Document dneL4x9Zwb0JepNByDkgVK280

FILE NAME: Avondale (AVD) DATE: 1973 Mar DOC#: AVD131 DOCUMENT DESCRIPTION: Journal Article - Biologic Response to Kind and Amount of Asbestos PLAINTIFF'S EXHIBIT Biologic Response to Kind C -> and Amount of Asbestos --i CD OT M o m Ktetafctd, M.D. cn cn CO o, D tu d t of ft biologic response to different types of asbestos dusts in dicate that ih e ir inhalation m adequate concentrations can produce pulmonary and pleural fibrosis and/or several types of malignancy, chiefly of the lung, pleura and peritoneum ' Associations between asbestos dust exposure and malignancy of the gastrointestinal tract have been reported* 14 However, a general con sensus w ith regard to this association has not been evolved' Most of the evidence of association between asbestos ex posure and human d.-ease Ha; boo-, and decreased pulmonary compliance. Asbestotic pulm onary fibrosis has been produced experimentally in various animal species However, dala on relative fibrogemcity o f different asbestos dusts in animal w o rk has not been con sistent* * Human data on relative fibrogenicity of different asbestos dusts is stiff inconclusive Murphy, Ferns and Burgess7 studied pipe coverers exposed mainly to chrysotile and amosite dust Asbestosis was first observed after 13 years of exposure to the dust or about 60 m illion particles per cubic foot (mpcf) sm oke. Age. sex a nd duration o M . posure to asbestos d id not account for this diffe re n ce The prevalence oi pulm onary fibrosis rose w ith increasing am ount and dura tio n ot cigare'c smoking and w ith increasing exposure io asbestos. 2. Bronchogenic Carcinoma Availab'e data confirm a relationship between pasi occupational exposure to asbestos duns and higher than expected incidence oi bronchogenic ca rc in o m a 1 0 -" Some studies have demonstrated ditterences n degree of risk am ong dmerent oc acquired from occ-ca: o r,al! exposed years The prevalence was 38% alter 20 cupauonaily exposed g-pups prebah1. groups years o f exposure In a recent un related to type and concentran.m published study o f talc workers exposed asbestos fiber, nature of work n - to a mixture o f talc w ith tremolite and formed, and other factors such a- Effects o f E xposure to D iffe r e n t a n thro p h yllite as the predom inant sm oking cigarettes'* and presence of Types of In h a le d Asbestos D usts 1. Asbestotic Pneumoconiosis O f the d ifftre n t pathogenic effects associated w ith asbestos dust exposure, the first clearfy demonstrated adverse effect of asbestos in man was pulmonary fibrosis or asbestotic pneumoconiosis There is general agreement that all forms of asbestos in commercial use can produce fibrotic effects m the lungs' Asbestotic pneumoconiosis is ch a ra cte re d roent- fibrous components, Klemfeld, Messite and Unger* found only one case o f pneumoconiosis among a group o f 39 workers whose mean expo-ure was 16 2 years w ith a range of 11 to 22 years. The mean dust concentration to which the workers had been exposed over a 20 year period was 23 mppcf w ith an average m inimum concentration o f 6 and an average maximum ot 68 mppcf. In both studies' 8 consideration was melafs in the asbestos dust14 For exam pie, in a study o f m ortality in relation to occupational exposure in the asbestos industry, interline. DeCoutle end Hen d e r s o n 12 o b s e rv e d d ifte re n c e s ' respiratory cancer mortality betwevm a in te n a n c e se rvic e w o rkers an production workers Two possible x< plananons were offered for the on ferences in respiratory cancer rncr` l between these tw o groups, one rhai genographicatly by diftuse interstitial given onh to nme-we'ghted average ex interm ittent asbestos e*po*ure ot m j fibrosis of variable degree sometimes associated w ith pleural fibrosis and calcification Clinical signs .nclude lung crepitations finger clubbing and dysp nea, physiological changes are con sistent w ith a restrictive