Document 0aYn29ZNV4OLdJn0kd8X6Z0J

FILE NAME: ZD^D/ DATE: : DOC#: ^D/ DOCUMENT DESCRIPTION::ZZZ^Z >ZD .:~ .. :::: ../ Rcpri11ttd from the A. Jf. A. Archhl's of fod11stria! Health J1wc 1958, T' of. li, pp. 63./-.:653 Cop~righf '19.~~. by .-1 mcrican Jfcdical .-1ssociafiJ11 An Epidemiological Study of Lung Cancer in Asbestos l\liners DANIEL C. BRAUN, M.D., and T. DAVID TRUAN, M.A., Pittsburgh E~er since the pronounced increase in the incidence of lung cancer among males became apparent, there have been attempts to associate it with one or another of the various elements in the emironment of man. The approach used by some \\orkers has been to suspect one or several substances and then set about in an intensive search for lung cancer among persons who haYe had any exposure to those materials. In this connection, Smith 82 writes: "The tendency of authors reporting the coincidental occurrence of primary lung cancer with silicosis or with any other theoretical etiologic conditions, has been to emphasize the percentage relationship in extremely small series of cases, with control cases which are not in any way comparable." It would seem ineYitable that asbestos should come under scrutiny in this manner, because prolonged exposure to this material is known to cause a specific type of pneumoconiosis, ~d because persons who show this form of pneumoconiosis often come to autopsy and pronde a ready source of material for study. It was in this way that reports of the simultaneous occurrence of lung cancer and asbestosis began to accumulate after the report of a case by Lynch and Smith 68 in 1935. Within the next 10 years, about 15 additional cases were reported, and in 1954 Merewether 76 revie\\"ed all deaths from asbestosis recorded in England since :\larch, 1924. Lung cancer occurred in 16% of these cases. Gloyne,41 Accepted for publication Jan. 20, 1958. This studv was made possible through a grant from the Quebec Asbestos Mining Association. ~fedical Director (Dr. Braun) and Statistical Consultant (Mr. Truan), Industrial Hygiene Foundation. whose \\"Ork is also frequently referred to as establishing a connection between asbestosis and cancer of the lung, reported in 1951 that cancer of the lung was present in 14.1 S:c of asbestosis cases examined by him. In 1941, Xordmann and Sorge 78 claimed to ha,e produced lung cancer in mice which they exposed to asbestos dust. Since 1951, additional cases of cancer of the lung coexist'.ng with asbestosis haYe been reported. and. according to Hueper :.s about 100 such cc.ses had been reported up to 1955. As a res:Ilt. an association between the two diseases appears to have been accepted b, man, a:Ithors. and seYeral \\Titers were usm~ g the. t'trm " asbestos1.s cancer" o f the lung. Werber. s1 in 1952, stated categorically that in. 7<;( to 177c of cases of asbestosis, after a latent period of about 1y;; to 20 years. carcinoma becomes estab- lished in the lung. On the other hand. not all authors accepted this alleged assoc1at10n without resenation. Sau;ie ~" in 1939 reported that he had discoYered no cases of lung cancer among 620 cases of asbestosis which he had examined: and in 1942, Holleb and Angrist 4& expressed the opinion that the number of cases of asbestosis with lung cancer was too small for statistical eyaluation. In 19..+7, \Yegdius 88 reported 126 radiologically diagnosed cases of asbestosis among 476 workers in Finland, and found no cases of lung cancer in this group. Goldblatt and Goldblatt in their section of Merewether's latest book,44 state: "But at no stage in all these impressive researches was any clue obtained which might haYe offered any sup;-ort to the possibility that asbestos could act as a carcinogen. There 634 - - -------~ ~"l"""~oJ-.. ~-- ---.-o,- .....- .. _.._..--.. ~-..,.~--- _.._,M_~~-~-_ _._ _.,,__ _, . . __ _ LUXG (A.\'CER JN ASBESTOS MINERS is .no reliable criterion by which one can anticipate carcinogenicity and, as is wdl "scheduled" areas, by which is meant, "those areas where processes are carried on known, relatively minute changes in the which ''"ere scheduled under the Asbestos structu:-e of a chemical carcinogen are suffi- Industry Regulations of 1931 as being cient to diminish or eliminate carcinogenic dusty." action. If asbestos is indeed to be regarded as a carcinogen, the need is felt to demonstrate some property which can be regarded as something more than inertness." These authors adYance the theory that, until some more experimrntal eYidence of direct carcinogenesis by asbestos or a decompo::.ition product of it can be obtained, asbestos might be considered as a "co-carcinogen" which only induces a further deyeJopment of a preneoplastic condition brought about by something independent of the asbestos, such as an endogenous factor. Thus the literature, "hile tending to support the thesis that asbestosis is in some way related to the deYelopment of lung cancer, is by no means unanimous. Altogether, if is perhaps more confusing than er.lig:1tening. A careful reYiew shew~ tkt the majority of the reports are clinical and not epidemiological. They lack many elements necessary for the application of epidemiological techniques to their content, and most of the authors do not make claim to haying done so. \Vhat has happened is that succeeding authors have drawn conclusions and generali.zed beyond the scope of the works which they quote. Nowhere, for There is, furthennore, a complete lack of definition of tenns as used in the published literature. For example, the term "asbestosis," as used. may refer to changes obsernble only by microscopic examination of the lung tissue. or it may mean a radiologically detectable condition. :'-lost of the publi::.hed reports obYiously included women among their cases, but some of them do not giYe the mm1ber or proportion of..."omen inYohed in the study. There is also a lack of uniformity as to ,,hat type of expo;:ure most studies have dealt with. Of 99 cases enwnerated bv Hueper :,~ in 1955, only 10 appear to ha;e originated in the l"nited States, and 7 in Canada. Some of the earlier reports apparently included asbestos miners, but it can be assumed. since 82 of the 99 cases had originated in England, and since no asbestos mining operations are carried on in that country, that most of the reported cases haYe imohed "orkers in the textile or fabricating indu;:tries. Such factors as smoking habits, family history of cancer, length of time in the industry, and age oi the individual case are also notably absent in the majority of these reports. example, have we found references to a With this understanding of the limita- population of asbestos workers, although several authors who. haYe quoted the ob- tions of the existing literature with respect to epidemiological generalization, it may be sened incidence of lung cancer in autopsies of value to consider in somewhat more de- of persons who also had asbestosis imply tail some representatiYe earlier publications, that this incidence applies to asbestos work- a few of which were referred to briefly ers, generally. We haYe likewise been above. unable to find any study which actually One of the most detailed studies and one calculated the incidence of lung cancer which deserYes the most serious considera- among a population of persons who had tion is that reported by Doll 28 in 1955. asbestosis, and not just those who came to This study reviews causes of death among autopsy. With the exception of a paper asbestos workers based on coroners' rec- by Doll,28 none of those reYiewed gaYe any ords. It also attempts to estimate the risk data on exposure and dust concentrations, and eYen Doll's paper merely mentions by studying records of men who worked for at least 20 years in exposed situations. . ' - - - - -..._........_ \'>h:ch 1;: meant, "C~ arc c;1rried on ,nder the :\sbestos rl 1931 as being e. a co1111 ilete lack ~ used in ;he pubt:xample. the tenn Y reier to changes H'OJ ic examination :i;ay m<:an a radiour 111. \ rej Qf"iS r1bYiously : their l.'i!~e~. but 'i\c :he nu:nber or .'.;\er! in the :"tudy. i ui:iic.;m;ty as to : r1< ,rudies ha\'e c - enu:ntrate<l by i 11 :,rir,"'ar to ha,e i Stde. ;,nd 7 in c;, :-Lcr :-eports ap. - :~1iner;:, but it ...:2 (Ji the 99 cases .:nd. and ;:ince no n- ::re cc-.rrie<l on < ui the reported hTs in the textile 'i:1; habits. family 1h o! t'.me in the :rnli\i<lual case are . :na_iority of these i116 oi tht limita- r;:!ure \\'ith respect :>zation. it may be r1newhat more del'.: :-lier publications, rc;em:<l to briefly :,.J ,:tu<lie;: and one >criou, considera- y D(Jll ~~ in 1955. .. _ "i <11:ath among 'll cor(Jners' rec,, c-1i111::te the risk :.cn \\"ho \\orke<l ' '; 1 erl ,:ituations. 635 .4. Jf. A ..