Document 2RDXd4QwKdqdbYKrapM2qea3r

FILE NAME: Friction Materials Standards Institute (FMS) DATE: 1972 Aug 30 DOC#: FMS022 DOCUMENT DESCRIPTION: Journal Article - Health Hazards of Asbestos with Cover Letter to the Asbestos Study Committee August 30, 1972 To: Asbestos Study Committ e e ' Subject: "Health Hazards of Asbestos", by J. C. Gilson Enclosed is an a r tic le "Health Hazards of Asbestos" by J . C. Gilson, Mr. i. H. Weaver, Chairman of the Committee, f e lt th is was a good overview of the e n tire asbestos health situ atio n as i t now stands, and suggested th a t it be d istrib u ted to members of the Committee. CWD/ere Enclosure E. W. D rislane Executive Director CC: B ritish Council AIA/NA (Swetonic) Committee Members M EMO ft am lit* desk aj I.H. WEAVER I think the attached a r tic le g iv e s a good overview o f the e n tir e a s b e s t o s / h e a lth s it u a t io n a t i t now s t a n d s . I su ggest you d is tr ib u te c o p ie s to th e o th e r members o f th e A s b e s to s Studj C onaittee. Ike naa/ut /ta^us uo ut aoL solus J. C. G IL S O N Inhaled fibrs 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 H IS T O R IC A L Asbestos was the first inorganic fibre to be used in com po sites. More than 4000 years ago day pots in Finland were strengthened by adding anthophyllite fibres'. In classical times asbestos cloth was used to preserve the ashes of the eminent. The oldest known piece of asbestos cloth from the Sew World, dating'front about 1740, is a small purse made 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-i: it was not until 30 vears later that the first medical 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 USA5,5 dial 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 nxmed asbestosis. DISEASES CAUSED B Y AS8 ESTOS D U ST Research carried ou: in the 1930s, supported by the greatly expanded investigations during the last 15 years into the types of disease caused by asbestos, now provides a much dearer picture of he specific hazards and how damage to health can be avoided in the future. Table l lists the diseases. TiS.'t 1O iC i i cju*o Ov asbestos dust Ajc-et'. out Ca'-t*' Cs'ni Fiososis ol lungs Bronchial (lung) Mesothelioma Skin Asbestosis In ashostons the dust causes scarring and thickening"! ihc tissues ot !:e lung The two parts particularly affected a"' *. ic fir.cm jir pas-aies ( respiratory bronchioles) ssitoic the;, b'jr.cii into the terminal air sacs (the alveoli), and *S-c s mace oi ;iiv lung (pl-cuta) The thickening of tlu* ii"uc-. T -.iJ :> me 'cuos dust affects me function o' :f.c : 1: in i- ss.is... IT,- volume when mils mfuteJ i* 'i c v i- 1 - '.i i .!>; ... m 1* less Ilian noiniai. Mu- ' '-'.iO ..`tiii'M' t nit. l l u u t ' i ' i , '!; i'.:i 1.1, : I ; I. I \SS . t X become stiffer than normal so that the compliance is reduced. The thickening in the alveolar walls, when the disease is extensive, also reduces the gas transfer for oxygen, so that the blood leaving the lung is no longer fully saturated with this gas. The transfer of carbon dioxide from the blood to the air in the lungs is not, however, appre ciably affected. The reduced oxygen transfer is partly compensated for by an increase in the frequency of breath ing so that the subject notices breathlessness on slight exertion. These alterations of lung function are used to assist in diagnosis o f a sb e sto s and measure the seventy 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 o f being afTectcd. This-lose 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 a practice. Prevention by avoiding exposures to 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 beiwcen asbestosis and lung-cancer. A survey in 1955 firmly established that those who had worked in the asbestos textile industry before the improvements in dust control, introduced in the 1930s, had a 10-fold excess risk of developing lung cancer5. The survey, however, also indicated that the improvement in dust control introduced at a particular factory after 1933 had very materially reduced the risk. Later surveys at this factor)' have confirmed this6. The lung cancers seen in asbestos woikers are similar lo those caused by cigarette smoking. Recent research imiicaics tlui there is likely to he a synergistic effect of cicarcttc smoking and exposure to asbestos dust1. The precise quantitative inier-rclationship between asbesios. mcaroucs. and