Document emErB2dz0LgXzE3bmDjvx44oq

Section of Epidemiology & Preventive Medicine freshen! J N Morris f Rcr / Meeting 10 February 1972 Michael Williams Lecture Asbestos Caneers Past aud Future Hazards [Abridged] . : . . by J C Gilspn prcp ' . .. {MRC Pttcnirsocoiuosis Unit, . L'at.laughIfc.'xi.'rJ, ' ' Penarth, - ' ' ' Glamorgan) ** Michael Williams was for a while one of my colleagues at the Pneumoconiosis Unit. It is just ten years since he was so tragically killed in a motor accident at the age of 44. lie would have wished that a lecture in his memory should include a `discussion*, as he rarely attended any lecture without contributing to the discussion in his characteristically charming and enthusiastic manner. .* . . I remember the joy with which he described to me the facilities JC1 had provided for him, and being surprised at their extent as he had only recently joined the Company. I did. not realize then that the rapid support he got was due to bis quite exceptionally wide understanding of the engineering, chemical, and rrxdicul aspects of his work; also, his flair for spotting new risks. No one intent cn delaying his proposals for preven tion had much chance of outwitting him. He is rightly commemorated; he show ed how* much can be achieved by an industrial medical officer who is able to learn all about, the processes in his factory and reach a stage where he can talk on equal terms with all from the research department to th c faciinry fioor. P revie- us lecturers (Dodds P.ovl,md ! 9w*7; Cttse 1559, Forrest 1971) have cescriirrd his c haracter:and contributions to know in 2dn::r;able det.n! 1. w;-s.cn he h.-.d cs: itblished himself as a leading Ctr<T t on clhemirai icaruir.oge ns he received much help!'ram aeintern.-.liona! L' nio.n .Against Cancer (UJCq: k,: visited many eo entries and by 1961 six out of the nine countries where ^-naphthyl- amine had beer, made had stopped manufacture or were about to do so. , . The part the UICC took in assisting the prevea- - tion of chemical cqncers through. sponsoring Michael Williams's visits docs not seem to be well recorded. The same may be true of t heir assistance in stimulating worldwide interest-in the .asbestos .Cancers. I welcome this opportunity to record briefly the help my colleagues and I have received, fust from the UICC nr.d later from the Inter nationa l Agency for Research on Cancer (IARC). In 19(53 Dr T F Mancuso, who has had a long .. interest in occupational cancers, wrote to Dr J C Wagner suggesting that an international effort be made to investigate further the cancers caused by asbestos. Y.'ith the help of Dr W Gardner, now president of the UICC, and the Anna Fuller Fund, a UICC Working Party on Asbestos Cancers (chairman - Dr H Stewart) was held in New York in 19&4. A number of the recommendations at that time (UICC 1955) have now been achieved -- for example, the preparation and distribution or standard reference samples of asbestos; the development and testing of ?. classification of the radiographic appearances of asbestosis; and the setting up nationally and internationally of pane}s of pathologists expert in pulmonary' tumours. Since 196S support for international investigations in asbestos has been provided cy the IAR.C as part of their ccr.arai .'.iOgranimr on environmental carcinogens. We have received great help from Dr J Hieeiiism (the director) and from Dr P P.ogovski. A grant from the 1ARC through the ' MRC has led to investigations and research pro jects cn the asbestos problem in eight countries. The industry has made important contributions through the Asbestosis Research Council io this country and Us-.* Quebec Asbestos Mining Associa tion in Canada. The Royal Navy- 5ms taken :t leading part in reviewing rise use of asbestos and BX-339 396 Proc.royf A U-J. Voluri'C 66 April 197J 't-t llistoricdl Asbestos has r.'Tor.g history; it has been used for about four thousand years, but up to about a hundred years ago it was regarded more ns a treasure than n commercial raw material. In 1725 Benjamin Franklin - inventor of the lightning 'conductor, -bifocal spectacles, and the harmonica -gave the oldest known woven asbestos articlea small purse made of tremoliie-to Sir Hans Sloar.e. Sir Hans, a physician and great collector, sold his treasures to the nation. The purse is still on show with the rest of his collection of minerals in the Natural History Museum. -------About a hundred years