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FILE NAME: Oil Industry and American Petroleum Institute (API) DATE: 1937 July DOC#: API176 DOCUMENT DESCRIPTION: Full Text Report - Dust Producing Operations in the Production of Petroleum Products and Associated Activities - Report of Standard Oil Co. >'^\*!'L5*Yj,i.u*-v*-,.'''U'u._>.<'.; vV'' rhAl ;'r* ;t,.v\-- V\'.: r:'1 .. - < )--:--I;::<.V:'J '. >vyV<\'-- ||<X\ IvT V wiaiii>iB''ieiika'|S.i.S|.iM^rPiSAu^dlM>i.i.a.*-'^t'f.*m;rf4-k>:Nti.'~.V:cvl ;PP l;h iv -V-' ' ' .i"1 ; 4'v` WKtt .--.*:?,V*W ; ' '. .:. A;' r - Yr-' :"ry': >' ' ''>- ; /;V/," ' ' ; ' :i\ :.;;/' ' V i i ;_ v m ^ rx** _-J^i) ! - : n " . li i? M igM Tfff **-- ^ * " * * * -- ******* . ;i-VV'*'; y.'/, ' j, '/ .i}... `V ;- . ' . .: .; * j-j '<*>. V * r FOREWORD Beoause it is the duty of industry to protect its employees and because no comprehensive survey of the hazards incident to oc cupational dust problems had yet been made, it was felt that here was an opportunity to render a serivce to the petroleum industry and its employees by making such a survey. It is hoped that the information presented in this bulletin will assist in finding proper answers to some of the many questions which have recently arisen concerning the health hazards of employ ees whose work involves exposure to dusts of various origin. An attempt has been made to consolidate opinions from, the most experienced students of occupational-dust problems to show the relative hazards of dusts and the duration of exposure which may prove harmful to the worker. Furthermore, a study of the prevalence of dust particles oc curring in various operations in the petroleum industry has been made and included in this report; also a description of the pro tective devices and equipment provided for the protection of the workmen. This report should serve as a guide to operating executives nd safety engineers in handling personnel and in providing adequate protection in dusty occupations. It should also resolve many of the ;fear3 and questions of industrial workers in these occupations. The study confirms an opinion that dusty occupations, thor oughly understood and intelligently handled should result in no Willard J. Denno. M. D. General Medical Director Standard Oil Company (N. J. ) MEDICO - SAFETY MEMORANDUM D U S T P R O D U C I N G OPE R A T I O N S IN T H E P R O D U C T I O N OF P E T R O L E U M P R O D U C T S A N D ASSOCIATED ACTIVITIES CONTENTS PAGE INTRODUCTION PART I - DUST AS A HEALTH HAZARD t ,, I - WET IS THE DUST PROBLEM SO IMPORTANT?.......................... 2 II - WHAT IS MEANT BY "DUST51?................... ........................ 2 III - WHAT ARE THE PHYSIOLOGICAL EFFECTS PRODUCED BY The Inhalation of Dust................................ 3 Silicosis in General......................................... 4 ' First National Silicosis Conference.......... .............. . 4 Silicatosis.................................................. 5 ... Asbestosis................................................... 7 17 - WHAT IS THE MAXIMUM PERMISSABLE DUST CONCENTRATION? Formula For Determining Maximum Permissible Concentration of Silica in The Air Breathed................................... 7, 8 Safe Dust Concentrations, Impringer Samples................ ..... 9 Y - HOW MAY THE CONCENTRATION AND CHARACTER OFINDUSTRIAL DUSTS BE DETERMINED?....................................................... 9 The Impinger Apparatus..................................... 10,11 The Zeiss Konimeter....................... ................. ...... 11 The Bausch k Lamb Dust Counter............................ ...... 11 PART II - DUST PRODUCING OPERATIONS STUDIED * WHAT ARE THE PRINCIPAL DUST PRODUCING OPERATIONS? I - SAND-BLASTING................................................... 13-15 II - FILTERING OPERATIONS.......................................... ...... 15-27 A - Filter Clay or Fullers Earth; What is Filter Clay or Fullers Earth?........................ How is Filter Clay Mined and Prepared?....................... How is Filter Clay Used?..................................... "Burning" Clay............................................ Charging Filters.......................................... Dumping Filters............. Composition of Filter House Air Borne Bust.................. Control of Filter Clay Dust.................................. 15,15 16,17 17,18 18,19 19,20 20,21 21 22 B - Contact Clay: Main Constituents of Contact Clays.................... ...... What is "Filtrol" and How is it Produced?................... What is the Chemical Composition of Filtrol?.......... ....... How is Contact Clay Used?............................. ...... 22,23 23,24 2^,25 25, 2S -2- PAGE C - Pone Black or Charred Bone; How is Bone Black Used...................................... 26 III - INSULATING OPERATIONS; A - What Physiological Reactions are Provoked by " Insulating Materials?.......... ............................ 27 B - What Are The Principal Insulating Operations and How Much Dust is Produced During Such Operations?.......... 27 . Insulating 12" Steam Lines.......................... . 27, 28 Insulating a 750-Pound Cracking Coil Accumulator..... . 28 , Insulating Treating Plant Acid Suction Line.............. *' 28 Insulating Cracking Coil Hot Oil Lines............... . 28 Dismantling or Removing Old Insulation............... ..... 28,29 Crushing Scrap Asbestos............................. . 29 Crushing Old Cork Insulation........................ . 29 17 - GUNITING OPERATIONS: What Is Gunite and How Is It Applied?....................... . Removal of Gunite Lingins................................... V - WELDING AND CUTTING OPERATIONS: 29,30 30 A - Welding Operations: 1. Electric Arc Welding............................... . 30 What are Coated Electrodes?...................... . 30,31 What do These Electrodes Contain and What Products Result From Their Use?................ . 31,32 What is The Amount and What Are the , ' Characteristics of Fumes or Dust Produced By The Various Electric Arc Welding Operations...... 32-35 What Physiological Effects on Welders is Produced by The Use of Coated Electrodes............ 35-37 2. O^y-Acetylene Welding................................... 37 Fumes or Dust Produced by O^y-Ac etyl ene Welding.... . 37 B - Burning or Cutting Operations: 1. With O^y-Acetylene.................................. Fumes or Dust Produced by O^y-Acetylene Burning.... ...... 2. With Natural Gas.................................... 37,38 _ 38 38 C Health Hazards Produced by Welding and Cutting Operations.... 38 VI - GRINDING OPERATIONS: What is The Composition of Grinding Wheels?................. Is Abrasive Dust Harmful?................................... 39 39,401 1 _ What are the More Frequently Used Types of Grinders. the Quantity and Character of the Dust they Produce?....... . 40 -2- PAGE C - Done Black or Charred Bone: How is Bone Black Used....................................... . 26 III r INSULATING OPERATIONS? A - What Physiological Reactions are Provoked by ` Insulating Materials?....................................... 27 B - What Are The Principal Insulating Operations and How Much Dust is Froduoed During Such Operations?......... . 27 . Insulating 12" Steam Lines................................ 27,23 Insulating a 750-Pound Cracking Coil Accumulator......... 28 Insulating Treating Plant Acid Suction Line.............. 28 Insulating Cracking Coil Hot Oil Lines................... 28 Dismantling or Removing Old Insulation.................... 28,29 Crushing Scrap Asbestos................................... 29 Crushing Old Cork Insulation.............................. 29 IV - GUNITING OPERATIONS: What Is Gunite and How Is It Applied?........................ 29,30 . Removal of Gunite Lingins.............. .'.................... 30 V - WELDING AND CUTTING OPERATIONS: A - Welding Operations? 1 Electric Arc Welding..................................... 30 What are Coated Electrodes?............................ 30,31 What do These Electrodes Contain and What J Products Result From Their Use?.................... . 31,32 What is The Amount and What Are the ' Characteristics of Fumes or Dust Produced By The Various Electric Arc Welding Operations...... 32-35 What Physiological Effects on Welders is > Produced by The Use of Coated Electrodes.... ........ 35-37 2. Osy-Acetylene Welding.................................... 37 Fumes or Dust Produced by Oxy-Acetylene Welding.... . 37 B - Burning or Cutting Operations ? 1. With Oxy-Acetylene....................................... Fumes or Dust Produced by Oxy-Acetylene Burning......... 2. With Natural Gas......................................... 37,38 38 38 C - Health Hazards Produced by Welding and Cutting Onerat ions.... 38 VI - GRINDING OPERATIONS: What is The Composition of Grinding Wheels?................. Is Abrasive Dust Harmful?.................................... 39 39,401 1 - What are the More Frequentlv Used Types of Grinders. the Quantity and Character of the Dust they Produce?.'...... . 40 -3- A - TANDEM FLOOR TOOL GRINDERS.................................. Dust Produced, by Tandem Floor Grinders..................... B - TANDEM BENCH GRINDERS....................................... Dust Produced by Tandem Bench. Grinders..................... Characteristics of Dust Produced by Tandem Benoh Grinders........................................ C - SINGLE FLOOR TOOL GRINDERS................... !.......... .... Dust Produoed by Single Floor Grinders.................. . Characteristics of Dust Produoed........................ . D - UNIVERSAL GRINDERS.......................................... Dust Produced By Universal Grinders........................ Charactersitics of Dust Produced........................ E - SURFACE GRINDERS............................................ Dust Produoed by Surface Grinders.......................... F - LANDIS TOOL GRINDERS........................................ Dust Produced by Landis Tool Grinders...................... G - YANKEE DRILL GRINDER........................................ Dust Produced by.Yankee Drill Grinder................... . H - AUTOMATIC CIRCULAR SAW SHARPENING MACHINE................... Dust Produoed by Yankee Drill Grinder................... ... I - AUTOMATIC BAND SAW GRINDER................................ .. Dust Produoed by Automatic Band Saw Grinder............. . J - AUTOMATIC BAND SAW LAP GRINDER.............................. Dust Produoed by Lap Grinder............................... K - PLANING KNIFE BLADE GRINDER......... ......................... Dust Produced by Blade Grinder...... ....................... L - LINDERMAN CUTTER GRINDER................................. ... Bust Produoed by Cutter Grinder......................... . M - GANG SAW BLADE GRINDER.................................... . .. Dust Produoed by Gang Saw Blade Grinder................. . N - EDGER SAW GRINDER......................................... .. Dust Produced by Edger Saw Grinder......................... 0 - CIRCULAR SLAB CUT-OFF SAW GRINDER......................... . Dust Produoed by Cut-Off Saw Grinder....................... P - "HOG KNIFE" GRINDER......................................... Dust Produced by "Hog Knife" Grinder....................... Q - CUTTER GRINDER............................................ . Dust Produced by Cutter Grinder.......................... . PAGE 40,41 41,42 41 41 42 43 43 43 44,45 44 45 45 45 45,46 45 46 46 46 46 46,4747 47 47 47' 47 47 47 47 47 47 47 47,48 48 48 48 48 43 fsgp: -4- PAGE Control of Dust from Grinding Wheels........................... 48 HANDLING POWDERED OR PULVERIZED MATERIALS? ... . . - A - LIME? (l) Ify'drated Lime............................................ (2) Lump Quick Lime................................. ......... What Physiological Effect is Produced by Lime Dust........... 49,50 50,51 51 B - METALLIC ZINC DUSTr Typical Screen Analysis............................. 51 Dust Produced...................................... 51 What Physiological Effect is Produced by Zinc Dust........... 51 C - ASBESTOS "FLOAT"? ' Dust Produced...................................... .......... ..Physiological Effect of Asbestos Particles......... 51, 52 52 D - GROUND MICA: Dust Produced...................................... 52 Physiological Effect of Mica Dust................. ....... . 52 ....... E - SULPHUR: ' . (l) Sulphur Flour................... (2) Crude Sulphur.................................. Physiological Effect of Sulphur.................... F - LITHARGE: ' Dust Produced....................................... Necessary Precautionary Measures When Handling Litharge................................ i......... 52 52,53 53 53 5*5,54 . G - SODA ASH: ' Dust Produced........ 54,55 H - TALC or "SOAPSTONE"r . .... . Dust Produced....................................... Physiological Effeots Produced by Talc Dust....... .......... , 55 55 I - GRAPHITE: . Dust Produc ed.......... ..................... ...... ,......... 55,56 ,J - SLATE FLOUR: ' Dust Produced................................................ 56 Effect of Slate Flour on the Lungs................. .......... 57 K - GRINDING DERRIS ROOT: ' Dust Produced................... 57 To What Extent is Derris Toxic?.............................. 57 L - GRINDING PYRETHRUM FLOWERS: Dust Produced............................. 57,53 M - MIXING AND PACKING "FLIT" POWDER: Dust Produced....................... 53 Filling Cans................................ 53 -y*- ; ' OTEANING. TUBES AND DRU^ - i _ CRACKING COIL SOAKING DRUMS; VA V . Dust Produc ed........... ........................... ? II _ c~r=`.:. :III ,, CRACKING COIL TUBES; Dust Produced........ .............................. WATER HEADERS AND BOILER TUBES; Dust Produc ed.............. ........ ........ Ccnaposition of Dust from Front Water Wall Header.... FOUNDRY OPERATIONS; 7 a.'Iv B:,v A - POURING MOLTEN METAL INTO SAND MOULDS............. r' B - "SHAKING OUT" CASTINGS............................ C - CLEANING CASTINGS; (a) Preliminary Cleaning...... .................. (b) Tumblast.............. ...................... (c) Sly Tumbling Mill........................... (d) Tumbling Barrels............................ (e) Air-Blasting................................ (f) Rough Snagging Wheels....................... (g) Fine Snagging and Polishing Wheels.......... (h) Cone Grinding Wheels........................ Average Dustiness of Cleaning Room Air.......... D - CORE MAKING....................................... E - SEPARATION OF BRASS FOUNDRY SKIMMINGS............. MASONS OPERATIONS; . 17 ;] y ..I 71 - TEARING OUT STILL FIRE BOXES.......................... - CHIPPING OR CUTTING CONCRETE.......................... - CHIPPING MORTAR FROM BETWEEN BRICK.................... - CRUSHING FIRE BRICK................................... - SHAPING FIRS BRICK ON EMERY WHEEL...................... - '^DISMANTLING MASONRY................................... XL - WOODWORKING OPERATIONS; A - BOX SHOOK MANUFACTURE (a) Resawing..................................... (b) Ripsawing.................................... J (c) Cut of Sawing................................. (d) Planing...................................... Dustiness of Shoolc-Factory Air................... 1 B - BELT SANDERS, SAND DISCS AND SPINDLES OR CYLINDERS: (&) Belt Sanders...^...... ....................... (b) Sand Discs or Wheels................... . (c) Sand Spindles or Cylinders................... C - MAKING WOODEN CRATES; (a) Band Saws.................................... (b) Railroad Saws.............. ,............... PAGE 58,59 59 59 60 60,61 61 61 61,62 62 62 62,63 63 63,64 64 64 64,65 65 65 65 65,66 66 66 66 67 67 67 6^,63 63 63 63.69 69.70 70 70 -6- PAGE - ROCK EXCAVATION: A - DRILLING.................................................. B - BLASTING.................................................. C - MUCKING..'.................................... D - DUST CONTROL MEASURES; (a) Wet Drilling and Wetting Down Rock Walls and Muck Piles......................................... (b) General Ventilation.................................. (c) Dust Exhaust Hoods on Drills and Other Mucking Operationsand LocalSources of Dust................. (d) Personal Protection by Means of Respirators and Positive - Pressure Masks....................... 70 71 71 71 71 71,72 72 PART III - MEASURES FOR REDUCTION OF THE DUST HAZARD HOW AN THE DS T HAZARD BE REDCED? J' g j .' ~ ] 0] ** ] ] j :o n c l u s i o n , A - DESIGN PLANT FOR DUST CONTROL........................... B - PROVIDE BUILDING VENTILATION............................ C - STORE DUSTY MATERIALS IN DUST-TIGHT BINS............... . D - ENCLOSE MATERIAL HANDLING EQUIPMENT.................... E - ISOLATE DUSTY PROCESSES................................. F - PROVIDE WET METHODS OF OPERATION........................ G - DESIGN EQUIPMENT TO CONTROL DUST....................... H - PROVIDE EXHAUST SYSTEMS................................ I - ESTABLISH MAINTENANCE AND GOOD HOUSEKEEPING PROCEDURE... J - PROVIDE RESPIRATORS..................................... (a) Air Purifying Types qf Respirators................. (b) Supplied Air Respirators........................... The Air Line Respirator................. ........ . Abrasive Blasting Respirator..................... (c) Acceptance and Use of Personal Respiratory Protection by Workmen............................ (d) Use, Maintenance and Care of Respirators........... WHAT MEDICAL CONTROL SHOULD BE EXERCISED IN THE SELECTION AND SUPERVISION OF MEN WORKING ON DUSTY JOBS?................ PHYSICAL EXAMINATIONS................................... DESIRABLE PHYSICAL QUALIFICATIONS....................... RE-EXAMINATIONS......................................... TIIE LIMITATIONS 74 74 74 74 74 74 75 75 75 76 76,77 77 78,79 79 79,80 80 80,81 80 81 81 81,82 1 STA N D A R D OIL CO M PAN Y ( Incorporated in New Jersey ) 30 Rockefeller Plaza New York, N. Y. MEDICO - SAFETY MEMORANDUM pU ST PRODUCING OPERATIONS IN TH E PRODUCTION OF PETROLEUM PRODUCTS AN D ASSOCIATED ACTIVITIES sgsU INTRODUCTION - Long looked upon as objectionable, dust today is also recogniz es" dangerous - especially with regard to occupational disease (Pneumoconiosis) and -ufffc explosions. Since the dust encountered in the production of Petroleum products * associated operations are non-explosive under ordinary working conditions, no ter attention will be devoted to this phase of the dust hazard. Studies have revealed that the time element (exposure) and the concentration ;e of the dust particles are major factors in producing health hazards. Here tofore difficulty has been encountered in determining actual dust concentrations and sizes of the particles, but recently developed instruments such as the Zeiss Koni- eter and the Bausch & Lomb Dust Counter make it stimate size of dust particles which, while not f' ;he dustiness of the area. possible to obtain dust counts and absolutely accurate, are indicative ^ " The data presented in this memorandum are based upon material taken from the available literature on the subject, upon field investigations and conferences with Technical specialists and upon 1008 actual sing a 20 to 30 micron (a micron is about dust counts l/25,000 of made with a Zeiss Konimeter, an inch) porcelain filter. |Y In the report of the Preventive Engineering Committee of the Air Hygiene -Foundation, Professor Philip Drinker of Harvard, chairman, and other technical specialists on the Committee write: "If tiie breathing of dust causes disability of any sort - silicosis is only one manifestation - then it follows that there must be some degree of air cleanliness from which no disability will result to the average man during the average working period. -U._ T ].f Jy 1--; "There is no satisfactory medical answer at present to this question, but the engineer is making a bad mistake if he lets men breathe heavy dust concen trations of any material. If no other reason for dust control can be found, then one should read transcripts of some of the recent suits at common law in which fantastic damages for alleged silicosis were granted to men who breathed dust containing little or no silica. The Courts and Compensation boards are not Impressed with subtle distinctions between dusts with. 10? and AO% quartz, especially when medical experts are reluctant to make definite statements as to the comparative significance of such differences. ] . "It would be well to realize that men working in dusty trades suffer far more from respiratory troubles of all kinds than do men who work in clean air. ; The evidence that excessive dustiness of any kind is harmful is beyond argu- PART I DUST AS A HEALTH HAZARD X - WHY IS THE DUST PROBLEM SO IMPORTANT? - Although the subject of the health ^V'workers in- dusty trades has been receiving considerable attention from students of "A trial hygiene for a number of years, the seriousness of this problem was not realised until it was brought sharply to our attention by the constantly grow- jf^^QQixatry-wide wave of lawsuits instituted in behalf of the victims in our oommon (t oourts, by the magnitude of the generous verdicts awarded by the juries and by a ent decision of the Federal Circuit Court reversing the substantial award of a ~i*+urv is a New Jersey case (Pennsylvania Pulverizing Company vs. Eldred G. Butler), fOwSig to these developments, the problem cannot be ignored or brushed aside as merely another form of "racketeering" by unscrupulous lawyers and conspiring doctors. Dodging the'issue cannot provide the needed solution because even the most unscrupulous Tlawyers cannot create a pathologic lung at will and, furthermore, even the most skep't i e of coroners frequently finds himself corroborating a diagnosis by his postmortem ~orr^Hnation. Enlightened industrialists and the medical profession as well as the '] bench and bar, have came to the realization that exposure to certain kinds o f dust, | such as those containing considerable amounts of quartz (silica), has increased the unhealthy bodily condition and death rate from respiratory diseases; while m<3tallio idusts, such as lead and its compounds, have been associated with general systemic poisoning of workers. "Silicosis" is now a definitely recognized disease which is destined to become one of the foremost and most serious of occupational diseases of -the .future because the number of workers in dusty trades is larger than almost any 3 other group exposed to a single known industrial hazard. The McCaffrey Act, which 3 -became effective September 1, 1935, amending the New York Compensation Law, included silicosis as an occupational disease subject to compensation. tfiu. . Sixteen states, as well as those of the Federal Government and of Hawaii, Puerto Rico, and the Philippine Islands (U.S.Dept,of Labor Bull,No,625,Bur.Labor Sta tistics), have Workmen's Compensation Acts which include compensation for occupational diseases, either expressly or by judicial interpretation, or specific occupational disease acts. "r II - WHAT IS MEANT BY "DUST"? - According to Webster's Unabridged Dictionary, "Dust" may be defined as fine, dry particles of earth or other matter so comminuted that they may be raised and wafted by the wind; that vdiioh is crumbled to minute portions; fine, powder. A3 pointed out by Philip Drinker in a paper read before the Chemical Section of the National Safety Congress (held in Atlantic City, October, 1936), dust3 include all types of dry earthy particles small enough to be blown about by ordinary air currents. Dust suspensions may be generated as the result of grind1 ing blasting, or comminuting process; or they may result from the handling of fineI ly divided materials as in mixing .processes, in sweeping, or the blowing about of wood flour, plant pollens, or oommon road dust. There is no chemical limitation im plied by the term "dust" while the range in size of dust particles extends from the sub-microscopic to small sand grains. Mr. D. Harrington, Chief Health and Safety Branch, U. S. Bureau of Mines advises that dust as applied to health and respiratory conditions may be wet as well as dry. Under some conditions, such for example as in wet drilling in mines, the escaping air from the drill hole may (in fact generally does) contain a certain amount of entrapped solid material which undoubtedly is wet rather than dry. yet it remains in the air sufficiently long in some instances at least to be breathed by the workers 'to contribute to possible health trouble. The size of dust of importance from a hygienic standpoint are those under ten microns. In fact, the sizes found in industrial atmospheres sire under two microns for the larger majority of particles, say 90 to 95 per cent. Physiologically, there are al most as many different classifications of dust as there are authors on the subject. However, according to Professor Drinker ("Dust, Fumes and Smoke". International La*bor Office, Occupation ana Health Vol.1, 930, P.603) all of these classifications ithout much practical importance, since in daily practice in industry the harmful . j_s exercised more frequently by dusts mostly of mixed origin. 3esides, what is 1**. important is the physical and chemical constitution of the dusts nd consequenttheir action on the system. hafcxil - WHAT Xt 132 EFFECTS PRODUCED BY THE INHALATION OF DUST? - To harmful from a respiratory viewpoint/ dust must be of sufficient finess to pass Tthrough t^ e ^ s a l filters and be retained in the alveoli (minute air sacs) of the particles found in autopsied lungs are of the order of one micron (a micron liru q/lOOO of a millimeter or about l/25,000 of an inch) or less in size - about the ^aize of the common bacteria. Some dust particles found in lungs are as large as ^ f i v e or six microns although these sizes are rather exceptional. There are five distinct types of reaction produced in man as the result of inhaldust. These reactions m a y b e broadly classified, based on the primary cause, as j? follower ry-. r \ Those which result in lung fibrosis, commonly referred to as moconiosis. These dusts contain free silica, asbestos, etc. ever, it is not necessary for fibrous tissue to be formed in for the disease to be classed as "Pneumoconiosis". pneu How order Those whioh are toxic and are absorbed into the blood stream such as lead, cadmium, etc. . Those whioh result in what is commonly referred to as metal fume fever; such as zino oxide, etc. Those which axe allergic in character, such organic dusts an pollen, pulverized wood and flour, etc. The breathing of pulverized wood and flour is frequently associated with tuberculosis. Those commonly referred to as "nuisance dusts". These may cause ir ritation of the respiratory tract or passages and may cause con siderable discomfort, also headaches of the dry "nasal" passage or sinus type and exposure to them may be associated with a high, in cidence of respiratory illness. The rate and extent of these reactions are dependent upon the resistance of the indi vidual,'*the exposure period (concentration of particles and length of exposure) tem- .perature and humidity of the air, rate of work, and the percentage of ingredients whioh are harmful. , Owing to the length of time required to obtain a reaction by inhalation meth ods, the United States Bureau of Mines and the Public Health Service adopted about twelve years ago, a method of injecting small quantities of the dusts to be studied into the peritoneal cavity of guinea pigs. ("Response of Peritoneal Tissue of Dusts Introduced as Foreign Bodies" by Dr. John W. Miller, Dr. R. R. Sayers and WmP, Yant, Jour.Amer.Med. Assoc. Sept. 22,1934 - Vol. 103, pps. 907-911). It was found that iden tical reactions occur in each animal injected with the same dust under the same con ditions and examined in the same time interval after injection. These reactions were essentially the same microscopically as that produced in the lungs and the gross ap pearance of the dust nodules was sufficiently differentiated to afford a means of classifying the physiological response to the du6ts. There are three types of reaction: An absorption or dissolution of the dust. A proliferative reaction. An inert reaction. -4- eSt" 'art reaction, the dust neither caused an increase in the size of the nodules _oeared from the tissues; instead there was more or less a change in its dis- Soapstone, carborundum (Silicon Carbide), jeweler's rouge (Ferric Oxide), Fv- -- ., _ ooal, bituminous coal and certain filter clays have inert reactions. Cal- limestone, precipitated calcium carbonate, gypsum, and Portland Cement exhibit- ^ S ? >iigL-^Borjrtlon reaction. Quartz, chat, certain filter clays and flint produced a KSliferative reaction. . E _ _ T h e physiological response to the injected dusts were found sufficiently well r*^vd ia 90 days to determine the type of reaction, particularly where the reaction E of absorption or proliferation. Since the reaction elicited by dust was ^tamt nr,d uniform in all of the animals injected with the dust, it is believed Lha-fc^this response of peritoneal tissue to various dusts can be used as a test to de[09 the possible harmfulnes's of industrial dusts. fibrosis-producing properties of a Georgia filter clay (30-60 mesh grade) t sampi of American contact clay and a German contact clay were tested by the Intra- Ceritoneal Method, undem the direction of Dr. R. R. Sayers, Medical Officer in Charge, U. S. Public Health Service. The Georgia filter clay showed an inert reaction ~]with a slight tendency towards a proliferation in the 90-day test. The American corn etact lay showed an inert -reaction with evidence of some slight absorption or dis appearance of seme part of dust in the 180-day tests. The German contact clay caused 33the formation of light yellowish-brown nodules and as the interval between the in- jgjjection and the examination increased the nodules became somewhat flattened, but the fl-mnrrrtt of dust and the approximate size of the nodule remained the same throughout ,the entire period (90-days) of the test. This can be considered an inert reaction; jbut* as the dust does not disappear from the peritoneum it should be considered as po- -=*tentially harmful though not as dangerous as pure silica. . -.y'V .In. commenting on the results of the -tests with the Georgia filter clay and the Aaerioaa contact cls.y, Doctor Sayers advised that the results of the test indicated 3that the filter clay is more harmful than the American contact clay because the dust rj remains inert in the tissues as this .was the largest portion of the dust and the in~ j ert appearance of the lesions was the most prominent. The modification of the reac 3 tion in the filter clay can be attributed to the presence of 5-10 per cent, quartz (Petrographic), Gypsum in the American contact clay may account for the slight ab- Jsorptive reaction. Doctor Sayers advises that an inert dust, if breathed ia. suffi cient cone Nitration, may be harmful. These tests were made in accordance with the procedure described in Reprint #1608, Public Health Reports, Yol. 49, No.3, January 1 19, 1934, pps. 80-89, The inhalation of dust gives rise to "Pneumoconiosis" a term derived from the Greek pneumon, lungs and konis, dust, and used to designate a pathological condition of the lungs caused by the inhalation of any dust. It includes SILICOSIS, a chronio disease of the lungs caused by the inhalation of minute particles of free silica (Si02) dust which produces a permanent incapacitating alteration of the lung tissue; ANT.HRACOSIS, the- black lung of the miner due to ooal dust; ANTHKACO-SILICOSTS, the newest of our mineral dust affections and introduced by the United States Public Health Service as a result of their studies in the Anthracite District of Pennsyl vania. This affection is the result, of breathing anthracite coal dust that contains silica. The common name for the affection is "Miners' Asthma"; CHALIC0SI5, the gray-black lung of the' stone-cutter due to stone dust; ASBESTCSIS, in asbestos workers due to asbestos dust; SIDEROSIS, due to breathing dusts of iron ore (The lungs are yellow or red from metallic oxides generally of iron. ); 3YSSIN0S1S, due to cotton particles and vegetable fibre dust, and PNEUM0N0ULTRAMICRCSC0PICSIL1C0V01-- CA.NCK0NI0SIS, a special form of silicosis caused by ultra-microscopic particles cf siliceous volcanic dust. Silicosis, Asbestosis, and Silico-Anthracosis are rhe only ' recuire practical attention. i i -5- . /pSsT While the "tyl5 Pulmonary lesion depends on the particular dust inhaled, the ^ pathological principle is the same in all forms of the disease, namely, an -under ^>i-brosis and replacement of the elastic lung tissue by a hard unyielding fi- ^ ^ i s s u e . All occupations that expose men to large amounts of dust may give rise r-^shrous oconj_osis but not necessarily to silicosis. It is now generally agreed that ^rder to produce the latter, (silicosis) inhaled silica dust must reach the lungs chemically uncombined condition, in very fine particles not more than ten mi ns (10 /25,000 inch) in diameter and in sufficient amount and over a sufficiently 2 r period of time. In relatively recent literature it appears that the proponents ^^frthe idea that only "free silica" is harmful are beginning to have some doubts and r> have the thought that possibly some silicates may under some conditions be harm : Generally speaking, the necessary length of exposure to produce silicosis is in ''^direct proportion to the sire of the dust particles and inverse proportion to the '^dust con0entration and the amount of free silica in the dust. Silicosis is char- ^aoterired anatomically by a generalired fibrosis of the lungs and clinically by short- -S^ness of breath, decreased chest expansion and a progressively lessened capacity for ^work which is out of proportion to the objective physical findings. The effect of ex *?- g-ure to dust such as silica is cumulative, the rapidity of development of the dis ' ease depending upon the time and amount of inhalation. Silicosis may develop to the ^point of causing symptoms only after several years exposure to silicious dust, but it A jnay be progressive in some cases even after exposure has ceased and may cause symtv* ' toms or become disabling long after the workman has left the environment that caused -`the condition. Some may improve or at least remain stationary in the absence of in faction. Watkins-Pitchford (J. Ind. Hyg. 9,109 - 1927) tells of Welsh miners who passed --pthe' physical examination for enlistment in the British Army, fought through the World '/war, then came back to England, and died of silicosis. Unfortunately, it is not -stated whether these persons died from silicosis complicated with tuberculosis. Brit- iton and Head (J.Am.Med.Assoc, 96, 1928 - 1931) give more detailed descriptions of 7? similar latent cases in the United States. ' i r~'r ] as ' Silicosis in General - It is generally agreed that silicosis may be defined , "A ohronio disease due to the breathing of air containing silica (Si02), characterized anatomically by generalized fibrotio changes and miliary nodules in both lungs, and clinically by shortness of 1 breath, decreased chest expansion, lessened capacity for work, ab sence of fever, increased susceptibility to tuberculosis (some of al!^ of which may be present), and by characteristic roentgenolo 3 gical findings," _ , In other words, silicosis is a disease of the lungs in which the normal lung tissue is replaced by scar tissue due to breathing air containing silica dust. Un 3 fortunately there is no known cure for silicosis - but SILICOSIS and nearly all ] other forms of dust diseases CAN BE PREVENTED. Recognizing the wide interest and even hysteria among apprehensive employers against whom claims had been filed by alarmed workers, and the necessity of thought J ful consideration of the silicosis problem, the Secretary of Labor on April 14, 1936 called the First National Silicosis Conference attended by more than 300 persons representing workers, employers, State and Federal Agencies, Insurance companies, and other interested groups. Four Committees were organized to study specific phases of the silicosis problem; and assemble the essential facts about silicosis in a series of reports; also to present specific suggestions for silicosis prevention, and straighten out other difficulties that silicosis has created. Reports made by these Committees were formally adopted at a second conference held February 2nd and 3rd i 1937 in Washington, from which we quote: -6- "While a fev; Persons maY still be of the opinion that such workers" ("Workers having silicosis) "are 'through' and doomed to an early death, every k tudv conducted thus far confirms the fact that the great majority of these ^eI1 will not necessarily progress from bad to worse. Perhaps it may be wise -'to transfer some workers to other employment, but many may be continued at StfiSp?.?their regular occupations if known methods are applied to control the dust and if special care is employed to prevent the development of tuberculosis, ! pneumonia and other lung complications". ."Contrary to popular belief, silicosis is slow to develop. Usually it takes seven years or more of exposure to silica dusjt for a worker to contract the .Iseasel "T t -is'said that a few cases have been known to develop in as short period as l-l/2^ years, but these were under extreme and unusual conditions. tjgggfrOn the other hand' many workers have labored under ordinary exposures to llflfg silica for more than 30 years without demonstrating any trouble whatever that Jlgpf'could be diagnosed as silicosis". For the convenient diagnosis of silicosis or of silicosis complicated by tu- Lberculosis, the pulmonary changes are classified in three stages by Drinker & Hatch ^("Industrial Dust" - 1936). In the first stage, the disease produces no diabiliiy. ''The victim can work just as well as ever. In the second stage, his respiration is 1affeoted; he is bothered by dyspnea or labored breathing. In the third stage dysJpnea becomes severe and he is likely to contract pulm onary tuberculosis, generally with fatal results. Whether he contracts tuberculosis or not, the advanced sili3 ootio is far below normal and is very susceptible to all respiratory diseases. 