f and some s c r a tc h c le a n in g i s done. T h is work p ro d u ces c o n s id e ra b le d u s t e s p e c ia lly when th e sand and old c o re s a re sh o v e lle d th ro u g h th e p r a tin g in to th e c a r or b u c k e t below (3 ,4 5 5 ,0 4 0 p a r tic le s te n m icro n s or le s s per c u b ic fo o t o f a i r ) . Under th e Konimeter m icroscope ab o u t 70$ o f th e du st p a rtic le s appear an g u lar, c ry s ta llin e , th re e m icrons or le ss in s iz e j 20$ w ere rounded c r y s t a l l i n e , f iv e m icro n s in s iz e and about 5$ w ere s c a le - lik e semi opaque w ith a red d ish -b ro w n tin g e and over te n m icrons in size* Pulmosan R e s p ira to rs h a v e b e e n p r o v id e d b u t a r e n o t alw ay s worn by men d o in g t h i s w ork, NO a t te m p t h a s b e e n made to c o n tr o l d u s t from p re lim in a ry c le a n in g a lth o u g h some stu d y has been g iv e n to th e p ro v is io n o f a s p e c ia l a i r - t i g h t room w ith a g r a tin g f l o c r and a hopper underneath w ith a screw conveyor a t th e bottom to convey th e d eb ris to th e d isp o sa l c a r or bucket and th u s e lim in a te th e d u st-p ro d u cin g s h o v e llin g and h an d lin g . Under t h i s plan exhaust ducts with a series of outlets around the top of the hopper carry o f f th e d u st. A ir is a ls o in tro d u c e d in to th e room about a man's b re a th in g le v e l and .th e amount o f a i r ta k e n out is g re a te r th an th a t in tro d u ced so th a t a n eg ativ e p re sjifsure is m ain tain ed and a com plete a i r change is made about every th re e m inutes. (b) Tum blast - The Tum blast is a machine w hich com bines tum bling w ith a i r b l a s t in g . From 400 t o 1500 pounds o f c a s ti n g s a r e p u t in t o a drum w hich re v o lv e s a b o u t 10 RfM. They r u n fro m a b o u t 20 m in u te s t o f o u r h o u r s , d e p e n d in g upon th e ty p e o f a b la s t of $20 S te e l sh o t through th re e 5 /l6 inch n o zzles under an a ir p ressu re of 85 pounds p e r s q u a r e in c h , T h is m achine i s o p e r a te d b y t h r e e men, w ith a n a v e r a g e ^serv ice o f e i g h t y e a r s , f o r a p e rio d o f tw o and a h a l f h o u rs p e r man p er d ay , f i v e days a week, Pulm osan D ust r e s p ir a to r s a re provided b u t a re n o t alw ays worn. A te n -in c h ex h au st p ip e has b een in s ta lle d a t th e to p o f th e m achine and a s ix - in c h e x h a u s t p ip e o v e r t h e s c r e e n , The s u c t i o n on th e s e e x h a u s t p ip e s i s s a id t o be ab o u t 2 -1 /2 in c h e s w ater. Samples ta k e n d u rin g th e o p e ra tio n o f t h i s m achine a v e r aged 1,200,760 d u st p a r tic le s , ten m icrons or le ss in s iz e , per cubic fo o t w hich in d ic a te s th a t th e d u st c o n tro l measures w hich have been provided are g e ttin g r e s u lts alth o u g h th e re is s t i l l room fo r improvement. About 98$ o f th e d u st p a r tic le s ap p ear q u a r tz - lik e under th e Konimeter m icroscope} ab o u t 60$ a re fiv e m icrons or le s s in s iz e and a re an g u lar c r y s ta llin e in appearance} 40$ a r e te n m icrons or. over in s iz e , and r a th e r rounded in appearance. T here a r e a ls o a la rg e number o f m inute b la ck m e ta llic specks e n tir e ly to o sm all and numerous to co u n t a c c u ra te ly . (c) S ly Tumbling M ill - Cleans b ra s s c a s tin g s by a com bination of tu m b lin g and a i r - b l a s t i n g w i t h -$5 Sand B l a s t Sand and 85 pounds p e r s q u a r e in c h a i r p r e s s u r e . The M ill h o ld s fro m 100 t o 1500 pounds o f c a s t i n g s an d c l e a n s f i v e lo a d s a d ay . Two men , w ith an av era g e s e r v ic e o f 15 y e a rs , o p e r a te t h i s m i l l w hich ru n s a b o u t f i v e hours a day. They w ear Pulmosan D ust r e s p ir a t o r s and ro g g le s when opening th e m achine. T his M ill is hooded w ith an 8 -in c h exhaust pipe having a 2 -in c h w ater su ctio n , a lso a 1 0 -in ch exhaust pipe over th e sand sc re e n a t th e re a r o f th e m achine. Samples of d u st taken d u rin g th e o p e ra tio n of th e S ly Tumbling M ill had as high as 2,492,160 p a r tic le s te n m icrons or le s s in s iz e per cubic fo o t o f a i r and an average o f 1,393,344 p a r tic le s p er cu b ic foot. About 90$ of th e s e d u st p a r tic le s were rounded c r y s ta l lin e in ap p earan ce u n d e r th e K onim eter m icroscope and two m icrons o r le s s in iiz e ; 5$ were b la c k , opaque s c a le - lik e and 5$ were rounded c r y s ta llin e about fiv e A icrons in s iz e . (d) T um bling B a rre ls - 36" x 42" W hiting Tum bling B a rre ls remove sand from c a s t in g s . They h o l d from 1200 t o 1500 pounds o f c a s t i n g s p e r lo a d and r e v o lv e a t 10 RPM, The c a s tin g s a r e tum bled a b o u t two h o u rs w ith a b o u t 700 pounds o f o n e -in c h u n a n n e a l ed c a s t m a lle a b le ir o n s t a r s and ja c k s . An e x h a u s t sy ste m w ith a 6 - in c h p ip e th ro u g h th e tru n n io n h av in g a s u c tio n o f l - l / 4 in ch es w ater. T his su ctio n has been found in adequate to giv e th e d e sire d re s u lts consequently th e su c tio n is to be in creased to 4--in c h e s w a te r . Sam ples t a k e n d u r in g t h e o p e r a t i o n o f t h e Tum bling B a r r e l s had a n average of 1,348,032 dust p a rtic le s , te n m icrons or le s s in siz e per cubic fo o t of a i r . About 90$ o f th e se p a r tic le s were an g u lar c r y s ta llin e in appearance under th e K onim eter M icroscope and th r e e m icrons o r le s s in siz e ? about 10$ were rounded semi c r y s ta llin e , t e n m icrons in s iz e . There w ere a lso a few tria n g u la r-s h a p e d opaque m e ta llic p a r tic le s . Three men, w ith an average s e rv ic e o f tw elve y e a rs, o p erate th e s e tu m b lin g b a r r e l s e ig h t hours a s h i f t , f iv e s h i f t s a week. Pulmosan D ust P ro o f r e s p ir a to r s and goggles h av e been p ro v id ed b u t a re n o t alw ays worn. The t y p e o f T um b lin g B a r r e ls b e i n g u sed h a s b e e n condemned b y a m a jo r com pany because i t is im po ssib le to v e n tila te i t p ro p erly . The holes in th e end lin e r s c lo g up when th e b a r r e l s t a r t s re v o lv in g , th u s p r e v e n tin g c i r c u l a t i o n o f a i r th ro u g h th e b a r r e l . T h is c o n d i tio n h as been re m e d ie d , i n a new d e s ig n now on th e m a rk e t, b y th e use of two s h e ll s - an in n e r p e rfo ra te d and an o u te r s o lid s h e ll. B oth tr u n n io n s a r e h o llo w and a r e c o n n e c te d with t h e a i r chamber between the two sh ells. Air under p re s s u re i s in tro d u c e d th ro u g h one tr u n n io n and ex h au sted th ro u g h th e other*, J (e ) A ir - B la s tin g - C astin g s which can n o t be tum bled due to t h e i r s iz e and f r a g i l i t y a re cle a n e d by a i r - b l a s t i n g (85 pounds per sq u are in c h ) w ith m ix tu re o f ap p ro x im ately h a l f and h a l f sand and $40 S te e l G rit, S y racu se Core sand is used when a s p e c ia l f in is h is d e s ire d . There a re th r e e men, w ith an average s e rv ic e o f th re e y e a r s , on t h i s jo b who w ork 45 m in u te s o f e v e r y h o u r, e i g h t h o u rs a s h i f t , f o r one --6 3" w h ile w earing a S ly S a n d -b la st Helm et su p p lie d w ith o u tsid e fre s h a i r p ro v id ed by a s p e c ia l b lo w er used f o r th a t p u rp o se only* Sam ples ta k e n in s id e th e room w h ile a c a s tin g was b e in g a i r - b l a s t e d had an av e ra g e o f 3 ,7 3 8 ,2 4 0 d u s t p a r t i c l e s te n m icro n s o r le ss per cubic fo o t o f air# About 80$ o f th e se d u st p a r tic le s were sh arp ly angu l a r c r y s ta llin e in appearanoe under th e K onim eter m icroscope and th re e m icrons or le s s in s iz e j 20$ were rounded q u a r tz - lik e c r y s ta ls about te n m icrons in size* There w ere a ls o a few r u s t - l i k e s c a le s and a la rg e number o f b la c k m e ta llio p a r ti c le s to o m inute and to o numerous to be counted a c c u ra te ly . The s i l i o o s i s h azard of th is opera tio n could be g re a tly reduced by th e use o f s te e l ab rasiv es ex clu siv ely , , (f) Rough Snagging Wheels - These m achines a re u sed fo r rem oving p ro je c tio n s such as sp ru e s, p a r ts an d .g ates from c a s tin g s . There a re two ty p e s o f th e s e w heelst t h e DOUBLE END u s in g e i t h e r 1 9 - 1 /2 " x 3" C arborundum and " V i t r i f i e d o r 24" x 2 - 1 / 2 " Redmanol ( B a k e l i t e b o u n d ) W heelsj and t h e HORIZONTAL DISC G r in d e r h a v in g a 50" d ia m ete r v i t r i f i e d wheel# These w heels a re u sed by seven men h av in g an av erag e s e rv ic e o f n in e h o u rs p er s h i f t , f iv e s h i f t s p er week. Each w heel i s hooded and has a fo u r-in ch su c tio n pipe. There is an e ig h t-in c h su c tio n pipe on th e H o rizo n tal G rinder. G oggles and r e s p ir a to r s a re p ro v id ed b u t th e l a t t e r a re n o t alw ays worn w ith th e e x c e p tio n o f t h e men on t h e H o r iz o n ta l G rin d e rs . V i t r i f i e d w h e e ls a r e r u n a t a s lo w e r s p e e d (1800 RFM) t h a n t h e B a k e l i t e Bound W heels w hich o p e r a t e a t 3400 RFM* Sam ples ta k e n d u r in g th e o p e r a t i o n o f t h e Rough S h ag g in g W heels h a d t h e f o l low ing dust co n c e n tra tio n s. Double End Snagging W heelst Average D ust from V itr if ie d W h e e ls ...... " 11 " Carborundum " . . . . . . " " " B a k e lite Bound W heels. . 3 , 6 5 3 , 2 8 0 p a rtic le s per cubic fo o t . . . 3,322,820 " " "' " .2,662,080 " " " " H o rizo n ta l P iso G rinder? A verage D ust from 50" V i t r i f i e d W h e e l,... .* 2 ,1 2 4 ,0 0 0 p a r ti c le s p er cu b ic fo o t The av erage d u s t produced by a l l th e Rough S nagging Wheels was 2 ,3 2 2 ,8 2 0 p a r t i c l e s , te n m icrons or le s s in s iz e , per cubic fo o t o f a ir . About 80$ o f th e d u st p a r tic le s from th e v i t r i f i e d w heels appeared b la c k angu l a r opaque under th e K onim eter m icroscope and two m icrons or le s s in s iz e j 20$ an g u lar c r y s ta llin e -about one m icron or le s s . There were a ls o a la rg e number o f b la c k m inute p a r ti c le s to o sm all and numerous to c o u n t. The d u s t p a r ti c le s from th e H o ri z o n ta l ( V itr if ie d ) w heel were ap p ro x im ately 90$ an g u lar, c r y s ta llin e and 10$ b la c k opaque. A ll o f th e s e p a r tic le s w ere ab o u t two m icrons or le s s in size* About 60$ o f th e d u st p a r ti c le s from th e B a k e lite bound w heel were b la c k a n g u lar two m icrons or le s s in s iz e j 25$ were an g u lar c r y s ta llin e , le s s than one m icron in s iz e and about 15$ were rounded c r y s ta llin e about fiv e m icrons in s iz e , (g) F in e Snag g in g and P o lis h in g W heels - These w heels g rin d o f f sm all p r o je c tio n s and remove r u s t from sto c k w hich has b een in s to ra g e . There a re th re e ty p es? DOUBLE 4" x 14" POLISHING EMERY WHEELS - W h eels a f t e r b e in g made u p a r e d ip p e d i n g lu e and then rolled in Alundum Grinding G r a in , s i z e s 60, 80 and 120 m esh. DOUBLE DISC GRINDERS - 36" d i s c s c o v e re d w ith if/46 C a s t I r o n G ra in o r S i l i c o n C a rb id e ( a n e l e c t r i c f u r n a c e p r o d u c t) and WIRE SCRATCH BRUSHES made up w ith f o u r 12" s e c t i o n s , /x h a u s t hoods w ith a su c tio n of from th re e to fiv e inches w ater, have been in s ta lle d - o n t h e P o l i s h i n g W heels and D isc G r in d e r s . T h e re i s NO hood on th e W ire S c r a tc h B ru sh es. T hese w heels a r e used by fo u r men w ith an a v e ra g e s e r v ic e o f two y e a r s . They wear goggles and gloves b u t no re s p ira to rs # Samples tak en a t face le v e l d u rin g th e o p eratio n of th is equipm ent had th e fo llo w in g av erag e dust co n ce n tratio n s? ft -64- f D ust P ro d u c e d b y 3611 D isc G r in d e r ................... 