agjLthc.asfca5h3SjndQ.Sn try proper started, following the discovery oflarge deposits of chrysotile in Canada and almost , simultaneously in Russia. Other types-the so -called amphtboles -- were discovered principally . in South Africa and Finland. It was about fifty . years after the start of the industry that lung cancer was first thought to be caused by the dust (Fig 1), about another t-.n year; before this was generally thought probable, and a further ten ' before it was finally established in the asbestos textile industry' (Doll 1955). The first reports of diffuse pleural tumours linked with asbestos appeared in the early 1340s, but there was an interval of about fifteen years before this associatiorvwas generally thought probable, and another ten before it was widely recognized in ail countries. It now looks as though history may be repeating itself. Clinical reports and surveys suggest that other cancers may also be linked with asbestosgastrointestinal, ovarian, and possibly leukemias :y;-ru',mum : -recurs; -ri-.Tc n0t` err;-.'. :!'.:-.:gn ' : ce rated _s mure than probable' and appears lower than for the lu-3 cancers. . Processes yrithhi the Industry . There are three bread divisions of the industry where exposure to dust can occur: mining and milling. ''her. the mineral fibres arc extracted; manufacture and application, when the fibres arc incorporated into a wide range of products; and demolition when the material is removed and scrapped. Mining ana quarrying are usually wet and dust levels arc therefore not high. At this stage the fibre is still closely held in the parent rock, so that the proportion of.respirable fibre in the dust is ' small. Dust levels rise during crushing and drying, and in the next processes where the fibre Is separated ftom the rock. The proportion of fibre increases but much of it is still in fairly big bundles. The degree to which the fibre bundles arc opened into its constituent fibres before bagging has increased over the years. But the dust control w-lth'n the" mills, which was virtually absent in the lS30s and early 1940s, has gradually and greatly improved by a factor of 100 or more. The bagged fibre with its low humidity is sent to the users in' industrialized countries. Significant dust exnrsj.ircs can occur during transport due to the use ofjute bags (now replaced by impermeable plastic ones) and inadequate dust control when the bags arc opened. In the manufacturing part of the industry major improvements in dustiness were first made in the textile section, in the 1930s (following the discoveo* cf a major asfccstosis hazard), and have Siart 9! coci.Titrcia; prv4uc:Scm 9% 53 IK3 *13 *20 *33 M3 <13 M3 * * LUNG CANCER p_r.iwvi. 4 rr.p.iTovcAL MSSOTHbUOMA. ...rr- OT1ISR CANCcES *20 Fig 1 of axbcsto* htiKiUt cuttccrs V !< Table ] 2-ietert inflcnetr:c tVr aswosrrd oaccm Tjrr of fibre Sta:c of Sire TTfr.r At: Sex. Ocsup^:Io3 Co.arjrt Qv> 19lfc{) A.*7!C\iC (A) CrooJ'lK (CO As*.hdph)(!iu (An) __ Dinj-srsion Sna;<- itraichtor curlr Sije-dtintetcf, length Duration ofexposure front firt capture A( Ant exposure S.r.otiin; Troxeelemeni.*. 4c, continued io be mpde since.- Reduction in dusti ness in other parts of the industry, especially in making insulation materials and asbestos cements, cams`later. Adequate control of the dust in asbestos spraying sections is very recent and is still so diir.auU.that the process has been stopped in some places. There are still very big differences in dust control in different countries. The last stag: of the process, to wWch until very recently Utile attention was given, is demoli tion and disposal of waste. Asbestos is almost indestructible and, therefore, it eventually has to be removed from buildings and ships, and else where. It is at this lime often very dry and the proportion of respirable fibre in the dust high, especially during the removal of old insulation;. These are, of course, the processes which-are most difficult to supervise and control. Levels of dusti ness several hundreds times the present standard can easily occur during the stripping of pipe insulation for inspection. The United Kingdom was the first country to exploit the usefulness of crocidolite and also the first to give it up. There i' `wever, still much old insul.irion containing crw-.doliic in ships and ' bull and .-Kc-.viiere. and its safe removal is. a :n.-.;er ct.ch. The A.ct/csii l-cteetci. Council has g.'.