3 ajr'r~ These three stages of silicosis can be distinguished by X-ray. A comparison v `of the X-ray plates of a silicotic with those of a normal person of" like age and I physique shows, in the first stage, distinctive shadows, evenly distributed in both * lungs. These maybe missed or misinterpreted by anybut an expert; but the changes in the second and third stages are obvious even to a layman. It is, of course, es- Jj sential that the X-ray plates be properly made. Dr. Pancost and Dr. Pendergrass of the University of Pennsylvania have given extensive study totheinfluence of X-ray technique on the diagnosis of silicosis. Pendergrass is of the opinion that shadows ~1 and appearances of fibrosis can be actually produced by the technique employed. 1 Under other conditions, existing fibrosis can be entirely missed by use of improper 3technique. T>. Silicates as a class are by no means R. Sayers (tJ.S. Public Health Bulletin 221) harmless. It was pointed out by Dr. R. that Miners* Consumption was rather com mon in the Broken Hill district of Australia where the rock contains considerable sillimanite (Al SiOs), fibrous silicate, and a rather low percentage of quartz (12.23^). The studies of Badham (Rept. Dir. Gen. Pub. Health, New South Wales) give con siderable support to W. R. Jones' (J.Hyg. 15,307-1933) contention that silicates, particularly the fibrous varieties, may well be the cause of pulmonary disability. Badham in 1927 coined the word SILICATOSIS to cover disability from the inhalation J of silicates. Other silicates such as Talc (H2 Mg (Sj.0 3 ))4 ; Shale; Kaolin (H4 Alf. Si2 0g); Feldspar; Cryolite, (Na3 AlFg ); and pure Mica give much less specific changes than quartz. A moderate fibrosis may appear after exposure to numerous materials but this fibrosis is usually not disabling. According to Dr. Lanza, "Silicatosis" is not a recognized term in this country and disability from the inhalation of sili cates has not been proven. ` Dr. Cary P. McCord (ind. Med. July 1933, pps. 4-12) states that all silicates taken into the lungs, of particle size capable of passing the cellular membranes, are likely to induce some fibrosis in excess of normal but the progress of such silica tosis is not nearly so rapid as for silicosis. Tuberculosis rates are high in sili cate using industries. Antecedent tuberculosis, quiescent, may flare up as a result . -V*..?. -7- cNc.i., Ft* B3CPO8UT0 to silicate dust. i*bestosis - According to authorities oit ed b^'Drinker & Hatch in their hook trial Dusts", the pathology produoed by asbeirtosSis not like that of silicosis. ^ tf, Gardner of Saranac Lake is of the opinion.thkt the asbestos fibers group J*ut the neck of an alveolus and shut it off, oausing-^what is known as "Atelectasis", ^ ' i , no definite migration or transportation ofthe dust particles to the lymph Lg and no fibrous nodules. As the ateleotatio areas,' increase the reduction in In area causes serious dyspnea or laborered breathing,:. Dr. A. J. Lanra (U. S.Health ts. 50 j 1 - 1935) suggests that the enlarged hearts'noted frequently in his I ses* of seoond stage Asbestosis may be due to the inor.eased load on the heart. It Ikes more work to pump blood through the fibrosed than-through the normal lung. Re- lat."penological studies from human lungs from oases of asbestosis'have indicated a ;3 'ffuse typ of interstitial fibrosis with a certain amount of emphysema. 3-* (A *17 - WHAT IS THE MAXIMUM FERMISSABLL DUST CONCENTRATION? - There appears to be a I ide variation in the maximum concentration of dust which might be inhaled without 't nbsequent injury to workmen. Some dusts (as lead) are determined by chemical :l i tothods and the oonoent rations in air are reoorded gravimetric ally as milligrams per . I ubio meter. However, bHe available information on the amount of lead dust that is ri jjjaful and the methods of determining lead are better and more accurate than those ll silica dust. It is rather well.agreed that an intake of about 1.5 milligrams of ; i-r Jead" a day, whether this is acquired by breathing dust or by drinking water that con K tains lead, is the maximum allowable quantity. Others (as silica, where size is a .IS* factor in determining dangerous particles), are usually given by count. Neither il Sethod tells the whole story, but in both eases it may be possible to secure the in formation neoessary for the purpose. O&S" The maximum silioa dust concentration considered permissible in the air breath- d by a workman at any point in the normal breathing zone has not been definitely es- rablished. There is considerable difference of opinion regarding the range of par- tides that are oounted when using the Publio Health Serrioe technique and light v? ,,field illumination. Bloomfield of the United States ^Publio Health Servi.ce and Brown yH' of the United States Bureau of Mines oontend that they oount particles from one mi- , Ai`, Jron and upward, or even 0,7 micron and upward. The Industrial Commission of Wis- onsin and its Advisory Committee, composed of both employers and scientists, how- ' * ever, agreed in 1932 on a tentative figure of 15 million oountable particles under '/ (ft iO miorons in longest dimension with free ailioa ocntent of 35 per cent in a cubio kV) .U oot of air as determined by United States Publio Health Servioe technique. Varia- | "T t ions in fr6& silioa content will make proportional inverse ohanges in this standard, i : In the case of practically pure silica, the permissible dust oount should probably )*d Ik "Tnevor exceed 5,000,000 countable partioles. By oountable partioles is meant those Jpartioles between 0.5 to 10 microns in the longest dimension. Particles of this * f ^ size are the ones that are believed to cause the greatest damage and form no visible -.cloud. Dust partioles smaller than 0. 5 miorons in the longest dimension are not jordinarily oountable. Dust partioles larger than 10 miorons in longest dimension do --not ordinarily reach, parts of the lung where they can produce injury of a respira tory nature. Most industrial dusts have but few partioles above two or three mi- Jcrons in size. They are usually about 90 to 95 per oent. below two or three microns and750 per oent. below about 0.5 to 0,7 microns. An exception to this would be a . dust sample taken olase to the point of generation of dust and before the larger partioles had time to settle out of the air. In South Afrioa the figure is 1 milligram per oubio meter (or 300 particles per cubio oentimeter. or approximately 8.5 million per oubio foot.) Dr. Lanza found )in 1917 in the Joplin, Missouri district that with good engineering practice, a J figure of 1 milligram per 100 liters of air could be attained. This value attribut ed to Lanza appears too high in. comparison with the South African standards. As there -8- . V 000 liters in oubio meter, it would indicate,_tha.t Laura's estimation repreS~\ 'jomething of the order of 80 mil~lion part'i'l~es'-per cubic foot. With good en- NiTeeriBE practio lower conoent rations than this o'an be obtained. In fact the ex"Evienee in South Africa and also the present experience in this country indicates cnn readily be kept below one-tenth of this value by using ordinary good % ^ ieea. . The United States Publio Health Service.in its recent study in-the- an ' region of Pennsylvania, found that 50 million particles per cubic foot with oent. quartz in the ooarse dust and 10 million particles per cubic foot with er oent. quartz were apparently satisfactory and. often were attained. The figure -ST10-20 million, particles per oubio foot for granite dust with 35 per cent, quartz 25*tent is often quoted from the Vermont granite studies of the United States Publio Health Service. From a consideration of general experience, Cummings suggests 5 mil lion particles per oubio foot as a threshold for dusts high in quarts. This figure for based upon a combination of South Africa, Australian and American experience but ticks entirely any published data in its support. JSEjS According to studies quoted by Philip Drinker and Theodore Hatoh in their book [industrial Dusts'* 10 to 20 million particles per ubio foot by the impinger sampling method, light field counting is a reasonable figure for'cement and limestone. Recent Work by Dreessen oonfirms the universally accepted opinion that dusts high in caloite land low in quartz do not produce disabling fibrosis. The threshold figure, of 0.15 Jmilligr*10 per oubio meter i3 given for lead dust, presumably litharge and white lead, -r- othe*....soluble lead 3alts. ' .. "" ' .... . It should be noted that many of the data were not determined as the Medical '^requirement, as attainable in good praotioe and apparently satisfactory g'from a safety standpoint. It should be further noted that the accepted figures are only relative due to the indefinite powers of resistance of an individual which are !'Wn unknown quantity. One individual might resist a proportion of 200 particles per ;-'cubio centimeter, while another would react unfavorably to 50 particles. The work- 'er* s physioal condition prior to the exposure is of great importance, since a young, healthy individual usually can stand a higher concentration or longer exposure before the first stage of silioosis is developed. However, far greater influence than physical oonditioa might be the ability of the nose and respiratory passages to ar I rest dust. . . .>V , - .vV\ : In their report to the National Silioosis Canfrenoe the Committee an Pro- vention of Silioosis through Medical Control pointed opt that sinoe standards of safe 1atmospheric*dust concentration, based on medical findings have been established for ^only a few industrial dusts, and in view of the fact that considerable study and ia * vestigation will be required to establish standards for other industrial dusts, some tentative standard would be useful. It was also stated that this arbitrary istandard "^ should be based upon what is believed to be within the limits of good engineering praotioe provided, it will largely control the silioosis hazard for most industrial r exposures. They, therefore, suggest that ` x Jr "The maximum permissible concentration of silica in the air breathed might be expressed by the following formula. (Determination of dust concentration according to technique described by United States Publio Health service in Reprint No. 1520 from Publio Health Reports. March 18, 1932): Multiply the percentage of' free silica by the total particle dust count. If the result is under 5 million, the oondition may be con sidered permissible. If the result is ever 5 million, the condition may be considered too high. For example, l 10% free silica with an average total dust oonoerrtration of 30 million particles per cubic foot would give .10 times 50 million* which equals 3 million (good pridtioe)) 30#, with arerag total dust concentration of 50 million, would'equal ,3 times 50, or 15 million 9 (unaatisfactory)*. jliig. formula is not applicable to any dust containing less than 5# free silioa," M| a p j - * . f. ; '~ " Sodor Hatch in his article "Some Fundamental Data on Mechanical Dust Traps" (Tech, pyk.Ho 637-i* 60, Amer. Inst, Min. & Met. Engrs., Aug., 1935) gives these . Safe Dust Conoentrations. Impinger Samples; * ' ' (Light Field, Low Power Counts.) ' '* . * Hind of Dust Maximum Permissible Conoentration He-__________________________________________ __________________________________ lYconfcaiJoimg no Silica. ................. 50 millions per oubio foot {{"Containing any small amount of silica, ^re oombined. '*..................... 30 " " " w rCOTtaining 20 to 40 per oent. Free S i l i o a .......................... 1 " " " n ^Greater than 40 per oent. ' jjg--.,..Free Silioa .......................... v ; .5 " " " " (Preferably as much less as possible) -Jr.' Hr H. Sayers, Medical Offioer in Charge, Industrial Hygiene and Sanitation, U, S. Rblio Health Serrioe in answer to a question as to permissible dustiness writes: I vgj;-:., "During reoent years, it has been 0U3ternary to recommend threshold or permissible dust limits ranging from fire to ten million partiolos per jv oubio foot as determined by Publio Health Serrioe technique,, especially with dust in whioh the percentage of free silioa.is aberre fire per cent There is no basis for the application of this oriterien to all dusts, but it is generally considered a safe praotioe and one whioh oan be attained in most industries by exhaust ventilation, wetting, or other methods of t'.dust ocntrol." . ' . .. As pointed out by Drinker and Hatch ("Industrial Dust" - 1936) It is unfort, aately impossible to evaluate dust exposures with the arithmetical nicety that we rphould have liked yet it is oommonly olaimed - by laymen - that prolonged exposure to i i off oonoentrations is just as serious as short expostures to heavy oonoentrat ions. This olaia is oontrary to a fundamental law of physiology. In disoussing the sub- ieot Clark and Drinker ("Industrial Medioine" - 1935) remark that a sub-three-- old stimulus (dust inhalation) for a long time produoes no reaction whereas a rela- ively brief super-threshold stimulus may cause a reaction". If workers are exposed to sudden heavy oonoentrations, the threshold values suggested previously would be korrespcndingly lowered. However, most threshold values are weighed -- an average Jjf the ranges. i T - HOW MAX THE CONCENTRATION AND CHARACTER OF INDUSTRIAL DUSTS BE DETEMINED? phe properties of a dust whioh determine its harmfulness have been shown to be its composition, oonoentrat ion (the quantity suspended in the industrial atmosphere), and its partile sire. The methods used for the determination of the concentration and Character of industrial dusts vary from a routine dust count for the purpose of -evaluating the efficiency of dust control methods to a detailed study of both the concentration and the character of the dust in connection with medical and engineer ing surveys. The Impinger Apparatus developed at the UniVed^States Bureau of Hines, vyrgh Experiment Station "by George Smith andvLeonard Greenburg, (Described in Uo. 1528 from the Publio Health Reports Vol.47, Ho, 12, March 18, 1932 pp, r^ S 75) has been employed for more than 13 years.'aa.a standard instrument for dust l^^dies. In this apparatus samples of air are drawn into an impinger tube and flask the.dust particles are thrown or impinged on a; prepared wetted glass collect or--* The rate of air flow is fixed at one oubio foot per minute while the j^ation of the sampling period is dependent upon the dust concentration. The air es through an orifice in the bottom of the impinger tube and strikes glass col- Hi^oting plate whioh is submerged in 3 cm* depth of distilled water or some other ffluid with satisfactory wotting properties, (if water is used as. the fluid in the ' *impinsr, silica particles are dissolved-- hence not available for oounting -- unless ^the-laboratory (oounting) work is done within a few hours of talcing the sample,) ^Ihis affords the means for aoourately determining the quantity and size of the par- tides. The liquid is then thoroughly shakon to obtain a uniform distribution of -the particles) filtered to remove those over 40 miorons in sise and again agitated. tSamples of approximately 1 oo, are taken by means of a pipette and plaoed in Sedg- ifiok-Rafter oounting oells. The use of a suitable miorosoope equipped with a Whipple jiiorometer diso to aid* in oounting. will permit the determination of the number of ^j^ioles in one quarter of the miorosoopio field,. From this figure, the number of T partiles of dust in 1 ou.it. oan bo calculated. One special advantage of this apjr p^ra.tus is the fact that analysis of the sample oan be determined by counting, by .iweighing or by chemical analysis. The impinger method is neither simple nor extreme'''ly complex) however, reliable results can be obtained only by well trained, ocmpe- tent "d experienced investigators. However, owing to the wide use of the impinger Jiff previous investigations that have been correlated with the pathological findings, S^sn impinger should be used for any investigation which is to inolude pathological ^findings or where the results are to be introduced*as evidence in court. Scane state -J^oodes on dust oontrol recognise the impinger method. The United States Bureau of /.Mines has practioally oompleted the development of a "Midget" impinger whioh. has most w/'of the good oharaoteristios of the impinger but lacks most of its drawbacks. This ^midget impinger will soon be available and will greatly simplify both sampling and '' ^ oounting. a-- . . . . . . v Other devioes are also available for sampling of dust over a continuous period "namely, the eleotrie preoipitator, the paper thimble, the eleotrostatio precipitator, fand the hot wire thermal preoipitator. The English are working on a dust sampling Sinstrument whioh precipitates the dust from the air by thermal means ("Physical Methods fox* the Estimation of the Dust Hazards in Industry", by H. L. Green * H. H, Watson, Privy Counoil, Medieal Research Counoil, Special Series No. 199, His Majesty* s Stationery Offioe, London, (1935)). The U. S. Bureau of Mines has been us- ,|(ing an eleotrio precipitator similar to those described by Drinker ("Alternating ^/Current Precipitator for Sanitary Air Analysis) I - An Inexpensive PreoipitatorUnit" J by P. Drinker, Jour. Ind. 3yg, Vel. 14, 1932, p.364) for collecting samples of the test suspensions used in testing meehanical filter respirators for permissibility. -TT' A number of instruments are available for making dust determinations for cor** j^trol purposes. Among these is the Konimeter which oalls for but little skill in Jr sampling. It is light, simple and quick to handle, needs no power for operation *nd requires only a miorosoope for counting the particles. The Zeiss 52S3aL2i7 consists of a miorosoope which, gives a magnification of 200X, an air pump, a dust filter to p remove very ooarse dust particles, a sample disc and a miorcmeter ruled in square millimeters. The air ptaap drives a measured quantity of air against the sample disc `-'whioh is covered with a stioky substance (glycerine jelly). This sample forma a dust * spot which can be examined under the miorosoope for a general idea of the nature of _ the dust and the relative quantities present, or for an actual measure, a "dust count which shows how many dust particles are present in one cubic centimeter or in one litre of the air samples examined. The Konimeter has been used very widely in ! "'rfeh Afrio* (Final Report of the Miners' PhtMsis'.Pr.errention Committee, Johannes- ^ 11991199, p..10) and also in Canada The U. S. Bureau of Mines has also vised it in *5?' f its dust studies In discussing the value ..ofthe Konimeter in their recent ces U"Aindustr-ial- D-ust"- (*McGraw-Hill Book Co., New York; and London - 1936) Philip jriuker a_n_ d3 TfT thV e^ oa. d3 oa rea Hatch 'nIt is the most of the THiae rm vw as rd SC choa oa ll of a I ' Publi4 o IHT ealt4 *hU writer M n 4 4 - a . - compact and simple sampling devioe. Space is provided for thirty samples on a single diso and no auxiliary souroe of power is required for its operation. Grab samples can be collected with speed and the fluctuations In dustiness and the development of dust floods can be revealed in a^.way ' that is impossible with more cumbersome apparatus. South African experience involving the collection of thousands of samples has shown that the figure of merit given by the Koni meter is direotly related to the amount of phthisis - produc ing dust in the air. It is a valuable routine sampling in strument but because of its low and selective efficiency, the oounts reported are probably considerably below the true level and they are<not easily compared with data obtained in England, for example, with the Owens apparatus, or in the United States with the impinger." Experience has shown that oontrary to Drinker's statement, the Konimeter if .properly used, will give results that agree very well with those obtained by the use if.the Impinger. The U. S. Bureau of Mines Experiment Station at Pittsburgh in Sjame comparative studies with the Konimeter and the Impinger found that an average of five Konimeter determinations was within about two per oent. of one impinger determi nation. The reason for taking an average of individual results obtained by the Koni- \eter, for oamparison with those of the Impinger, is due to the fact that the* Kcad aster takes an instantaneous grab sample of small volumes and owing to the hetrogene- -*us nature of dust in air grab samples do not represent the average conditions. The impinger takes a continuous sample of rather large volumes and is thereby representa tive of the average. For these reasons, if it is desired to oompare Konimeter re sults with Impinger results it is neoessary to take several Konimeter samples during ^ e oourse of the Impinger sample, in order to obtain average conditions. We have no Correlating information of the Konimeter with the 20 to 30 micron porcelain filter against the standard impinger method. .. A Zeisc Konimeter, using a 20 to 30 mioron poroelain filter was used in Ving actual dust oounts in our various dust producing operations. The partiole sire and site classification was estimated rather than accurately measured and computed. Only ^rtioles ten microns or less in size were counted since it is generally agreed that Just particles larger than ten miorons in size are not particularly pathogenic. ] Other methods in common use are the Owens jet dust sampler ("Jet Dust Counting Jpparatus" by J.S.Owens, Jour. Ind.Hyg. ,Vol. 14,1932,P.522), whioh has recently been manufactured in this country and the photographic dust counter, developed by Ficklen EOtt. The Owens jet dust counter is used in this country to collect samples for iole size distribution determinations. It is used principally in Australia for rmlnation of number concentration of atmospheric dust of industrial hygienic im portance. , I The latest device for determining dust concentrations is the Bausch 4 Lamb Dugy Counter which was placed on the market a few months ago. This instrument con- lists of a dark-field microsoope magnifying 200X, and an impinging apparatus mounted jn a ccsnmon base. The base is a hollow chamber with the bottom hinged to provide easy acoess to the dark field condenser and a circular glass specimen slide. 3ymeans s?f a hand pump, which is part of the impinging device, a sample of air is drawn * i - 12- ougli * moistening ohamber which has at its lower^end a narrow slit. The dust is -P"x>sited through this slit on to the circular specimen slide in the form of a ribbon. JL^gjide can be rotated until the sample comes into'-proper position for viewing with fche sdorosoope, or a maximum of twelve samples oan b e ,collected on the slide and then The slides are qudokly removable and replaoble This dust counter is not i dfsig11^ for aoourate dust determination but rather as an inexpensive device for CJughly oheoking dust conditions. It has not been available long enough for a thorough aotual practioe. ;' jHggi' The principal objection to instruments like the Bausoh & Lamb Dust Counter and *\ Owens jet dust sampler for determining number concentration is that their dust collating efficiency decreases with an increase in the atmospheric dust concentra tion and the faot that they take grab samples. V> :C < Sinoe the major portion of dust present in industrial atmospheres is small : enough to gain entrance to the lungs, very little attention need be given to determina- " of the exact sites of partiles. f t r j :** ^r*. * V r. < ' V ,/ " i r- ' *! m* M <'*!& i s ? jo*-/ .^5SJ i \ *WHAl ARB PRINCIPAL DUST PRODUCING OPERATIONS? - In order to determine to extent if nrty workers in the production of petroleum products and associated Cities are xposed to the hasard of breathing dust, a survey of all dus produo * - era^j_ona was made at the various plants concerned, T,phve*s"eA o,,pe-ra-tmions, listed er of their apparent degree of dustiness, aret I - SAND - BLASTING : ' Due to the large amount of finely divided silloa dust produced by the impact ^ g r a i n s of sand on the surface of the object being cleaned, sand-blasting is Tost dangerous silicosis hazard encountered in our survey. Sand-blasting is j^ijTjather extensively at oil refineries for cleaning inside soaking drums, bubbly tar separators, run-down pans and storage tanks for metal inspection and to, * ait the aPPiica^irL f gunite lining as a means of preventing corrosion. Header Uies^or other similar parts, tubes in cracking coil fire boxes and return bend.B_ k, r^fgAad-bla.sted to permit a detailed and thorough examination for cracks and de Sand-blasting is'' also employed in the removal of corrosion from under floatinrroof tanks; for removing roughness or rust from steel shapes or rodsj for oleanU ^ b e l l caps, bubble plates, trays, and pipe prior to putting them back in service; lao'on the ends of tubeB preparatory to placing them for rolling; and for cleaning -^stings which are too large or fragile to withstand being tumbled. It has been '(#ji to a limited extent for cleaning buildings and rendering window glass opaque. I, The cracking coil tubeB, pipe, bell caps, trays, header-boxes and similar ob- cta'are usually sandblasted out-doors in the open air or in a more or less open (bed/ both locations being as far removed as feasible from any shops, process units Iriother working places. Coarse river sand is discharged through a one-half tothree- -uarter inch nozzle with compressed air under a pressure of 30 to 90 pounds per 'tquare inch. The men at the nozzles stand to the windward side of their work and Jear a "Healthguard" (Chicago Eye Shield Company) mask, a Sly Sand Blast Helmet or a resh Air Hose Mask covered with a canvas hood. The men at the Sand Blast Machines -tear "Bust Safe" goggles and a M.S.A. "Ccmfo" Respirator. The Mine Safety Appliances jeapany now has a sand-blast hood that is meeting with considerable approval by in dustry and also by the United States Navy Department. A blower is available for upplying air to these hoods that cleans the air. This same blower can be used in Ocnneotion with air-lino respirators. ... When sand-blasting is done inside of drums having more than one opening, such 'jt^soaking drums, an air siphon is plaoed in the lower manhole whioh draws out the just"and allows a continuous circulation of fresh air through the drum. In drums there thesiphon cannot be used, the air circulation ia poor and the men work in -hiits ranging from 30 minutes to an hour, depending on the size of the drum and the mount of air circulation inside. They also wear an approved sand-blast helmet. -J c` These sand-blasting jobs are not continuous routine operations but are per- joraed when necessary by men selected from the Common Labor gangs or the Mason's De partment. ?*?. oent. The work is rotated so that in most cases it ocoupieB less than twenty of the worker's time and there is an interval of IS to 20 days between and-blasting jobs. Consequently, on the average, no one man is exposed to more than combined total of 400 hours during the course of a year. In discussing rotation it men on sand-blasting jobs. Dr. Gehrmana, Medical Director of the du Pont Company 'Tote: "It must be borne in mind that silicosis is a cumulative disease and, therefore, the rotation of men in this type of work cannot be considered 1 -14- &s entirely preventive. Assuming that & man works in an atmosphere of sil- ioa dust for several months, during whichtime he is bound to absorb a cer- *taia amount of the dust rhieh produoes permanent damage in his lungs; he 1 s then removed and the possibilities are that the damage which is already done will he sufficient to continue-on and progress to the point where in hj_ater years he will develop symptoms, . :. "Therefore, if we take to rotating men in this type of work we are 'fi.oing the possibility of, in later years, developing a large number of oases of a moderate silicosis with some permanent disability. The only "aaf expedient which can be used is oomplete prevention and this can only 30 done by eliminating the dust." . , During our survey we found that men engaged in sand-blasting, that is ha-run i-ng 9-^QSxle or attending the sand-blast machine, were more or less properly protected actually doing the work but often times they removed their protective equip : before getting completely away from the working area. ____ X large amount of very small partioles is produced by sand-blasting. In an Ig^rsis of dust samples collected both outdoors and indoors during sand-blasting, ' he following distribution (Publio Health Bulletin No. 217 - p.52) on a sire fr*- ] basis was found* Sise Group in Microns Per Cent of Total 0. 00 -- 0.49................. 0. 50 - 0.99................. . . . . 1.4 19.7 'W 1.00 1.50 2.00 - 'Vf.___ 1.49........... ..... ............................. 1. 99................ * 2.49................ ... 34. 7 20.3 12.6 2.50 - 2.99................................................................ 5.2 3.00 -- 3. 50 4.00 4.50 5.00 5. 50 - 3.49........................................................ ... 399# # # * A A QS * # # # # # A QQ ' y1 o '.. *>.. C *Q - i v 'y M f - .-a # 0# t o o * e 00 - V # & 0 # * * #.#<# * ' . -V v t*. * . 2. 8 1.6 1.1 0.2 0.2 0.2 - - - While it has been estimated that free silioa dust partioles, _1 micron in diameter, ri'fquire 8_^ours-to..fall 5__ft. in still airj partioles .5 microns' _in diameter require '/[less than" I~Jiour_tO-fail the^same^dJLrtanoe. Considering this fact, it is apparent a -- that the dust harard from a particular operation may, even though carried, out for ^short periods, be acute throughout the working day. In view of the fact that the oco ndition of still air is rarely, if ever achieved, and that, dangerous partioles exist -in sises below one micron, it is evident that a hazard exists. ] Fortunately most of the outside sand-blasting is done in more or less isolated -- locations which makes it rather improbable that there will be any unsafe silica dust exposure to other workmen. However, should it become necessary for any work to be j -done in the vicinity of sand-blasting operations either on process units or the sand -blast sheds or yards, it should be remembered that there may be silica dust in the .-'air even though it can not be seen* Dust counts as high as 5,344,160 particles ten ^microns or less per cubic foot were found in samples taken about 50 feet "downwind" ^(wind blowing about 15 to 20 miles per hour) while sand-blasting cracking coil tubes; -- about 95% of these dust particles appeared angular crystalline under the Xonimeter J 'microscope and were about five microns or less in size. Samples taken about 100 feet -- "downwind" from sand-blasting operation had counts as high as 1,812,480 particles per 'oubie foot. 5 -15 vj irfc counts as high as 13,933,440 and as ^low as 453,120 partiles per cutio i?U5found in samples taken during the filling',of the Send Blast Machine feed The high counts were found when sand .was .shovelled into a small circular shaken ty hand, the lower counts, when the sand was simply shovelled in- hoPP^r* T*1 average dust produced hy filling or charging the Sand-Blasting was 4,950,316 particles, ten microns or.:less, per cubic foot. t. ' counts as high as 4,954,320 partiles^ ten microns or less, were found in taken inside a Sand-Blasting Room while cleaning castings. The average dust room during sand-blasting was 3,873,625 particles per cubio foot. About 80# Sjsa particles were angular crystalline three microns or less in sise and about ^ " 'leared rounded, quarts-like crystals about ten microns in size. There were a t-like soales over ten microns in sise and a very large number of minute dark o particles too small to be counted accurately. The dustiness of this operaIcould be greatly reduoed by the use of steel abrasives exclusively. All of the samples for dust counts referred to above were taken at face level ^vicinity of workmen. : ... .i. . * ; '** * ' ,000,000-dust'''particles per cubic foot is the tentative maximum allowable dust particles containing free silica of a sise less than 10 '.microns reeoo- j^jded'for sand-blasting, - n -FILTERING OPERATIONS i* =} mi jr The process of filtering is extensively used in the refining of petroleum to improve the oolor stability and to remove impurities freo motor lubriparaffine waxes. The three materials aqet commonly used for this purpose `j&Filter Clay or Pullers Earth, Contact Clay and Bone Black. Considerable dust is `prt&bed by the handling, oharging and reoraditioning of these materials. J filter clay or fullers earth 1 `Wbab is Filter Clay or Fullers Earth? Filter clay oanncrt be identified from chemical composition but consists of silica, alumina, iron and alkaline earths in 3 rarying percentages. The distinguishing properties are laok of plasticity and the power to remove oolor from oils. There are numerous deposits of this clay and other, filtering earths in the United States the oldest and among the most extensive are > > those found close to the Florida-Georgia line. One of these, at Attapulgus, Georgia, n rjppliss a major portion of the olay vised by the affiliated Standard Oil Company (Jew Jersey) organisations. At the mine this material oontains on an average approxl> mtely 32# silica and 45# moisture. The average composition after being prooessed and prepared for shipment is approximately . Si02..................... ....y 67*46 per cent AlaOj....................... . ;:10.08 . " n Fe^Oj.^ 2. 4 9 " ** 1 MgO. .................... ....-^4.09 " Combined Moisture.... . ;C* 5. 61 n " Free Moisture. ........... ; 6.28 " " The comparatively low dust oounts1found even in plaoes where there was cleaning and sweeping is no doubt due to the fact that this filter clay is of a rather coarse na ture and without appreciable amount of fines. There appears to be a wide variation in the composition and free silica con tent of filter clays used in European refineries. nTerranan a German Filter clay used in Poland shows: -16- Loss in calcination 05 per cent Free Silica (Si02)........ V - 4 -8*27 AI2O3 and F203.......... * ^? -M\>^?i & 'm i 1 Ihe filter clay used in Roumania is repor$e4.'