1,416,000 p a r tic le s per cu b ic foot f $ II I! II -^gll W ire S c r a tc h B r u s h . . . . . . 736 ,3 2 0 " " " " r II II II ^11 x 14" P o l i s h i n g W h e e ls. . 4 8 1 ,4 4 0 " " " I These c o m p a ra tiv e ly low d u s t co u n ts i n d i c a t e t h a t th e d u st c o n tro l m e asu re s w hich t h av e b een p ro v id e d are e i t h e r e f f e c t i v e o r t h e d u s t p a r t i c l e s produced a r e ov er 30 m icro n s in s iz e and were th u s f i l t e r e d o u t b y th e K onim eter f i l t e r . Under th e mi E cro sco p e d u s t p a r tic le s from th e P o lis h in g W heels appeared a l l round c r y s ta l lin e and ab o u t one m icro n in s iz e . About 40$ o f th e d u s t p a r ti c le s produced b y th e Double C Disc G rin d er w ere sh arp ly a n g u la r, opaque ab o u t th re e m icrons o r le s s in s iz e j 60$ w ere le s s a n g u la r c r y s ta llin e about one m icron in s iz e . The d u st p a r ti c le s produced E by..the. W ire S c ra tc h Brush w ere a l l rounded, c r y s ta llin e and about one m icro n in s iz e . T h e re w e re no m e t a l l i c p a r t i c l e s i n an y o f t h e sam p les exam ined. Few e x h a u s t hoods I h ave b e e n i n s t a l l e d on W ire S c r a tc h B rushes b e c a u se i t h as b e e n g e n e r a lly assum ed th a t th e s e b ru sh es did n o t produce any d u st. This assum ption, however, is u n tru e as I one sam ple from a wire b ru sh a t a S outhern R e'finery had as h ig h as 6 ,6 8 3 ,5 2 0 p ar ti c le s te n m icrons or le s s per cubic fo o t o f a i r . r (h) Cone G rinding W heels - These w heels a re o p erated w ith com pressed a i r and E a re used to do m isc ellan eo u s g rin d in g on c a s tin g s by fo u r men, w ith an av era g e s e r v ic e o f tw elv e y e a r s , ab o u t two hours a day on an average. The cones a r e 5 - l/4 " x E 3 -1 /4 " v i t r i f i e d and produce an average d u st o f 1,869,120 p a r tic le s te n m icrons or le s s per cubic fo o t of a ir . About 80$ of th e se p a rtic le s are sharp an g u lar c ry s ta l E lin e , In appearance under th e K onim eter m icroscope they a re fiv e m icrons or le ss in s iz e j 20$ a re round opaque b u t n o n -m e ta llic in appearance and fiv e m icrons o r over I in s iz e , , T here a r e no hoods over th e s e w heels and th e o p e ra to rs wear no r e s p ir a to r s . I A v e ra ge D u s tin e s s o f C le a n in g Room A i r - A s e r i e s o f f i v e s a m p le s w ere -ak en b etw ee n 9*30 and 9 ;4 0 A.II. t o d e te rm in e t h e av era g e am ount o f d u s t i n th e a i r f o f th e c l e a n i n g room w h ile th e v a r io u s c l e a n in g o p e r a tio n s w ere in f u l l b l a s t . An o t h e r s e r i e s o f f i v e sam p les w ere ta k e n a b o u t 3*30 PM, i n t h e a f t e r n o o n a f t e r th e r room had b e e n g iv e n i t s r e g u la r c le a n -u p . T h e re was q u ite a d if f e r e n c e in th e am ount o f dust in th e a i r during th e m orning (2 ,1 6 6 ,4 8 0 p a rtic le s te n m icrons or le ss per r cubic fo o t o f a i r ) and d u rin g th e a fte rn o o n tow ard th e c lo s e o f th e s h i f t (338,272 p a r tic le s p e r cubic fo o t). About 95$ o f th e d u st p a r tic le s in th e evening samples r w ere a n g u la r c r y s t a l l i n e i n a p p e a ra n c e and a b o u t two m icrons in s iz e . T h ere were a few la r g e sem i-o p aq u e o r s c a l e - l i k e ..p a r t i c l e s a b o u t 20 m icro n s in s i z e . About 98$ c o f th e d u st p a r tic le s in th e m orning sam ples w ere an g u lar c r y s t a l l i n e two m icrons o r le s s in s iz e and about 2$ were round, c r y s ta llin e over fiv e m icrons in s iz e , t A sam ple o f d u s t from to p o f one o f th e la rg e r E x h au st Ducts in th e c e n te r b o f th e c le a n in g room was g iv e n a p e tro g ra p h ic ex am in atio n b y th e U.S. B u reau o f M ines Experim ent S ta tio n a t P itts b u rg h , P en n sy lv an ia and found to c o n ta in 40$ Q uartz G (S iO g), 20$ Clay M ineral n o t co m p lete ly id e n tif ie d j 40$ opaque, e Dc - CORE MAKING - A l a r g e num ber o f c o r e s a r e made b y th e Demmler A ir Ope ra te d Core M achine which uses a m ix tu re of tw o -th ird s sea san d , o n e -th ird r iv e r sand n and one g a llo n c o re o il per 60 g a llo n s sand. There are th r e e so u rces o f d u st in th e o p e ra tio n o f th i s machine? n (1 ) S h o v e llin g Sand to f i l l th e M achine H o p p e r.,1 ,0 1 9 ,5 2 0 p a r tic le s p e r cubic fo o t n (2) Blow ing o u t C o r e - b o x e s . , . . . . , , . . , . . . . . . . . . , , 736,320 " " " " |t '`^ 4 ' ( 3 ) B lo w in g sa n d in to t h e C o r e - M o u l d s . , . . . . . , . . 7 5 5 ,2 0 0 11 11 " " c '''.'Ah . / About 98$ o f the d u s t p a r tic le s from blow ing out th e core boxes a re dark, c opaque i n a p p e a r a n c e and a b o u t one m ic ro n i n s i z e . The d u s t p a r t i c l e s from b lo w in g c sand i n t o th e c o r e m oulds o r e a n g u la r c r y s t a l l i n e l e s s th a n one m ic ro n i n s i z e . -65- Cores a r e "sm oothed up" a f t e r b ein g baked in th e co re oven by s c ra tc h in g o f f th e rough edges w ith an. o ld hacksaw b la d e . This o p e ra tio n produces an av erag e of ^906,240 dust p a r tic le s te n m icrons o r le ss in s iz e per cubic fo o t of a i r . About 98$ J o f th e s e p a r tic le s a re a n g u la r, c r y s ta llin e in appearance under th e Konim eter m i croscope and a re le s s th a n one m icron in siz e . E, - SEPARATION OF BRASS FOUNDRY SKIMHINGS - A S t e i n l e i n S e p a r a t o r , r e v o lv in g a b o u t 25 RPM, s e p a r a t e s b r a s s from a b o u t 100 pounds o f skim m ings a n h o u r. The se p a ra to r has a 4 -in ch exhaust d u ct to a 1 2 -in ch fan w hich produces a su c tio n of about four in ch es w a te r. Samples ta k en d u rin g th e o p e ra tio n of th is m achine had an average o f 1,231,920 p a r tic le s te n m icrons or le s s per cu b ic fo o t o f a i r . About 95$ o f th e d u st p a r tic le s in sam ples ta k e n above th e charging ch u te appeared opaque a n g u la r b lack in c o lo r under th e K onim eter m icroscope and w ere le s s th a n one m icron > in s iz e . About 80$ o f th e d u st p a r tic le s in sam ples from th e tru n n io n w ere more c r y s t a l l i n e and rounded in a p p e a ra n c e and l e s s th a n one m icron in s i z e . T his was a l s o t r u e o f th e sam p les ta k e n in f r o n t o f t h e m achine w here t h e s l a g d ro p s down i n t o a b u ck et. The d u s t p a r tic le s in sam ples from th e m etal b e in g d isch arg e d from th e m achine were about 50$ m e ta llic in appearance about 50$ an g u lar c r y s ta llin e . Both c r y s t a l l i n e and opaque p a r ti c le s w ere about two m icrons o r le s s in s iz e . S ix men, w ith an average s e rv ic e o f seven y e a rs , ta k e tu rn s o p e ra tin g th i s m achine which ru n s a b o u t two hours per day on an a v e ra g e , X - MASON'S OPERATIONS I . - TEARING OUT STILL FIRE BOXES - Two men w ith a n a v e r a g e s e r v i c e o f t e n y e a rs , spend two days a m onth on an average te a r in g out s la g -c o v e re d bottom s o f c ra c k in g c o i l fu rn a c e f i r e boxes. T em perature in s id e f i r e box i s ab o u t 85F, The b o t toms w hich a r e composed o f f i r e b r ic k a re broken up w ith "B u ll P o in t" Pneum atic c h is e ls . Samples ta k e n in s id e th e f i r e box w h ile th i s work was in p ro g re ss had d u s t co n ce n tratio n s as high as 1,019,520 p a rtic le s te n m icrons o r le s s per cubic foot of a i r . These p a r tic le s w ere g la ss y sh a rp ly c r y s ta l lin e in appearance u n d er th e Koni m eter m icroscope. About 90$ were fiv e m icrons or le ss in s i z e and 10$ w ere over te n m ic ro n s. The l a r g e r p a r t i c l e s w ere sem i-opaque. There w ere a ls o a l a r g e number o f round b lack opaque p a r tic le s about one m icron o r le s s in s iz e . A fter th e bottom s had been broken up by th e pneum atic c h ise ls th ey a re sh o v elled out through th e f i r e box door and th e n r e s h o v e lle d in to tr u c k s to b e h a u le d away. This o p e r a tio n n a t u r a l ly produces more d u st th a n th e b re a k in g up in s id e th e f i r e box. A lthough no wind was blow ing samples ta k e n a t fa c e le v e l, d u rin g th e sh o v e llin g and lo ad in g had dust con c e n tra tio n s as high as 2,435,520 p a rtic le s te n m icrons or le s s per cubic fo o t of a i r and a n a v e ra g e o f 1 ,3 4 5 ,2 0 0 , G o g g le s b u t no r e s p i r a t o r s w e re w orn b y t h e workmen,I. I I . - CHIPPING OR CUTTING CONCRETE - A l a r g e number o f em ployees w ith an av erag e serv ice o f th re e y e a rs , spend a t le a s t te n per cent, o f th e ir tim e dism ant lin g o r c u ttin g c o n c re te s tr u c tu r e s w ith pneum atic c h is e ls in th e rem oval of old fo u n d atio n s, c o n c re te su p p o rts and b lo c k s and in c u ttin g h o le s in w alls and flo o rs . Samples taken d u rin g th e c u ttin g o r ch ip p in g o f c o n c re te had as h ig h as 6,910,080 p a r tic le s te n m icrons or le s s in s iz e per cubic fo o t and a g e n e ra l average of 1,591,051 p a rtic le s per cu b ic fo o t. A ll of th e se dust p a r tic le s a re s lig h tly angular c r y s ta l lin e in appearance u n d er th e Konim eter m icroscope. About 85$ o f th e dust p ar t i c l e s '-ere fiv e m icrons o r le s s in s i z e ) 10$ betw een f iv e and te n m iorons and about 5$ o v e r te n m iorons in s iz e . In many cases n e ith e r goggles or r e s p ir a t o r s were worn by t h e workmen. R e g a rd le s s o f th e r a t h e r low d u s t c o u n ts fo u n d , men engaged in c h ip ping or c u ttin g co n crete should wear co n crete due to th e high s ili c a co n ten t in th e ysual aggregate used in co n cre te. if?? I I I . - CHIPPING MORTAR FROM BETV/EEN BRICK - C h ip p in g M o rta r w ith p n eu m atic ch is e l s from betw een b ric k s in w a l ls o f s tr u c tu r e s p r e p a ra to ry to w e a th e r-p ro o fin g is a p a r tic u la r ly d u sty o p e ra tio n . Samples tak en d u rin g th is work had d u s t c o n c e n tra tio n s as high as 20,956,800 p a r tic le s te n m icrons o r le s s p er cubic fo o t o f a i r and a '^ g en eral a v e ra g e o f 1 3 ,8 4 8 ,4 8 0 p a r t i c l e s p e r c u b ic f o o t. A l l o f t h e s e p a r t i c l e s w ere 'angular c r y s ta llin e in appearance under th e K onim eter m icroscope and about s ix m i cro n s or le s s in s iz e . There were a lso a c o u n tle ss number o f m inute re d d ish -g ra y p a r tic le s . This work was done by an o u ts id e c o n tra c to r whose em