Document XOaL2YGYxL3gXb9g6bEyN5Y5K

( c fitprinted (ram the A. St. A. 3r<Awci a( Indtittriat Health. June 1753, VoL 17, pf. 634-453 Copyright 1953, by American Utiiieal Atjoeiotion , from An Epidemiological Study of Lung Cancer in Asbestos Miners OANICl t MAUN. MJ),, d T. DAVID T*UAM, M.A^ Pirnkuryh Ever since the pronounced increase in the incidence of lung oncer among males became apparent, there have been attempts to associate it with one or another of the various elements in the environment of man. The approach used by some workers has been to suspect one or several sub* s&nces and then set about in an intensive search ior lung cancer among persons who have had any exposure to those materials. In this connection. Smith ** writes: "The tendency of authors reporting the coinci dental 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 inevitable that asbestos should come under scrutiny in this manner, because prolonged exposure to this material is known to cause a specific type of pneu moconiosis, and because persons who show this form of pneumoconiosis often come to autopsy and provide 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 accu mulate after the report of a case by Lynch and Smith** in 1935. Within the next 10 years, about 15 additional cases were re ported. and in 1954 Merewether1* reviewed all deaths from asbestosis recorded in Eng land since March, 1924. Lung cancer oc curred in 16ft of these cases. Gloyne,*1 Accepted for publiation Jan. 20. 19S8. This, stwiy was made possible through a fram frran tbs Quebec Asbestos Minins Association. Holies! Director (Dr. Braun) and Statistieil Consultant (Mr. Tran), Industrial Hygiene 694 whose work is also, frequently referred to as establishing a connection between asbes tosis and cancer of the lung, reported in 1951 that cancer of the lung was present in 14.1ft of asbestosis cases examined by him. In 1941, Nordmann and SorgoM claimed to have produced lung cancer in mice which they exposed to asbestos dust. Since 1951, additional cases of oncer of the lung coexisting with asbestosis have been reported, and, according to Kueper** about 100 such cases had been reported up to 1955. As a result, an association between the two diseases appears to have been ac cepted by many authors, and several writers were using the term "asbestosis cancer" of the lung. Werber.** in 1952, stated cate gorically that in 7ft to 17ft of cases of asbestosis. after a latent period of about 1% to 20 years, carcinoma becomes estab lished in the lung. On the other hand, not all authors ac cepted this alleged association without reservation Saupe * in 1939 reported that he had discovered no cases of lung oncer among 620 cases of asbestosis which he had examined; and in 1942, Holleb and Angrist ** expressed the opinion that the number of eases of asbestosis with lung cancer was loo small for statistical evalua tion. In 1947, Wegelius** reported 126 radiologicdly 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 Merewcther's latest book,** sate: "But at no sage in all these impressive researches wns any due obtained which might have offered any support to the possibility that srh-stes co.ild act as s zl. .!. "" . i j  I.UXC CANCER IX ASHHSTOS MINERS at is iiu reliable criterion by which one ctiv '`scheduled'' ureas, by which is meant, .mtieipmc circiiiusfeniciiy and. as is well known, relatively mhiuic changes in the structure of a chemical carcinogen are suffi cient 10 diminish or climinan: carcinogenic `those areas where processes are carried on which were scheduled under the Asbestos Industry Regulations of 1931 as being dusty." . action. If asbestos is indeed to b$.regarded.as a arcinogen, the need is felt to danonstratc some property which on be regarded as something more lhan inertness." These authors advance the theory that, until some more experimental evidence of direct carcinogenesis by asbestos or a <iecum|>osuion product of it can be obtained, asbestos might be considered as a "co-car* cinogen" which" only induces a further de velopment of a preneopiasttc condition brought about by something independent of the asbestos, such as an endogenous factor. Thus the literature, while tending to sup port the thesis that asbestosis is in some way related to the development of lung cancer, is by no means unanimous. Alto gether, it is perhaps more confusing than enlightening. A careful review shows that the majority of the reports are clinical and uot epidemiological. They lack many ele ments necessary for the application of epidemiological techniques to their content, and most of the authors do sot make claim to having done so. What has happened is that succeeding authors have drawn conclu sions and generalised beyond the $co{r of the works which they quote! Nowhere, tor There is, furthermore, a complete lack of definition of terms as used in the pub lished literature. For example, the term "asbestosis," as used, may refer to changes observable only by microscopic examination ot the lung tissue, or it may mean a radiologictlly detectable condition. Most of the published repons obviously included women among their cues, but some >f them do not give the number or proportion of women involved in the study. There is also a lack of uniformity as to what ryie of exposure most studies have dealt with. Of 99 cases enumerated by Hucper4* in 1955. only 10 apr>ear to have originated in the United Stales, and 7 in Canada. Some of the earlier reports ap parently included asbestos miners, but it can be assumed, since S2 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 have involved workers in the textile or fabricating industries. Such factors as smoking habits, family history of cancer, length of time in the industry, and age of the individual case are also notably absent in the majority of these reports. example, have -we found references to a population of asbestos workers, although several authors who have quoted the ob served incidence of lung cancer in autopsies With this understanding of the limita tions ot the existing literature with respect to epidemiological generalisation, it may be of value to consider in somewhat more de of persons mho also had asbesiosis imply tail some representative earlier publications, that this incidence applies to asbestos work a few of which were referred to briefly ers, generally. We have likewise bent above. unable to find any study which actually One of the most detailed studies and one calculated the incidence of lung cancer which deserves the most serious considera among a population of person* who had tion is that reported by Doll54 in 1955- asbestosis, and not just thoe who enne to This study reviews causes of deith among autopsy. With the exception of a jKi|>cr asbestos workers based on coroners' rec **y r`oH,*s none of those reviewed gave any ords. It uIm> u,e hk data on exj>osurc ami dust concentrations, l*y studying