Document kDdy48LZZ4kO3wOVZXgD23vbO

FILE NAME: Colonial Sugar Refinery (CSR) DATE: 0000 DOC#: CSR190 DOCUMENT DESCRIPTION: Journal Article - A Survey of Dust Exposu and Lung Disease in the Asbestos-Cement Industry in New South Wales Dpcj.Jlk Studies in In d u stria l Hygiene J01. 24 \ A GURVE OP DUST .EXPOSURE AXO LUJIG DISEASE III ' I . THE ASBESTOS-CEHENT IEDUSTR IE NEW SOUTH WALES , ' i C e c il G . Roberts and Harry U. WH&lte D o H b A SUrtVEY OF UoT EXi CJUtiE *;!) lUilG. lUCEASE IJ) IHE ASai':JrcS-C^EI IKJDU3IRY. Ill _______ :_____________ MEVLSSiim. ________ , j _ _____ flISTOhICAl. ' , . r, Probably the e a r lie s t recorded case o f asbostosis b a o n tap -a r r a y in London, in 1900, con cerning the death o f a workman, aged 55, w:.o Had been 4x, e ed to asbestos dust fo r ootaa fo u rteen yeans'. In 1910 a lt e r the n e g istra r-G e n e ral liaa drawn a tte n tio n ' to the death c ] U r Sh S w r k e r from "acuto pulmonary fi b r o s is " _,od l- %sr.s s r s i i r e years1 exposure to asbestos -u Im, } ^ 4 a f t e r eigh teen revealed e x te n siv e f i b r o s l s ' o f t h e ^ s ? '" , O ff ic e on S e ^ S u " 6 ? ^ ^ " ? P r lc ? v^ ^ ' to the Hume cinntothuthtegraosubpeSotof sUceirnslouns<; r ^ to ^ini3` ^ U.cralnrgr ie1d9i8o"u9t fa c t u r a , ,vao w e re^ x -o sa d ^ lr*l y *n* ugea 1x1 t e x t i l e manu a l cn a very s n a il pro o r tio n ! , T e a s b e s to s , o r'a s b e s to s mixed fib re In - n r `' r t io n 01 cctCLn or o th er v e ge ta b le S - r t S ; w S r s v r i i f f oui ? . * * & , s e le c te d . Of those e x a a in - r i'n * ^ ln SUCh f a c f:oTy b e ln K ' f i b r o s is o f the lungs rhoda u M n era f0U? a to shiiye d i f fa s e exposure to high d u s t 'r o n n n ? ^ ? ? rS C0" s i J ere th at with f u l l y developed in seven t f n i n 10113 Ch" '" b r o s is 'w o u ld be a fte r auout thirteen year*- r ith H t " ' "itb ' P3 sib le death m aturation o f the f i b r o s i ^ ' m irht ?w r u? s t c o n c e n tra tio n s, -e a r s . U n fo rtu n a te ly 0n lv % ?S long as tw enty-five c e n tra tio n are shown flfa'ures * dU3t con- processes connected o n ly with ti - n^ e a^ply to Opening and handling f i b r e 1 w ithout i r " ^ iiiduotry. tio n , would be r e n r d e d I ! ' 1? a exhddst v e n t ila t io n , and t h is i s ^ h e o n lv dus t cone or. cru tlo n o^eru- to both the asb estos t e x t i i ^ * ^l s t ad th at woul4 be cowmen o f trie in d u s tr y . Ihe a u th in " ^ tos-cement sections sf iebx r oapspi sea. red to have X e f f u c t on the in cniedie^n cer oagfe thneor , i o f a su rvey o f ^ g ro u o ^ o f^ i r i S *iub^dsbdd bF S .B '. ieP ln .eters d u s t in the a s b e s t o s -e o t t o il i n d n ^ 0? 3 ex* ^ sed ,tn a s b e s to s t w e n t y - fiv e m oderate a n d ^ L h t ^ d v ^ a i f * " 1* , 1io b t f u l , were fo u n d . Ih e avAT-ii.ro advanced c a s e s <) a s b e s to s is t h i r t y - t h r e e p erson s wif-h9XlJ^SUr? o f tllc' whole, group o f was 1 0 . u y^ars Do d e r a te o r advanced; a s b e s t o s is to o ls (1 0 .5 years) had f f r i a j those w ith moderate a so e s- advanced a sb e sto sis fin greu tei` exosure than t hose with t h a t a s b e s t o s is do i 8 ,8 y e a r s ) . Tnere was. some e v id e n ce Those ^ d e r ? o r t ;ey : l r o f rL r" P id ^y ^ - persons? in 9 .5 y e a rs and a d m e e f h? d ev l o PCd . "^ a e r a t e a s b e s t o s is c o r r e s j ondlng f l ^ u r l s fo r " p o ^ 031 1x1 `J * y e a r s ; the 1 9 .4 and 11?5 lllrl " ^ rkuf s over f r t y y e a rs were . tin g e f f e c t o / tlh,nee ia$Uu3stt conn ^thub e1r7c*u!lo s is awc taisv aotbisnegrveodr . aggrava- Service years la te r the United btutes pub.'ie published i t s study by Dreassun e t a l . j ,o f Ua subaeltsu- tt iuasJ .lSs WIne r eth e C asbes urried t os ou t t Oeixl taiCl tel iIuneid, u.s.jt.Jry ,1 l. 1.p...duic.,nu l iicixitu:.uI'lehea- f a c t o r ie s . The dust samples m.