.;as'' having 60.4 per cent, free ^ or 75.z% total silicates. "Granosil" olayjused in Belgium contains a. total. ^ntagfl of 73-1/2 per oent. of silicates expressed-as Si02. The percentage of free ^liea as riot determined. , Sow is Filter Clay Mined and Prepared? - The^deposit varies from 2 to 12 feet thickness, probably averaging about 7 feet.. ''There is an overburden of about 35 which is removed by an. eleotrioally operated*drag line or a .steam shovel. The loaded into small cars, transported to the wet clay shed where it is dumped # ^ H o ' t h e drying floor and dried for three days. It is then picked up by orange peel ^ ^ k e t s , loaded into portable distributors and delivered to belt conveyors which dis- the earth into roller crushers where it is reduced to sires up to a maximum of inches. From these crushers the clay goes to secondary crushers where it is re- S'^Sied to a maximum of one inch. Since the clay is more or less damp very little I^dSst is produced. The clay is then transferred ,to tandem oil-fired rotary dryers, F 50 to 60 feet long and* six to seven feet in diameter. In the 20 minutes required **for the clay to pass through the dryers the volatile and moisture content is reduced ] M t o 50 per oent. to a maximum of 15 per cent. The average dust ten microns or i^less ia sire in samples taken at various points around the dryers and conveyors was 31*564,969 partioles per cubic foot. This rather low. dust count is the result of the ^installation of hoods with ducts to exhaust fans-placed over the discharge points to ithe' conveyors or elevators. About 85# of these dust partioles were angular crystal- lline in appearance under the Xonimeter microscope and about five microns or less in y 5slxi' about 15# were over ten microns in sire. The_ larger particles had rough edges appeared to contain several small air bubbles." The clay is removed from the ^dryers to hot rock cooling tanks, then to a vibrating screen. The overs ire is next ^pulverized in a roller mill and the product conveyed to a sifter. An exhaust system :rfor" the mills and elevators has been installed. This process may be repeated until ^the desired sire material has been obtained and graded to standard mesh sires, the rVetter known of whioh are 15-30, 30-60, 60-90, and the 200 mesh. The 60-90 grade is ] ^probably the most commonly used in the petroleum industry when decoloring by percolaition, and the 200 when contacting. However, the 30-60 is preferred by most ,of our ''refining units in the United States. The sire selected is apparently determined .^largely by the type of returning equipment. . - s S6een tests are made hourly to insure that the sires are within the speoifi- ^eations. Here are two typical screen analyses , ' ' ' 30 - 60 GRADE FILTBfcsCUr-.. ^ Mesh Per, Cents^^J Over 30 .. 30 - 40. 40 - 60. 60 - 82. Thru 82 .. -W- - 1 Total 100.0 IP1. a >,:.. v - .rv ' : . y " '* X" ^ -17- FIIIE5 (100 - u p ) GRADE FILTER CLAY Mesh Per Cent. Over 9 7 ................... ; . 97 - 157.................. ..'..... 157 - 200.................. ....... Thru 200........................... 0. 6 22.7 8. 0 63. 7 ' Total 10 0 .0 There is very little dust produced by the sifting operation. All of the con- ^tions are designed to be dust tight but there is some leakage. Samples of air x ^ e n at various points around the sifters while in operation had an average of ^ ^208,960 dust particles less than ten microns per cubic foot. About 85% of these |5ujgt' particles were slightly angular crystalline in appearance and five microns or in size; about 15% were slightly rounded semi-opaque ten microns or over in size, larger particles had small cracks or fissures and several small air bubbles. lien spend about two hours a day deeming, repairing or replacing silk screens IT^jT-the sifters. Samples taken during this operation contained an average of J^2'039,040 dust particles less than ten microns per cubic foot. About 97% of these st particles were angular crystalline in appearance and five microns or less in ?'sisej about 5% were opaque over five microns in size. yr After being sifted and graded the clay is ready for shipment. The 30-60 mesh *pfaae is placed in burlap bags holding 128 pounds and loaded into railroad box cars; ^about 400 bags to a car on an average. Dust counts of samples taken during the fill ing-of the bags with the 30-60 mesh grade show that there sire from 7,589,760 to ^"g'968,640 dust particles less than ten microns per cubic foot which indicates that f a 1 1 .men engaged in bagging and handling bags in this area should wear approved respiYrators such as the "M. S.A. Comfo". About 80% of the dust particles in samples taken T during the filling and handling of the bags appear slightly angular crystalline under r the microscope and are five microns or less in size; 20% are rounded crystalline, ten r microns or over in size. Bulk Loading of railroad box cars with the 30-60 mesh grade produces clouds of 'dust, but a major portion of this dust is apparently larger than 30 microns in size > /;u sample taken during this bulk loading had an average of only 6,853,440 particles, ..ten microns or less in size per cubic foot. The Fines (100-up) grade is put into 128-pound cotton bags. Dust counts in samples taken during this operation showed that there were from 4,644,480 to 14,216,640 dust particles less than ten microns per cubic foot in the air being breathed by the fillers, weighers, sewers and truckers. About 80% of these particles were rounded, semi-opaque crystalline in appearance under the Konimeter microscope and five microns or less in size; 20% were semi-opaque crystalline from about seven to fifteen microns in size. There were also a large number of very small particles about one micron or -less in size. How is Filter Clay Used? - Upon arrival at the refinery, the bags of clay are removed from the box cars by a crew of men usually from the General Labor Department; the job being rotated so that the same men do not do this particular operation more than perhaps twelve hours twice a year on an average. Goggles and "M.S.A. Comf0" respirators are generally provided. The clay is either trucked or dragged to an elevator or conveyor hopper and dumped and the bags are piled for storage. At points where the clay is received in bulk, it is unloaded by a large wooden scoop pulled by a. motor driven drag-line. Unloading, handling, and dumping the clay is one of the -18- ^j.est parts of the filtering operation. The amount of dust produced is of course ^'dPen<^ent n ^W wor^ ^ one' ventilation provided, and the care used by th doing the job. Here are some average dust counts of particles less than ten. mi,jaen ^j-ons in samples taken during the unloading of bags of 30-60 mesh Attapulgus clay Particles Per Cubic Foot Qaloading and dumping bags (128 lbs. ) into Hopper at a '' Southern Refinery....................... fl)umping clay from Bags into Elevator Hopper at a ' Northern Refinery............ ^Handling bags from Storage and Dumping into Elevator Hopper at another Northern Refinery............ "inside Box Car During Unloading.................................... Outside" " " " .......... ....................... In Filter House Passageway being used to Truck Clay to Elevator hopper......................... rAverage Dust Produced while sweeping up inside car after '* unloading............................... 5,403,456 2,237,280 755,150 1,110,144 372,924 339,840 651,360 Apparently unloading clay in the bulk is less dusty than handling and dumping Bs''of the clay in bags. Samples taken during the unloading of bulk c.lay gave these average counts of dust under ten microns in sizer _ inside car during unloading..................... 962,880 particles per cubic foot IS*Outside " " " ..................... 623,040 " " " " ^ There is of. course more dust produced in the vicinity of bulk unloading than is proIf'dueed when handling and dumping clay in bags. After dumping, the new clay is taken by elevators and conveyors to storage It bins which hold about 20 tons each. This is also a dusty operation due to the failur ^io cover the storage bins or to place hoods over the junction points of elevators and ..c belt conveyors. Samples taken during the filling of storage bins with new clay had 1 these average dust counts of particles less than 10 microns in sizer Dust over Bins around elevators and conveyors during i 33^' filling at a Northern Refinery....... j p * ' n tt It " & Conveyors while filling at another Northern. Refinery................................ " & Conveyors while filling at a '".vi'* . Southern Refinery................................. n Face Level on Walkway over Storage Bins Northern Refinery while Filling Bin........................ Dust Counts as high as 8,609,280 particles per cubic foot were found in samples taken ^near the discharge of one belt conveyor into the top of a storage bin. About 90$ of ^ these dust particles appeared angular crystalline under the Konimeter microscope and ;/were five microns or less in size; about 10$ were black, opaque, many scale-like in 'appearance and ten microns or over in size, "BURNING" CLAY - From the storage bins the clay is conducted by chutes and/or conveyors and elevators to gas or oil fired Wedge Burners or Rotary Burners or Kilns in which it is "burned" or roasted, and then discharged into rotary coolers where it is cooled. Where all openings, chutes and elevator outlets as well as the ends of rotary coolers are properly enclosed and an exhaust duct is placed over the burner, very little dust (an average of only 804,160 particles, ten microns or less in size -19- ___ ybic foot) is produced and no respiratory protection is necessary. Three tyrioes or kilns are used to recondition filter clay. Average dust counts of lei taken during the operation of these burners give a comparison of the amount ^du-st (particles ten microns or less per cubic foot) produced by each: NjypA of Furnace Feeding About Furnace Coolers Total General Average___ `'ff-rman-Frasoh Oil or Gas Fired..... p Wedge Gas Fired..... gnotary " ..... 2 , 6 2 4 , 3 2 0 ____ 5 , 3 9 9 , 6 8 0 ___ 2 , 0 6 7 , 3 6 0 ___ 3,700,480., 1,522,459. 1,070,046. 2 , 7 3 2 , 8 8 0 ........... 2 , 1 0 8 , 5 9 0 .......... 3 , 1 1 5 , 2 0 0 .......... 2,990,542 2,395,971 1,818,206 The present practice of using a compressed air hose to clean up the clay on ^Tr^Various floods of the Furnace House at one of the Refineries is particularly ob- ieotionable due to the excessive dust (12,687,360 particles ten microns or less per eubi which is stirred up. I ** ujggjv- About 90^ .of the dust particles in samples taken during the burning of filter olay were angular transparent crystalline in appearance and five microns or less in si*J were round opaque, ten microns or over and 5% were rounded semi-opaque, ten microns or over in sire. jgi:- Exposure to dust produced by burning or reoonditioning clay is rather limited. Usually there is one fireman for each shift of eight hours, three shifts per 24 hours ajjd a porter for the day shift only. Since one of the porter's main jobs is to .*oleam-up? he is exposed more continuously to dust than are the firemen. CHARGING FILTERS - The cooled, burned clay (30-60 grade) is conveyed to the filters by means of elevators and belt conveyors and charged through chutes from the conveyor belt tripper at a rate of from one and a quarter to eight tons per hour, jhese vessels hold from seven to fifty tons each. The amount of dust produced during the charging operation depends upon the grade of clay being handled, the'rate of charging, the position of the clay on the conveyor belt, the condition of the convey or belt, tripper and charging chute; also whether the top manhole of the filter is loft open during the filling. A general average of 54 dust counts made of samples taken during the charging of filters at all of our plants using 30-60 mesh Attapulgps Filter Clay was 3,717,884^particles ten microns or-less in size per cubic foot. The iaount*of dust produced by the charging operation varies considerably at the various plants as is shown by these averages? pa/ ' * Refinery rrtfc. ' ' Baton Rouge '""ST* Bayway Bayonne Eagle Works Charging Rate Particles oer cubic foot 8 1 -1 /4 3 -1 /2 6 tons per hour --.... tt tl tt tf Tt tl tt 4,271,413 2,435,520 2,242,944 1,042,976 It 8 the general belief that the more times a clay has been used and recondit the less dust is produced during its handling. Our study does not confirm this be lief as applicable to dust produced while charging filters, Averages of dust counts in samples taken during this operation were: 77JTL 1 Clay...... .......... # 3 If # 10 " 2,242,944 particles per cubic foot 4.604.832 3.896.832 -20- p y According to an analysis of particle size made by the Bayonne Laboratory of a afflole of (30-60 grade Attapulgus Clay) No. 1 , -No. 3, and No.8 Wedge clays, the f^lowing is the size classification or distribution: Raw Clay #1 Clay ' #3 Clay # 8 Clay Coarser than 100 mesh 98. 5%... . 99.4#... 98. 7/^o. . 98. 3# Diameter of Particles Raw Clay #3 Clay #8 Clay jfl1 1 1 meter8 Microns Per Cent Per Cent Per Cent to . 074 T . o n " .044 f. 044 " .035 035 g 025 " .025 " .015 f.015 " .005 *. 005 " .001 149 to 74 74 tl 44 44 II 35 35 It 25 25 It 15 ih It 5 5 If 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# of the dust particles in samples taken during the charging of #3 clay were slightly angular in appearance and five microns or less in size; 15# were 'ounded semi-opaque, ten microns or over in size. About 75# of the particles in samples taken during the charging of #10 clay were slightly angular crystalline, fire microns or less in size; about 20# were over ten microns in size and were semi-opaque about 5# were round semi-opaque between five and ten microns in size. All of the larger particles appear to contain small bubbles. There are numerous small black specks about one^-quarter micron in size. Charging of filters is usually done by one man per shift for each filter , ahouse. There are three shifts a day. These men have an average service of about 20 ^years and work eight hours a shift, nine shifts out of fourteen. Ventilation is provided in the newer filter houses by eighteen-inch roof vea- jLtilators extending about twelve inches above the roof and also by windows which oc- pupy about 80# of the wall space in front of the top .of the filters. 1 ' DUMPING FILTEPJS - After the filters are charged with clay they are plated up -jfand th oil is allowed to percolate through the clay for several hours, the length of ] -intime depending upon the nature of /the oil run and the "yield" of the clay; The oil *-J J&is all drained off and the clay is then washed with naphtha or "Varsol" and steamed jfto remove all trace of the naphtha. After this the filter is dumped on to a canvas .3 .belt conveyor and the clay returned to the kiln for burning or reconditioning. Filter -V clay is used as many as fourteen times before it is finally discarded. In order to Z determine what effect the reconditioning of filter clay had on its free silica con J s t a n t samples were analyzed ^dustrial Hygiene with this by the New result: York State Department of Labor, Division of In- Times Burned % Free Silica Raw Clay............... Once................... Three.................. Eight.................. 6. 30 8.50 9. 20 9. 30 1 Considerable steam is usually given off during the dumping which probably * -21- ^.Ins the smaller dust count (a general average of only 2,518,781 particles ten or less in sire per cubic foot) than would be expected. The dustiest part of filter dumping operation is sweeping up the floor under the filters after dumpis completed. Samples taken during this sweeping or cleaning up had as high as 538,880 particles per cubic foot, although the general average of samples taken dumping, at the. various refineries was 2,514,816 particles per cubic foot. About of these dust particles are slightly angular crystalline in appearance under the ironmeter microscope and are above five microns or less in size; about 5% are rounded p^ui-opaque over five microns in size. Occasionally the clay doesn*t "flow" when the filter is opened end must be started "flowing" by means of an iron bar. This action ^usea some dust (2,888,640 particles per cubic foot) but not as much as pounding the rbottoffl and lower sides with a sledge (4,248,000 particles per cubic foot) as is some- dae- After the clay has run out, the inside of the filter is swept out with a ire* which produces a little dust (an average of 792,960 particles per cubic foot). ^Ihe filter is then plated up and is ready for recharging. The work of dumping filters is done by one m an per 3hift, for each filter bouse. Theso m e n have an average service of about ten years and work eight hours a | ^shift, nine shifts out of fourteen. They are exposed to dust less than 60 per cent. *`"of their working time. - Spent clay is used to a limited extent for packing around valves and. fire hy drants to prevent freezing; also for certain other small absorbing job such, as on the warehouse floors of some of the larger bulk sales plants where lubricating oils are earns --frynwferred from barrels or drums to smaller containers, or loaded into five gallon from bulk. Most of the spent clay is disposed of, however, by dumping it on nearby Company property and, to a lesser extent on railroad property near river banks. j Jjgi- . f:" Composition of Filter House Air Borne Dust: Samples of dust from Attapulgus lay, which had settled on the tops of elevator housings and on girders over the storage bins in filter houses, were submitted to the United States Bureau of Mines Ex- 1 pfcriment Station for petrographic examination. Ordinarily positive results are not I obtained in petrographic tests for the identification of minerals in atmospheric dust. ` However, the samples submitted were coarse enough to give results in most cases. In studying the results of the petrographic examinations it should be borne in that 1 the samples submitted were settled dust, and that they are not representative of the 3-i composition of the dust that would be breathed generally owing to the differential settling rates and the ease with which the various mineral constituents can be crush-, ed to a powder. * "Montmorillonite" ((Mg, Ca) 0.A12 03. 5Si 02. nH20 -- n5to8) is the miner ial that is characteristic of many types of fullers earth, Not all of the less important minerals found were fully identified. Clay dust from top shell of elevator - Top #2, Herman-Frasch Furnace. J Quartz - 10/ Montmorillonite - 80; Caleite, Mierocline and Unidentified - 10% J Dust from accumulation on girder ever clay storage bins - #4 Filter House. Quartz - 10% ` Montmorillonite - 70% Possibly other clay minerals present, opaque - 20% Dust from accumulation on eirder ever clay storage bins - =1 Filter House. Quartz - Over 1% Opaque - 40? Montmorillonite - 55% Unidentified - 5% -22- J S-B- ff if fct t tt tt tr m U t t r a a a u Control of Filter Clay Dustt Dust in a filter plants results principally from eration" of the clay handling machinery. The condition is aggravated by the . S' ent practice at some refineries by using an air hose to blow accumulated dust and l^Tled ciay from equipment, walls and floors. Handling a fine light dust producing such as filter clay, in a system which includes open belt conveyors is in^"'ently a -dusty operation. (12,687,360 particles, ten microns or less in size, per foot). It is difficult to prevent some dust frcxa being generated at unloading jSJrgft'g where the clay falls into chutes or bins, but it can and should be controlled of hoods, enclosures, and adequate exhaust systems with effective dust collec- ____ There will always be an irreducible minimum of spillage and .dust settlement Srver dusty material is handled in systems such as exist in most refinery filter SusVs* This is an economic waste and increases the difficulty of the dust control pfobl311* Unless the present practice of cleaning dust spillage by blowing with cam- ed air is changed, the necessary periodic cleaning will continue to be a very ^fcy and unhealthful operation even though all precautions have been taken to pre- jTflofc- the escape of dust from clay handling equipment. A modern industrial vacuum 0leaniug system would do the job efficiently, without creating any dust. The principal source of dust in filter buildings is the belt conveyor which is fdually located at the top of the building. Gusts of wind from the monitor blow the lay end dust from the belt. A certain amount of dust is also generated by clay fall ing, into the tripper chute (6,060,480 particles per cubic foot) and discharging from 23the"tripper chute into the chute leading to the various filters (7,306,560 particles gj-pgf^oubio foot). This could be considerably reduced by inserting canvas or sheet iron connections between the ends of the tripper chutes and the chutes to the filters, --Tand by using a properly designed belt tripper on the conveyer belt. ~ ' Bins for the storage of filter clay should be closed with steel decks having the smallest possible openings in the form of ohutes to reoeive clay from the canvey- ]ers7:-' If oare were greatly reduced. taken not to overflow the bins, the dust and spillage could be t J shl-,.' For complete control of dust, an exhaust system equipped with dust collector, _| fttn,` ducts and hoods should be installed to remove dust from the points of origin, such as, all unloading points (except movable trippers) of each belt conveyer in the 3building, new clay bins and burned clay bins. One estimate which has been prepared for such a n _installation calls for an exhaust system with a capacity of approximately 15,000 cubic feet of dust laden air per minute, and is based on maintaining an inward flow of air at openings into hoods and bins at a recommended velocity of 200 feet or more per minute. ' In considering dust collectors, it should be borne in mind that the J cyclone type will not remove the fine dust particles (ten microns or less in size) which are most injurious to health, and that the cloth bag type filter has been proven n to bo more successful in removing these fine particles. J 21- Under existing conditions at most plants it is almost impossible to keep the J plants clean, regardless of how carefully the equipment is operated. However, the in stallation of a vacuum system and adequate dust collectors should encourage operators td exercise more care in the operation of equipment and thus cut down the amount of dust and spillage. B. - CONTACT CLAY: V Most contact clays, particularly in the United States, are acid treated "Ben tonite". Bentonite is a non-refractory clay, a double silicate of iron and aluminum, derived from the shale of the Fort Benton formation in the upper Missouri valley. -23- There appears to be a wide variation in the composition and free silica con- __ ^of Amricai1 Eviropean contact or activated clays, "Filtrol" an extensively ft^^;^3nerioan contact clay is reported to contain about 57$ free .silica (silica which '"K2??niolub3.e in concentrated hydrochloric acid). "Milwhite", another extensively |tlv^n^jnerioan contact clay, contains 65$ free silica. The contact clays listed are y*f2To most extensively used in Europe: Insoluble in Concentrated HCL Insoluble in Concentrated HCL and 5$ HA? CO3. "Ivry" Clay (French).... ."Terrana Extra" (German). ,,"Clarit" (Italian)...... 75. 0$. 64. 4$. 49. 5$. 64. 6$ 27. 2$ 50. 6$ "Tonsil AC", another French contact clay, has 61.75$ free silica, *'The main constituents of "Petrisil", a German contact clay, are: Total Silica............... Lim'd (CaO)................. Aluminum and Iron Oxides.... Loss on ignition (Water)..., 51. 57$ 0.63$ 18. 83$ 23.62$ The balance probably consists of potassirn and sodium oxides. m . The following is the result of a petrographic examination , of "Petrisil" which was made at the United States Bureau of Mines experiment station: Quartz..................... 5$ . Montmorillonite............ 90$ Unidentified Minerals..... . 5 $ v : The use of contact clay for improving the oolor of lubricating oil3 i3 a re'oent development. At present the price of contact clay is so low that it is used only onoe and then discarded. ' jgfcl Although there are many contact clays on the market, a large percentage of that used by the Standard group is known as "Filtrol", consequently this was included in ^ our dust studies. . ] What is "Filtrol" and How is it Produoed? "Filtrol" is a pulverized acid treat ed Bentonite, used as a deodorizer, absorbent and deodorizer in the refining and preparation of both organic and inorganic oils. It comes iVom "open cut" mines in J Mississippi and California, and occurs in beds about two and one-half feet thick under an over-burden of some eighteen to twenty-five feet. There has been same doubt as to its origin, but it is now believed to have been volcanic dust transported by the air and deposited under the waters of either a lake or a sea. Raw Bentonite is mined and loaded onto trucks with steam shovels, and then taken to the preparation plant. A tractor scoop lifts the raw material from the storage shed floor and places it in a hopper out of which it is fed into an elevator by means of a steel pan feed er. The elevator discharges into a crusher which breaks the material down sufficient ly to enable it to pass through a screen (three meshes to an inch) onto a belt con veyer which takes it to a pre-mixer where it is mixed with water to form a "slurry". This slurrv is oassed into larre wooden tanks and treated with dilute sulphuric acid -24- with air and steam. It is then dumped into thiokeners, washed, and deliverOliver filter. From there it goes in turn to a pug mill, drying tower, cage mill and classifier. The finished product is placed in a bin where ii is fwjnto fifty pound Bates Valve paper bags by means of a Bates Bag Packer. It is in.. railroad box cars, each having a oap&city of from 1600 to 2000 bags, The ^ g r a d e s of "Filtrol" in greatest demand aret GRADE oent. thru >00 mesh) 85 - 88 75 - 88 90 * 93 Per cent, of Total Production 80 16 5 Coarser Than 200 Mesh 14.0# 23.0# 8.0# 200 - 325 Mesh 16.0# s 24. 0# 23. 0# Finer Than 325 Mesh 70. 0# 53.0# 69.0# The only real dust producing operations in the production of Filtrol are the jjiing, staoking and handling of the fifty pound bags. Samples of dust taken during ese operations, revealed the followingr Operation Particles per cu ft. . Average dust filling bags with 85-88 grade " tt packing roam while filling bags " n produced in handling of filled bags 10,416,096 9,572,180 5,845,248 An exhaust system has been installed to reduce and control the dust produced during the packing of Filtrol. This consists of a metal hood above the filling tubes liTfront of the machine, with a basin below. A seven-inoh duct leads from the basin I a six-inch duct to a canopy in back of the paoker, both connecting with a teniaoh main duct *diioh runs to a Sturtevant Fan (1750 R.P.M. ) designed to handle 1,620 oubio feet of air per minute against four-inoh water static pressure. A cyclone dust oolieotor removes the larger particles from the air before delivering it to a tubular eioth dust collector. About sixty per cent, of the dust particles of samples taken during the fil ling operation are slightly angular crystalline in ap'pearanoe under the Konimeter mi ld orpseope, Cdd are about two microns or less in sirej approximately twenty per cent. Yppear.to.be rounded crystalline, glass-like, but with rather smooth edges, and over ll _ta miorons in sise. There are. a large, number of very small gray particles (about rj .twenty per cent. ) too minute and too numerous to count accurately. What-is the Chemical Composition of "Filtrol"7 Below is the result of an an\&lysis by a oommercial chemical laboratory in Los Angeles, California, of a sample j)f Filtrol from the Jackscn (Mississippi) plant? Per Cent, Silica (Si02).......................... Alumina (A1203 )...... Ferric Oxide (Fe2 0 3)................... Titanium Oxide (Ti02).............. .. Calcium Oxide (CaO)............. Magnesium Oxide (MgO).............. Manganese Dioxide(Mn02)................ Carbon Dioxide (CO2 )................... Potassium Oxide (K2O).................. 56. 90 13. 97 1.44 0.10 2.82 3.55 0.03 ia " -25- Per Cent, Sodium Oxide (Na20).................... 0. 04 Chlorine (Cl)....................... ... Phosphoric Anhydride (P2O5 )..... ....... Sulphuric Anhydride (SO3 )............. . 0.63 Total ignition loss.................... 20. 00 * Free Moisture.......................... 12.23 "It is customary to separately report materials such as Silica (Si02) and Alumina (AI2O3 ) in ultimate analysis although the elements are known to be in combination with one smother. It is difficult to get an analysis of free Silica, and since the quantity contained in Filtrol would be -very small, we hare not attempted to hare this par ticular analysis made." The following is the result of an analysis of "Super-Filtrol" which was made 'France: ; '* Per Cent. Moisture at 120 degrees C ............. Loss on ignition....................... Insoluble in concentrated H C L ......... (Total Silica and unattacked crystals) Insoluble in HCL and in a 5% Na2C03 solution. (Siler, quartz and unattacked crystals) 16. 5 33. 5 55.0 15 0 A microscopic examination shows a few particles with "acute angles". An examination made by the United States Bureau of Mines Experiment Station in ""Pittsburgh, Pennsylvania showed that Filtrol contains more than 1% quartz, 95?? Montmorillonite ((Mg, Ca) 0.Al203-5Si02-xiH20-- n*5 to 8 ) and 5% unidentified minerals. ?Arsimilar examination of Attapulgus Fines (200 mesh) showed 5% quartz and 95?? Mont I morillonite. . Jjfe How is Contact Clay Used? The clay is mixed with oil, agitated and heated, and k thither allowed to settle or run through a filter press.' ~It is then discarded. The rclay is eitlfer dumped directly into the oil or placed in a hopper from which it flows ^into inductors or mixing chambers where it is mixed with the oil and then pumped to a : filter tank. The only dusty operations are the unloading of the material and dumping fit into the hoppers or mixing chambers. The higher dust counts with the contact clay -fas compared to filter clay is probably due to the fact that it is a finer material, 'or at least disintegrates more easily than the filter clays studied. _J?- Samples taken during the damping of Filtrol and Attapulgus Fines into a reac t i o n chamber gave the following dust counts. Operation Particles per cu. ft. Average dust produced while dumping 50 pound bags of "Filtrol"........................ 6,768,480 Average dust produced while dumping 100 pound V- bags of "Attapulgus Fines"................ 9,260,640 -26- Konimeter Microscope the particles were rounded in appearance. The "AttaFines" appeared more crystalline and angular, and had a greater proportion of es five microns or less in size than did the "Filtrol". The counts indicate m0re dust results from dumping Attapulgus Fines than from dumping Filtrol acti- ted clay. Dumping fifty pound bags of "Milwhite" (90% through 200 mesh), a Texas contact into the feed hoppers to the inductors or mixing chambers is an exceedingly [clay iity operation. Samples taken during this operation had as high as 14,046,720 par 'oles ten microns or less in size per cubic foot. Samples taken in the middle of -roam just after thirty bags had been dumped into the hopper had 55,847,040 par oles per cubic foot. Under the Konimeter Microscope, about 90% of these particles eared slightly crystalline, and were five microns or less in size; 10% were round, [*PP [etui-opaque, ten to twenty microns in size. There were also a few scale like parlolesm Fourteen men with an average service credit of six years are involved in this Operation. Three men are exposed to the dust during six hours of each eight hour Hl'shift for nine of the fourteen shifts during the 85% of the time the filtering plant "'is'in operation, ^hey wear M.S. A. "Comfo" respirators. j After extensive study and investigation the local management has made arrangeif^nents to receive the -clay in tank cars similar to those manufactured by the General 3lAmerican Tank Car Company. These cars are self-unloading and will discharge into an enclosed hopper. The clay will then be transported to storage bins by means of a screw conveyor completely enclosed in ten-inch tubing. It will be withdrawn from the bottom of the bins, passing through weighing scales, into the inductors where it will j>e mixed with the oil. This will provide a completely closed system and should liminate all air contamination. 1 fcg- BONE BLACK OR CHARRED BONE Refined wax is filtered through bone black or charred bone to improve its J f^olor. . This material is obtained frcm various meat packing firms in finely woven cof- vffee bags that hold about 150 pounds each. An open belt conveyer and elevator carry -.S'the bone direotly from the reactivating furnace to the covered filter charging hopper. 3 >=_Metal ohutes lead directly from this hopper into filters which hold about 3,000 ^pounds of bone black. Upon completion of filtration the bone is washed with "Varsol", steamed..for about 24 hours, washed with hot water,' steamed for two hours more, and* hsthen dumped upon belt conveyers which carry it to the reactivating furnace which is ^Vgas fired. The bone goes through the furnace at a temperature of about 1100 degrees 'Fahrenheit and at the rate of about 250 pounds per hour. Bone black can. be used over :-*=and over again. Three men one on each shift, with an average service credit of ^fifteen years, are engaged in this operation. Their period of exposure to dust is % about one hour per shift. The greatest amount of dust produced results from the open "^conveyers, particularly in dumping the material from the furnace onto the conveyer ybelt. Samples taken during this operation had as high as 11,044,800- particles of ten J S microns or less in size per cubic foot. Considerable dust (14,273,280 particles per ? cubio foot) also arises from the open hatch of the filter charging hopper during ^filling. An eight-inch motor driven exhaust fan has been installed to suck back the a dust from where the elevator buckets dump the reactivated bone into the chute to the i* charging hopper. The dust loss from this filtering operation is estimated to be about 1500 pounds per month. T Under the Konimeter Microscope about 65% of the dust particles of samples taken - during the reactivation of bone black appear to be black, opaque, scot-like, and are five microns or less in size; 5% are rounded, semi-opacue, ten microns,or more in size, j The angular crystalline and light- grey particles which constitute about Z0% are probably Ill -INSULATING O P E R ATIONS Insulation plays an important part in the processing of petroleum products, --two types i*1s u i t i n g material most frequently used are "Sponge Felt" (asbes- ith ground sponge to give dead air space and thus increase the effectiveness insulation) and a mixture of 85# magnesia and 15# asbestos. Rock wool is !^.0 a. considerably lesser degree. In the ordinary camrr.ercial form, Rock Wool, J ed at our refineries, does not present a dust hazard. It is also used for ins' "e insulation, and is available in small nodule form which can be blown into -3*- "85# magnesia" is a mixture of magnesia and granulated asbestos and pressed "o'-blocks of various sizes and shapes (usually 16" x 18" x l-l/2"). The most dust from dismantling old insulation and grinding scrap material for use as a plas- Tg?cir "ganister". The average service of men engaged in insulating operations is fifteen years. Most of these men have been transferred from the Common Labor ^rtment. They work nine out of fourteen eight-hour shifts, in gangs of from two men, and are actually exposed to dust for less then sixty per cent, of their J^rkiug time. Goggles are sometimes provided, and occasionally MSA "Camfo" Respira- but this equipment is not used as muoh as it should be. Generally speaking, '^'ut 85% of their work is with sponge felt and 15# with 85# magnesia insulation. of the larger southern refineries about 300,000 square fee of sponge felt and {0^000 square feet of 85# magnesia are handled a year. What Physiological Reactions are Provoked by Insulating Materials? According $rtm Leroy U. Gardner (Jourru Indust. Hyg. Mar. 1937,Yol. 19, No. 3, P. 121) asbestos dust *ith its fibrous particles does not seem to be readily handled by the protective aaehanism of the lungs. Quoting from his article: "They are not removed to the lymphoid tissue but remain in contact with the delicate walls of the air spaces. They become surrounded by an iron-containing ooating that fractures and gives rise to the pecu liar structures known as 'asbestosis bodies'. The fibers are irri tating, perhaps because of their fora:, and they excite a fibrosis which begins about the terminal bronchioles and spreads to form dif fuse patches in the parenchyma. Often the distribution is sub-pleural. In the presence of infection, the reaction to asbestos dust is much more- severe than that caused by the dust alone." * _ There is nothing in the pertinent literature, nor does the Bureau of Mines know of any evidence, which would demonstrate magnesite (a natural magnesium carbon ate) to be harmful. It would fall in the class of "nuisance dusts" such as gypsum. Vhile many of the so-called "nuisance dusts" have never been found to be harmful, it isvthe opinion of most investigators in the field of industrial hygiene that no work er should be exposed to any dust in a concentration exceeding 75 or 100 millions af particles per cubic foot of air. B - What are the Principal Insulating Operations and How Much Dust is Produced Purine Such Operati ons ? There is, of course, a wide variation in the amount of insu lation work and the amount of dust produced. A few examples, however, will give a good general idea: INSULATING 12" STEAM LINES: 6" x 18" x l-l/2" blocks of 85# mag nesia are tied on the steam line with 14-gauge galvanized wire and covered with roofing paper to make it waterproof. Often times this work is performed on scaffolds twelve to fifteen feet above the ground, with men lying on their backs under the line part of the time.  ff 0 U It U n u u B r s r s b i r e u u u u -28- Considerable dust (as "high as 18,124,800 p.rticles of less than ten microns per cubic foot) results from tapping the blooks into place, 'samples taken during the entire operation had an average concentra tion of 6,881,760 particles per cubic foot. About 90$ of these dust particles were slightly angular, crystalline in appearance and above five microns or less- in size (as seen under the Konimeter Microscope)) were rounded opaque, ten microns or more in size; and 5$ were opaque scale-like, five microns or more in size. Samples taken while applying asbestos sponge felt to a 1 2 " steam line had a dust concentration as high as 23,788,800 particles of ten microns or less in size per cubic foot. The average was 12,574,080 particles per cubic foot. These dxist concentrations are considered too high for work ing without adequate protection. INSULATING A 750-POUND CRACKING COIL ACCUMULATOR; 6" x 36" blocks of Johns-Manville "Fire Felt" are first applied and plastered with extra AA Rubberoid Asbestos Cement and waterproofed with JohnsManville "Insulkote". The dustiness of handling these materials has been considerably reduoed since the manufacturers began shipping the "Fire Felt" in cardboard cartons containing thirteen or twenty blocks, and the plaster in hundred-pound paper bags. Samples taken 'during this operation had an average dust concentration of 4,502,880 particles, ten microns or less in size per cubic foot. About 75$ of these dust particles were slightly angular in appearance, five mi * crons or less in size; 10$ were scale-like; opaque; and 15$ were ' rod-like and fibrous. INSULATING TREATING PLANT ACID SUCTION LINE* Seotions of "Sponge Felt Pipe Cover" are cut to fit pipe lengths with an ordinary carpen t e r ^ hand saw. This operation produces on an average 821,280 partioles of dust, ten microns or less in size, per cubic foot. Under . 