ployees wore goggles but no dust re s p ira to rs , IV. - CRUSHING FIRE BRICK - F i r e b r i c k s a r e c r u s h e d i n a b e l t - d r i v e n W illia m s o r a M otor-driven S tu rte v a n t B rick Crusher so th a t 80$ w ill pass th ro u g h a 3/8" or a 150-mesh s c re e n - much o f i t i s powdered d u rin g th e c ru s h in g . This m a te r ia l is th e n mixed w ith f i r e c la y , crushed asb e sto s and cem ent to make "G a n ister" w hich is . used in tube sh eet lin in g s , packings or as m ortar in b u ild in g f i r e boxes o f furnaces. Samples ta k e n d u rin g ~ th e b ru sh in g o f : f i r e b r ic k had d u s t c o n c e n tra tio n s as h ig h as 11,564,560 p a r tic le s te n m icrons or le s s in s iz e per cu b ic fo o t and a general average o f 2 ,5 6 2 ,9 6 0 p a r t i c l e s p e r c u b ic fo o t, C ru sh in g new f i r e b r ic k p ro d u ces ab o u t s ix tim es as many d u st p a r t i c l e s (4 ,3 7 5 ,7 3 3 p e r cubio fo o t) a s is produced when c ru sh in g o ld , used f i r e b r ic k (73 6 ,3 2 0 p a r tic le s p e r cu b ic f o o t) . Under th e konim eter m i c ro sc o p e ab o u t 94$ o f th e d u s t p a r t i c l e s produced b y c r u s h in g new f i r e b r ic k a p p e a r an g u la r c r y s ta l lin e , one m icron or le s s ill s iz e j a b o u t 5$ a re opaque over te n m i cro n s and ab o u t 1$ a r e d a rk opaque, s c a le - lik e ab o u t f i v e m iorons in s iz e . The d u s t pa r t i c l e s from c ru s h in g o ld used f i r e b ric k are more rounded c r y s ta l lin e in ap p earan ce and a r e a b o u t f i v e m ic r o n s o r l e s s i n s i z e . An a n a l y s i s o f Alamo F i r e - c l a y B r ic k , w hich i s commonly u sed and was th e new u n u sed f i r e b r i c k b e in g c ru sh e d a t th e tim e our sam ples were ta k e n , su p p lie d by th e m an u factu rers (H arbison-W alker R e fra c to rie s Company) r e p o r ts t S 1 C # 0 9e o>00 A lu m in a and T i t a n i a ..........,,. F e r r i c O x id e. ........................ LilU0 . eae M a g n e s ia ........................... .. A l k a l i e s . ...................................... 51. 8 p er 45, 4 11 1 . 1 11 0. 5 tl 0. 3 11 1 . 1 11 c e n t. It 11 11 11 11 F ir e b r ic k i s crus'hed by two men a s s ig n e d from th e L abor D epartm en t, th e a v e r a g e s e r v i c e o f t h e s e men i s a b o u t 14 y e a r s . Two t o t h r e e to n s a r e c r u s h e d p e r day. The t o t a l le n g th o f ex p o su re p e r month depends upon th e demand fo r c ru sh e d f i r e b r ic k and w ill v a ry from a g e n e ra l av era g e o f f i f t e e n h o u rs p e r man p e r m onth to as much a s tw e lv e h o u rs a w eek. G oggles and M, S, A. Comfo d u s t r e s p i r a t o r s a r e worn, V. - SHAPING FIRE BRICK ON EMERY WHEEL - F i r e b r i c k a r e g ro u n d t o a s p e c i f i e d s h a p e and s i z e on a 2" x 24" C arborundum ( G r i t 1 6 , G rad e 1 , Bond 6C) W heel w hich r e v o lv e s 900 RPM. T his w h e e l i s a lm o st c o m p le te ly e n c l o s e d b y a hood w h ic h h a s a 4 in c h d u c t to a 2 4 - in c h m o t o r - d r i v e n f a n o p e r a t i n g a t 1750 RPM, , b u t t h i s e x h a u s t i s e v id e n tly inadequate as sam ples taken w hile rounding o ff th e edges of a f i r e clay fu r nace block had a d u st c o n c e n tra tio n as h ig h as 4,078,080 p a r tic le s te n m icrons or l e s s in s iz e p e r cu b ic fo o t o f a i r . The g e n e ra l a v e ra g e was 2 ,0 0 1 ,6 5 8 p a r t i c l e s p er cubic foot. A ll of th e se d u st p a rtic le s were s lig h tly an g u lar and s lig h tly opaque in a p p e a ra n c e u n d er th e m ic ro sc o p e and f iv e m icro n s o r l e s s in s i z e . One man w earin g g o g g le s and a M, S.A, Comfo r e s p i r a t o r , w i t h a b o u t 15 y e a r s s e r v i c e , sp e n d s a n a v e ra g e o f a b o u t two days a month sh a p in g f i r e b r ic k and b lo c k s on t h i s w heel, V I. - DISMANTLING MASONRY - D is m a n tlin g M asonry s t r u c t u r e s su c h a s /a n d s t i l l s e t t i n g s is a v e ry d u sty o p e ra tio n b u t was n o t in c lu d e d in t h i s as th e r e was no work o f t h i s ty p e in p ro g re s s a t any o f t h e p la n ts a t th e survey. old b o ile r d u st study tim e of our -6 7 - XI - WOODWORKING OPERATIONS Woodworking o p e r a tio n s , as perform ed in c o n n e c tio n w ith th e r e f in in g o f pe troleum produots and a s s o c ia te d a c t i v i t i e s , a re used in th e p ro d u ctio n o f p a tte r n s , box sh o o ts, c o n ta in e r s , and c o n s tr u c tio n or m ain ten an ce work. These woodworking o p e ra tio n s produce m ore o r le s s d u s t which is la r g e ly o rg a n ic and a lth o u g h i t may have some s p o re s and h av e an a l l e r g i o e f f e o t on some in d iv id u a ls , i t i s n o t c o n s id e r ed h a rm fu l, Mr, D. H a r r in g to n o f th e U. S. B u re a u o f M ines a d v is e s t h a t t h e U, S. De partm ent of L abor in a re c e n t b u l l e t i n in d ic a te t h a t w orkers b re a th in g wood d u s t a re f a r more d e f in i te l y a f f l i c t e d w ith tu b e rc u lo s is th a n th e g en era l 'rim o f in d u s tr i a l w o rk e rs. I n l a r g e q u a n t i t i e s , how ever, wood d u s t b e lo n g s in t h e ''n u is a n c e " c l a s s and may a l s o be an e x p lo s io n h a z a rd A. - BOX SHOOK MANUFACTURE - A ll p in e lu m b er u s e d i n th e m a n u fa c tu re o f box shooks i s " k i l n - d r i e d " and a l l gum lu m b er i s " a i r - d r i e d " . Men work e i g h t h o u rs a s h if t, fiv e s h i f t s a week. (a ) Resawing - Band saws, tw e n ty -fiv e f e e t fo u r in c h e s in circ u m fe re n c e , re saw fo u r-q u a rte r and f iv e - q u a r te r lum ber in to 3 /8 -in c h and l/2 - in e h shooks re s p e c tiv e ly . Samples ta k e n d u rin g th is resaw ing had an average d u st c o n c e n tra tio n of 155,760 p a r t i c l e s te n m icrons o r le s s per cu b ic fo o t o f a i r when saw ing p in e and 9 9 6 ,8 6 4 p a r t i c l e s p e r c u b ic f o o t when saw in g gum. T h ese low c o u n ts i n d i c a t e t h a t th e exhaust and d u st c o lle c tin g system which has been p ro v id ed is fu n c tio n in g . T his exhaust system in c lu d e s hoods over each saw w ith 8 -in c h d u c ts to a b e l t d riv e n fan w ith f i v e - f o o t b la d e s r e v o lv i n g 3500 RFM, A b o u t 60$ o f t h e d u s t p a r t i o l e s i n s a m p le s taken w hile resaw ing p in e were c r y s ta llin e , r a th e r g la s s - lik e in appearance - prob a b ly r e s i n - u n d er t h e K onim eter m icroscope and o v er te n m icrons in s i z e j 40$ .were round w ith rough edges gray and opaque, fiv e m icrons or le s s in size. About 80$ of t h e d u s t p a r t i c l e s fro m c u t t i n g gum lum ber w e re ro u n d c r y s t a l l i n e sem i-o p aq u e i n a p p e a r a n c e , f i v e m ic r o n s o r l e s s in s i z e j 20$ w e re o v e r f i v e m ic ro n s in s i z e . Gum lum b e r is resaw ed only a b o u t fo u r days a month. (b ) R ip s aw ing - Rip saw s, 14 in c h es in d ia m e te r c u t end 3 from f o u r - q u a r te r gum lu m b er. An e x h a u s t s y ste m h a s b e e n p r o v id e d w ith a hood o v e r ea c h saw and f o u r in c h m e ta l d u c ts t o a b e l t - d r i v e n f a n w ith s i x - f o o t b l a d e s r e v o lv in g 3500 RFM, S am ples thken du rin g t h i s o p e ra tio n had an average d u st c o n c e n tra tio n o f 169,920 p a r tic le s te n m icrons or le s s p e r cubic fo o t of a ir . A ll o f th e s e p a r tic le s were an g u lar c ry s t a l l i n e sem i-opaque i n ap p earan ce under th e K onim eter m icroscope and about th r e e mi crons iii size, ( c ) C u t-O ff S aw ing - Saw f o u r - q u a r t e r lu m b er t o make box en d s. A bout 85$ o f t h e tim e gum lu m b e r i s sawed, an d 1 5 $ p in e lu m b e r i s saw ed. Sam ples ta k e n w h ile saw in g gum lu m b er h ad a n a v e r a g e d u s t c o n c e n t r a t i o n o f 8 7 7 ,9 2 0 p a r t i o l e s t e n m io ro n s o r le s s p er cubic fo o t o f a i r . About 50$ o f th e s e p a r ti c le s were round c r y s ta l lin e sem i opaque, gray in o o lo r and from fiv e to te n m icrons in s i z e j 50$ were s li g h t l y angu l a r c r y s ta llin e in ap p earance under th e K onim eter m icrosoope and th re e m icrons or le s s in s iz e . T h ere w ere a l s o s e v e r a l v e ry sm a ll b la c k sp eck s. The low d u s t c o u n t in d i c a te s th a t e i th e r th e p a r tic le s were m o stly over 30 m icrons in s iz e and were th u s f i l t e r e d o u t b y th e p o r c e l a in f i l t e r o r t h a t th e e x h a u s t sy ste m was e f f e c t i v e , (d) P lan in g - P lan ers or double s u rfa c e rs re s u rfa c e th e fo u r-q u a rte r and fiv e q u a r t e r lu m b er t o g iv e i t t h e p r o p e r f i n i s h . T h e re i s a n e x h a u s t hood o v e r e a c h ma chine w ith an e ig h t-in c h m etal duct to a b e lt-d riv e n fan w ith six -fo o t blades rev o lv in g 3500 RFM. S am p les ta k e n d u r in g th e o p e r a t i o n o f p l a n e r s o r d o u b le s u r f a c e r s had a g en era l average d u st c o n c e n tra tio n o f 509,760 p a r tic le s te n m icrons or le s s p er cu b ic f o o t o f a i r when p la n in g p in e lum ber and 415,360 p a r ti c le s p er cu b ic fo o t when p la n in g gum lu m b er. P a r t i c l e s o f d u s t p ro d u c e d w h ile p l a n in g p in e lu m b er w ere fiv e m icrons o r le s s in s i z e j 25$ were la r g e r th a n two m icrons and r a th e r opaque. D u st p a r t i c l e s fro m p la n in g gum lum ber w ere ro u n d o p aq u e i n a p p e a ra n c e an d one m iro n or le ss in size, w D u stin e ss o f Shook F acto ry A ir - A s e r ie s of fiv e sam ples w ere ta k e n a t fiv e s tra te g ic p o in ts to determ ine th e average d u st co n c e n tra tio n of th e fa c to ry a ir . These sam ples gave an av erag e c o n c e n tra tio n o f only 141,600 d u st p a r ti c le s te n mi cro n s or le s s p e r cubic fo o t o f a i r which in d ic a te s th a t e ith e r th e m ajor p o rtio n o f th e d u s t i s o v e r 30 m icrons in s iz e o r t h a t th e v e n t i l a t i o n system i s p ro v in g e ffe c ti v e , The l a t t e r is probably th e more lo g i c a l e x p la n a tio n alth o u g h th e e x c e lle n t h o u s e k e e p in g i s u n d o u b te d ly a n im p o r ta n t f a c t o r . A b o u t 98/2 o f t h e d u s t p a r t i o l e s i n th e fa o to ry a i r sam ples w ere s lig h tly an g u lar c r y s ta llin e in appearance under th e K o n im e ter m ic ro s c o p e and a b o u t f i v e m ic ro n s o r l e s s i n s i z e j 2% w ere ro u n d , opaque d a rk g ray i n c o l o r and two m icro n s o r l e s s in s iz e . B, - BELT SANDERS, SAND DISCS AND SPINDLES OR CYLINDERS - T h is eq u ip m e n t i s used fo r " s q u a rin g up" and sm oothing s u rfa c e s o f wooden p a tte r n s , o le a n in g and fin is h in g b a rre l-h e a d in g and sta v e s and g en eral m ill work in th e C arp en ter Shops, S a n d e rs a r e a n o t o r i o u s s o u r c e o f f i n e wood d u s t s . They a r e a l s o c o n ta m in a te d w ith an a p p re c ia b le amount o f s i l i c a , i f a san d -ty p e o f a b ra siv e is used, co n seq u en tly e i t h e r hoods f o r th e m ach in es o r r e s p i r a t o r s f o r th e men engaged i n o p e r a tin g th e s e m a