-rv taken by C reenburg-w.-i L.i siue itpt ilne gd o r. d u In st t addi aken t io n , from lcolidegueilsc.ial t. abnraelya st heisn gwelreevie.uld, eanodt' of airborne lust c o lle c t e d by b ag-ty p e f ilt e r . uwphs> oust ceu n U were used fo r s i z i n g , l'ue to ta l dust exposure o f i each workmen in m illio n s o f p a r t ic le - y e a r s per cu b ic fo o t v.as found by m u ltip ly in g the dust count fo r each operation' by the number o f years spent on i t , and summing ,the proau cts so o b ta in e d . D iv is io n by tue t o t a l number o f years the worker was exposed gave the weighted oust ctn ce n tru tlo n experienced by the workman over th a t p e rio d . This method o f assessing exposure has been adopted in th is rep o rt. I S in ce t h e ir t e s t s were made by im pinger, a d ir e c t comparison i s p o ssib le with the te s ts o f the present survey wnlcn acre a ls o taken by lm p in ger, and th is i s 'done l a t e r . Only th ree persons cu t o f 108 exposed 'to a weignted dust concentration below fiv e m illio n p a r tic le s per cu bic fo o t , but 70 out o f oo9 persons exposed to a g re a te r co n ce n tra tio n were a ffe c t e d by a s b e s t o s is . From these fig u r e s , the authors concluded "Because clean -cu t cases o f a s b e s to s is were found only In d ust co n ce n tra tio n s exceeding fiv e m illio n p a rtic le s per cubic fo o t, and.because they . were not found a t lower dust co n c e n tra tio n s , f i v e m illio n p a r t ic le s per cu b ic fo o t may be regarded as the 'th resh o ld ` value fo r asbestos-dust exposure u n til b etter data are a v a il a b le . > The most s i g n i f i c a n t work cn a sb e sto ilis experlm en- Tanimals was r e c e n tly c a r rie d out In the United a ta te s by Vorwald, Durkan and P r a tt'. The anim als used were guinea p ig s r a t s , m ice , r a b b it s , c a ts and .dogs. From the r e s u lts o f t h e ir exp erim en ts, the authors made6 these ob s e r v a tio n s , among o th e r s . . "" e 1 . Long c h r y s it ile asb estos fib r e s produced a peribron- ?t on ts?is a, ri^n ila3Tl'.Tl>Sains<imo fa-l,stheexlcueapt >thsee lml aourse toaa'hpdumthaen adsobge. s i r f a i l u r e o f the mouse and tne dog o respond i s n o t known. Long asb estos fib r e s were necessary to produce the reactio n . . ,' s . The mode o f a c tio n o f the long asb e sto s fib re i s " ? c h a n lc a l> not ch em ica l, and appears t o ' Ho a c tio n , sin ce in f le x ib le g la ss wool f i b r e s do not prouuce f i b r o s i s , nor do asb estos fib r e s v.nich have had t .ic ir f l e x i b i l i t y destroyed by 3. Evidence was p r o c e e d showing th a t dust, con cen tratici r 1* / 3! ^ 1111011 Pa r t l c l o s per cu bic f o o t , co n ta in in g 0.6/S fi b r e s g re a te r than ten m icrons in ' le n g th ( i . e . under 1 m illio n asbestos fib re s greater tnan ten microns per cubic fo o t) w ill produoe experim ental a s b e s to s is in guin ea p ig s . The a c t u a l lower l i m i t ol concentration o f long fib re s necessary to'produce ex p erim en tal a s b e s to s is was hoc e s ta b lis h e dA. ' 4 . The d u ra tio n