-iRCHIITS OF l.YDU'TRIAL HL.4.LTf-J Doll concluded that lung cancer was a specific industrial hazard of certain asbtstos workers and that, after 20 years of expo- sure. the risk is 10 times as great as for the gen<:ral population. This article is important for several reasons, in addition to the definite conclusions at \Yhich it arri\'es. For example, it begins by stating that "in Yiew of the infrequency of asbestosis, this large number of cases (61 cas6 of lung cancer) suggests-but does not prO\e-that lung cancer is an occu}'ational hazard of asbestos workers." :\either this article nor any pre\'ious one \\hich ,,.e haYe examined presents any figures to proYe that asbestosis is an infrequent occurrence. Estimates of the number of pcrsons potentially exposed to asbestos clust in the lnited States alone yary from 10.000 to 35,000, and the i1Kiclence. of asbestosis of any degree migl~t be higher than Doll imagines. This study, like so mam others, in\'ohes autopsy records. The number of persons inrnJyecJ in the statistical analysis is only 113, reprt~enting onl\' l.042.2S man-yea;s 11f life. It is also tru~ that in selecting. men 1:ho had been employed for at least 20 n:ars. the stud\ automatically excluded ~hose who died. from other ~auses after shorter employment. Another reason why this publication is of importance is a statement which it contains to the effect that "the strongest eYi<lenct that it (lung cancer) may be a hazard (in asbestos workers) has been produced Ly :\Ierewether and by Gloyne." In 1951 Gloyne 41 presented a re\'iew of 1205 autopsies on persons who had \\'orked in Yarious dusty occupations. This number included 132 asbestos workers of \\horn 121 showed "pneumoconiosis"-~re sumably asbestosis. Priman cancer of the ~un~ occurred 17 times in' this group, an umclence rate of 14.1 ~c for lung cancer among asbtstosis cases coming to autopsy. There were in his series 796 cases with silicosis. and 6.9C;(; of these also showed pri- mary cancer of the lung. The incidence oi 636 lung cancer in other forms of pneumoconio- sis ,,as 6.i~c. and in 169 cases \\hich proYed not to haYe any type of pneumo- coniosis it wa~ 8.3o/c. Gloyne considered "the mortality of the asbestos \\orkers" to be "disturbing... First of all, it is obYious that the paper does not deal with the "mortality of asbestos workers,'' and secondly. it must be borne in mind that all of Dr. Gloyne':; cases \\ere submitted to him for study because the findings were unusual ior uncomplicated pneumoconiosis. 1t can reasonably be assumed that cases, including thu,;;e of asbestosi,:, in which the finding~ \\ere not considered unusual wtre not :cent to Dr. Gloyne ior examination. .\s a mat- ter (Ji fact. in the same paragraph in \\hich he eXiJresses co1Ktrn OYer the incidence rate in a:'testosis. Dr. Gloyne himself ]'Oints out that tht rate for lung cancer based on necrop:-ies at the London Chest Ho~pital was 21.Y( while the figures of iht J\.egi:-trar-General showed unh 2.-+S{. He thus recrJgi1izt:<l that autopsies ~n a ctr tain selected gr(JU\ oi cases were not rep res<:.'ntatiYe r>f th<: general population . . It \\'Ould "e<:.'m. then. that notwithstanding the \aiue uf Dr. Gloyn1:'s work, its importance a:'. an index of the preYalence of lung cancer in asbe~totics has been misinterpreted by :come \\hrJ ha\'t: quoted him. All that it really shows is th<: fact that in a group of 121 cases, selected for special study pri- marily because they seemed abnormal bY preliminary t'Xamin~tion, 17. or 14.1 <Jc. had lung cancer. :\Iere\\ether 7 ~' in 1947, in the report of the Chief Inspector of Factories. reYie1,ed all cases reported between 1924 and 1946 in which asbestosi:; \\as the cause oi death or a coexisting condition. This \\'Ork was lakr extended to include all such cases reported up to December, 1954, by which time. there \\"ere 3-l-..J. deaths, including 205 mal6 and 139 fem ales. Among them ,,ere 55 ca,;6 I 16~(:) of cancer of the lung, 41 in males and 14 in females. It is quite pos.sible that a large number of a:-;be~totics who cJ'.cl not die of their a:->besto<~. or in \\ho~e 1u1. Ji, Jm:c, 195S --~ " . mmra , --"' ' rc-hniC'iziM -." --"' t.6.,,...,., --- -, , .. , ~ :net f ~ ' "'**~ ... ---~- - -oB>.... ?Jre-..-atr r r - -- ttrs e.0.1,r.,m,, mt- mn. t*-'-5- -:: . . . . . , - :la~ -- sr~ t -~ LL'.\"G (A.\"CJ:R IX ASBESTOS .\11.\TRS death certificate it was not mentioned, may haYe been missed. The import of this 16o/c is enhanced by the simultaneous statement that the incidl.'.nce of lung cancer in autopsies of the general population is only 1%;. The danger of attempting to compare a rate found in 344 cases with the rate for the general population without respect to age, occupation, and many other Yariables, such as smoking habits, is obYious. Lynch,'Q \\"ho with Smith 08 had reported the first case in 1935, reported 4 cases of carcinoma of the lung in a series of 49 autopsies on workers in an asbestos manufacturing plant who were shown to ha,e "demonstrable deposits of asbestos in the lungs." This, of course. is not necessarily identical with the disease asbestosis. Lynch, himself, points out that. although this !s an incidence of 8.21(, "both figures are too small for Yery serious statistical types of calculation." ;\ewrtheless. later writers haYe used this paper to strengthen the case for an association of carcinoma of the lung ,,-ith asbestosis. It is also of interest that Klotz 03 found only the same number of :ases of lung cancer :n a ;.eries near!:: 10 times as large, i. e.. -t in 478 cases of asbestosis. Behrens, as cited by ~Ierewether. 76 estimated that, of 309 cases of asbestosis in the literature, 44 showed associated cancer of th~ lung-giYing an incidence of 14.2%. This is an illustration of generalizing an incidence obtained in a group of cases which were undoubtedly reported only because some of them sho\\ed lung cancer, to possibly hundreds of asbestotics whose cases were ne\'er reported. The same applies to the conclusion of Teleky,85 who appears to haYe re\iewed reports of 39 autopsies on persons with asbestosis among which 6 cases of lung cancer occurred. In- formation from sources such as these does not justify generalizations with regard to mortality_ rates. Perhaps no one has \\ritten so extensiyeJy on the subject as has Hueper."2"9 In 1955 he reyiewed the cases 58 reported Brau11-Trna11 prior to that date and enumerated a total of 99. EleYen of these were those discussed by Doll 28 and may have been cases coYered by other authors. Eight were disco\ered by Kennaway and Kennaway 62 in an analysis of death certificates, and, unless Merewether's study was incomplete, these cases should ha\e been included in his re- port. Of the remaining 80, it is quite pos- sible that the 31 contributed by l\!erewether and the 17 by Gloyne contain some duplication \\ith each other or with those of other English authors. Principles of the Epidemiological Method Dorn 30 has pointed out that much of what is now tho~ght to be pertinent concerning the comparati\'e frequency of lung cancer in different population groups has been de,eloped from the analysis of clinical material, particularly surgical and autopsy records, supplemented to some extent by the reported impressions of \'arious clinicians based upon their personal observations. l\fore recently, hO\'vever, attention has turned to the systematic imestigation of this problem by the same methods that haYe proYed so successful previously in the study of communicable diseases, that is to say, by epidemiological methods. In order to apply this method of investigation to the problem under discussion, we were of the opinion that a study should be planned so as to provide ( 1) a well-defined population group; (2) a\'ailable data for all members of this population, including the healthy as well as the ill; (3) a sample which is truly representative of the population; (4) reliable and valid obserntions relating to the problem of the study. A serious defect, common to most of the studies which ha,e been reported, is that little or no information concerning the healthy people in the group seems to have been available to the author. In order to draw a generalization regarding all asbestos workers it is necessan clude li~ing persons ;s for a study well as the to indead. 63i ;, total , ,,.c: llis- <.:11 ca~es :ere Jis\.~i.y t>:.? in d. unless te. these l his reuite pos. re\\ether Juplica- oi other ogical h of what oncernmg .1g cancer been denical ma- autopsy -.:xtent by 1CJUS c\ini; obserYa- attention i mestigae methods e\iously in ses, that is ::h. o i inYesti:ussion, we should be \ell-defined data for all eluding the J a sample the populaJbservations tudy. most of the ted, is that ~erning the .ms to have In order to all asbestos ~tudy to in" the dead. 63i 0 : . 0000 : :.:-;_:::.:.:::::::. ::. ::: :. : : ::.. : . : ::.::....:..:.:..: ::H :....:.::.....:._::.:..:.:...::.:::~ o o o 0 .. --------------------- ---- .... -- A M. A. ARCHITT.5 OF 1.\'m:sTRl...JL HJ:ALTlI Limiting the inYestigation to cases coming to autopsy, as has been frequently clone in earlier studies, still further restricts its use in generalization. The problem with which \re are concerned is whether asbestos miners experience more lung cancer than does 'the general population. The answer necessitates the collection of reliable in formation on asbestos miners as a group. as \\'ell as on the general population. It seems ad\'isable to discuss the differences between the epidemiological approach and that used in the studies which ha\'e been reported to date. A wry important romideration is the fact that lung cancer, in ~pi 'e of its increasing numbers. is still a di:-ea:;e of lo\\' incidence; that is. in a gi\'en J>Opubtion not many persons \\'ill contract thi~ particular disease. This fact requires tha'. large samples or groups mu,;t be studild to pro\'icle meaningful result,;. H.ecognizing the difficulty of obtaining -uch large samples, most earlier writers de,iatt:d from the epidemiological method and ,;ought to circunwent the requirement <ii ob~ening \rell persons by ( 1) comparing the r,lati<c frequency of cancer in Yari1i~i:- :;ites: ( 2) comparing the relati\'e i rLquency oi cancer in a group of hospital- il'L'd patients: ( 3) comparing the relati,e i l'L'q.uency of cancer in a group of cases <' 1;111ng to autop,;y. .