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4 ' FRICTION MATERIALS sr'VRDS INSTITUTE,INC. E-210 R0UTV4, PARAMUS, N.J, )7652 11 August 30, 1972 To: Asbestos Study Committee' Subject: "Health Hazards of Asbestos", by J. C, Gilson Enclosed is an article "Health Hazards of Asbestos? by J. C. Gilson. Mr. I. H. Weaver, Chairman of the Committee, felt this.was a good overview of the entire asbestos health situation as it now stands, and suggested that it be distributed to members of the Committee. EYiD/erc Enclosure VS CC: British Council AIA/NA (Swetonic) Committee Members E. W, Drislane Executive Director VABEX-123 SCF-ALLF-04190 MEMO bam Im dtti a] I.H. WEAVER I think the attached article, gives a good overview of the entire asbestos/ health situation at it now stands. I suggest you distribute copies to the other members of the Asbestos Study Connittee. . Ike Health Hazards of asiestos c.j. GILSON Inhaled.fibres of asbestos can cause fibrosis of the lungs and two kinds of cancer. Protection of asbestos workers calls for monitoring and controlling their working environment and linking these records with records of their health HISTORICAL Asbestos vis the first inorganic fibre to be used in compo sites. More than 4000 years ago clay pots in Finland were sttenglhcned by adding anihophylliie fibres'. In classical times asbestos cloth was used to preserve the ashes of the eminent. The oldest known piece of asbestos doth from the Sew World, dating Tront about 1740. is a small purse mad: of tremolite in the Sir Hans Sloane collection of minerals in the British Museum (Natural History). The modern asbestos industry is about 100 years old, starting nearly simultaneously in Canada and the USSR, fc't: it was hot untf 30 ears later that the first medial reports appeared in France and England, indicating that there might be a specific type of damage to the lungs following inhalation of the dust. By the late 1920s it was clear from surveys made in this country and in USA1-1 that a high proportion of older workers in the asbestos textile industries were becoming severely disabled by a specific type of chest disease due. to the dust. This was named asbestosis. .. DISEASES CA USED 8 Y AS8EST0S DUST Research carried ou: in (lie 1930s, supported by the greatly expanded investigations during tiic last 15 years into (lie types of disease caused by asbestos, now.ptovides a much dearer pir.uie of the specific hazards and how damage to health can b: avoided in the future. Table I lists th: diseases. Tliit I Quitfj siuito by ubtnoi dun Aimiiow Ci**ee' AitXV.S! Coins Fiurotii of lungs 8'oncftiji Oungl Mftoiheiiofnj Skin Asbestos/s In asViti.vls the Jus: causes scarring and iliickeninc .>! the invito ui :!;c lung The two pans particularly aliocieii s".' :m: fii.rs! air pas-agci (respiratory bruttcliiolesl wi-.eic the;, b.'jr.ci-. i: :c the ic.'min.il w sacs till.' alvc.ilii, and th; .s::u:e n- ;h.- lung (rleuial. The thickening ofilie d-wic-. :: fu.vc by the Voceiui dust ali'ccls me limclioi. <>' rite ::: m.m- IT:-.- minute when fully i.'ilIal.'J v li..' - :-u' u-i hi I- le's ilun numiai. Tin- t-.s-c-.s * i-t.i.i : '-INC (*mi. I (.liuWi;-'; jj t'.T. became sliffer than normal so that the compliance is reduced. The thickening in the alveolar walls, when the disease is extensive, also (educes the gu transfer for oxygen, so that the blood leaving the lung is no longet folly saturated with tltis gas. The transfer of arbon dioxide from the blood to the air. in the lungs is not, however, sppreciably affected. The reduced oxygen transfer is partly compensated for by an increase in the frequency of breath ing so that th: subject notices breathlessness on slight exertion. These alterations of lung function are used to assist in diagnosis of asbestosis and measure the severity of the