c h in e s s h o u ld b e p r o v id e d . We a p p r e c i a t e t h a t i t i s r a t h e r d i f f i c u l t t o p r o p e r ly hood a s a n d e r to p re v e n t th e f in e d u s t b ein g c a r r ie d around by th e a b r a s iv e member, p a r t i c u l a r l y d is o sa n d e rs. Our a t t e n t i o n h as b een c a lle d to a case w here a man en-. gaged in th e use of sanders su ffered re c u rrin g re s p ira to ry illn e s s and u ltim a te ly d eath from pneum onia. His a tta c k s o f il l n e s s seemed to c o r r e la te w ith extended use of th e sanders. (a) B e l t S a n d e rs - An 8" x 2 8 -1 /2 f t . B e l t S a n d e r ( L ig h tn in g A d alo x C lo th l - l / 2 - 40 X G 'rit N orton A b ra s iv e s ) runs on an av e ra g e o f two h o u rs p e r day and i s used by e ig h t d i f f e r e n t men w ith an average s e rv ic e o f f if t e e n y e a rs . Samples ta k e n w hile f in is h in g #1 Pine lum ber had a d u st c o n c e n tra tio n as high as 15,5 1 9 ,3 6 0 p a r t i c l e s te n m icrons o r le s s per cubic fo o t o f a i r and a g en eral av erag e o f 3,443,712 p a r tic le s per cubic fo o t. About 0% of th e se p a r tic le s were an g u lar c r y s ta llin e in ap p earan ce under th e K onim eter m icroscope and fiv e m icrons or le s s in s i z e j 5% were over fiv e m icrons in s i z e j 5% were opaque s c a le - lik e , te n m icrons or le s s in s iz e . T here was no hood o v er th i s sa n d e r and th e d u s t produced was throw n in to th e shop a ir, A 6 in . x 18 f t . B elt Sanding m achine ($3 P ro d u ctio n C loth M innesota M ining Company) ru n s on av era g e from fo u r to s ix h o u rs a week and is used by fo u r d i f f e r e n t men, w ith an av erag e s e rv ic e o f fo u r y e a rs. T h is work was fo rm erly done by hand on a la th e w ith sand p ap er. Samples ta k e n w h ile f in is h in g th e o u tsid e o f a b a r r e l had an av erag e d u st c o n c e n tra tio n of 481,440 p a r tic le s te n m icrons or le s s p er cubio fo o t. T hese p a r ti c le s were la rg e ly an g u lar c r y s t a l l i n e in -ap p e aran ce u nder th e Koni m e te r m ic r o s c o p e . About 5C$ w ere f i v e m ic ro n s o r l e s s , an d 50% w ere o v e r f i v e m i crons in siz e , (b) Sand D isc s or W heels - T h ese d i s c s r u n fro m 40% t o 6 0 / o f t h e tim e and a re u s u a lly used by everybody in th e shop in w hich th e y a re lo c a te d . Sam ples ta k e n during the operation of sand discs or wheels had the following dust concentrations? -6 9 - No. S iz e (D ia. ) A brasive Used Work B eing Done I 7" # 2 4 Sand C leaning P ap er Minn, h e a d s M in in g Co. F in is h e d B arrels II 24" # 1 -1 /2 Gar S q u arin g n e t P ap er. Wood Minn. Min P a t t e r n _ in g Co, I I I 30" IV 30" #40 G rit on B ris to l Board, G ard n er Ma c h in e Co, #2 G arnet N et Back. G ardner M achine Co, Sm oothing o ff Pat te rn S q u a rin g Wood P a t te rn P a rtic le s Per Cubic Foot 604,160 623,040 1 ,9 2 5 ,7 6 0 3 ,6 2 4 ,9 6 0 C h a ra c te ris tic s of Dust P a r tic le s (S izes and P er centages E stim ated) t A ngular c r y s ta llin e about 50$ fiv e m icrons o r le s s and 50$ la r g e r th an fiv e m icrons. About 85$ angular cry s t a l l i n e two m icrons . or le ss ; 5$ q u artz-lik e rounded a b o u t 10 mi crons in size, About 90$ an g u lar crys t a l l i n e th re e m icrons o r le s s j 10$ opaque an g u lar one m icron in s iz e . About 98$ sem i-opaque, sa n d -lik e , one m icron or le s s , 2$ opaque 5 m icrons o r over in s iz e . The sand d is c in No, I was u sed in a w e ll v e n t i l a t e d c a b in e t c o n n e c te d to a 48" m otor d riv e n fa n by a 7 -in c h d u c t. The men wore g o ggles and "Comfo" r e s p ir a t o r s . . The san d w h eels i n No I I and No I I I h ad hoods w ith a b o u t 3 ~ l/2 in c h e s w a te r s u c tio n co n n ected to a 24" m o to r d riv e n fa n by 4 -in c h d u c ts . The men wore n e i t h e r g o g g le s n o r r e s p i r a t o r s . The w h eel i n No. IV had a n e x h a u s t hood w ith a 6 in c h d u c t c o n n e c te d t o a 2 4 - in c h d u c t w hich i n t u r n was c o n n e c te d w ith a 3 6 - in c h mo to r driven fan. (c) Sand Sp in d le s o r C y lin d e rs - Sand s p in d le s o r c y l in d e r s a r e used on an a v e r a g e o f a b o u t tw o h o u rs p e r man p e r day. No hood o r s u c t i o n e x h a u s t h a s b e e n p ro v id e d f o r t h i s eq u ip m en t. Men u s in g i t do n o t w ear g o g g le s o r r e s p i r a t o r s a lth o u g h th e dust p a r tic le s produced a re more an g u lar in appearance th a n th o se produced by sand d isc s or w heels. Samples ta k e n d u rin g th e o p e ra tio n of Sand S p in d les or C y lin d e rs had th e f o l low ing d u s t c o n c e n tra tio n st S iz e (Dia. ) A brasive Used Work B eing Done P a rtic le s Per Cubic Foot 3" #G arnet Paper C utting Inside G ardner M achine Core Boxes Co, 2,322,240 C h a ra c te ris tic s o f Dust P a r tic le s (S iz e s and Percentage E stim ated) About 60$ q u a rtz -lik e in ap p earan ce, te n m i crons or over in sizej 40$ sem i-opaque fiv e m icrons or le ss in size. -70- DUST PRODUCED BY SAND SPINDLES OR CYLINDERS ( C o n c lu d e d ) S iz e (D ia. ) A brasive Used 3 -1 /2 " # l- l/2 G arnet P aper Minn, M ining Co. Work B eing Done P utting Taper on P attern. P a rtic le s Per Cubic Foot 877,920 C h a ra c te ris tic s of Dust P a r tio le s (S iz e s and P ercentage Estim ated) About 90% angular crys t a l l i n e two m icrons in s i z e j 10% o p a q u e 1f iv e m icrons or le s s in size. C. - MAKING WOODEN CRATES - Two t y p e s o f saw s a r e u s e d i n p r e p a r i n g lum ber f o r m aking c ra te s fo r g a s o lin e pumps and ta n k s j ( a ) Band Saws - S am p les t a k e n d u r in g t h e o p e r a t i o n o f Band Saw h ad a d u st c o n c e n tra tio n o f 453,120 p a r ti c le s te n m icrons o r le s s p er cubic fo o t o f a ir . A ll o f th e s e d u st p a r tic le s were round, opaque in ap p earan ce under th e Konim eter m icroscope and th re e m icrons or le s s in siz e . (b ) R a ilro a d Saws - Sam ples ta k e n d u rin g t h e o p e r a tio n o f an 18" R a ilro a d Saw had a d u s t c o n c e n tr a ti o n o f 3 ,9 6 4 ,8 0 0 p a r t i c l e s t e n m ic ro n s o r le ss, p e r cu b ic fo o t o f a ir. A ll of th e s e p a r tic le s were round, g ra y ish opaque in appearance under th e K onim eter m icroscope and ab o u t fiv e m icrons o r le s s in s iz e . There were a lso nu merous m inute gray specks to o sm all to count a c c u ra te ly . ' XII - ROCK EXCAVATION Rock ex cav atio n i s u s u a lly a d u st p ro d u cin g o p e ra tio n which is lim ite d to con s tr u c tio n a c t i v i t i e s in th e p etro leu m in d u s try . The h azard o u sn ess o f ro ck ex cav atio n depends e n tire ly upon th e n a tu re o f th e rock b eing excavated, th e le n g th o f exposure and th e methods being fo llo w ed . The p r in c ip a l so u rces o f d u st a re rook d r il li n g , b la s tin g , mucking and h a n d lin g o f th e rock. Of th e s e , d r i l l i n g p ro b ab ly produces th e g r e a te s t amount of d u st. A, - DRILLING - The p n e u m a tic ro c k d r i l l o p e r a t e s e s s e n t i a l l y a s a c r u s h in g d e v ic e which s h a tte r s th e ro ck to a powder a t th e p o in t o f im pact. A ccording to T h e o d o re H atch o f t h e H a rv a rd S c h o o l o f P u b lic H e a lth (N. Y. In d . B u l l , V o l. 1 5 , No, 9 - S ept, 1936) th e p a rtic le s o f d u st thus generated v ary in siz e from o n e-q u arter inch o r l a r g e r down t o s u b -m ic ro s c o p ic d ia m e te rs . The d u s t i s removed fro m t h e d r i l l h o le by a stream o f a i r or w ate r o r a co m b in atio n of th e two in tro d u c e d th ro u g h th e hollow d r i l l s te e l. In th e case o f jackham m er d r illin g a co n sid era b le amount of rock dust e je c te d from th e h o le f a l l s b ack to be cru sh ed f u r th e r b e fo re i t is removed ag ain , Q u o tin g Mr, H atch? "The am ount o f d u s t p rod u ced b y a r o c k d r i l l is s u r p r is in g ly la rg e - a jack-ham m er, o p eratin g a t th e o v e r-a ll r a te of 100 f e e t o f d r i l l i n g p e r day, a c tu a lly c ru sh es m ore th a n 200 pounds of rock in e ig h t hours. Cf th is , a t le a s t fiv e per cent, is in >- / th e form o f p a r t i c l e s sm a lle r th a n te n m icro n s| hence, more th a n f i f t y grams o f d u s t s m a ll enough to be a i r f l o a t e d i s g e n e ra te d p er fo o t d r i l l e d . In term s o f numbers o f p a r ti c le s th e f ig u r e s a re enormous - i t has been found t h a t a ja c k hammer p ro duces as o c n n ta V\ i T 1 n am rvn v-L? 1 q n P ^ i r w t a n i a i n4-Q voc4' rlur* i no* a h A -7 1 - B, - BLASTING - I t i s o f t e n s a id t h a t b l a s t i n g p ro d u c e s t h e g r e a t e s t am ount Hof d u s t in r o o k - e x c a v a tio n T h is s ta te m e n t i s c o n t r a d i c t e d b y some a u t h o r i t i e s who 're fe r to the f a c t th a t the b la s t dislodges a g re a t deal o f dust from the rock su r faces d ep o sited th e r e from e a r l i e r d r illin g o p e ra tio n in a d d itio n to th a t a c tu a lly generated by i t . Under th i s c o n d itio n b la s tin g is undoubtedly follow ed by a h ig h e r d u s t c o n c e n tr a tio n th a n i n th e c a s e when a l l th e d u s t p ro d u ced by d r i l l i n g i s ca p tu re d and conveyed to a rem ote c o lle c to r so th a t only th a t a c tu a lly generated by th e explosion escapes in to th e a ir. W hile i t i s u n d o ubtedly tr u e th a t i f d r i l l i n g is done d ry , th e re w ill be de p o s itio n of some o f th e d u st on th e su rfa c e s o f th e e x c a v a tio n and l a t e r be r a is e d by b la s tin g , how ever, d u st from th is source i s m inim ised i f d r i l lin g i s done w et, beoause th e slu sh ed o u t p a r t i c l e s ten d to form ag g lo m e ra te s, whioh a re n o t so r e a d i ly ra is e d by th e b la s tin g o p e ra tio n . A lso, when good p r a c tic e is follow ed, th e face and s id e s a r e w et down w ith w a te r b e fo re b l a s t i n g , and i n m in in g work, th e r e i s a continuous w ater sp ray th a t is s ta rte d onto th e heading b e fo re th e b la s t tak es p lace and c o n tin u e d f o r some tim e a f t e r t o h e lp a l l a y th e d u s t and t o w et down th e m a t e r i a l , so t h a t d u s t r a i s e d d u rin g m ucking w i l l be a t a minimum. C* - MUCKING - The am ount o f d u s t p ro d u c e d by m u ck in g and o th e r r o c k - h a n d lin g o p e r a tio n s v a r i e s g r e a t l y w ith th e n a tu r e o f t h e o p e r a t io n . On open e x c a v a tio n i t is probably o f li* ttle im portance, b u t in co n fin ed sources as in tu n n e ls and m ines t h e d u s t c o n c e n tr a tio n a s s o c ia t e d w ith ro c k h a n d lin g may r e a c h dangerous l e v e l s . D - DUST CONTROL - M ethods f o r t h e c o n t r o l o f d u s t i n ro c k e x c a v a tio n a s su g g e ste d by Mr. H atch in o lu d e t ( a ) - Wet D r i l l i n g an d W e ttin g Down Rook W alls an d Muck P i l e s - I n g e n e r a l i t may be s a id t h a t w a te r i s l e s s e f f e c t i v e a g a i n s t q u a r tz - b e a r in g ro c k th a n a g a i n s t s i l i o a - f r e e m a te r ia l such as lim e -sto n e . The u se fu ln e ss o f w ater i s lim ite d when fre e z in