\ t ll'mpting to compare t\\'O population gniup,;, looking only at the relative fre'11wncy of nmcer in \'arlous body sites, 1my re,;ult in finding a higher percentage 1rdatin frequency) in one of the groups, \1 hl'n. in fact, the mortality rate of cancer ii a particular organ is exactly the same in lioth groups. This is very clearly dem1111'trakd in the excellent article by Dorn.ao ThL mortality rate from a particular cause j, till' true measure of comparison. It i:; apparent that selected groups such .! ' ho~pitalizecl patients or autopsy cases :,.,,_,. not be in any way representati\'e of .: I.: r;.:-tr group, and that in dealing with -~1< h -amJ>lt:,;, the obsener may easily find !L >:-L c1:-e,; of a gi\'en disease than would ,,_::- be found in another group oi the same size. but representati\'e of the general population. It is true that imestigation of cases f ram such a sample can furnish infom1ation \'aluable for research. but the use of this information in drawing generalizations is necessarily restricted. It is the obligation of both the inw;;tigator and of those who read his report to make proper comparisons an<l to dra\\' only those conclusions which are \'ali<l and justified. .-.\ good statistical ,;tucly of ca~es of cancer of the lung occur ring in a group of autopsies can lead .to a proper inference concerning the frequency of lung canct:r among cases coming to autOlb)'. but only to stKh cases. For in formation from such a study to be projected t;J some larger group. it is necessary that the autopsies represeiit a. good sample of that larger group. 'To assume that such i,; the case in any particular series is dangerous and likely to ~e false. There is some danger that the figure~ reported by some author~ may be misconstrued as applying to asbes:os \\'orkers or e\en asbestos miners. \\'hen. in fact. t~i': authors in question cl0 not make this generalization, nor can the generalization be maC:e :or the 1easons stat~d. Close stud) 0: the reports re\'eals that the percentages cited relate only to the group of autopsies CO\'ered by the particular in\'estigation. The present study. in contrast to the earlier works. has been planned to utilize the epidemiological method. :\ \\'ell-defined group of asbestos miners has been established in such a way that it constitutes a good sample of the \Yhole population of asbestos miners in Quebec. Data for all members of this group haYe been collected and analyzed. Those concerning lung cancer ha\'e receiwd most careful consideration. Details of the methods employed will be set forth later. but the type of approach is considered to permit of fair comparisons !lnd Y<ilid generalizations. Collection and Analysis of Data A preliminary sur\'ey of poential sources of information in February. 1956, inYohecl l'vl Ji. June. 1958 LL'.\'G CA.\TER IX ASBESTOS MIXERS discussions with the physicians in charge of the asbestos companies' programs and with clinicians, pathologists, representatiYes of City and ProYincial health departments and of the Canadian Canct:r Society, and other interested persons. It was found that morbidity data, although somewhat limited, were a,ailable from such sources as the hospitals in ::\1ontreal and Quebec City, and the 13 cancer detection centers in the ProYin~e. Howen~r. becau:;e of the high mortality in hmg cancer, it seemed aci,isable to depend upon data relating to deaths. These we found to be obtainable at the Yitai statistics department of the ).finistry of Health in Quebec City. From the preliminary surYey. it was apparent that extensiYe and detailed infonrntion could be gathered with respect to both the ]Jersons employed in the asbestos mining industry and the mortality figures for the general population. Following this exploratory surYey, the initial effort was directed to the collection of data relating to all workers who had been processed through the clinic at Thetford }\fines since its inception in 1947, and similar information regarding all \rorkers at Asbestos, Que. Data from the clinical records included the age, family and personal medical histories, smoking habits, number of years of exposure, an estimate of weighted exposure, and the course of the individual's health status or the cause of his death. From this infonnation it was possible to formulate a "cohort" which could be well defined, should be representathe of the whole group, and could be followed for a definite period of time. All of the aYailable experience indicates that the deYelopment of asbestosis in less than fiye years of exposure must be somewhat rare. Accordingly, the cohort v.:as defined as including every miner who had a total exposure of fi,e or more years, and who was on the employment rolls in 1950. Office and other nonexposed personnel, regardless of length of employment, were not included. This Bra1m-Tnwn cohort was then followed by means of the annual physical examination record, through a six-year interYal, 1950 through 1955. All data regarding this group werl' then tabulated in order to determine the characteristics of the cohort. For those wh0 survived the entire period, reference wa~ made to the physical examination result; and x-ray findings at the end of the period. Those \vho had died were tabulated sepa rately, and the cause of death wacorroborated by examination of the ch:;,1 h certificates. ..\ further search was mad, concerning those in the original cohort "Ji,. remained unaccounted for when the Ji, ing and the knmrn dead had been tabulatt"d They represent men who had left emplo_1 ment thr(lugh retirement or resignation Ewntually. all but a small number of thet were accounted for as either living or dead and in the latter event. the cause of d1.:;11l was substantiated in a similar manner, a11' the results added to the original list .,: deaths. Death certificates for the ProYince ,,, Quebec for the years 1952 to 1955, inclu siYe. were reYiewed in the depc>rtment ,,f Yitai statistics of the ProYincial Healch >.1inistry, together with statistical ~um maries of the causes of deaths in the I'rO\ ince by counties. All cases in which death was certified as ha\'ing been due to pri mary cancer of the lung were examined for such infom1ation as place of residence. occupation, date of death, hospital in which death occurred, and whether or not an autop!'y was performed. Cases in which lung cancer ,,as giYen as a cause of death. but in which it was not specified as to whether the cancer originated in the lung. were also reYiewed in an effort to incluck all instances of primary carcinoma of thr lung in the study. The statistics for the Pro...-ince of Quebec relate to population, total deaths from ali causes, total deaths from cancer of all type::. and deaths from lung cancer. These werl collected and tabulated by counties and by sex for the years 1950 to 1955, inclu~iH-. -i l A M . .4 . .-JRCHffES OF IYDL'STRIAL HE.-ILTH From them, death rates for the general population of Quebec and of indi\'idual counties were calculated for specific years and analyzed by cause. In addition to this analysis of deaths oc- curring in the cohort and during the years under obser\'ation. eYery known death from cancer of the lung. as well as eYery case Practically all employees of one company diagnosed but still Jiying, has been tabulated are coYered by a group policy of life insur- and analyzed. They will be discussed separ- ance which, fortunately, nearly all of them ately from those included in the population continue to carrI when they retire. A \'ery and time-interYal under study. - few are not coYered by this policy, and A comparison of lung cancer mortality those who leave the industry for one reason in the asbestos-producing counties has been or another except retirement usually are made with that in counties \\'hich are far nsmo alllonnguemrbecro.veAresd,anbuadt dtihtiiosnails clhikecekwiuspeona wrehmicohv,edprefsruommabtlhye, naosbaessbtoesstoms imneisnearsndliYien. ... the in formation obtained from the clinical Finally, in order to broaden the comparirecords on this group, the records of the son of death rates in different population liie insurance company \rere examined for groups, the rates ha,e been collected for all death claims paid under the policy, and Canada generally, and for the cnited States, particular notice \\'as taken of the claims according to the most recent published and in \\'hich the proof of death was based on unpublished material. cancer of the lung. Deaths from lung cancer among asbestos miners were thus determined from the clinical records in the medical ser\'ice of the industry and checked by means of the death certificates and insurance company records. The deaths were then ,erified individually by re\iewing them \\'ith the physicians in charge of the medical senices. In this manner. there was established a list of cases in ,,hich primary cancer of the lung is con- sidered to have been prowd as the cause of death. A few cases in which lung cancer is strongly suspected but not proved as the cause of death \\'ere considered separately. :'.