'the Konimeter Microsoope all of these particles are slightly angular, ,crystalline in appearance, and five microns or less in size. The blocks or sections of the pipe cover are held in place by wrapping #16 gauge galvanized wire about each one. INSULATING CRACKING COIL HOT OIL LINES; All hot oil lines at crack ing coils are insulated with 2" asbestos tubing (85$ magnesia and 15$ asbestos) held in place by fine copper wire. Sections of the tubing are cut to fit particular areas by means of an ordinary carpenter's hand saw. This produoes 7,788,000 particles of dust, ten microns or less in size, per cubic foot. Under the miorosoope, S0$ of these dust particles appeared to be rounded crystalline and about three mi .crons or less in size. Each section of tubing is pounded into place 12 with the open hand so that it fits snugly against the pipe, and then wired into position. The dust produced from both of these operations C averages about 3,379,520 particles per cubic foot. Under the micro scope, approximately 80$ or 90$ of the dust particles appear crystal SI -line, more or less angular, and five microns or less in size; the re maining 10 $ or more are rounded in appearance, and over ten microns ft in size. ft DISMANTLING OR REMOVING OLD INSULATION; As a general rule, the dismantling or removal of old insulation is a more dusty operation ft than the application of new insulation. The old insulation is chopped or cut with a hatchet or small hand-ane, and pried loose and pulled a off with the hands. This produces dust concentrations as high as 5,890,560 particles, ten microns or less in size, per cubic foot. In & -29- ^gjo^tling an old cracking coil 4" tar lino, the average dust concem^fcratio11 was 2 3 2 2 240 particles per cubic foot. In appearance these Krtioles were clear crystalline, rather rounded, and five microns or ji^ss in sire. No fibres were observed in any of the dust samples from ^jinapntling operations. After a few weeks or months service, insula tion on hot lines dries out and appears to disintegrate. This is prob ably due. "k "^ie i'ac^ that suoh insulation is usually covered with a "reathex*-proof material which prevents absorption of moisture from the `'CRUSHING SCRAP ASBESTOS: Sorap asbestos insulation, usually the fs5% magnesia type, is crushed in a belt-driven Williams crusher to pass t h rough a soreen with one-inch holes or slots, and is then mixed with rjew asbestos to make insulating plaster. This operation, which is a rery dusty one, is performed by two men, with an average sex-rice credit 'of about twelve years. Goggles and MSA. "Comfo" or Willson Dust Respi rators are worn. Considerable dust is produoed in breaking up the rsorap insulation by hand prior to cx*ushing (10,195,200 particles, ten ^microns or less, per qubio foot), and also when feeding the crusher fwhich is done by shovelling the brokers-up pieces into the hopper and ^poking them down with a short wooden stick (14,839,680 particles per "cubic foot). Dust counts as high as 27,527,040 particles per cubic 'foot were found in samples taken from over the hopper. These dust confoentrations are dangerously high. Abort 95% of these particles are sharply angular, crystalline in appearance and five microns or less in "size; 5% are opaque scale-like, six microns or more in size. Crushing ^serap asbestos is not a steady routine operation, the exposure varying ffrom eight hours a month to about twelve hours a week. CRUSHING OLD C0RX INSULATION: This operation is performed approxi'mately twioe a year and takes abort twenty or thirty minutes. The inff'sulation is crushed on a belt-driven Williams crusher, by the same men Jr who orush the scrap asbestos. This crushed cork is used for insulating lines in the cold settling plant. The average amount of dust produced is 20,016,178 particles, ten microns or less in size per cubic foot. About QO% of the particles are slightly angular, crystalline, in ap^ pearanoe, and five microns or less in sizej 20% are round, semi-opaque, ten miorons or more. Therefore also a large number of .very small black or dark gr.qy specks, ' IV -GUNITING O P E R A T I O N -Jr What is Gunite and How is it Applied? - Gunite is a mixture of approximately part (one 94 pound bag) of Portland Cement and two parts (twelve scoop shovels) 3* an sharp sand. The sand and cement are mixed dry, shoveled into the hopper unite machine, using water under about 40-pounds per square inch pressure and xessed air at thirty to ninety pounds per square inoh. It is applied under pres }'" as a 3emi-fluid, against the surface to be protected (usually process equipment, s, oracking coil soaking drums and storage tanks). In practically every case guniting is done, it follows immediately, after the sand blasting job used to -a the surace. In most cases, the work is performed by the same crew. The indi ; L holding the gunite nozzle is provided with the same protection as is the for of the sand blast nozzle, and the men tending the gunite machines are proi with respirators and are required to use them while actually handling the sand 'jment. This involves mixing the materials and charging them into the machines jwo dustiest parts of a guniting job). Samples taken during these operations a the following dust counts of particles ten microns or less in size: is f S 1 1 1 1 -30- t v ii n i t n n n n - n n D h d n n B B d - d D I H Qperatlon Particles per cu. ffc. Screening sand prior to mixing with, cement.. Mixing batoh.............................. Shoveling mix into hopper................. 2,493,160 1,699,200 6,485,280 l About 40$ of the dust particles in samples taken while mixing the batch and the hopper were crystalline, quarts-like in appearance, and about five mi- in size. The remainder were dark grey in color and below one micron in size, r2f^ust particles in air coming out of the bottom manhole of a soaking drum being ^Ited averaged 528,640 particles per cubic foot, and were slightly angular, Qline in appearance and four miorons or less in sire. t: A gunite crew oonsists of six men. The average servioe credit of the men in fcrews studied was eight years. Two "nozzle-men" who "spell" each other every rjytfoT three hours apply the gunite. There is one man at the gunite machine, and hfcr** nen soreen "h sand and mix it with cement. Only about 25$ of their working or n^*ne hours Per w 0st per man, is devoted to guniting. 1 Removal of Gunite Lining? Pneumatio chisels are used to remove gunite lining. jJ^jples taken from inside a cracking coil tar separator during this operation had as ^ as 16,595,520 particles of dust, ten microns or less in size, per cubic foot, ggd'an average of 10,804,080 particles per cubic foot. About 75$ of these particles rounded, angular, more or less opaque, in appearance, one micron or less in and 25$ were singular, quartz-like, about ten miorons or less in size. A chemianalysis of the gunite lining showed that it contained 68.2$ free silica. Four 'joJfrom the Plant Labor Department, with an average se'rvioe of seven years, spend Jgout twenty hours per week removing gunite linings from process equipment. An air ^yjhon provides ventilation, and the men are required to use the goggles and respira tor* which are furnished them. V -WELDING A N D CUTTING OPERATIONS Welding has never been considered a dust-producing operation. However, our tudies and those of others indicate that the use of the modern coated electrodes or jids produces a large amount of dust in addition to the fumes which are evolved. An ilectric aro is used for most of the welding around refineries. There are a number ^ owelding jobs, however, for which oxy-aoetylene is used. Oxy-acetylene is also wed for pracsfcioally all burning or outting. it. - WELDING OPERATIONS? .*1 , ELECTRIC ARC WELDING? Electrio sure welding is used on all types of con* instruction and repair work. The average servioe of the electric welders is 'Tibout two years and most of them came from the Labor Department, having jjibeen developed into welders at the individual plants. They are exposed to particulate matter generated by the welding operation on an average of six ` hours per shift, nine shifts out of fourteen. This particulate matter is ordinarily referred to as "fumes or smokes". The particles when found have a much smaller size range than that of dust, such as silica. With same operations there may also be some dv^st present, but the product formed from volatilizing the metal and rod coatings is commonly termed a "fume". All iwelders are provided with approved hand shield or helmets equipped with ==10 Noviweld lens. Welding in shops is done in canvas or wooden booths. A steam or air syphon is installed when any arc welding is done inside of closed fTvessels such as drums or towers. What are Coated Electrodes? Coated electrodes are metal weldine rods covered U- -31- composition which prevents oxidation and permits the formation of stronger and * 5 uniform welds. :po h What Do These Electrodes Contain and What Products Result From Their Use? In x7' the coatings used in modern coated welding electrodes are patented or trade - ets' with special virtues attributed to each. Obviously, it is inadvisable to into these coatings materials which might produce products harmful to man. fSjrTftheless, chemical analyses of both the coatings and their products indicate that continual use of same of these rods might possibly lead to complications. Host of the arc welding at our affiliated plants is done with ^5 Fleetweld ^od electrodes which come in two sizes (5/32" and 3/l6") and-with General Elec * W-20 5/32" coated rods. Other rods sometimes used are #4 Stainweld Zaj>S alloy .tri0 ding nod, 5/32" Stainweld A rods for stainless steel, and Murex Nickel Steel coat rods. Among the constituents of some of these electrodes coatings are: Coated Electrode Brand SiO?. Per Cent. Fluorine Calcium Fluoride "Fleetweld", Lincoln Electric Co......... 30.28 "Murex". American Metal & Thermite Co.... 28,05 "USS Cr-Ni 18-8", Amer. Steel & Wire Co. ...37. 20 "Stainweld", Lincoln Electric Co....... ..12.101 1 "Rezistal K-A-25", Crucible Steel Co......24.03 21. 20 13. 40 14. 50 43. 50 present 'All of the above coatings also contain Iron Oxide (F203) Manganese Oxide, either Mn203 or MnO or both, and Aluminum Oxide (AI2 O3 ), in varying per- 0 entases. - The composition of the fluxes or coatings used in G & E types W-20, W-22 rid if-23 is not available, but it is known that they contain amounts of free silicates aid free silica- According to determinations made by the General Electric Company, the"maximum concentration of free silica on any of their electrodes under a particular jet of conditions is 1,575,000 particles per cubic foot of air with W-20, 778,OQO with W-22, and 1,093,000 with W-23 under other conditions the concentrations might be 3higher or lower than those given. The maximum permissible concentration as listed by-the Metropolitan Life Insurance Company is 7,000,000 particles per cubic foot of air. . ` .jFfgv Coatings also contain cotton fiber, cellulose, or other organic pulp which "creates fumes, but since we are only concerned with dust in this study all fume pro ducing materials will receive no further consideration. ftf* 5? ]trodes ' Welding forms a corrosion-resisting steel with coated corrosion-resisting steel elec slag, among the major constituents of rdiich are: "Stainweld" USS CR-Ni 18-8 "Rsistai" J Fluorine (P)............. .......... g;--Silica (Si02)..,,..................... W Iron, Chromium and Manganese Oxides... ^ Calcium Oxide (CaO).............. `___ 11.4#...... 6.6#......... 14.9# 25.1#..... ..38.5#...........13.3# 22. 3#...... 24. 2#..........15. 2# 50.7#....... 28.0#...........26.7# The major constituents of dusts separated from atmosphere by gravity and col lected from the bottoms of welding chambers after welding corrosion-resisting steel plates with coated corrosion-resisting steel welding rods are: u-a H u li till U U (Iff ff-H-Q Q Q Q-U-U li Ui|-|HJ 11 ti -32- r "Stainweld" USS CR-i:i 18-8 "Rezistal" e (SiO )...................... 11. 0%. 1 9 . 6 # ....... 10.0# Fluoride (CaF )............ 40.5%. 11. 4# 23. 4# f-O^des of Iron, Aluminum and Nickel. 30.2/2. 52. 1*/o 36.6# ykien Tho following is an interesting comparison between the compositions of dust using bare mild steel electrodes and when using coated electrodes for galvanized steel: Brand "Fleetweld" "Wilson" "Murex" Bare Electrodes # ZnO # F23 79.2 62.6 60.5 20.0 60.5 40. 0 Coated Electrodes # ZnO # Fe20 2 67.5 78. 8 72. 0 31. 9 21.5 28.0 Investigations have shown that there m a y be as much as a five per cent, variaJ^aTin composition of* dust produced b y the same make and kind of electrode when used constant conditions but by different operators. "I slap; Ferrio oxide (Fe203) which emanates from all welding arcs, regardless of the g p f o f coating, is disagreeable but not harmful. Concentrations of iron oxide of about (^ `milligrams ^yTorgans. per cubic meter are said to be entirely non-injurious to the respira- Breathing the dense clouds of fumes of zinc oodde, formed when the zinc of the f^lranized coating is boiled off by the heat of the welding arc, causes what is cora- igmly known as "fume fever". This is evidenced by nausea followed by chills and u&- pjeaflant fever. The fume fever does no lasting harm except after prolonged exposure, jad^the effects are not cumulative. Ordinary ventilation, which is necessary in any elding operation, is considered adequate to prevent fume fever. ] What Is The Amount And What Are The Characteristics of Dust Produced By The Trlou8 Electric Arc Welding Operations? There is a wide variation in the amount and Character of dust produced by different types of rods on different materials under ifferent operating conditions. _ FDKE. OR DUST PRODUCED BT ARC WELDING Material Being iSji Welded Hi Rivets inside Cross Coil Drum. Trjr Electrode Used G-E W-20 Coated Size of Electrode 5/32" Particles Per cu. ft. 20,050,560 Mild Steel Blanks Inside Bopth. ig % G-E W-20 Coated 5/32" 14,839,680 Characteristics of Dust Particles. (Sizes and Per centages Estimated) About 98# angular crystal line, 5 microns or less in size; 2# rounded semi-opaque, 10 microns or more in size. About 80# round black or reddishbrown specks, 1 microns or less in size; 20# slightly angu lar crystalline, 10 microns or less but mostly about 5 microns and large number reddish brown specks too small and numerous to count. -33- FUI-IE OR DUST PRODUCED BY ARC WELDING (Continued) | ^ ^ i a l dBeinS Electrode Size of Particles Used Electrode Per cu. it. iffo" Boiler [Rate Inside 7^5 Fleetweld Coated 5/32" 11,441,280 tijti/4" I-Uld ggteel ExpanR J o n Joint In- Wgiie Booth. #5 Fleetweld Coated 3/16" 19,861,793 tff/2n Rolled Rteel Rfs.OOO# per R o in. Tensile Strength) Inlide 6+Foot drum near R e a d of closed #5 Fleetweld Coated ' 3/16" 2,265,600 Characteristics of Dust Particles, (Sizes and Per centages Estimated) About 80? angular crystalline, 3 microns or less in size; 10$ round semi-opaque, 10 microns or more in size; 10$ opaque scale like, 10 mi crons or less in size. Count less number of minute par ticles, reddish brown smudge. About 95$ angular crystal line, 3 microns or less in size; 5$ rounded semi-opaque, 10 microns or less. Count less number of particles reddish brown smudge. All particles 5 microns or less in size; about 10$ angular semi-opaque. Raiding Flange oa 4" Steel B i n e Pipe, In Eid e Booth. Murex Coated jyfe" Boiler FLate Inside ggboth. 7p5 Fleetweld Coated Welding RivB t s in Eourtney Edge R e s i d e Crack i n g Coil EESoaking Drum. =f5 Fleetweld Coated 3/32" 2,756,480 5/32" 490,880 5/32" 6,456,960 ( All particles' 2 microns or less in size; slightly angular, glass-like; dark grey smudge. About 75$ round, metallic opaque, 5 microns in size; 25$ semi-opaque, crystal line. Countless number of minute particles About 90$ sharply angular crystalline, about 1 micron or less in size; 10$ rounded semi-opaque, 5 mi crons or more. Countless number of minute petr-bicles. -34- FOHE OR DUST PRODUCED BY ARC WELDING (Continued) Electrode Sire of Particles Characteristics of Dust Us ed Electrode Per cu. ft. Particles. (Sizes and Per p p "` centages Estimated) Stainweld A Coated 5/32" 849,600 About 60# slightly angular . semi-opaque, 5 microns or less in size; 20# rounded, over 10 microns; 20# very glass-like, 10 mi crons or less. G-E W20 Coated 3/16" 23,222,400 About 80% semi-opaque, red dish brown rounded, crystal line, 5 microns or less; 20# round globules of metal 5 microns or more in size. Countless number of small particles. j&/2n Boiler ypjpe Inside Roebling Iron Rod 5/32" 26,592,480 About 90# black opaque, 1 micronorless in size; 5% rounded metallic globular, 5 microns or less; 5% slight ly angular, semi-opaque, crystalline, 3 microns or less. Countless number red dish brown particle?. ffick Welding K Flange on Standard Bpip in CmtJfiide Welding |Shop. Fleetweld #7 Coated 5/32" 362,496 About 95# black opaque metallic, 2 microns or less; 5% angular'crystalline, 5 microns or less. C o m b les s number of reddish brown particles. ^Baok Welding fifFlange on fis" Standard fjPipe Inside Sooth* Fleetweld #7 Coated 5/32" 1,000,640 About 95# black opaque metallic, 2 microns or less; 5# angular crysta lline, 5 microns or less. Countless number of black particles. gelding Rivfets Inside ^Cracking Coil Vaporfir er (Mild f Steel Alumi n u m Coated). Fleetweld #7 Coated 5/32" 6,253,056 About 95# angular crystal line, 5 microns or less, mostly around 2 microns;5# semi-opaque, round, 5 mi crons. Countless number of black particles. J 35 FUME OR DUST PRODUCED BY ARC_ WELDING (Continued) Electrode Beins HHgelded Us ed Size of Electrode Particles Per cu. ft. Characteristics of Dust Particles. (Sizes and Per centages Estimated) RinS Mild K e l Boiler Fleetweld #7 Coated ^ K f d e Booth. 3/16" 27,662,976 All particles less than 2 microns. 70% round, opaque; ZCf% slightly angular, crystal line. Countless number of black particles, reddish brown smudge. H R J Steel H g f S p Plates fii|ide Booth, Stainweld A Coated 5/32" 2,605,440 All particles black opaque, 2 microns or less in size. s te e l Brnslde fpKkth. Stainweld A '* Coated 5/32" t 12,460,800 About 80% angular opaque, 2 microns or less; 20%, slight ly angular crystalline, 5 microns or less. Countless number black particles, brownish grey smudge. The B. S.Navy recently conducted some extensive test3 with coated electrodes, found that the quantity of dust or fumes developed while welding on galvanized si plate was greater than when bare steel plates were used and the dust remain ' suspension for far longer periods of time. It was also found that the Jrage size of the dust particles was 0.27 microns and that there were 130;000 par oles under four microns diameter per cubio centimeter. Quoting the Navy report: L"It is apparent that considerable quantities of dust are found in any- arc welding operation. The dust formed when operating on plain mild steelor corrosion resisting steel is largely derived from the flux coating on the electrodes, as is shown by the composition of these dusts". What TprysioloEical Effect on Welders is Produced by The Use of Coated feetrodes. According to a study made by Doctors A.T. Doig and A. P. G. McLaughlin an. lungs of Electric Arc Welders (Lancet - V. 20; 771 - 775 (April 4, 1936)), defiuiite pulmonary lesions' which gave rise to striking X-ray changes in the appearance :']the lungs were found in welders which had breathed the dust or fume from coated Electrodes. Quoting Doctors Doig and McLaughlin: "The electrodes or welding rods which contain a core of metal and an outer covering are consumed gradually by the heat generated (about 1500C, ) during the welding operation. The metal in the core of the rod becomes molten and, assisted by the flux contained in the covering, spreads over the surface of the metal which is being welded. The fume is therefore made up of the volatilized constituents of the coverings of the rods together with fine particles of oxidized metial, usually in the form of iron oxides,, In addition the fumes probably contain gases such as nitrogen peroxide and ozone which are formed by the action of an electric spark on the air. The composition of the coverings of the electrodes or welding rods becomes, in the circumstances, a matter of some importance. Many substances, all of which we do not propose to enumerate, are used. The basis of the majority of the coverings is sodium silicate which acts as a flux. Again, the -36- coverings of a certain type of electrode contain asbestos. The rods are sometimes dipped in a mixture containing powdered asbestos and sodium sili cate, or asbestos yarn is wound round the rod and fixed by sodium silicate. In same cases the asbestos completely covers the rods, and in others it is merely a cord which is wound spirally about the rod. "The composition of the fumes arising from electric welding electrodes has not yet been fully investigated. Mr. L.C, McNair, H.N. Engineering In spector of Factories, has however had partial analysis made of the fumes evolved from an asbestos-covered electrode and some asbestos fibres were found. When the particulate matter of the fumes was collected in an Owen's dust-oounter, it was seen that a large proportion consisted of iron oxide particles, with an occasional asbestos fibre. "The X-ray appearances in the well-marked cases differ from the usual picture of asbestosis. In none of the positive cases and in only one of the suspicious cases was there any blurring of the diaphragmatic shadow, and in no case was the heart outlined blurred. The line of the interlo bar septum (a feature present in a number of films of cases of asbestos is) is seen in only one positive case. The opacities in the films are not ac centuated at the bases of the lungs, but on the contrary the upper lung fields appear to be the earliest, and in established cases, most markedly affected. Before asbestosis can be eliminated from the differential diagnosis it must be remembered that the asbestos fibres are being subjected to intense heat and are not in the same physical state as the fibres which are inhaled by workers in an asbestos factory. It is possible that a typical picture of asbestosis might be produced by the inhalation of alter ed asbestos. Merewether. says that - 'the radiographic appearances of the developed or advanced states of asbestosis are distinctive, although they are not specific. While, as is the case with silicosis, certain radio graphic appearances may be looked upon as typical of the disease, freqxiently modifications of and departure from the typical picture occur'. The X-ray appearances in our cases most closely resemble those of a fine silioosis, but the clinical features show two important differences. In the first place, the electric welders whom we examined are all in good health and are fit to work. The only symptoms observed were slight cough and morning expectoration, and in the first case a small haemoptysis occurred. This man has not been away from work even for a day since he was first seen in June, 1S33, and his health at the present time is good. None of the mejf suffers from dyspnaea. Secondly none of them has concomitant pulmonary tuberculosis. "Miliary tuberculosis can be ruled out of the differential diagno sis for clinical reasons, and to sane extent on the radiological appear ances. None of the cases shows the dyspnaea, cyanosis, and tachycardia of acute or subacute miliary tuberculosis. Chronic or healed miliary tuberculosis is rare and it is difficult to imagine that a condition of such rarity would be found in S out of one group of 16 men. In the X-ray films of the welders' chests the fine opacities are irregular in sire and shape, whereas in miliary tuberculosis of the lung the shadows are more uniform. "A further possible explanation of the X-ray appearances in this series of cases is that the inhalation of small quantities of nitrous fumes together with the superadded effect of fine iron oxide dust might set up small areas of chronic inflammatory change, congestion, or fi brosis in the lungs. Again, the iron oxide particles might be opaque to the X-rays and produce the picture without the associated presence -37- fibrosis and congestion." -ACETYLENE '.LLDIIJG: Oxy-acetylene welding is more or less confined to repair jobs or to certain emergency operations where arc welding is not latle or practical. Exposure of men doing welding is more or less irregu They usually wear. American Optical Company or Willson Welding Goggles #4 Noviweld lens. The amount of dust produced by oxy-acetylene welding roODJSidera.bly less than that caused by the use of coated electrodes in arc ing, and varies considerably with the style tip and welding rod being jed as well as the material welded, as is shown by the following table: DUST PRODUCED BY OXY-ACETYLENE WELDING Serial Being Welded Welding Rod Tip Used Particles Per Cu. Ft. Characteristics of Dust Particles (Sizes and Per centages Estimated) ivanized Hood raiding Shop. Norway 5/32" Aireo #4 396,480 About 70/2 slightly angular, semi-opaque, greyish, 5 mi crons or less; 20# rounded semi-opaque, greyish crys talline, 10 microns or more; 10# amorphous, scale-like; 10 microns or more in size. x 2" Bar on, W el ding Oxweld copperized steel 3/16" Aireo #8 509,760 About 80# black opaque, 1 micron or less in size; abort 2C# rounded, crystalline; 5 microns or less in size. r/2* Boiler ate, Soft [Steel, WeldShop. Oxweld copperized steel l/8" Oxweld #6 |f/B" GalvamIzed eet ` _ on, Weld ing Shop. Oxweld o opperi zed 1s/te8e" l, Oxweld *I^Welding Teeth */on 3and Saw. Simmons Saw Welding Rod. 3/64" Aero plane #2 1,019,520 1,359,360. 1,472,640 About 80# round, semi-opaque^ 5 microns or less in size; 10# angular crystalline. Countless number of small black particles. About 80# rounded, semi opaque, dark grey, 1 micron or l6ss in size; 10# slightly angular crystalline, 3 mi crons or less; 10# sharply angular crystalline, 5 mi crons or less; countless number of small dark grey particles. Abort 98# round black opaque, about 1 micron or less in size; 2# slightly angular, crystalline, 3 microns or less in size. 3F- BURNING OR CUTTING OPERATIONS: t_l. WITH OXY-ACSTYLciNE: The oxy-acetylene torch is used both in the construction  H U a u s fl fl U B M B S 2 8 3 g -38- j-the demolition of process equipment and works structures. It also plays ^important part in emergency and rescue work. Goggles with shade #5 Novi ' 2.eaB are provided and their use is required. At the larger plants men an average service credit of six years spend about three-fourths of *eir working time on cutting or burning operations (about half their time given to "burning steel" for new construction). The amount of dust proad is usually greater than that caused by oxy-acetylene welding. DUST PRODUCED BY OXY-ACETYLEKE BURNING fjjftterial Being Particles Characteristics of Dust Particles *gl-' Burned Tip Used per cu. ft. (Sizes and Percentages Estimated) fBurning 5" f Plues (1-1/2" ? thick) Out of Shell Still. Oxweld #2 1,869,120 About 75# round black, 2 microns or less in size; 20# slightly angular, crystalline, 2 microns or less; 5# opaque, scale-like, various sizes. 1/2" Boiler Plate (soft t steel) Oxweld #4 2,718,720 About 90# semi-opaque, black, 2 microns or less 10# round, dark grey, over 5 microns in size. 2*' WITH NATURAL GASr A large part of the burning or cutting at one of the larger southern refineries is done with oxygen and natural gas (SO pounds per square inch pressure). A special torch with a l/l6" x 5/l6" tip made in the refinery shops is used. Two men with an average service of thirteen years spend a major portion of their working time'on this natural gas. They wear goggles with #5 shade Noviweld lens. Samples taken while burning holes in 3" standard pipe in the yard outside of welding shop with oxygen a^id natu ral gas"had a concentration of 471,811 particles, ten microns or less in size, per cubic foot. About 75# of these particles were slightly angular crystal line in appearance under the Konimeter microsoope, and were five microns or ~|G|less in sizej 25# were rough scale-like, opaque, ten microns or less in size, j There were also many minute particles. li: - HEALTH HAZARDS PRODUCED BY WELDING AND BURNING OPERATIONS:Although our ^ study was confined to the fumes or dust produo ed by Welding and Cutting opera 3 tion the'^ibssibility of lead poisoning from welding or cutting iron plates that have been previously coated with red lead should be pointed out. Lead "1 - poisoning from this source is rather common, especially in cutting up old ;j sorap, bridges, tanks, and other iron structures that have through many years of use received protective coatings of red load. The action of the flame 5? volatilizes this lead material and creates a smoke that is poisonous. The 1- same hazard exists in cutting out rivets in new structures. It should also be pointed out that some of the welding rods contain manganese which is very poisonous when taken into the body. There is an ap parent hazard from volatilizing this material, or rather changing it to tho oxide of manganese, and breathing the fumes produced. There are further dangers from carbon monoxide and oxygen deficiency owing to the use of gas-cutting or welding flames inside small tanks or similar confined spaces. It is becoming more and more recognized that persons engaged in cutting and welding operations, either by arc or flame, should have respirator;/ protec. * tion, in all work where there is a possibility of the workmen breathing fumes and dusts created. 3 -39VI - GRINDING OPERATIONS power grinders are perhaps the most universally used of the small power tools. The usual power grinder, commonly known as the emery Wheel, consists %& caS-fc m etal stand and two abrasive wheels mounted on a through shaft which is **^+her belt or motor driven. There are also severed grinding wheels, such as are 3L. d on machine tool equipment where grinding takes the place of lathe and planer v. All grinding operations produce dust to a greater or lesser degree, depending composition and construction of the wheel, the- material being ground and the T^asfciTation or exhaust hoods provided. ilia? What is the Composition of Grinding Wheels? Grinding wheels are made of j ' either bauxite which is mined, or silicon carbide which is made by heating a mix- ^tur of sand, coke and common salt in an electric furnace. The bauxite or ailicon ca-Tbide are crushed to the desired grain size, mixed with an adhesive sub stance called a bond, and formed into wheels, discs, cones or cylinders. 'There are jn&zty wheels in which the binder is shellac, rubber, bakelite and other organic cam- pounds. Bauxite wheels are known in the shop as "Alundum" and "Aloxite", while silicon carbide wheels are known as "Crystolon" and "Carborundum". Alundum wheels should be -used on material of low tensile strengths such as cast iron, brass, alumi num, copper and marble. Is ____ _A_b_r_a__s_i_v_e Dust ____________ H_a_rm_f_ul_? According to Dr. - W. Irving_ Clark in a _pe._per read St a meeting of Government Officials in Industry (Boston - May 21, 1931) the artifi- oal abrasives, aluminum oxide and silicon carbide do not contain, free silica and their dust cannot produce silicosis. The dust, like any other inorganic dust, can, "however, if breathed for a long period of time in large quantities, produce an X-ray picture similar to that of early silicosis. This picture ohanges very slightly as years of exposure increase, and at no time are the nodules, characteristic of sili cosis, evident. Unlike silicosis, there is no progress in the process after expo sure ceases and there appears to be no marked physical disability. Although there is no silicosis, the X-rays do show signs of pneumoconiosis. Carborundum dust, chemically, is silicon carbide. According to Miller and .Sayers (U. S. Pub. Health Rep. Vol. 49 #3 of Jan. 19, 1934) carborundum dust when in jected into the peritoneal cavity of guinea pigs produced no reaction and was termed ^"inert". Dusts such as quartz and flint - silicosis producing dusts - produced a ;proliferative reaction. ' f- Leroy U. Gardner (U.S. Pub.Health Rep. Vol. 50 #21 of May 24, 1935) reports that carborundum produces practically no reaction when inhaled by guinea pigs in high concentrations over a period of time. Quoting from Dr. Gardners article, the part pertaining to carborundum dust: "The dust which does reach the traoheobronchial lymph nodes apparent ly lacks the proper physiochemical properties to stimulate any but a very slight proliferation of connective tissue, In the lungs, there is practically no fibrosis." ' The Journal of the American Medical Association (Notes and Queries 103, 1472, 1934) makes this statement regarding the health hazard of breathing dus from arti ficial abrasives: "Only silica (Si02) is capable of inducing silicosis, but any other mineral dust under conditions of prolonged and gross exposure may cai;ne some increase in pulmonary fibrosis. If the relative potential harm of l silica is rated as 100, these other non-toxic mineral dusts may be rated -40- b b n B - u - B - a n - n - n - n - B E i l u s J? only on the r^er of 5 or 10. " Z Despite this comparatively low rating of harmfuln.ess of these dusts it is -j -graJ.ly considered advisable to use dust hoods and exhausts wherever practical as r fi is clinical evidence that workers exposed to heavy concentrations of dust of ^ iind are more liable to develop diseases affecting the nose, throat and chest P^ing the winter months effort should be made than those not exposed to keep the dust count to dust. Dr. Clark believes that below twenty million particles of than ten microns per cubic foot of air, * '& I What are the More Frequently Used Types of Grinders, the Quantity and Character I^ the Dust They Produo e? The grinders most commonly found in the refineries and as- .-^jiated activities are* ^ A - TANDEM FLOOR TOOL GRINDERS: Tandem floor tool grinders, the most ;Ye.uently used type, are in most cases motor-driven and operate at a speed of from . 'i50 to 1850 RFM. The type of wheel or grinding media selected depends upon the ma larial to be ground. Generally speaking, the wheels found in most of the machine Jjjjops and wood working shops around our refineries used: 1J ',' l-l/2" x 10" Norton tAl,undum (Grade P, Grit 46) wheels for sharpening tools and for general service grinding. 