damage. Asbestosis takes a number of years to develop, even under very dusty conditions, but once established it is a progressive disease not materially affected by avoiding further dust exposure. The less the dust exposure, the longer interval before the onset of disease, the less its severity; and the less chance of being affected. This-dose response relationship is used to fix the acceptable dust levels - threshold limit values - for those working with . asbestos. The article by Holmes in this issue describes how these standards are applied n practice. Prevention by avoiding exposures lo a dangerous quantity of dust is an essential step towards the safe use of asbestos. Asbestos cancers . Some years after the recognition of asbestosis as an impor tant problem in the asbestos textile industry, articles began to appear in the medical journals4 suggesting an association between asbestosis and tunc-cancer. A survey in 1955 firmly established that those who had worked in :k: asbestos textile industry before the improvements in dust control, introduced in the 1930s, had a 10-fold excess risk of developing lung cancct5. The survey, however, also indicated that the improvement in dust control introduced at a radicular factory after 1933 hid very materially reduced the risk. Latct surveys at this factory have confirmed this4. . The lung cancers seen in asbestos u-oikers are similar to those caused by cigarette smoking. Recent research indi cates that thete is likely to he a syncigistic effect of cigarette smoking and exposure to ashestos dust1. The precnc quantitative inlet-relationship between asbestos, .tpreiio. .md other factors is not fully established, but p.vwni evidence indicates that those who smoke cigarettes i:-c arc exposed to asbestos dust have a risk of developing !i::.: cancer ,il least fifty times (dealer titan ncn-sniokeis vi; '.W not expused to asbestos dust. . the iaM 15 years ilieie has been much new mfeima- tw:: al-ou; ilu- hut. between expo-ur: to asbestos and nt-i-Vc: prev:.,(i,|y very tir: type of cancer jfleenng ilic "suffice of the lung and the gut* RepOfts of these meso- demiological studies of the incidence of these tumours in tl.cliums is they arc called lu ncrcascd steeply over man for differ' ypes of fibre, it seems probable tint the tie list 10 yeats. There is general agreement in most important fibres are likely to be those which ire straight, industrialized countries that there has been a real increase of Us t'omi of cancer*. |n about SO1,* of cases there is a small in diameter (up to about I pm) and perhaps 10 pm in length. It is not vctltnown whether the ultra-fine fibre: history of exposure to asbestos dust at some time in Use only visible under the electron microscope arc biologically past. A feature of these tumours is the long interval important. Such fibres are present in large numbers in (he between first exposures to asbestos dust and the detection lungs of those who have been exposed to asbestos, but of the cancer, it is tareiy less than 2D years and may be up their combined miss is extremely small. It is too early yet to 50 or more yeats. In some instances the exposure to to use this information to establish with confidence a the dust has been short, only a few months, but the separate dust standard to prevent the development of these highest incidence of turnouts has occutred in those most mesotheliomas. This is a field of intensive reseatch at the heavily exposed to asbestos dust. Cigarette smoking seems present. " to play no part in these turnouts,but some research workers Seme of the new evidence surgetis that the size and think .there may be oilier co-factors present as well as sliape of the fibre are more important than its chemical asbestos10. The only other specific injury caused is the formation of composition, provided