\Iortality rates haY~ been calculated using both the "proved" and the total of "proved" and "suspected" cases during the years under obserntion. Comparisons were then made between the death rates from the same cause among specific segments of unexposed persons. All lung cancer deaths, both suspected and proYed, were carefully ana- lyzed to determine possible relationship or correlations between the development of lung cancer and any factor known from the clinical records, such as family history of ':ancer. personal history of heavy smoking, rnexistence of asbestosis, or exposure to a~bestos. Results and Interpretation The cohort \\'hich \\'a~ constructed according to the criteria described in the, preceding section has been considered indi\'i<lually and compared with the general population. Description of the cohort "ill be presented here as a preface to the results of the study: Original Cohort Lost Perons Deducted Fmal Cohort Living m 1~55 (\\OrAing and reuredJ Dead by 1955 Cancer of lung Questionable cancer of lung Other causes Vnknown cau~es Smokers :\'on smokers l"nknown 6,091 133 ~.958 3,ii l JSi' 9 3 169 6 4,673 1,265 20 Tables I, 2, 3, and 4 present age, number of years of employment, weighted awrage exposure, and smoking habits of the cohort. A comparison of the exposure to asbestos dust is presented in Table 3. All members of the cohort were placed in one of three categories, representing increasing degrees of exposure based on a \\'eighted aYerage of the years spent at Yarious JeyeJs of du?tiness. The degree of dustiness for each job category was determined after consultation with persons familiar with the emironment and conditions in the yarious work Vol. Ji, Jrmr, 1958 .~. -1 .-'. ::_. :__:; l -~,:;,--__--; ~ .. ' -.~:::.: "' __:.,.....::.. j .., ~' ~-....... ~ ~~ .- ~~..:.~;] - . .. - -.--- - -~-'.<: -~ . -- 4-' _, ~. f.< . . . ~.' ... ... ~ .. ,_ ;.._ ~?:~.--~ ~;>:'.~ . 1 ~ ~ ~~~:~;'.:.-:. j - f.CXG C.1.\"CLR IX .4.SBESTOS .111.\"ERS T.\R:.1: l -.\"11111btr and Pcrct11f,1q, fi1strz/J11tio11 b)' Age T.\l\LE 2 -Xw11btr 1111d P.-rccntayc Distnbutir"' I> Lcnylh of l.11Jf'loy11Jcnf .\ ~ l' 2U-~L ____ _ 4fl-M ....... . :-..:..-1 1_ . . - . - . 11."i-r ------------ ----------l"lH~llOWn __ .. __ . __ . _....... _. ---- .. Tot~!~---- .\H:~~l' .\g( .......... --- Lts.' tlian 0.53. 5.~'4.i1' i I l'rr Cent fl6 19 JO b 100 L<11~th of f.mplo:mcnt ti-l ... - - .. - .. - - - ......... - . - ... - . J0-19 . . . . . . . . . . . . . . ---- 20-!?!:f.. --- ------ ... - ... - - ... -30-39... - -. - 40-49............... -........... . 5ll+ .....: ....................... . Tntal>..................... . AYl'f:l)!(' yC'ar~ of t1Tilp1ormrnt .. --- . Xurnber 1,795 2.398 922 603 185 55 5.958 18 r~r Cent 30 40 16 10 3 l J(l{J ;trea~. For the purposes of calculation, the :is.;urnptiun has been made that the relation.;Jiip bet\\'een these categorie,: i~ linear, and that Category Jl is twict a~ dusty, and Category 1I I three time~ as dusty as Categ-nn I. ually smoking more than fi\'e cigarette~ ]''r clay. Persons "ho smoke pipes or cigarexclusi\'eh \\'ere not considered to be ~111r1h ers for the purpose oi this study. Table 5 presents the year-by-year n;perience of the cohort and indicates thl.' T.\llLE 3.-.\"umbcr and Prrcr11/,1qc Tlisfribution by Exposure Calt'[i"l'Y F. \t1o~ure C~1t<'P:ory L _____ --------------- ]! ______________ ----- -- . - . - ... --Ill_ --- ___ . _. _____ . _. ___ .... _..... _ l"nknown......................... . Totals...................... .\'C':-.1~e E\po~nre___________ :'."\ un:licr .Col 2 J.=i11 l --1 : ~..1r1"' :.?.fl Per Cent 34 36 30 100 Le~~ thon 0.5%. 'n-1e fourth Yariaule, smoking habits, was ,:imilarly tabulated and is ~hmm in Table -+. This \\as included becau~e the informa- tion ,,as a\'ailable and because :<moking \\'as regarded as one of the \'ariables which. besides the ernironment, could conceiYably influence the de\'elopment of lung cancer. A.s used in this presentation. the term smoker refers to a cigarette smoker, habit- T.\JlLE 4.-Xw11t-<r and Pc1cenlagc Dislribuliui: by Smoking Habits ~m(km~ Jfohns '.\:umber .~mokers................... ~on~moker!'.' _____ ._. _. _. _. _______ ___ l"nknown.......... ...... .... .... .. 4.673 1,265 20 Tot3ls..... -_ 5.958 100 Less than 0.5%. numLer of deaths eacl1 :eai from s;Jec fi,d causes. In general. a case was comidcn:d to be "proYed" a:-; one of primary canl'lr of the lung \\hen the records showed tha: the diagnosis had been supported by an autopsy or surgical resection of the ltmg with microscopic examination of the rl.' 1110\'ed tissue. In one case so comiclerccl. howeYer, diagnosis \\as confim1ed by bron TABLE 5.-Ycar-by-l"car E.ipcricnce of Cohort and Death Rates per 100_,000 Man-}"rars of Risk Cause of Death Year ~o.Ali..-e At Beiinning of Year Pro.-ed Primary Ca.or Lung Suspected Priman Ca.of Lung 19!i0 . . . . . . . . . . . . . 5,958 l 2 1951 ... 5.942 2 0 195:? ____ .......... - ........... . 5.922 0 0 1953 ___________________ _ s.B~ 2 l 195-1 5,S4S l 0 1955 5,810 3 0 Totals............................ 9 "Fro,ed" rate per 10' 0,000 man-years of r:sk- 9 ~ - 25.5 Other Causes 12 17 37 3-1 33 36 Jfi9 'Tr.tal" rate per JC0.000 man-years of nsk~ 3:._ 2~;.5 - 34 O t;nknown l 1 0 0 4 0 6 )!an-Yea~ of RISk 5,950 5,932 5,903.5 5.~.5 5.SZll s.90~ Braun-Truan ..... __::..::=.::::::::::::.:::::::.:.::..::::::::":::~:::=::::..:.::..'..::.-_:::..:.:.:.::::----:---------..:::.:.:.:. _______;..:::.:~:.:...:.:.:....--- r lt: ., "'lJl' A. JI. A .-1.RCHffES OF !:\'DUSTRIAL HE.-1.LTH TABLE 6.-"Pro-.:ed" Cases of Pn'.mar:y Ca11ce1 of the L11ng Case :So. AGe l 00 2 65 3 1\5 4 5g 5 48 6 61 7 Mi 8 3i g 68 Smoker Yes Yes Yes Yes Yes Yes Yes Yes Yes Exposure 26 yr. in Cat. II 34 yr. In Cat. I 3i yr. in Cat. l 32 yr. in Cat. I 22 yr. in Cat. 11 33 yr. In Cat. Ill 30 )T. In Cat. 11 16 )T. In Cat. I 28 )T. in Cat. III Died Hl-12-51 5- 3-55 i-20-55 8-20--50 -51 4-30-53 11-22-53 8- 5-M 5- -55 Autopsy Yes Yes ::-=o Ye.s Yes Yes Yes Yes Bronch. Asbestosis Yes ::-=o ::-=o Xo Yes Yes Yes );o );o choscopy with visualization and biopsy. In another, although there was no autopsy, the diagnosis of primary cancer of the lung seems to have been beyond question. The term "suspected" primary cancer of the lung was applied to those cases in which the diagnosis remains in doubt but some of the eYidence points to cancer of the lung. There were three such cases. The term "man-years of risk" has been used to mean the number of men at risk ior the year under obserYation. A person who lived throughout the year was counted as a full man-year of risk, but one who died <luring the year was counted as one-half a man-year. Deaths occurring in the cohort, and in \\hich Jung cancer is considered to haYe been pro\'ed as a cause, are shown in Table 6. In Table 7 are shown three deaths which ha\e been considered as "suspected" lung cancer cases. An indication of the importance of these "suspected" cases in interpreting the results of the calculations is desirable before further discussion of the mortality rates which are derived in later tables. For example, it happens that the rate found for the proYed cases is close to the "expected" rate based on the general population figures for the ProYince, as will be shown later, and on this basis we should find eight deaths from lung cancer among the cohort. Actually, nine cases were observed. If, howeyer, the 3 additional "suspected" cases were in eluded. increasing this figure to 12, the total would be very close to the 95<jc level of significance. HoweYer, haYing found just 12 cases, we are not aboYe this le\'d, and therefore the hypothesis that asbestos miners do not have a higher mortality from lung cancer than does the general population cannot be rejected. ::\e\'ertheless. the occurrence of 12 cases in this samr1le would increase the rate to a point \\~1ich approaches the significant bel. Because oi the tremendous importance of the questionable cases in this re$pect. some detail regarding them will be gi\'en here. In one of these cases, the su~111c1011 of cancer of the lung is based upon the x-ray interpretation, and. although no autopsy was performed, the death certificate indicates that death wa~ 8ue to lung cc.ncer. J, is well known that the x-ray appearance of fibrosis, especially if a localized density or a superimposed tuberculous lesion is present, can simulate that of a tumor, and by itself, does not jmtiiy the inclusion of this case as one of "proYed" cancer of the lung. A second case was certified as ha\'ing died by reason of hydrothorax, possibly due to lung cancer, but again there was no surgery and no postmortem examination. In the third case, although it was subjected to autopsy, two pathologists disagreed as to whether lung cancer was present. The death was certified as haYing been due to chronic myocarditis with nephritis and pulmonary congestion, and possibly cancer of the lung. On the basis of these fact::, it :-eems unwarranted to include these three cases among TABLE 7.