-sn an. important lead by preparing Codes of Practice for all uses of asbestos (Asbestos Information Committee, 10 Wardour Street, London WIV -3 HG). . Factors Ir.flucncing Incidence of Asbestos Cancers The more important and specific factors affecting the incidence of asbestos cancers are becoming clear (Table 1). The total dust dose as well as the. pattern appears important. A knowledge of the exposure response relationship is needed to agree acceptable standards of dustiness in industry and predict the likely risk, if any, to the general public. The four important common types of fibre-- chrysolite, amositc, crocidolite. and ar.thophyllite -- difier in their biological effects. The degree of* dispersion, diameter, length, and slrape of the fibre markedly influence where the dust Is de posited in the lung arid its subsequent clhr.inaiion, and probably its biological effect. Thu lapse or time between first exposure and the detection of associated cancers is long - rarely less than twenty* y^nrs for mesotheliomas. This long interval means that the effects now being detected epidcmiologi- cally refer to conditions many years ago, and it is difficult to be sure that improsements in work ing conditions introduced even twenty-five years ago arc fully effective. Cofactors, especially cigarettesmoking, are certainly important; others, such as heavy metals also in the dust, may be relevant. . Lung Carcinomas . ' Comparisons ofresults ofrecent surveys ofasbestos workers: A comparison of the findings in surveys which are technically fairly comparable (T-bte 2) provides some information .about iuc effect of Tabled . . Pjiixt!;.* ut.,, of Ji'jnloi *>Ln -iih foils-- uo of 20 i-r --!'* Iron: Prtl tipour T/pe rf fir. \:rr.nj sni mi!!in; C\ <=f An First Before l$*iO Beforx 19-JO 1936 Ltt*Z eer.ee* Stundnnt ilfuths Deration mortality r,tr:o {ol'serredl (yeart) {all causes) expected) Keferenrr " '* 1/12- 92 1/12-9 120 10 -9 ia:l MrDcniitf etch 1971 . 3:1 Miiifr.sll> exposed 3:1 KMIwOio 4 Meunrssn 1970 I r-.j'.i-.'jn eti.Ie Tc:::is T(.:r,- 1.-- A C.Cr C.Cr c c C.'A.Cr * C, A, Cr Before J9-C5 before 153.1 Ap.tr 1913 Before 19)3 - After 19)3 IJJJ-- 1534--satirculci) 1-9 :o~ 20-r 24 % 2 j. 2~ 153 232 (132) 2S3 1S5 130 200 9:1 !<:l 1.4:1 IS :l 2.1:1 <:t 12:1 SoG.Ter eh J9TJ Dj.'! 1333 Kn? rlet. 1953 Mjonto A El-Attsr Mirwvio 4 Kl-A::ir J9-j7 Ne hc-fvc 19-&9 Nr^hfit/y etc:. ]97^ l-.t, -;- 3- C. A Uefort 1942 C. A.Cr Bs'fvre I'Ko C. A.Cr Scfyi: W-; ?P -r 139 20- uo 262 v.\ Sel-U.Trr sh 2773 5:1 7 et ef. 1970 12:1 E*r.*ci 4 ,m 1974 V 333 Proc.roy. Sac. A fc.L Vulumc 66 April 197J 16 /"\. .-- ' '- ! T:*. C ,4J*2 .ions studied were either gc;d eviilei cat the lung Carrie emu risk is dies.; ?rc*n c:~:r: O . trade union record<. related frabte 3). Despite the low overall ,-^k hi parts ct`:::: inJuairy have now chr> so; lie miners and rmiier.:, :hc c-.c^s-; rrsn J. Ti*.: p r rc have usually l-.e;: to v..:r iinii'.'-'.i to those with the highest past tins' a nrixturc of fibres, bat iOme single fibre type exposures, m me uauw.iaii corners in UK. with exposures h.tva also been reported (Muncuso A a mixed tilire exposure, there is also evidence of a El-Attar 1367, McDonald cl cil. 1971, Ki'iiuoto diiS'ercnce of risk related to probable intensity of A Metirr.taa 1970, SelikotTer cl. 1973). The excess past dust exposure. The levels or dust exposure, c: lung cancer i:es varied considerably between even in those least exposed in both factory and surveys. The most striking con trait is between lh: mine, were probably two or even more orders lew risk in the survey of 12 000 chrysotilo miners higher then levels of exposure in the "general nr.d millers' in Quebec born between IS91- and public from environmental pollution. Thus these 1920, and the high risk in the insulation workers surveys, taken with orher evidence, suggest that where exposures have teen to a mixture of the dose of asbestos dust required to increase the chrysolite and amosite in USA, or to these two lung cancer risk materially is likely to be well ar.d crccidciitc in UK. The big difl'ercrlci might above that which has been encountered up to the at firs'.rick: he attributed to the use of crocidolite, present by the general public. It must, however, but this v.