Document pmnYMpZMZXXa5no8RLrjvywbD

.. and Morutuv N*tional C.-cr me f*temu- 5.5*9 neuroblastoma In -rc. MD V,verK euomapneti-' field' 4-5-4go on Health Perspcct .a- and occupational D National Cancer cohorts. Chemist-. 'I ` its effect on cancer ura! nervous *>Merr An investiganor of n method ) Occup v>s-ure to microwave :6-66:-670 asbestos insulation icX .-cupauon* and mo... i:i 9N-929 nous sysierr, cancer ted 21.367-J70 ]982a) Brain cancer 120-129 alio panem> amonp .-pational nsk factor- rv of Industrie- and ? ?! 40*-ill from brain tumo- ;er Am ) Epiae--.io! PLAINTIFF'S EXHIBIT ^ 3 >3 American Journal of Industrial Medicine L?:6J9-457 ()988> Relative Risk of Mesotheiioma Among Railroad Machinists Exposed to Chrysotile Thomas F. Mancuso, md Thu Mud> challenpo the assertion of low relative nsk of chrvsotile in the causation of mesothelioma Datj are provided on the tmc period use of various tvpcs of asbesio- ir. the United State-- and in insulation materials The focus of the studv is on mesothelioma among railroad ma;hmisiv emploved in the steam locomotive era who were exposed to chrvsotile Within a cohort of machinists aloe January I. 1945. a suh-cohon method wa-- applied i<- all succe-sive machinists hired in each of the respective veur- 11920- 1 fi'iiowed through 19bb The total cohort was [M and the number of death' 15b. with U mesothelioma- identified among 4! cancer deaths The finding- demon strated an extremelv high relative risk for machinist' exposed to chnsotile fot the induction of mesothelioma in the individual >ear of hire cohorts A stmiiar observation wa- noted for other crafts hired in the same time period One mesothelioma occurred for even 13 machinists hired in the succeedinp scan t I920-1929 and constituted 34 c, of all cancer deaih' It o concluded that chrvsotile ts far more hazardous in the induction of mesothelioma- and that the a-bestos cancer risk in the steam locomotive era- wa- much hipher thar, had been previous!) estimated "" Ke> words: railroad, mesothelioma, ehrvsotilt. machinists, epidemiologv, craft- INTRODUCTION The direction of thi- brief paper ts to focus on a specific lime penod of asbestos exposure in the Untied States as a basic means to identify the type of asbestos used in the railroad industry tn the steam locomotive era. which is the subject matter of this studs. Chrysotile represents approximate!) 95^ of the total world production of -ii forms of asbestos, w uh Canada its largest producer JRosato. 1959] It ts contact w ith this tspe of asbestos, according to Hueper j 1965]. that furnishes the chief cause of asbestos pneumoniocomosis and cancer, especial!) tn the United States, because contact with amostic and crocidolite have beer, comparative!) minor, and these varieties represent bui a small (ruction of the total amount of a-besto- produced and used Estimated U S asbestos consumption of 1920-1930. which includes the time Department of Indu-ina! Lmironmenta' Health Science- Grdj*ic Schi**! of Public Health. Irmcr-itof Pitt-burgh. Pittsburgh Adders* reprint reque-!' 10 P- Thomu- F Mancu-o Depanmen; of Jnduvtnat Environmental Health Services. Graduate School o( PuMi. Health. Iniver-nv o) Pittsburgh. Pittsburgh. PA I52M Accepted for puMi;anor Januj*} 10. IVs- $ 1988 Alan R. Liss. Inc. 640 Mancuw TABLE I. foyo joys 101(' l.S. Fihfr Oor*'umptmn (Ton*-' 0<vJi>!ur Amciii' Canadian chr\ Motile Oihei No datj Sc foU I.Of- N,- da:. m y(> 4.000 4.10(1 k.SOO To:-' amv'^nr a'lj cr.viJ.'hK iComhitied Ton*.*' ]o;j io?y 19?? J9?J l&is J9.V ,0-.* |WVV jOVu &:? :i: 2?? is: SOI i.4?: :.9:s ?.:*: Source l S Depanmeni of Commerce Tola' ISe (** x(* i :os.ki" period of this paper (I920-I929i. is shown m Table 1 as well as consumption estimates for amosite and crocidolite combined by >ear from ]930--39. _ The question of relative nsk m the induction of mesotheliomas among railroad machinists relates to the form of chrysotile asbestos that has been provided from the Canadian chn soiile mines for many decades for commercial use in the United States tit is this form of chrysotile asbestos, to which exposure has occurred and mesotheliomas developed, that addressed m this investigation.) " The foundation and exploration of the employee-specific year of hire approach m the evaluation of the use of different types of asbestos in insulation materials in the United States was provided b> Selikoff. who has conducted the most extensive work in this area jSelikoff et al.. 1970] The basic information on asbestos type relative to the time periods derived from vano^ reports and communications.are as follows The largest asbestos manufacturer in the United States first used crocidolite in 1929 (for sheet packing, nor insulation) and never used crocidolite for the manufacture of insulation at any time (1928-1968). employing it in only two products (asbestos cement pipe and packings (Pundsack. quoted by Selikoff et a).. 1970], * The very small amount of imported crocidolite in the United States was used for valve packings and woven braid (Pundsack. quoted by Selikoff et a) . 1970} Until approximately the early 194(k. chrysotile was primarily utilized in the manufacture of asbestos insulation products (Selikoff et a) . 1973) The limited amoun; of imported amosite distributed throughout the United States had its most extensive use in the maritime industry. m shipbuilding and repair. (in particular in naval vesselsi. with the first application of pipe covering in 1937 (FJeisheret al.. 1946}. During the 1950s. amosne was the predominant type of asbestos in insulation materials (Cooper and Miedema. J97?) _ Smither J1963). referring to one of the world's largest producers of amosite. stated that as far as he was able to ascertain. "The only asbestos not implicated in _ association with mesothelioma is amosite." V' Totj1 ft p ` ISM*** 0" JlU.XO' r1 yos K'* ):' ;* \ as consumption -39. as among railroad pro\ ided from the the United State' ias occurred and r 'lire approach n, .aterials in the st extensive work os type relame to ' are as follows: i used crocidolne 'octdohte for the c it in only two d\ Selikoff et al.. d States was used f et a!.. 1970). rily utilized in the i J ;ghout the United nidmg and repair, covering in 1957 sstos in insulation Jucers of amosite. not implicated in Relative Risk of Mesothelioma Amonf Railroad Machinists W1 Jn terms of the historical perspective of exposure to asbestos in the railroad industry, the principal and most extensive exposure in volume and dimensions occurred in the application and removal of asbestos lapping on the boilers of steam locomotives A description of these work practice' has been provided by Mancuso J1983) Chrysotile wav the type of asbestos used since the first application of asbestos in the steam locomotive era for the lappmp of the locomotive boilers, and this continued through the succeeding decades In addition to chrysotile. if some other potential exposure to amosite or crocidolne as packing or other material occumed at some point in time, the actual exposure would have been comparatively limited in nature and scope From the evaluation of data relative to the type of asbestos, year and amount, and the time-period use of various types of asbestos, it is reasonable to conclude that the type of asbestov used for lagging insulation