o f exposure required to develop the pulmonary re a c tio n tc in h aled a sb e sto s is .dust i s in rs e ly proportional to the concentration o f long p a r t ic le s lu the a i r . From the a u th ora' fig u r e s , about a5 m illio n p a r t ic le -y e a r s per cu bic lo o t would produce a very e a r ly a s b e s t o s ls , W ailst* with an ex posure o f 50 m illio n p a r t ic le - y e a r s per cubic fo o t the f i b r o s is would be q u ite marked. b . Further co n clu sio n s readied v.ere th at experim ental a s b e s to s ls ceases to regress on d iscon tin u an ce o f dust exposure and th at In h a la tio n o f asbestos dust did not a l t e r s lg n li'ic ..n t ly the f i n a l outcome o f ex perim ental tu b e rc u le :;ls in two s e r ie s of guinea ,<igs exposed to th at d u s t. , ` DESCRIPTION OF THE It.DUS TRY ' , The m ajor a c t i v i t y o f the a sb e sto s in d u stry o f New South Wales i s the m anufacture o f asb estos cement and i t s fa b r ic a t io n in to f l a t and corrugated shooting apd in to a lurgo range o f moulded p ro d u cts. In th is report o n ly .t h is sid e o f the Industry w ill be d e a lt ..it ;i, but i t is intended to deal wltij other se ctio n s o f the industry in a separate r e ,c r t . The m anufacture o f asbestos-cem ent products in j.ew South V/ales i s co n fin ed to three firm s o p eratin g in Sydney vdio In t i .l s s e c tio n o f the in d u stry employ approxim ately one thousand persons. 1 1 I . - The raw m a te r ia ls used are a s b e s to s , bement and w ater. The a sb e sto s i s re ceiv e d In bags from West A u s t r a lia , Soutn A fr ic a , Canada and a sm all qu an tity frorn'B aryulgll in New South W ales. Prom th ese sources the fo llo w in g tyues o f asbestos are obtained: am osite (an amphibole m in eral), . c h r y s o t ile ( fib r o u s serp en tin e) and c r o c id o lit e (blu e a s b e s to s ). \ The cement I s m ainly received in b u lk ; e ith e r by r a i l wagons or tr u c k s , which are emptied d ir e c t o n .to screw conveyors. Tne conveyors feed bucket e le v a to rs!a n d b e lt s which ca rry the cement to sto rag e b in s . A' c e r t a in amount o f cement i s received and stored in bags a g a in s t any hold-up in bulk s u p p lie s . On a r r i v a l the bags o f a sb esto s are man handled and sto red in s t a c k s . As required thelb ags are again manhandled and conveyed from the sto re to the p u lv e r is e r s or d is in t e g r a t o r s . T ills manhandling o f bags i s c a rrie d out by groups o f men g e n e r a lly known as "asb estos gangs".. The n ext step i s blending o f the asbestos by emptying and. m ixing with sh ovels the co n ten ts o f ap p ro p riate b a g s. ' The' mix i s then sh o v e lle d or hand-fed in t o the p u lv e r is e r s . .T il's work i s c a r rie d out by a fu r th e r group, sometimes known;as ."blower men". The ..u lv e r ls e r s are e it h e r pug or ham m erm ills. The p u lv e rise d product I s then blown through d u c ts ito sto rage hoppers, u s u a lly known as fib re -ro c iu s . As re q u ired , tnc b'lu..n asbestos is g e n e ra lly raked through sm all d oo rsin to burrows, weighed and then wheeled to the tid e m ills or b oaters chore the asbestos-cem ent mix i s prepared. In to these machines water i s run and the weighed asb estos f ib r e added. . Towards the end o f the b e a tin g p e rio d , ranging from 1 5 ' to 40 m inu tes, a weighed q u a n tity o f cement i s added from a conveyor b e l t . Only those operatives tuklng part in