-as rarely or never used in the USA w hen be recognized that the present high lung cancer the groups r.ow being studied for mortality were risk due to cigarette smoking makes it difficult to first exposed more than twenty years ago. A detect small excess risks due to occupational or group of Insulation workers exposed only to environmtntaicauscs. .. amosite has also been studied (Solikotf el al. 1973) and is found to have an excess lung cancer risk Relation to length af exposure and to sex: Dr. "comparable to other insulation workers exposed Nswhousc's study is the only one where a com to chrysottie and amosite. Comparison with the parison between a large group of men and women lew risk tea (he chrysottie miners and millers in with similar exposures, has been possible (New- Quebec might suggest that the ris:< was principally house -'t cl. 1372). Treble: 4 shows that, although linked with amosite, but this is unlikely because the observcd/cxpected ratio of lung cancer is in the early years the insulation workers exposed higher in the-women, the excess rate pee IU0 000 to chry.'Otilc and amosite in America used mostly subject years of exposure is, if anything, greater chrysotlic, and the amosite was not widely used in the men. In both sexes It is related to length of until Iztar. In addition, the lung cancer risk is exposure. This higher rate in the men may In part probably low In the amosite miners and millers in be due to the fact that a year of exposure in the South Africa. Them is also evidence of a high risk men actually entailed a greater dose of dust, or in the past to lentils workers exposed only to that- the interaction between cigarette smoking chrysoti'c (Mancuso Sc. El-Attar 1967). Titus, tto ar.d asbestos ditfers.in the sexes. . single type of fibre seems to bo especially impor- tar.t in relation to the Iur.g carcinoma risk. It Cofc'ctors: ' Asbestos - is a .highly absorptive stems likely that the dost of respirable fibre of a material. Lung cancers have naturally been partiaular size, diameter, and perhaps shape are biamed on subsanccs absorbed on to the" fibre, the important factors. Further comparisons such as trace elements, cigarette smoke; and between textile worker; and miners and millers hydrocarbons from othersources. Cigarette smoke exposed only to ckrysotilc may be helpful, is certainly important (SelikolV et al. 1970). the. especially if use can be-made of records of past - risk being much greater in smokers than in non dust cirr.eer.trr.ticr.s and the physical characteris smokers amons asbestos workers. Doll (1971) tics of txe cast. t pointed out that the cfTects of asbestos-and Fccer.t surveys (McDonald ct al. 1971, N'tw- cigarette smoke arc perhaps multiplicative rather heuse 1959, Nawhcusc et c!. 1972) have produced than additive, ar.d this is supported by more recent ~site 3 /v; ! C, A. Cr c cs^crf obirrvrd,'esfecreddrctki Sts Ls-l'rtsdium rAf-oture Sneer t.\?Zre Vf 1.5:1 6.1:1 P 13.4:1 .*j ir.rrn^e >lezth r,:trt t*.' .led /r ; r er Mt/cx < to :oq 400 4CO M Z 10.6 15.B 27.7 Tc.hlc4 cancer u men ami women af<rr scvtft full.** rrf up CO or mgfc >n (ma.nwfacturiu^av^rUa* iawl-tiioo (cxcilei; C, A, Cr) Men Wc--:ten *S?0\itee O'*") <2 >2 <2 >2 OOsrrredl ex pretext rnfiif 3.0 5.6 6.3 o:.6 E.rcrxt rut* prrJGOCCO yrvrc X20 570 70 2 SO Q P'rrof .* ./.vrrW.i.* jW > v. refer. o s: oking: V .-/.t/. ]972). T: v.;:; fee interesting o of lung cancer stop smoking cut retain their :s!c.< compares with those who nop 2vc no: been asbestos workers. MS50TJfTLlOMA SunVST fX CANADA / 'eis;!;:Us! Tumours Eoth pleural ?.r.d peritoneal tumours arc linked with exposure to asbestos, but as these tumours were recently vet)* rare, and were not on the ICD Hal until 195S, the past incidence is not available from national records, ar.d special sur veys arc r,tided. The panels of pathologists set up following the U ICC recommendations, mentioned i 2eovc, have been reviewing cases and developing " evidencecn (heintsr-andintra-observervariation. ".