for steam locomotives for railroad company A was almost exclusively, if not solely chrysotile during the 1920-1929 period Thi' would also apply to 193(>-I939 and into the 1940s and later The last steam engine repair for railroad company A occurred in 1957. The nature and extent of the relative risk from exposure to chrysotile asbestos, in terms of the subsequent development of mesotheliomas, constitutes the main emphasis of the present study of railroad machinists hired dunng the years I920-J929. The methodology used is the concept of individual year-of-hire cohorts of the same craft m succeeding years exposed to the same asbestos conditions and each observed since date of hire The concept of reproducible effects has been well established in animal experiments Exposure to the same carcinogenic agent, for a specific number of the same animal species, under the same conditions, observed for the same length of time, provides the basis for estimation of relative nsk The results of the present epidemiological study represent the equivalent of a successive series of human experiments on the occupational exposure to chrysotile asbestos among machinists hired 1920-1929 in the steam locomotive era of the railroad industry. It is not the purpose of this investigation to evaluate the various theories involved in the development of the actual cancer process, but rather to focus on the disease itself, the occurrence of mesothelioma following exposure to chrysotile asbestos MATERIALS AND METHODS In a previous study, data were presented on a cohort of white male railroad machinists alive on January 1. 195-1 w ho had been employed before 1935 JMancuso. 1983). This paper is based on a similar but earlier seniority list prepared by railroad company A. as a regular employment procedure of railroad machinists and other crafts, alive January J. 19-5. who were employed before 1935 Within this cohort, successive suh-cohons were established representing those machinists hired in each of the specific years 1920-1929. inclusive, followed through 1986 The study is unique in using an internal control comparison rather than the general population. In this respect, the method differs from other epidemiological studies by focusing on the individual year of hire and relating the cancer nsk soleh to those hired during that specific year In essence, the successive cohort method provides the means for internal comparisons and for the investigation of reproducible effects in terms of relative risk. w: Mncw T ABLE 11. Stnkvriiv Cohort of Railroad Machini'i* in Railroad Compare A Alive in 1945 and Subcoht.n Hirrd I92ft-I929 Total number Cohort of what malf- hired More I9?5. alive in 1W5 Death' with cau^' of death information - Subvohon white male' hired 1920-1929. employed in J945 Death'with cau^e'of death information Sot known to he deceased in 1986 285 25' 181 156 25 Ji is recognized that the 1945 semoritv lm represent' a survivor group and that other machinist' could have left or retired before 1945. The identification of .the deceased was derived from the death claim records of the Internationa) Union of Machinists and Aerospace Workers Death certificates were coded bv an experienced nosologist according to the 8th Revision of the Internationa! Classification of Diseases. Injuries and Causes of Death RESULTS The analyses are confined to those machinists hired 1920-1929 for railroad companv A Table 11 relates to the description of the successive cohorts. There were 1$) white males alive and employed in 1945 who were hired from 1920-1929. inclusive. Among this group. 15b were identified as dead in 1986. Table 111 is a presentation of the successive cohorts representing machinists hired for each of the successive years 1920-1929. In railroad company A. the table show s for each sear of hire, the number in the cohort and the number of deaths. Also shown is the distribution of mesotheliomas, lung cancers, and other type* of cancer in the respective >ear of hire hv age at hire Among the 156 deaths. 36 pnmarx sues in the 4) cancer deaths were identified. 14 (35) of all cancers were mesotheliomas The same employer railroad companv A w as identified on 13 of the 14 mesothelioma deaths As a point of reference on the rants of mesotheliomas tn the general population. Selikoff et al. | J965} cite the enervation of 3 mesotheliomas of the pleura and no mesothelioma of the peritoneum among 31.652 death' in a study of 1.(>46.185 men and women reported bv the Amencan Cancer Society Table 111 illustrates the extreme)) small size of the successive cohorts of machinists in which'death' due to mesothelioma occurred -The basic observation from this simple ana)vsis show s that fo; each hire seat from 1920 through 1929 (w ith the exception of 1921 and 1928. w ith on)\ 9 and 1 hired in those years, respective!)). mesothelioma incidence was replicated, for ea>rh of the successive cohorts of machinists hired in the same vear. at comparable age at hire, emploved at the same workplace, exposed as a specific craft to the same asbestos working conditions in the ^steam locomotive era In terms of relative risk in the development of mesothelioma from exposure to chrysotile asbestos, what is most sinking is the occurrence of mesothelioma in such a small number of deaths and cohons in each respective individual year of hire. On r in 194? and loti1 nuniiv :sx S<* m IV< -s v or roup and that entification of the national Union of b\ an experienced Classification of -1929 for railroad ->hons. There uere from 1920-1929. s sf ' nc machinists n( .. A. the table ner of deaths Also ier types of cancer hs were identified. railroad companx of reference on the al |1965] cite (he a of the peritoneum n reported hs the cessjse cohort' of basic observation through 1929 (\uih car>. respective)} i. :essi\e cohons of plosed at the same tg conditions in the a from exposure to sothehoma in such al sear of hire. On Relative Risk of Mesothelioma Among Railroad Machinists 64.' TABLF III. Surcfss'v< Cohort' h> >tr of Hire and Aft From 1920 to 1929 Among Railroad Machinist' b> Cancer Cum of Ikath ______ ___________________ ___________ Nunitvr if Sumfv? r>J dcjth* Carver* Mc'Otheiionu* Lur: M.vjiS SmfTVich O'l.'f Cfv uni Reciun BUddet PriMjie Adrer.j' Rfneulun- celi Sik unl.n ** r. Prinijr\ carver* 7<Mj` cjn. er* I}i' i: in r:3d's>, 122 > j j;i u > -- -- i 1 1 W o' Hire iu;> tu;4 )g;s |*j a v* 4-1 l< y. 2 iT 1 >' i; 11 . r 11 i y>i .:n i2d ' r;: l>r Ape a' hin <> i:.j iN' (4-1 <:a - IS.*' t A 2 1 (41 i rt* idt'r i.'ll (4.* i (4! 12U t"1 t.'M- .'O' (!' 6 t '* s 7A9 l> |S i: to." 1* 14 !9> t (> 125/ (24, _ :?i (221 l.'Sl -- (2V- A J-- 2J I9> loU i: IM 9 1 5f> OVj )4 ( '* 1 i t 1 1 I - 1 1 1 A t 1 A .'t* A 41 A'be'U`*i* r`EndothflK*mj of pieur^ 'Hospitj1 reeord p4in M oi death certificate tor ?a.h cat .or ot "other sipmfuar/ condition*" no; included if total *Sanu ca*e the average, one mesothelioma death occurred for each 11 deaths, or if one referred to all 1M of the cohort, the relause nsk would be^ne mesothelioma in exerx. 1? machinists hired The precision of the reproducibilitx is funher demonstrated for those hired in specific \ears In 1922. of the 19 machinists hired. 2 mesotheliomas occurred tn men hired 6 months apart In 1925. of the 27 machinist' hired. 5 mesothelioma' occurred. 