these e a r lie r stages o f the manufacturing process are lik e ly to be exposed to ex ce ssiv e d u st, but there i s a minor process o f reclaim ing diy scrap which g iv e s r i s e to a le s s e r exposure, bu-f one which i s , n e v e rth e le ss, a good d eal g re a te r than that found in the subsequent sta g e s o f m anufacture where the processes are m ainly carried out w et. I t m ight be mentioned .'here th at there I Is l i t t l e exposure to cu _e n t us op,. sal to a sb esto s c a s t no in any case cement dust a o ts not c o n s titu te any io r lo u s hazard to tiie lu n g s. > ' From the tide mill or beater the liquid mix of asbestos-cement is run into an ugita Lor whcmie it is J'ed as required on to f el t belts of the su-.ct making machines. Here most o f the water i s removed by f i l t r a t i o n and su ctio n through tue b e l t . The sneet now in course of* p rep a ra tio n i s tra n sferre d from the b e l t on to r o lle r s o f circu m ference ap p rop riate to the len gth o f tne sneet re q u ired , anu i s , u u llt up to a d esired th ick n e ss as tne r o lle r s r o t a t e . ' I t m-/ be cu t and removed from the r o lle r s e ith e r-m a n u a lly or m echan ically. For a f l a t sh ee t, i t i s then stacked between Stc-:1 l u t e s , but When a corrugated shout i s required i t I s U r s t Imna moulded on a corrugated s t e e l 'sheet and'tnu-u staciceJ between corrugated so. c t s . In som e'cases the handling o f these i.e t sneets i s e n t ir e ly manual and In o th ers h ig h ly uunnoohddrrejilnn ,.' TThh*e* Srie'eaeclti*o narev c ltcnhen taaklleoswepdlactoe is'tsanedxotfhoerrmcuicrin g <.nu hastens the p ro ce ss. Some sn e els are takeri away from 'r t ic le s lne/ rr0r Of a wide riange o f moulded a r t ic le s , -kfter moulding, these a r tic le s are placed in iinncrrrepaSset ttnneXPttudriCneovethreocf umrlonugldasn. d drying pro'cess and so - j. te r the sh eets have been cured ulna d r ie d , they are in .uost in s ta n ce s trimmed to s iz e by g u i l l o t i n e , band saws alia emery w heels, u recen t development,'has bean wet trimming o f the sheets to tne f i n a l siz e p rio r to the cu rin g and drying p ro ce ss. In t h is w ay'the amount o f dry scrau i s being reduced and w ith i t the exposure to dust a lre a d y mentioned in connection w ith d^y sc ra p . Asr,K3.`Ui':r ok the duet i/ypn.-him.- ' . I d Hew South Ytctles* dust c c n c e n t r it lm e aT ,,v u s u a lly determined by the Owens' dust counter, an average o f se v e ra l counts being maae over a s u ita b ly p eriod o f ** tim e, u s u a lly one h a lf-h o u r or mere. However', in order to >e a b le to compare our fig u r e s w ith corresponding American < nes, and with the American standard o f fiv e m illio n ,, r r, " b lc SSSCSSS! "*** fo o t' 11 " * s b" " ~ .ii! 2& & & & ? & ' WSfsSSB* bottom fi v e m illim e tre s below. The f l a s k co d ta in s tar cubic centimetres o f a co lle c tin g l l ^ l d w h lS ^ t u L .. i . _ a s u lt a b le Av o l1L e `:S t iMt =V ? ll e C l :1:l2 l i *j l d ^ u tc-d to o f the am ount^^^ust co llected f. 5 o then P*? 