lung d.sordcr manifested by decreased 'orced vital capacity 3'minished d itu sio n capacity posures Peak concentrations were not mentioned Lacking data on peak ex posures and since the operations ditrered significantly one cannot truly compare the relative patnogenieitv of the dusts reierred to m the tw o studies As m the case of bronchogenic car cinoma the lactor ot smoking must be corwiclL'cd m r" lo'i. s j j'b e s lo - ex tetiance service workers proudbly a. very High level, produced excerespiratory cancer bur no g rt'it excess > asbestosis: a n o th e r exrsianafion .s j based on types o f asbestos to * f / these tw o groups of workers were posed Srxtv-tour perepnt of ;re ma fenance service w o rk e rs w ith h gh posures had been exposed fo croculo 0'c ' >< *-- Vv Yo'% Nu*" O* ,>jrlfnpr of abt/f 31 C* " ^ *v^v W * \ > V I } jo J C ' l ' f i ? " ' r ' l-^ posure and d e vc io n i'.c - nr pulmonary tiprosn In a -t-cS ui 10/ a-Px-kw texti'e asbestos whereas 8C oi tS- pruduc. 1 vvbrkers w ith h,gh e x p .i-u -o had b v<ror\,ne''Ul v*i . * .y w^ ` Ji w o rk e rs W e i'- 4 ' n , " d that 'h o so exposf-d, rncl.cj;in._ .tut c..jO.: ji % Cf If* - P'ev J l` n-P nr ibros.x w J- was more care,nog- - r iro n i->. - m. '* `CO Of p1n " T 1. " y t ; 40 j m - " i }- 2-1 , in n o - asbestos d u " ' r a i n 1, c 'l'v - jt h _ 296 '*8992x01 S *noiite. to w hich these workers were reported 33 case* of m w olheiial tumors western Cape The greater penetration Oposed. Cigarette smoking is in id - in a part of South Africa important for to the deeper alveoli adjacent to the (JHionil factor or importance, (n a study crocidolite mining, investigators m other pleura by the smaller crocidolite fibers gi .nsulation workers, Selikoff, Ham- parts of the w o rld 1* 17have examined the could account for difference* m in mood and Churg11 reported a m ortality distribution o f mesotheliomas m the c id e n c e o f m e s o th e lio m a a m o n g #sk 92 times greater among insulators general population and among oc workers m the tw o areas In addition to nho smoked cigarettes compared to cupationally exposed asbestos workers the biologic im portance o f fiber diameter men w ho neither smoked cigarettes nor The results indicate a fairly good and shape, other factors such as metallic worked in (he insulation industry More relationship between exposure to d if cation* and enzymes present in asbestos rtcentfy. the role of trace metals has also fe re n t asbestos d u sts, n a m e ly, dust remain to be evaluated, particularly been considered a m aior factor in car crocidolite, ehiysotife and amosue or m view o f the fact that not all cinogenesis among asbestos insulators' * mixtures thereof, and the occurrence of mesotheliomas are related to asbestos Wagner. Gilson Berry et a l' com m othetiomas. Wagner1* pointed out dust exposure mented that the risk of bronchogenic that amphibole fibers, which are straight, There have been a variety o f animal carcinoma is dearly related to the in are more likely to reach (he periphery of studies m w hich experimentally induced tensity of past exposure and to the risk ot the lung in contrast to chrysotile ribers. mesothelioma has been reported in d if asbestos's When the environm ental which rosemble stretched coils and are ferent animals.*1 O f particular interest control is surf c ie n t to e lim in a te readily intercepted by the bronchi, is the study o f Roe. Carter. Walters et a l- 1 asbestos's, tne excess risk of- bron- especially at bifurcations The lesser risk w ho produced pleural and peritoneal ihngentc cance' d mmishes Wagner 31 developing mesothelioma iro n ex mesothelioma in mice subcutaneously ind associates also -q.cated that it s posure to chrysotile fibers mav be due to miected w ith crocidolite, amosite and not known whether me woe o f asbestos ~eir curly nature, which prevents most Chrysotile and thus have shown evi inhaled influences me risk o f bronchial o- uem