other factors is not fully established, but present evidence indicates that those who smoke cigarettes a n are exposed 10 asbestos dust have a risk of developing !.: a cancer at least fifty tunes etcater titan tum-sniokets v. i, ' `ire not e\poM*d lo asbestos dust. In the last 15 se a ts thete has been m uch new in fe rn u - I'otii the huk betw een exposure to ,isbc<to< m l i. u!:-.! prcv;..u>ly vers rare type of cancer aftectnip me Ui< last 10 years. There is general agreement in most industrialized countries that there has been a real increase of t-.is form of cancer*. In about SO', of cases there is a history of exposure to asbestos dust at some time in the past. A feature of these tumours is the long interval between first exposures to asbestos dust and the detection of the cancer, it is rarely less than-20 years and may be up to 50 or more years. In some instances the exposure to the dust has been shorn only a few months, but the highest incidence of turnouts lus occuired in those most heavily exposed to asbestos dust. Cigarette smoking seems to play no part in these tumours, but some research workers think there may be oilier co-factors present as well as asbestos10. The only other specific injury caused is the formation of asbestos corns on the fingers when the fibres lodge in the skin. The removal of the fibre usually cures the corn and no cancers of the skin relatable to asbestos have been teported. PRACTICAL IMPLICATIONS OF THE BIOLOGICAL EFFECTS OF ASBESTOS Inhalation o f the fibre For all practical purposes the risk from asbestos is limited to inhalation of the fibres. Thus control o f the airborne dust levels and their monitoring by instruments, which will measure that pan of the dust which can gain access to the deeper parts of the lung, is an essential sup in the safe use of aU types of asbestos. Although asbestos fibres can be ingested in minute amounts in beverages which have been filtered through asbestos, or water supplies", there is no 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 or other cancers. Sue and shape o f fibres Recent research has helped to clarify the probable influ ence of fibre length and diameter in producing asbestosis and the bronchial cancers. The fibrosis is thought to be caused principally by the fibres between about 5 and 100 pm ir. length. Fibres much larger than this in the environment settle out quicisiy and are not inhaled. Further sue reparation occurs n the air passages, the important sue parameter being fibre diameter since it is this dimen sion rather than fibre length that governs the failing speed of the fibres. Thus fibres greater in diameter than about 2 pm (These also tend to be the longest! mostly fall or impact in the upper respiratory tract and are carried away with the 'putuin. In the narmw airways any long fibres remaining ;ire deposited by interception 3nd fibres longer than about 1QU pm seldom teach the I'iucsi bronchioles T!n< tncjt.s iltat for the control of asbestosis. and probably bronchial cancers, the dose of fibics between about 5 pm and 10.) ,n length and up to about 2 pm in diameicr i> the iracti-'t. of the Ju-t winch.ins to be measured. l or ->i mesoiheii nttas the evidence about the bio logical! mpyrt ani x.-c is imieh l o> complete t'oi-.g imorin.at r l u- m many sources. Mich as the aeio-.lynjnuc hch.M >1 fmc l h' : . ' v the s>/e and s l up- ot fibics winch ue let.*,nr.I r, hangs ol ai ni na' ' .ms! man lollo'.wng cxpos ai e to d . t t c i e o - t ypes ot asbestos. ml the epi- . i --------------- P 'ooaote Uiat iUc important fibre re likely to be those which are sif;-eht small in diameter (up to about I pm) and perhaps JOpni in length. It is not vet known whether the ultra-fine fibre; only visible under the electron microscope are bioloeicalK* important. Such fibres are present in large numbers*in the lungs of those who have been exposed to asbestos, but their combined mass is extremely small, h is too early yet to use tins information to establish with confidence a separate dust standard to prevent the development o f these mesotheliomas. This is a field of intensive research at the present. Some of the new evidence suggest* that the size and slupe of the fibre are more important than its chemical composition, provided it is relatively insoluble. It may be that extremely fine fibres of many different materials cam penetrate cells without immediately killing them , but once inside can damage the mechanisms of cell divisions. An implication cf this view is that cate should be taken to avoid - exposure to dusts o f all types of fibre less than 0-5 pm dia meter and several micrometres ir. length. 