111410 a counting chamber. The one we use c o u n t^ th * " ? b r ig h t-lin e haemacytometer. From-the c e ll th t o t a l number o f p a r t ic le s in the c o lle c t in g liq u id can be c a lc u la t e d . The volume in cu bic fe e t .'o f a i r samples ia n IOUnf hy d iv id in g the time in m in u te s .o f cam pling by te n . D iv isio n o f the former qu an tity ,y the la t t e ^ g lv e s the dust concentration in p a rtic le s per cubic 'fo o t. ~ L>~~ There are both advantages ui.u dls-d V an tages in the- use o f tins m idget lu p in g e r . l'ne m icroscopic see-up used fo r counting does not re so lv e p a r t ic le s b'elo.i one micron in s i z e . I n is may not be such a d is a d v a n ta g e 'if .the l o i t e r p a r tic le s o f asbestos ( e .g . fib r e s over ten microns In le n g th ) have the s ig n ific a n c e a sc rib e d t6 then by some In v e s tig a to r s . S h a tte rin g o f the la r/ u r p a r tic le s tends to o ccu r, but th is d e fe ct is cott.on to a l l Jet-sam pling in - strumonts in which the uusty a ir i s drum thrqugh an o r if ic e i . i 1. ..y e lo c l t y * In " " y t e s t , o nly one sample need be obtained, instead o f a se rie s o f samples as with the (Kens' dust counter, f ills f a c i l i t a t e s co u n tin g, but-;does not allow assessment of the r e la tiv e d ustin ess o f the d iff-T e h t , nas-- o f an o p e ra tio n , nor may a s t a t i s t i c a l a n a ly s is be made of'"* tfifc re s u lt* , G e n e ra lly , dust samples taken in tills survey i i en " invites, or longer l f .'a l .l phases o f the op eration b ein g te s te d had not been covered. The t o t i l exposure o f each workman in m illio n s o f g a r H a le -y e a r s per cu bic fo o t was aeterm lned by m u ltip ly in g the ,dust count i-cr each operation by the number o f . ea rs ne hud'spent on i t soaring the products so o b tain ed . \ ' 1 ^ ie weaknesses o f th is uoLhod o f a ss e s sin c a workman's dust exposure are obviou s. I t assumes that tue o u st co n ce n tra tio n o btain ed by t e s t i s approxim ately the mean cpeerr-iiondrtDorf eynetar arst;io ?i t toig nwohriechs bthotaht "shanorht-atserbmeen( ee.gxp. ohseodurolyv)er a flu c tu a tio n s in the dustiness as w ell us long-term (e g over p eriods o f years) trends towards more dusty or l e s s ' dusty c o n d i t i o n . The former can be mlnim lse'd.by L k i ^ f ' more dust te s ts a t a l l working p o in ts blit the- , be estim ated w ithout having taken t e s t s some yfears b efore * m aanSyy oor^ tthhee ff aa cr tt*o r ie s concerned. t h is h u rti E f b e S ^ * i 4 in t a is report S t ^ i S ^ b f e V T ith , v i " B not the minimum and the maximum c u s t counts' a r r ^ n o v a i^ o r '^tne6'' IU#y - t put ;ip descending Position of Tests Asbestos , ulverisers L disintegrators T ice H i l l s and beaters Scrap bagging points Table 1 No. Uldget Impinger Count of Nature o f Work .m i l l . t a r t ./ c u b . f t . i.Average LOW- ... HlglV- C&t 4 a sb e sto s unbagged, 1/' blended by s .io v d ; i s . 7 c . b A. V U fed to u is in te g - rator j . Blown asbestos usu i _ . 6 a lly raked in to bar ' 1 o 0 .1 7.8 rows & wheeled to b e a te r . Wet-mixed , (iith cement in beater 3 P u lv e ris e d & blown '* .6 0 .8 5 .3 scrap fille d into ' bags from hoppers A 4 t Jic- Of Years J-o. c f a^loyees . Ob 16 10 i> 1 7b surveyed c, cut - c l ? f / - < % & * f i S c ho 1 f o r found t o 'o c w r 1! ? ! fflen1t i -- 1, S b e l i b l S ' i i i TM ^ 8 ^ io rt*'ork in Tery h l g j d u s r i o n " ^ exposure L d l ^ L ** " in workers uriH, i aUB* c o n c e a tr a ti ons f , * ***** wi t h ffliuiv o f rho " * l e , s than 5 y e a rs! ~ tua d i *dase I s rare durln, t^ ? ! e 8U" e / e d ^ *th em * l t ,l ln Uiu ir,<iua try tended t o ^ X l l S i S ^ ^ ^ ' r ^ T ^ 7 1 d u s t. I t w ill a ls o be seen 1'ruii comparing ta b le s 1 and b t u ,, t ` a la r g e proportion o f tue men, 10D oat ,, f 17b, ',.