1-1/2" to 3" x 14" Carborundum wheels for miscellaneous grinding. fj J lw. Scmetime3 14" grain 144, grade 3" x 16" Carborundum (Grit 30, Grade K) wheels for grind ing lathe and other machine tools. two different wheels are used on tandem tool grinders; for 24, grade Q Norton Alundum vitrified wheel on one side and M A l u n d m wheel on the other side. example, a a 2" x 14" 2" x grain J .. The amount of dust produoed by the operation of tandem tool grinders depends , primarily upon the composition of the wheel and the hardness and character of the | object being ground. Theoretically, the operating speed and the pressure should also be determining factors, but these were not studied. The following are average 'll dust counts of particles ten microns or less per cubic foot in samples taken in the breathing tftne of -the person using the grinder during the grinding of various ob jects on various wheels of tandem floor grinders: Operation Particles per C cubic foot 8 Grinding Cast Iron on 2" x 12" Aloxite (46M Grit) Wheel......... 11,648,960 " a Steel Sleeve on a l/2" x 10" Carborundum Wheel....... 8,127,840 s " " Hard Steel Chisel on a 5/8" x 8-1/2" Alundum Wheel... 7,476,480 " "" " " " " 1/2" x 10" Carborundum Wheel.. 1,670,880 a ' n nit n it n tt 3 x ^.O" " " 906,240 " " Pneumatic Tool Steel Chisel on a 3-1/2"x 14" Norton a Alumdum (3836 - 0.53) Wheel................. ........ 1,869,120 " " Chisel Bar on the same wheel (3836 - 0, 5B Alumdum)... 4,134,720 3 " " Tool Steel Chisel on a 1" x 10" Carborundum (Grain 46M) Wheel.......................................... 2 , 5 9 4 , 1 1 2 = " Tool Steel on a 2" x 14" Alundum (24 grain, grade Q) Wheel 396,480 n n n it it it ti ^4 tt " M) " 1,019.520 w. " a Lathe Tool on a l/2" x 12" " (Grade ?) Wheel...... 339,840 n n n n n tt it it ^ it ^ n ...... 1 , 3 3 1 , 0 4 0 w Operation (Continued) Partiolea per cubic foot Grinding a Lathe Tool on a 3" x 16" Carborundum (grit 30,grade K) Wheel....... " Mild Steel on a l-l/2" x 10" Alundum Wheel.............. " Steel Dies on a 3" x 14" Carborundum Wheel.............. " Squaring Shear Blades on a 1-1/2" x 16" Carborundum Wheel. 362,496 6,655,200 56,640 2,577,120 Dust Produced By Operation of Tandem Floor Grinders.1 As would be expected, there is a wide variation in the appearance of the dust particles under the Koni- microscope. These examples however, will give an idea of the characteristics of. the dust produced during the operation of Tandem Floor Grinders: 1 Material Being St Ground * .a '1 " x 3" Mild Steel Ban Size of Wheel Type of Wheel 1-1/2" x 10" Alundum (Grit 46, Grade P) Tool Steel A % Tool Steel (Same ma> t erial as V- above) J Lathe Tool _:vX.-. t" Chisel 3ar iJS- . Pneumatic Hand Tool Steel Chisel 5Lathe Tool Lathe Tool (Same as above) 2" x 14" 2" x 14" Alundum vitrified (Grit" 44,Grade M) Alundum vitrified (Grit 24, Grade Q) 3" x 16" 2-1/2 x 14" Carborundum (Grit 30 Grade K) Alundum (3836-0. 5B) 2-1/2" x 14" Alundum (3836-0. 5B) 1-1/2" x 12" Alundum (Grade P) 1-1/2" x 12" Alundum (Grade R) Characteristics of Dust .Particles. (Sizes and Percentages Estimated) About 70$ angular crystalline, 5 microns or less in size; 30$ metallic shreds; 10% white opaque, slightly singular, over 10 microns; many small black specks. About 90% angular crystalline, 2 microns or less in size; 10$ opaque, 1 micron or less in size. About 60$ round, semi-opaque, 10 microns or less in size; 40$ angular opaque, 5 microns or lest in size. About 75% round, crystalline, 5 microns in size; 25$ slightly angular. t About 70$ slightly angular, 3 microns in size; 30$ black, opaque, metallic. About 98$ round, black, opaque, one micron or less in size. About 50$ angular crystalline, 2 microns or less in size; 50$ round, black, metallic, 1 mi cron or less in size. ...... .... About 75$ angular crystalline, J 2 microns or less in size; 25$ | round, black, metallic, 1 mi- i cron or less in size. j i j? ^ jy ja' sxj/ jp -42- DUST PRODUCED BY TANDEM FLOOR GRINDERS (Concluded) rtrial BeinS *% Ground Iron Size of Wheel Type of Wheel 2" x 12" Aloxito (Grit 46, Grade M) Characteristics of Dust Particles. (Sizes and Percentages Estimated) About 85)2 sharply angular, crys talline, 5 microns or less; 10$ rounded angular crystalline, over 10 micronsj 5% opaque scale-like metallic, 10 microns or lessj large number of black metallic specks. r9 "hard" wheels are used for grinding soft cast steel,- atout 98$ of the dust par oles are metallic and less than one-half micron in size. f. With the exception of a very small number of men who devote about 95$ of trfr' working time to actual grinding, there is a very wide variation in the number isen exposed and the length of such exposure to dust produced by the operation of ^jyjeo floor tool grinders. In only one case was a respirator worn. Goggles have ^ provided and their use required in most cases. B - TANDEM BENCH GRINDERSt These grinders are small in size and are used for Opening small tools and light grinding. They are all motor-driven and operate at keut 3400 R.P.M. Different grade wheels are used, usually l-l/8" x 8" Carborundum ;r*,in #80) on one side, and on the other a 1" x 8" Carborundum (Grain #90), The count of dust produced by the operation of tandem bench grinders varies with thema- *ri&l being ground and the composition of the wheel, but these average dust counts ^ fairly representative - XTj i Operation ' . . Particles per cu. ft. j Grinding Cold Chisel on l-l/8" Grain #80 Carborundum Wheel.... 5,909,440 ` " " " " 1" x 8" " #90 n .... 8,401,600 ' " l/2" Boiler Plate on 1" x 8"#90 " * .... 12,460,800 " Hard Steel Chisel on 5/8" x 8-l/2" Alundum j (Grain 46^ Grade P)___ ...................... 7,476,480 > a ` Dust particles in samples taken during the operation of the' tandem bench Tinder have the following characteristics ... Material Being Ground Size of Wheel Type of Wheel Characteristics of Dust Particles. (Sizes and Percentages Estimated) [Medium Steel Cold Chisel v 1-1/2"x8" Carborundum (#80 Grain) About 75$ slightly angular crys talline, 5 microns or less in size; 20$ round opaque, metallic, one micron or less) 5% semi opaque, over 10 microns and look like chips of glass. Medium Steel Cold Chisel (Same tool as Above) t 1" x 8" Carborundum (#90 Grain) About 80$ round opaque, 2 microns or less in size; 20$ slightly angu lar crystalline, 5 microns or less in size. -43DUST PRODUCED BY TANDEM BENCH GRINDERS Material Being Ground Size of Wheel Type of Wheel Characteristics of Dust Particles. (Sizes and Percentages Estimated) i/2" Soft Steel Boiler plate (Taking off rough edges) 1" x 8" Carborundum (#90 Grain) About 90/i round, black, metallic, 2 microns or less in size; 10% slightly angular crystalline, 5 microns or less in size. Sard Steel Chisel t-ar 5/8" x 8-1/2" Alundum (Grain 46, Grade p) About B5% round, black opaque, 2 microns or less in size; 15/S rounded crystalline, 10 microns or over. C - SINGLE FLOOR TOOL GRINDERS: There are only a few single floor grinders use. They fange in size from 1" x 10" motor-driven (1750 RPM) to 2-l/2" x 20" W belt-driven (1250 RIM). The larger size is used for heavy grinding such as blanks 2" and large tools; the smaller sizes for sharpening tools and miscellaneous grind~ ing. The wheel on the large grinder is Carborundum (#90 Grain). For the smaller Jisize class Grain 46, Grade M Carborundum wheels are used on the 1" x 10" and Grain ^ 2 4 , Grade*Q Alumdum wheels in the 1-1/2" x 14" size. Samples taken during the opera tion of Single Floor Grinders had dust counts as follows: Operation Particles ner cu. ft. Grinding Tool Steel on l-l/2" x 14" Alundum Wheel (Grain 24, Grade Q)................ 679,680 " Chisel on 1" x 10" Carborundum Wheel (Grain 46, Grade M)................ 2,594,112 " 1/2" x 4" Mild Steel Bar on 2-l/2 x 20" Carborundum Wheel (Grain 90)....... 4,451,904 5 The hoods which almost completely enclose these wheels act as practical duet collec- " tors. . Dust particles produced by the foregoing grinding had these characteristics when examined under the Eonimeter microscope it Material Being Ground Size of Wheel Type of Wheel Hard Steel Tool Bit 1-1/2" X 14" ? 1/4" x 2" Mild 1" x 10" 1 Steel 3ar 1 /2nx4" Mild Steel 3ar 2-1/2"x20" Alundum (Grain 24, Grade Q) Carborundum (Grain 46, Grade M) Carborundum: (Grain 90) 1 .......... ...............................................- Characteristics of Dust Particles. (Sizes and Percentages Estimated) All particles were 2 microns or less in size. About 6O5* were an gular crystalline; 40/o were rounded opaque. 2% About 9B% were black opaque, 2 mi crons or less in size; slightly angular,5 microns or less in size. About 85^ were slightly angular crystalline, 5 microns or less in size;about 15/ black semi-opacue, angular metallic, 2 microns or less in size. n m u is u n s x in ia ff ^ -44- v . D - U Tr:LRSAL GRINDERS: As the name would indicate, universal grinders are for a wide variety of purposes and therefore are in more continuous opera^ than are the other grinders, with the exception of the tandem floor tool grind ' There are two types or makes, the Brown Sharpe Universal Grinder which has Operating speed of 3750 RPM. and the Grand Rapids Universal Grinder which grates at about 3850 RPM. The following abrasive wheels are used: sJh gr fg? l/?." x 5" Norton Co. 3846 J 5B Alundum wheel for grinding hardened carbon tool steel. 1/2" x 7" Norton Co. 3846 I 8B Alundum wheel for grinding high speed tool steel. : |jjj^ 2" x 3-l/2" Carborundum Co. grit 401-P-25, type 12 ^ Aloxite wheel for grinding case hardened steel. l/4" x 10" Carborundum Co. wheel used for cutting, jy'' 1" x 10" '' " " " " " sharpening tools, reamers, dies and drill bits. Samples taken during the operation of the various'Universal grinders had ust counts as follows: * Operation Particles per cu. ft. 3 Dressing l/2" x 7" Alundum (3846 I 83) Wheel with a . "Diamond Point"............................... *........... 1,397,120 SP :J|. (Evidently the clouds of dust which come off during 5* dressing have particle langer than 30 microns) S dr Grinding High Speed Tool Steel on l/2" x 7" Alundum Wheel v (3846 I 8B).......... 1,846,464 SPi 5; " Hardened Carbon Tool Steel on 1/2" x 5" Alundum Wheel / *. .(3846 J 5B)............................ 6,683,520 ar it; " Case Hardened Steel on 2" x 3-1/2" Aloxite -X (Grit 401 - P - 25 Type 2).............. 84,960 ^ Cutting off Tool Steel with l/4" x 10" Carborundum Wheel..., 1,416,000 # * 2SP ` Dust particles in samples taken during the operation of Universal grinders have these characteristics: A Material 3eing Ground Sise of Wheel Type of Wheel Characteristics of Dust Particles (Sises and Percentages Estimated) - Dressing Wheel With a ,"Diamond Point" 1/2" x 7" Alundum (3846 I 8B) High Speed Tool Steel (a Landis Pipe Chaser) 1/2" x 7" Alundum (3646 I 83) About 80^ slightly angular crys talline. About 3 microns in size; 20% black opaque, round, about 1 micron or less in size. About 60% opaque angular, about 2 microns or less in size; 4-0% slightly angular, crystalline, 5 microns or over in size. 1 n Dust particles in samples taken during the operation of Universal grinders these characteristics (Continued): e?e "material Being j Ground Size of Wheel gardened Car-- \donated Steel f(Pipe Grip for lpipe Machine) 1/2" x 5" Type of Wheel Alundum (3846 J 5B) % ;Case Hardened Steel (Plungfers for Fill i n g Machine) 2" x 3-1/2" ** Aloxite (Grit 401-P- 25 Type 12) Characteristics of Dust Particles. (Sizes and Percentages Estimated) About 30# angular crystalline, about 2 microns or less in size; 70# round black opaque, less than 1 micron in size. Numerous black specks too small to count. Several large oblong black opaque par ticles about 20 microns wide and 35 or 40 microns long. All particles black opaque, 1 mi cron or less in size. jgg E - SURFACE GRINDERS: Surface grinders are used almost exclusively on valves and dies. They are equipped with either 1/2" x 8" Norton Alundum (1946E) wheels or \jzn x A" to 6" Carborundum (Aloxlte) wheels. No dust collectors are provided, the dust being thrown out into the atmosphere. Samples taken during the operation of surface grinders had the following dust concentration (10 microns or less): Operation Particles per cu, ft. Grinding " $ Dressing gv-. Soft Cast Steel Valve on l/2" x 6" Carborundum. Aloxlte Wheel.......................... Tool Steel Die on l/2" x 8" Alundum (1946H) Wheel.................................. Surface of l/2n x 8" Alundum Wheel with a "Diamond Point"................................. 566,400 1,019,520 1,132,800 About 70% of the particles from grinding the steel die were metallic, 3 mi crons o r #less, whereas 98# of the particles from grinding the soft steel valve were stallie. Many of the particles were too small to identify or count accurately. if* F - LANDIS TOOL GRINDERS: Landis tool grinders are usually equipped with two different types of.wheels, one for side grinding and the other the ordinary type. W./2" x 12" Carborundum Aloxite (Grit 40, Grade H, Bond 33) is used for general purpose grinding such as bull chisels, diamond points, cold chisels, flanges and wrappers. The Side Grinding Type is usually a 2-l/2" x 1-1/2" x 12" Grit 46A-P P678 Aloxite brand AA wheel used for grinding Landis dies. At one plant the wheels of the Landis tool grinder are enclosed by hoods at the rear of each of which is ttached a two-inch pipe connected to a three-inch pipe which discharges into a ewer. Suction is induced by a stream of compressed air from a half-inch pipe inlerted in the two-inch pipe just b.ack of the hand. This arrangement acts: as a sy phon and pulls the dust away from the person using the grinder. Samples taken dur ing the operation of Landis tool grinders had dust concentrations as follows: ' i f n n n u n n n u Q B f l i n i f l l J J J l J I l f l J P J / J J j P J i t f It 8 9 $ -46- f Operation Particles oer c m ft ""Dressing l-l/2" x 12" Aloxite Wheel (Grit 40, Grade H, Bond 33)............... (Evidently particles in the cloud of dust thrown off by -the 2-1/2" x 6" Metcalf Emery Wheel Dresser are larger than .30 microns in size) ' 226,560 ^Grinding "Diamond Point" Chisel on l-l/2" x 12" Aloxite Wheel rl f (Grit 40, Grade H)............................................. .Grinding 2-1/2" x 6" Landis die on 2-l/2" x l-l/2" x 12" Aloxite Wheel (Grit 46A-P P678)........................... 2,067,360 755,203 Under the Konimeter microscope dust particles in samples taken while dressing ^1-1/2" x 12" Aloxite Wheel appeared slightly angular with a yellowish tinge and Te five microns or less in size. About 75# of the particles from grinding the kdis die were round, opaque, and less than 1 micron in size; 25# were slightly jugular crystalline, less than 2 microns. Particles from grinding the diamond point jjiisol were less quartz-like than those from grinding the die. This difference is, course, due to difference in the composition of the two wheels. On an average, T,dis tool grinders ar used about twenty hours a week, visually by different men. ______ G-- YANKEE DRILL GRINDER: Used for grinding all types of drill bits. Has a ' side grinding type 1" x l-l/2" x 9" Carborundum Aloxite (Grit 30, Grade M, Bond 28) 'bee1 Operating speed 1735 RPM. On an average a Yankee Drill Grinder runs about J three hours a day and is used by four different men with an average service of twelve years. y Samples taken during the grinding of a 2-5/16" high speed drill had an ave rage of 1,000,829 particles, ten microns or less, per cubic foot. About 70# of these dust particles are slightly crystalline in appearance, five microns or less' in size; 50# were rounded, semi-opaque, over ten microns in size. There were also a few small metallic shreds. No exhaust or dust collector is used in this grinding. ;y H - AUTOMATIC CIRCULAR SAW SHARPENING MACHINE: There are a number of these grinders in use in the wood working operations - such as in the production o.f wooden barrels, boxes and crates - closely associated with the refining of petroleum pro ducts. Since they are automatic when once put in operation, there is very little dust hazard except where no exhaust or dust collectors have been installed and the dust produced is thrown into the filing room atmosphere. Automatic Circular Saw Sharpening Machines are equipped with l/4" x 8" Norton Alundum Wheels (Grain 60, Grade N), 3/8" x 8" Norton Alundum (1946 M) wheels, or l/2" x 6" Carborundum wheels. The average dust produced during operation of these machines is: Wheel Particles per cu. ft. l/2" x 6" Carborundum....................................... 1,923,280 " - 1/4" x12" " 3,568,320 , 5;3/8" x 8" Alundum (1946M).................................. 2,095,680 JT 1/4" X 8" " (Grain 60, Grade N)...................... 1,461,312 % -- XL About 98% of dust particles in, samples taken while sharpening circular saws on the Carborundum wheels were black metallic in appearance, and one micron or less ia size. About 75# of the particles from the Alundum wheels were rounded crystal line, 5 microns or under in size, and 25# round black metallic, about one micron or less in size. There were a number of small metallic shreds in the samples from the thicker (3/8" x 8") wheel.I I - AUTOMATIC HAND SAW GRINDER: After the Band Saw has been inserted and the hine adjusted, this grinder works automatically. The wheel ordinarily used is a x 8" Grain 50, C-rade N Norton Company Alundum. The wheel is refaced or dressed a Metcalf Emery Wheel Dresser about twice a day. The average dust produced by ~bis dressing operation is 2,284,480 particles less than ten microns per cubic foot. ?hout 95$ of these dust particles are sharply angular crystalline in appearance ,gr Konimeter microscope,, and about five microns or less in size. The dust ^%-oduced during the sharpening or grinding of the band saw blade is on sun average ijfjLy 877,920 particles per cubic foot. About 50$ of these particles appear angular '^yg-taHine and about 50$ round black opaque. All of them are about two microns or `'ess in size. ' _ J - AUTOMATIC BAND SAW LAP GRINDER: Used to grind ends of band saw prepara t o r y to welding them together. The grinding wheel visually used is 5/8" x 10" Grain Grade M, Norton Company Alundum. No dust collector is provided although a dust ^ 'ount as high as 16,142,400 particles, ten microns or less, was found in one sample f'^jcen in front of the wheel while it was in operation. The average dust produced this lap grinder was 4,984,320 particles per cubic foot. About 80$ of these dust ^particles were semi-opaque, slightly angular in appearance, and two microns or less size; 20$ were black opaque, about one micron or less in size. % K - PLANING KNIFE BLADE GRINDER: Uses a l/2" x 8" Grain 46, Grade N, Norton 'Company Alundum wheel. Operating speed 3000 RPM. No hood or any other protection, 'average dust produced while sharpening a Planer Knife Blade was 566,400 particles, ^ten microns or less per cubic foot. About 60$ of these dust particles were slight l y angular crystalline in appearance and about two microns or less in size; 40$ were opaque of various sizes from about seven microns or less. There were a few small fmetallic shreds. lip L - LINDERMAN CUTTER GRINDER: Sharpens nutters from the Linderman machine \for tongueing and grooving. Grinder uses a l/2" x 6" Norton Alundum (Grain 60,Grade *N) cup wheel. Operating speed 3000 RFM. There is a hood guard over the top of the /grinding wheel, but no exhaust or dust collector, although dust counts as high as :14,386,560 particles, ten microns or less, were found at the front of the grinder in (operation, and 12,574,080 particles per cubic foot in the back. The average dust -1 produced was 9,137,920 particles per cubic foot. About 70$ of these dust particles 'are round semi-opaque in appearance under the Konimeter microscope, and three mi crons or less in size; 20$ are round, globular like particles, seven microns or less 4in site; and 10$ are metallic shreds about two microns wide and 20 to 30 microns long, jThere.%re many minute crystalline particles too small and too numerous to count ac- fcurately. ' y. M -- GANG SAW BLADE GRINDER: Uses a 5/8" x 10" Grain 50, Grade M, Norton ^Company A1undrum wheel, operating at 1800 RPM. A rather crude dust collector has (been installed, but the average dust (8,760,320 particles per cubic foot) produced by this grinder in operation indicates that it is inadequate. About 90$ of the ^dust particles in samples taken during the grinding of a Gang Saw Blade were semi- ^opaque in appearance and about two microns or less in size; 10$ were black round, .opaque, one micron or less in size. There were numerous minute black specks too small to count accurately. ia a.- . 7f N - EDGER SAW GRINDER: Uses a 3/8" x 8" Grain 60, Grade N, Norton Company Alundum wheel, operating at 1650 RPM. No hood or any other dust collector for this grinder. The low dust count, an average of only 453,120 particles, ten microns or less per cubic foot, indicates that there is very little real need for such equip ment. The dust particles produced while grinding an Edger Saw 31ade are angular crystalline, about two microns or less in size. . 0 - CIRCULAR SLAB CUT-OFF SAW C-RINDER: Uses a 3/4" x 10" Grain N, Norton y Alundum wheel operating at 1650 RR, A rather ineffective dust collector has {^stalled, but the average high dust concentration (10,931,521 ^articles oer ^ic foot) shows that it is inadequate. About 80# of the dust particles in samples ten during the sharpening of a Circular Slab Cut-off Saw were opaque in appearance, ^ jaicrons or less in size; 20# were slightly angular crystalline, five microns or in size. There were also a large number .of minute black opaque particles. * * ! P - "HOG KNIFE" GRINDER: Uses a l-l/2" x 24" Carborundum wheel operating at Jq RB4. This grinder is completely enclosed by a metal hood, but the dust is dis tuned onto the floor through an opening in the lower part of the hood. The average wjj-t produced by the operation of this grinder is 1,869,120 particles per cubic Mot. About 75# of these dust particles were angular crystalline in appearance under Konimeter microsoope and four microns or less in size; 25# were round, black que, two microns or less in size. H Q - CUTTER GRINDER: Uses a 3-1/2" x 2-l/2" x l/2" Nort on Alundum wheel (3846 j 2 5). The amount of dust produced depends upon the material being ground as is jhc*n by the following! Grinding a steel counter sink........... 736,320 particles per cu. ft. f " " " reamer.......... ..... .1,019,520 " " " " yke dust particles are about 98# opaque metallic in appearance and about one micron 9r less in size. 3*. What Precautions Should Be Adopted For Safeguarding Those Who Use Grinding Wheels? Authorities generally agree (Jour. Indust. Hyg. Vol. VII No. 8 August 1925 " ^351) that workers who habitually use grinding wheels will run but slight risk of developing pneumoconiosis if they use certified abrasive rather than sandstone wheels for all grinding operations and if the machines upon which the artificial abrasive wheels are mounted are properly hooded and excessive dust removed by suction. v Control of Dust From Grinding, Polishing and Buffing Wheels. Exhaust systems for grinding, polishing and buffing wheels vary widely in design. In the case of grinding, the hoods used serve not only to provide means for capturing the dust but also act t o ;'protect the worker in case the wheel bursts. The chief difficulty to be overcome in grinding'wheels, .according to U. S. Public Health Bulletin No. 217, "The Determination and Control of Industrial Dust" (1935), is the outward sweep of air, a fan action, due to the revolving wheel. This effect is very marked with high speed and rough wheels and is so strong that in many instances it is sufficient to counter act the normal inward flow of air. The same effect exists with polishing and buffing wheels but to a less marked degree. Practically all industrial States have codes regulating the construction and 'dust connections for grinding, polishing and buffing wheels. They also regulate the air required for wheels of various sizes in terms of static suction in the connect ing ducts. These codes possess no uniformity. However, the requirements designat ed by State codes must be followed. In States where no codes have been adopted it is desirable to provide exhausts on all grinding wheels with a suction at the con nection to the hood sufficient to produce a difference of level of at least two inches of water between the two sides of a T^-shaoed tube. A number of the wheels have been provided with suction exhaust produced by a motor driven fan or a hood, with a two-inch pipe one end of which is immersed in a bucket of water. The dust is drawn in by the rapid revolution of the wheels (1750 REM). This simple arrangement is particularly effective. Three samples taken near the discharge of a motor driven suction fan connected with the hood of l-l/2" x 1C" -49- indum (Grit 46. Grade ?) wheel while a tool was being sharpened had an average of 0?6 989 particles per cubic foot which would have otherwise been thrown into the -chine shop atmosphere. 'S' As pointed out by Dr. W. Irving Clark in his paper "Dust Hazards and the Pre- ^untion of Injury from the Same" read at a meeting of Government Officials in Indus- ^ try at. VB ost1 o_n__ , XH? a-- s_ s_ , on A V . V Mi #ay 1 ^ * O 2T 1, 119Q 3' i1l , the 4--V \ A most T a k 4> / effective i h h r> /* A 4 -- j-%. mnei -tVh% AoJd Aof removing A-- a m >. a m fine h J A_ A. tides of dust is by suction applied as close as possible to the point where they u-e generated and the amount of this suction is great enough to overcome the dis- -^rsing action upon the dust of the work being done. The velocity at the air ducts -'of an efficient dust removing tube should be 1500 linear feet per minute. Quoting :lir. Clark: ^ '3j|' * f jjT 3^5 "Ho matter how well a workman is protected he should be kept under medical supervision and have a periodic examination of his heart and lungs. In addition, the X-ray should be employed freely in order to detect early signs of fibrosis in the lungs and to show ary signs of early pulmonary tuberculosis. In my experience with workers exposed to inorganic dust, non-silicous in character, a yearly physical examination with an X-ray every second year after ten years exposure is sufficient but it must be remembered nhat this is the result of work in a factory where the character of the dust is relatively harmless and where excellent dust remov ing devices are installed on every machine where it is possible. Where free silica is present in large quantities the examinations should begin after two or three years exposure and an X-ray should be taken every year. Dr. Clark also states that men who are "asthmatic, who suffer from chronic bronchitis, or who have had pulmonary tuberculosis should not work at a dusty job. , VH - HANDLING POWDERED OR PULVERIZED MATERIAL j A large amount of powdered or pulverised materials are used in the treatment if petroleum products and boiler water and in the manufacture of greases and insec ticides. In most cases approved respiratory protection is provided and its use re quired when handling the materials. Exposure to dust is usually intermittent and of ih.orfc duration. Among the powdered or'pulverized materials used in the refining, of petroleum products and associated activities are: "aVr - LITE: Lime is extensively used in the hydrated fora and to a muoh lesser de gree as I m p quicklime. # 1 Hydrated Lime? Used in the preparation of lime soap grease and the mantw 4 facture of pressure gun and cup grease; also in the treatment of boiler feed- $ water to "soften it". It comes in fifty pound paper bags by railroad, usual l y about 1,000 bags to a car. According to a chemical analysis of a typical ^sample, hydrated lime contains: ' Fe203Al203.......... 0.30 per cent. t CaO. 1............... 73.64 " " MgO................. 0. 93 " " Insoluble Silica .15 Residue..... 1.01 " " If (Remainder mostly Moisture and Volatile Matter) :r. From 150 to 350 pounds of lime are used per batch in the manufacture of greases. -50- (ttn n n u n m u B B se u es s-m -s-ti-sss-s s s s z s # sacks of lime are usually opened and dumped into the mixing kettle. Con siderable dust (as high as 34,890,240 particles less than ten microns per cu- ^io foot in one sample) is produced by this operation. The average dust pro v e d is 4,733,305 particles per cubic foot and the average exposure per batch ia about five minutes. The number of batches made per week varies from one to *wenty-five. No respirators are worn by men dumping hydrated lime at any of points where it is used with the exception of Baton Rouge where the wear ying "Comfo'1 respirator is required. About 85# of the dust particles :i_I1 samples taken while dumping lime in mixing kettles are slightly angular, R i g h t l y opaque, crystalline, in appearance under the Konimeter microscope, and rive microns or less in size; 15# are rounded, semi-opaque, with a metallic igj-eyish color, ten microns or over. There are also a countless number of very ismall particles. 3^ Only a small quantity of Hydrated Lime is used in the treatment of boiler rfeedwater. About 70 pounds of lime is mixed per batch and about six batches "tre ms.de every day (24 hours). The mixing is done by one man on each shift. Although the exposure is very short, the men at Ingleside Refinery wear Willson ^"Dust-tite" respirators while dumping lime. The average dust produced during this operation is only 657,024 particles, ten microns or less, per cubic foot. This low dust concentration is the result of a spray of water from a two inch *pipe across the hatch of the mixing tank just below the opening while sacks are .being dumped. Consequently, the material is wet almost as soon as the lime is 'introduced. About 95# of the dust particles in samples taken while -the lime -i'uas being dumped into the mixing tank were semi-angular crystalline in-appear- T'anoe, and from five microns or less in size, and 5# were round opaque, two mi- borons or less in size. - Lump Quick]ime? Used to "soften" boiler feedwater. The lime used for this ipurpose is Oyster Shell Lump Quicklime (97# CaO). It comes in fifty pound tpaper-lined burlap bags, and eight bags axe usually used per batch. One batch ^ is made per shift. The dumping and mixing requires about ten minutes per batch, T&nd the man doing this work is protected by rubber type goggles, but no respi- j *rator. The average dust produced by handling the bags of lump Oyster Shell :Quicklime is 2,605,440 particles per cubic foot. The average dust produced ;while dumping the bags of lump Oyster Shell Quicklime into the mixing tank is 294,528 particles, less than ten microns, per cubic foot. The handling and ' dumping of this Oyster Shell Quicklime produoes less dust than is produced by -jthe hydrated lime usually used. About-- 95# of the dust particles in samples i> ^taken d u A n g the dumping of Oyster Shell Quicklime into the mixing kettle ap- H pear slightly angular, crystalline under the Konimeter microscope, and are five 7 miorons' or less in size} 2# are round, semi-opaque, over ten microns in size; and 3# are black opaque scale-like, five microns or less in size. t. What Physllogical Effect is Produced by Lime Dust? According to the Inter national Labor Office (Occupation and Health, Vol. II, 1934) particles of lime mix with the sweat of workmen handling it and irritate the uncovered pores of the skin} lesions of the mucous membranes are also set up. We are told that: .? "The action of quicklime is due partly to its avidity for water 1 (deh.ydra.tion), to the heat given off in its reaction with water, - - and partly to the peculiar; causticity of the alkaline oxides or ` alkaline earths. Quicklime exerts essentially a local action (on the skin and mucous membranes) irritating and caustic, which is naturally less marked in the case of slaked lime. Milk of lime is a feeble caustic acting only on the mucous membranes. The dilute lyes are only caustic to the skin after prolonged ac tion and especially when they are warm. -51- "In practice it is the dust of quicklime and slaked lime, given 0ef in the course of manufacture and manipulation, which gives rise to the well known lesions. This very fine dust is deposit ed readily on the mucous membranes and skin. When inhaled it may penetrate as far as the respiratory tract." Although lime has a tendency to irritate the mucous membranes of the respiratract, it is not considered particularly hazardous when breathed in small Quantities at intermittent intervals. However, complications may result when a ,'?arge amount of the dust is breathed more or less regularly. Therefore, it is to wear an approved respirator such as the MSA "Comfo" or the Willson *"Dust-tite". , -t METALLIC ZINC DUST: Metallic zinc dust (90% through 300 mesh) is an important ^nstituent in Pipe Thread Coating Compound. About 1500 pounds of this material is I0>ed per batch, and about fifty batches are made per month. The zinc dust comes in iOO pound wooden kegs or 500 pound steel drums. According to a chemical analysis, this*zino dust is 9S. 20^metallic zinc and 0. 80% zinc oxide (ZnO). The particle size distribution of a typical sample as determined by a standard screen analysis is: All through 120 mesh screen 3. 76/o retained on 200 mesh 2.04% " " 250 " - 22. 24% " " 325 " <7' & */t u jhe zinc dust is dumped from the keg or drum onto a metal sheet in front of the ket tle and shoveled into the kettle by two or three men (with an average service of | about three months) from the General Labor Department. This is a very dusty opera : tion. One sample taken during the shoveling of zinc dust had as high as 68,760,960 "particles per cubic foot of air the average concentration being 28,331,328 par| tides, less than ten microns, per cubic foot. The workmen are exposed to this dust about thirty minutes per batch or approximately 2-l/2 hours per month. They wear dust respirators. About 95% of these dust particles are dark grey, opaque, angular in appearance under the Xonimeter microscope, and about five microns or less in size; 5% appear slightly angular, crystalline, ten microns or less in size. The crystalline material is probably zinc oxide. * - What Physiological Effect is Produc ed by Zinc Dust? Although zinc oxide (ZnO) produces definite physiological effects, metallic zinc dust does not seem to affect the person breathing it other than that caused by the inhalation, of any inert dust. Nevertheless some investigators are of the opinion that zinc is not entirely inert j and harmless. Certainly it is not as hannful as lead or arsenic, but the United I States Public Health Service has certain limitations on the amount of zinc that is permitted in drinking water. According to Nuck, E. Remy, and F. Poltzmann (Jour. Indust. Hyg. , Vol. 12, 1930, page 171 Ab. ) Zinc dust cam cause lung trouble after being inhaled in large quantities. Zinc dust is also very definitely explosive. j C. - A-S3EST0S "FLOAT": Float asbestos is -used in the manufacture of tractor lubriJ cants. It comes in 150 pound cloth bags by railroad, about 2000 bags to a car. From 200 to 3000 pounds are used per batch and from two to fifteen batches a.re made per month. The bags of asbestos float are dumped into the mixing kettle by three men with an average service of twelve years. These laborers are exposed to dust about forty minutes per batch. Dust concentration as high as 8,259,440 particles, ten microns or less in size, per cubic foot are produced during the dumping of as bestos float, the average being 3,058,560 particles per cubic foot. About 9S;"2 of these particles are slightly angular, round, transparent in appearance under the Xonimeter microscope, and two microns or less in size; 2% are round, semi-c^iaque, J P J P J r f f P B B B B B B B B n t t ff -IT R i l l l I B B B H i n m i -52I 3 like, five microns or over in size, 1 | Reoent investigations have indicated that the inhalation of asbestos particles licrons or less in size is even more hazardous than was originally believed, and -in order to prevent harmful effects concentrations should be kept below five bn particles (10 microns or less) per cubic foot. The physiological effects already been discussed under "ASBESTOSIS" so need not be given any further con-atioru Men handling asbestos float should be required to wear approved respi- GROUND MICAt Ground mica (80 mesh) is used in the manufacture of axle grease, aes in 100 pound burlap bags. About fifty pounds of ground mica is used per land an average of five batches are made per month. The period, of exposure not exceed ten minutes a batch. Handling ground mica produces an average of '^120 particles ten microns or less in size, per cubic foot. About 60% of these iles are transparent irregularly shaped scale like in appearance under the Jter microscope, and five microns or less in sizej about 40# are over ten mi . in size. The transparent plates have small lines or fissures and appear to Ln small air bubbles. Although ground mica has never been considered a hazardous dust, seme recent is made among the workers in North Carolina indicate that continued exposure to quantities of ground mica over a period of years will produce a fibrosis. Howthere is very little probability of any trouble where concentrations are kept v 10,000,000 particles per cubic foot of air and where the exposure to mica dust Slh a small percentage of the employee's working time. SULPHURt Sulphur flour is used for sulphurizing cutting oils and in the Ration of special lubricants for hypoid gears. Crude'sulphur is used in the jLcture of sulphuric acid and in the treatment of gasoline and naphtha for re . of impurities such as the mercaptans. Lphur FIourt Sulphur flour comes in paper-lined wooden barrels, 100-pound oth bags, or 150-pound burlap bags. About 2500 pounds of this sulphur is mped into the melting kettle by two men with an average service of twelve "It s , once a day. 