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 o f the workers within the industry. Eatlier medical reports did not differentiate between one type of asbestos and another, and most of the surveys were concerned with asbestos textile wutkers. A full assessment of the risks would ideally be based on studies of workers only exposed to each type of fibre and tn all die operations within the industry in which this fibre was used. In practice the information is much less complete than this. Exposures to one type o f fibre have usually occurred only in the mining and fibre separat ing. This work usually takes place in countries where the medical records are scanty and the labour turnover is rapid. A notable exception is in the chryjotile msies in Quebec where a very comprehensive survey has just been com pleted"-14. In the manufacturing countries several types of fibre are often mixed together or have been processed concurrently so that employees have been exposed to several types of fibre in unknown quantities. Past records of dustiness are raraly available for reiatma to the incidence of the diseases. Thus the current assessment of the relative risks in the past from different types c f fibre and occupa tions is based on information winch is far front complete. Use can be made of experiment in animals, especially rats, because most of the diseases seen in man can be pioduccd in these animals. New information is rapidly accumulating which may me a clearer indication of the way in which different types of asbestos produce their biological effects. There is general agreement that asbestosis ar.d bronchial .an.ers can be caused by ill types of commercially used asbestos(amositc. mhophylhte. chrysolite, and crocidolite) if ilie dust is inhaled in sufficient quantities, but it now wans likely that the risk from chrysutilc may be less than will; tlie utlie: t>pcs of fibre. There is also evidence that the ri'k is lowest tit minim; and increases nlottg the fiote wpa: j i me and ;r._nui jcv.itu.g procC'WJ. T h is is thought to tie 2 u' !> the higher propot imn oI hhImimic dust consist mg il'i. Iilu.-' able to penetrate into the d eep est p n t..c I'mg. In pi.ntice tins means that the cleaner .he t:iwc : : t j ilte t *. a c-mp-lcicly u is sepat jied m io m J iv ta w .il good evider.c-i - do ierponse relationship fur asJicstosiJ and broncfcti' csfl-'en ar.i thus. if the dust level* are kept within the n r- s:cr.-a:it. the risks of asbestes'.s and bron chial cancers ir :h: f-f-:e ;ouid be very small. The risk c:' fkii'ptr.i mesotheliomas has a different relation to fibre `.vpi. I: s probably highest with croodolitc and k west w."*. c'r.ryiv.f.*. S o caser clearly related to aiuhrphylkte hate been reported, despite careful search. TV.: ns-: w::h amosite probably lies between crocidalitc ar.a cr.-yvjtili. Tire evidence for a dose response relationship is less clear ir. the cave of mesotheliomas and hei.ee tits ihrrsi.c.d hm.it value i* more difficult to assess. In the Atberos Repletions I9(i9'* the standard for ciocidolite is is: a: one-tenth of that for other types of asbestos. COMPARISON C F OCCUPATIONAL RISKS What is the rr-cjr.itu.ie o f the risk of developing ill-health from asbestos? So rincJe index provides a satisfactory measure of injury to health. Thus the excess risk of death before a specified ace may be a useful index for tc.ose diseases causing sudden or tapid death, but it as an inappropriate index for diseases causing a lone period of disomiity uut li.i.i slio.tv.n..;g of life. The cancers associated with asbestos exposure fall into tltc first group and asa-rrosis the second group. In different occu pational greurs ecntpa.-isons of mortality are easier to make than those of ilir.evs. 3u: even for mortality the compari sons are no? r-raightferward. For example, the more the selection is Icrtitid to a definable group with a high past exposure, the worse the risk will appear. Allowance has also to be made for tr.e effects of age, length of exposure, and how lone the occupational croup Iras been followed. When such a"owar.ces are made the excess mortality from `all causes' in grreps of workers heavily exposed to the more jr-acmc types of asbestos dusts in the past is closely corr.pi.