from reaching tne p'eura dence ot migration oi fibers, a finding cancer in man Excenments in animals 'Aagner has, therefore, emphasned that w h ic h helps e x p la in p e rito n e a l suggested to them mat t should because quantitative studies ot the d istn o jlio n of mesothelioma in workers exposed to d il- thrysotile produces 'ess severe fibres.s q." erent woes of liber within ms lung terent asbestos dusts 'Han does amosue or crocidolite in eaua. n .owing nhalauon need to be e*- One noteworthy feature about the o c ilo-.es 'ended However not all ampmoole currence of asbestos mesotheliomas hay The quest.on or whether _the ca- ' cers show an increased prevalence tor been the long period, com m nntv over 50 onogenic role of asbestos is rela'ed m ~esotheltoma production De-oite a years between nrst exposure to asbestos ^ `e specific kind ot tiber is more d i" c . -q-ouen searen no inesuiieOTs h,e and appearance ro m o ih p iio m a '" - 1 :n answer than the question of d c -r- : i~ n associated w ith ar.tn jiv lli t e Whitwm t and Ruwclnre-' o b -e rw il 'hai telated response For this purpose a-bestos production in Fmlaro ' the interval irom first exposure to ` Wnght* indicated that populations w.m f'.mbrell Griintns and Poores- em asbestos and appearance or meso long-term exposure to only one vanet. phasized the im p orta n ce ot lib e r theliomas ranged trom 13 to 63 sears hi fiber are needed. V irtu a lly ah diameter in addition to liber shape irt w ith a mean or 42 years They ex fabricating processes use more than one re la tio n to d e v e lo p m e n t of pressed the o pinion that the incidence of variety w ithin the same prom ts at any m e s o th e lio m a They p ro v id e d a m olheliom a w ill continue to nse w ith one time or have used more than one plaus'bte explanation for difrerences in increasing use o f asbestos un til about 40 sanely at various times. Populations frequency of diffuse mesotheliomas in years after adequate protective measure* restricted to m in in g and m illin g the Northwestern Cape of South Africa have been taken. Another important i operations m the production of asbestos where only crocidolite is mined com feature about m o th e iio m a m contrast 'iber lend themselves best to a study of pared to the Transvaal region where to bronchogenic carcinom a is rhat He etrects of a single kind o f asbtos both crocidolite and the closely related cigarette smoking does n o t appear to be 'her it is these populations w hich can amosite are mined The occurrence o f an im portant factor related to its 11 P'lAide the answer to the influence of a m otheltom a m the Transvaal is rare development *><v;e variety ol asbestos fiber m terms The mean fiber diameters ot Transvaa! 4 Pleural Calcification- Cato tied or carcinogenesis However, the role of crocidolite and amosite were ih-ee times pleural plaques have been reported hi'twent types of asbestos in raising the those of Northwestern Cape crocidolite am ong w o rk e rs e xp o se d to a n - ,nc dence of bronchogenic cancer ap Timbrell et al postulated that dirrerences thophylltle, chrysotile, amosite and pears to be dose-related and may m diameter w ould influence the ability tren,elite, or mixtures thereof-'*-a* upon the specific category of of fibers to penetrate to the periphery of Multiple or bilateral pleural plaques are i V - especially m -egard to degree of ef- 'he lung and pleura where the tumors regarded by some investigators as v ir V develop 8ecause of their greater tually diagnostic of asbestos related ) M esom ehal Tum ors Primary "a1gnani tumors of the pleura and n-" toneum, formerly regarded as ex " dingly rare bv most pathologists are ng reported more frequently, par aerodynamic sute, a higher proportion bv mass of Transvaal fibers w ill be deposited in the 'arger a.