-"Suspecied" Primars Cancer of the Lung C":i!'e ~o. Age I 4g 2 46 3 65 Smoker Yes Yes y~ Exposure 32 )T. In Cat. III 33 lT. In Cat. III 42 yT. in Cat. II Died 10-25-W ;- -53 !t-30-55 Autop;r ::-=o Yes Xo Asbestosis S'o Yes Xo - .... . -'l j ,-.j j . - . ':-. -~ ~ . __,_~.. ::,.~ :- . ~. ,.. i - ... .- '.. --.-,.~..:!.'-'.i,l .:.-..---::~ ;~.-..._. .. --.. --; .. J -~---": ~--J~_:..,_~:,~~ ~ _.-3-~:~:;{~~:j <:':-~'~;~:~:-;.':~~J:\;:~t~'.) .?.{,:.: ~ c - ' -: 1 :;.. :{:_:-; '.;,~ .7::~:~;::~/'~ .. ii~~~~f~t .L'.YG C...J.\'CER !.\' ASBE\'TOS JJl.\'ERS "proYecl" instances of hmg cancer. On the Jthcr hand, they cannot, in fairness, be ctisregarcled complekly. Jt i~ for this reasfll1 that mortality rates haYe been calculated both ways. Table 8 gi\es the rates by age groups. The rates by length of employment are :;hmm m Table 9. During the first 40 years of employment, the rate rises, an observation which seems plausible since the men 1\ere growing older. Howe\'er, after 40 1ears of exposure there are no "proYed" cases r<::porkcl for a total of 240 men dur ing the six years, or about 1440 man-years of exposure. \Vhen the ''suspected" cases a re added, one case does ~hm\ up in this T.-\llI.E 8.-L1111g Ca11ca D.-aths by ..Jgc Groups T ~BLE u.-Lu11q Cancer Deaths bs Length of E111f'/nymr11t :\'umber of Pers.vns a.nd ~umber of Lung Cancer l>tat:i~ Len~th <f Employment :\o. of J'ersons :'.'\o. of D<oths Proved Tot.:JI 5-9 ................ . 1.795 0 10-19................ . 2.3% I 20-29.... - - .... - 922 3 30-39.............. - f.03 5 450(1-+49. .. .. .. .. .. .. .. .. .. .. .. .......... .. l&'> 55 0 0 Totals....... . 5.%8 9 12 Annual Lun;: Cancer Death Rates per )IanYears of Exposure Length of Employment Pro,ed 5-9.............................. _. 0 10-19.............................. - ' 20-29... ------------------------ 54 30-39............................... 13~ 40-49............................... 0 50+................................ 0 Oer-311.. ...... __ ........ .. 25 100,000 T<H .I r Wl !1> (J 31 Xumher of Persons and ~umlier of Lung Cancer Death~ .\oe Group :\o. or J1trsnns :'.'\o. of Deaths Proved Total 20--14 _- - - - - -- - -- - - - - -- 3.001 I ~ -,-~)4 .. -- - - - - - - - -- --- - 1.124 1 .~.:.-ti4_ - - - - - - -- ----- -- - C.15 3 (l"i~n+k-n-o--w-n--_-_-_-_-_-_-_-_-_-_-_-_ 3153 04 Totals ....... . 5,958 12 AnnuaJ Lun~ Cancer Death Rate~ per )lan- Years oi Expo~ure .\~c '. roup l'rowd 20-44............................... 4 l5-: ................ .. .. ..... 15 -'5-64............................... bl (;5+................................ 212 l"nknown__________________________ O Owr-all.................... 25 100,000 Totzl 4 44 81 265 O 34 period. This would produce a rate of 69 per 100.000. again demonstrating the impor.tance of these questionable. but unproved, cases to the final conclusion, becaus'.:'., if there \\ere no cases in this number of men with long exposure, and if asbestos is a carcinogenic agent, it must be concluded that these 240 men ha\'e demon- :?.,;Iii~:~:?s~~o:~~~~:.:~~tF~~~~:::~ of an intrinsic or endogenous factor in cancer. The only other explanation would be that the susceptible members of this age group had died earlier of lung cancer. Table 18, ,,hich appears later in this section. in- Bra1111-Trua11 dicates that the members of the did not die i rom lung cancer at a you11;:tr age than th~ general population. The rate;: by \\'eighted exposure ;:n ~hmm in Table 10. and it will be tH 1tt .J that they present strong eYidence ag-;1:11'! asbesw:-; being a carcinogenic agent. for. ii exposure to asbestos is in any \\ay om nected to lung cancer. we would expect th:!'. the longer and heaYier the exposure. t'lw higher the rate that \YOUld be found. The only possible ~rror in this interpret;1ti"n could occur if the weighted exposures 11 L'fl imersely related to years of employnlt'lll. TABLE 10 -L1111g Cancer Deaths b) Exf'os111 Category Xumber of Per;ons and Xumber of Lung Cancer !Jeath E'fX'sure Category ~o.of Persons Ko. of De.:iths Pro,ed Tot>! ! 1.................. 2.031 4 IL................ 2.1so a III.................. 1,772 2 t:nkoowo..... ....... s o o Totals........ 5,958 9 E.,.:: Lo,,~;:.~..":t'~.~:~;, ~' Category Pro\"ed !................................ aa !!................................ 2S m................................ 19 Cnknown...... ................... O 0 ,.~Vill. _ ............... 25 12 rno,ooo riTotal 3~ tHJ ;.:.:. '-.~-- -,::.:._'{~;,~~~@i'iiil\'SU&i.nnarmacL&!tWWWWWl'WWWWZW A. JI. A. ARCHJT"ES OF J.\'JWSTRIAL 1-!EALTH T.~RLF 1l.-.\11111/1cr ,1/ Pt1sons iu / "anmts lf.-.:ghtcd E.1fo.rnrc Cottg,irics by Lcn_qth nf Emf>/ny111rnl \\'rl~hted Eq>0s11rP C.it(g:orws Len~th of -------~---- Emplorment JI III j-~ lfl-1~ 20-2'-" 10-:i~ 50+ 40-4~ 70i 5% 490 f.f>3 !'.!'3 851 314 3r,3 243 247 21!; 137 ;'6 67 41 24 21 10 l'n known n 1 2 1 1 0 Total l.i% 2,398 922 f,()3 !SS 55 T.\BLE 12.-L1111u Cancer Death fnr S11111i.'crs 011d ,\'011s11111kcrs :'\umber of Person!! and :'\umber of Lun~ Ca:iccr Dt:ath~ h:- Smoking Haha~ '."o. or Death! Persons Pro"<ed Total f'mokrrs ............ .. 4,6;'3 9 12 :'\"on~mokers. ____ ... _. _. l.205 0 0 l"nknown .......... 20 0 0 Totals...... .. o,9!>8 12 Tot31S A\"( r:i.!!e rrnrs cf ~~ptisurt: 2.031 17.8 2,1>0 17.b l,i72 !C.6 5,958 29.0 li.5 Annual Lun~ Cancer Death R!'te< .rer 100.0C: ~fan-Ycaro of f.xpo<ure hi Smoking Hahm :>:o. of neat'1~ in \\hich ca~e the hea\'iest \\eighted ex- rrowd Total f!CJ:>ure (Category I I I) would show the shortbt length of employment. Table 11, ~moker~ --------- __ _ "on!'tnnkrr~------ ____ _ l'nknown ... _______ ... 32 43 0 0 0 ~ l which li:'ts the number of persom in \arious Over-all ......... - .. -- ..... - 34 A expo3ure categories by length of employ- ' ment indicates that thi.~ error has not oc- smokers ma\' haw included a larger curred. I 11 fact, the aYerage number of years perccn.age of .young men. Consecpently. ad- of employment for each exposure l'ategory ditional Tables. 13, 14, and 15 .,\ere con- is almo:'t identical. structed to show the di$tribution \ i :::mokers Table 12. which deYelops the rates for and non~mokers by age. length of employ- :-rnnktr:' and nonsmokers, is mo5t striking. ment. and degree of exposure. ..\!though lt shm\'s that not a single ca3e of lung there are ~light differences, thty <lo not cancer dneloped among the 1265 non- account for the fact that all obsc-:Ted cases s1,1oker~ and that all cases of lung cancer, of lung cancer \\ere in smokers. In respect both "proYed" and "~uspected," ocrnrred in to age (Table 13) the combined awrage smokers. age of the smokers was 4.9 year:: le,-;s than Table 12 was so striking that it was felt that of the nommokers. Table 14 shows th?t funrwr verification was necessary. It that 'lS far as length of employn:ent is con- \\as possible that some abnormal distribu- tion may haw occurred. e. g., the non- T.\BLL 13.-.\'umha and Pcrcc11fagc Dist1ih11tirm nf Smokers and l:o11s111okcrs by Age Groups .\.ge Group :n?1-15-444 . ...... ...... ......... . !\'.-fo4 tt~+-----------------rnknown ......... Totals.... ..\. "<erage a~e ...... !\'umber Smoker - ::\'onsmoker 3.200 fiSH 896 224 411 202 164 150 2 0 4.fi73 39.3 1,265 44.2 Unknown 12 4 2 1 1 20 40.7 T-\BLE 14-}\"11111/Jcr and PClrrnf,:.fJr Di.strihution of Smokers and .\"onsmnkcrs by Lri:pth of E111plny111cnl Len~th of Employment 5-9 ---------------- 10-19.............. 20-29 . . . . . . . . . . 30-39 ..... 4so0-+49....................... Totals........ A Yera2e len11th of emplo)-ment .. :"umber ~mokrrs 1,408 J,P6;' ;22 433 110 33 ="onsmoke~ 3,-,- 426 199 lf\fi 75 22 4.673 1.265 17.0 19.3 C-nkno..-n 10 ~ 2 ~ 0 0 20 16.0 ( Perremage Distribution Percentage Distribution -~~e Group I !.':.-+!................. ;;...:.4........ ......... :.;..~----- t~:k-rlO\\:~~=~==~=:=~== Total>. ...... Smoker 1\8.5 19.2 8.8 35 100% Xonsmoker 54.5 li .i 16.0 11.8 0.0 100% rnknown 60.0 20.0 10.0 5.0 5.0 100% Len~th Of Employ'!Ilent 5-9 10-19.... 20-29 ....... 30-39............. 4so0-+49................... Smoker 30.l 42.l 15.4 9.3 2.~ 0.7 Xonsmok<r 29.8 33.i 15.7 13.l .~.9 l.S C'nl:Do...-n ro.o :?0.0 10.0 '.!0.0 o.o 0.0 Totals... 1003 lOOo/c 100'7. T"of. I~, .T 1111r. 1958 ----- - -- --- - - - - - - - - -... ........ .ir..-..&.--- ........ - .... IXSG CA.\"CER 1.1\ ASBESTOS Jf!SERS TABLE lS.-.\'11111/Jcr and Percentage Distribution of Sn111kcrs and ]\'onsmokcrs bi' . E.rposure Catcgorj' Exposure Category L ................. IL ................. III .................. 'Cnknown.... __ ... _. Totals........ A,era~e exposure cate~or)' .. _....... :\'umber Smokers :\'onsmokers l,f>.'\3 474 l,fi91 452 1.425 338 4 1 4,6i3 1,265 2.0 1.9 'Cnknown 4 7 Q 0 20 2.3 Demography in the PrO\incial n!inistry of Health. The data on total deaths, deaths from all forms of cancer, and deaths from cancer of the lung were obtained by sex ~nd by county for the years 1950 through 1955. In addition, all death certificates which ~.pecified primary cancer of the lung, and all those which indicated lung cancer but did not specify the origin, were examined for the years 1952 through 1955. Prrrentagc Distrihution Table 16 gi\es a tabulation of the number Exposure of deaths from lung cancer in the PrO\ince :,i.