it is relatively insoluble. H may be that extremely fine fibres of many different materials can asbtstos coins on the fingers when the fibres lodge in the penetrate cells without immediately killing them, but once skin. The removal of the fibre usually cures the corn and inside an damage the mechanisms of ceil divisions. An no cancers of the skin relatable to asbestos have been implication cf (his view is that cate should be taken to avoid repotted. exposure to dusts of all types of fibre leu than C J pm dia" meter id several micrometres in Iciigiiu PRACTICAL IMPLICATIONS OF THE BIOLOGICAL EFFECTS OF ASBESTOS Inhalation cf the fibre . For all practical purposes the risk from asbestos is limited to inhalation of the fibres. Thus control of (he airborne dust levels and their monitoring hy instruments, which will measure that part of the dust which can gain access to the deeper parts of the lung, is in essential step in the safe use - of all types of asbestos. Although asbtstos fibtes an be ingested in minute amounts in beverages which have been filtered through asbestos, or water supplies11, there is nu firm evidence that such tiny traces have any ill-effects. Feeding massive doses of asbestos to animals has so far failed to produce any mesotheliomas ot other cancers. Sue and shape ol fibres Recent research has helped to clarify the probable influ ence of fibre length and diameter in producing asbestosis and (he bronchial cancers. The fibrosis is thought to be caused principally bv the fibres between about 5 and 100 pm ir. length. Fibres much larger than this in the envirenment settle out quickly and arc not inhaled. Further size .-eparsUoit occurs in the ait passages, the important . size paramefe: being fibre diameter since it is this dimen sion rathe: than fibre length that governs the falling speed of the fines. Thu< libies cieaicr in diameter than about 2 pm (these also tend to be the longest I mostly fall or impact in :h: upper respiratory tract and are carried away wiih the sputum. In the nariow airways any long fibres remaining arc deposited by interception and fibres longer than aboa: IfJU pm seldom teach the finest bronchioles Tins means that lor the cuiiimI of asbestosis. and probably bronchial cancers. `.In- doss- of fibres between about 5 pm and Ili-.l ;:.v. ;n lengih and up to about 2 pm in diameter o ihc fiaen-:: of the Jus! which lus to Ik measured. l:o: m-CMiilicii.itr.as the evidence about the bio- h'CiCiiis :r.:pj:l:.at :.:/C is much less complete. I sing i:n.'.'i::;i : r lu-in mans' sourcs's. 'iicli as iltf aerodynamic hcli. si.-.:: .0 fine f;i'ills' we and sliap. o! fibk's sslncti oe ici.i,:r, lungs of anuna'' am! uijii tollo-.sing C.vp.Kue lo d.licivii: types ol asbestos, and I he epi Types of asbestos and occupations within the industry The last 10 years have shown the importance to health of the type of asbestos inhaled and the occupation of the workers within the industry. Earlier medical reports did not differentiate between one type of asbestos and another, end most of the surveys were concerned with asbestos textile wutkers. A full assessment of the risks would ideally be based on studies of workeis only exposed to each type of fibre and in all the operations within the industry in which this fibre was used. In practice the information is much less complete than this. Exposures to one type of fibre liave usually occurred only in the mining and fibre separat ing. This work usually lakes place in countries where the medical records are scanty and the labour turnover is rapid. A notable exception is in the chtysotile mines in Quebec where a very comprehensive survey has just beet: compitted11'1*. In the manufacturing countries several types of fibre are often mixed together o: have been processed concurrently so that employees