-wavs by gravitational settling and he te e w ill reach the periphery ot he lj~ a s w ith disease; however, other causes oi pleural calcification are v\et! know n Robinson" found pleural plaques m 2 7x of 1,820 autopsies per-ortned chiefly upon adult male* No relation a ' - 1a.-1v among workers exposed to much less chic eocv than >h* shorter and .'i-os dust' Smcp w a g - e '" ' '-i smaller diam eter nbers Ot ' "e North ship to ty p ic a l asbestos bodies degenerative or neoplastic disease or -nat cf Occupational Medicme'Vat 15 No 3 March 1973 297 STOSUS75 k n o w n in fe c tio u s disease was discovered. Robinson indicated that pleural plaques should not be con sidered proof o f asbestosis not termed "benign fibrotic mesothelioma". W ith regard to those occupationally exposed, pleural calcification rarely ap pears u n til 20 yean after first exposure and does not necessanly correlate w ith pulmonary fibrosis. Pleural calcification also appears to differ in frequency m d if ferent occupationally exposed groups, but studies to date have n o t explained such differences. The finding of pleural calcification o r pleural plaques has been reported as being comm on in Urge segments o f populations not directly ex posed occupationally to asbestos but ivmg in or near regions where asbestos ibers are being produced and used" 11 There is no evidence that presence o f pleural plaques bears any relation to the developm ent o f m esotheliom a. In Finland and Eastern Quebec where a greater frequency o f pleural plaques has been reported, there has been no increased frequency of mesothelioma' Furthermore, one cannot conclude that presence Of pleural calcification is an in dicator of previous asbestos exposure since other causes 'ead to th's condition, nor can it be assumed that absence or plaques excludes a history o f exposure to asbestos. Effects R elated to Q u a n tity o f In h a le d Asbestos Ousts 1. Correlation of Environmental Ex posure and Biologic Response Balaer and Cooper*4 reported asbestosis among insulation workers exposed to levels not exceeding the time-weighted average of 5 m ppcf Chrvsotil and amosue were the principal types ot asbestos minerals lo w hich the group studied was ex posed Murphy, Ferns and Burgess et at' reported that asbestosis was first ob served in the group they studied after U years of exposure, or about 60 mppcfyears The highest average concentration was TOO m ppcf and lowest 0 8 mppc* w ith an overall average o f 5 2 mppcf Amosite and chrysoit'e were used but no crocido'ite was present No asbe-tosw was found m men exposed less than 60 mppcf-years Twenty percent of those exposed lor '5 to ' 00 mppct years were considered to have asbestosis \ j a'- tempt was made <o correh'e worse's 298 w h o had asbestosis w ith the charac teristics o l dirterent jobs in the w ork place nor w ith tim e spent on the ob. Peak concentrations were not given. In a recent unpublished paper, W illiam s, Baier and Thomas** compiled data on exposure levels at various textile processing operations in tw o plants for 37 years and 20 years, respectively. Even though exposures were mainly below 5 m ppcf and in many instances below 2 mppcf, 64 workers were repotted to have asbestos. in an unpublished study, Ktonfetd, Messite and U nger* found only one case o f pneumoconiosis in a group o f 39 workers exposed to commercial talc containing tremolite and anthrophyllite as the mat or fibrous components, despite a mean exposure o f 16 2 years w ith a range o f 11 to 22 years and a time-weighted average o f 23.0 mppcf The mean fiber count, obtained only in 1970, was 34 fibersfml w ith a fiber length greater than 5 microns/ml The range varied from a low of 8 to a high of 160 fibers/ml In a comparative study of talc workers employed in tw o different plants and exposed to the same minerals, these authors* observed a Significantly increased prevalence ot pneumoconiosis based on chest roent genograms and clinical findings in the workers w ho had four times the mean fiber count than the comparative group even though mean age and