[.The variation is similar to that reported for other clinical, assessments, and disagreements on .diagnosis arc to be expected. In addition, separa tion between*parenchymal and pleural tumours is not perfect and may be especially difficult in those exposed to asbestos because their tumours may be sited towards the periphery of the lung. * I I CotiWlr ZZZZZ2ZZ2 TrrnlM* Link vrit'i asbestos *xposure; Evidence linking r---Tn oiuu* mesotheliomas of the pleura and peritoneum with Fig3 .. past exposure to asbestos comes from two sources: occupational histories of cases of mesotheliomas countries, and confirm the association between in the records of pathologists, and prospective mesotheliomas and past exposure to asbestos. r studies of asbestos workers. Studies of both types But the first approach has always revealed some have now been reported from more than a dozen cases with no association with asbestos. The*pro portion has been smaller in more recent .surveys irrsoTirEtjoss* svrvsv is scnrur.xn to AWa where the information has been more complete. `Blind' studies of history of exposure to asbestos in mesotheliomas and case controls have been made in Scotland and in Canada {McEwcn ct aL 1970, McDonald et a!. 1970) F*gs 2 and 3). In Scotland only 5% of the cases of mesothelioma gave no history of asbestos exposure, and the primary luns cancer cpr.trols lie between the mesotheliomas and the cardiovascular controls. In Canada, where the surrey was country-wide and covered ail cases over an eight-year period, there was a much higher proportion with no likely exposure to asbestos, but there was still a significant excess in the mesothelioma group of definite and probable exposure to asbestos. The cases related to asbestos in Canada occurred more often in the manufacturing than in the mining sections of the industry. This survey indicated an annual incidence of about cr.e per million. The marked difference between findings in Scotland and Canada is not yet explained. Jv&j l*v> Ne"t To ;bi* Trei-SU .nit Type cffibre: The reports of mesotheliomas from many countries where the proportion of different types of fibre used has v.ijjcJ widely make it highly improbable that cal> one type of fibre is always responsible. But evidence of a bigger xl r\ .te) Tree. roy. . ''-finr.ci'i.-Ii9~J v.i.-ii.of r:j-.o:::v':C rr. ::iC'A.;r. :y,-- nbrc developing bladder tumours in groups most carcmoma c:jr:-,- from exposed to p-naphthytoniinc (SYitllams 1902). ssvz:z: sou.-res. Only a few eases of mesotheliomas have occurred r In South Africa mesotheliomas were first cis- follc-.witg exposure to chrysolite atone (Mancuso .covered in relatively, large numbers by Dr Wagner &. El-Attar 1967, .McDonald cl m. 1970, Constan- in association with the Norm West C;:p- erocido- tin'ides 1972, persona! communication. Wagner lt'.e mines in about 1955 (Wagner a c!. lOG'J). In ct r.i. J971), but they have occurred after exposure the succeeding fifteen years continuing surveil to pure atr.oshi in the manufacturing of insulation lance of all asbestos producing areas in South (Sciikotf et al. 1973). So Tar anthophyllitc seems Africa has confirmed that excess of meso innocent in this respect, despite intensive search theliomas is almost limited to the crocidolite area, in Finland (Kaviluoto <5c. Meurman 1970). with very few reported from r.mosita mining and none from chrysotilc (Wagner ct al. 1971, Dose ofthist, duration ofexposure, cud relation to Ilarlngtoncro/. 1971). sex: Information about the dose of dust and the Groups of mesotheliomas have occurred among risk of mesothelioma at present is qualitative. past workers exposed to crocidolite alone and There arc many reports of cases following short where the dust concentration has not always been exposures --a few weeks. Cases have followed high. For example. Dr J S P Jones (1972, personal exposure to dusty clothes in the home. In addition communication) discovered nine cases of meso- asbestosis is often absent, again indicating ai : thslioma in a group of workers employed placing relatively small dose of dust (Wagner ct uL 1971), .crocidoiite asbestos filter rads in gas masks during but there is evidence of a relation of risk'to dose i. . the war. Five of the cases occurred in 200 of the and length of exposure (Newhouse et al. 1972) more heavily exposed subgroup, but the process. (Tablet!). V was not excessively dusty. Another example is a . . , '. ' small group discovered by Dr fl Lewinsohn Cofactors: So far no definite relation between j . (1972, personal communication). The men had cigarette smoking or other factors and mesoworked in a factory' in the mid 1920s (before theiicmas has yet been revealed. ... . _ _ . asbestosis was discovered!), where possible heavy exposures to crocidolite occurred following its Rising incidence of incsathcGauias in UK: A processing in one area of the works. Six eases Register of Mesotheliomas was started in 1962. of mesothelioma- have subsequently developed Cases from the records of pathologists and the among those working within a few feet of each Cancer Registers have been accumulated wtlU other. No other eases of mesothelioma have new reported eases. Over the years the incidence occurred in this factory, where exposures were of confirmed eases has risen as follows: before mainly to chrysotilc -or to very much lower 1955 tot?.! deaths recorded, 17; 1955-59,' 6.2 amounts of crocidolite. deaths per annum; 1960-64, 17.4 deaths per In general more mesotheliomas have occurred annum; 1965, 24; J956. 