records of men who worked and even Doll's paper merely mentions for at least 20 years in exposed situations. i 1 SreiM--TniM A/ 635 o * A. M. .4. AfHIlIVl.S or STRIA/. HI-.AI.TII Doll concluded that lung cancer was a spe cific industrial hazard of certain asbestos workers and that, after 20 years of expo sure. the risk is 10 times as great as for the general jwpuiation. This article is important for several rea sons. in addition to the definite conclusions at which it arrives. For example, it- .begins by stating that "in view of the infrequency of asbestosis. this large number of cases ('61 cases of lung cancer) suggests--but does not prove--rihat lung cancer is an occupational hazard of asbestos workers." Neither this article nor any previous one which we have examined presents any fig ures to prove that asbestosis is an infre quent occurrence. Estimates of the number of persons potentially exposed to asbestos dust in the United States alone van- from 10,000 to 35,000, and the incidence oi asbestosis of any degree might be higher than Doll imagines. This study, like so many others, involves autopsy records. The number of persons involved in the statistical analysis is only 113, representing only 1,042.25 man-years of life. It is also true that in selecting men who had been employed for at least 20 years, the study automatically excluded those who died from other causes after shorter employment. Another reason why this publication is ot importance is a statement which it con tains to the effect that "the strongest evi dence that it (lung sneer) may be a hazard (in asbestos workers) -has been produced by Merewether and by Gloyne." In 1951' Gloynepresented a review of 1205 autopsies on persons who had worked in various dusty occupations. This number included 132 asbestos workers, of whom 121 showed "pneumoconiosis"--pre sumably asbestosis. Primary- cancer of the lung ocairred 17 times in this group, an incidence - rate of 14.1% 'for lung cancer among asbestosis cases coming to autopsy. There were in his series 796 cases with sili- 6,9% of these also showed pri mary cancer of the lung. The' incidence of lung cancer in other forms of pneumoconio sis was 6.7%. and in 169 cases which proved not to have any type of pneumo coniosis it was 8.35<-. Gloyne considered "the mortality of the asbestos workers" to be "disturbing." First of all, it is obvious that the paper does not deal with the "mor tality of asbestos workers." and secondly, it must be borne in mind that all of Dr. Gloyne's cases were submitted to him for study because the findings were unusual for uncomplicated pneumoconiosis. It can reasonably be assumed that cases, including those of asbestosis. tn which the findings were not considered unusual were not sent to Dr. Gloyne for examination. As a nut ter of fact, in the same paragraph in which he expresses concern over the incidence rate in asbestosis. Dr. Gloyne himseif points out that the rate for lung cancer based on necropsies at the London Chest Hospital was 21.3ft while the figures of the Registrar-General showed only 2.4%. He thus recognized that autopsies on a cer tain selected group of cases were not rep resentative of the general population. It would seem. then, that notwithstanding the value of Dr. Gloyne's work, its importance as an index of the prevalence of lung can cer in asbestotics has been misinterpreted by some who have quoted him. All that it really shows is the faet that in a group of 121 cases, selected for special study pri marily because they seemed abnormal by preliminary examination. 17. or 14.1ft, had lung cancer. Merewether15 in 1947, in the report of the Chief Insjfector of Factories, reviewed all cases retried between 1924 and 1946 in which asbestosis was the cause of death or a coexisting condition. This work was later extended to include all such tases re- jwrted up to December. 1954, by which time there were 344 deaths, including 205 males .and 139 females. Among them were 55 cases (16%) of cancer of the lung. 41 in males and 14 in females. It is quite possible that a large number of wk a;a not die of their asbestosis. or in whose 636 tV/ }?, Junf. jw AV i U W'C C.4KCER IX .4SUEST0S MIXERS death certificate it wa$ not mentioned, may have been missed- The import of this 16% is enhanced by the simultaneous statement that the incidence of lung cancer in autop sies of the general |>opuintion 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 variables, such as smoking habits, is obvious. Lynch/0 who with Smith ** 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 manu facturing plant who were shown to have ''demonstrable deposits of asbestos in the lungs." This, of course, is not necessarily identical with the disease asbestosis. Lynch, himself, points our that, although this is an incidence of 82%. "both figures are too small tor very serious statistical types of calculation." Nevertheless, later writers have used this paper to strengthen the case for an association of carcinoma of the lung with asbestosis. It is also of interest that Kfotz ** found only the same number of oses of lung cancer in a- series nearly 10 times as large, i. e., 4 in 478 cases of asbestosis. Behrens, as cited by Merewether/* esti mated that, of 309 cases of asbestosis in the literature, 44 showed associated cancer of the lung--giving an incidence of 14.2%. This is an illustration of generalizing an incidence obtained in a group of cases which were undoubtedly reported only 6e- coute some of them showed lung cancer, to possibly hundreds of asbestotics whose cases were never reported. The same ap plies to the conclusion of Teleky,** who appears to have reviewed 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 written so exten sively on the subject as has Hucper.1*s* In 1955 he reviewed the cases M reported prior to that date and enumerated a total of 99. Eleven of these were those dis cussed by Doll :l and may have been cases covered by other authors. Eight were dis covered by Kennaway and Kennaway*5 in an analysis of death certificates, and. unless Merewether's study was incomplete, these oses should have been included in his re port. Of the remaining SO, it is quite pos sible that the 31 contributed by Merewether and the 17 bv Glovne contain some duplica tion with each other or with those of other English authors. Principles of the Epidemiological Method Dorn J0 has pointed out that much of what is now thought to be pertinent concerning she comparative frequency of lung cancer in ditterent population groups has been de veloped from the analysis of clinical ma terial, particularly surgical and autopsy records, supplemented to some extent by the reported impressions of various clini cians based upon their personal observa tions. More recently, however, attention has turned to the systematic investiga tion of this problem by the same methods that have proved so successful