'Their exposure to the dust which results from handling _j dumping the bags, an average of 1,540,608 particles, ten microns or ss, per cubic foot, is about fifteen minutes per man per shift on an av&rre. No goggles or respirators are worn. About 90% of the dust particles [samples taken during the dumping of the sulphur flour were slightly angu.r crystalline in appearance under the Konimeter microscope, and five mi- ins or less in size; 10# were semi-opaque, rounded, and over five microns size. The larger particles appear to contain small air bubbles. There e also a number of very small specks. "About 370 pounds of flour sulphur is used per batch in the preparation hypoid gear lubricant. Two batches are made per week on an average. .e exposure to the sulphur dust is only about two hours per week on an Jrage. Since the sulphur is dumped into drums of oil being agitated by apidly revolving propeller type mixer more dust is produced than where bags are simply dumped into a kettle. Samples taken during this opera -on had as high as 6,910,080 particles, ten microns or less in size, per pic foot. The average was 3,783,552 particles per cubic foot. The dust tides had the same characteristics as those given in the preceding .ragraph. ide Sulphurt Crude sulphur comes in box cars holding about SC, 000 pounds, ually from Freeport, Texas. Towers are filled with this sulphur by four -&3- 'jb 1 with an average service of eight years. It requires about two hours to :fill a tower with about 10,000 pounds of crude sulphur. Two towers are chargfed every wee^ Consequently, the men are exposed about four hours a week to sulphur dust caused by breaking up the lumps (4,304,640 particles, ten mi'crons or less, per cubic foot) and shoveling the crude sulphur into the rower 'alerrator (an average of 3,357,640 particles per cubic foot). The amount of ^dus'k produced by this operation is somewhat reduced by the steam turned on in'8ide the elevator shaft to prevent dust explosions. About 50% of the dust :particles in samples taken while the tower was being filled were slightly angu lar crystalline in appearance under the Konimeter microscope and five microns Lor less in size; 35% were rounded semi-opaque, ten microns or over in size; and. .5% were opaque scale like, between five and twelve microns in size. ' Sulphur dust particles are explosive but otherwise are not considered hazardflUS any more than any of the other "nuisance" dusts, although they will irritate the jj^cous membranes and the eyes after slight exposure. Consequently, it is advis e e to wear rubber type goggles and approved respirators, such as the MSA Camfo typ ' In an article by Aldo Cestari (Arch, Intern. Pharmacodynamie, 1933, vol. 46, pp, 300-314) it is stated: "Intratracheal injection of sulfur suspensions brings about ex cretion of hydrogen sulfide in a period of 50 hours. There are slight exudative and infiltrative reactions in the lungs. It is supposed that a substance similar to glutathione reduces the sulfur to hydrogen sulfide. " ?l - LITHARGE: Litharge is added to the Plumbite of "Doctor" Solution to assist in the removal of mercaptans, other sulphur compounds and unsaturated hydrocarbons from asoline and naphtha. From one to five 600-pound drums of litharge are used in a batoh, depending upon the stook to be treated and the condition of the "Doctor So lution". The litharge is removed from the drum a shovel at a time, and about fifteen minutes are required to dump one batch. A batch is made once a week on an average. The average service of the men involved in this operation is seven years. They wear MSA Camfo respirators with an approved lead filter and rubber type goggles. All of the work of adding litharge is done in the open air on a platform at the tops of the solution tanks. S- - H 1 The kverage dust produoed during the dumping or shoveling of litharge into the solution tank is 3,077,480 particles, ten microns or less in size, per cubic Ifoot, although there were as high as 9,288,960 particles per cubic foot" during the operation. A rough estimation of this litharge concentration indicates the presence of from five to fifteen milligrams of lead per ten cubic meters - the amount that an average person doing moderate work would breathe in one day. This is in excess of 1.5 milligrams in'ten cubic meters which is the maximum allowable limit set by the United States Public Health Service. About 80% of these dust particles were.rounded, transparent, crystalline in appearance under the Konimeter microscope, and five mi- orons or less in size; about 15% were over ten microns and appeared to contain small air bubblesj 5% were dark opaque scale-like, from five to ten microns in size. 5 . bi- Hecessarv Precautionary Measures When Handling Litharge. Litharge is a com pound of lead, and consequently there is the possibility of lead poisoning unless a few simple precautions are observed to prevent the entrance of lead into the body by swallowing minute particles of the litharge dust, by inhaling the dust, or by absorption from the skin when handling the litharge. An effort should be made to cause as little dust-as possible. Instructions issued by the Medical Department re quire that: "1. No employee shall handle litharge until he has been examined and certified as physically qualified by the Company Doctor. "2. Employees must be sent to the Company Doctor for physical ex amination at least every six months or at the first sign of ~ ill health- " "3. Respirators - An approved type of lead dust respirator, proper ly adjusted, shall be worn when handling litharge. All respi rators shall be thoroughly cleaned with soap and warm water. "4. Clothing - Unionalls, caps or some head covering and gauntlet gloves shall be worn when handling litharge. Upon the comple tion of this operation the outer clothing must be removed and placed in a locker used for this purpose only. Unionalls should be washed at least once a week. "5. Bathing and locker facilities - A conveniently located locker and w a s h room shall be designated for use of oaployees hand ling litharge. Separate lockers should be provided for street clothes, work clothes, and one for Unionalls worn when hand ling litharge. In plants where men are handling litharge throughout the shift, only two lockers need be provided. The floors of the locker roams where the men.change their dust covered Unionalls and the benches shall be thoroughly moisten ed before being cleaned. "6. Personal cleanliness - General personal cleanliness is of first importanc e. (a) Hands must be thoroughly washed on the completion of the litharge handling operation. Hands must also be thoroughly washed before eating or placing anything in the mouth. A special effort should be made to clean the finger nails so as to remove any litharge. (b) Never eat until litharge covered clothing has been removed and the hands washed. (c) Teeth should be brushed at least twice a day and the teeth and gums kept in good condition. (d) The mouth should be rinsed thoroughly before eating. (e) Never use tobacco in any fora while working in and around litharge." The responsibility for the careful observance of ALL of these instruc tions should be placed upon the foreman. - SODA A52; Soda ash (58% NftgO) is used to form a solution for neutralizing ac oil. Thirty 200-pound cloth bags of soda ash are dumped into a tank of water per batch by six men, with an average service of five years, from the General Labor De partment; three batches a week. Men exposed to dust resulting from opening and dumping the bags of soda ash about five hours a week. Eight men spend about half a day a month unloading bags from railroad box cars. The men who do the unloading wear MSA Comfo respirators and are not the same men as those doing the mixing who d sot wear any respirators or goggles. The average dust produced by the dumping ana -55- jjixing operation is 1,003,337 particles, less than ten microns, per cubic foot of These particles are all slightly angular, crystalline in appearance under the j|F jonimeter microscope and about five microns in size. Many are transparent, glass t like. There are a number of small black specks. 'b - TALC or "SOAPSTONE"; Pulverized talc or "soapstone" is used as a filler in the. Manufacture of "hot neok" greases used in the steel mills. According to R. B. Ladoo (U.S. "Bureau of Mines Bui. No. 213, 1919) ordinary talc or soapstone is Steatite (hydrous magnesium silicate - H2Mg3 (Si0 3 )4 ). In the form of powder, the talc is greyish white. Associate Chemist Frederick Goldman of the U. S. 3ureau of Mines, who jnade a chemical analysis of samples of talc as marketed, reports: Si02.............. 46.04 per cent _ CaO............... 4.39 " " MgO............... 26. 20 " " Combined Oxides.... 15.64 " " Grease makers usually consider the composition of "soapstone" which they use as ap proximately 90$ magnesium silicate and 1C$ calcium carbonate. It comes in 90-pound paper bags, 700 bags to a box car. About 7200 pounds are used per batch and one batch is made a day on an average. The "soapstone" is dumped into the mixing kettle by two men with an average service of ten years. This dumping which requires about an hour per batch is a rather dusty operation. One sample taken at face level just after a bag had been dumped had as high as 22,995,840 particles, ten microns orless in size, per cubic foot of air. The average dust produced was 13,064,960 dust par ticles per cubic foot. About 98$ of these dust particles were transparent, crystal line, irregularly shaped plates and rods, in appearance under the Konimeter microsoope. Most of these particles (about 98$) were five microns or less in size, the remainder being ten microns or over; about 2$ were scale-like, semi-opaque, five mi crons or less in size. ]' .Physiological Effects Produced By Talc Dusts. About two years ago Dr. W. C. Dreessen, Passed Assistant Surgeon, and J. M. Dalla Valle, Assistant Sanitary Engi-; near, United States Public Health Service, made a study to ascertain whether there is a connection between talc dust exposure and the relatively high tuberculosis death rate in Murray County, Georgia, where two talc mills and mines are located. They found (Reprint No. 1669 from the Public Health Reports Vol. 50, No. 5, Feb. 1, 1935, pages 131-143)t J ? jI "Physical and roentgenologic examinations were made of 66 men and women who were exposed or had been exposed to talc dust. In the higher dust groups comprising 33 men, 8 were found to have Pneumo coniosis I and 8 to have Pneumoconiosis II or III. Six of the thirteen examined were diagnosed as having Pneumoconiosis I. No advanced stages of the disease were found in this group. In the group exposed to low concentrations of dust, no Pneumoconiosis was found." The final conclusion of this study was that although Georgia talc appears to be "more injurious than tramolite talc" the high tuberculosis mortality rate in the County "could not be attributed to the t?.lc industry". Investigators have suggested, however, that for more or less continuous expo_ sures concentrations of talc or "soapstone" dust should not exceed 15,000,000 par I tides, ten microns or less in size, per cubic foot of air. - GRAPHITE: Powdered graphite (80$ to 85$ graphitic carbon and 15$ probably magnesium silicate) is used in the manufacture of spring and pressure lubricants. li r > f f f f f $ f f f f f f f f f f f f f f B B a B i t t r t r ft B - B -56- 'jcsnes in metal drums or 100-pound paper lined bags. About 3700 pounds of powdered Lj-aphite is used per batch and one batch is made per day on an average. The ,-raphite is dumped into the mixing kettle by men with an average service of seven ears. This operation requires about forty minutes per batch per man on an average, jiree men are usually engaged in this dumping. They wear respirators while hand ling and dumping graphite, which is not a particularly dusty operation. The average ust produced is 1,803,080 particles, ten microns or less, per cubic foot of air. 'ill of these dust particles are rounded or slightly angular, black opaque, amorphous, jooty or dark grey in appearance under the Konimeter microscope, and three microns p less in size. t!j - SLATE FLOUR: Slate flour (300 mesh) gives rigidity to asphalt on "fast sur- jfaces" such as steep roofs and pipe lines, and prevents its running off. It also jroduces desirable weathering properties. Mixtures as low as 107 slate flour and fjs high as 40$ are used. An average of two tons of slate flour is used to each 'still which averages about 800 barrels of steam reduced asphalt. Since the slate 'flour is introduced by the use of closed pipe lines and centrifugal pumps, the only ljust produced is that which results during the unloading of the sacks and dumping 'them Into the hopper. The slate flour comes in 50-pound paper bags, 750 bags to a railroad box car. Four men with an average servioe of about a year, open the bags ind dump the slate flour directly into a hopper from which it is siphoned by cam- J pressed air to a storage tank holding about 15 tons. About four carloads a month ire received and an average of about 5-l/2 hours is required to unload each car. dibout one and three-quarter million pounds were dumped during the last quarter ^period. The men wear MSA Camfo respirators. A screen analysis of this slate flour 'showed that 99.7% passed through a 200 mesh screen and 96.8$ through a 325 mesh soreen. Due to the fineness of slate flour and its low bulk density (1.04) con siderable dust, an average of 12,007,680 particles, ten microns or less in size, iper cubic foot of air, and counts as high as 16,538,880 particles per cubic foot, lire produced during dumping the sacks and filling the storage tank. About 98% of ]these dust particles are slightly angular, transparent, crystalline in appearance under the Konimeter microsoope, and five microns or less in size; 2% are semi-opaque, slightly angular. There were a few plate like particles which appeared to contain -jsstall air bubbles, and a large number of small black particles. ` . A petrographic examination made of a slate flour sample at the United States i3ureau cf Mines Experiment Station in Pittsburgh, Pennsylvania showed that it con- stained more t^Jan 1% Quartz (Si02 )* 30$ Sericite (K2O-3AI2O3-6 Si02-2%0), 40% 'opaque and 3C$ five different unidentified constituents. A chemical analysis of slate granules and flour (Jour. Indust.Hyg. V 0I.XV. ,No. 2,Mar. 1933,p. 67) reports these constituents: c I Silicon Dioxide ........ 59. 27$ Magnesium Oxide... Titanium Dioxide. ....... 0. 99$ Potassium Oxide... C Aluminum Oxide... ...... 18. 81$ Ferric Oxide.... ...... 1 .1 2 $ Sodium Oxide..... Water below 110C. .... 0. 32$ I Ferrous 0x3.de ... ...... 6.58$ " above " . I Managanous Oxide. ...... 0.13$ Phosphoric Oxide.. I Calcium Oxide.... ...... 0.42$ Carbon Dioxide.... .... 0.2 1 $ ! Barium Oxide.... 0 05/e Ferric Sulphide. .. .... 0.15$ Specific Gravity - 2. 795 J "The silicon found, though expressed in the chemical analysis as silicon dioxide, is net differentiated chemically as to the forms present in the original minerals, whether free silica or silicate. " -5 7 - _ Effect of Slate Flour on The Lungs - In his' paper "Effects of Certain Silicate Dusts in the Lungs" read before the Industrial Hygiene Section of the American Public gealth Association at Washington, D. C, on October 27, 1932, Dr. Waldemar C. Dreessen j)f the United States Public Health Service, reporting the results of his studies of workers exposed to slate dust, wrote: I * "Of the 48 cases of pneumoconiosis observed, all were in the first t stage except 5 cases. In general, the pneumoconiosis observed in * the early or first stage cases resembled that induced by cement 1 dust. The bronchial striations, however, were somewhat more promi nent. There was always a moderate bilateral increase in the size and density of the hilar shadows with accentuations of bronchial striations which extended well out into each lung field. The linear striations seemed "softer" in appearance and lacked some of x the sharpness of detail which is usually observed in the X-rays of individuals who have inhaled silica dust. This diffuse, fine generalized fibrosis was chiefly confined to the lower two-thirds of the lung fields. "In the second stage an increased prominence of the above mention- i ed characteristics was present with the appearance of flake like, f. dappled areas of increased density in both lung fields. In the i- third stage these dappled areas seemed to conglomerate, and in this manner gave way to massive, clouded areas of increased density." Dr. Dreessen found that although the silicate dusts of slate "induce a fine diffuse, bilateral fibrosis of the lungs which is definitely demonstrable in the X-ray" "workers exposed to slate dust do not begin to show definite first stage pneumoconio sis until after more than ten years exposure. He-did not find any evidence that the resultant pneumoconiosis had led to disability. i K - GRINDING PERRIS ROOT: Derris root is used in the manufacture of insecticides. It comes in 500--pound bales from the Dutch East Indies. In order to reduce dust, the bales are thoroughly wetted with white oil. The root is ground at the rate of 500 pounds an hour to pass through a 3/8"-screen, One man with three years* service is exposed to an average dust concentration of 1,604,800 particles, ten microns or less, per cubic foot of air. About S0% of these dust particles are rather round, crystalline in appearance under the Konimeter microscope, and about five microns in size; 20% are sharply angular, five microns or less in size. The particles ap pear to bemore inorganio than organic in character. Evidently the lighter root dust particles are either larger than 30 microns and were, therefore, filtered out by the Konimeter filter or were carried out by the exhaust ventilation, thus leaving the dirt or soil which had adhered to the roots. The grinder is located in a small room well ventilated by means of a 30-inch motor-driven fan. This explains the low dust concentration in the samples taken during the grinding operation. The operator wears rubber gloves, cover-alls, and is provided with a fresh air hose type of mask while grinding. * . To What Extent is Derris Toxic? According to recent studies by the United States Department of Agriculture (indust, i Eng. Chem. Vol. 28, No. 7, July 1936, pps. 815-821) Derris is a possible health hazard to those engaged in milling, grind ing, and diluting it (Derris) without the use of suitable protective measures. Pharmacological studies show that Derris and its water extracts affect the respira- .tory center which is initially stimulated and then, after fatal doses, completely depressed, with death resulting. Derris dust when applied to the armpits 'was also found to provoke a "mild evanescent irritation." ' I II - GRINDING PYRZTHRUM FLOWERS: Pyrethrum flowers are an important source of cne ff IF Sf WW ff -58- rtn r a hn n _ ^ th e e s s e n t i a l in g r e d ie n t s o f i n s e c t i c i d e s . They come from Japan in mat covered s r ie s w e ig h in g about 4 5 0 pounds. On an a v e r a g e , about t e n b a l e s a r e ground per ^ b if t . Opening th e b a le s o f com pressed flo w ers i s th e d u s t ie s t p a rt o f th e opera t i o n , producing on an average 2 ,0 3 9 ,0 4 0 p a r t ic le s , ten m icrons or l e s s , per cubic ffocrt' a ^r * About 8 5 $ o f t h e s e p a r t i c l e s a r e a n g u la r , c r y s t a l l i n e i n ap p earan ce er th e K onim eter m ic r o sc o p e , and th r e e m icrons or l e s s in s i z e ; ab ou t 15$ are &t round p a r t i c l e s and d i s c s and s h r e d s , t e n m icron s or l e s s . The c r y s t a l l i n e ^^Cpearing d u st p rob ab ly o r ig in a t e s from th e s o i l which has blow n on th e flo w er s or - p la n t s . One mri i s e x p o se d p er s h i f t f o r ab ou t fo u r h ou rs a day d u r in g a n in e month " ;e r i 0d. He w ears a W i ll s o n d u s t r e s p i r a t o r . The g r in d e r i s e n c lo s e d i n a m eta l ousing connected by a fo u rteen -in ch duct to a six te e n -in c h m otor d riven exhaust fan. Pyrethrum d u st O thers in the le a st; ^ome in d iv id u a ls to j in pyrethrum d u st. seems t o i r r i t a t e th e sk in o f some in d iv id u a ls as a m atter o f fa c t i t causes an a lle r g ic ty p e such an exten t th a t i t is in a d v isa b le fo r such and not a f f e c t o f reaction in p erson s t o work ,, MIXING AND PACKING "FLIT" POWDER; " F lit " powder i s a m ix t u r e o f p u lv e r iz e d * d o r r is r o o t, pyrethrum flo w e r s and o th e r in g r e d ie n t s . I t i s m ixed i n a s p e c i a l ^oom p r o v id e d w ith e x h a u s t v e n t i l a t i o n b y a man w e a r in g a r e s p i r a t o r . The d u s t i e s t -fpart o f t h is o p e r a tio n i s s i f t i n g th e p u lv e r iz e d d e r r is and pyrethrum which produces |a n average o f 8 ,7 2 2 ,5 6 0 p a r t ic le s , te n m icrons or le s s , per cubic fo o t o f a ir . JAbout 95$ of these dust particles are angular, crystalline in appearance under the ?Xonimeter microscope, and about three microns in size; about 5$ are less crystalline ^and more opaque, five microns or less in size. & F i l l i n g Cans; T h ree-q u a rter and two and o n e-q u a rter ounce t i n cans a re f i l l ed by a u to m a tic m a ch in es, t h e f i l l e r ends o f w hich a r e e n c lo s e d i n a m e ta l h o u sin g w ith a fou r-in ch exhaust duct to a fou rteen -in ch m otor-driven fan. That th is ex h au st arrangem ent i s f a i r l y e f f e c t i v e i s shown by an a verage d u st c o n c e n tr a t io n in ^sam ples tak en a t fa c e l e v e l o f th e operator during t h e ' f i l l i n g op era tio n of 3^1,755,840 p a r t ic le s , t e n m icrons or l e s s , per cu b ic fo o t o f a ir . The g i r l a t th e ^ S ealer wears a bag-type dust resp ira to r. . $ VIII - C L E A N I N G T U B E S A N D D R U M S C O N T E N T S --t c S C lea n in g -tubes and drums o f b o i le r s and p r o c e ss equipm ent i s a r o u tin e opera t i o n w hich produces c o n sid e r a b le d u st b elo n g in g more to th e " n u isan ce" c la s s th an t o c . th e fib r o s is ca u sa tio n group. N ev erth eless, co n sid era tio n should be given to k eeping; 5 -su ch d u s down t o a minimum o f n o t more th a n 1 0 , 0 00 ,00 0 p a r t i c l e s p e r c u b ic f o o t due c .v t o t h e number o f men engaged i n t h i s work and t h e i r m ore or l e s s c o n tin u o u s e x - 1 posure I. c I . - CRACKING COIL SOAKING DRUMS; C rack in g c o i l s o a k in g drums " coke-u p" a b o u t t f : once a month, so t h a t in many c a se s th e y a re a lm ost c o m p le te ly f i l l e d w ith th e ex t ' c e p t i o n o f an o p e n in g down th r o u g h t h e c e n t e r no g r e a t e r th a n t w e lv e in c h e s i n diam - ; e t e r . A t m ost p l a n t s , t h i s cok e i s rem oved b y a s p e c i a l m ach in e; a t -the o t h e r s , men c w it h an a v e r a g e s e r v i c e o f t e n y e a r s a r e r e g u la r ly engaged i n c le a n i n g t h e s e drums by -: mOneeanms ano f waorkc os nicnrseitde e b aunsdt e rtw oty poeu tos ifd ep naeut mtahteic t ocph ims ealn,hosltea. r t iTnhge taetmtpheer attoupr e oifn st hi dee dtrhume . t drum i s ab ou t 90 d e g r e e s F a h r e n h e it. E ach man works h a l f an h o u r i n s i d e and i s th e n r e l i e v e d f o r ab ou t an h o u r. On an a v e r a g e , each man works a b o u t two and a h a l f hours 1 per s h i f t , two s h i f t s a week. A "boatsw ain" ch a ir i s used t o g e t in and out o f th e drum. They wear " h a rd b o iled " h a ts and l i f e - b e l t s . E x c e lle n t v e n t i l a t i o n i s p ro v id ed c by a steam or an a ir syohon o la ced in th e bottom m anhole o f th e drum, as a r e s u lt o f t w hich sam ples ta k e n a t fa c e l e v e l o f men d u rin g th e o p e r a tio n c f th e pneum atic c h i s e l had an average o f o n ly 3 1 1 ,5 2 0 dust p a r t ic le s , te n m icrons cr l e s s , per cu b ic fo o t o f a i r . .About 6 0 $ o f t h e s e p a r t i c l e s w ere s h a r p ly a n g u la r , c r y s t a l l i n e in ap p earan ce * konimeter microscope, and about five microns or less in size) 35# were ! ^ u n d "semi-opaque, crystalline, about ten microns or over; and about 5% were small r ck'particles. There were also a few black scale-like particles over ten microns ^^size. The major portion of this dust is probably coke or carbon and the scale I *ike particles are, no doubt, metal from the sides of the drum or from the chisel. I fjf. II. - CRACKING COIL TUBES; There are 183 tubes in a high pressure cracking 1 ^ unit. After running from twenty to twenty-five days, depending upon the char.~cc^.er Qf -the stock being run, the temperature and pressure, the petroleum coke which deposited on the tubes must be removed. Liberty air-driven tube cleaners with '^c0ne and star cutters operated by men with an average service of six years are used -for this purpose. The men work in gangs of six to eight and are exposed to dust ^ftbout six hours every two shifts on an average. They wear neither goggles nor respi- ?rators although a dust samole taken immediately after reversing the cleaning 'machine while 'less in size, in a tube contained as per cubic foot. About high as 9,062,400 particles, ten micronsor 50% of these dust particles are black, opaque 'in appearance under the Konimeter microscope, and two microns or less in size; 40# |"are angular, transparent, plate-like, ten microns or larger; and 30%, are angular, {'transparent crystalline, five microns or less in size, i A' ' ! -f Samples taken on the Cleaning Platform while cleaning Cracking Coil Furnace Itubes at a Northern refinery had an average of 113,280 particlesper cubic foot. Ninety-eight per cent, of these dust particles were rounded crystalline in appearance -.under the microscope and five microns or less in size. Samples taken in the passage -way back of the furnace while tubes were being cleaned had as high as 1,076,160 ^particles, ten microns or less in size, per cubic foot of air. This indicates that the men in the passageway, back of the furnace are exposed to more dust than those "'on the cleaning platform. . 2 III. - WATER HEADERS AND BOILER TUBES; Tubes and headers are cleaned twice a year by means of air-driven turbines. It has been found that cleaning can be done more effectively if done dry rather than wet because the dust can be blown out. If .water were used, the loosened material would soon form a paste which-would be smear- - ed back on the tubes by the action of the cleaning turbine. Regardless of the dust ] which is produced in concentrations as high as 30,359,040 particles, ten microns or less in size per cubic foot of air, workmen prefer working in dry drums rather than in wet ones. Eight men (two on each turbine) are engaged in this cleaning operation .which requires about twelve days a year. Men with an average service of fifteen years :are assigned to this job from the Labor Department. The temperature inside of the ' .drums or headers is about 70 degrees Pbhrenheit. In accordance with the usual prac tice, men operating the turbines, inside the drum or header, work about ten minutes and are relieved for ten minutes by their co-workers who assist in handling the air .^hose in and out of the drum manhole. Respirators have been provided in most cases .but sire not always worn. The average dust produced while cleaning water-headers and boiler tubes in samples taken from; Lower Platform, Front Water Header................ 18,306,048 part, per cu. ft. j In t%Z Drum While Cleaning Water Wall and Tubes,... 5,664,000 n " " $ Inside Manhole Drum #3 While Being Cleaned........ 28,320,000 " " n ` % About 40? of the dust particles in the samples taken on the lower front water-header platform, while header was being cleaned, were rounded, dark red in appearance under the Konimeter microscope, and about two microns in size; 50# were opaque, more or less angular, and about five microns in size; 10# were crystalline, slightly angular, and over ten microns in size. About 65# of the particles in the sample taken inside 2 drum during cleaning were black, opaque, angular, less than two microns in size; ' and about 15# were round, more or less opaque, over ten microns. The concentration . of dust INSIDE the drum during cleaning appears to decrease with the distance from ; 1 ' -60 a a as n n v * a a - s a B B B B B B D B $ - . S S S 3 3 0 manhole as is demonstrated by these counts in samples from Drum jfZ (Riley 3oil- ?)* Location Particles per cu. ft. ! Inside..Manhole.......................... ....................... About 8 ft. Inside Drum.......................... 1 j * n n n r n 18 " " ! n 24 " " " .......................... ............. " ............................................................................ 19,257,600 1,585,920 1,132,800 be dust particles from inside the drum appear black, angular and were less than two icrons in size. The dust from these cleaning operations are supposed to be largely be results of metal corrosion and sediment (largely Calcium Carbonate and Calcium bosphate) deposited by the treated Boiler Feed Water. A petrographic examination :f a sample of dust from the Front Water Wall Header was made by the United States ureau of Mines Experiment Station at Pittsburgh, Pennsylvania, who reported: Quartz (Si02)......................... Opaque o? Coated with Opaque Material.. Unidentified Clay-like................ 1 per cent. 90 " " 9" " I According to a chemical analysis of this same material made by a regular re finery chemist using the method of Adolph Knopf, U. S. Public Health Service, the dust jontained: Free'Silica.................... ....... 0,70 per cent. Combined Silica....................... 41.01 " " ^ Although the analysis of the dust shows a low free silica content, the high dust concentrations found and the possibility that at times such concentrations may Ibe higher than those gardless of the kind found, demonstrate the of dust encountered. desirability of wearing respirators re ] IX - FOUNDRY OPERATIONS During recent years considerable attention has been focused upon the health of foundry workers by the operation of the so-callod "Silicosis Racket" which has ex tracted large sums of money from the Foundry Industry. It is difficult to isolate -Jthis type of work which gives rise to a very general exposure to dust which may in volve all workers employed in the foundry. In many cases the worker is in sxich close 1contact with the duty atmosphere as to cause serious exposure. Much progress has been made in reducing the dustiness of our foundry operations and plans are now being considered which will further safeguard our foundry workers. The following is a ibrief outline of foundry dust producing operations: A, - POURING MOLTEN METAL INTO SAND MOULDS - About 19-1/2 tons of metal are poured per "heat". Thirty-five men with an average service of twelve years spend | about one and a half hours pouring and six and a half hours moulding per day, five j days a week. Goggles, asbestos leggings and congress-type shoes are worn by the men .handling the molten metal. About 60# of the moulding sand, which is the principal ' source of dust, is free silica (Si02).` During the pouring operation the foundry air appears to be full of dust and smoke, however, samples taken during this work aver| aged only 396,480 particles ten microns or less in size per cubic foot of air. Praci tically all of these dust particles appeared angular, crystalline under ohe Honimeter ; aicroscope and were about two microns or less in size. ! A sample of dust from the too of the crane rail over the moulding floor was ] * * 9 I P * i -6 1 - 1 a aetrographic examination by the U. S. Bureau of Mines Experiment Station in Lotsburgh, Pennsylvania who reported 50% quartz (Si02)j 15% Clay Mineral not ccaaletely identified. Kaolinite is A12C3.2 SiO 2. 2H2O; 5% Calcite (Ca C03 ) and Z0% I Igue, B. - "SHAKING OUT" CASTINGS - After pouring, the castings are allowed to , then'the moulds are liberally sprinkled with water from a hose. The bands or Ups are removed and the flask is thrown over and broken open. The rough castings re pulled out, piled up and trucked to the Cleaning Room. "Shaking Out" is con:idered one of the serious occupational disease hazards encountered in industry and ; '9 dustiest operation in founderies but due to the thorough wetting and careful n-iidling by the men, samples taken during the operation had an average of only 558,230 dust particles ten microns or less per cubic foot of air. The impinger '-hod would no doubt reveal much higher counts. About 98% of the dust particles e slightly singular crystalline in appearance under the Kanimeter microscope and vere one micron or less in size. "Shaking Out" is rather hot work, the men per spire freely so that it would be difficult to enforce the wearing of goggles and res1 rators. Twelve men with an average service of eight years work on this job, eight nours per shift, five shifts per week. J After the castings have been removed the moulding sand is again wetted and Aoroughly worked over with a motor-driven sand cutter which is a series of revolv ing blades, similar to those on a lawn mower, operated by an electric motor, mounted ia rubber-tired four-wheeled carriage which moves back and forth over the moulding oor. Moisture tests are made and viien these tests indicate 4.6 to 5.6 moisture e sand is considered ready for the moulders. During the operation of this sand cut ter, the operator is exposed to an average dust concentration of 1,529,280 particles len microns or less per cubic foot. These particleg were less than two microns and Jere slightly angular crystalline in appearance under the Xonimeter microscope. 1 C. - CLEANING CASTINGS - Various methods are used to clean castings depend ing on their size end shape. All of these methods produce more or less dust same of which can be taken care of by exhaust ventilations, others cannot. The methods most -jommonly employed are? (a) Preliminary Cleaning - Castings are brought from the moulding floor during the night and deposited in the Cleaning Room. The following morning the cores are Tcnocked out, the sprues and gates are broken off and same scratch cleaning is done, -this work produces considerable dust especially when the s"and and cOLd cores are , shovelled through the grating into the car or bucket below (3,455,040 particles ten biicrons or less per cubic foot of air). Under the Kanimeter microscope about 70% of }the dust particles appear angular, crystalline, three microns or less in size; 20% were rounded crystalline, five microns in size and about 5% were scale-like semi- ,opaque with a reddish-brown tinge and over ten microns in size. Pulmosan Respirators jhave been provided but are not always worn by men doing this work. NO attempt has . Jbeen made to control dust from preliminary cleaning although some study has been given to the provision of a special air-tight room with a grating floor and a hopper (underneath with a screw conveyer at the bottom to convey the debris to the disposal Icar or bucket and thus eliminate the dust-producing shovelling and handling. Under this plan exhaust ducts with a series of outlets around the top of the hopper carry off the dust. Air is also introduced -into the room about a man's breathing level and the amount of air taken out is greater than that introduced so that a negative pres sure is maintained and a complete air change is made about every three minutes. ("b) Tumblast - The Tumblast is a machine which combines tumbling with air blast ing. From 400 to 1500 pounds of castings are put into a drum which revolves about 10 RRT. They run from about 20 minutes to four hours, depending upon the type of castings and cleanliness required. While the castings are being tumbled they receive it e S ff ff B-B-B-B-B-B-B-B-B- B-B-B-B-fl B 0 -62i d] jst of tt20 Steel shot through three 5/l6 inch nozzles under an air pressure of t junds per square inch. This machine is operated hy three men, with an average rvice of eight years, for a period of two and a half hours per man per day, five /?