2 were hired in the same month. 10 da\' apan a* ace' 20 and 21 The third cave, hired 6 months earlier, at ace 2J aKo had a'be'to'i' A machinist hired w nhm 2 month' of the third mesothelioma case, at ace 2*1. a!'k> hud asbevtosi' h'ted on the death certificate' In 3925. among the 5 mesothelioma'. 2 were hired 2 months apart at age' 25 and 29. and tn 192". the 2 mesotheliomas were hired 5 months apart at aces 24 and 25. ]t is recognized that other case' of mesothelioma max haxe occurred among the machinist' who retired or left before 1945. the xear of the semontx list. This is illustrated with the following case fS. a machinist uho retired in 1943 and died in 1946 (age 69) with a pleural endothelioma, with prior employment in 1916 with railroad companx A at the same facility. The medical report of this case is included because it represents the earliest <44 Mancuso death (1946) and the earliest exposure that would he related to the use of chrxsotilc ashesto' b> worker4 employed by railroad company A The posi mortem examination showed that _____ was suffering from a malignant tumor which had its origin m the wall' hnmg the lung surface and the inside of the chest wall This had started m the left chest and had progressed to inxoJvc the cells and lining of the abdominal organs (peritoneum! and to a lesser extent the sac surrounding the heart and the lining of the right lung It became dear that the tumor had extended through the chest wall in the front into the tissue which we had cut into on Tuesday morning which was indeed pan of the tumor This is a \er> unusual t>pe of cancer since tt had spread so widely it of course wa4 unapproachable by any type of treatment We regret that e were unable to establish the diagnosis during life. *' Signed b> Medical Director-Internist of railroad company A hospital tThis information was obtained by chance from the victims family) Hochberg 11951 ] considered endothelioma as mesothelioma in h:> rexiew of histological origins of tumors The probability that other case4 of mesothelioma had occurred was confirmed from communications with former physicians of the same railroad hospital serxing employees of companx A In reconstructing a senes of observations during the follow-up inxestimation. it wa4 determined that a presentation of mesotheliomas had been made to the local medical society In terms of histoncal perspective. it appears that Otto 119S6J was the first clinician in the United States to report, in 1967. the occurrence of mesotheliomas among railroad workers to a medical society. There ua4 no publication. The presentation was directed at a series of JO mesotheliomas (1957-1966) in which 9 were male employees of railroad companx A. The occupations at the time of clinical evaluation were, executive (engineer), track foreman. ? machinists. 2 boilermakers, shop foreman, engine carpenter. The duration of life from diagnosis for $ cave4 wa4 9 months. Otto 11986] believed that other cases of mesotheliomas max have occurred but were not recorded on the death certificates Within this context tin the group of mesothelioma4 in our stud>) was a machinist hired in 1922. w ho had a mesothelioma of the pleura diagnosed in 1965 and died in 1966. Despite the established diagnosis, the death certificate was signed ai t-me of death b> a ph> sician other than the (rearing medical artendam. w ho recorded lung cancer as the primary cause of death Obviously the physician signing the death certificate was unaware of the prior diagnosis of mesothelioma Tms case represent4 either the extension of the original mesothelioma into the lung, or constitutes two primary tumors, and ha* been identified tn both categories in Table 111 Further, it wa4 learned lOtto. 1986) that the thoracic surgeon for the same railroad hospital serving employees of companx A "had operated on more than 20 mesotheliomas in 15 years." No details are available on these cases. Another phxsician fBaur. 1985] confirmed that approximate!) 20 cases of mesothelioma had been diagnosed among employees of company A from 1957-1971 who had been exposed to asbestos insulation in production and repair of steam engines at the same facility. These additional cases of mesothelioma are very important because, based on c ' of chrysolilc cring from a lung surface :hest and had runal organs bean and the lad extended id cut into on ad so w idc)> \ c regret that d bs Medical rmation wa' in his rewew of red was confirmed ,d hospital serving .anon' during the mesothelioma' had peeme. it appears port, in 196". the scvet> There was 1 esothebomas compans A. The (engineer). track rnter. The duration ed that other cases death certificates our stud> i was a mosed in 1965 and cate w as signed at iant. who recorded n signing the death ni" case represents or constitutes two Me 111 :eon for the same j on more than 20 ^e cases Another mesothelioma had >71 who had been ngines at the same because, based on Rrlaliw Risk of MfsoOx-liomt Amnnf Railroad Machinist *45 the mesothelioma deaths m the present stud) for that period, the) would have had an interval between hire and scar of death of 55-46 scars and therefore would have been hired during the 1920-1929 pent*d of this present studs Mancuso j 1985] had access to onls 7 mesothelioma for the specific time peri(*d of 1957-19"! for compans A in reference to lung cancer. Table 111 also shows that there were 11 death' due io cancer of the lung among the 56 primary cancer deaths, compared to 14 case' of mesothelioma Lung cancer deaths occurred in each of the repcctise sear of hire of machinist cohort' from 1920-1929 iwnh the same exception of 1921 and 192k. with 9 and 1 hired) In 1925. a lung cancer was noted in Pan II of a death cemficaie The most striking observation was the closeness of the dates of hire between some of the cases of cancer of the lung and those of mesothelioma which relate to the sanation in human response For the 1929 cohon of machinists with 2 career death' tone cancer of the lung, and the one case of mesothelioma!, each was hired on exact)) the same das. ai comparable ages (51 and 29) The lung cancer patient died 9 sears later 119801 than the me'Othehoma patient (19711. For the 1925 cohon. the hire date' of a patient who died of cancer of the lung and another of mesothelioma were 5 days apan. at ages 52 and 25 The lung cancer patient died 4 sears before (1967) the mesothelioma case 119") i The other pair of lung cancer and mesothelioma patients were hired one month apan in 1925. at ages 25 and 29 The lung cancer patient died in 1972 and the mesothelioma patient died in 1985. 15 years later In 1925. the hire dates were one month apan for the deaths due to lung cancer (with pleural plaques cued on the death cemficaie) and mesothelioma, the employees were hired at ages 22 and 20 The lung cancer patient died in 1952 and the one with mesothelioma 26 sears later, in 1978 ]n another close!) matched pair, cases with lung cancer (Pan Hi and mesothelioma were hired one month apan at ages 28 and 21; the lung cancer patient died in 1972 and the one with a mesothelioma in 1977. 