-... . Cate~ory Smokers Xonsmokers l;nknown and in the cohort for the years 1950 through -;j: L.. .... 33.2 IL....... ......... 31\.2 3i.5 35.7 20.0 35.0 1955, .i.nd shO\\s the annual rate per 100,oor1 llJ .... ... .. . . . . ... 30.~ Cnknown.. .. . u.l 21\.7 0.1 45.0 0.0 in these segments. It will be noted from the Totals........ 1(~13 HKl% 100% table that the mortality rate for the "proved" cases in the cohort is only slightly cerned, the smokers had worked about 2.3 higher than the rate for the Prmince. years less on the average than the non- \Vhen the "suspected" cases are included in . ' smokers. \Vith longer exposure and greater the calculation, the hte for the cohort rise~ age, one "ould expect the nonsmoking to 33.8 per 100,000, which is about 50~( group to show a higher rate if lung cancer higher than the rate for the ProYince. Thi~. were due to asbestos. Table 15 shO\\'S that it will be recalled from the predous dis the anrage exposure category was almost cussion of the effect of the "suspected" the same for the two groups. Therefore, cases on the re~ults. approaches but doe~ this nriable seems to be of no importance not exceed the significant leYel. in accounting for this difference. One further interesting obsenation from The result of this additional analysis is that none of these factors appears to lessen the effect of Table 12. Table 16 is the rather marked increase in the total number of ca~~s fo1 the Prmi1,ct between 1950 and 1955. It is assumed that C0111 parison of the Coltort Ex pericncc at least part of this increase is due to im- with that of the Province of Q11ebcc, Do- proved recognition and reporting of lung 111inio~1 of Canada, and the United States.- cancer during the intenal. F01; this reason. In order to make a comparison of the the years 19S4 and 195~ were thought to be experience among asbestos miners with that more nearly representatiYe of actual condi- of the general population of the Province of tions. yen so, it is quite likely that the Quebec, statistics were gathered, as stated general population is not studied for lung earlier, in the office of the DiYision of cancer with the same diligence with which .-~ .: ~" i i TABLE 16.-Comparison of Cohort with Province of Quebec Lung Caneer Deatbs ."-nnual Number of Rate per Persons 1950 1951 1952 1Q53 1954 19~ Total 100,000 Pro\'lnee 1,198.000. 196 220 245 303 303 357 l,62i :?2.6 Cohort 5,923 t Tota.I 3 2 0 3 I 3 12 33.S Pro\'&d 1 2 0 2 1 3 9 ~.3 Province 1,102.000 103 21S 245 aoo 302 3M 1.612 Z!.5 (ercludlng asbestos work en;) In the Pro\'ince figures, It has been assumed all male lung cancer deaths are for men o! 20+ ,ears. Approximate midpoint of the enumerated population for 1951, and the estimated population !or 1954 (Rapport, rn..-. de la Dt mo~raphle). tSumber ah.-e in cohort at beginning of 1952. Braun-Truan ~5 ...... .. .. ..... . ..... .. ... ...... :::.::.:.:::. :..:: .-:-.: . . ....... I Total~ A. JI. A. ARO/ll"ES OF IXIJL'STR!.-1L HEALTH T \Bl.I-: 1i.-L1111u Cancer D1a/hs for the P1-.>111cc (!f Q11cbcc * F.st 1m:.i <'<l t ]'OJ>ll).ltl'ltl 777 ,fl()(l !!tr.2.0tMI 137.00(l 121,CK~I l.237,IKIO Total 17 fi7 J(XJ Ill 2<.J5 :\umber oi Deaths 19M Fpcc1tied l'nmarr I'rowd Total l'ro\'ed 13 11 9 afi 43 29 38 69 32 33 68 :?\< 120 191 w 195.) Tot.al Certified ~p!'c1tied Primary Total li fiO 117 148 342 Proved 9 35 S7 54 155 Total 17 56 116 148 337 Prowd g 32 57 M n2 20-H .. 4.o-.'L __ _ ..1- .~ - - . ' - t~~-:- - - - . Death Rates per I00,000 11,;4 Tot.,] C'irc1fi"'1 Total 111.1\'("j Tot.al Pr\('(} 2.2 1.7 1.4 1.2 ;,rn:.? 17.~ 21.3 14.4 73.C\ 27.7 .'\0.4 2:14 91.7 27.3 51\.2 ~LO 23.~ 9.7 15.4 ~.o - - - - - - - - - - Tot.al C<'rllfie.d 19.'' i'~"'ctfd Primary Total l'ro\'ed Totsl Pro~ed 2.2 1.2 2.2 1.2 29.i I i.3 27.7 !o.8 S5.4 41 n .. 4.7 41.6 122.3 H.n 122.3 .6 27.6 12.5 27.2 12.3 . n.n. f1 :: <il.th (0t'::1.it-::t" '1' f..S.!1~11 lit 1r J q1.1l 1\ I 1 l 111 11 \(' l liy :l;l;Jlym'! rn,1 p:n;tn:a7rS for .l'Z(" ~r,,u 1 ,s f 1r rn i}es to the t );J} p1p'J:.H1J'1 fo:- }';}j~, as e::i~eD l'l l-~.1.111,.;rt. l>!Y dt' I. l>lrno:;r::pLll'. :his di:-t:::-e is looked for in the miners. and Thi~ cumparison, summarized in 'Table it ;:e1:m:' prnba bk that the mortality rates 18, shm,s that the obsened number of ' f ior the I'nJ\ince may be 10\\'. This \\ould deaths in our sample is not significantly -~ :ippear tl be substantiated by the fact that greater th;rn the expected number of deaths, the repr.:-ting of case;: in the cohort shO\\'t'd based on the awrage of tht 195-t and 1955 !~ no such inaease on.T the same period. figure~ for the ProYince. It is true that. in Table 17 \\'a:' compiled to shO\\' the an- the ca'e of the age group of 65 and o\er, nual age-,:.11ecific lung cancer rate of cases the fi\e deaths prO\ide a figure which is in \\'hi(h he dc<i'11 certificae merely read a1most significant at th,. 95<;;;. Jew!. H0w- "cancer of the lung." as distinguished from those in \Yhich the diagnosis was confirmed by autr1risy. surgery. or biopsy. The term ~pecifier! primary" refers to those cases in these rno categories in which the tumor \\'as specified as ha\'ing originated in the lung. It \\'ill be noted that, of the total cases reported in 1955, a much higher percentage eYer, it shoukl be noted that this number includes one of the suspected but unproved cases preYiously referred to. Furthennore, it is rather likely that the rate for the general 11opulation is understakd in this age group, for the obYious reason that the exact cause of death in the Yery old is not than in 195-t were specified as primary. The table al,:.o shows that a higher percentage of the total cases certified in 1955 were prmed, agc.in indicating increasing interest TABLE 18.-Comf'arison of the Act1uiJ and , E.1pcctcd N11111ber of Lung Cancer Deaths bY Age Among Asbesios Miners _in this disease. A comparison has been made ben,een the age-specific rates shown in Table 17, and those for the cohort, shown in Table 8. An aYerage of the 1954 and 1955 rates for the Pro,ince has been used, since the 1955 figure '':as higher and may haYe been exceptional. A~e Group Pro'l'ince Total Specified Primar~ Rate per 100,000 20-44 1.S 4&-54 24.5 .15-64. 6i.6 65+ 89.3 'Cnkno"'l\ Obse!"l'ed No. Expected of Deaths ~o.of ~O. Of '.:\liners Deaths Pro..-ed Total 3.901 1.124 615 315 3 Ot 1 1 2 1 3 2 3 3 2 4 s 0 0 The npected number is baSEld on the a'l'e.ra~e of the IP54 and 1955 age-specific rates for the Pro~ince. of Quebec. t Actullly 0.4. T"ti/. Ii, .f1111c, 1958 ) { . J :~ . ::.::::::..:: :.. :..:.: ::. : : ..::..::::::::::::::::::.:.:.:.:..:.::::::::::.:.:..::.:::..:::_.:...-_..:_.:.:.::::..:-..:.: :.: : . ::::.. :::::::::::. : .. : ..... . . ..... ................ .... : .:...:.:::::_;_:_:..:.::.._..:.~.:__:::_:.::...:..:::.::...::......................- ........ LL"XG CAXCER fl\" ASBESTOS JfIXERS * TABLE 19.-Agc f)istrib11tiu11 of ,ld11/t Males for tlzc Proiincc of QuchN, 1951 A~e Group 2044 ............ 45-M .... ~65-+-.............. Total.. .. l 1ro\mct :'.'\umber l'lrtrntap:e i2i,135 f\3 li.;i;.~:;2 16 l'.ll>,\144 11 113,467 10 l,158,498 100 Perrenta;?e 111 Cohort f\6 19 10 5 100 Rapport, 1954. a matter of the same intensity of interest as it is in younger ptr~ons. Table 18 abo ans\rers a question previously rai:;l'(I. It ~hfJ\r!> that the member~ of the cohort han: not died from lung cancer at an age earlier than the general population. and that such an explanation cannot be offtn:d for the ab~tnce oi lung cancer in 240 men \\"ith more than 40 years oi employment referred to on page 643. Before Jea\'ing this comparison of the PrO\ince with the miners, it should be sho\\"n that their age di~tribution:- are n:asonably the same. That this i~ the case can be obstrved from Table 19. It should be remembered that the miners retire and consequently. it can be expected that the oldest age group \\"ill be larger in the gtneral population. The data presented in Table 20 indicatt> that the lung cancer rate generally dtcreasts after age 70. Therefore. we could expect the rate for all people oYer 65 to be smaller than the rate for the group between 65 and 75, \\"hich would apply to the oldest group of miners. It is felt that by using the whole adult male population, we ha\'e developed rates for the general population which are somewhat lower than if we had been able to exclude the people in the general population OYer 75. A comparison between the asbestos miners and the population of the Dominion as a whole was made, using statistical material from se,:eral sources. In one source, Phillips 79 ga\'e age- and sex-specific rates for Canada for three periods between 1931 and 1952. The rates for males are gi,en in Table 20. These figures show strikingly the increase in rates between 1931 and 1952. and this Braun-Truan TABLE 20.-.41111110/ Death Rates per 100,000 f<" Cancer of the L11ng in Canada* .-'.ge Group rnder 30 3a.0,-..3349 40-44 45-49 .'iOM 5,,.59 f\()-1\4 fi.'i-<19 IO-i4 7~-;g ~CHI ~:;+ All Mes 1931-1933 0.2 0.9 2.0 3.0 5.2 ~-2 12.7 12.5 1.).1 10.i 1-'.8 8.2 11.4 2.8 Groups of Ycnrs 1141-1913 0.3 0.9 3.2 5.4 12.5 18.9 27.0 33.7 34.5 30.6 30.0 27.9 14.3 7.1 195()-1952 1.0 0.8 3.0 6.5 10.7 37.2 59.7 77.8 102.9 AA.3 &3.9 59.7 71.0 15.