previously in the study of communicable diseases, that is to say. by epidemiological methods. In order to apply this method of investi gation 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) available data for ail members of this population, including the healthy as well as the ill; (3) a sample which is truly representative of the popula tion; (4) reliable and valid observations relating to the problem of the study. A serious defect, common to most of the studies which have 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 asbesm* workers, it is necessary for a study to in clude living persons as well as the dead. B'6iu*--Trnan K\T A. M. A. ARCHIVES OR INDUSTRIAL Hl-.At.TH Limiting the investigation to cases coining to oujo/-i\f, "as has been trequemly oone in earlier studies, still further restricts its use in generalization. The problem with which we are concerned is whether asbestos miners experience more lung cancer than does the general population. The answer necessitates the collection of reliable infor mation on asbestos miners as a group, as well as on the general population. It seems advisable to discuss the differ ences between the epidemiological approach and that used *in the studies which have been reported to date. A very important consideration is the fact that lung cancer, in spite of its increasing numbers, is still a disease of iovv incidence; that is, in a given population not many persons will contract this particular disease. This fact requires that large samples or groups must be stud ied to provide meaningful results. Recognizing the difficult)* of obtaining such large samples, most earlier writers deviated from the epidemiological method and sought to circumvent the requirement of observing well persons by (1) compar ing the fdc'ize frequency ot cancer in vari ous sites: (2) comparing the relative frequency of cancer in a group of hospital ized patients: (3) comparing the relative frequency of cancer in a group of cases coming to autopsy. Attempting to compare two population groups, looking only at the relative fre quency of cancer in various body sites, may result in finding ^higher percentage frelative frequency) in-one of the groups, when, in fact, the mortoiily rate of cancer of a particular organ is exactly the same in both groups. This is- very clearly dem onstrated in the excellent article by Dorn.*0 The mortality rate from a particular cause \s the true measure of comparison.- It is apparent that selected groups such as hospitalized patients or autopsy cases may not be in any way representative of a larger group, and that in dealing with such samples, the observer may easily find cases of a given disease than would be found in another group of the same size, out representative ot the general population. U is true that investigation of cases from such a sample can furnish information valuable for research, but the use of this information in drawing generalizations is necessariiv restricted. Jt is the obligation of both the investigator and of those who read his report to make proper comparisons and to draw only those conclusions which are valid and justified. A good statistical study oi cases of cancer of the lung occur ring in a group of autopsies can lead to a proper inference concerning the frequency of lung cancer among cases coming to autopsy, but only to such cases. For in formation from such a study to be pro jected to some larger group, it is necessary that the autopsies represent a good sample of that larger group. To assume that such is the case in any particular series is dan gerous and likely to be false. There is some danger that the figures reported by some authors may be miscon strued as applying to asbestos workers or even asbestos miners, when, in fact, the authors in question do not make this gen eralization. mir can the generalization be nude for the reasons stated. Gose study of the reports reveals that the percentages cited relate only to the group of autopsies covered by the particular investigation. The present study, in contrast to the earlier works, has been planned to utilize the epidemiological method. A well-defined group of asbestos miners has been estab lished in such a wav that it constitutes a good sample of the whole population of asbestfo miners in Quebec. Data for all members of this group have been collected anti analyzed. Those concerning lung can cer have received most careful considera tion. DeuviU of the methods employed will be set forth later, but the type of approach is considered to. permit of fair comjmrisons and valid generalizations. Collection and Analysis of Data A preliminary survey cf pv......juices of information in February, 1956, involved 638 Vet. 17. Ju*r. I9M /-/ l.ry't: CJXCF.R /A* .-tvrt/.cym- v dincussions with the pliv>ici:utN iu charge cohort ;is then followed by nic.ni-> of the of the asbestos companies* pr/>gr:mi anil annual physical examination records with clinicians. |>atholngiM$. reprtrseiuaiivi-s through a dx-year interval, 1950 through of City and Provincial health dejwnnwnts 1955. All data regarding this group were and of the Canadian Cancer Society, and then tabulated in order to determine the whet interested }>crms. It was found, that characteristics of the cohort. For those who morbidity data, although somewhat limited, survived the entire j>eriod. reference was were available from such sources as the made :o the physiol'examination results hospitals in Montreal and Quebec City, and and x-niy findings at the end of the period. the 13 cancer detection centers in the Prov Those who had died were tabulated sepa ince. However, because of the high mor rately. and the cause of death was tality itt lung cancer, it seemed advisable corroborated by examination of the death to deftend upon data relating to deaths. certificates. A further search was made These we found to Ite obtainable at the concerning those in the original cohort who vital statistics department- of the Ministry remained unaccounted for when the living of Health in Quebec City. From the pre ami the known dead had been tabulated. liminary survey, it was ap|nrem that exten They represent men who had left employ sive and detailed information could be ment through retirement or resignation. gathered with respect to both the |>er<nn* Kventuaiiy. all but a small number of these employed in the asbestos mininc industry were accounted sot as cither living or dead. and the mortality figures tor the general ;uui iu the latter event, the cause of death Imputation.. was substantiated in a similar manner, and Following., this exploratory survey, the - the resuits added to the original list of initial eti'nrt was directed 10 the collection deaths. of data relating to all workers who had Death certificates for the Province of been processed through the clinic at Thei- Quebec tor the years 1952 to 1955, inclu forri Mines since