5 years later In Table HI. for sear of hire 1920. a rare type of cancer, reticulum cell sarcoma, occurred among 10 deaths and i' mentioned because, in animal experiments by Gibe! et a) (1976). reticulum cell sarcoma' were induced bs chrysotile asbestos (oral administration) Wagner 11962] produced such neoplasms by intrapleural inoculation For sear of hire 1922. there was one death categonzedas due to cancer of the adrenal, in a cohort of 19 This jv cued because another death due to cancer of the adrenal occurred in the 1945 cohort, a machinist hired in 1918 (There were 11 machinists hired m 1918 i Sohcper' 11965] cued his own observation of mans sears before--of a case of pnma") carcinoma of the adrenal in which asbestos bodies were demonstrable in the adrenals This tspe of cancer warrants further investigation. Table IV shows the distribution of the mesotheliomas b) sear of hire, sear of death, age at death, and sea"' from fir>t employment to death For the 1920-1929 cohon of machin.'ts. th; pattern of prolonged latency continued to be seen in the succeeding decade> The ev idence that ma-ked sanation m human response can and does occur in the latencs penod for the development of me>othehomas following the same type of work exposure to dust containing a'besios is prov ided not onls m the successive indiv idual year of hire cohon' as show n in Tabic 1\ . but also within the respective sear of hire as previous!) cued A sinking illustration is the 1925 sear-of-hire cohon. The two mesothelioma cases that were hired 2 months apan (October and December) had a date of death difference of 1J sear> (46 and 60 years) For the two cases that had the same age at hire. 29 sear>. the interval difference was 25 years (57 and 60) 6*6 Maori/ TABU: J\ . in Sucres'" t Cohort' of Railroad Msrhiimt' Hired |92(ul929 b> ^eir of Hirt. A* t Death. Inu-nal in Wars. War of Death and T>p< Hire dau Aci ' hit'- lnuT\j` ir ncj'"' Ape r death War n< death iv;u ]:: )v:: ISC' iv;j iv;s iscs IV> hj:iv;" 19> 2" D ;i yi :j ;si A^ *< a. W Nl J< 4-1 SJ <A M ;* v t*' ,'f 41 4' S' ISIS4 Pleura p* |WP` Pleura p* IVbP Pifura* `4 IQ-7 Pleura IQ'S Pleura S4 lS4 Pleura p: 195" Pleura pr> ivp: Pleura S' IQsS Pleura "1 ' IQ'l Pleura M jop; Pleura" P IQbV Pleura * JO'S I'rwpeeififJ `1 IQ'l Pieura -)9?9 r. A 19"S Pleura'll *Wa' from first empl''\mcrr i<-death 'laieru ot lapsed pen>>i > fAI'i' had June carnf specified or dca:l* certificate 'Endothelioma of pleura CW nr. asbestos" Similar)}. in a comparau\e sfud) on insulation workers, anion* the 22 deaths due to mesothelioma jSehkofi et a).. 1970], fo; the 15 employed in 1920-1929 exposed to chrysotile. the interval between >ear of hire and death varied from 25 m 45 years An illustration of a relatively short latency period following exposure to chrysotile was cited by Scansetn et al 119S.41. who reported on the development of pleural mesothelioma in a worker involved m opening chrysotile asbestos fibertJon an intermittent blits) to increase the surface area for filter purposes in the wine industry. Symptoms developed 7.5 years after first exposure to the chrysolite asbestos. Table V shows the lung cancer deaths by successive cohorts (1920-1929) by year of hire, age at death, year of death, and elapsed years between first employment and death (The table also includes the observations on the 1930-1939 successive cohorts.) For the 1920-1929 cohort, the interval ir. years from first employment and death was 27-51 year> There uas marked variation in the latency period even for those hired in the same year, for example. 1923 If one compare> the m-oothehoma' and the lung cancers hired in the same y ear. the age at hire for the mesothelioma'. with tust a few exceptions, is less than that of the lung cancers ll one compares the interval in years from first employment to death between the mesothelioma and lung cancers for those hired in the same year, in general, the latency penod of the mesoiheboma< was longer than that of the lung cancers The fact that there were 6 mesotheliomas, an extremely rare cancer identified from 1972. and only 3 lung cancer deaths for a cohort (1920-1929) of machinists with the same medical and hospital facilities and care during the same penod of time, strongly suggests that other cases of lung cancer may have occurred and were not . ,i |*U m.'s t>> .. I'ly___ n <<.' n it m.; J't l'r n... 1*1 Ml.'' |T- Ill.1 |T Ml.. |'i Ml.' n mi.I'l 1M.. IT Ml.' I l-\|K . iflCd IT "... IT .1" .f ' u;- III' ::: deaths J in i;(i-!929 !' 11 1 tilt 25 to i II'" i v Insure to 1. ipmcnt of .Ivsli*' 1hher' ton M' 111 the wine << ll .hrvvotile 1 IW?" !V2-b> tll'1 CIM [ilovmeni 1 ij oi mu vessive i tnpt' > ment and . JXI'1*1i even for in tl" s..line vear. . Ii" tl* .hi that of m. i it O' deatn l. '.HU- \ear. in lll.ll III iIk lung l Jill I'l identified nj | i ) machinists it nivi k! **1 time. 1 Til were not Relative Rhk of Mesothelioma Amon Railroad Machinist* M7 TABLF ' . Lun Cancers in Surcri Cohorts of Railroad Machinist' Hired 192CM*2* b tear of Hirt. Apt al {Hath. lnler\1 in Warv >r*r of Ikath Hire VC4' |o;n iv;: t:: jo;? i:j iv;s iu;s j> HOw ]Olu |Q7sj |0?g Apt at hin is :i > aa ;; > rr u VI lu : *. ;* *i ; IniiTN^I in ncj'-* 4* ;* 4-1 4U 4* 4* 4; Ve M |o:.i. )g;v In 4'1 K 4f- Ape at death t>5 4" 65 50 7p 7; Mi 71 74 t) 70 ^ 7] S4 74 ^ cat of death |W4U twpn' tys; iv5: 1 71 i<r: ]4f-7 Wf* JVM' JVNJ |*7 J<T| ]9e5 *V e<n (rorr :!:ro eniploNmen: ii- dull. < 'lai-.n- c lapsed period'i 'Also had mf'0(hfliom rV iO la*c< pleuV plague 'Or. Pan II o' dea:h cenifi,a:r recorded on the death certificate' Higher death rates from lung cancer following exposure to chrvsotile have been previous!) reponed The possibihtv exists that the criteria used b> some railroad doctors in the diagnosis of lung cancer, asbestosis. and silicosis mas have lessened the recording of such diseases on death certificates For companv A. the criterion for one of the phvsiciam was that a diagnosis of silicosis or asbestosis could not be made without biopsv and examination of the tissues bv a pathologist. Table VI provides data on the following 10-vear period b> a successive vear-of-hire cohort (193( -19391 Thn is shown as supplementary information to provide a visual display of how economic condition*- (the Depression that occurred after 1929) influenced the number of workers exposed For five vears no railroad machinists were hired and onlv a few were hired in the other sears Excluding 1939. thi> meant that onlv lb machinist' had been hired through 193b For the 7 hired in 193-. there ' one death due to lung cancer at age 6b. after an interval of 30 vear> since first empinv men; In I93v. there were 4 lung cancers and one mesothelioma among 26 dej'h' in a cohort of 34 The 1939 sub-cohort wa' of particular interest in term' of reproducibiiitv and range of latency period because 24 of the 34 machinists were hired on the same da> Within this group, hired on.the same da\ at the same age. there wa' one mesothelioma and two lung cancers One machinist hired the da> before (age 29j aKo developed lung cancer, as did a machinist hired at age 23 one month later The latency period for the lung cancers of the 1939 subcohort (Table Vi ranged from 23 to 46 vears. For the 1930-1939 cohort there were 648 Marxw TARLF VI. $uecf>e Cohort' b 7 ear of Hire and Agt From 1956 to I9J9 Among Railroad Machinist.' b> Cancer Cause of With ______________________________________ Number in cohon Numhc1 of deaths Mat of hire IWVu |U'*|.