average duration of exposure and range were similar fo r both groups, indicating a dose-rer ponse relationship. Enterlme. DeCaufle and Henderson* recently dem onstrated co n vin cin g evidence for an exposure-response relationship between chrysotile asbestos, measured in terms of m illion parts per cubic loot years (mppef-years), and risk of m alignant and non-m alignam respiratory disease Specifically, the nsk of respiratory cancer increased from 166 7 (Standardized Mortality Ratio) at m in im a l exposures to 555 6 at cumulative exposures in excess of 750 mppcf-year5 The percentage increase exceeded 300 W ith regardto nonmalignant respiratory disease, the in creased risk was noto n ly to pneumocon os.s and pulmonary nbrosis but to othe' diseases of the respiratory svstem as wel' McDonald Ross.ter. Eyssen et a l' 7 reported r,n' 2d primary thoracic n toD .iv'" > a"-----^ 9 304 io-me- em p lo y e in a chrysotile asbestos m ire and m ill. Five of the neoplasms were mesotheliomas. Although the autnory concluded that even heavy asbestos exposure earned only a modest nsk of con tracting lung cancer and an even lesser risk o f co n tra ctin g m esotheliom a. 5efikoff** in commenting on McDonald's "h ea vily exposed" group stated that these workers demonstrated five times as m uch lu n g o n c e r as the group of "lightly exposed" workers. Whereas branchial cancer is more dearly related to intensity of exposure, data on mesothelioma are less certain w ith regard to the influence ol quantity There are many examples where ex posure has been short, though not necessanly slight'. As mentioned by Wagner, Gilson, Berry et a l10, mesothelial tumors apparently occur more frequently in the peritoneum than in ihe pleura when the exposure has been extensive, but the route of entry of dusts mto tne abdomen is not k n o w n Epidemiological studies show that there is much clearer evidence Of nsk of mesothelioma varying w ith type o f asbestos than in the case of bro n ch ia l carcinoma The study ot K ivilu oto and U p u m in 't P'Ovdes evidence that exposure to anthophvil 'e very rarely causes mesothelioma The very long period that elapses tchveen first exposure and development o( mesothelioma has prevented an estimate of what proportion o f an exposed group develops mesothelial tumors Wagner. O lson, Berry et a l10 believe that the proportion is likely to be fairly >mall. much less than that fo llow ing exposure to bladder carcinogens for example As true fo r pleural calcification, not all pleural mesotheliomas are relatable to exposure to asbestos, there are presumably other causative factors This makes interpretation o f the relationship between asbestos exposure at a low level and mesothelioma difficult There is need for more prospective studies on the quantity as w e ll as rype ot asbestos bur den in the lung and occurrence ol mesothelioma. 2. M ortality Experience From Lung Cancer, Asbestosis and Other Non,Malignant Respiratory Diseases Studies of the m ortality of workers in d.rterenr asbestos industnes and trades and de ferent asbestos dust exposures' " '' ,Q N *> indicate that past exposure to dir erer.t asbestos minerals has c o rtrib u 'ec to an excess of m ortality of cancer o' tH. lu Biologic Response to Kind and Amount of Asbestos hlenfeld ura and peritoneum and its comcX ions. and n o n-m alignant iiratory diseas over the general sulation In several studies an excess deaths from g a stro in te stin a l lignancy1 '* Has been reported. itudies on mortality experience point the im portance of elapsed tim e from lal exposure and duration and degree exposure as factors w hich increase the a precise animal model from w hich to derive a dose-response relationship for extrapolating nsk factors m producing disease IS lacking. Unfortunately, the amount of asbestos dust required to produce pathologic effects rn animals is unusually large in proportion to amounts to which man is exposed Hence, animal