g te m p e ra tu re s a re en co u n tered and i t produces o b je c tio n a b le w orking c o n d itio n s e sp e c ia lly for overhead d r i l l operators and is c e rta in ly to be avoided i f a pneu monia hazard e x is ts , A fundam ental o b je c tio n to th e wet method i s th a t th e d u st i s n o t removed from th e scene o f o p e ra tio n b u t sim p ly su p p ressed n ear i t s so u rce w here i t rem ains to be throw n in to th e a i r by a subsequent d istu rb a n c e such as b la s tin g . (b) - G eneral V e n tila tio n - T h e purpose of g en eral v e n tila tio n is to d ilu te th e d u s ty a i r w ith s u f f i c i e n t c le a n a i r t o b r i n g th e c o n c e n tr a tio n down t o a s a t i s f a c t o r y l e v e l , Two p r e c a u t i o n s a r e re q u ire d * 1 s t. - th e fre s h a ir i t s e l f m ust be fre e from d u st and 2nd, - i t m ust be p ro p e rly d is tr ib u te d th ro u g h th e work in g s t o in s u r e maximum m ix in g w ith th e d u s t la d e n a ir. (c) - D ust E xhaust Hoods on D rills and O ther Muoking O p eratio n s and Sources of Dust - E ffe c tiv e d u s t c o n tro l can b e secu red by means of a d u st tr a p whioh surrounds th e d r i l l s te e l a t th e rock s u rfa c e . The d u s t-la d e n a i r is cap tu red as i t em erges from th e d r i l l - h o l e b y th e in flo w o f c l e a n a i r i n t o t h e t r a p . To b e e f f e c ti v e , th e i n l e t v e lo o itie s m ust be g re a t enough t o p re v e n t th e outward movement o f th e d u s t and s u f f i c i e n t v e l o c ity m ust be m a in ta in e d a t a l l p o in ts w ith in th e t r a p to p rev en t s e tt lin g and clo g g in g . The c o lle c te d d u s t is conveyed by th e a ir-s tre a m jh ro u g h hose and p ip in g t o a s u ita b le d u st s e p a r a to r in w hich th e a i r is fre e d from -^Lts d u s t lo a d and th u s i s d is c h a rg e d from t h e a p p a r a tu s a s c le a n a i r . T raps o f d i f - fe re n t designs a re req u ired w ith various d r il lin g o p eratio n s and sp e c ia l su p p o rtin g devices are n ecessary to hold th e tra p in proper alignm ent w ith th e sev eral o p erat in g p o sitio n s (NOTE* The d u s t t r a p i s s a t i s f a c t o r y u n d e r many c o n d i t i o n s , b u t a g a i n u n d e r many o th e r c o n d i t i o n s h a s n o t p roved s a t i s f a c t o r y RSB) Looal -7 2 - The d u s t d is p e rs e d during m ucking, as w e ll as th a t a r is i n g from ro ck d r i l l in g , can be c o n tro lle d by lo c a l exhavist v e n t i l a t i o n and re q u ire s no e la b o ra te ap p a ra tu s. (d) - P e r s o n a l P r o t e c t i o n By Means o f R e s p i r a t o r s and P o s i t i v e - P r e s s u r e M asks - An e f f e c t i v e r e s p i r a t o r o r a p o s i t i v e - p r e s s u r e m ask s u p p lie d w ith a n a d e q u a te q u a n tity of d u s t- f r e e a i r provides th e w earer w ith p ro te c tio n when i t f i t s th e face p ro p e rly and i s worn c o n tin u o u sly in d u sty atm ospheres. R e s p ira to rs and masks have a le g itim a te p lace in th e field of s ilic o s is c o n tro l, e sp e c ia lly to provide pro te c tio n a g a in s t in fre q u e n t unexpected d u s t c o n c e n tra tio n s b u t can n o t be recommended as a s u b s titu te fo r d u st co n tro l in continuous o p eratio n s. -7 3 - PART III - MEASURES FOR REDUCTION OF THE DUST HAZARD HOW CAN THE DUST HAZARD BE REDUCED? - The q u a n t i t y o f d u s t in h a le d may be m in im iz e d b y t h e employment o f t h e s e f o u r m ethods o u t l i n e d b y Dr. It, Kummel i n "M edioal Record"?- Ml . S uppr e s s i o n o f D u st N ear I t 1 s O r i g i n , b y t h e u s e o f e x h a u s t d r a u g h t, d u st tr a p s o r w ater. The w a te r has th e ad v an tag e o f a fly -p a p e r e f f e c t on th e s i l i c a p a r tic le s , but th e hum idity c re a te d te n d s to favor in fe c tio n by prolonging th e l i f e of pathogenic organism s o u tsid e th e body and f a c i l i t a t in g th e ir entrance in to th e body, 112. A dm ixture o f A d u lte r a n t D ust w i t h th e s i l i c a w h ich may a s s i s t i n th e ex p ulsion o f s i l i c a from the lungs, re ta rd th e pro cess o f th e d ise a se or p rev en t th e developm ent o f tu b e rc u lo s is . However, th e in tr o d u c tio n o f an a d d itio n a l fo re ig n body in to the lungs i s of d o u b tfu l v alu e fra u g h t w ith p o te n tia l danger and should be re g a rd e d very c a u tio u s ly and con serv ativ ely , " 3, P ro p e r V e n ti la ti o n , i n c o n n e c tio n w ith o th e r methods "4, Masks should be an id e a l p re v e n tiv e m easure b u t, u n fo rtu n a te ly , m ost o f th e masks sto p p in g th e d u st a ls o s to p th e r e s p ir a tio n , th u s ne c e s s ita tin g th e ir freq u en t rem oval. They should be of an approved ty p e, properly m aintained, s t r i c t l y supervised and th e ir use rig id ly en fo rced ," We do n o t b e l i e v e t h a t t h e u s e o f w a te r w ould h a v e an y o u t s t a n d i n g e f f e c t s on r a is in g th e hum idity in most o f the d u st producing o p eratio n s in th e Petroleum In d u s t r y , a n y m o re th a n , f o r e x a m p le , s p r i n k l i n g one' s aw n would h a v e . We b e l i e v e i t rem ains to be proved beyond doubt th a t th e h u m id ifio a tio n of a i r a c tu a lly favors b a c te r io lo g ic a l growth to th e e x te n t th a t th e in o id e n c e o f d is e a s e from p ath o g en ic organism s is r a is e d s ig n if i c a n tl y . T here has been much d is c u s s io n on t h i s s u b je c t, b u t l i t t l e h as been proven. T h e o r e tic a lly , i t may be a d m itte d t h a t th e s e organism s liv e longer in a m oist atm osphere th a n in a d ry atm osphere, but i t is ra th e r hazard ous reasoning to conclude th a t fo r th e reaso n s s ta te d , th e use o f wet m ethods in d u st co n tro l causes an increase in d isease. Dr, Kummel' s s ta t e m e n t t h a t m ost m asks (we presum e h e means r e s p i r a t o r s ) t h a t sto p du st also stop re s p ira tio n s , is a l i t t l e stro n g . There a re a v a ila b le today r e s p ira to rs th a t ad eq u ately remove d u st w ith o u t c re a tin g a re s is ta n c e to b re a th in g in excess o f 15 to 30 m illim e te r s of w ater colum n, and th e tendency o f p ro g re ssiv e m a n u fa c tu re rs o f suoh d e v ic e s i s t o f u r t h e r lo w e r th e r e s i s t a n c e . Men d u r in g th e war a c tu a lly d id fig h tin g w hile w earing re s p ira to iy p ro te c tiv e devices th a t had as much a s 50 t o 75 m illim e te r s r e s i s t a n c e . The r e s i s t a n c e f ig u r e s g iv e n f o r r e s p i r a to r s a re m easured a t a r a te o f a i r flow of ab o u t th re e cu b ic f e e t a m inute which i s e q u iv a le n t t o t h e amount o f a i r b re a th e d by a p e rs o n d o in g h a rd p h y s ic a l work Dust R e s p ira to rs and A ir Masks - R e s p ira to rs and m asks o f v a rio u s ty p e s have been used sin o e th e days o f th e a lch em ists and a re m entioned by A g rico la, Ram azzini and o th ers. C ontrol of th e d u st hazard by means o f re s p ira to ry p ro te c tiv e equip ment is e ff e c tiv e , provided? (1 ) th e p ro te c tiv e equipm ent is e f f ic ie n t, and (2 ) i t is worn c o n tin u o u sly . E f f ic ie n t equipm ent is a v a ila b le , b u t for c o n tin u o u s use, day a f t e r day, t h i s method o f c o n tro l cannot be depended upon to provide the f i r s t lin e of defensej in th is re s p e c t i t may be lik en ed to th e use o f p e rso n a l im m unization as a p rim ary safeg u ard a g a in s t th e sp read of ty p h o id fever Dust r e s p ira to rs and a i r masks do, however, have a d e f in ite place in th e f ie ld o f d u st c o n tro l, e s p e c ia lly as an emergency m easure, as a means o f p r o te c tio n on in fre q u e n t d u sty o ccu p atio n s and as an ad ju n ct to o th e r m ore fundam ental m ethods o f p rev en tio n . i R ep o rts made to th e N a tio n a l S i l i c o s i s C onference, c a lle d by th e S e c re ta ry o f Labor in February (1937) to -study s p e c ific phases o f th e s ili c o s is problem and p re s e n t s u g g e s tio n s f o r i t s s o lu ti o n , c o n ta in e d many recom m endations b y q u a l i f i e d au t h o r i t i e s on th e s u b je c t w hich have been s u c c e s s fu lly employed u n d er a c tu a l o p e ra tin g - c o n d itio n s . B r ie fly summarized m easures f o r th e c o n tro l of d u st and th e p re v e n tio n o f pneum oconiosis inolude* A. - DESIGN PLANT FOR DUST CONTROL - Much c a n be a c c o m p lis h e d th r o u g h d e s ig n when new b u ild in g s a re c o n te m p la te d o r when old " b u ild in g s a r e to be rem o d eled . For in s ta n c e , s t r u c t u r a l p r o je c tio n s and le d g e s may be m inim ized to p re v e n t t h e accumu la tio n o f d u st th a t m ight l a t e r be re le a s e d in to th e atm osphere by a ir c u rre n ts or by b u ild in g v ib ra tio n caused by tr a v e llin g cran e s, v ib ra tin g m achinery, and equipment t h a t have la r g e r e o ip r o c a tin g p a r ts . The E n g in e e rin g Com m ittee re c o g n iz e d th e f a c t th a t our p re s e n t day e n g in e e rin g and s tr u c tu r a l m a te ria ls fo r f a c to r ie s do n o t per m it e lim in a tio n o f innum erable led g es and p ro je c tio n s w ith o u t p ro h ib itiv e b u ild in g and ro o fin g c o s ts . However, b u ild in g i n t e r i o r s sh o u ld be so c o n tru c te d t h a t th e y may be e a s ily c lean ed by w ashing, h osing, vacuum c le a n in g o r b ru sh in g . In some cases o p e ra tio n s may be lo o a te d o v er g r a tin g s , b e n e a th w hich equipm ent i s p ro v id e d fo r r e m oving th e m a te r ia ls and d u s t th a t f a l l th ro u g h . B. - PROVIDE BUILDING VENTILATION - N a tu r a l v e n t i l a t i o n s h o u ld u s u a l l y be c o n sid ere d only an ad ju n c t in rem oving or red u cin g d ust in th e a i r . Even though i t is p o s sib le to have higji ro o fs in o n e -sto ry s tru c tu re s w hich w ill g iv e th e g re a te s t b e n e f i t fro m n a t u r a l v e n t i l a t i o n , su c h m e th o d s c a n n o t b e r e l i e d upon t o p r o v id e com p le te p r o te c tio n in d u sty o p e ra tio n s . Where m ech an ical v e n t ila t in g system s a re pro v id e d , c a r e sh o u ld be ta k e n to p re v e n t s tr o n g d r a f ts from open windows and doors de s tro y in g th e e ffe c tiv e n e s s of th e system . Guards and s h ie ld s should be p laced in th e v ic in it y o f hooded and p a r t i a l l y en clo sed p ro c e sse s to p re v e n t such a c o n d itio n , C. - STORE DUSTY MATERIALS IN DUST-TIGHT BINS - D u sty m a t e r i a l s s h o u ld be s to re d in d u s t-tig h t b in s, ta n k s, or en clo su res, but each s tru c tu re of th is type should be provided w ith a b re a th e r or v e n t sta c k perhaps w ith an exhaust fan in th e sta c k -- to perm it th e a ir d isp laced during lo ad in g to be c a rrie d o u tsid e the b u ild in g . B asem ents may be u se d f o r s to r a g e p u rp o ses b u t sh o u ld n o t be u se d f o r d u sty m anufacturing o p eratio n s. D - ENCLOSE MATERIAL HANDLING EQUIPMENT - E x c e s s iv e d u s t c r e a t e d b y m echan ized m a te ria l - handling equipm ent can u s u a lly be c o n tro lle d by p ro v isio n o f adequate h o u s in g and a p p l i c a t i o n o f e x h a u s t system s Some m a t e r i a l s c a n b e k e p t i n a m o is t c o n d itio n w h ile b e in g h a n d le d , b u t when t h i s is done, th e m a te r ia l may d ry o u t and b e d isp e rse d in to th e atm osphere as du st. E - ISOLATE DUSTY PROCESSES - W here p o s s i b l e , s e v e r a l o r a l l d u s t y p r o c e s s e s may be is o la te d from th e r e s t o f th e p la n t. This som etim es p e rm its th e i n s t a l l a t i o n o f a more com pact exhaust sy stem r e s u lt in g in more e f f i c i e n t o p e ra tio n and low er m ain- enance co st. F. -- PROVIDE WET METHODS OF OPERATION - W a te r, o i l , and o t h e r l i q u i d s may b e used effectiv ely -75 1, To S u p p re s s d u s t a t t h e p o in t o f o r i g i n i n su o h o p e r a t io n s a s ro c k -d rillin g j` han d lin g , p u lv erizin g , and m illin g rock and o rej g rin d in g m etal on g rin d sto n e s; ab rasiv e -w h ee l o u ttin g of g r a n ite and san d sto n e . 