-2Ce to a ; of coalminers who have developed the severer farre of c.rai-orkers' pneumoconiosis or that of deep-sea f. ih:~.er. who have the highest rates of acci dental tie.::ta cf any occupst.on. However. the excess mortality fre- ; `alt causes' in these occupational roups is less than 2-.d. c: cr.a : .-T ick ers of twenty cigarettes and -irr :i C3` ; T'::,:s is red -;L `. : it-t~.i.l:eri. : : : r.r. :'.t d iu '.its frvtm 'ali cau' es- hut di : t `- f:cr. "hr:. such a mesothelioma ashes- to S::. or i.-.: . ::s :: ause tv t. at of tlie genera P'..hi ie . di ; .: cow.*.s r*r / . . r::eiy much more increase J. Tins IS bt: -:>i i . ` mai a r i a'hcsioji arc ext rei:mx\ ^ rare tn .\ *.. . ; ; * . v. vked witli aabestur. C 'ill j.Mon fr- times . e\ p id '1'.`j 1j ; * ^ the rti'portuin of in^*1\ id'.i.ils ...p a d.sca-i and the excess :isk ol j * : ; r : ; i h.J'-. duals compared a r:h the -si fn-* id lite seco: d c.\ :.~- : THE P U T _ Tf As \:\ i;i.--. t'.CA P1 curii: j :- : r .; d :;.-rs prool vf ilio ef i.'aey of :-a.: :r;;t i!ie s'ahil ns ol 1tic .>. .a: on!s c>-::ie Ito:"1 ilMMllC *. : t: . tvtIt::a. 11iri::v P't'CCN' . 1 nuierul s used in* mej* exposed, (,'umpui. now make it easy to store th a information, hut we still need the foresight and adimnistration to see that it is achieved. If it is not dene wc may still Li dO years or so be in no better position to answer im ponani questions which ate at present unanrweiablc because o f the paucity of past records. C O N C L U S IO N The recent increase in the number of cases of asbestosis and other diseases related to pasi 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 Asbcsios Regulations. Much new information about the biological efTects of asbcsios has been acquired recently. The new Asbestos Regulations 1969 based on this information, if correctly applied, should gtreatly reduce the risks in the future. The selection of which types of asbestos to use in new processes should 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. Wien working with extremely fine fibres o f any material which may become airborne, caution is needed. Aj> exami nation of the possible biological effects is required if the product is to be widely used and risks of damage to health arc to be avoided in the future. Proof of the efficacy of present preventive measures depends on much better record keeping than has been the case in the past. REFERENCES 1 Noro Leo. American Indurial Hygiene Association Journal I ol 29. p l9S(l9hS> 3 Merc ether E. R. A. and Price C. W,, `Report on the effects of asbestos dust on the lungs and dust suppression in the A<ticsios Industry'. London. HMSO (1930) 3 Drccsscn W. C , DsllavaiJe ). M,, |-.d*ardt T. I- MiUex J. W,, Sayers R. R., `A study of asbestosis in the asbestos textile industry'. US Treasury Department. Public lle.iiu Sen ice. Public Mealtit Bulletin No 34 1 (August 19 3SV * Mctovcthet F,, R. A. Annual Report. Inspector o f factories, London, MMSO H 9 i' l 5 Doll Richard. Prmsr. ir-'.--r! of ndusTris! Medicine, i'oi 12. p SI (1925) ( Kito\ J. ).. Holm-.-' S.. Doll R., and Mil' I. D., Smisti Journal of hiJustua! M , - J i c : r i ol 25. p 29.; / 19nS; ' Sclikmi' I J.. Jikm;-.' nj the Americsn Medicai Association. I #./ 2nd. p I Hd / vr ` ' Wjeiu-r J. Cil-or. J. C... Brrry 0 .. ir.J Tunbrell V.. Hnttsh 'I.-Jiijl Unitetin Vn:2~.p 71 I l 9 ? h 9 Gilson ). `Astv'io health hazards', in Shapiro. It. A. (editor). 'Pr.ouinoeur.!.->M<'. Ptoeevvlin-s of the International Conteren.-e, Johanr. .-sbur?. 34 A rn l-3 May )V69, p 173. t ipe To* n etc.. Osicrd University Pievi (19 30) !0 't eti*iei I.. Asbcsios c\pvurv in Ss'utl. Afiica'. thtJ. p ) 30 I I t'unr.undiain M.Ni. and Pontcfraet R ..,\ature. I of 2J2. p SS2 M V 71) 13 Pei Male Margaret R.. foumict-Massey Cisoie. 'k Donald J. C . Sicnuatycki ).. ir.d Rossi ter C. K.. fiulletiti d e Physio- Pul/to/opc Rtqii'ctnire. i'ol n. p r-J7 f/V'ri) I ` M, Donald J. Corbett. M.Dotiattl Alison D., Gthhs Graham W,. . Me'nuis In JaeX. i::d Kossitcr t hjilcs la., Atciurcs of / . ;,i 'inn itij! Ile d n- VoJ 22. p n77 r19? 1/ ia loJom tulle. (u'in. (t \V , Ma.lsleri P T.. MeDonald 1. C.. IC si.ik., , I ; r1 im.-i.on K .lin r o f HespiralP'y in : > ` _V is M .ii'.nv Instiu! .. lih 'i Xu W , I'jrtniies. 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