<=re employee on Jobs where the dust co n ce n tra tio n v.as on the,A verage 0.55 l'uble 3 D is t r ib u t io n o f Employees on V arloas Types o f Work Tested a t rime o f Survey Type o f Work He. Of Vi, ------- Employees' Asbestos P ulverisers & D isintegrators Tide i l l l l s 4c B eaters 18 ' ", ( ) Scrap bagging points* 0 ' F ib re Rooms C u tte r s L Handsaws > t , V * 1 _ Scrap Reclamation P lan t 5 , ' General fa c to r y atmosphere (handlin g, moulding wet sheets) 11 105 TOTAL 175 . ' : No employees occupied e n t ir e ly on th is work. . r m illio n p a r t ic le s per cu b ic fo o t and such exposure can be regarded as n e g l i g i b le . Having regard to the two fa c t o r s o f turnover o f Job and w idely d iffe r e n t co n cen tr_tlo h s o f dust experienced on d i f f e r e n t p r o c e s se s, i t was considered th a t t0v ,Usi m6tU3d a ss e s sin g the in d iv id u a l's exposure to measure i t in terms o f p a rtic le -.y e a r s te r nrora<-i0 t` t!:ls J urPse dust concentration's fo r each Tn' taker, as tnose found a t the time o f't h e su rvey. Iprronbifa^b1lef " tntCaTt 1<d; Sus?t hceorne d. tihteio nssurvheady wbeaesn cfaar ri riel yd os tuat.bilet fsoeermaed ccnsiderabie p e rio d .. N ev erth eless, the p o s s ib ility o f dust cc V t h f - t I k ? irom time to time cannot be djccluaed and The u f xp<?s^ re ca* be no more than an approxim ation. The r e s u lt s obtained by th is method are c l a s s i f i e d in Table 4 . Table 4 , ' C la s s ific a t io n o f In d iviu u u l Exposure to Dust iiillio n p articles per cubic foot ------------ * Y e a r s ________ No. o f , Employees , 1 o 127 ` 5 -9 18 . > I 10 - 4 16 ' 25-49 11 ' 50-99 ' 0 ;* 100 and over 3 : TOTAL 17b , ' -8 - Prevlous surveys carried out elsewhere, ai.j ..lrtu ay rc-ierred t o , have shown th a t a s b e s to s is i s n o f l i v e l y t.-,' occur unless exposure has exceeaoa b m illio n .a r t ic le s for more tauii & y e a rs, th a t i s to say a5 m illio n p a r tiu lc -y -.-a r s . I t v.111 be seen from the ta b le th a t in o n l; 14 cases iiad t h is l e v e l oi exposure been reached and in view o f .L a is a io .. in c id e n ce ol a s b e s to s is WaS to be expected alia. w s . iii fa c t , found. . j 9 CTJMlC/iL AND X-itAY FINDI?^ 1 ' tr The c l i n i c a l exam ination o f a l l the s u b je c ts was c a r rie d out by m edical o f f i c e r s o f the D iv is io n o f ! Dl oiiiil^siuo nt &no / t h ^meH ^ Drhepeasrttmx _ernat yosr beyit htheer bc oy.n-tshueltaTnutb erracduiloo-sis 1 D iv l s l c n . For tue x -ra y exam inations 14" x 11" fU rns were used in a l l c a s e s , hnore exposure had roaohed a le v e l v i-v e d ChvJ ?b eS t0 S lS ^ h t be ^ . c t e d , the- film s here re - CL, l l persans. s k ille d In tile assessm ent o f n f j 1,1 D iiiul judgement on t h e 'film was bascu oy bv the ' i n th h g er,eral cons,w` rua o pinio ns given f i n d i n - I 1 ! ' ^ i J peaching the d ia g n o sis the' c l i n i c a l evidence ^ 1x110' c o n s id e r a tio n , but t)ie c l i n i c a l did fhe c,i biseas? wus n e g li g i b le and in only, 'two cases aid the symptomatology co n trib u te tc a d iagnosis c f a s- tt oo ss iiss ttoo 'do uus'ti * exfoplolosuwrien. 8 tu b le r e la te d the cases o f asbes, Table 5 Incidence o f A sbestosis related to Dust Exposure , Exposure in m illio n p a r tic le -y e a r s per cubic foot " Persons Lxposod .Persons at ffe c t e d Less than 10 145 . 