|9 -. juu 1935 IWp IV*' IQif. 40 70 7-- 5 4 0 1-- f Vv Toty <2 40 Caue of death Mesothelioma* Cancel of lunp Ape at hire 39 tv 1 tt 11 5 y. 2 Cancer of panrrea* Cancer of Madder Cancer of pro'tak Mjelopennu' leukemia CarcinomaiOM'* ipnrr.ap. untnov.ni Tota' cancer* ! 35.V 48 $y 1 36 51 ar* t 2 11 V 1? 'Pan 11 or Death Cenifi.ak ''include' MelanoMa'iorns with enla'ped li'et 7 ABLE MI. Case' of Mesothelioma Among Railroad Craft Workers. Employed I92&-1929 for Compart* A 1*45 Cohort Ca'e 1 t 4 Craft Boilermaker helper Machiniv; helpe'*' Boilermaker helper Boilermaker helper Mar of hire ion iv;; iv:< iv;?r Number hired } 6 M U Ape at hire t< 38 21 2} Imenal tears 4f 36 5.t 59 Ape at death 75 76 74 8! Yea* of death JVM 1958 19*8 1984 Employee' compar.\ A not tn eohon . 5 Machinist 1926 6 Executive rencineen' iv;p 7 Boilermaker* 8 Enprne ca-penter 24 44 6* 1970 IV 39 57 IV65 6V 1958 66 1959 'identified h\ Otto f Ashestosi' also two cancer' of the Madder and a melanoblastoma The three cases of carcinomatosis. pnmarv unknown, out of 13 cancers represent a critical loss of information Table VII provides information about mesotheliomas amonc different worker crafts of company A that relate to our suid) b> year of hire (no special study ua^ conducted i. The occurrence of cancer in a boilermaker helper hired in 1921 (only 1 was hired for (he yean complements the successive cohorts amonp machinists, providing a continuity for & successive years. 1920-1927. Data on workers in the other crafts hired in 1922 and 1925 who developed mesothelioma supplement the machinists" observation for those years c one Railroad - iw'-s (i -- |OVW \4 2b r Af' xx ! XX XX fs AX Xj XS. Xj I - 1 1 C` X 1 9 ]' plpytd 1920-1929 for Apr ai death lb 1A M of death 1Q> 1 |95S JO'S IOS.1 , 5" t* |CP(l }9f-5 195S |oyu fne three cases of n: a critical loss of >ng different worker no special study was Tired in 1921 (only 1 among machinists, ta on workers in the icma supplement (he Relative Risk of Mwtihclinms Ajnonp Railroad Machinists *49 The most striking observation wa' the indication of relative risk to size of number hired for that year among the boilermaker helpers (cave 3. 4> The 2 deaths due to mesothelioma were derived from only 14 hired in that category in 1925 in company A ai that facility One of the death certificates, in addition to mesothelioma, specified "ashesio'is mans year'*' m Pan 1 of the underlying causes of death Case 5. an employe machinist of compam A in the work facility of the adiointnp state, had been hired m 1926 The diagnosis was made at the same company A hospital He died in 19*0 at ace 68 Case 6 was employed at the same location and facility of compam A ir 1926. first as a laborer and subsequently as a machinist hefper. in 1928-1932 he was lappinp boilers of the steam locomotives From 1933 on. he was assigned to nonshop viork at various geographical locations of company A. with a continual rise into management positions After war service <1943-19461 he returned to his original place of employment a* an executive engineer until 1963. Case 6 is of particular interest because it illustrate' two basic principles First, m epidemiological studies, the last job un this instance, executive) can be misleading because it docs not reflect the early years of exposure to hazardous and carcinogenic material (asbestos) that occurred in the work environment Second, that the carcinogenic n>k continues after the exposure to the carcinogen has ceased Two clinicians for companv A hospital attended and signed 11 of the mesothelioma death certificates, 8 for machinists and 3 for other crafts The exposure and nsk of all craft' and workers to asbestos insulation material, including boilermakers tn the steam locomotive era. have been previous!} described (Mancuso. ]983). Liebcn f!96`J cited the occurrence of a mesothelioma in a railroad boiler maker who had applied asbestos insulation on steam engines for 25 years. The identification of the mesotheliomas among the various crafts demonstrated again a basic public health principle known for decades, that the disease follow.' the trail of the exposure, whether to infectious, toxic, or carcinogenic agents, regardless of the location of the exposure, the job title, or type of industry Selikoff (1964J referred to this concept "floating fibers do not respect job classifications--insulators share their exposure with other trades, eg. electricians, plumbers, sheet metal workers, sreamfmers. carpfnier>. boilermakers, foremen and even the architect.** Similarly, beyond the workplace, children and family members of asbestos workers have developed mesothelioma' and asbestos related diseases following limited and intermittent exposure. DISCUSSION In the examination of relative risks from various form' of a'besios. there is a need to put into proper perspective the references which h3ve beer, made to ore contaminants, which have been identified as derived from the chrysotile mines The epidemiological investigation' of health effects that pertain to chrysotile are solely directed at the form of chry>onle that has been provided in prior decades from the Canadian chrysotile mines for commercial distribution and use in the United States and elsewhere. The chrysotile. as supplied and distributed throughout the United States, was not processed in any way to remove any ore contaminant before use and human exposure occurred in essence, the mesotheliomas which have occurred and 650 Mncu*n arc ihc subject of epidemiological studies relate to the form or type of chrysolite that via'' provided for commercial u*>c On one occasion Wagner. who reported the major stud) on mesotheliomas, stated "all mesothelioma* caused by commercial asbestos base been due to crocidolite." |I979] although he did not always espouse this view jGiKon and Wagner. 1967) Experimental Observations - Wagner ei a! 119fc0j conducted extensive experimental studies on animals w nh all types of asbestos. b> intrapleural innoculation and b> inhalation. Wagner observed in summary. "These experiments produced some surprising results, in particular, although the crocidolite sample had produced more mesotheliomas than did the chrysotile after intrapleural injection, after inhalation, the sample of chrvsotiie from Canada produced a*.mans mesothehonia* as_did crocdolitc. this was in spite of the fact that the retention of chrysotile dust in the lungs wa* very much less than that of crocidolite. This experiment has cast some doubt on the epidemiological evidence that crocidoiite is much more hazardous than chrysotile as far as mesotheliomas are concerned " . Subsequently. Wagner [~L9kfe) referred to a series of cases (12) of mesothelioma in a preliminary investigation of the chrysotile mine and the production of commercial chrysotile in Cyprus which had occurred among individuals exposed to the chrysotile mine dusi w uh ore contaminant * (containing tremolitei similar to those observed from the chry sotile mines of Canada A series pieapenmsars have.cansiiiemJj demonstrated that chrysolite, more than_anv other form of asbestos^ gejMp the .pleura and is retaioed-tn the pleura as the basis of subsequent..disease x Le Bouffant [ 198D1. in a study of human tissues, noted a preferential migration - of chrysotile fibers_lo,.lht.pieura. with a significant increase and accumulation in the pleura, in comparison with the lung parenchyma "The median percentage of chrysotile fibers was in the lung and 339J in the pleura." In one series of cases, the median concentration in the pleura was 3000 fibers tchrysoiiJe> per gram of dry tissue. ' Sebastien et al 11979. 