its inception itt 1947. and sive, were reviewed in the department of similar information regarding all workers vital statistics of the Provincial Health at Asbestos. Que. Dam from the clinical Ministry, together with statistical sum records included the age. family and per maries of the causes of deaths in the Prov sonal medical histories, smoking habits, ince by counties. All cases in which death number of years of ex|*surc. an estimate was certified as having been due to pri <( weighted ex|osurc. and the course of ntary cancer of the lung were examined for the individual's health stains or the cause such information as place of residence, of his death. . ' occupation, date of death, hospital in which From this information it was )*visible death occurred, and whether or not an to formulate a "cohort" which could be well autopsy was performed. Cases its which defined, should be representative oi the lung cancer was given as a cause of death, whole group, and could be follower! for a but in which it was not specified as to definite period of time. All of the available whether the cancer'originated in the lung, experience* indicates that the development were also reviewed in an effort to include of asbestosis io less than five years of ex all instances of primary carcinoma of the posure must be somewhat rare. Accord lung in the study. ingly, the cohort was defined as including The statistics for the Province of Quebec every miner who had a total exjsure of relate to population, total deaths from all five or more years, and who was on the causes, total deaths from rmc:r employment rolls in 1950. Office and other and deaths from lung cancer. These were nonexposed personnel, regardless of length collected and tabulated by counties and by of employment, were not included. This sex for the years 1950 to 1955. inclusive. Bratett--Tmon 639 A. M. A. AHai/niS or ISDISTR1AL HhAl.ru From-(hem, death rates for the geneiai population of Quebec and of individual counties were calculated for specific years and analyzed by cause. Practically all employees of one company are covered by a group policy of life insur ance which, fortunately, nearly all of them continue to carry when they retire. A very few are not covered by this policy, and those who leave the industry for one reason or another except retirement usually are no longer covered, but this is likewise a small number. As ait additional check upon the information obtained from the clinical records on this group, .the records of the life insurance company were examined for all death claims paid tinder the policy, and particular notice was taken of the claims in which the prooi of death was based on cancer of the lung. Deaths from lung cancer among asbestos miners were thus determined from the clinical records in the medial service of the industry and checked by means of the death certificates and insurance company records. The deaths were then verified individually by reviewing them with the physicians in charge of the medical services. In this man ner, there was established a list of cases in which primary oncer of the lung is con sidered to have been proved as the cause of death. A few cases in which lung cancer is strongly suspected but not proved as the ause of death were considered separately. Mortality rates have been calculateri^using both the "proved" and the total of "proved" and "suspected" cases during the years un der observation. Comparisons were then made between the death rates from the same cause among specific segments of unex;>o5ed persons. All lung cancer deaths, both suspected and proved, were carefully ana lyzed to determine possible relationship or correlations between the develojiment of lung cancer and any factor known from the clinical records, such as family history of cancer, personal history of heavy smoking. ot asbestosis, or exposure to asbestos. 640 in audition to thi> analysis ot deaths oc curring in the cohort and during the years under observation, every known death from cancer of the lung, as well as even- case diagnosed but still living, has been tabulated and analyzed. They will be discussed separ ately from those included in the population and time-interval under study. A comparison of lung cancer mortality in the asbestos-producing counties has been made with that in counties which are far removed from the asbestos mines and in which, presumably, no asbestos miners live. Finally, in order to broaden the compari son of death rates in different population groups, the rates have been collected for Canada generally, ami for the United States, according to the me: recent published and unpublished materia!. Results and Interpretation The cohort which was constructed accord ing to the criteria described in the preceding section has been considered individually and compared with the general population. Description at the cohort will be presented here as a preface to the results of the study: Ortciml CoWt Prr'ai* IMucirJ Fin*l CSxn Ijfjfic in 1955 (`nrkin* ml rvnml) l>na w ms Ctxtrt ( Ivme UimtKrtUblc 19*C*f il Inn,' Other vm t'Ahmvn f.uMl .Vmwglnt Vnltiiovn 6,Ml 111 5,951 ua m 9 .j 149 4 .tn 1J4J 20 Tables 1. 2. 5. and 4 present age. number of years of employment, weigh'.ed average cxjiosure, and smoking habits of the cohort. A co*.n|>ariMiu of the exposure to asbestos dust is presented in Table 3`. All members m the cohort were placed in one of three categories, representing increasing degrees of ex]x>sure based nn a weighted average of the years sjxnt at various levels of dustiness. The degree of dustiness for each job category was determined a*rer cor'-*'**, liuit with persons familiar with the environ ment and conditions in the various work V,,t. 17, WS* /-v 7 7^0 LUNC CANCER IN ASBKSTOS MINERS TaALS l.--Number tmd Percentage Dillributw* Ta*LC Z--Number and Percentage Distributive by ______________________ >V . Length of Employment he* SoOn-M..,. UarnaTi" "' ! ............. it*--............... ,,... NubMr J.: i.rc* | * lev this 9J%. rr Cent H 19 * Unrtfi ( Ifflpw'orm >........................................................ 10-U........................................................ -....................................................... M>........................................................ r...._................................... ......... ........................................ Nus>t*r l.TM Uh ns va IU u LftU tee C*( X 40 >1 . )0 I 1 100 areas. For the purposes of calculation, the assumption has been made that the relation ship between these categories is linear, and that Category II is twice as dusty, and Category III three times as dusty as Cate gory I. uallv smoking more than five cigarettes per day. Persons who smoke pipes or cigars exclusively were not considered to be smok ers ior the purpose of this study. Table 5 presents the yea--by-year ex perience of the cohort and indicates the Taste A.