2. To p r e v e n t t h e r e - d i s p e r s i o n o f d u s t t h a t h a s s e t t l e d on th e f lo o r s , w a lls, and o th e r su rfao es such as in th e g ra n ite in dus t r y and in fo u n d rie s, G, - DESIGN1EQUIPMENT TO CONTROL DUST - When new m a o h in e ry o r o th e r eq u ip m en t is contem plated, th e m anufacturer can freq u en tly be encouraged to inolude dust con t r o l fe a tu re s such as exhaust hoods as an in te g r a l p a r t o f th e d esig n and construo-_., tio n , H. - PROVIDE EXHAUST SYSTEMS - In some o p e r a t i o n s , e x h a u s t s y ste m s may be in s ta lle d to remove d u st a t i t s p o in t o f o rig in * In many, cases s e v e ra l sm all system s a r e p r e f e r a b l e t o a l a r g e r s y s te m . Any m e c h a n ic a l v e n t i l a t i o n s y s te m s h o u ld b e d e sig n e d to m eet a t l e a s t th e minimum re q u ire m e n ts o f l o c a l S ta t e law s o r i n d u s t r i a l codes, or lack in g such req u irem en ts, should be in s ta lle d according to th e b e st ac cepted p ractice. Dust A rre ste rs - P rovision of d u st a rre s te rs w ill prevent hazardous d u sts from b eing c irc u la te d in to o th er p a rts o f th e p la n t or in to th e neighborhood. The lo c a tio n o f d u s t a rre s te rs is v ery im portant, p a rtic u la rly i f dry types of a rre s te rs are u sed . P r o v is io n sh o u ld be made f o r rem oval o f th e c o lle c te d d u st w ith o u t i t s escape in to th e a re a where th e a r r e s te r is lo c a te d , I. - ESTABLISH MAINTENANCE AND GOOD HOUSEKEEPING PROCEDURE - Good h o u s e k e e p in g i s u n q u e s tio n a b ly th e c h e a p e s t s in g le method o f c o n t r o l l i n g d u st. M aintenance goes w ith i t hand in hand. The b e s t equipm ent in th e w orld w ill n o t c o n tro l d u st i f su p e rin te n d e n ts , forem en, and w orkers a re c a r e le s s and d is o r d e r ly in t h e i r work. E ig h t su g g e stio n s a r e advanced by th e C onference Committees 1, I f d u s t- tig h t equipm ent is in s ta lle d i t should be in sp e c te d a t re g u la r and freq u en t in te rv a ls and a l l d e fe c ts should be co r rected as soon as they are detected. 2, O p eratio n s sh o u ld be perform ed in a manner th a t w ill o re a te th e minimum am ount o f d u st. 3, Use w a te r u n d er p re s s u re where p o s s ib le to c le a n b u ild in g i n terio rs. 4, I f p r a c tic a b le , oombine w ater w ith a i r fo r c le a n in g p u rp o ses, A ll c le a n in g should be done, i f p o s s ib le o u tsid e o f working h o u rs and men engaged in th is o p e ra tio n should be pro v id ed w ith du st re s p ira to rs , 5, Vacuum c le a n in g removes d u s t w ith o u t d is p e r s in g i t elsew h ere, 6, B rushing is p a rtic u la rly adaptable fo r clean in g b u ild in g s o f the older type of co nstruction. 7, L o w -p ressu re steam can som etim es be used to ad v an tag e. 8. A re s p o n s ib le p e rs o n should be a ssig n e d th e ta s k o f s u p e rv is in g m a in te n a n c e and h o u se k e e p in g a c t i v i t i e s . Among o th e r th in g s he sh o u ld make t e s t s from tim e to tim e to make su re th a t th e d u st c o n tro l program is ach iev in g th e d e s ire d re s u lts J,, - PROVIDE RESPIRATORS - The C o n fe re n c e C om m ittee was o f th e unam inous o p in ion th a t "d u st e lim in a tio n m ust be given prim ary c o n sid e ra tio n in so lv in g th e s i l i c o s is problem ". N e v e rth e le s s , when known m ethods o f e lim in a tio n a re n o t a p p lic a b le o r a re in e ff e c tiv e , r e s p ir a to r s should be provided as "a l a s t re s o rt and fo r oc casio n a l exposure only. R o ta tio n o f p erso n n el under th e se conditions is ad v isab le. " The r e p o r t d e f i n i t e l y s ta t e s , t h a t . th e r e , w i l l .a lw a y s;be._places. where o th e r m ethods w ill be in a p p lic a b le and in e f f e c tiv e , and r e s p ir a t o r s `w ill be re q u ire d f o r doing th e work, a ls o th a t th e re w ill be s itu a tio n s w here r e s p ir a to r s w ill be th e prim ary means o f p r o te c tin g th e workmen. The scope o f good u se o f r e s p ir a to r s i s c o n s id e r ably beyond th a t o f o cca sio n al exposw e. The need o f r o ta tin g p erso n n el depends on th e ty p e o f work done and th e s u p e r v is io n g iv e n th e workmen. In some o p e r a t i n s , r e s p i r a t o r s a r e as much a p a r t o f th e workman' s equipm ent a s h is to o ls . C e r ta in ly , i t cannot be expected th a t a person can wear a r e s p ira to r fo r sev eral hours con t i n u o u s l y - b u t how many jo b s a r e t h e r e t h a t w ould r e q u i r e a p e r s o n t o k e e p t h e r e s p i r a t o r on c o n t in u o u s ly f o r a n e x te n d e d p e r io d o f tim e . T he common p r a c t i c e i n t h e m ajo rity o f in d u s tria l occupations is th a t th e person is in te rm itte n tly exposed and is a ffo rd e d many o p p o r tu n itie s fo r th e p e rio d ic rem oval o f th e r e s p ir a to r y p ro te c t i v e d evice. The two g e n e ra l ty p e s o f r e s p i r a t o r s which th e Committee c o n s id e re d s u ita b le for p ro te c tio n a g a in st s ilic a dust are? (a) A ir-p u rify in g re s p ira to rs th a t f il te r out the dust p a rtic le s. (b ) S u p p lie d -a ir r e s p ir a to r s in w hich d u s t- f r e e a i r b reath ed by th e w orker comes t o him from an u n c o n ta m in a te d o u ts id e s o u rc e . Most r e s p ir a to r m a n u fa ctu rers have subm itted th e ir d e v ic e s fo r te s tin g and approval b y t h e U. S. B u re a u o f M in e s, an d o n ly th o s e w h ich h a v e b e e n a p p ro v e d s h o u ld b e u s e d . (a) A ir-P u rify in g Types o f R esp irato rs - Of the a ir-p u rify in g c la s s , th e type m ost commonly u se d i s t h e m e c h a n ic a l f i l t e r r e s p i r a t o r f o r m e c h a n ic a lly -g e n e ra te d d u st. These r e s p ir a to r s g iv e no p ro te c tio n from gases and vapors. They g e n e ra lly c o n s is t o f h a l f fa o e p ie c e s to which a re a tta c h e d an ex h au st v alv e and a f i l t e r i n g medium t h a t rem oves th e d u s t from th e in h a le d a i r j some a r e equipped w ith a f i l t e r medium t h a t rem oves p a i n t m is ts and some fum es. They a r e l i g h t i n w e ig h t and in e x pensive. F ilt e r pads m ust be changed a t c e r ta in in te r v a ls , depending on th e concen t r a t i o n o f d u s t. Some ty p e s r e s t r i c t th e f i e l d o f v i s i o n . The g e n e r a l r e q u ire m e n ts o f a sa fe and s u ita b le M echanical f i l t e r r e s p ir a to r a r e ( l ) adequate p r o te c tio n , (2) re a so n a b le co m fo rt and co n v en ien ce, (3) an a c c e p ta b le s e rv ic e l i f e p erio d o f p ro te c tio n , (4) easy c le a n in g and s t e r i l i z a t i o n , and (5 ) low c o s t o f m aintenance in good serv iceab le condition. S tu d ie s o f m e c h a n ic a l f i l t r a t i o n by fib r o u s m a te r ia ls made by s u c h a g e n c ie s as t h e U n ite d S t a t e s B u reau o f M ines (U .S , B ur, o f M in es, T ech. P a p e r No. 394 (1 9 2 6 ) and U.S. P u b .H e a lth B u ll.N o . 177 (1 9 2 8 )) and th e H arvard School o f P u b lic H e a lth (Jo u rn . In d u s t. Hyg. 9 ,2 6 (1 9 2 7 )) re v e a le d t h a t f i l t e r i n g e f f ic ie n c y v a r ie s w ith th e p a r t i c l e ^ize and th e amount of s o lid p a r tic u la te m a tte r r e ta in e d j a ls o th a t th e r e s is ta n c e to tjkir flow v a r ie s w ith th e amount of s o lid p a r tic u la te m a tte r re ta in e d and th e r a te o f a i r flow. A fte r a l l , th e fundam ental b a s is f o r ju d g in g th e s u i t a b i l i t y o f a r e s p i r a to r is w hether o r n o t th e amount o f d u st th a t is u n re ta in e d or escapes th ro u g h th e f i l t e r under c o n d itio n s o f p r a c tic a l use i s below th e amount th a t would be harm ful to b reath e. This is n o t r e la te d to any percen tag e e ffic ie n c y . In order to meet th e -77- dusts of th e follow ing size c h a ra c te ristic s? 99 per c e n t sm a lle r th a n 2 ,8 0 m icrons 95 II ii ti tt .1 , 80 rt 90 tr it it It 1 40 ti 80 1! ii tt 11 1 .0 0 n 70 ii it it It 0 , 85 u 60 it tr n tt 0 .7 2 tt 50 it it f! tt 0 .6 0 ti I t w ill be n o te d th a t 80 per c e n t o f th e d u s t used one m icron (l/2 5 ,0 0 0 th of an inch) and 50 p er c e n t w illr|n o ^ ,'^ ^ < ^ e itd u sta -o f th e se c h a r a c te r is tic s and rato rs; ' in th e se approval t e s t s is below is below 0,6 m icrons. C an isters should n o t be used as dust re s p i In order to obtain th e desired p ro te c tio n , i t is e sse n tia l th a t th e faoep ie c e s o f th e m e c h a n ic a l- f il te r r e s p i r a t o r s f i t th e fa c e o f th e workman sn u g ly b u t w ith a minimum o f h ead -b an d te n s io n . A s im p le p r a c t i c a l t e s t , s u g g e s te d by C a r lto n E. Brown o f t h e U, S, B ureau o f M ines E x p e rim e n t S t a t i o n in P i t t s b u r g h , P e n n s y lv a n ia ( J o u r , In d u s t, Hyg, Feb, 1937 V ol. 19 , No, 2 , p, 9 8 ) , t h a t anyone c a n r u n t o d e te rm in e w h eth er a r e s p ir a to r face p iece i s m aking a tig ih t s e a l, is to wear i t in a h ig h con c e n tr a tio n o f c o a l d u st. The tim e o f th e t e s t can be sh o rte n e d by blow ing a stream of a ir co n tain in g a high co n ce n tratio n of coal dust around th e edges of th e facep ie c e , The lo c a tio n and ap p ro x im ate m ag n itu d e o f th e le a k s a re shown by s tr e a k s of c o a l d u s t on th e p a r t o f th e fa c e c o v ere d b y th e fa c e p ie c e . A nother t e s t , a c c o rd in g t o Mr, Brown, c o n s i s t s o f p lu g g in g t h e in ta k e s o f th e r e s p i r a t o r and th e n a tte m p tin g to in h a le. This type o f t e s t could w e ll be supplem ented by th e Coal d u st te s t. (b ) Supp lie d A ir R e sp ira to rs - I n d u s tr ia l p ro cesses such as pneum atic d r illin g ,a b ra s iv e b la s tin g and spray c o a tin g have in tro d u c e d atm ospheric c o n d itio n s fo r w hich th e a ir-p u rify in g type of re s p ira to rs a re n o t p a rtic u la rly s u ita b le . C ertain kinds o f pneum atic d r i l l i n g a re re s p o n s ib le f o r d u s t c o n c e n tra tio n s so h ig h th a t th e y would ra p id ly overload a d u s t r e s p ir a to r . The o p e ra to r of an a b ra s iv e b la s tin g o u t f i t m ust be p ro te c te d n o t only a g a in st th e in h a la tio n of a i r c o n ta in in g h ig h co n cen tra tio n s o f d u st, b u t a ls o a g a in st im pact and a b ra s io n o f th e head and sh o u ld er by th e rebounding a b ra siv e and loosened abraded m a te ria l. Spray co atin g is re sp o n sib le fre q u en tly for p o llu tio n of the surrounding atm osphere by a com bination of p a rtic u la te m a tte r (m ists th a t a re liq u id p a r tic le s or a com bination o f s o lid and liq u id p a r t i c l e s ) and h arm fu l vapors r e s u ltin g from th e e v a p o ra tio n o f th e liq u id v e h ic le o f th e c o atin g used in th e spray gun. S ince th e s e o p e ra tio n s a re c a r r ie d o u t fre q u e n tly in is o la te d p la c e s and a t d if f e r e n t lo c a tio n s a t v ario u s times, they do n o t lend them selves always to g en era l c o n tro l m easures. T herefore, sup p lied a i r r e s p ira to rs perform a d e f in ite service The ty p e s in g e n e ra l u s e a re th o s e commonly known as h o se m asks, a i r - l i n e r e s p i r a t o r s , and ab rasiv e b la s tin g re s p ira to rs such ps sand b la s t masks, helm ets, and hoods. S u p p lie d -a ir re s p ira to rs have th e fo llo w in g advantages fo r ro u tin e non-em er gency use over th o se o f the a ir-p u riiy in g re s p ira to rs such as gas masks, m echanicalf i l t e r r e s p ir a to r s and th e com bination o f gas mask w ith a m echanical f i l t e r ? 