19801. in similar studies on human tissues, also demonstrated that the retention of asbestos fiber* in the parietal pleura was type- and size-related, that inside the parietal pleura most of the fibers were short chrysotile fiber*., and that lung retention wa* no: a good indicator of pleural retention .. Yiallat.ei aL_(I98fv]. with intratracheal injection of small amount* of I'iCC chrysotile. demonstrated that the shorten fibril* reach the pleura very rapidly and can be retrieved from the pleura) fluid of rat* within one month >. / HanngJonJ)9M). m his review on animal studies, cited that large numbers of ihon lower aspect fibers may induce mesotheliomas and that superfine chrysolite w.as the most carcinogenic of all the materials used - x Mowe et al..419b-] found that there was no correlation between latency and the total lung fiber concentration"in malignant mesothelioma. Identification of Mesotheliomas Of particular significance are the observations by Chqrg et aL.tlSS^.l who identified, in one hospital.'6 cases of pleural mesotheliomas in 90 consecunye hnsonic that n mesotheliomas. inc been duo to . icw |GiNon and n on animals with Wagner obsened jits. in particular, mas than did the of chnsotile from u a** in spue of the .h less than that of ;>ologica) evidence mesotheliomas arc ) of mesothelioma non of commercial ed to the chnsotile iosc obsened from i\ chnsotile. more m the pleura as the .*) mal migration jccumulaiion in the itan percentage of one senes of cases, ie) per gram of dn uman tissues, also leura was tvpe- and ere shon chnsotile al retention I amounts of I'ICC ver> rapidlv and can a? large number' of erfine chnsotile wa' Aecn latencv and the : et al. 11984} who s in 90 consecutive Krtaiiw RtsL of Mesothelioma Among Railroad Machinist* 651 autopsy ,n the period of late !9bo to 1985. of lone-term worker- 4 the ThcJford mines of the Quebec chnsotile indusin tin contrast. Hochbcrp 11951) had estimated that there had been between I per IOtM and I per lO.(KK) autopsied in the general population ) The mineral content in the lungs of 5 of the 6 death' w ith mesothelioma' identified b\ Churp had onlv chn sonic and ore components These observation' eoncerninp chn sonic in the lung' were found even after 22 tallowing for correction in case No 2i scars since last work exposure to chn sonic, and after an interval of 3i_48 vears between initial cmplovment and death Earlier. Gibb' (1978) had specificalh cited the need for such a studv of "autop'.v materia! from persons who died at vanou' period' after cvpo'ure to chn sonic to see how long the fibre remained in the lung " It is evident, that chn sonic remain' and that the cancer risk docs not cease after exposure stops The Churg ea'C' and the mesothelioma eases that occurred after the age of 65 in tho sene', a' well as in those workers who ceased asbestos exposure at earlier age'. aNo demon'trate this point The Churg et ai oh'enation of 6 mesotheliomas in 90 autop'ie' during less than 4 \ear' among the Thctlord a'hc'U*' worker' i' aNo significant because McDonald ei al [1980] had reported onh 15 mesothelioma' among Thetford chnsotile miners in Quebec during 19 vears t 1960-1978). These findings emphasize the necessitx of ascertaining other cases of mesotheliomas which max have occurred before, during, and after the McDonald et al and Churg et al lime period' of observation A few instance' will be cited Identification of mesothelioma' is ha'icalh difficult, but this mav have been more difficult for some of the mining and sunounding rural areas in Canada because of limited professional resources Thi' wa' referred to hv Selikoff et al [196-4J in discussing the various areas of the chnsotile mines in Canada In Asbestos, a town with one of the largest chnsotile mines in the world, there is no pathologist, no hospital laboratory postmortems are.almost never done. Montreal and Quebec Citv are at least 75 miles from the areas in question and are not common!) utilized hv the local population Serious cases are sent to Sherbrooke 40 miles away The onlv hospital in the Asbestos area is a small one used for maiernitv purposes (at least 2 vears agoi. Canier. physician for the asbestos companies clinical facility in the Quebec area, in reporting on death' before 1950. identified 2 cases of pleural .mesothelioma associated with Thetford chrvsotik mining operations 11952] One asbestO' worker had been emploved for 2b vean Tm- second identified h> autop'\ in 194si (referred to consultant pathologist \orwald ir the Inned Statesi. was that of a companv official, the treasurer of the Asbesto' Companv Thetford Mines, whose exposure wa' recorded as office work from with a latencv period of *9 vears [Castleman. 1986) (Wagner e: a! | N(o; referred to the 2 case' of mesothelioma' h\ Carrier from the Canadian Chryotik mines i It i' apparent that unless resident' of the area near chnsotile mines were accorded similar exceptional medical assistance of autopsies and special microscopic examination of the tissues h> a consulting pathologist, it is verx likely that mesotheliomas would not have been detected and recorded Braun and Truan 1.1958]. in a studv of ashewos miners (Thetford and Asbestos) 65: Mtncuv. in Canada, cued a.dvathjiuc tomcsolhdu>nui.hsdL*C.C0 19>br 193.7 The identification as to whether it ua<> from the Thetford or Asbestos mines was not given Death certificates are not an accurate reflection of the full number of mesothelioma'* which have occurred, for several well-known reason** Mesotheliomas ma> have been identified at some point m time bv biopsy, m hospital records but not recorded later on the death certificate at another location with a different doctor, as previouslv mentioned Similar!), information derived from autopsies mav not be recorded on the death certificates (International Classification of Disease. Intones, and Causes of Death did not include malignant mesothelioma until the eighth revision ) All of this is related to the basic problem of the infrequent) of autopsies in various rural and urban areas, and the need for the particular serv ices of pathologists Further, cancers which have been reported on the death certificate as pnman site unknown, or attributed to some other site, have been found on subsequent review of the microscopic slides b> consultant pathologists to be mesotheliomas Selikoff et al 11979). in a senes of reports utilizing all medical resources, demonstrated that the number of mesotheliomas wav far greater compared to what, was recorded on the death certificates among workers exposed to asbestos, and similar experiences have been reported b> Neuhouse and Wagner 11972) Nevertheless, death certificates in research arc ven important A complicating factor in Canada was the policv of the Quebec Mimstn of Social Affairs, which has insisted on permission of the next of km before providing a death certificate, with cause of death, even for research purposes (Nicholson et al . 