2S; 2967, 43; 196S, 73. after exposure to mixtures of amositc, crocidolite, When distributed geographically, the new eases and chrysotilc asbestos than to chrysotilc alone nearly all coma from places where past occupa (Table 5). Up to the present the proportion of tional exposures are known to have occurred. deaths due to mesotheliomas in groups at greatest In summary, although it 5s known that' a risk is about 5%. This compares with ever 90% mijori'.y of the population carry a small burden Table 5 . Pfercrlio^ 9% ursfHi from cxkct asjJ nrvoiS*s<oa feUicd :s r-pr.::on cy?* r.**'i.n; (Curses) . DtetH .Vo. c/ U- co*e*r f'irscttftivrQ F7l-'t Tstcl Vc. y. .Vff, y. C K*l 2413 97 4 3 0.12 C. A.O azi -.35 41 9J 10 4.5 ,, - Vo*x; C.A c:i C, A.O Ki. 3S0 72 19.0 -* J.S Z\ U,4 7 7.1 V 'Ctlu. > V;i m'i *.wufj Hf;vri i <*%; ,iJ tctsilc* lC. A, C*l Ms.i V/c-sr- Yesucr <2 >2 <2 >2 Vki.V //mi/ r rpox^re :s JJ 102 ISO 34 HI of asbestos fibres in the King, it seems likely to be too smell to produce a detectable cll'cct; this is so even though'thc amount of asbestos required to produce mesotheliomas of the pleura is con siderably less then that which will cause asbestosis or lung cancer. Pc'.ks^encsh Kow can this rather confused picture be fitted into a hypothesis of- the pathogenesis of the two principal types of cancer? This is not t!;c place to elaborate On the alternatives, but I will outline one hypothesis being developed by mv colleague. Dr V Timbrel!. * 'Vc he\e to explain: (I) A \cr/ lo.v rncso-. thslioma and low lung carcinoma risk in chryso lite mining and milling, despite very* heavy dust exposures in the p'.r>t. (2) "I ::e much higher mesothelioma risk in mining and milling crocidolitc ti'.an r.mositc. (?) A high mesothelioma and Jung carcinoma risk in insulation workers where exposures have been to mixtures of fibre types, but also apparently a high risk in pure nmosilc exposure in manufacturing insulation. (4) A lung carcinoma risk and asbestosis in anthophyllite mining, but no mesotheliomas. Dr TimbrcII's hypothesis can be divided into two parts: first, the influence of diameter, length, and shape of a fibrous particle on where it is deposited in the lung; secondly, the influence of diameter and length on its subsequent movement in the lung and its entrance into a cell without killing that cell. . The first part is based on theory supported by experiments, and it shows that it Is diameter and shape (curved or straight), and presence of adherent particles which most affect the site of deposition in the lung. The finer and strzightcr and cleaner the fibre, the further it will penetrate; length is of secondary importance. From this it follows that: (1) In mining and milling where the fibres are not fu.iy separated and arc, tnerefore, in bundles of large diameter and also have adherent particles, the proportion of dust which CROCIOOUTF. ...................... --AMOSITE \ i i i ANTKGFHYLUTE 10pm CHP.VSOT1LE V i i < i I I 1. fVt-r. r-jy. Si-C. )!. April /v7 20 by abes:--w, ^ud it will be possible to measure :!>c amour.: ot west ot dviterenc types of asbestos goitijj V) Sut-viitviiwrt ofs*hcr i.ncljrm: ;!iii C$f<m >?!. CJVium xinUt JLe. (2).Uvcc*f ii* v:r of jtlc:os (cjir^jonlc :ni .incite) (3) Redaction e tisnt e^ro^wrct. iiojurrfW't of tfm ^e!: (CoCc* ofTrsciivc. J.*bev:o* Inf'oirrrait.-'a Committee; A>ce>:ot <U%a?4:'Oa9 J969J (S) Piri--J;- cumin^iio^ of ~nr*crj; h.n!ryCiI r^orsjicrtntf (cliw3l,X-ro# lunj fvR.tp#l (J) P.cscrJ itnla-r: proem - !}pc of r.:i:cHaJ used; blok^ica!!/ aspro^risic dun ir.fjic.