data w h ich have shown different respon ses to different types of asbestos* 4 can There is no generally accepted basis that permits assignment of relative risk factors to fibers m the electron microscope range compared to fibers in the light microscope range. Suzuki and Churg4' contend that submicroseopic fibers are responsible for most o f the biologic changes produced by asbestos. O ther in vestigators have also pointed o u t that the fine dust partides below 1 m icron in < of m alignant and non-malignant not be used as a basis for drawing firm length may be just as damaging as dust pirator/ disease. In some instances c o n c lu s io n s as to th e re la tiv e particles containing both large and small ie<e exposure was o f short duration pathogenicity o f different types of fib e rs 41 Cross41 in fo rm e d us that degree was relatively high, there was asbestos in man. One maior impediment in h a la tio n o f th e s u b m ic ro s e o p ic excess o f observed deaths from can- in evaluating the relative pathogenicity asbestos fibers experimentally produced of the lung and pleura and cancer of in man is the fact that m most instances only a phagocytic response; he does not ier sites compared to the number ex industrial exposures are not solely to one believe that submicroseopic fibers are ited Knox, Holmes Doll et al40 type of asbestos mineral but rather to a responsible for the m ore extensive md, m a preliminary teoort, that after mixture of several plus metals and oils biologic changes produced by asbestos. st controls were introduced m a and possibly other minerals It is possible that the relative risks ush asbestos textile p'anr during the There ir e only a few studies which associated w ith fibers of different sizes 50's. the incidence or resoiratory can- 'elate malignancy in exposed groups to a are different for malignant and non- teff from a tenfold excess to a rate smgie type o f asbestos'4 - 19 \to<t m ahgnant changes fu rth e r studies illar to that in ihe general population epidemiological studies that appear to bearing on this matter are necessary incuso and El-Attar " m r study Qt - z cate dnferences m pathogenicity Kleinfeld Messite and Linger41round that lestos workers o b 'e '-e o '-a t the nsk nulmonary cancer .a 'e Z .sith emj.-nent duration n m0v nuances as a - c - g hoes of asbestos contain Haws m f a - --ey lack quantitative data on ,, e v e exposures, riber cha-ac- (he nature of the dust samples analyzed ndicated that liber counts o f aerosols did not provide a true picture of ex level ot cnpiovrment <=*ner ertce hq* HPn mnriaitrv rj e juiniui'M i* s- ;x and presence or co 'acro's '"" *r'T'Ore ll it} (JHtK.UK tO VdUtf ui>'?>fr1' >* posure to asbestiform minerals because i.ucv .ociiedcd `cic i:bCw but ci*j d ^ ~ce'> increased v \11n -egard to ope -it a-bestos Me n- ; =- 3 asbestos as to re at *e ; i " . : e n i c i t v w ith regard to em er m any `m alt a<besto> Mbers and "aggregate riber*" which contained sub d ,MesMte, hiv vman et a l1 observed s or neoplasia stantial amounts o f asbestitorm minerals excess of me,fa' :\ Tom cancer o f the . :e s ,o date indicate that bom namely tremofire and anthophyllue OO -g and pleura among -ale workers ex- '-a c e and size or asbestos iib e rs are In light of recent observations, one -ed to a mixture or talc and tremolue - z~ cant tactors us d e te rm in in g cannot exclude the influence or corac significant increase in incidence ap- esc a.litv deposition, retention and tors on biologic euects as a m ajor deter J1 ared in the oldcvt age group, 60 to 79 c ea-ance rrom the pulmonary react and minant of pathogenicity Dixon, Lowe, CD ars rather than m the middle age thus are im portant determinants ot the Richards el af14 postu/aied that asnestos Oh sup ao to 59 vears Th's was ar s re and nature of tissue response The fibers probably serve as vectors in CO nance w ith then nndings among importance of fiber diameter and length producing disease bv carrying toxic or -J bextos insulaiors exposed to chrysotrle n explaining the disparity in the pre oncogenic substances to vulnerable e rv d amosite whose du-ation ot exposute valence Ot mesothelioma m ihe vortn- sites Relevant studies included analysis ax ,,m ila r to 'hat or Ihe talc workers noeg the a'besio- .