1 NO r e s i s t a n c e t o i n h a l a t i o n . 2, Freedom from inward le ak ag e o f co n tam in ated air 3. P ro te c tio n a g a in s t a l l k in d s o f co n tam in an ts and even a g a in st a t m ospheres d e fic ie n t in oxygen which w ill n o t poison or i r r i t a t e the skin. 4 The I n f lo w in g a i r re d u c e s e x c e s s iv e p e r s p i r a t i o n and te n d s ^ to cool the face, 5. When a h a n d - o p e r a te d b lo w er i s u s e d a se c o n d p e r s o n i s a lw a y s p re s e n t, (W ith an approved mask, p rovided th fa c e p ie o e is tig h t, th e w earer can in h ale enough a ir through th e hose to es cape i f th e blow er should sto p ). The A ir- Line R e sp ira to r c o n s is ts of a t i g h t - f i t t i n g facep iece, a lo o sely f i t t i n g fa c e p ie c e o r even a h elm et o r hood c o v e rin g th e head and e x te n d in g down over th e neck or s h o u ld e rs . The a i r s u p p lie d to th e s e r e s p ir a t o r s h as been l a r g e l y th a t ob ta in e d from th e com pressed a i r so u rce used in th e perform ance o f th e work, as in sand b la s tin g , pneum atic d r i l l i n g and sp ray p a in tin g . T his a i r is f r e q u e n tly con- -- ta m in a te d w ith o b je o tio n a b l e a n d , i n some i n s t a n c e s , h a rm fu l s u b s ta n c e s w h ich , t o some e x te n t, can b e removed by means o f a i r - p u r i f y in g ap p u rte n an o es. In d is c u s s in g "Res p ira to ry P ro te c tiv e D evices" in th e F ebruary (1937) issu e o f the Jo u rn al o f Indus t r i a l H y g ie n e an d T o x ic o lo g y , Mr, C, E, Brown o f t h e U n ite d S ta t e s B u re a u o f M ines w rotei "U sing a i r from th e o rd in a ry com pressed a i r system found in in d u stry t o su p p ly r e s p ir a to r s is n o t to be in d is c r im in a te ly recommended. These com pressed a ir system s a re u su a lly o f the high p re ssu re , in te rn a lly lu b r ic a te d , re c ip ro c a tin g -c o m p re s s o r ty p e . The a i r s u p p lie d b y th e s e system s is contam inated fre q u e n tly w ith m alodorous c o n s titu e n ts such as v ap o rs, m ists and p ro d u cts of decom position of th e com pressor lu b r ic a n t, slu g s of w ater, and ru s t from th e pipe lin e . A ll or most of th e s e co n tam in an ts can be removed p ro b a b ly by some o f th e com m ercial a i r p u r if i e r s so ld f o r th is purpose. A p re ssu re -re d u c in g meohanism should be used also in th e lin e to prevent any p o s s ib ility o f sudden a c c id e n ta l b la s ts o f h ig h -p re s s u re a i r from in ju r in g th e lu n g s o f th e w e a re r o f th e r e s p i r a t o r . W ith a co m p resso r o f t h i s ty p e t h e r e i s alw ays t h e p o s s i b i l i t y , how ever r a r e i t may b e in w e ll- k e p t sy ste m s, o f th e g e n e ra tio n of carbon monoxide due to o v e rh e a tin g of th e com pressor lu b r ic a n t ( Jo u r. In d u st. Hyg, 18,461 (1 9 3 6 )). This danger can be m inim ized or e lim in a te d by th e u se o f te m p eratu re c o n tro ls o r carbon monoxide alarm s on th e com pressor w hich, of co u rse, should be so m aintained as to p re v e n t th e g e n e ra tio n o f carbon monoxide, "The tre n d in s u p p lie d -a ir r e s p ira to rs is to use sp e c ia l lo w -p ressu re, e x te r n a lly lu b ric a te d , p o s itiv e -p re s s u re a ir-s u p p ly devices. Most of th e o b je c tio n s to th e h ig h -p re s s u re re c ip ro c a tin g -ty p e com pressor do n o t apply to an a ir-s u p p ly of th is kind. Since th e se d ev ices are n o t common i n i n d u s t r y , h o w e v e r, i t i s u s u a l l y n e c e s s a r y t o p u r c h a s e a s p e c ia l one fo r use w ith th e re s p ira to r. Since a i r p u r if ie r s , p res s u r e - r e d u c i n g m e c h a n ism s, and s p e c i a l c o m p r e s s o r - c o n t r o l o r a la r m me chanism s a re not n e c e ssa ry , th e p ric e of th is re s p ira to r com plete w ith a ir-su p p ly device should not exceed th a t of th e o th e r type of re s p ira to r w ith o u t th e a i r sup o ly system . "The use of a s p e c ia l a ir-c o n d itio n in g u n it to re g u la te th e tem pera t u r e and h u m id ity o f th e a i r s u p p lie d to th e r e s p i r a t o r w earer is de~ J 1 sira b le ." The minimum a i r s u p p ly fo r a r e s p i r a t o r d e sig n e d to use a l l th e a i r f o r r e s p ir a to r y needs a t a h ig h d e g re e of e f f ic ie n c y is g e n e ra lly ag reed among I n d u s tr ia l H y g i e n i s t s t o b e a t l e a s t f o u r to six tim e s t h e air breathed p e r m in u te . As a g en era l c la s s , re s p ira to rs w ith lo o s e - f ittin g face p iece s, hoods, or helm ets req u ire -79- more a i r than th o se w ith tig h t f i t t i n g facep ieces. J' T here i s some d if f e r e n c e o f o p in io n among u s e rs o f r e s p i r a t o r s as to w hether or n o t adjustm ents should be p rovided whereby th e w earer can v a ry th e flow o f a i r to m e et v a r i a t i o n s i n h i s r e q u ir e m e n ts . I t was t h e o p in io n o f t h e N a ti o n a l S i l i c o s i s C onference Committee t h a t d e f i n i t e recom m endations f o r a l l s itu a tio n s can n o t be made, b u t f o r many s i t u a t i o n s , and p a r ti c u la r ly w here t i g h t - f i t t i n g fa o e p ie o e s a re u se d , an a d ju s ta b le flo w i s d e s i r a b l e and may even be n e o e s s a r y j a l s o , m ost workmen c a n l e a r n t o a d j u s t t h e a i r p r o p e r l y . On th e o t h e r hand f i x e d - f l o w p r o c e d u r e s r e q u ir e a minimum amount o f i n s t r u c t i o n and s u p e r v is io n and a r e t h e m o st co n d u civ e t o safety under a ll cond itio n s. W hile Hose Masks and A ir-L in e R e sp ira to rs have m a n y 'd e fIn i^ 'a d v a n ta g e s th e a re a o f tr a v e l o f th e w earer is lim ite d to th e le n g th o f th e h o s e , and movements a re h an d icap p ed t o some e x te n t by th e hose. M a n ife s tly , t h e a i r f o r th e h o se and th e mask should be f r e s h and p u re, b u t u n fo rtu n a te ly t h i s i s n o t alw ays so. A brasive B la stin g Respir a to r - A brasive b la s tin g r e s p ir a to r s c o n s is t essen t i a l l y o f a hood, w ith windows, th a t f i t s lo o s e ly over th e head and sh o u ld ers and designed to w ith stan d and p ro te c t th e w earer' s head, neck and sh o u ld ers from ab ra sio n by the rebounding o f p a rtic le s o f sand or g r itj and a su p p ly of fre sh a ir , a t l e a s t s ix cubic f e e t p e r m in u te , blow n in to th e hood. Only equipm ent which has met th e U nited S ta te s B ureau o f M ines t e s t req u irem en ts and w hich is approved by th e M edical and S afety D epartm ents should be used. (c) A cceptance and Use o f P e r s o n a l R espi r a t o r y P r o te c t io n by Workman - As s t a t e d i n a p a p e r by G, M. K in tz and H. C, Fow ler o f t h e U n ite d S t a t e s B u re a u o f M ines ( I .C ,6915 N o.vl936) p re se n te d a t th e I n te r n a tio n a l P etro leu m E x p o s itio n and C ongress, T u ls a , Oklahoma, May 21 1936, s e l e c t i n g r e s p i r a t o r y p r o t e c t i v e eq u ip m en t i s s im p le com pared w ith g e t tin g men to w ear i t a f t e r i t i s s u p p lie d . G e n e ra lly workmen w ill w ear masks r e a d ily in p la c e s w here th ey have seen o th e rs a s p h y x ia te d , or in some s im ila r tro u b le , b u t th e y a re l i k e l y to r e s i s t w earing p ro te c tiv e equipment w here th e d u s t cannot b e seen o r w h ere th e fumes and m is t have no o b je c tio n a b le odor. There a re th re e m ain reasons fo r such re sista n c e s F i r s t , in b re d o b je c tio n to any new id e a j Second, th e fe e lin g th a t th e in d iv id u a l is a superman and can. "ta k e i t " w ith o u t p r o te c tio n ! an d , T h ird , th e inconvenience o f w earing th e equipm ent. I n a s u rv e y c o n d u c te d among t h e em ployees o f t h e Col g a t e - P a lm o li v e - P e e t Com p an y b y Mr, F, H, W a lln e r o f t h a t Company' s I n s u r a n c e D e p a rtm e n t, i t was fo u n d t h a t th e men d id n 't l i k e th e d is f ig u r in g appearance o f a "m uzzle" over t h e i r fa c e s. This su rv e y a ls o d is c lo s e d t h a t some w orkers o b je c te d to th e r e s p i r a t o r because th e y th o u g h t i t made b r e a th in g d i f f i c u l t when th e r e a l tr o u b le was t h a t th e y w ere n o t b re a th in g c o rre c tly . B re a th in g through a r e s p ir a to r should be done deeply and slow ly and a f te r th e p ro p er h a b it h as been a c q u ire d much d lso a m fo rt may be e lim in a te d . Q u o tin g Mr. W a lln e rt "Foremen should a p p re c ia te th a t th e p o s itio n o f th e s tra p s th a t h o ld th e r e s p i r a t o r in p la c e has much to do w ith co m fo rt. They should le a rn w hether th e s tra p s should be worn over th e head or around th e n eck . Some ty p e s h a v e tw o s t r a p s , one t o be w o rn aro u n d t h e n e c k , th e other around the head. " P ro b a b lv t h e m o st e f f e c t i v e n la n in v o -th in c ressnirntnrK wnm is first, to " s e l l " the s u p e r v is in g p e r s o n n e l who i n t u r n s h o u ld " s e l l " t h e w o rk e r b y e d u c a tio n , p o s s i b l y t ^/ocom panied by s t r i o t and f a i r su p e rv is io n and d is c ip lin e . Employees exposed t o d u s t hazards re q u irin g th e w earing o f re s p ira to rs should be convinced th a t i t is e s s e n tia l t o s a c r if i c e some com fort and d ig n ity to a v o id s e rio u s c a s e s o f d i s a b i l i t y and s u f f e r in g . E very w o rk e r s h o u ld h a v e h i s own r e s p i r a t o r . I t r e q u i r e s tim e