-crrwsu: rrur^iil rcvofJs . Cooofws'o; f<zrch, ircludinj cot:;^;s<c anatyiU to the various structures in the hint;; aiso, it has recently been shown that organ cultures of Iun~ arsd pleura react to the different types of asbestos (Rajan et at. 1972). It is, of course, recognized that cigarette smoking is a major factor m the lung carcinomas. Work is in progress to study the combined effect of asbestos and cigarette smoke in animals. . Prevention What is being done to use this epidemiological knowledge for prevention? Table 7 summarizes will get to the pleura is'small compared to later steps now being taken in this country*. I have stages in manufacture where the fibres are cleaner already mentioned the extensive review of the 2nd rrtors separate and, therefore, smaller in uses of asbestos by the Royal Navy, leading to its diameter. (2) The fibre diameter and shape will replacement by other insularsts for a large number also aSect where the dust goes into the lung after of purposes. Other large users have done the same. dcpoSltioh. Imports of crocidolite into the UK have fallen .. Fig * shows how different the fibres are under strikingly, compared with an increase with then ithe electron microscope. An'.hophyllitc is much for the rest of the world. Last ycar.jio crocidolite -larger in diameter tiian the rest; therefore, less of was imported into the UK. Arc those countries 'it will penetrate deeply into the lung and little to into which greatly increased amounts are new .the pleura; in addition, the diameters may be too going taking sufficient precaution in its use? * big to enter cells, except plutgocytes, without The UK was the. first to introduce new and destroying them. Chrysotilc is very fins, but it is mere exacting environmental standards for also early, especially when fully opened; much asbestos (Department of Employment and Pro less will, therefore, reach the periphery than ductivity 1969), following the recommendations would be anticipated from its diameter because of the British Occupational Hygiene Society interception occurs higher up the respiratory (1963), and also to develop Cedes of Practice, tract; it also happens to be relatively more soluble worked out by the Asbestosis Research Council than the other types; enough may, however, reach in consultation with- the Department of Employ the respiratory bronchioles to cause asbestosis. ment; a number of other countries have followed Amosite and crocidolite arc very closely related this lead. Following the recommendations of the chemically and until recently were thought to be Advisory Panel of the Senior Medical Inspector, so similar that differences in mesothelioma rate a scheme for the periodic surveillance and long in mining the two types could r.ot be due to term follow up of asbestos workers has been differences in the fibre (Wright 1963). It has now .put into operation by the Department of Employ been shown that there is an important difference ' ment in co-operation with industry (Ministry of in diameter (Timbrel! et at. 1371): crocidolite has Labour 1967)-This will be gradually extended to about one-third the diameter cf amesite and, as the cover all groups potentially exposed, as they arc falling speed is proportional to diameter squared, identified. Thc_rccords of this scheme will be. the amesite fibres will settle nine times more linked with the cnvircr.mcntaj measurements ' rapid :y than the crocidolite. Tit'.:j, there wi! 1 be less <mane:c of an amosite ri, re reaching the r* itcry of the lung and. t 1 A pleura. NVe still recorded by - the employers and the Industrial Hygiene Unit of the Department of Employment. I would like to stress the last item. Research by h.2VC ta ex plain why the crccwV1' lie mined in the Or E R A Merewether in 1929 revealed the high Tran:.waul does no: seer.: to c:IL15C rrtcscthclioi tins. risk of asbestosis in the textile industry. Alas, no Surprising:.;% ti turrs cut ;*.:c crrcidolite frem continuing research effort was maintained, despite tills 2 r<r2 h: the seme diemete r us tit: amosite 2 d his proposals at that time (Merewether <Si Price is r.c: P *.c c :r. lha North VVest 1930); had this been done, better, controls would Cn^c. "Tifc crocidolite ft cm \ raiia (no lottger almost certainly have been i.-.treJeccd earlier. We shall need to know whether the controls now from the North Wes: Cape being introduced are adequate and must also look This hypothesis cuts sc .vay to unify i:vc a critically at substitute materials to be sure they It Isas she arc innocuous. If it should turn out that diameter, peb'e in animals. length, and straightness uf n fibre influence its i su. :\cs cs.ased hi mar. chances cf'jcititig into the deeper parts of the lung. 2J .i : /v zr.d ther. is. r.-.