1* . : o 10-8 4 16 ' .. * ' 2 ' 5 - 49 11 . ' 4 ' 50-99 , 100 and over TOTAL C ' . f' 0 ' , / 17b . i: 9 per cubic lo o t exposure. In both these cases the estimr Kr r . -` "9X" Te tt-a l 5, IwhTose1" sutrv*e, ty l fh*as a l"rea d yK bf eeSnb rieTfefrtriead ' -t A found & cases In 196 persons with exposure o f le a s than -b m illio n par t lc le - y e a r s pur c ..b ic 1`u u t. l t . u u s been pcIntea out that such estim ation s o f exposure are no uore than approxim ations ana i t I s q u ite p o s s ib le th a t tnesc- stra y cases ..here exposure .'as ap p aren tly w ithin toe lim it s o f sa fe ty viar a t some period exposed to h igh er co n ce n tra tio n s o f dust tour; were found to e x i s t during the survey on the p r o c e s s.s where the men hud worked. Ihe ln ciqo n ee o f c a s e s , four out o f eleven persons exposed a t the 25-49 m illio n pu rticle-yeu rs per cubic foot le v e l of exposure, is con- s ld e ra b ly h igh er than th a t found by D reessen ,.n am ely three cases out of eighty-fou r persons exposed. I t i s in te rest ing th at the sm all number o f three persons v.tio had an ex posure o f over 100 m illio n ,a r t i c le - y e u r s cubic foot a ll snowed sig n s o f a sb e sto o ls compared witn roughly h a l f in; breosen* s su rv e y . Iio ..e ve r, the numbers with- nigh l e v . l s : o f exposure found In our survey arc so sm all' in comparison with h re e s se n 's th a t tne d iffe r e n c e s mentioned are o f no sta tistic a l sign ificance. . ' ' Advanced stages o f a sb e sto sls are seldom found with exposure o f le s s than 100 m illio n p a r tic ie -.y e a r s per cubic fo o t and in t h is survey only one case was found w.-iere the disease could be regarded as having passed the early stage and the x -r a y revealed the c h a r a c t e r is t ic ground c la s s appearance o f the lung f i e ld s . In th is c a s e 'the estim ated exposure was 167 m illio n p a r t ic le - y e a r s per cu bic f o o t . T able 6 shows the r e la tio n s h ip between toe i n - : ciaen ce oi a s b e s to s ls and the len gth o f exposure to a s bestos d u st. Ihe la t t e r is not n e cessa rily id e n tic a l with len gth o f employment in toe Industry (Table 2 ) ; fo r c e r ta in o ccu p ation s ( e . g . watchman, d e liv e ry man, cle rk ) have no exposure- to the d u s t. ' Table 6 Incidence o f A sbestosls related to i Exposure Time . i Exposure Time in years Persons Exposed Persons Affepted Less than 5 5 -9.9 10 -1 9 .9 20 and over TOTAL 102 42 . 26 5 175 1 5*. *i t i :i 1 . 9 be seen that only about one'percent of those workmen w ith le s s than f i v e years* exposure were ff iivv ee C/vefdars*1tl l lesxtpoasburoeut shtoewn ed>Jesrigcnesnt o f a stbheossteo swlsit. h- mThoerese than ilgurc-s are sciaov/hat lower than toose found by 'n rc-sse n ot a l , vac r e n t e d 10 cases ( # ) in *88 p e rso n s*b o se d ^ -10- le s s than f i v e y e a r s , and 63 cases (40; ) in 159 persons exposed l'o1 fi v e or more y e ^ rs. Tins U if 1'ureuce between tne two surve/s I s s t a t i s t i c a l l y s l g n l f i c u i l ana, sin ce wo have consluered iiere only p e rio d s, o f exposure, -would prouably Ue caused by tne h ig h er dust c o n c e n tr e tlu is found In tne a s bestos te x tile Industry. ' ' A sinllur table snowing tne relationship oetweei) the incidence of asbestosis .and tile weignted cnist concen- . tration, is given below. ; Table 7 ' Incidence o f A sbestosis related to Weighted. D ust Concentration - Weighted Dust Concentration in m illion p articles per cubic fo o t Persons Exposed Persons AfXected Less than 5 5-9.9 10 - 1 9.9 20 and over ic r 4 13 i 5 