--Number and Percentage Dittriovtiem by Exposure Category Tasl 4.--Number end Percentage Distribution by SmoPtno Hcbets Eiootwi Ciutorr I....................................................... Numrur HUant..nWi,,.......... .. AMflft ................................... .................... Lea iOid 1 Per Ceei 2* 2* Soierier Hiuu imttn................................. NentmrtKfrt Ontoova................. ^oul>._.............. *t4t!o oar*. HusMr ?r Cni : 21 100 The fourth variable, smoking habits, was similarly tabulated and is shown in Table 4. This was included because the informa tion was available and because smoking was regarded as one of the variables which, besides the environment, eould conceivably influence the development of lung cancer. As used in this presentation, the term smoker refers to a cigarette smoker, habit* number of deaths each year from specified <ause$. In general, a case was considered to be "proved" as one of primary cancer of the lung when the records showed that die diagnosis had been supported by an autopsy or surgical resection of the lung with microscopic examination of the re moved tissue. In one ase so considered, however, diagnosis was confirmed by bron- Tails 3.--Y ear-oyrear Experience of Cohort a. na tseatn nmfj ' MomYeori of Risk N. AJi at 8tianioc *t Vw Fntearr Ct. M Lucie Cum DaU SonxnM rnairr C*.K Lunt Other C<ww *Ti*wd~ fW Mr loan nto-tMit at tm> -- SJ ISJBiJ tt--n per tUijsjO B*A->un M rat - - mMM tlu-Ynn MfttM i.tn Mttt Uvnas umia Broun--Tneon a* < (.ORicr Deaths by Length Sinfioyncnl So. of Tov 1-tnoM i.vo uT*S I 1S 4 no 0 *, Ooo.h R..O \<lfV Ecmu JWW ' 000 Tv,*` A. it. A. ARCHIVE* OF IXDCSTXiAL HEALTH TaiuC 6.--"Proved* Cotes Of Primary Cancer Of the Lung All Seekr Ctpnun 4* tt W Y4 <4 Yu 23 jt- in Cm. U 41 M Xt * j* rr.rn Cjl i U V S rr. m C4L U1 D>M tP-13-Sl >-4-M Kfr-Xr 4-75-SJ 4-W-SJ 11-23-M *- S-K y -u Amepif Vi Yu So Ytt Vo Vo Branch. Yu No So So Vfi Xti Yu No i visualization and biopsy. In would be very close to the 95% level /ugh there was no autopsy, the of significance. However, having found just primary cancer of the lung 12 cases, we are not above this level, and been beyond question, therefore the hypothesis that asbestos miners .uspected" primary cancer o: do not have a higher mortality from lung those cases in cancer than does the general population can -~s in doubt but not be rejected. Nevertheless, the occur . joints to cancer of the rence of 12 cases in this sample would ere three such cases, increase the rate to a point which approaches an-years of risk" has been the significant ievei. Because oi the tre he number of men at risk mendous importance of the questionable nder observation. A person rases in this respect, some detail regarding ighout the year was counted them will be given here. :r of risk, but one who died In one of these cases, the suspicion of was counted as one-half a cancer of the lung is based upon the x-ray interpretation, and. although no autopsy was ng in the cohort, and in performed, the death certificate indicates rr is considered to have that death was due to lung cancer. It is cause, are shown in Table well known that the x-ray appearance of shown three deaths which fibrosis, especially if a localized density or rred as "suspected" lung a superimposed tuberculous lesion is pres ent, can simulate that of a tumor, and by the importance of these itself, does not justify the inclusion of this a interpreting the results case as one of "proved" cancer of the s is desirable before fur- lung. A second case was certified as having the mprtaiiry rates which died by reason of hydrothorax, possibly due tafies. For example, it' to lung cancer, but again there was no found for the proved surgery and no (xjstmortem examination. - he `'expected" rate based In the third ensv, although it was subjected ulation figures for die to autopsy, two pathologists disagreed as to ; shown later, and on whether lung cancer was present. The death d find eight deaths from was certified as having been due to chronic -* the cohort. Actually, myocarditis with nephritis and pulmonary ved. If, however, the congestion, and possibly cancer of the lung. -cted" cases were in- On the basis of these facts, it seems unwar iis figure to 12, the total ranted to include these three cases among TaIIX 7.~'Svtpccti<t* primary Cancer of the Lung *er Yu Yw Yu Emeara it. la Cm. ftt sn.ucu.rn ttyr.MCu.tl jMtd w-ss-m 1- M2 S-20-U At*t*r Me Yu Ne . Attorna X YN*u Vat. 17, June. }OiS f b : members of the rrjnon u lung cancer at a younger neral population, y weighted exposure are : 10. and it will be noted nt strong evidence against i carcinogenic agent, for, it oestos is in any way conancer, we would expect that heavier the exposure, the that would be found. The trior in this interpretation he weighted exposures were i| to years of employment. hi t.'or<r Ocaiht ey Exposure' Cotenory nj XurnM' 1 Uunt Cixecr Dclihi VXrnn.vontt Ka. el Owim rt yi.t-.Ht C>mo Ot<uhCioRowut** Mf t.0 YU*M a t a ti Tn St n JT a t* M3 Weighted Exposure Categories 'ey Length of Employment u>Khtj Eirmufr CeiuenMoi I um M X10k-9lt ao-ji *&-< rot M114 31;1 34 SK mHi i1t7 0 4110 iwTuoiurliun Mttceian call its ciso t.m HA kuon Taut t.m t - tin4sU 0 1uU i a.o irj in which case the heaviest weighted ex posure (Category 111) would show the shortest length o( employment. Ta'oie 11. which lists the number of persons in various exposure categories by length of employ ment indicates that this error has not oc curred. In fact, the average number of years of employment for each exposure category is almost identical. _' Table 12, which develops the rates tor smokers and nonsmokers, is most striking. It shows that not a single case of lung cancer developed among the 1265 non smokers and that all cases of lung cancer, both "proved" and "suspected." occurred in smokers. Table 12 was so striking that it was felt that further verification was necessary. It was possible that some abnormal distribu tion may have occurred, e. g., the non- TasU 13.--iV*i6er and Percentage Distribution of Smokers and Nonsmokers o? Age C'ouet A* Gfoop 30-44....................... 41-J4.......... ........... A1MSA4............................................ Datnvn_......... Taub_--.. A*4ran )i(-.......... N'lUBber Soatir Xenamottt iXO n tn *24 4M m 1*4 ISO 2 0 4.C3 1.260 Cnkoavn < 3 1 l 30 40.T Smoitrt ,Vwjmo*rrj Nwtn l PtrWil iM Somber f Lu( Ciw<> itealhi ky Smootnc Kibti S. el Otfthl lnoni Totl Xonmoccn. Vaiw-r............ 4.n 0 0 0 0 Tul.,,......... l.U 3 13 Annuel LunreCi iZ'eCnr?ervSrecitafty RSmmoicueie*r H1*060.m00) MukVuti No. of Doaini SaioKm............................. XCentnnnb3o'S*...n..._.._................................................ Piotw 32 0 0 Taul 41 o 0 0f-oll................................... IS >4 smokers may have included a larger percer.ts.gt ct young men. Consequently, ad ditional Tables. U. 14. and 15 were con structed to show the distribution of smokers and nonsmokers by age. length of employ ment. and degree of exposure. Although there are siigh: differences.. they do not account for the fact that all observed cases of lung cancer were in smokers. In respect to age {Table 13) the combined average age of the smokers was 4.9 years less than that of the nonsmokers. Table 14-show* that as far as length of employment is con- Tabu 14--Number end Percentage Distribution of Smokers and Sownokeet by Length of Employment EBIvMmobrnMuni 1H0-l.................................. 3400---34J................................................... JM-.................. Aru<Tk#ottrltft....<.... ... NatsMr Smoktn NcniniSKtri ITT 43S IIAM4 1.1 s 1J VI Cnknvwn 4 04 0 ro Kt.ft hmaufi Dfrtflbuuoo Ac* Omt Snoktt Xwwwtt 30-44.............................. 4-W.......... .. SS-04.............................. U IW it >4J it.: I*B . Taisll_______ toos toon PttfcnT> OB 30B I0B SB toon Uyt thin #%. 6*4 ruTTBtan DtstHbuuon l*nttn m CnokrtMiu Smektr Mruiuokrr S4................. ........ 30.1 Unknown ............. 34 0.1 U 100% 0.0 toor. Vol. 17. Sunt. )95S LUNG CANCER IN ASBESTOS MINERS TaJU IS.Sumber and Pereentaoe Oisiribuiion of Smokers and Nonsmoeert by Exposure Category . Cautery t............................... m............................... Duao........ ............ ToieU. Axnn axpeturr cuttea SaHin 4 4.C3 It NoaiMun <51 1 1.2*9 W UeXaovn 4 * 0 9 U Fcrcaouit Pbulbatloa Creenm Cauierr Smokon Xeoatektn t................... M . ______ T7aasevp_.... JfcJ KS a.: 3S.T u T*tai_.... 19% 197. UoXbovn 9.0 49.0 04 looev cented, the smokers had worked about 2.3 years less on the average than the non smokers. With longer exposure and greater age, one would expect the nonsmoking group to show a higher rate it lung cancer were due to asbestos. Table 13 shows that the average exposure category was almost the same tor the two groups. Therefore, this variable seems to be of no importance in accounting for this difference. The result of this additional analysis is that none of these factors appears to lessen the effect of Table 12. Comparison of the Cohort Experience with that of the Province of Quebec, Do minion of Canada, and the United States.-- In order to make a comparison of the experience among asbestos miners with that of the general, population of the Province of Quebec, statistics were gathered, as staled earlier, in the office of the Division of in the Provincial Miv.i;-..v <ji Health. The data on total deaths, deaths from all forms of cancer, and deaths from cancer of the lung were obtained by sex and by county for the years 1950 through 1955. In addition, all death certihcaces which specified primary cancer of the lung, and all those which indicated Jung cancer but did not specify the origin, were exam ined for the years 1952 through 1955. Table 16 gives a tabulation of the number' of deaths from lung cancer in the Province and in the cohort tor the years 1950 through 1955, and shows the annual rate per 100.000 in these segments. It will be noted from the table that the mortality rate for the "proved" cases in the cohort is only slightly higher than the rate for the Province. When the 'suspected" eases are included in the calculation, the rate for the cohort rises to 33.8 per 10Q.0QQ. which is about 50T*e higher than the rate tor the Province. This, it will be recalled from the previous dis cussion of the effect of the "suspected" cases on the results, approaches but does not exceed the significant level. One further interesting observation from Table 16 is the rather marked increase in the total number of cases for the Province between 1950 and 1955. It is assumed that at least pan of this increase is due to im proved recognition and reporting of lung oncer during the interval. For this reason, the years 1954 and 1955 were thought to be more nearly representative of actual condi tions. Even so, it is quite likely that the general population is not studied for lung cancer with the same diligence with which TaSLE 16.--Comforusen of Cohort -jrilA Previntt of Quebec Lose Canmr Dootbi Anneal . finni 1190 1U1 1*92 109 194 1*99 Total >03.000 Frm<e CoToontal m*d (virtueiai oobutm un-oeo* 10* a t a 91st 949 749 m xa an}a astt an 1.04 194a I 1.(12 *rktnt SJ U the Proton flnrri. It Ku Orta tauB*4 *0 Btl* Ium oearOwthtef. lot ato v> rr- * Aspvetrmmu oiepOkPlellAt raucrwrwM pep-mum tot 1*91, M vbtvnimateO population ler 1*94 (lUppeft, Civ. tfo la Ot iffipnitl. (Number alive ta cohort as bdvuuitf at 1*91. Bream--Trap* 645 A|* Croup --4 O413M-rMM Tauit A. U. A. ARCHIVES OF INDUSTRIAL HEALTH TailC \7.--Luxf Concrr Deaths for the province ef Quebec* pQpwuiion TTT.fcO Stirt.l.JDwMMo 1337.000 fiunOcr ( Dotdf SIM Tu) Camera SmciOtU PrjSir* Tui Protaa Taul ProsrS IT IICDrO 3n13L 14)1 ' a 1 33I1I 3U 13) Ul M 'lIU Tsui CmiSM SnctoM PnaJary Toul Protaa Taul Ptarad I3T0 u% % 37 HI M 1U 30 US 337 VS3 Aw Oroue ||ti sty 4W M .................... 7. OTT/Uil.,.,......... .. ............... Duu Ksta per 100.000 ISM Twi Carnets Scvnrwd Pr:=ry TaaJ Prod Tool Prot I33II3.l3T3 i.r mi l.l 30.4 M3 141.31 133443 U-S 1.7 13.1 1.0 1133 Taul C<n*4 SoaaOM PrMt7 Total Praraa Taul ?ro*4 5-3 44L4.3b to 411134..3.13* it.6 13.S r.: 113 * Di* (ns etna tamieouj. t Cstmtu ia 9>ocl*IK>s aouiAal BT *99>r<9| ItsI pertaoutn lor to Jfeppon. Pit. 31 u Ptssprapnit. . ' |ue* (at suits is tea tool pjpuliiioa far ||M. u iittn this disease is looked for in the miners, and it seems probable that the mortality rates tor the Province may be low. This would appear to be substantiated by the fact that the reporting of cases in the cohort showed no such increase over the same period. Table 1? was compiled to show the an nual age-specific lung cancer rate of cases in which the death certinate merely read "cancer of the lung." as distinguished from those in which the diagnosis was confirmed by autopsy, surgery, or biopsy. The term "specified primary" refers to those cases in these two categories in which the tumor was specified as having originated in the lung. It will be noted that, of the total cases reported in 1953, a much higher percentage than in 1954 were specified as primary. The table also shows that a higher percentage of the total cases certified in 1955 were proved, again indicating increasing interest in this disease. A comparison has been made between the age-specific rates shown-in Table 17, and those for the cohort, shown in Table 8. An average of the 1954 and 1955 rates for the Province has been used, since the 1955 figure was higher and may have been ex ceptional. This comparison, summarized in Table 18, shows that the observed number oi deaths in our sample is not significantly greater than the expected number of deaths, based on the average of the 1954 and 1955 figures for the Province. It is true that, in the case oi the age group of 65 and over, the five deaths provide a figure which is almost significant at the 95$e level. How ever, it should be noted that this number includes one of the suspected but unproved cases previously referred to. Furthermore, it is rather likely that the rate for the general population is understated in this age group, ior the obvious reason that the exact cause of death in the very old is not Tailc 18.