-p.r.ble cf cecorttirv: malign:: r::, clhcr line f.v. Hi have to be looked a: critirr.Hy. I should also like to stress the cast,'benefit analysis. EpitLctr.tclcay iz largely directed to assessing ill health. To produce 2 balanced assess ment, we need metliads to assess the benefits - for cxanp'.c, the protect.;or. afforded by asbestos against lire damatta to..life and property. The safely of our whole transport system depends heavily or. asbestos, due to its e.s;er.t;::! use at present in brake litiittry and dutch plates. A start has beer, mace by the Institute of Social and Economic Reseat--it, University of York, to assess the kind of information needed to make such a cost/bencf.: analysis (Akchurst 1973). `I have attempted to bring top-ether ir. this account soma oT the pieces cf a jigsaw puazlc; a number of-the pieces have been shaped by those with whom I have teen fortunate to work over the last ten yearn. They do not yet all lit. But the ` picture is clearer and important seeps towards prevention have already been started, based in part on knowledge acquired as a result of a widely based research effort. ' :;ct j*J J C. .a D. O ***. S,*rtaj*<K*2 Ar //.Nt.VA 22.677 .Nf<fl^%* J.i*t* A, ,\fur,\ ' \tditci JaitrrtiUS A AM M^icuwTb L n*AfUfAA {'%**") J cf 2i*dUt*c 9,147 E R A 2 C W* " * (1Ci}j> Rsr'Jf* 6o o5 A\h<+tc>\ D\i\: o?> *.? ent! Uw*: in Hi? A ;br%:ss H>!Sc\ London Mu:U:r rl 1 r.>uut(:957) rroStrat. ArAifijffWt ll.' U; cf HMhO, London NcNnuw>! L(IVU-V) Jf'.t.'n!vf .\(rd;c^c25,294 Nfl.ovr M U Herry C. V* Jjawi C .* TvL 7.J K -if; J.^rr.ctcf t~,!.:itrZz! 27. 134 Kn,>n KT. Wsvnrr J C ft >.*.. FK ' <I).v.vrr(.Uftd**) 25i. J46 bcL^n.'I { J, E C2 * J ^ (I97y) In: rVrvnioconov*. IVwcTdi*?:*orim<rn^i'on4i Cpr.fercr.ae. JvJiennc.burs IWA.F.ti. II A bhcpira. Urjv. r*I:y C;;*c 7 *<. ft4.;p 1520 (197.*j in: iVcrccJmci r*riVInt;rr.2ior:al rneTrs.*o<uois . Ccnrvrcn;r.r.uckarcti (injms) T>!-?rJia IK.Coo**rr\V C2 iuLrrJ L . * {!97v) AeeM^t o/Zr.viVewpw/McsUl 21. 754 Timbfdl V. CfiEiiht IJ M ft- Vo-lcj P D (1971) <U*4m) 23 2. 35 . Vice <!><;) Ln:i%hJju,r,xlofl*&tt,&Zfc&i*~ 22.165 Wasner J C.CnonJ C, Uerry <#ft*Tiniw,*W V* (l>7l) M*dlenl UuitxUiH 27.7! \Vj;r.cr J C. S!f J5S* C A ft 3 Urciiswl K ' (tCf.'Ji Cfiliih JzueazlcfIn.iuUticlSicJUl^c 17# 260 WKwAUIC (P32).! (z: 7^.CJ6 Wnzhl C W (IKS) ArcUra of Ue*Uh U, 173 REFERENCES ' '. AWhmt R cj) t:t: R2.;pyc3 SFVsti ofAtbrisos. Ed. ? Bu;cmsi.5 C CiUer., VI ft 5 C Vaster. I Pub^.niti.'HNc. S. Uon (j.n prrw) fccr?>'C.NVU**M Lft 7-rokM (1*572) Lunect u,476 Eorn<! (I5CT) efiue Royal SseusyefMf&ittt 60.93 LfJhKOrcv*tji3l llxzisKtSocIciv Ces:iai*ctn Hygiene S:ar.2irils(256) AtfzU c/Ozeuysticks! Jfjficnz 11.47 CimRAM (1959) t'rzxrclt'ezi cfik* Koyat Society cfMedicine 62, 1061 Drpo^oicotct ErtsZeyincal IVodwrmiiy (2959) Slstuts.-y Ir:?ur*cn:s I960, No. 6"0. F4?tc?cs:Thr Albedo lr9. H.MS0.1c.*.Jon EsCltC (i 954) Przzezd'.r-;: cf'.Uc Peyol Satiety efMtiilcinc 57, J 165 DsHTl Vt1t)Jwvteft:i* Srztizr.zol Society134,133 r-sarC&S^-^M J C (! 57!) D*iiUP Jwfizi cf!r:Uvtial Aftt'/ctr2!, 226 Fsf/M! A?M (t * 7 \ j Przzer-Jurs: cf:' c a;. ; / S~cl*ty cf.KtcJiriuc b-i, *09 JianVttsr J h. C 3 C ft v5r*-er J C {: J?!) .Vs.'y-r'ij-J,:-. :52. 54 R ft M^*frr-.a 11 In: J r' < r * *;. m: Cv.-?sr<*cc. Jiiir-fibvr;. 15.0. L'i. H A Sr.iSrs. C A*?J f-rj*. C.sr: 1 **92 K.-:tJr. !is\i!*S.: ' * 1 IS.' IE {:*: i*-;.;:;..*:-- -25.2*3 ';<u*':Arr,r;,*f' \. cC.' A A '! Do.alJ J C (i r`2. Cu-rrr - 2 i. ? . 4 / DI5C5.WON . Dr JR CIo*er {.Cardijf) asked -hai was meant by respirable dust in relation to asbestos, i,el did the definition depend on mere that* fSbre length? He also enquired if there was any use ra biologically monitor- ins isfcestos workers; in other words, vests there any evidence that a worker who had once contracted a sign or symptom of ouo of.tsc three fatal lung diseases caused by asbestos ever been heaped by taking hint away from exposure to asbestos dust? Dr Citsen, ir. reply to Dr Glovest said that no-single parameter c: the dust could bar used. It depended on the diameter and tha shape - u-Jarthcr straight or curly - but to a iris extent on lengpii; density was also relevant. _ Dr Gilson said that the use of biological monitoring could r.ct ye: be fully assessed. It was not known whether there was a detectable stage at which removal from further dust exposure arTcctud prognosis in rela tion to i>bettos!s and asbestos cancers. It would be possiola ta f.r.d this out or.'.y by prospective studies of appraprirte group-*. tii:ci :hi> was saw being started. v