and e f f o r t t o a d j u s t t h i s p r o t e c t i v e d e v ic e so i t c o n ta o ts th e f a c e s n u g ly w ith a minimum o f h e a d band te n sio n . I t cannot be expected th a t th e average workman w ill r e a d ju s t a d i f fe re n t r e s p ira to r each day. A lso, the psyohologioal e ffe o t o f u sin g a r e s p ira to r w orn p re v io u s ly b y a n o th e r workman i s n o t u n im p o rta n t. A lth o u g h h e may n o t say any th in g about i t , i t is n a tu r a lly re v o ltin g to most men' s p rin c ip le s o f b o d ily sa n i t a t i o n to have to clamp o v e r h is fa c e a d e v io e t h a t has been soaked w ith sw eat and d ir t_ of a n o th e r man' s ,fa p e _ a n d _ in to whioh one or m ore men h av e b re a th e d day a f t e r day! I t is to o muoh l i k e u s in g th e o th e r f e llo w ' s to o th b ru s h . The b e s t p r a c tic e is t o mark ev e ry r e s p i r a t o r s o eac h workman c a n i d e n t i f y h i s own, (d) Use, M aintenance and C are of R e sp ira to rs - P erso n al re s p ir a to r y p ro te c tiv e de v ic e s must be m a in ta in e d i n a c o n d itio n s u b s t a n t i a l l y th e same as when re c e iv e d freon th e m an u factu rer. D epending on th e d e n s ity o f th e d u s t re p la c e a b le f i l t e r s should be changed fre q u e n tly to p re v e n t th e ir becom ing clo g g ed and u s u a lly i t i s d e s ira b le to u se a r e s p i r a t o r w ith o u t a f a c e le t. However, i f th e y a r e c o n sid e re d n e c e ssa ry , th e fa c e le ts should be changed o ften to avoid sk in i r r i t a t i o n , A clean fa c e lt gives th e r e s p ir a to r a c le a n a p p ea ran ce and removes one o b je c tio n to w earing i t . The C o lg a te - P a lm o liv e - P e e t Company fo u n d t h a t t h e h a b i t o f some w o rk ers o f removing th e ir r e s p ir a to r s a t in te r v a ls caused sk in i r r i t a t i o n , Everytim e th e y d id t h i s , d u s t s e t t l e d on th e s u r f a c e s th a t la y n e x t t o th e w o rk e r' s fa o e and i r r i t a t i n g a r t i c l e s were tr a n s f e r r e d t o th e sk in when th e d ev ic e was re p la c e d . I t i s , th e re /f o r e , b e s t to have th e em ployee w ear h is r e s p ir a t o r c o n s ta n tly w h ile under exposure. In some c a s e s , o in tm e n ts o r p e tro le u m j e l l y h a s h e lp e d t o overcam e t h e i r r i t a t i n g e f fe c t of p o in ts th a t c o n ta c t th e skin. Where a c o n s id e r a b le number o f r e s p ir a t o r s a r e u se d , i t i s good p r a c t i c e to h av e a " R e s p i r a t o r Room" w i t h a n a t t e n d a n t who i s s u e s t h e r e s p i r a t o r s and c l e a n s , s t e r i l i z e s an d o th e r w is e k e e p s them in good c o n d i t i o n . R e s p i r a t o r s may b e c l e a n s e d by w ashing and b ru s h in g them w ith an a n t i s e p t i c so ap and warm w a te r. They sh o u ld be checked fo r damaged or im p ro p erly fu n c tio n in g p a rts suoh as rubber v alv e s e a ts and head-bands. I f d e fe c tiv e , th e s e should be re p la c e d by new p a rts , WHAT MEDICAL CONTROL SHOULD BE EXERCISED IN THE SELECTION AND SUPERVISION OF MEN WORKING ON DUSTY JOBS? - I t i s e s s e n t i a l t h a t a d e q u a te m e d ic a l o o n t r o l b e esev e re i s ecL, S uch c o n t r o l s h o u ld in c lu d e th e e x a m in a tio n , p r i o r t o i n i t i a l w o rk in g on d u s ty jo b s o f t h e w o rk e r t o i n s u r e t h a t h e i s a s u i t a b l e p h y s i c a l s u b j e c t . T h is ex>am ination sh o u ld p re fe ra b ly in c lu d e X -ray ex am in atio n o f th e lungs whioh p erm its c l o s e r c o n t r o l w i t h s u b s e q u e n t X -ra y t e s t s a s w e ll a s b e i n g a p r o t e c t i o n t o th e em ployer in th e event of any la te r le g a l actio n . A w orker, to be c la s s e d as p h y sic a lly s u ita b le , should be in a d d itio n , de te rm in e d to be a n o s e - b r e a th e r r a th e r th a n a m o u th -b re a th e r and th e n a tu r a l f i l t e r in g c a p a c i t y o f t h e h o s e s h o u ld be fo u n d t o b e s a t i s f a c t o r y , G,, Lehmann ( J , Ind,B jyg, 17,37 1935) in d ic a te s th a t th e " S ilic o tic s u s c e p tib ility of w orkers w ith poor na- f i l t r a t i o n i s muoh g r e a t e r th a n th a t o f men w ith good n a s a l f i l t e r s " . He a d js e s th a t jobs w ith a s i l i o o s i s hazard be h e ld only by men w ith good n a sa l f i l t e r s " j/ "^xd t h a t m outh b r e a th e r s a r e a n e s p e c ia lly b ad r is k . He s u g g e s ts t h a t th e " d u s t r e ta in in g cap a c ity o f th e nose be used as an index o f th e in d iv id u a l's q u a lific a tio n fo r w orking in a s i l i c o s i s producing atm osphere". I t is p o s sib le th a t S te r n s te in ' s technique fo r m easuring n a sa l re sista n c e (" In d u s tria l D usts - p#66) could be develop ed in t o a sim p le p ro c e d u re f o r s e le c tin g men b e s t a d a p te d t o d u s t ex p o su re. -8 1 - f o r d u s ty jo b s men who a re p a s t th e age o f 40 and n o t young men j u s t ta k in g up a tra d e . A ll workers engaged in harm ful dusty op eratio n s should be p e rio d ic a lly th o r oughly re-exam ined, in c lu d in g X -ray te s t s . P a r tic u la r em phasis should be placed on any in d ic a tio n o f sh o rtn ess o f b rea th and ch est pains R egulations should be enforced co ncerning th e tim e lim ita tio n of work o f any em ployees in v o lv e d in a d u s t p ro d u cin g o p e r a tio n . Suoh Company r e g u la tio n s c o n c e rn in g s a n d b l a s t i n g c a l l i n g f o r a f i x e d s ix - m o n th maximum p e r io d on su o h w o rk , a f t e r w hioh a minimum s ix -m o n th p e rio d away from d u s t p ro d u c in g work s h o u ld b e fo llo w e d more c lo s e ly . For p ro te c tio n from a le g a l angle, th e w orker should be given a f in a l th o r ough ex am ination in c lu d in g X -ray b e fo re b ein g perm anently tr a n s f e r r e d t o seme o th e r ty p e o f work, la id o ff or d ischarged . ' CONCLUSION There is s t i l l a trem endous amount to be le a rn e d about pneum oconiosis and d u s t- p r o d u c in g o p e r a tio n s . One th i n g , h o w ev er, i s c e r t a i n - t h e r e i s a v e r y d e f i n i t e tendency to re q u ire com pensation fo r in d u s tr ia l o r o ccu p atio n al d ise a se s. I f th e se co m p e n sa tio n c o s ts a r e t o b e k e p t t o a minimum an d th e h e a l t h and s a f e ty o f workman a r e t o be prom oted i t w ill b e n e c e ss a ry to make f u r th e r s tu d ie s and t o p ro m p tly a d o p t a d e q u a te p r e c a u t i o n a r y m e a su re s. Many o f t h e s e a r e now i n e f f e c t , t h e o th e r s .should be put in fo rc e as soon as p o ssib le . A fte r y e a rs o f stu d y and d ir e c t c o n ta c t w ith th e D ust P roblem , Mr, Dan H a rrin g to n , C h ie f, H e a lth and S a f e ty B ranoh, U n ite d S t a t e s B ureau o f M ines, h a s come t o t h i s c o n c lu s io n (Eng, & Min, Jo u r, M arch 1937 p p s ,119-21) w ith w hich we a re h e a r t i l y in accord "In th e maze o f u n c e rta in tie s connected w ith alm ost a l l phases o f th e c a u sa tio n and d ia g n o sis o f d u s t d is e a s e , ab o u t th e only r e a lly w ell-determ ined fa c t av a ila b le is th a t b reath in g la rg e q u a n titie s o f dust (o r p o ssib ly o f c e rta in d u st) over extended periods is lik e ly under some c o n d itio n s t o be harm ful to h e a lth and th a t su b seq u en t a l l e v ia ti o n o r c u re i s d i f f i c u l t o r im p o ssib le , T h e re fo re , i t would seem to b e lo g ic a l to t r y to p rev en t d u st fo rm atio n th u s p re v e n tin g i t from harm ing w orkers through r e s p ir a tio n o r o th erw ise. H ere is a r e a l job f o r th e e n g in e e r, and l i t t l e o r no h e lp can be expected in th e se v i t a l fu n ctio n s from any agency ex cep t th e en g in eers and o p e ra t ing officials g i "The m ost harm ful o f th e o rd in ary d u sts to b re a th is probably s i l i c a d u s t, b u t, on th e o th e r hand, n o t even f re e s i l i c a , supposed ly th e m ost d etrim en tal of th e s ili c a d u sts, is harm ful unless i t is b r e a t h e d , i n c o n s id e r a b le q u a n t i t i e s and o v e r e x te n d e d p e r io d s . No human b ein g ever liv e d any c o n sid e ra b le tim e on t h i s e a r th o f ours w ith o u t b re a th in g s i l i c a d u st ( f r e e s i l i c a d u s t) , y e t by no means a l l o f th e p eople o f th e w orld have or have had s ili c o s is . In o th e r w ords, th e q u a n tity of dust taken in to th e re s p ira to ry organs is a c o n tro ll ing fa c to r in dust re sp ira to ry harm fulness. "One com mon-sense answ er is t h a t any atm o sp h ere in w hich d u st i s v is ib le to th e naked eye is c e rta in ly to o d u sty to be breathed w ith s a f e t y b y human, b e i n g s , and th e w is e , f a r s i g h t e d , human em p lo y er w i l l im m ediately s ta r t to decrease th e d u st co n ten t in any atm osphere where d u s t i s v i s i b l e . A f te r he has e lim in a te d v i s i b l e d u s t, t h e r e mav -8 2 - s t i l l rem ain enough v ery sm all in v is ib le du st to cause h a m to th e h e a l t h o f th o s e who b r e a t h i - t , b u t i n a n y e v e n t i f he h a s e x e r t e d s u f f i c i e n t w e ll-d ire o te d e f f o r t to remove th e v is ib le d u st i t is c e r ta in t h a t much o f th e sm a lle r in v is ib le , and p robably m ost harm ful d u st h as a ls o been removed. "M anifestly, i f dust is kep t out o f the a ir breathed by w orkers, th e l a t t e r can n o t sucoumb to d u s t d is e a s e o f a r e s p ir a to r y c h a r a c te r ," I n d o s i n g , we acknow ledge w ith g r a ti tu d e th e s u p p o rt and c o o p e ra tio n o f _D r, Vi, J, D enno, G e n e ra l M e d ic a l D i r e c t o r , S ta n d a rd O i l Company (New J e r s e y ) w hose v is io n and a c tiv e i n t e r e s t in M ed io o -S afety problem s made t h i s D ust Study p o s s ib le . We a l s o a p p r e c i a t e t h e a d v ic e and a s s i s t a n c e r e n d e r e d b y r Mr, W. P, Y a n t, D ir e c t o r o f R e s e a r c h & D ev elo p m en t, Mine S a fe ty A p p lia n ces Company, P itts b u r g h , P en n sy lv a n ia , Dr. L eonard G reenburg, E x e c u tiv e D ir e c to r , D iv isio n o f I n d u s tr ia l H ygiene, D epartm ent o f Labor, S t a t e o f New Y o rk , New Y o rk , N,Y, Dr, R. R, S a y e r s , S e n io r S u rg e o n , U ,S ,P ublic H ealth S ervioe C h ief, D iv isio n o f I n d u s tr ia l H ygiene, N a tio n a l I n s t i t u t e o f H e a lth , W ash in g to n , D.C, Mr. D a n ie l H a r r in g to n , C h ie f , H e a lth and S a f e ty D iv is io n U n ite d S t a t e s B u reau o f M in es, W a sh in g to n , D. C. Dr, A, J , L a n z a , A s s i s t a n t M e d io a l D i r e c t o r , M e tr o p o l ita n L i f e I n s u r a n c e Company, New Y o rk , N,Y. Mr, E, H. B arlo w , C h ie f E n g in e e r , S ta n d a rd O il D evelopm ent Company, E l i z a b e t h , New J e r s e y . Mr, H, N, B l a k e s l e e , D ep a rtm e n t o f A c c id e n t P r e v e n t i o n , A m erican P e tro le u m I n s t i t u t e , New Y ork, N.Y. New Y ork. N, Y. July F ifte en th 19 3 7 R, S. B o n sib C hief S afety In sp ecto r S ta n d a r d O il Co, (N. J , )