have been exposed to several types of fibre in unknown quantities. Past records of dustiness arc :a::!y available fin reining to the incidence of the diseases. Th.us the current assessment of the relative risks in the past tiom different types cf fibre and occupa tion! is based on information which is far from complete. Use can be nude of experiment* in animals, especially rats because most of trie diseases seen in man can be pioduccd in these animals. New information is rapidly accumulating which may give a dearer indication of the way in which different types of asbestos produce their biological effects. there is grucra! agreement that asbestosis and btnnchial cancers can he caused by all types of commercially used jshcstiisliunositc.inthopltyllitc. chrysolite, and crocidolite) if the dust is inhaled in sufficient quantities, hut it now wems likely that :he nsk from chrysolite may be less than with the otliei types of fibre. These is also evidence that the tik-is Iimesi in inuiini: and increases .along site fibre wrauiiiic and ir.j.nii'j.-iuiiiig piueerj. This is thought to Ik die in ihc higher piopiiituiu s>f auKmic dust consul inn ->i .ihic IiI i.k able i,, penetrate mill tfic deepest pvi " li e lung. In pi.niicc lilts means that the cleaner :!ic and the m-uc e-rup-leiely n is wpauied tutu individual K't aj iJaS.n. Lie greater N risk. Thtie is also sod evide.-.di - dof: Ksronse relaiivJnsltip for aslicstosis '4 bronchi- -r.:cn and thus, if ihc dim levels aie kept ilhi.* Iht it*.'- 4'.:'dr.is. the tisks of asbestosis Jisd htott- sii) cancer:=:ou'.d be very irnaJl. Fr: risk c:' ir-mesotheliomas ha: a different :!.iuun toftF: ':7`- ' ptotebly highest with c/ocidolUe -d h-west So caser clearly related 10 ithcphyl!;:: have b.'cr. reported. despite careful -itds. Tit: v& :mo-;tc probably lie: between oeidaliicar.: er.-yvjiile. The evidence for a dose response letic.vship 2 lets clear ir. the cave of mesotheliomas and nice the ih:r..':d l-.it value is more difficult lo assess. > the Aihrsces Regulations IW)15 the standard for ocidaliie is >:: at of.e-te.iih of that for oilier types of sbestos. :OM?A RISOK OF OCCUPA 7ICNA L RISKS That is the :r.2riit;de of the risk of developing fll-liealtlt forn asbestos: So single index provides a saiisfaetory a xasure of injury to Iiaalrh. ' Thus iht excess risk o: death before a specified ape may i useful index fo: cose diseases causing sudden or tapid eath. bus it is a ir.apprcpriate index for diseescs eausinp long period o! iiaoi.ity but luiic shutunat of life. T! anccrs associated with asbestos exposure fall into the first ami; and asbestosis the second group. In different occu- aaticna! gs.-jp c.'.T.pa.isia.is of mortality are easier to make han those of illr.ass. But even for mortality the contpari- ions ate nar Sraightferwsrd. Fot example, the more the .election is limirsd to a definable group with a high past xposure, the verse the risk will appear. Allowance has also to be made for the effects of age, length of exposure, id how Ions die occupational croup ha: been followed. When such sc.owjsets ate made the excess mortality from `all cities' in groups of workers heavily exposed to the more di.ricn: types of asbestos dusts in the past is closely corupLib'e to that ofcoalminers who have deveioped the severer turn of cnalworfcers' pneumoconiosis or that of deep-se: f.sht.-mer. who have die highest rates of acci dental deu.ru c: ar.y occupation. However, the excess mortality tree-: ':!i causes' in these occupational groups is less than shat vf male smokers of twenty cigarettes and wore a cay c: .I'.: died it;-, noii-or,niters. Ti::s :: r. c:: '.its ftitm 'ali causes', but d;:i! .i f;cr. a. ??;. Vduh :i mesntl'Clinin.:. u>bcs- ICil:.. or i::; f col:k ;e:s:.' tv ti.at uf the senctat ptibiic. "ut.lt more increased. This t3 bf. : "a- :rJ ;> hcsinsis ;::c extremely rate in :!. .V. ... - i*.: '.: v. -rM with asbestos. (.miumiwi (xjn* :n;i* ^7. tl'.i -ti'portuir. of indiv.dtitils fApu- ed v-m if.