- ia week. Pulmosan Dust respirators are provided hut are not always worn. A a- jnch exhaust pipe has been installed at the top of the machine and a six-inch 3.ust pine over the screen. The suction on these exhaust pipes is said to be e<out 2-l/2 inches water. Samples taken during the operation of this machine averI1,200,760 dust particles, ten microns or less in size, per cubic foot which inCi..les that the dust control measures which have been provided are getting results though there is still room for improvement. About 98$ of the dust particles ap a ]quartz-like under the Xonimeter microscope; about 60$ are five microns or less .ze and are angular crystalline in appearance; 40$ are ten microns or over in ze, and rather rounded, in appearance. There are also a large number of minute black t-llio specks entirely too small and numerous to count accurately. (c) Sly Tumbling Mill - Cleans brass castings by a combination of tumbling and r-blasting with 3 Sand Blast Sand and 85 pounds per square inch air pressure. The 1 Iholds from 100 to 150C pounds of castings and cleans five loads a day. Two men , t I an average service of 15 years, operate this mill which runs abcut five hours a y. They wear Pulmosan Dust respirators and roggls when opening the machine. This i" is hooded with an Si-inch exhaust pipe having a 2-inch water suction, also a nch exhaust pipe over the sand screen at the rear of the machine. Samples of .st taken during the operation of the Sly Tumbling Mill had as high as 2,492,160 rfsicles ten microns or less in size per cubic foot of air and an average of 5)3,344 particles per cubic foot. About 90$ of these dust particles were rounded . ystalline in appearance under the Konimeter microscope and two microns or less in ze; 5$ were black, opaque scale-like and 5$ were rounded crystalline about five .< rons in size. _ (d) Tumbling Barrels - 36" x 42" Whiting Tumbling Barrels remove sand from cast . They hold from 1200 to 1500 pounds of castings per load and revolve at 10 RPK. castings are tumbled about two hours with about 700 pounds of one-inch unannealcast malleable iron stars and jacks. An exhaust system with a 6-inch pipe through e trunnion having a suction of 1-1/4 inches water. This suction has been found in cuate to give the desired results consequently the suction is to he increased to Eches water. Samples taken during the operation of the Tumbling Barrels had an erage of 1,348,032 dust particles ten microns or less in size per cubic foot of 71 About 90$ of these particles were angular crystalline in appearance under the ijimeter Micrcn^zope and three microns or less in size; about 10$ were rounded ssmiystalline, ten microns in size. There were also a few triangular-shaped opaque *allic particles. Three men, with an average service of twelve years, operate se tumbling barrels eight hours a shift, five shifts a week. Pulmosan Dust Proof spirators and goggles have been provided but are not always worn. j The type of Tumbling Barrels being used has been condemned by a major com- Jy because it is impossible to ventilate it properly. The holes in the end liners og up when the barrel starts revolving, thus preventing circulation of air through j barrel. This condition has been remedied, in a new design now on the market, by } use of two shells - an inner perforated and an outer solid shell. 3oth trun- ons are hollow and are connected with the air chamber between the two shells. Air 'her pressure is introduced through one trunnion and exhausted through the other; ! (e) Air-Blasting - Castings which cannot be tumbled due to their size and fra- tr lity are cleaned by air-blasting (85 pounds per square inch) with mixture of ap- knnately half and half sand and -- 40 Steel C-rit. Syracuse Core sand is used when at ipecial finish is desired. There are three men, with an average service of three ars, on this job who work 45 minutes of every hour, eight hours a shift, for one ik out of three weeks, This work is done in a special tight air conditioned room -u-u-u -63- j. wearing a Sly Sand-blast Helmet supplied with outside fresh air provided by a st ;ial blower used for that purpose only. Samples taken inside the room while a casting was being air-blasted had an average of 3,738,240 dust particles ten microns 01 less per cubic foot of air. About 80^5 of these dust particles were sharply angul Icrvstalline in appearance under the Konimeter microscope and three microns or ^ess in size} 20^ were rounded quartz-like crystals about ten microns in size. There wpre also a few rust-like scales and a large number of black metallic particles too ute and too numeroxts to be counted accurately. The silicosis hazard of this opera tion could be greatly reduced by the use of steel abrasives exclusively. 1 (f) Rough Snagging Wheels - These machines are used for removing projections s- h as sprues, parts and gates from castings. There are two types of these wheels: the DOUBLE END using either 19-l/2" x 3" Carborundum and Vitrified or 24" x 2-1/2" 3.-Jjnanol (Bakelite bound) Wheels; and the HORIZONTAL DISC Grinder having a 50" d: meter vitrified wheel. These wheels are used by seven men having an average service of nine hours per shift, five shifts per week. Each wheel is hooded and has a four-inch suction pipe. There is an eight-inch suction pipe on the Horizontal G: inder. Goggles and respirators are provided but the latter are not always worn w_lh the exception of the men on the Horizontal Grinders. Vitrified wheels, are run at a slower speed (1800 RPM) than the Bakelite Bound Wheels which operate at 3400 Samples taken during the operation of the Rough Shagging Wheels had the fol- 1 fiing dust concentrations. Double End Snagging Wheels: EJ average Dust from Vitrified Wheels..... ti n " Carborundum " ..... " Bakelite Bound Wheels. 3,653,280 particles per cubic foot 3,322,820 " " "' " 2, 663-, 080 '' " " " Horizontal Diso Grinder; ^.verage Dust from 50" Vitrified Wheel....... 2,124,000 particles per cubic foot The average dust produced by all the Rough Snagging Wheels was 2,322,820 particles, t p microns or less in size, per cubic foot of air. About 80/5 cf the dust particles from the vitrified wheels appeared black angu I jr opaque under the Konimeter microscope and two microns or less in size; 20/5 an- ~ g lor crystalline -about one micron or less. There were also a large number of black minute particles, too small and numerous to count. The dust particles from the Horir"ptal (Vitrified) wheel were approximately 90% angular, crystalline and 10/5 black < aque. All of these particles were about two microns or less in size. About 6055 oi the dust particles from the Bakelite bound wheel were black angular two microns or less in size; Z5% were angular crystalline, less than one micron in size and abort ] f were 'rounded crystalline about five microns in size. J (g) Fine Snagging and Polishing Wheels - These wheels grind off small projec- 1 'jons and remove rust from stock which has been in storage. There sure three types: .JUBLE 4" x 14" POLISHING EMERY WHEELS - Wheels after being made up are dipped in glue and then rolled in Alundum Grinding Grain, sizes 60, 80 and 120 mesh. DOUBLE "|SC GRINDERS - 36" discs covered with y46 Cast Iran Grain or Silicon Carbide (an feetrie furnace product) and WIRE SCRATCH BRUSHES -- made up with four 12" sections, exhaust hoods with a suction of from three to five inches water, have been installed on the Polishing Wheels and Disc Grinders. There is NO hood on the Wire Scratch pushes. These wheels are used by four men with an average service of two years. They ..ear goggles and gloves but no respirators. Samples taken at face level during the operation of this equipment had the following average dust concentrations: 1 ( (T 1 1 ff I a d a a a a tf m b tr n a Q.Q u u a u u--4i I -64- 1st Produced by 36" Disc Grinder........... 1,416,000 particles per cubic foot | " " 12" Wire Scratch Brush..... 736,320 " `" " " " " " 4" x 14" Polishing Wheels.. 481,440 " " " " e comparatively low dust counts indicate that the dust control measures which yjk been provided are either effective or the dust particles produced are over 30 crons in size and were thus filtered out by the Konimeter filter. Under the ni- 'cope dust particles from the Polishing Wheels appeared all round crystalline and bv_.lt one micron in size. About 40$ of the dust particles produced by the Double j,sc Grinder were sharply angular, opaque about three microns or less in size; 60$ \ less angular crystalline about one micron in size. The dust particles produced ^ ;he Wire Scratch Brush were all rounded, crystalline and about one micron in size. iere were no metallic particles in any of the samples examined. Few exhaust hoods been installed on Wire Scratch Brushes because it has been generally assumed in j these brushes did not produce any dust. This assumption, however, is untrue as ae sample from a wire brush at a Southern Refinery had as high as 6,683,520 pan icles ten microns or less per cubic foot of air. ' I (h) Cone Grinding Wheels - These wheels are- operated with compressed air and re used to do miscellaneous grinding on castings by four men, with an average serii | of twelve years, about two hours a day on an average. The cones are 5-l/4" x j4" vitrified and produce an average dust of 1,869,120 particles ten microns or ass per cubic foot of air. About 80$ of these particles are sharp angular crystaliH#. In appearance under the Konimeter microscope they are five microns or- less in iS; 20$ are round opaque but non-metallic in appearance and five microns or over iTize. . There are no hoods over these wheels and the operators wear no respirators. ' Average Dustiness of Cleaning Room Air - A series of five samples were l.m between 9:30 and 9:40 A.M. to determine the average amount of dust in the air ' the cleaning room while the various cleaning operations were in full blast. An- L"|r series of five samples were taken about 3:30 P.M. in the afternoon after the >Ji had been given its regular clean-up. There was quite a difference in the amount ' dust in the air during the morning (2,166,480 particles ten microns or less per hie foot of air) and during the afternoon toward the close of the shift (338,272 . tides per cubic foot). About 95$ of the dust particles in the evening samples ra angular crystalline in appearance and about two microns in size. There were a w large semi-opaque or scale-like particles about 20 microns in size. About 98$ ''the dust particles in the morning samples were angular crystalline two mi'Shans or J in size ancf about 2$ were round, crystalline over five microns in size. j A sample of dust from top of one of the larger Exhaust Ducts in the center ihe cleaning roam was given a petrographic examination by the .S. Bureau of Mines priment Station at Pittsburgh, Pennsylvania and found to contain 40$ Quartz i02)i 20$ Clay Mineral not completely identified; 40$ opaque. 1 J), - CORE MAKING - A large number of cores are made by the Demmler Air Ope- ted Core Machine which uses a mixture of two-thirds sea sand, one-third river sand lone gallon core oil per 60 gallons sand. There are three sources of dust in the Jation of this machine: rl) Shovelling Sand to fill the Machine' Hopper..1,019,520 carbides per cubic foot f) Blowing out Core-boxes..................... 736,320 * " " " I ,3) Blowing sand into the Core-Moulds.......... 755,200 " " " tl j About 98$ of the dust particles from blowing out the core boxes are dark, -que in appearance and about one micron in size. The dust particles from blowing :d into the core moulds are angular crystalline less than one micron in size, a i I -6 5 - Cores a r e "sm oothed up" a f t e r b e in g baked in t h e c o r e oven b y s c r a tc h in g i f f th e r o u g h e d g e s w it h an. o ld hacksaw b la d e . T h is o p e r a tio n p r o d u c e s an a v e r a g e o f 06,240 d u st p a r t ic le s te n m icrons or le s s in s iz e per cu b ic fo o t o f a ir . About 98% o f th e se p a r t ic le s are an gu lar, c r y s t a llin e in appearance under th e Konim eter m ijroscope and are le s s th an one m icron in s iz e . v E. - SEPARATION OF BRASS FOUNDRY SKIMMINGS - A Steinlein Separator, revolv ing about 25 RFM, separates brass from about 100 pounds of skimmings an hour. The bparator has a 4-inch exhaust duct to a 12-inch fan which produces a suction of about four inches water. Samples taken during the operation of this machine had an > overage of 1,231,920 particles ten microns or less per cubic foot of air. About 95% | f the d u st p a r t ic le s in sam ples taken above th e charging ch u te appeared opaque [ A g u ia r b la c k in c o lo r under t h e K onim eter m icro sco p e and w ere l e s s th a n one m icron ' in s i z e . A b out 8O70 o f t h e d u st p a r t i c l e s in sa m p les from t h e t r u n n io n w ere more - y s t a l l i n e and rou n d ed i n a p p e a r a n c e and l e s s th a n one m icro n i n s i z e . T h is was ; j.so tr u e o f th e sa m p les ta k en in fr o n t o f th e m achine where t h e s l a g drops down in to . a bucket. The d u st p a r t ic le s in sam ples from th e .m e ta l b e in g d isch a rg ed from th e , - a c h in e w ere a b o u t 50% m e t a l l i c i n ap p earan ce ab ou t 50% a n g u la r c r y s t a l l i n e . B oth r y s t a l li n e and opaque jD a rticles w ere about two m icrons or l e s s in s i z e . S ix men, w ith an av era g e s e r v i c e ' o f seven y e a r s, tak e tu rn s o p eratin g t h is m achine which runs about two hours per day on an average. I X - M ASO N 'S OPERATIO NS S I. -- TEARING OUT STILL FIRE BOXES - Two men with an average service of ten ars. spend two days a month on an average tearing out slag-covered bottoms of crack ing coil furnace fire boxes. Temperature inside fire box is about 85F. The bot toms which are composed of fire brick are broken up with "Bull Point" Pneumatic lisels. Samples taken inside the fire box while this work was in progress had dust uincentrations as high as 1,019,520 particles ten microns or less per cubic foot of air. These particles were glassy sharply crystalline in appearance under the Koni- 1 Iter microscope. About 90% were five microns or less in size and 10% were over ten 1 Jcrons. The larger particles were semi-opaque. There were also a large number of round black opaque particles about one micron or less in size. After the bottoms h-jd been broken up by the pneumatic chisels they are shovelled out through the fire I lx door and then reshovelled into trucks to be hauled away. This operation natural ly produces more dust than the breaking up inside the fire box. Although no wind was blowing samples taken at face level during the shovelling and loading had dust con- c tntrations as^high as 2,435,520 particles ten microns or less per cubic foot of air aJd an average of 1,345,200. Goggles but no respirators were worn by the workmen.1 1 II. -- CHIPPING OR CUTTING CONCRETE -- A large number of employees with an 3 jerage service of three years, spend at least ten per cent, of their time dismant ling or cutting concrete structures with pneumatic chisels in the removal of old foundations, concrete supports and blocks and in cutting holes in walls and floors. : pples taken during the cutting or chipping of concrete had as high as 6,910,080 particles ten microns or less in size per cubic foot and a general average of ..591,051 particles per cubic foot. All of these dust particles are slightly angular ; Irstalline in appearance under the Konimeter microscope. About Q5% of the dust par- r* :-isles ere five microns or less in size; 10 % between five and ten microns and about '% over ten microns in size. In many ea,ses neither goggles or respirators were worn 1 |the workmen. Regardless of the rather- l,ow_dust counts found, men engaged in chip- 1 pg or cutting concrete should wear "SeSnrete-due to the high silica content in the sual aggregate used in concrete. i t III. - CHIPPING MORTAR FROM BETWEEN BRICK - Chipping Mortar with pneumatic ..isels from between bricks inwalls of structures preparatory to weather-proofing is a articularly dusty operation. Samples taken during this work had dust concentrations l t I -66 ifjtniiRniifinnnDQnDBIIBBBflilflfliniSJJJJJJJ .5 h ig h as 2 0 ,9 5 6 ,8 0 0 p a r t i c l e s t e n m icron s o r l e s s p e r c u b ic f o o t o f a i r and a -< ;era l a v e r a 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 t a l li n e in appearance under th e K onim eter m icroscop e and about s i x m i crons or l e s s in s i z e . There w ere a ls o a c o u n t le s s number o f m in u te r e d d is h -g r a y pi "Jticles. T his work was done by an o u tsid e co n tra cto r whose em ployees wore g o g g les auJ no d u s t r e s p i r a t o r s . . IV. - CRUSHING FIRE BRICK - F ir e b r ic k s a r e c ru sh ed i n a b e l t - d r i v e n W illia m s o', a M o to r -d r iv e n S t u r t e v a n t B r ic k Crusher so t h a t 80$ w i l l p a s s th r o u g h a 3/8" or a 150-mesh s c r e e n - much o f i t i s powdered d u rin g th e cru sh in g . T his m a t e r ia l i s th e n mixed w ith f i r e c la y , crushed a s b e s t o s and cem ent t o make " G an ister" w h ich i s . u se d in f je s h e e t l i n i n g s , p a c k in g s or as m ortar in b u i l d in g f i r e b o x e s o f .f u r n a c e s . Samples taken during the crushing of fire brick had dust concentrations as high as 11,554,560 particles ten microns or less in size per cubic foot and a general average o 12,562,960 particles per cubic foot. Crushing new fire briok produces about six t kes as many dust particles (4,375,733 per cubio foot) as is produced when crushing old, used fire brick (736,320 particles per cubic foot). Under the konimeter mi o pscope about 94$ of the dust particles produced by crushing new fire brick appear x rular crystalline, one.jnicron or less in size; about 5$ are opaque over ten mi crons and about 1$ are dark opaque, scale-like about five microns in size. The dust particles from crushing old used fire brick are more rounded crystalline in appearance j fl are about five microns or less in size. An analysis of Alamo Fire-clay Brick, f.ikoh is commonly used and was the new unused fire brick being crushed at the time our samples were taken, supplied by the manufacturers (Harbison-Walker Refractories C^jnpany) reports: Silica................. Alumina and Tltania..... Ferric Oxide........ . Lime....................,.. Magnesia............... Alkalies............... per cent. n tt n tt 0. 5 Tt tt tt tt t! tt Fire brick is crushed by two men assigned from the Labor Department, the aver s e service of these men is about 14 years. Two to three tons are crushed per day. 'je total length of exposure per month depends upon the demand for crushed fire brick and will vary from a general average of fifteen hours per man per month to as 1ch as twelve hours a week. Goggles and M.S. A.Comfo dust respirators are worn. V. - SHAPING FIRE BRICK ON EMERY WHEEL - Fire brick are ground to a specified shape and size on a 2" x 24" Carborundum (Grit 16, Grade 1, Bond 6C) Wheel which re- Jlves 900 RFM. This wheel is almost completely enclosed by a hood which has a 4ch duct to a 24-inch motor-driven fan operating at 1750 RFM. , but this exhaust is evidently inadequate as samples taken while rounding off the edges of a fire clay fur- rJce block had a dust concentration as high as 4,078,080 particles ten microns or ss in size per cubic foot of air. The general average was 2,001,658 particles per cubic foot. All of these dust particles were slightly angular and slightly opaque in Jpearance under the microscope and five microns or less in size. One man wearing ggles and a K.S.A. Comfo respirator, with about 15 years service, spends an average about two days a month shaping fire brick and blocks on this wheel. ' VI. VI. - DISMANTLING MASONRY - Dismantling Masonry structures such as old boiler id still settings is a very dusty operation but was not included in this dust study as there was no work of this type in progress at any of the plants at the time of our yrvey. 1 f -67- XI - W OODW ORKING OPERATIO NS Woodworking operations, as performed in connection with the refining of pe troleum products and associated activities, are used in the production of patterns, box shooks, containers, and construction or maintenance work. These woodworking operations produce more or less dust which is largely organic and although it may have some spores and have an allergic effect on some individuals, it is not consider ed harmful. Mr. D. Harrington of the U. S. Bureau of Mines advises that the U. S. De partment of Labor in a recent bulletin indicate that workers breathing wood dust are far more definitely afflicted with tuberculosis than the general run of industrial workers. In large quantities, however, wood dust belongs in the "nuisance" class and may also be an explosion hazard : A. - BOX SHOOK MAITOFACTURE - All pin? lumber used in the manufacture of box shooks is "kiln-dried" and all gum lumber is "air-dried". Men work eight hours a shift, five shifts a week. (a) Resawing - Band saws, twenty-five feet four inches in circumference, re saw four-quarter and .five-quarter lumber into 3/8-inch and l/2-inch shooks respec I tively. Samples taken during this resawing had an average dust concentration of 155,760 particles ten microns or less per cubic foot of air when sawing pine and 996,864 particles per cubic foot when sawing gum. These low counts indicate that the exhaust and dust collecting system which has been provided is functioning. This exhaust system includes hoods over each saw with 8-inch ducts to a belt driven fan n with five-- foot blades revolving 3500 RFM. About 60% of the dust particles in samples taken while resawing pine were crystalline, rather glass-like in appearance - prob J ably resin - under the Konimeter microscope and over ten microns in sizej 40? .were round with rough edges gray and opaque, five microns or less in size. About 80% of the dust particles from cutting gum lumber were round crystalline semi-opaque in ap pearance, five microns or less in size; ZO% were aver five microns in size. Gum lum ] ber is resawed only about four days a month. j (b) Ripsawing - Rip saws. 14 inches in diameter out ends from four-quarter gum lumber. An exhaust system has been provided with a hood over each saw and four ] inch metal ducts to a belt-driven fan with six-foot blades revolving 3500 RFM. Samples taken during this operation had an average dust concentration of 169,920 particles ten microns or less per cubic foot of air. All of these particles were angular crys ] talline semi-opaque, in appearance under the Konimeter microscope and about three microns in tze, ' (c) Cut-Off Sawing - Saw four-quarter lumber to make box ends. About 85% of the time gum lumber is sawed, and 15% pine lumber is sawed. Samples taken while saw ing gum lumber had an average dust concentration of 877,920 particles ten microns or J less per cubic foot of air. About 50% of these particles were round crystalline semi opaque, gray in oolor and from five to ten microns in size; 50% were slightly angu lar crystalline in appearance under the Konimeter microscope and three microns or less J in size. There were also several very small black specks. The low dust count indi cates that either the particles were mostly over 30 microns in size and were thus filtered out by the porcelain filter or that the exhaust system was effective. (d) Planing - Planers or double surfacers resurface the four-quarter and five quarter lumber to give it the proper finish. There is an exhaust hood over each ma chine with an eight-inch metal duct to a belt-driven fan with six-foot blades revolv ing 3500 RFM. Samples taken during the operation of planers or double surfacers had i a general average dust concentration of 509,760 particles ten microns or less per cubic foot of air when planing pine lumber and 415,360 particles per cubic foot when planing gum lumber. Particles of dust produced while planing pine lumber were crystalline rather round ir. appearance under the Konimeter microscope, about 75-o were ! ' i -68- L-7-e microns or less in size; 25# were larger than two microns and rather opaque. x z particles from planing gum lumber were round opaque in appearance and one mirv.n or less in size. ~| Dustiness of Shook Factory Air - A series of five samples were taken at five r Jitegic points no determine the. average dust concentration of the factory air, nese samples gave an average concentration of only 141,600 dust particles ten mir-us or less' per cubic foot of air which indicates that either the major portion of i dust is over 30 miorons in size or that the ventilation system is proving effect ive. The latter is probably the more logical explanation although the excellent ousekeeping is undoubtedly an important factor. About 98# of the dust particles in i ]factory air samples were slightly angular crystalline in appearance under the 3_imeter microscope and about five microns or less in size; 2# were round, opaque ^rk gray in color and two microns or less in size. I B. - BELT SANDERS, SAND DISCS AND SPINDLES OR CYLINDERS - This equipment is 3ed for ''squaring up" and smoothing surfaces of wooden patterns, cleaning and L'-'jLshing barrel-heading and staves and general mill work in the Carpenter Shops, i. pers are a notorious source of fine wood dusts. They are also contaminated with l appreciable amount of silica, if a sand-type of abrasive is used, consequently Lther hoods for the machines or respirators for the men engaged in operating these i. lines should be provided. We appreciate that it is rather difficult to properly ) fi a sander to prevent the fine dust being carried around by the abrasive member, irticularly disc sanders. Our attention has been called to a case where a man en-. fd in the use of sanders suffered recurring respiratory illness and ultimately ' h from pneumonia. His'attacks of illness seemed to correlate with extended >e of the sanders. j (a) 3elt Sanders - A n 8" x 28-1/2 ft. Belt Sander (Lightning Adalox Cloth x/2 - 40 X Grit Norton Abrasives) runs on an average of two hours per day and is ed by eight different men with an average service of fifteen years. Samples taken ie finishing ^=1 Pine lumber had a dust concentration as high as 15,519,360 par es ten microns or less per cubic foot of air and a general average of 3,443,712 .rticles per cubic foot. About 90# of these particles were angular crystalline in Iarance under the Konimeter microscope and five microns or less in size; 5# were five microns in size; 5# were opaque scale-like, ten microns or less in size, ere was no hood over this sander and the dust produced was thrown into the shop ^ A 6 in. x 18 ft. Belt Sanding machine (#3 Production Cloth Minnesota Mining mpany) runs on average frcm four to six hours a week and is used by four different iwith an average service of four years. This work was formerly done by hand on the with sand paper. Samples taken while finishing the outside of a barrel had .average dust concentration of 481,440 particles ten microns or less per cubic 'vfc. These particles were largely angular crystalline in appearance under the Koni- fer microscope. About 50# were five microns or less, and 50# were over five mi ons in size. ' 1 1 (b) Sand Discs or Wheels - These discs run from 40# to 60# of the time and J usually used by everybody in the shop in which they are located. Samples taken ring the operation of sand discs or wheels had the following dust oonoentrationst I ! -69- No. Siz e Abraisive (Dia. ) Us ed Work Being Done l1 ^ 1 7" #24 Sand Cleaning Paper Minn. heads Mining Co. Finished Barrels II 24" #1-1/2 Gar Squaring net Paper. Wood Minn. Min Pattern ing Co. Particles Per Cubic Foot 604,160 623,040 Characteristics of Dust Particles (Sizes and Per centages Estimated) __ Angular crystalline ' about 50$ five microns or less and 50$ larger than five microns. About :85$ angular crys talline two microns or less; 5$ quartz-like rounded about 10 mi crons in size. , III 30" #40 Grit on Bristol Board. Gardner Ma chine Co. Smoothing off Pat tern 1,925,760 About 90$ angular crys talline three microns or less; 10$ opaque angular one micron in siz e. IV 30" -Jl % i #2 Garnet Net Back. Gardner Machine Co. Squaring Wood Pat tern 3,624,960 About S8$ semi-opaque, sand-like, one micron or less, 2$ opaque 5 microns or over in size. j The sand disc in No. I was used in a well ventilated cabinet connected to a i8" motor driven fan by a 7-inch duct. The men wore goggles and "Comfo" respiraors. The sand wheels in No, II and -Jo. Ill had hoods with about 3-1/2 inches water suction connected to a 24" motor driven fan by 4-inch ducts. The men wore 1either goggles nor respirators. The wheel in No. IV had an exhaust hood with a 6nch duct connected to a 24-inch duct which in turn was connected with a 36-inch m o or driven fan. ] (c) Sand Spindles Cylinders - Sand spindles or cylinders are used on an -Average of about two hours per man per day. No hood or suction exhaust has been pro vided for this equipment. Men using it do not wear goggles or respirators although the dust particles produced are more angular in appearance than those produced by Jana discs or wheels. Samples taken during the operation of Sand Spindles or Cylinders had the fol lowing dust concentrsitionsr 1-- :-- 1 Size 1 (Dia. ) Abrasive Used Work Being Done t Particles Per Cubic Foot ; ?un 1 I #Garnet Paper Gardner Machine Co. Cutting Inside Core 3oxes 2,322,240 Characteristics of Dust Particles (Sizes and percentage Estimated) About 60$ quartz-like in appearance, ten mi crons or over in size; 40$ semi-opaque five microns or less in size. j -70- {j I Size |;ia. ) DUST PRODUCED BY SAND SPINDLES OR CYLINDERS (Concluded) Abrasive Used Work Being Done Particles Per Cubic Foot Characteristics of Dust Particles (Sizes and Percentage Estimated) " j-l/2" ! #l-l/2 Garnet Paper Minn. Mining Co. Putting Taper on Pattern. 877,920 About 90% angular crys talline two microns in size; 10% opaque five microns or less in size. I C. - MAKING WOODEN CRATES - Two types of saws are used in preparing lumber for ^Jing crates for gasoline pumps and tanks: I (a ) Band Saws - Samples taken during the operation of Band Saw had a dust [centration of 453,120 particles ten microns or less per cubic foot of air. All of tnese dust particles were'round, opaque in appearance under the Konimeter microscope 2. | three microns or less in size. (b) Railroad Saws - Samples taken during the operation of an 18" Railroad f had a dust concentration of 3,964,800 particles ten microns or less per cubic t 'of air. All of these particles were round, grayish opaque in appearance under Konimeter microscope and about five microns or less in size. There were also nu merous minute gray specks too small to count accurately. ' XII -R O C K E X C A V A T I O N 1 Rock excavation is usually a dust producing operation which is limited to con i ruction activities in the petroleum industry. The hazardousness of rock excavation depends entirely upon the nature of the rock being excavated, the length of exposure and the methods being followed. The principal sources of dust are rock drilling, 'lasting, mucking and handling of the rock. Of these, drilling probably produces the greatest amount of dust. '1 A. - DRILLING - The pneumatic rock drill operates essentially as a crushing _Jvice which scatters the rock to a powder at the point of impact. According to Theodore Hatch of the Harvard School of Public Health (K.Y. Ind. Bull. Vol. 15, No. 9 - cept. 1936) the particles of dust thus generated vary in size from one-quarter inch r larger down to sub-microscopic diameters. The dust is removed from the drill hole oy a stream of air or water or a combination of the two introduced through the hollow drill steel. In the case of jack-hammer drilling a considerable amount of rock dust fleeted from the hole falls back to be crushed further before it is removed again, ,,noting Mr. Hatch:I I ''The amount of dust produced by a rock drill is surprisingly j large - a jack-hammer, operating at the over-all rate of 100 feet of.drilling per day, actually crushes more than 200 pounds i of rock in eight hours. Cf .this, at least five per cent, is in the form of particles smaller than ten microns; hence, more than fifty grams of dust small enough to be air floated is generated per foot drilled. In terms of numbers of particles the figures ' are enormous - it has been found that a jack hammer produces as much as one billion particles cf hygienic interest during one minute of operation". -71I B. - BLASTING - It is often said that Blasting produces the greatest amount , | dust in rock-excavation. This statement is contradicted by some authorities who . !fer to the fact that the blast dislodges a great deal of dust from the rock sur faces deposited there from earlier drilling operation in addition to that actually j'""Tnerated by it. Under this condition blasting is undoubtedly followed by a higher 1st concentration than in the case when all the dust produced by drilling is cap tured and conveyed to a remote collector so that only that actually generated by the explosion escapes into the air. While it is undoubtedly true that if drilling is done dry, there will be de position of some of the dust on the surfaces of the excavation and later be raised 1 I blasting, however, dust from this source is minimised if drilling is done wet, cause the slushed out particles tend to form agglomerates, which are not so readi ly raised by the blasting operation. Also, when good practice is followed, the face i\d sides are wet down with water before blasting, and in mining work, there is a i jrrtinuous water spray that is started onto the heading before the blast takes plaoe and continued for some time after to help allay the dust and to wet down the material, so that dust raised during mucking will be at a minimum. J C. - MUCKING - The amount of dust produced by mucking and other rock-handling operations varies greatly with the nature of the operation. On open excavation it : j probably of li'ttle importance, but in confined sources as in tunnels and mines le dust concentration associated with rock handling may reach dangerous levels. g_|_ D. - DUST CONTROL - Methods for the control of dust in rock excavation as jggested by Mr. Hatch include? (a) - Wet Drilling and Wetting Down Rock Walls and Muck Piles - In general it jy be said that water is less effective against quartz-bearing rock than against jlica-free material such as lime-stone. The usefulness of water is limited when freezing temperatures are encountered and it produces objectionable working conditions Pcially for overhead drill operators and is certainly to be avoided if a pneua hazard exists. A fundamental objection to the wet method is that the dust is rot removed from the scene of operation but simply suppressed near its source where remains to be thrown into the air by a subsequent disturbance such as blasting. ] (b) - General Ventilation - The purpose of general ventilation is to dilute :he dusty air with sufficient clean air to bring the concentration down to a satis- ?toryvlevel. Two precautions are required: - 1st. - the fresh air itself must be free from dust and 2nd. - it must be properly distributed through the work ings to insure maximum mixing with the dust laden air. "j (c) - Dust Exhaust Hoods on Drills and Other Mucking Operations and Local Jurces of Dust - Effective dust control can be secured by means of a dust trap which urrounds the drill steel at the rock surface. The dust-laden air is captured as it jerges from the drill-hole by the inflow of clean air into the trap. To be effec- jve, the inlet velocities must be great enough to prevent the outward movement of He dust and sufficient velocity must be maintained at all points within the trap to revent settling and clogging. The collected dust is conveyed by the air-stream rough hose and piping to a suitable dust separator in which the air is freed from -s dust load and thus is discharged from the apparatus as clean air. Traps of eff erent designs are required with various drilling operations and special supporting ivices are necessary to hold the trap in proper alignment with the several operat- ,g positions. (NOTE: The dust trap is satisfactory under many conditions, but again ader many other conditions has not proved satisfactory. RS3) ffffffffffffffffffffffannnnnnnflnnuaniiiiBuii . The dust dispersed during mucking, as well as that arising iron rock drill-- ig, can be controlled by local exhaust ventilation and requires no elaborate ap paratus. r . | (d) - Personal Protection By Keans of Respirators and Positive - Pressure asks - An effective respirator or a positive-pressure mask supplied with an adequate Quantity of dust-free air provides the wearer with protection when it fits the face poperly and is worn continuously in dusty atmospheres. Respirators and masks have Ilegitimate place in the field of silicosis control, especially to provide pro jection against infrequent unexpected dust concentrations but cannot be recommended I-s a substitute for dust control in continuous operations.1 Jti % 1 i -'j - PART III MEASURES FOR REDUCTION OF THE DUST HAZARD HOW CAN THE DUST EAZA.ED BE REDUCED? - The quantity of dust inhaled nay be minimized"by the employment of these four methods outlined by Dr. M. Kummel in "Medi cal Record":- "X. Suppression of Dust Near It* s Origin, by the use of exhaust draught, dust traps or water. The water has the advantage of a fly-paper effect on the silica particles, but the humidity created tends to favor infection by prolonging the life of pathogenic organisms outside the body and facilitat ing their entrance into the body. "2. Admixture of Adulterant Dust with the silica which may assist in the expulsion of silica from the lungs, retard the process of the disease or prevent the development of tuberculosis. However, the introduction of an additional foreign body into the lungs is of doubtful value fraught with potential danger and should be regarded very cautiously and con servatively. "3. Proper Ventilation, in connection with other methods. "4, Masks should be an ideal preventive measure but, unfortunately, most of the masks stopping the dust also stop the respiration, thus ne cessitating their frequent removal. They should be of an approved type, 3 properly maintained, strictly supervised and their use rigidly enforced." We do not believe that the use of water would have any outstanding effects on 1raising the humidity in most of the dust producing operations in the Petroleum In- - dustry, any more than, for example, sprinkling one's lawn would have. We believe it remains to be proved beyond doubt that the humidification of air actually favors jbacteriological growth to the extent that the incidence of disease from pathogenic [organisms is raised significantly. There has been much discussion on this subject, Dut little has been proven. Theoretically, it may be admitted that these organisms live longer in a moist atmosphere than in a dry atmosphere, but it is rather hazardJous reasoning to conclude that for the reasons stated, the use of wet methods in dust Jcontrol causes an increase in disease. ri Dr. Kummel's statement that most masks (we presume he means respirators) that o^top dust alSfc stop respirations, is a little strong. There are available today respirators that adequately remove dust without creating a resistance to breathing .jin excess of 15 to 30 millimeters of water column, and the tendency of progressive jnanufactursrs of such devices is to further lower the resistance. Men during the War actually did fighting vhile wearing respiratory protective devices that had as much as 50 to 75 millimeters resistance. The resistance figures given for respira tors are measured at a rate of air flow of about three cubic feet a minute which is .equivalent to the amount of air breathed 'ey a person doing hard physical work. j Dust Respirators and Air Masks - Respirators and masks of various types have peen used since the days of the alchemists and are mentioned by Agricola, Ramazzini and others. Control of the dust hazard by means of respiratory protective equip ment is effective, provided: (l) the protective equipment is efficient, and j (2) it is worn continuously. Efficient equipment is available, but for continuous use, day after day, this method ffffffffirirffffffffflrffffn' fffVH -74- ; rontrol cannot be depended upon to provide the first line of defense; in this re it may be likened to the use of personal immunization as a primary safeguard -unst the spread of typhoid fever. Dust respirators and air masks do, however, ive a definite place in the field of dust control, especially as an emergency si jure, as a means of protection on infrequent dusty occupations and as an adjunct 0 Jther more fundamental methods of prevention. i Report's made to the National Silicosis Conference, called by the Secretary of al Jr in February (1937) to -study specific phases of the silicosis problem and pre?nt suggestions for its solution, contained many recommendations by qualified auicrities on the subject which have been successfully employed under actual operating 3: jitions. Briefly summarized measures for the control of dust and the prevention f pneumoooniosis include: j A. - DESIGN PLANT FOR DUST CONTROL - Much can be accomplished through design u -4 new buildings are contemplated or when old buildings are to be remodeled. For sstance, structural projections and ledges may be minimized to prevent the accunu- i- Lon of dust that might later be released into the atmosphere by air currents or Y puilding vibration caused by travelling cranes, vibrating machinery, and equipment oat have large reciprocating parts. The Engineering Committee recognized the fact iat our present day engineering and structural materials for factories do not per- 1 Ielimination of innumerable ledges and projections without prohibitive building iv.