& "'.\fortallty from Lun~ Caneer in Canada," 1931 to 1952. increase is particularly marked after age 50. confirming an obser\'ation pre\iou~ly made. to the effect that until recently lung cancer has probably been underdiagnosed in the older age groups in the general population. To m~ these figures for purposes oi comparison. it is necessary to combine the ratts for certain age groups in order tti conform to the age distributions ustd in thi~ study. Since the exact populations in each age group for the years indicated is not kno\\'n, this must be an approximation. Ho\\'eYer. the rates would be somewhat a~ folio\,-~: A;:e Group 20~~ 45._:..;. 55-64 65+ Rate s 27 69 9095 These rates are. in general, lowtr than those deYeloped for the total (proYed and suspected :1 cases of lung cancer among the asbestos miners. The only large difference. howe\'er, is in the age group of 65 years and oYer. and it is quite possible that the rate for this group may have increased for Canada between 1952 and 1954 a.s it did for the ProYince of Quebec (Table 17). A further comparison has been made with an O\'er-aJI rate obtained from the American Cancer Society for respiratory cancer deaths in Canada in 1953. This rate, for males. is 20.8 per 100,000, or 5 more per 100,000 than Phillips' 1950-1952 rate, and compares with 25.3 per 100,000 for proYed cases and 33.8 per 100,000 for total cases among the (Hi "nOHo.. O o--.....:..- 00 - . ; ; . - ~--- ___ --~ '_}-- --"''_._,,_.,.........._ ' . ........~--""---. A. M. A. ARCHJJ'E\ OF J.Hll'STRIAL HL4LTH T:\BLE 21.-.\"11111bcr (Ji Deaths and Death Rates f'cr J(!0,000 by Age Groups i or the Adult .\Jal" Pop11!ation (Ji the United States* waY, and other countries. at least 50.000 pe;sons must be exposed throughout t~e world. and it can be assumed that this .1.~e Group Popul.nwn Cases Rate per 100,000 number has been fairly constant in the 20 :..'l>-44 4;~M 5.'-&I ti..:...+ Total 24/>H,OOO ~.OGJ,000 ti.~HU,lKlU ~.tiiU,\)()() H.lil9,00U 883 2,9i9 ~.:.!..">! 6,4!!:l 16,5911 3 6 36.9 98.6 114.3 3i.2 years since 1935 \\hen the first case of asbestosis "ith Jung cancer was report1:<1. At least 1.000,000 man-years oi exposure has thus bl.'en accumulated. and this figure Datu from "Yitai Sta!lstics of the l:nlted States," Vol. l and 2, 1952. asbestos miners in this study. It is therefore obYious that there a re no important diffen:nces bet\\"een the rates for asbestos :niners an<l those for the general population oi Qut"bec and the Dominion of Canada. Si1Ke it is probable that figures for the l"nited States are more complete and, therefore. possibly more comparable to the data for th\:' miners, age-specific rates were com- puted from "\'ital Statistics of the tnited States." Yolumes I and II, for 1952. These rates h~iw beei1 tabulated in Table 21. It is apparent that these rates compare iaYorably with those for the asbestos miners a5- shO\rn in Table 8. Still other rates for the l-nited States were obtained from the :\rnerican Cancer Society, and for males. these \\ere 25.3 per 100,000 in 1953, and 28.0 per 100,000 in 1955. They are not iden~ic;.; with :he rate ca!cuh:ited fror.1 t\.ie figures oi the office of Vital Statistics, but this is possibly because the American Cancer Society rates are for males of all ages. Xen~rtheless, they, too, compare farnrably \\"ith the rates o( 25 ( 0r 34 for total cases) obtaining among the asbestos miners. Turning for a moment to a comparison l>etween the asbestos miners and persons who are exposed to asbestos. in one form or another (as <listinguished from the general population groups just discused, who ha,e t1'J exposure) an interesting obserYation can be deYeloped by deduction. Hueper .;s has stated that there are about 35,000 persons exposed in the l:nited States, and we haYe found that the Canadian mines employ about 8000. Elsewhere, it has been 1:stimated that the workers in England who haYe exposure total between 3000 and 5000. \\.ith workers in Africa, Denmark, N'or- can be diYi<led bY the approximately 150 cases of hmg c;;ncer with asbestosis reported during the 20-year period. This giYes a rate of 15 per 100.000. ,,hich is at least indicati,e that any lung cancer rate which can be calculated for workers exposed to asbestos dust is not much g:eater than that for the unexposed populat1on. Comparison Bct-.,ccn Eight Counties Adjacent to tht Asbcstos-Produci11g Areas and Eiqht Selcct,d Co1t11ties.-To compare lung ca;1cer mortality rates in the countie5 surroum\ing the a~bestos-producing area~ with another group of countie5 in which no asbestos miners are likely to reside, the. rates \\"ere computed on the basis oi figures for the years 1950 through 1955. The eight com;ties stltcted for comparison \\ere ...\rgenteuil, Chateaugay, :\fontmagny. Po~t neuf. Richlieu. RiYiere-du-Loup. :::--t. Hyacinthe. and Terrebonne, mainly because th~\" repre~ent a \\iJ~ geog1aph:c di5tributio1~ throt\O'hout the ProYince. The countie:-; selected be"'cause of their proximity to the asbestos mines include Arthabaska. Beauce. Drummond. Frontenac. ::-.Iegantic, Rich- mond. Shtrbrooke. and \Volfe. Table 22 shows the number of lung cancer deaths for the years 1950 through 1955 for each of thes; counties, and a mortality rate. based on the adult male population in 1952. To emphasize the comparison, Megantic County has been shown separately, as has the P;oyince of Quebec and also the Prmince with the eight "asbestos-producing.. counties subtracted. Decause of its unique lung cancer death rate, ::-.fontreal et Isle de Je,;u~ h::is also been listed in order to proYide further comparison. It is apparent from the table that the Jung cancer death rate for the eight counties ro1. li, June, 1958 ---- ...,~-- ~_,. ...~.............. ~ - :~~~-~. . ,:. ....... __ _ ' .r- . -: : ' ' '"':~' .,.;,--" :~ ~ -~... r~,~ ~~~~ :., :J,_ ' .._ ";~ ': - ' ; .,;~,: -~~;~~'::-,.:.f:-;;~~'f ~:-:~i';q;~:-;,:i~"-,,t:-'".a,;~;.~..:~ J;;ig;t. ~~~...-..~-~~~~n~y~,~~,~;e...-..~*~-~--~*"""'*'~"ttioaM'M<~""'~.....,;M.i;O..;;.-~------'""'""""...,....,""""....,_.,.,.......,.....,..__.......,....,.._...,.~- : l . 1 ..y._ .. .. "' ..... ~--': 1:.' - ; . < . , 2..-. . ;:_' . ... .. ~:~: :::. ~o'.J '' LL'XG CAXCf.R I.I-..' ASBESTOS M!Xf.RS TABLE 22.-.\'mnbtr nf Lung Canccr Deaths and Rate f'cr 100.000 Jfan-} cars Counties .\dull '.\l.lll' Popuh.1t1un Rote per 1~52 1950 1951 10;.2 19~3 19:..i 1955 Tot.11 100.000 '.l!egantlc County 13.100 3 I 3 3 4 15 18.9 Eight ".l.djacent" Counties 97 ,t;o() 6 3 9 Jfj 1r. 54 9.4 Eight Selected Counties "3 tKKt 2 10 5 JS 5 9 49 9.8 Pro,!nce of Quebec 1,19,,ooo 196 220 245 303 303 357 lf124 22.6 Pro\ince of Queb!,c less eight "adj3c1'nt" counties '.\lontreal et Isle de Jesus 1.100.tJOO 190 3\+1,000 3 217, 236 158 ~7 192 ~ l&~ 3H 1570 2"25 770 23.~ 32.3 It Is as;umed that all male lung C'<>nt"r <lo3th~ ocourred after age 20. immediately surrounding the asbestos-producing areas is practically identical with that of eight counties selected for comparison. While Megantic County has a rate nearly twice that of the combined eight selected counties, it is lower than the rate for the ProYince, and considerably lower than the rate for 1vfontreal. The figure for Montreal would certainly be higher except for the \'ery low numbers of deaths reported for 1950 and 1951, and it would appear that in those years some error in reporting has undoubtedly been made. On the basis of tht' other years, 1950 and 1951 deaths would be expected to be about 200 greater. This would result in a rate of 40 per 100,000. The only possible conclusion from this comparison is that there is no e\iclence that the persons who liYe and work in the counties surrounding and adjacent to the asbestos-producing areas haYe any greater incidence of lung cancer than those who liYe elsewhere in the ProYince. Comment on All Recorded L1111g Cancer Cases, Li<:ing and Dead, among the Asbes- tos Mincrs.