--Comparison of the Actual and Effected Number of Lung Cancer Dtaths-by Age Among Asbestos Miners ProniKa Taul SiwiWO Oreua 70~U *MM IM U-fe Usknaaii pa 105300 13 343 *7.1 M3 * Xa.ar Mlnm Irorrd D*4tu* Obaar*td Na. a< Daaibi Tre*0 T*u am 1,114 113 IU * t 1 - *0 tiumSTt s bAVd o th tTT-rrre! ttM UM tod t ..1133 MT-tOKtnc row* wc tn Pric ef acioout W4 Voi 17, June, 19S1 S'**/ LUXC CAXCER y.v ASBESTOS MIXERS Taole 19.--.4cr Distribution of Adult Males jor Taale 20 --Annttal Death Roles per ]00/X0 {' the Province of Quebec. 19iT* Cancer et im Luny 1.1 Coj-sLu ' Onun of Ywi M* Craue NuMr rn*nuit in Csnsri Act Ci^ap I9J1-IVJJ 1041-100 14JO-IWJ 33--4..................... aM .MM...................... ............ IM.9S2 13.0*4 l U 1* 10 AH-....................... 1U..4T w & - 1.110.490 its 100 lupport. 1AM. a matter of the same intensity o! interest as it is In younger persons. t'lVW 30-M 11-14 V44 . O-ul M-M il-AO C6-M n-u ;m:o M Aw AU Am o.: 0.0 5,ft 111 ,v: 1.2 P7 12.1 t2 u* 0J 1.0 0.9 4A 1.2 >.q 3.4 4.S 12 0 it: 19.9 Jt.2 rj n: u.; "2 HE* P*J u.-< rt. 2.: HJ 51.0 7.1 u.1 Table 18 also answers a question pre viously raised. It shows that the members * ~Mvru!>! tram tun; CMKtr in CjiwAi." l*Ji is 10J2. of the cohort have nor died from lung can cer at an age earlier than the general popu lation, and that such .an explanation cannot be offeree for the absence of lung cancer in 240 men with more than 40 years oi employment referred to on page 643. Before leaving this comparison of the Province with the miners, it should be shown that their age distributions art rea sonably the same. That this is the case can be observed from Table 19. It should be remembered that the miners retire and consequently, it can be expected that the oidest age group will be larger in the genera! population- The data presented in Table 20 indiote that the lung cancer rate generally decreases after age '0. There fore, we could expect the race for oil people over 65 to be smaller than the rate for the group between 65 and 75, which would apply to the oldest group of miners. It is felt that by using the whole adult male popula tion. we have developed rates for the gen eral population which are somewhat lower than if we had been able to exclude the people in the general population over 75. A comparison between the asbestos miners and the population of the Dominion as a whole was made, using statistical material from several sources. In one source. Phil lips " gave age- and sex-specific rates for Canada for three periods between 1931 and 1952. The rates for males are given in Table 20. These figures shew strikingly the increase in rates between 1931 and 1952, and this mcrease is particularly marked after age 50. confirming an observation previously made. ;o the enecc that until recently lung cancer h3S probably been underdiagnosed in the eider age groups in the general popu lation. To use these figures tor purposes of comparison, it is necessary to combine the rates tor certain age groups in order to conform to the age distributions used in this study. Since the exact populations in each age group for the years indicated is not known, this must be an approxim.av.cn. However, the rates would be somewhat as follows: A( Crup JO.n <SJ* SS-t* tSf Ri .S 2? ' Of 0*5 These rates are, in general, lower than those developed foe the totai (proved and suspected) cases of lung cancer among the asbestos miners. The only large difference, however, is in the age group oi 65 years anti over, and it is quite possible that the rate for this group may have increased for Canada between 1952 and 1954 as it did for the province of Quebec (Table 17). A further comparison has been made with an over-all rate obtained from the American Cancer Society for respiratory cancer deaths in Canada in 1953. This rate, ior males, is 20.S per 100.000, or 5 mere per 1CG.CCC. than Phillips' 1950-1952 rate, and compares with 25.3 pc. IC2.CCC I./. proved cases and 33.S per 100.000 for total cases among the 647 Aj./ A. M. A. ARCHIfES OF INDUSTRIAL HEALTH T.UK of Dfailt* unit Dtoth Rates lOOpW by Aae Grotlft for the Adult Afelc PofulatMn 0/ Ihf United Stain * Agt ClWP SO-M O-Jt MT Tstal Vapulatnn luiim kou.ux i.K0xaa M.tlO.OOO Cum J.V79 UM Mt4 lO Halt p*1100.000 i.% MJ M.< UJ r..i * tram -vital Stuoua 1 Uw CtM Statu." v*l 1 wxlllMl asbestos miners in this study. It is there* fore obvious that there are no important differences between the rates for asbestos miners and those for the general population of Quebec and the Dominion of Canada. Since it is probable that figures for the United Sates are more complete and, there fore. possibly more comparable to the data for the miners, age-specific rates were com puted iron*. "Vital Statistics of the United States,'' Volumes I and II. for 1952. These rates have been tabulated in Table 21. It is apparent that these rates compare favorably with those for the asbestos miners as shown in Table S. Still other rates for the United States were obtained from the American Cancer Society, and for males, these were 25.3 per 100.000 in 1953, and 2S.0 per 100.000 in 1955. They are not identical with the rate calculated from the figures of the office of Vital Statistics, but this is possibly because the American Can cer Society rates are for males of all ages. Nevertheless, they. too. compare favorably with the rates of 25 for 34 for total cases) obtaining among the asbestos miners. Turning for a moment to a comparison between the asbestos miners and persons who are exposed to asbestos in one form or another (as distinguished from the gen eral population groups just discused, who have no exposure) an interesting observa tion can be developed by deduction. Hueper ** has stated that there are about 35.00Q persons exposed in the United States, and we have found that the Canadian- mines employ about 8000. Elsewhere, it has been estimated that the workers in England who have exposure total between 3000 and 5000. With workers in Africa, Denmark, Nor way, and ether countries, at least 50.000 persons must be exposed throughout the world, and it can be assumed that this number has been fairly constant in the 20 years since 1935 when the first case ot asbestosis with lung cancer was reported. At least 1.000,000 man-years of exposure has thus been accumulated, and this figure can be divided by the approximately 150 cases of lung cancer with asbestosis re ported during the 20-year period. This gives a rate of 13 per 100,000, which is at least indicative that any lung cancer rate which