1979) Consequent!). death certificates which could be critical tn a research stud) could not be obtained from the appropriate relative if tbev had moved, died, or could not be found. Death registration tn Quebec first became compulson in 1920 {McDonald et al.. 1970). The most important fundamental difficult) in prior decades has been the proper diagnosis and identification of mesotheliomas, and the underreporting that occurred for this type of rare cancer. This was one of the major considerations of the ll'CC Working Pan) on Asbestos and Cancer 11965}. which was directed at the interna tional coordination of research on asbestos. A senes of recommendations was made w hich proposed that reference panels of qualified pathologists t w ho w ould review the cases of other pathologists) be set up on a regional, national, and international basis to assist in the diagnosis of mesothelioma and other turnon* associated with exposure to asbestos ' In view of the uniqueness of the pathological services required, as well as the other factors, it is reasonable to conclude that the magnitude of undendemification.of mesothelioma'- m some penod> of.time may have been far greater than realized in the rural chnsotile mining area'- of Canada and would tend to underestimate the relative ,lrisk of chrxsotile.tr, the induitioii.of mesotheliomav Dust Estimations In the consideration of duM estimates and dust exposure?- in the earl) vears relative to chnsotile as well as other forms of asbestos, a considerable number of questions have been raised av to the appropriateness of such guesses and extrapola tions about exposure levels in prior decades tas they may relate to subsequent development of lung cancer and mesothelioma). Selikoff (1978] was doubtful about the validity of the dose*dust estimate in the Quebec Stud) in view of the infrequent and fragmentary dust measurements made in earlier years. Wright (1978) was also -The identification \cn v .ull number of ns Mesotheliomas 'ital records hut noi dificrcni doctor, as opsu's may not he f Disease. Imuries. ia until the eighth cnc\ of autopsies m tees of pathologists .ate as primary site jbsequent review of *mas Selikoffetai monstrated that the . as recorded on the ar experiences have death certificates tn as the policy of the ion of the next of km or research purposes i could he critical in relame if thc> had Quebec first became has been the proper so-mp th3t occurred ns of the Jl'CC ected at the internatendationx was made ho would review the )d international basis *caiceJ with exposure juired. as well ax the jndendennfieation of er than realized in the restimatc the relative e> jn the early years rtsiderablc number of uesses and extrapolarelate to subsequent sj was doubtful about iew of the infrequent right 1)97$] uas also Relative Risk of Mesothelioma Amonj Railroad Machinin' *5.' ven much concerned w ith the attempt' at "reconstruction of exposure 30 years apo-- because this hj' a high deprec of uncertainty-- considerable variations occur in plants from day to da>. and even hour to hour and that intermittent exposures that nupht be ven significant biologically. nupht appear in the data as low exposures if presented as time weighted averages " Further, extensive problems exist relative to dose estimates because of the marked dificrences and chanpes in air sampling instruments, and the decree of eflecmcness of various method' and evaluation techniques over the past decades The problem of dust estimates in prior decades is compounded bv the known marked human variation tn biolopica! response to asbestos and other carcinogens Tho has been demonstrated in the present study and a series of , illustrations cited in the result' ' A panel of scientist' of the I S Government (NIOSH-OSHA) Asbestos Work Group |I980] concluded "that there was no evidence for a threshold or for a 'safe' lev el of asbestos exposure." after citing that "human occupational exposure to all forms of commercial asbestos fiber types. both individually and_in_\jixipus combi nations have bejLD associated-wjth. high rate*.-of _ashc>4ost^-iung cancel__ and ,(mesothelioma )" Problems in Epidemiological Studies In terms of mortality experience, the basic concept of mortality surveillance of workers employed in specific industries has been known and applied for decades by insurance companies Hoflman |)91b) cued increased nsk of asbestos workers, leading American and Canadian iiie insurance companies to deny insurance coverape for such persons. Continued evidence of this risk was a J930 survey of asbestos miners in Asbestos and Thetford mines m Canada, in which 42 cases of asbestosis were found among 195 asbestos miners, and an investigative report {1949) which cited extensive effects of asbestosis. the deaths, and air pollution from chrysotiie mining operations (Castleman. 1986. Trudeau. J974J. Of particular interest is the Braun-Truan study [1958] of lung cancer among miners of the Asbestos and Thetford mines in Canada, which provides illustrations of some of the problems of design, analysis, and reporting of results, which can understate the cancer risk These are cited in broad terms, as necessary background in any evaluation and estimation of cancer risk from chrysotile. The study consisted of a combined cohort of 5.958 (6.091. less | tt Josi to study). all of whom had at least 5 years or more employment, were alive in 1950. and were followed for 6 years through 1955. Tnis automatically excluded the mesotheliomas of the Thetford operations that died before 1950 (2>. as cited by Canier |1952]. Other basic problems affected the evaluation Enterline |!9M] pointed out that an inappropriate statistical derivation of the expected rate for lung cancer was used, which submerged the positive lung cancer finding-, tha: th; same comparable diagnostic criteria (of confirmation! essentia! to the anaiy >- w js no: used both for the study group and the control group M^ncuso |IV65| cued the very short period of observation, uhich substantially limited the extent of the identification of the lung cancers, that the designated exposure categories were basically not tenable and therefore inappropriate for correlation Selikof! |1964] also cued the dilution factor in the cohort, relative to age. duration, and lung cancers, the limitations of the availability of medical services: and problems with both the diagnostic and exposure criteria. Sabourin [1957J. in referring to the prepublication Braun-Truan report for the 654 MncuM> Quebec Asbestos Mining Association, noted lh3i cancer statistical data "was sen poor tn the Pro\ncc. as the report of cancer as cause of death is not compellable h> lavs. \ g . tuberculosis must be reported " In fact, occupational cancers when thc> do occur ma> not be reported in the literature Hueper | I9M j. citing the published article U95M. pointed out that the Braun-Truan data "had missed M cases of asbestosis cancer of the lung studied at Saranac Lake Laboratories." Despite all these constraints, the prepubhcation Braun-Truan data identified a positive statistical association between lung cancer and asbestosis. but thiv unfortunate!) did not appear tn the published paper. Another problem was that the marked differences between two groups in a stud) can be submerged when combined and used as a single cohort, which affect the