* roofing costs. However, building interiors should be so contructed that they may e easily cleaned by washing, hosing, vacuum cleaning or brushing. In some cases Sations ng the may be located over gratings, beneath materials and dust that fall through. which equipment is provided for re- B. - PROVIDE BUILDING VENTILATION - Natural ventilation should usually be c sidered only an adjunct in removing or reducing dust in the air. Even though it s possible to have high roofs in one-story structures which will give the greatest 3 enefit from natural ventilation, such methods cannot be relied upon to provide cam- 1 jfce protection in dusty operations. Where mechanical ventilating systems are pro- iJed, care should be taken to prevent strong drafts from open windows and doors de- . 1I troying the effectiveness of the system. Guards and shields should be placed in the 3 FJinity of hooded and partially enclosed processes to prevent such a condition, ^ C. - STORE DUSTY MATERIALS IN DUST-TIGHT BINS - Dusty materials should be ed in dust-tight bins, tanks, or enclosures, but each structure cf this type Id be provided with a breather or vent stack -- perhaps with an exhaust fan in aeJ stack -- to permit the air displaced during loading to be carried outside the 3 ailding. Basements may be used for storage purposes but should not be used for : k manufacturing operations. 3 D. - ENCLOSE MATERIAL HANDLING EQUIPMENT - Excessive dust created by mechan 3 : d material - handling equipment can usually be controlled by provision of adequate :Jsing and application of exhaust systems. Some materials can be kept in a moist 3 ondition while being handled, but when this is done, the material may dry out and be jpersed into the atmosphere as dust. 3 E. - ISOLATE DUSTY PROCESSES - Where possible, several or all dusty processes d be isolated from the rest of the plant. This sometimes permits the installation a more compact exhaust system resulting in more efficient operation and lower d ance cost. d ; F. - PROVIDE 'WET METHODS OF OPERATION Water, oil, and othe: liquids oe )d effectively: d ii -75- i 1. To suppress dust at the point of origin in such operations as j rock-drilling;" handling, pulverizing, and milling rock and ore; grinding metal on grindstones; abrasive-wheel cutting of , granite and sandstone. I j ' 2. To prevent the re-dispersion of dust that has settled on the floors, weills, and other surfaces such as in the granite indus ; try and in foundries. G. - DESIGN EQUIPMENT TO CONTROL DUST - When new machinery or other equipmen s contemplated, the manufacturer can frequently be encouraged to include dust con- rol features such as exhaust hoods as an integral part of the design and construc tion. H. - PROVIDE EXHAUST SYSTEMS - In some operations, exhaust systems may be installed to remove dust at its point of origin. In many cases several small systems are preferable to a larger system. Any mechanical ventilation system should be de- ligned to meet at least the minimum requirements of local State laws or industrial lodes, or lacking such..requirements, should be installed according to the best ac cepted practice. Dust Arresters - Provision of dust arresters will prevent hazardous dusts from being circulated into other parts of the plant or into the neighborhood. The location of dust arresters is very important, particularly if dry types of arresters are used. Provision should be made for removal of the collected dust without its escape into the area where the arrester is 1 oc at ed, - I. - ESTABLISH MAINTENANCE AND GOOD HOUSEKEEPING PROCEDURE - Good housekeeping is unquestionably the cheapest single method of controlling dust. Maintenance goes ith it hand in hand. The best equipment in the world will not control dust if st>* perintendents, foremen, and workers are careless and disorderly in their work. Eight suggestions are advanced by the Conference Committee: J 1. If dust-tight equipment is installed it should be inspected at regular and frequent intervals and all defects should be cor rected as soon as they are detected. ,,. 2. Operations should be performed in a manner that will create the minimum amount of dust. 3. Use water under pressure where possible to clean building in teriors. ' j 4. If practicable, combine water with air for cleaning purposes. All cleaning should be done, if possible outside of working J1 hours and men engaged in this operation should be provided with dust respirators. I 5. Vacuum cleaning removes dU3t without dispersing it elsewhere. 6. Brushing is particularly adaptable for cleaning buildings of the older type of construction. i JI 7. Low-pressure steam can sometimes be used to advantage. r ir r rr 8. A responsible person should be assigned the task of supervis ing maintenance and housekeeping activities. Among other things he should make tests from time to time to make sure that the dust control program is achieving the desired re sults. H r J. - PROVIDE RESPIRATORS - The Conference Committee was of the unaminous ouin- ion that'"dust elimination must be given primary consideration in solving the sili * cosis problem". Nevertheless, when known methods of elimination are not applicable Ior are ineffective, respirators should be provided as "a last resort and for oc P casional exposure only. Rotation of personnel under these conditions is advisable." The report definitely states that there will always be places where other methods P will be inapplicable and ineffective, and respirators will be required for doing the | work, also that there will be situations where respirators will be the primary :means of protecting the workmen. The scope of good use of respirators is considerjably beyond that of occasional exposure. The need of rotating personnel depends on P the type of work done and the supervision given the workmen. In some operatins, I P respirators are as much a part of the workman's equipment as his tools. Certainly, it cannot be expected that a person can wear a respirator for several hours con- P tinuously - but how many jobs are there that would require a person to keep the res pirator on continuously for an extended period of time. The common practice in the I majority of industrial occupations is that the person is intermittently exposed and u jis afforded many'opportunities for the periodic removal of the respiratory protec- I tive device. The two general types of respirators which the Committee considered $ ^suitable for protection against silica dust are: p 9 p (a) Air-purifying respirators that filter out the dust particles. (b) Supplied-air respirators in which dust-free air breathed by the worker comes to him from an uncontaminated outside source. p c IMost respirator manufacturers have submitted their devices for testing and approval Jby the U. S. Bureau of Mines, and only those which have been approved should be used. c (a) Air-Purifying Types of Respirators - Of the air-purifying cla'ss, the type ost commonly 'used is the mechanical filter respirator for mechanically-generated a a uust. These respirators give no protection from.gases and vapors. They generally consist of half facepieces to which are attached.an exhaust valve and a filtering pedium that./emoves the dust from the inhaled air; some are equipped with a filter -Imediun that removes paint mists and some fumes. They are light in weight and inex pensive. Filter pads must be changed at certain intervals, depending on the concen n tration of dust. Some types restrict the field of vision. The general requirements of a safe and suitable Mechanical filter respirator are (l) adequate protection, (2) t reasonable comfort and convenience, (3) an acceptable service life period of protec 'ion, (4) easy cleaning and sterilization, and (5) low cost of maintenance in good t serviceable condition. e Studies of mechanical filtration by fibrous materials made by such agencies as t jthe United States Bureau of Mines (U. S.Bur. of Mines, Tech. Paper Nc. 394 (1926) and JU.S. Pub. Health Bull. Ko. 177 (1928)) and the Harvard School of Public Health (Journ. t Indust. Hyg. 9,26 (1927)) revealed that filtering efficiency varies with the particle [size and the amount of solid particulate matter retained; also that the resistance to t Air flow varies with the amount of solid particulate matter retained ana the rate cf air flow. After all, the fundamental basis for judging the suitability of a respi t rator is whether or not the amount of dust that is unretained or escapes through the filter under conditions of practical use is below the amount than would be harmful i to breathe. This is net related to ar.y percentage efficiency. In order to meet the t Bureau of Mines recuirements for aoorcv&l, a resniratcr must satisfactoriiv remove -77- dusts of the following size characteristics: ' ] _ C . 99 per cent smaller than 2. 80 microns 95 It II t t 1. 80 tt 90 I I II tt t t 1. 40 tt 80 I t tt tt 70 t l tt tt t t 1. 00 tt t t 0. 85 tt 60 t t tt tt t t 0. 72 tt 50 t t tt tt t t 0. 60 tt It will he noted that 80 per cent of the dust used in these approval tests is below one micron (l/25,000th of an inch) and 50 per cent is below 0.6 microns. Canisters will not remove dusts of these characteristics and should not be used as dust respi rators. In order to obtain the desired protection, it is essential that the face pieces of the mechanical-filter respirators fit the face of the workman snugly but with a minimum of head-band tension. A simple practical test, suggested by Carlton E. Brown of the U. S. Bureau of Mines Experiment Station in Pittsburgh, Pennsylvania (Jour. Indust. Hyg. Feb. 1937 Vol. 19, No. 2, p. 98), that anyone can run to determine whether a respirator facepiece is making a tight seal, is to wear it in a high con- ]centration of coal dust. The time of the test csui be shortened by blowing a stream of air containing a high concentration of coal dust around the edges of the face piece. The location and approximate magnitude of the leaks are shown by streaks of coal dust on the part of the face covered by the facepiece. Another test, according 3 to Mr. Brown, consists of plugging the intakes of the respirator and then attempting U to inhale. This type of test could well be supplemented by the Coal dust test. ] (b) Supplied Air Respirators - Industrial processes such as pneumatic drilling, ab- \ rasive blasting and spray coating have introduced atmospheric conditions for which the air-purifying type of respirators are not particularly suitable. Certain kinds of pneumatic drilling are responsible for dust concentrations so high that they would 1 rapidly overload a dust respirator. The operator of am abrasive blasting outfit ,, ^must be protected not only against the inhalation of air containing high concentra tions of dust, but also against impact and abrasion of the head and shoulder by the I rebounding abrasive and loosened abraded material. Spray coating is responsible fre- Jquently for pollution of the surrounding atmosphere by a combination of particulate matter (mists that are liquid particles or a combination of solid and liquid par "]tides) and harmful vapors resulting from the evaporation of the liquid vehicle of ~1' the coating'tised in the spray gun. Since these operations are carried out frequently in isolated places and at different locations at various times, they do not lend themselves always to general icontrol measures. Therefore, supplied air respirators perform a definite service. The types in general use are those commonly known as hose masks, air-line respirators, and abrasive blasting respirators such as sand blast masks, helmets, and hoocs. Supplied-air respirators have the following advantages for routine non-emer- Jgency use over those of the air-purifying filter respirators and the combination of respirators such as gas masks, mechanicalgas mask with a mechanical filter: 1. NO resistance to inhalation.' 2. Freedom from inward leakage of contaminated air. 3. Protection against all kinds of contaminants and even against ai mospheres deficient in oxygen which will not poison or irritate the skin. -78- 4. The Inflowing air reduces excessive perspiration and tends to cool .ace. 5. Vfnen a hand-operated blower is used a second person is always present. (With an approved mask, provided the facepiece is tight, the wearer can inhale enough air through the hose to es cape if the blower should stop). The Air-Line Respirator consists of a tight-fitting facepiece, a loosely fit- 1>ing facepiece or even a helmet or hood covering the head and extending down over the neck or shoulders. The air supplied to these respirators has been largely that ob tained from the compressed air source used in the performance of the work, as in sand blasting, pneumatic drilling and spray painting. This air is frequently con taminated with objectionable and, in some instances, harmful substances which, to some extent, can be removed by means of air-purifying appurtenances. In discussing; "Res piratory Protective Devices" in the February (1937) issue of the Journal of Indus trial Hygiene and Toxicology, Mr. C. E. 3rown of the United States Bureau of Mines wrotet "Using air from the ordinary compressed air system found in industry to supply respirators is not to be indiscriminately recommended. These compressed air systems are usually of the high pressure, internally lu bricated, reciprocating-compressor type. The air supplied by these systems is contaminated frequently with malodorous constituents such as vapors, mists and products of decomposition of the compressor lu bricant, slugs of water, and rust from the pipe line. All or most of these'contaminants can be removed probably b y some of the commercial air purifiers sold for this purpose. A pressure-reducing mechanism should be used also in the line to prevent any possibility of sudden accidental blasts of high-pressure air from injuring the lungs of the wearer of the respirator. With a compressor of this type there is always the possibility, however rare it may be in well-kept systems, of the generation of carbon monoxide due to overheating of the compressor lu bricant (Jour. Indust.Eyg. 18,461 (1936)). This danger can be minimized or eliminated by the use of temperature controls or carbon monoxide alarms on the compressor which, of course, should be so maintained as to pre vent the geners.tion of carbon monoxide, >. "The*trend in supplied-air respirators is to use special low-pressure, externally lubricated, positive-pressure air-supply devices. Most of the objections to the high-pressure reciprocating-type compressor do not apply to an. air-supply of this kind. Since these devices are not common in industry, however, it is usually necessary to purchase a special one for use with the respirator. Since air purifiers, pres sure-reducing mechanisms, and special compressor-control or alarm me chanisms are not necessary, the price of this respirator complete with air-supply device should not exceed that of the other type of respira tor without the air supoly system. "The use of a special air-conditioning unit to regulate the tempera ture and humidity of the air supplied to the respirator wearer is de sirable. " The minimum air supply for a respirator designed to use al1_1 the air fo res- ratory needs at a high degree of efficiency is generally agreed among .r.dustrial gienists to be at least four to six times the air breathed per minute, As a sneral class, respirators with loose-fitting facepieces, hoods, or helmets " y ; R R R R R R R R -"I R R R R R R P a a a R R $ r -79- core air than those with tight fitting facepieces. There is some difference of opinion among users of respirators as to whether or not adjustments should be provided whereby the wearer can van/ the flow of air to meet variations in his requirements. It was the opinion of the National Silicosis Conference Committee that definite recommendations for all situations cannot be made but for many situations, and particularly where tight-fitting facepieces are used an adjustable flow is desirable and may even be necessary; also, most workmen can learn to adjust the air properly. On the other hand fixed-flow procedures reauire a minimum amount of instruction and supervision and are the most conducive to safety under all conditions. While Hose Masks and Air-Line Respirators have many definite advantages the area of travel of the wearer is limited to the lengvh of the hose, and movements are handicapped to some extent by the hose. Manifestly, the air for the hose and the mask should be fresh and pure, but unfortunately this is not always so. Abrasive Blasting Respirator - Abrasive blasting respirators consist essen I tially of a hood, with windows, that fits loosely over the head and shoulders and designed to withstand and protect the wearer's head, neck and shoulders from abra sion by the rebounding of particles of sand or grit; and a supply of fresh air, at least six cubic feet per minute, blown into the hood. Only equipment which has met the United States Bureau of Mines test requirements and which is approved by the Medical and Safety Departments should be used. (c) Acceptance and Use of Personal Respiratory Protection by Workmen - As stated in a paper by G. M. Kintz and H. C. Fowler of the United States Bureau of Mines (I. C,6915 No.vl936) presented at the International Petroleum Exposition and Congress, Tulsa, Oklahoma, May 21 1936, selecting respiratory protective equipment is simple compared with getting men to wear it after it is supplied. Generally workmen will wear masks readily in places where they have seen others asphyxiated, or in some similar trouble, but they are likely to resist wearing protective equipment where . the dust cannot be seen or where the fumes and mist have no objectionable odor. ] There are three main reasons for such resistance: " First, inbred objection to any new idea; -- Second, the feeling that the individual is a superman and can "take it" without protection; and, Third, the inconvenience of wearing the equipment. In a survey conducted among the employees of the Colgate-Palmolive-?eet Com pany by Mr. F. H. Wallner of that Company's Insurance Department, it was found that | the men didn't like the disfiguring appearance of a "muzzle" over their faces. This j survey also disclosed that some workers objected to the respirator because vhey thought it made breathing difficult when the real trouble was that they were not j breathing correctly. Breathing through a respirator should be done deeply and slowj ly and after the proper habit has been acquired much discomfort may be eliminated. Quoting Mr. Wallner: i | "Foremen should appreciate that the position of the straps that ' hold the respirator in place has much to do with comfort. They should learn whether the straps should be worn over the head or around the i' neck. Some types have two straps, one to be worn around the neck, the other around the head. " . Probably the most effective plan in getting respirators worn is first to"sell" -80- ^ ;the supervising personnel who in turn should "sell" the worker by education, possibly aocompanied by strict and fair supervision and discipline. Employees exposed to dust | `hazards requiring the wearing of respirators should be convinced that it is essential J to sacrifice some comfort and dignity to avoid serious cases of disability and suffer . ]inc. Every worker should have his own respirator. It requires time and effort to . `adjust this protective device so it contacts the face snugly with a minimum of head band tension. It cannot be expected that the average workman 'will readjust a dif ferent resoirator each day. Also, the psychological effect of using a respirator jworn previously by another workman is not unimportant. Although he may not say any thing about it, it is naturally revolting to most men's principles of bodily sani tation to have to clamp over his face a device that has been soaked with sweat and dirt of another man's face and into which one or more men have breathed day after day! It is too much like using the other fellow's tooth brush. The best practice is to mark every respirator so each workman can identify his own. (d) Use, Maintenance and Care of Respirators - Personal respiratory protective de vices must be maintained in a condition substantially the same as when received from ithe manufacturer. Depending on the density of the dust replaceable filters should be changed frequently, to prevent their becoming clogged and usually it is desirable to use a respirator without a facelet. However, if they are considered necessary, jthe facelets should be changed often to avoid skin irritation. A clean facelt gives jthe respirator a clean appearance and removes one objection to wearing it. The Colgate-?almolive-Peet Company found that the habit of some workers of removing their respirators at intervals caused skin irritation. Everytime they did ilthis, dust settled on the surfaces that lay next to the worker's face and irritating particles were transferred to the skin when the device was replaced. It is, there- Ifore, best to have the employee wear his respirator constantly while under exposure. In some cases, ointments or petroleum jelly has helped to overcame the irritating ef| feet of points that contact the skin. I Where a considerable number of respirators are used, it is good practice to have a "Respirator Room" with an attendant who issues the respirators and cleans, sterilizes and otherwise keeps them in good condition. Respirators may be cleansed ~lby washing and brushing them with an antiseptic soap and warm water. They should be Jchecked for damaged or improperly functioning parts such as rubber valve seats and head-bands. If defective, these should be replaced by new parts. WEAT*MEDICAL CONTROL SHOULD BE EXERCISED IN THE SELECTION AND SUPERVISION 0? MEN WORKING ON DUSTY JOBS? - It is essential that adequate medical control be ex ercised. Such control' should include the examination, prior to initial working on dusty jobs of the worker to insure that he is a suitable physical subject. This ex lamination should preferably include X-ray examination of the lungs which permits closer control with subsequent X-ray tests as well as being a protection to the em ployer in the event of ary later legal action. A worker, to be classed as physically suitable, should be in additio: , de .termined to be a nose-breather rather than a mouth-breather and the natural filter-- Jing capacity of the%ose should be found to be satisfactory. G. Lehmann (J, Inc. Hyg. J17,37 - 1935) indicates that the "Silicotic susceptibility of workers with poor na sal filtration is much greater than that of men with good nasal filters" ile ad'vises that jobs with a silicosis hazard be held only by men with good nasal filters" and that mouth breathers are an especially bad risk. He suggests that the "dust re taining capacity of the nose be used as an index of the individual's qua!if ication for working in a silicosis producing atmosphere". It is possible that Sterr.stein's technique for measuring nasal resistance ("Industrial Dusts - p.55) could be developed into a simple procedure for selecting men best adapted to dust exposure. TX . J t n , , _A.it 1 o A ^ c-.r* I * *I 1 1 % 1 a* I 3 * 5 3 3 : 3' t : ** ; * t * rr i -81- for dusty jobs men who are past the age of 40 and not young men just taking up a trade. All workers engaged in harmful dusty operations should be periodically thor oughly re-examined, including X-ray tests. Particular emphasis should be placed on any indication of shortness of breath and chest pains . " Regulations should be enforced concerning the time limitation of work of any employees involved in a dust producing operation. Such Company regulations concern ' ing sandblasting calling for a fixed six-month maximum period on such work, after : which a minimum six-month period away from dust producing work should be followed more closely. : For protection from a legal angle, the worker should be given a final thor : ough examination including X-ray before being permanently transferred to some other 1 type of work, laid off or discharged. 1 . CONCLUSION j There is still a tremendous amount to be learned about pneumoconiosis and Jdust-producing operations. One thing, however, is certain -there is a very definite tendency to require compensation for industrial or occupational diseases. If these I compensation costs are to be kept to a minimum and the health and safety of workman U are to be promoted it will be necessary to make further studies and to promptly 2 adopt adequate precautionary measures. Many of these are now in effect, the others should be put in force as soon as possible. After years of study and direct contact with the Dust Problem, Mr. Dan Harrington, Chief, Health and Safety Branch, United JStates Bureau of pps. 119-21) with Mines, has came to this conclusion which we are heartily in accord (Eng. & Min. Jour. March 1937 "In the maze of uncertainties connected with almost all phases of 1 the causation and diagnosis of dust disease, about the only really well-determined fact available is that breathing large quantities of ] dust (or possibly of certain dust) over extended periods is likely under some conditions to be harmful to health and that subsequent al leviation or cure is difficult or impossible. Therefore, it would seem to be logical, to try to prevent dust formation thus preventing it fr<ja harming workers through respiration or otherwise. Here is a real job for the engineer, and little or no help can be expected in i these vital functions from any agency except the engineers and operat ing officials. "The most harmful of the ordinary dusts to breath is probably silioa dust, but, on the other hand, not even free silica, supposed ly the most detrimental of the silica dusts, is harmful unless it is 1 breathed, in considerable quantities and over extended periods. Ho human being ever lived any considerable time on this earth of ours without breathing silica dust (free silica dust), yet by no means all 1 of the people of the world have or have had silicosis. In other words, the quantity of dust taken into the respiratory organs is a controll ing factor in dust respiratory harmfulness. "One common-sense answer is that any atmosphere in which cust is visible to the naked eye is certainly too dusty to be breathed with safety by human beings, and the wise, farsighted, human employer will immediately start to decrease the dust content in any atmosphere ..here 4* -81- for dusty jobs wen who are past the age of 40 and not young men just taking up a trade. All workers engaged in harmful dusty operations should he periodically thor oughly re-examined, including X-ray tests. Particular emphasis should he placed on any indication of shortness of breath and chest pain * Regulations should be enforced concerning the time limitation of work of any employees involved in a dust producing operation. Such Company regulations concern ing sandblasting calling for a fixed six-month maximum period on such work, after whioh a minimum six-month period away from dust producing work should be followed more closely. For protection from a legal angle, the worker should be given a final thor ough examination including X--ray before being pemajie.itly transfe.rred to sane other type of work, laid off or discharged. CONCLUSION There is still a tremendous amount to be learned about pneumoconiosis and dust-producing operations. One thing, however, is certain -there is a very definite tendency to require compensation for industrial or occupational diseases. If these compensation costs are to be kept to a minimum and the health and safety of workman ' are to be promoted it will be necessary to make further studies and to promptly adopt adequate precautionary measures. Many of these are now in effect, the others should be put in force as soon as possible. After years of study s m d direct contact . with the Dust Problem., Mr. Den Harrington, Chief,, Health and Safety Branch, United ' States Bureau of Mines, has come to this conclusion (Eng. & Min. Jour. March 1937 pps* 119-El) with which we are heartily in accord ' j 1 I | j | "In the max* of uncertainties connected with almost all phases of the causation and diagnosis of dust disease, about the only really well-determined fact available is that breathing: large quantities of dust (or possibly of certain dust) over extended periods is likely under some conditions to be harmful to health and that subsequent al leviation or cure is difficult or impossible. Therefore, it would seem to be logical tc try to prevent dust formation thus prerenting it frqp harming; workers through respiration or otherwise. H're is a real job for the engineer, and little or no help can be expected in these vital functions from any agency except the engineers and operatlng officials, 1 ! | "The most harmful of the ordinary dusts to breath is probably silica dust, bu(:f on the other hand, not even free silica, supposedly the most detrimental of the silica dusts, is harmful unless it is breathed, in considerable quantities and over extended, periods. Ho human being ever- lived einy considerable time on this earth of ours without breathing silica dust (free silica dust), yet by no means all of the people of the world have or have had silicosis. In other words, the quantity of dust taken into the respiratory organs is * controlllng factor in dust respiratory harmfulness, "One common-sense answer is that any atmosphere in which dust is visible to the naked eye is certainly too dusty tc be breathed with ! safety by human beings, and the wise, farsighted, human employar will i immediately start to decrease the dust content in any atmosphere where dust is visible. After he has eliminated visible dust, there ;?.y -B3. etill remain irough very small Invisible dust to cause harm to the health of those who breath it, but in any event if he has exerted suf ficient well-directed effort to remove the visible dust it is certain that much of the smaller invisible, and probably most harmful dust has also been removed, "Manifestly, if dust is kept out of the air breathed by workers, the latter ofnnot succumb to dust disease of a respiratory character." In closing, we acknowledge with gratitude the support and cooperation of Dr. W, J. Deano, General Medical Director, Standard Oil Company (New Jersey) whose vision and active interest in Medico-Safety problems made this Dust Study possible. We also appreciate the advioe scad assistance rendered by; Mr. W, P. Yant, Director of Research & Development, Mine Safety Appliances Company, Pittsburgh, Pennsylvania, Dr. Leorard Greshburg, Executive Director, < Division of Industrial Hygiene, Department of Labor, State of Hew York, Hew York, N, Y. Dr. R. It Sayers, Senior Surgeon, TJ.S, Public Health Service Chief, Divieion of Industrial Hygiene, National Institute of Health, Washington, D*C. Mr, Daniel Harrington, Chief, Health and Safety Division United States Bureau of Mines, Washington, D. C. Dr. A. J Lanza, Assistant Medical Director, Metropolitan Life Insurance Company, New York, N.Y. Mr. E. H. Barlow, Chief Engineer, Standard Oil Development Company, Elizabeth, New Jersey. Mr. H. N. Blakesleo, Department of Accident Prevention, American Petroleum Institute, New York, N.Y. New York. N.Y. July Fifteenth 19 3 7 R. S. Bons it Chief Safety Ineoector Standard Oil Co. `(N. J. ) us 2*OmInMi !M*w