f 4 0 : o TOTAL 175. ` i .9 ' In t h is ta b le n e a r ly three per cent o f the workmer exposed to a weighted dust concentration o f lda,s than 5 ooff tthtese" aerxposCeldH %toPera wCUe?lglnctefd00tdu*set recoenfcfeencttreadti.o-n Soo f wfeirvee CS# m illio n or more p a r t i c l e s per cubic f o o t . , Corresponding : fig u r e s from tne re p o rt o f Dreessen e t cd . . e r e o u t o f8108 e ^ d o v e -.s (or 2>*-) and 70 out o f 239 employees' (or 215,') I t i u r Cf i u r L th a t t i ere HS s l n l f l c a a t d iffe r e n c e between* American o n e s ^ giY9a ^ t llis ta b le > tne corresponding . ^ne numbr o f cases w itu p h y s ic a l s ig n s , or X -ra v eviden ce o f r e s p ir a to r y d ise a se o th er taw a s b e S t S s lI 7 s'c out o f 175 (Ia b le ) i s h ig h er taun mignt be e xp ected . fable 8 i*./ Cases o f R e sp irato ry D isease other tU'un A sb e sto sis ! . D ise a se Humber > , Tuberculosis - A ctive " Healed B ro n c h itis Other "2 1 4 ; 11 1 5 . total ' - *2 y ^rsrsvsns^ ~ m V & ,2 > s r i" .:% icis sn ^ ,, c s s . i r r i 01- su ggest a c t iv a t io n C f the d is e a s e due to* ^ L <*** =*" * * a ^ g ? y ^ ,i i i i a r s . ^ r Sthiee IlnSduuIsi,rirvy' Vfo,"r' "n''i?n epry' evaltras= 1v .'ltn""aOn seinxcpeo sbuor*e'o.af t,'lbo Liilal i i oinr , eevvidi ednScer oorf drre -a>cJertlHvcau^tal con fooof t thweithdoisueta stuee. re b.e in g any1 y o f tne eleven cases o f b ro iich itis ex- S5%S S S i." & { T `i S . , ?" i 6 `une'p" ici2 exposures were 6. 17 and l l ' a n H ^ rem aining turee ca p e s, SS i't FXiZS'H r " ty In clu d in g chost x-ruy!^ A & i i n r P l y^ e t " e d ic a l exam ination, COIiCLUSIONf; . , c f . c r l l c r ^ L r S ^ L S d 1" ^ ! " ; ' ' " f l TM V w c r l .n c . i K K . S ! * s s K * r i - P r4 i s a s s i ^ r "- p rocesses were found where the dust loi,'el'* .b e y e rttie le s s,. enough to le a d in e v it a b lv tv, c?n c e n tra<tions were high provided the L p ?oyees Jobs. Fortunately these erodes ot b e s t o s i s ! enugh in, those p a rtic u la r workmen, but i t i s recommended th a t few th e se men g r e a te r p r o t e c t i o n I g a i L t d u s t. t0 glV e F i r s t l y , c e r t a L i^ u s t y ^ a n d ^ r o r ^ c o u ^ d ^ duc^' su p p ression , fo llo w in g shows. P r io r to t h is * . TM ^ 1 b " e =han is e d , as the a screw conveyor to tra n sp o rt the b T ^ A n f 'irm had ^ s t a l l e d rooms to the tid e m ills - sin A .. 0 n * soesto s from tne f i b r e in s t a lle d a b e l t conveyor to ^eed t h e ^ ^' tiie -same firm lias the p u lv e ris e r. I t is considAna^ asbestos to have le sse n ed the exposure to anh c^a - P o tLl theSe measures do n o t e n t ir e ly e lim in a te tne e x j o * ! .^ * USt" v Su<sh improvements are o ccasion s, such as durin- r ii, to dust .since there emptying o f f i b r e r o o m f w n^ ,, 2 " ! I?r u u rin 2' the complete spaces and snovel the f i b r e ^ o r haVf ^ ` ater confined short p erio d s, an approved r`r ^ Pe r io d s - . In tnese adequate protection^ 'Pe f dust rcSP ira to r'w o u ld a ffo r d mwaetcehr-ansipcraal yasndor pwneiu^moatiilr^ p r a y s 8 hdow* eevTeerr* t11h^id r' enedlteares r bwotihth because the wetted m ineral t e - d s ^ o * 1? * f , hd f i b r e s d i f f i c u l t n u cis, conveyors, e tc . dS to ttdriere *to.t*,Ih e sid e s o f ' T *la b! '.p r c .ia a ,, p o in ts in order t o t o c r e a s a t l ^ ? ncl 'osut, e o f these minimum a i r movement o f 50 < f the ;e^ a u s t . A cpcclbg 1 fa . the cccess 0 !, tea410 ^ my s s .s a s zrzsL,