-.. ` f J WtKu.'a jr.d Hie excess risk id a r-t'f i 'iju ' . .t- . r .duals cumpated -.visit the ge.-.d: ** it: may be relatively smtili and the see tv.'. 0 cn:::-- :*; : TH: PUT. *f At It: m.-t . d.:2a-r proof of the efficacy of : pi-:*..- . . . :: ;.a.::ii; ilic t'aliiluv <>l die ' ' . ;'L tttiV' -; : : ok!) -::u- im;i r..: muourjciuin:; ptoccst ar-c :. * '. . J tualvruls nwd. tiv mo- suteinenis of ex^^jre; the medical recoids of those exposed. Compui. how make it easy to store (his infor mation, but we still wed the foicsiglti and administration to see that it js achieved. ff it is no; dene we may still li '0 years or so he in no better position lo answer important questions which are ji present unansweitblc because of the paucity of past ttcotds. CONCLUSION ' The recent increase in the number of cases of asbestosis and other diseases related" to past exposure to asbestos is the result of relatively heavy exposures to the dust, particularly in parts of the asbestos industry not covered by the 1931 Asbestos Regulations. " Much new infonnalion about the biological effects of asbestos has been acquired recently. The new Asbestos Regulations 1969 based on this information, if correctly applied, should greatly reduce the risks in the future. ... The selection of wh ich types of asbestos to use in new ptocesses mould take into account their biological effects if the risk of dust exposure is likely to occur during manu facture or in the use of the products. When working with extremely fine fibres of any material which may become airborne, caution is needed. An exami nation of the possible biological effects is required if the product is to be widely used and risks uf damage to health are to be avoided in the future. Prouf of the efficacy of present preventive measures depends on much better record keeping than has been the case in (lie past. REFERENCES I Noro Uo, American Induurul Hygiene Allocation Journal, I'oflV.p Its (H'nS! 3 Mem ether E. R. A. ir.d Pikrc C. W.. 'Report on the effects of asbestos dust on the lungs and duss suppression in the Asbestos Industry'. London, HUSO (1910) 1 Drcetscn W. C, Daili'-aile J. M,, ltd*aids T. L. MiSer J. Vf.. layers R. R., 'A study of asbestosis in she asbestos textile industry'. US Trcasoty Department. I'ubiic llealtls Serv ice. Public Health Bulk it.-.So 1411 Atfast 193SV 4 McicwcUict F.. R. A. Annual Report, Inspector of ffactotiex London, HMSOll9i'!| . ? Onll Kiclurd. Mtith Icjrre! of`.nJutzisi Hedkint. Vot pSIlltSSl l- Knox J. )',, llolinoS. Doll R..111J llili I. D.,Srilim Journal vflnjinttia! fh-Jin': '. I'ot 2S.p 2V.!/ftrn.f; ? ' vliknil' I. i.. JiiinS. n; the Anit-rkcn McJicat Auoefeuon, fnl 'ii-l.p HU Ivr'- k Wactier I. ('.. Cil-ot: J. C. Deny G.. and Tunhretl V.. Hritiih tt.'./uj/Hulltiin l'n.',\'./i r/f/v?// 9 O'.hon I. (,, ',t<lv-:u` aiiltli haaarjt'. in Shapiro. 11. A. teJtttiri, 'l*r.euinoci.:.!.'<i<'. hocrediiip of the Inlemalioiul fun'.'etenee, )nSinr.:tcs;. 34 Apnt-1 Stsy IV60, p Hi. t'rpe Ton etc.. Oxford L'niverutt VievlUIOl !L '.'eb-tet 1.. Ashctio- rvpc'urv in South Africa". iHI. p ! 13 11 ( unmiidtam II. V., and 7unsciraCI K...Vamre, I nf 232.? JI!<>:/) 13 IteeUaLe Matcarct R.. rcunuri'Masser Cisclc. V.cfloitald I. l\. Stcmtaiyrki J., and Hii.niet C. E.. flulletin do rhyrio- PaiMuftr Ren"'cinire. loln. p t.J7(t(/<l/ le MeliunaMl.Corbett.sfrUotuld AlwnU.,CihhsGtahani ,NK*muiukt ar.J Ko-Miet (hailet E, Aitiurcs of / ill ifr-'H'la ff/j/ tvfit7ii . f. tV.. Mj.-ller.i r. T.. MeDonJJ ]. C.. IL. Al.(U V.jij-ai. ; r 1 h.m.an K'.vkm* of tUa it,*, * Hi lN Sisihi'aift In'Uut Hi.'i N.i null. I j.-lmire The <N-oO' U . 1*MN | ::.l .n. HMStillVi.li