-xu'ators there was western Cape and that ot the Transvaal region of South Africa has been of various types oi asbestos to determine components present in each w ith special i mc-eased incidence ot -ung and rural cancers m both middle and streng'nened by the study oi T mb-eil Cnniths and Poolev20 The curiv shape pi emphasis on metals and polycyclic hydrocarbons'4 '> The present con best age groups There was no excess the chrvsotile fiber oners an expiananoo sensus is that contaminants are present carcinoma ot the gastrointestinal tract 0 peritoneum in taic workers whereas asbestos worke-s gastrointestinal and i nneal malignancv was sigmficantlv c eased compared to rhe general inflation, as also obse-ved by Selikoff, i* rrond and Chu'b 1#i 'Scu5sion and C o n c lu s io n - - . - a t studies have been u se rjl m -,Jt -g terra n 'actors 'hat exp am ot its interception by the bronchi especially at bifurcations in cont-ast to amphibole fibers which are needle-like and mav. therefore, reach more deeply into the .ung parenchyma and pleura Since one of the amphiboles, namelv anthophyllite has rarely been associated w ith mesothelioma production tactore other than shape and s.ze must ae cen sidered L n 'it recently, most work and ` D ic tation involved onlv fibers deter'ed h but that identuication or a specuic pathogenetic role for them requires tuither sfudv If subsequent investigations verify that trace metals and other frac tions of the various types a f asbestos dust do in fact play a m aior role m p roducing asbestosis o r neoplastic diseases customarily associated w ith ex posure to asbestiform mineral dusts, then existing standards governing ex posure to asbestiform minerals in the united States and C-eat Britain un - _i ^ ; c acnon or aspt_ai,,, nowese- me o p ric a l or lig h t m ic rOsCOPa doubted'v w ill be ` jb ie c t to revision -trial Occ-pat coal Meitcine-Vol 15 Ns 3 March 1973 299 References 1 Asbevoy The need fo, in d feasibility of air pollution controls Panel on Asbestos Commute on Biologic Effects of Atmospheric Pollutants Washington, DC, Division of Medical Sciences, National Research Council 1971 l Selikoff 11. Hammond EC. Churg I vtor- alny eupswiences oI asbestos insulation work, 1943-1968, pp 180-186 In HA 5heo.ro Ed. Pneumoconiosis Proceedings of .he International Conference, lohannesburg, 969 Cape Town Oxford University Press. 970 3 klemfetd M. Messee I. Kooyman O, *t al vtortalitv among talc mines and millers in New York Slate, Arch Environ Health 14 663- obi ' %7 * Wight CW Asbestos and health in 1969, *m Rev Resp On 10# 467 470. i960 5 -Joit Pf Mills I, Young OK Experimental i'Oes'Osis m -ihe aumea-pig. I Pith fact n ' 85 195 196b 6 Morns 1C, Roberts VVH, Sifverton RE. et al do 2. 205 in CN Davies. Ed .nhaled Pitne'es and Vapours Petgammor Press, Lon don-Pa ns 1969 Murphy RIM. ferns BG. Burgess WA et al tnects ot low concentrations of asbestos, m >w ingl I Med 28S 1271 1278 ' 971 4 Meinfeld M, Messue I, langer AM A study of workers exposed to asbesnmrm minerals m commercial 'ate maruiac'ure To be published 9 Weiss VV C So'.'!? a"d ojlm cna- b-c* s 104 223-227 - s 10 Wagner C C on smoxing Pp*- 'C 5e"\ asbestos ' p ic D't C ?i al Epidem ology o' asoes'os ca"cs-s Snf sted Bull 27 71-76 t i l l Braun DC ' - . a ' r O An eoidemmiogical -. -cs 3t cancer .n asbestos miners 4r;* -<j uieJ -- t7 634-653 1958 12 interline P DeCoufie ? Henderson V Mortai'ty in re'ai c" o occupar.orai exposure I the asbestos rbustrv -ysentea at the xmp.,can industrial Hygiene Conference San 'nc sco. 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