anahxcs and inicrpretaiions that can be made This related to the difference* in the exposure categories for the Asbestos and Thetford miners as recorded independent!) m the prepubbcation report These were then combined and the differences in the Jung cancer rates were averaged in the published report, lessening the statistical sensitivm m control comparisons. Epidemiological studies have the complicating problem of competing causes of death, in which individuals, workers, or residents max die of other causes, whether of asbestosis. or other disease or injuries, before the latencv period has been met for the development of lung cancer and mesothelioma Similar!), it is also recognized that monahi) per se. although important, is onK a verv pross indicator of health effects; significant diseases mav be sustained in prior sears b> those exposed, but not identified or reflected on the eventual death certificates. A further fundamental problem has been the use of the general population, with higher actuarial death rates than employed workers, as a control to derive the expected rate. This can be misleading and mask positive cancer findings among the workers studied. Chrysotile Exposure Mesotheliomas have also been reported following exposure to chrvsotile in the manufacture, removal, and installation of brake linings; these commonlv have been made with chrysotile asbestos. The pervasiveness of the automotive industry with associated repairs and the ver> large population of worker? who mav have been exposed in prior years, represent a major area of concern. The seriousness of the problem is reflected in a review bv Castleman et a). 11970. 1986) on asbestos disease among brake repair workers that documents a series of reports in the United States. Canada, and Europe. The following citations represent illustrations of particular aspects. t.apogr-jn.-t M.-faugh^) j)OS',j reported a pleural mesothelioma in an auto repair man who had worked for mam \ear>. often replacing brake linings The latencv period since first exposure and death was 2" years Chrysotile wa*- identified and confirmed bv electron diffraction anal)sis and no amphiboles fiber? were found It was estimated that I ng of chrvsotile was present per 5 g of u et lung parenchvma Tflp ft al H9&31. in a report on mesothelioma in the Connecticut tumor registry cited - cases of mesothelioma tpieural and peritoneal! in women (clerical workers) who were emploved at a friction products plant that manufactured brake linings using onlv chrvsotile asbestos Of particular epidemiological significance was the fact that the mesotheliomas were not cited on the death certificates and therefore were not included in the death certificate anahsis of 122 women w ho died in a cohort stud) of that plant (McDonald. 1986). i jjta "was vcrv s noi compellable bv cancer* when thcv do the published article 4 case* of ijsbcs\OM'' Despite all these a positive statistical natelv did not appear lerences between two d as a single cohort. This related to the Thetford miners as e then combined and he published report. f competing causes of other causes, whether nod has been met lor it is also recogni2ed ss indicator of health hose exposed, but not further fundamental r actuarial death rates d rate This can be ers studied ire to chrvsotiie in the common!) have been motive industry. with who ma> have been he seriousness of the 6) or. asbestos disease in the L nited States, 'tranons of particular oihehoma in an auto -.g brake linings The "V'-ouic via* identified ic' fibers were found wet lung pjrenchvnij hi- Connecticut tumor j!1 n women (clerical -i manufactured brake 'Cical significance was mficates and therefore n who died in a cohort Relator Risk of McvMhflioma Among Railroad Machinist 455 '' Vianna _?nd Pol:m_|_L97bl. in a studv of spouses with indirect, minimal, intermittent exposure to asbestos, cited 3 mesotheliomas that had occurred in women at ages 40. 77. 7b. whose husbands were brake lining workers. ./ McDonald ei al | 1970) identified two cases of primary malignant mesothelioma tumors m Canada, in persons who had been brake Umng mstailcrs. and one who had worked in brake lining manufacture Godwin and Ja_gatK 1.196b) reponed a case of peritoneal mesothelioma in a worker who wove brake linings made from chrvsotilc for three vears and who died at age 43. Mancuso | 19b3j reported a pleural mesothelioma in an auto mechanic who died in 1969 at age 5b Clinical Epidemiology and Medical Economics The findings of this studv demonstrate a very high relative nsk for those exposed to chrvsotilc asbestos in the development of . mcsubelioma with one mesothelioma eventual!) occurring, for even 13 machinist*. Juied in-thc vjuts 1920-1929 b> railroad company d The human experience, the manifestation of the disease, and the consistent repeated development of a specific rare cancer such as mesothelioma in successive, cohorts following prior exposure to commercial chrvsotilc asbestos illustrate the basic principle that the nature of the asbestos exposure was sufficient for the induction of the mesotheliomas, regardless of the theoretical discussions and posturings surround ing the development of the cancer process This investigation also demonstrated again the importance in medicine of `clinical epidemiologv" in the identification of occupational cancers bv clinicians Historical!). virtual)} even occupational cancer was first identified bv a clinician or surgeon In this instance, phvsicians associated with the same railroad hospital of companv A consistent!) diagnosed mesotheliomas, a rare type of cancer among workers employed bv the same companv in a small citv. The clinicians and the thoracic surgeon unfortunate!) did noi publish their findings of mesotheliomas that had occurred among the railroad workers. This illustrates the basic fact that occupational cancers and diseases can and do occur in specific industries and mav not be reported in the medical literature the absence of such reports does not mean that the specific occupational disease or cancer hav not occurred It is hoped that this paper will encourage phvsicians in industrial medicine in the application of "clinical epidemiologv" and in the publication of their findings in the medical literature. A final basic medical observation and concern is the occurrence of occupational cancer among the elderly Of the 14 mesotheliomas m the cohon studv. 12 died at ages 65 and over, as well as 7 of b in the craft devignat.on* The occurrence of cancer in the older age group, because of th; la:enc> period, hav been observed in virtual!) all occupational epidemiological studio* of a wide range of industrial carcinogenv The substantia! implications for medual economics, the interrelationship of govern mental medical care and cost', and the importance of environmental controls of prevention in the carl) work vears of life warrant a mator national investigation ACKNOWLEDGMENT This studv was made possible through the support of the Environmental Cancer Section. International Radiation Research and Training Institute. 6N> Mancuvo REFERENCES Baur. JH (Ik5i Communication Braun DC. Inian. TD i |95hi An epidi mioinpual stud> ol lunp can.ct in asbcstt" miner* Auh of JnJ Health Sol |7pU-65? 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