-Although a simple enumera- tion of all the known or suspected cases of cancer of the lung in these areas has no particular Yalue from a statistical point of view, it is of interest to summarize such cases for the record. There were nine deaths prior to the beginning of the time period cO\ered by the study, including one in which the diagnosis was mediastinal lymphosarcoma. During the period coYered by this investigation, there were nine proved cases and three mspected case~ in the cohort. Through 1956 and to date in 1957, there were eight deaths, six of which were merely suggesti\c oi cancer of the lung and incluclecl ~uch cl i a g n o s e s as mecliastinal lymph(J~arcoma. mesothelioma, cancer of the leg with mt'ta~ta~es to lung. abscess of lung. and cancer oi the p:mcreas. One other was cliagno~d on the basis oi x-ray only. In addition. there are now li\'ing four cases in which the diagno~tic e\'iclence is strongly sngges\iYe of lung cancer. This is a total of 33 cases of "-'111 types. including 10 "suspected"' but unprowd cases, and -t that are still liYing. The remaining 19 constitute the total of prond cas6 oi cancer of the lung among the a~be:-.tos miners since 1940. The fHO\ ed cas6 aYeraged 59 years of age at rleath. ancl \'aried bet\\'een 37 years and 68 ylars. Their \rnrking span COYerecl periods Yarying from a minimum of 1-t years to a maximum of 37 years. Only three men hacl less than 25 years of em- ployment in the industry. Senn among those on \\'horn such information is anilable had a \\'eighted exposure placing them in Category III. and six \\orked in an exposure represented by Category I. There \\ere only 17 among these pro\ed hmg cancer cases in which we haYe information regarding the presence of asbestosis. Asbestosis was present in nine, although it was minimal in two. Two pathologists disagreed regarding its presence in another. At least seYen of the 19 prO\ed lung cancers, therefore, were not .accom- panied by asbestosis. Summary and Conclusions I ntert:>st in the question of whether there mav be an association between lung cancer Bra1m-Tn''n 649 ... "' 1:1:.d ,,j tlw 1. : ll~. : \\ .1- \ . I 11 I'<" 111 rj 1::~1~ !.d '.i !'t !I. . ~ "' I t ~ 11j J.; 4 "1h Ii l''.:: ;u 1it1tt '.! :1 i ':I 111111. ; .11 li !11 t" itt . :h11 .. A. M. A. ARCHIT"ES OF IXDL'STRIAL HT:ALTJI and exposure to asbestos has been eYident ~ince the report in 1935 by Lynch and S'mith oi a case in which lung cancer and asbestosis ,,ere both present. As additional cases in which the two diseases coexisted were reported, a causal association appears to haYe been gradually accepted by many authors, although some workers considered the correlation to be inconclusive. The present study was undertaken in an effort to determine whether a causal relationship did, in fact, exist between exposure to asbestos and cancer of the lung. Since most earlier studies had been limited to enumerating the lung cancers found in cer\ain selected samples, such as cases coming to autopsy or death certificates in which asbestosis was mentioned, it was apparent that they could not fulfill the requirements of an epidemiological and statistical approach to the problem. The present study was, therefore, designed to meet the requirements of this method. After a preliminary survey to explore the ;l\'ailability of reliable infom1ation, data were gathered on workers in the asbestos mines in Quebec, based on their medical records. A cohort was defined as a group of asbestos miners haying at least fiye years of exposure and who were in the indu:>try was not possible to trace 133 of these for the "hole period. but 5771 of the remaining 5958 \\ere found to be still li,ing in 1955 or later. Of the 187 known dead. cancer of the lung was considered to have been reasonably pro\'ed in 9 and to be strongly suggested in 3. The members of the cohort were studied with respect to age, length of employment, a weighted a\'erage of their exposure, and their smoking habits. It was found that 4673 were smokers within the definition of that term as used in this study. Thirty-four per cent of the cohort were more than 45 years of age. and thirty per cent had been ~mployed for longer than 20 years. Thirty per cent had a weighted exposure which placed them in the category of highest ex- posure. The mortalit\ rate for lung cancer, as computed on the basis ~ nine "proYed" deaths among the cohort was 25.3 per 100,000. \\'hen the three "suspected" cases were added, the "total" rate for the cohort rose to 33.8. The importance of the suspected but unprO\ed cases in determining these rates has been reiterated because it is likely that such cases would not be included in the statistics for the general population and becau~e ,hey inf.uence the :esults so m::irk- in 1950. Data relatiYe to their characteristics edly. were collected and their status at the end According to the findings in this study, of a six-year period of obserYation was de- termined. In the case of those who had died, an exhausthe search of death certificates and insurance records was carried out in order to determine as nearly as possible the exact cause of death. Mortality rates from lung cancer for the general population of the PrO\ince of Quebec and its various counties and for the Dominion of Canada, as well as the 'Cnited States were calculated from statistics collected in the appropriate places. Comparisons of the rates obtained for asbestos workers and for the other population groups were made according to ac- cepted statistical methods. Records were obtained on 6091 persons who fulfilled the criteria of the cohort. It the mortality rate from lung cancer does not appear to increase with length of exposure or with degree of exposure, a fact which presents strong e,idence against the carcinogenicity of asbestos. Comparison of the experience among the asbestos miners with that of various segments of the unexposed, comparable population shows that the obserYed number of deaths among the miners is not significantly greater than the expected riumber. The rate for pro,ed cases among the asbestos miners (25.3 per 100,000) compares well with the rate of 22.5 per 100,000 for the rest of the Pro\'ince, and 20.8 per 100,000 for adult males throughout the Dominion of Canada. It also compares satisfactorily with rates 650 Fol. Ji, J1me, 1~58_ . ___ . . -~-~ ._ ........ ~-~- --~ ,, -~---~----'----- --~-----.-... . -_:-=.:::::..:_.:___:._-_ _ _. _ _ _ _. - u:sc CA.\'CT:R /1\ ASBESTOS .UI.\.LRS of 37.2, 25.3. and 28.0 obtained from nrious sources for adult males in tht: lnited States. Finally, in this matter of comparison, it 6. Behrens. \\".: Experimental .'\s!Jesto3:-. Schwe1z Ztschr. allg. Path. 14 :2i5-2;";i, 1951. i Behrens, \\"., Jr.: The Cl would appear that the world-wide experience Pathology of AA,estosis, inical Picture a!1 .. Ztschr lniallmed. of persons exposed to asbestos dust is not Deruiskrankh 45:129-140 (.lune 15) 1952. t: worse with respect to lung cancer than that of the unexposed population. 8. Berbling:er, \\'.: Incrc:ase oi Lung Cancer and Disea<es Due to Dust Inhalation, }.fed. !\:!in 2i:l33i-1342 <Sept. ll) 1931. The counties surrounding the asbestosproducing areas, in which it is presumed 9. Berenbl um, I.: Irritation and Carcinogene<;i-. A. rch. Path. 38 :233-244 (Oct.) 19++. most of the asbestos miners liYe, haYe almost identical mortality rates with those of eight counties widely scattered through the 621:(0)28B-9e3h0ne(:Ju..\nsebe:5<)tos1is9,36D. eutsche med. \\"clmsc:.r l l Bohme, ..\ : Results oi Periodical Examin;,. Province, and are lo\\"er than those for the tion< oi \\"orker< in :111 .\shestos Factor:-, Beit~ Siliko<e F(irsch. 11 :34, 1951. remainder of the Pro,ince, and much lower than the rate for l\Iontreal. Since 1940 there ha,e been 19 cases in 12. Bowles, 0.: Ashestos-:.filling, :\farketi1:; and Fa! ricat icm, In formation Circular Xo. 686'.J. l'. S. Department oi the lnterior, Bu which the diagnosis of primary cancer of :.rines. 1933. pp. 1-26. reau c: the lung may be considered to haYe been proved. Approximately half 13. Bre<lo\1, L.; Hoaglin, L.; Rasmussen, G . and ..\hram<, H. K.: Occupation< and C1garet of these cases were associated with asbestosis. All but one died in the recognized "cancer-age" and at Smiiking ~ Pul Heall ii. 14 Bristul, 1C Factors in Lung Cancer, ..\m. .l ++ lil-181 (Feb.) 1954. L. .I.: Roentgenolo,;ic .-\~1,ects least one-third had only the lightest ex- Silirnsi; and ..\sJ.,estosis, A. M.A. ..\rch. o' Indmt posure (Category I) to asbestos dust. Health l l :189-195 (},!arch) 1955. On the basis of what are beliered to be 15 Cancer oi the Lung: An EYaluation oi the complete and reliable data, it seems fair to ProLlem. Proc-eedings of the Sciemific Section. conclude that the asbestos miners in the Province of Quebec do not ha\e a signif- ..\11:1ual :'.\Ittting. ..\merican Cane-er Society, Inc.. ::-\01. 3-4, 1933. ::\ell" York. American Canct' Sucitty. Inc., 1956. icantly higher death rate from lung cance; than d') comparabl~ s.:gments of the general population. 16. Cartier, P.: Asbestosis Cancer oi the Lung. in discussion on Smith. \\'. E : Sun ey oi Some Current Briu<!J and European Studies Furthermore, the death rate from lung tional Tu111<1r, Problems, of OccupaA. M.A. ..\rch. Indust cancer in the areas contiguous to the asbes- Hyg 5 :262-263, 1952. tos operations is comparable to that in areas widely scattered thro l i. Cartier. P.: Some Clinical Observations oi Asbrno~i;; m :'.\line and :.fill \Yorkers, A. 11. A ughout the ProYince of Quebec and is lower than in some urbanized areas within the Province. ..\ rch. I nclust. Health ll :204-207 (:.farch) 1955. 18. Clerens, J : Research into Pulmonary .-\sb~s to;.is in Belgium, .-\rch. belges med. Sociale 565 IXoY.) 1951. 8 :55i- REFERENCES 19. Clynes: Asbestosis and Silicosis, Brit. 1L J. 1. Alascio Escobar, R.: Bronchial Carcinoma: l :3i9, 1931. 2R6e:v3i7e5w-37o9f 2(0S0epCt.a)ses1,95J6.. Internat. Coll. Surgeons Pa2r0d.eeC,oHffi.n.E.G.B..,T.; Duryee, H. C.; 1faier, H. C.; 2. Allen, M. L.: Bronchiogenic Carcinoma As- oi Tobacco and Wynter, E. L.: The Effects Smoking, Panel Meeting, Bull. 1\ew sociated with Pneumonoconiosis: Cases, J. Indust. Hrg. 16:346-3 Report of 2 York Acad. :.led. 32:133-156 (Feb.) 1956. 3. Cartier, P.: A 4i (:!\O\.) 1934. umtribution to the Study of Asbestosis, Arch. ma!. profess. 10 :589-595, 21. Cohart, E. M.: Lung Cancer and Economic Statm, Cancer 8:1126-1129 (Nm.Dec.) 1955 22. Cooke, \\. 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