can be calculated for workers ex posed to asbestos dust is not much greater than that for the unexposed population. Comparison Between Eight Counties Ad jacent to the Asbestos-Producing Areas and Eight Selected Czu>:t:cs --To compare iurg cancer mortality rates in the counties sur rounding the asbestos-producing areas with another group of counties in which no as bestos miners are likely to reside, the rates were computed on the basis of figures for the years 1930 through 1955. The e:em counties seiected for comparison were Argemeuil. Chateaugay. Monunagny, Portneui, Richlieu. Riviere-du-Loup. St. Hvacimhe. and Terrebonne, mainly because they represent a wide geographic distribu tion throughout the Province. The counties selected because of their proximity to the asbestos mines include Arthabaska, Beauce. Drummond. Fromenac. Megamic. Rich mond. Sherbrooke, and Wolfe. Table 22 shows the number of lung cancer deaths for the years 1950 through 1955 for each of these counties, and a mortality rate, based on the adult male population in 1952. To emphasize the comparison. Megamic County has been shown separately, as has the Province of Quebec and also the Prov ince with the eight "asbestos-producing" counties subtracted. Because of its unique lung cancer death rate, Montreal et Isle de Jesus has also.been listed in order to provide further comparison. It is apparent .'rum me table that the lung cancer death rate for the eight counties Vot. 17, ]u*. 19St /o LL'XG CAXCER IX ASBESTOS MIXERS Ta*LC 22.--Xtimber of i.imo Canter Dcetks end Rate ft- lOOWO Man-Ym'i Ceusiwi pre*iocl Qu<mc i.bicH Meatmlti ImM <*sus MJ* Uant C&ftftr C*iVM* AU)t Mil- . Po0UI9tlOA I IUI 1M3 S1 19 U tS n.ira *3.0& Uii-OJO 3 1 3 m | i 9 ] u i Ju i : 303 303 i.ico.ono i nr St 3* JH.W0 m 1U S3 * Ii UMMIM0 tfcinU M* Utfit oaotr4tt&iftccumc *<wr miX. rra <fei' *r. it:3-. immediately surrounding the asbestos-pro* during areas is'practically identical with that of eight counties selected tor comparison. While Megantic County has a rate nearly twice that of the combined eight selected counties, it is lowec than the rate for the Province, and considerably lower than the rate for Montreal. The figure for Montreal would certainly be higher except :cr the very low numbers of deaths reported tor 1950 ana 1951, and it would appear that in those years some error in reporting has undoubtedly been made. On the basis of the other years. 1950 and 1951 deaths would be expected to be about 200 greater. This would result in a rate of -10 per lOO.CGO. The only possible conclusion from this comparison is that there is no evidence that the persons who live and work in the coun ties surrounding and ad/acent to the as bestos-producing areas have any greater incidence of lung cancer than those who live elsewhere in the Province. Comment on All Recorded Lung Cancer Coies, Living and Dead, among the Asbeslos A/inerj.--Ahhougfi""*a simple enumera tion of all the known or suspected cases of cancer of the Sting in these areas has no particular value from a statistical point of view, it is of interest to summarire such eases for the record. There were nine deaths prior to the beginning of the time period covered by the study, including one in which the diagnosis was mediastinal lymphosar coma. During the period, covered by this inve<*ijptson, there were nine proved cases and three suspected cases in the cohort. Through 1956 and to date in 1957, there were eight deaths, six of which were merely suggestive of cancer of the long, ano u> eluded such diagnoses as mesiastinai' lymphosarcoma, mesotheiicea, cancer as- the leg with metastases to lung, abs*v of'ten-5, and cancer of the pancreas. Caw other, was* diagnosed on the basis oi zt-csiy oni.r. fitaddition. there are now livmg tece-cases iswhich the diagnostic evidence is strongly suggestive o: iur.c cancer. Ts-* is a vuii' of 35 cases o: all types, inducing 10 *suepected" but unproved cases, aad 4 that j-.-tt: stiil living. The remaining 39 cowKinsre the total of proved cases of cancel of sivr fcnq. among the asbestos miners since The proved cases averaged 59 years, oi age at death, and varied bervm AT and 6S years. Their working s?aic- covered! periods varying from a rnsnsrem of 14years co a maximum of 37 rears. Chiy three men had less than 25 years os' em ployment in the industry. Sma among those on whom such infonnaijos- is avail able had a weighted exposure porting- them in Category 111, and six worked in ax exposure represented by Category. 3. There were only 17 among these prosivd lung cancer cases in which- we have > formation regarding the presence of a-sbestosis. Asbestosis was prtsenc ip. nine, although it was. minimal in two. Two path ologists disagreed regarding rts peesenc* ia. another. At least seven of tfce- IS proved lung cancers, therefore, were no# accom panied by asbestosis. Summary and Conclusions Interest in tne question of wfietfte* (here may be an association between fang, cancer Brgvn--7rwa* 6*9 A. M. A. ARCHIVES OF INDUSTRIAL HEALTH -arid exposure to asocstos has Deen evident since the report in 1935 by Lynch and Smith of a case in which lung cancer and asbes- tosis were both present. As additional eases in which the two diseases coexisted were reported, a causal association appears to have been gradually accepted by many authors, although some workers considered the correlation to be inconclusive. The pres ent study was undertaken in an effort to de termine whether a causal relationship did. n 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 certain selected samples, such as cases coming to autopsy or death certificates in which asbestosis was mentioned, it was apparent that they could not fulfil! the re quirements of an epidemiological and sta tistical approach to the problem. The present study was. therefore, designed to meet the requirements of this method. After a preliminary survey to explore the availability'' of reiiabie information, 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 having at least five years of exposure and who weto in the industry in 1950. Data relative to their characteristics were collected and their status at the end of a six-year period of observation was de termined. In the case of those who had .died, an exhaustive search,oi death certif icates 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 Province ot Quebec and its various counties and for the Dominion of Canada, as well as the United States were calculated from statistics collected in the appropriate places. Comparisons of the rates obtained for asbestos workers and for the other popu lation groups were made according to ac cepted statistical methods. ' Records were obtained on 6091 persons who fulfilled the criteria of the cohort. It was not possible to trace 133 of these for the whole period, but 5771 of the remaining 5958 were found to be still living in 1955 or later. Of the 187 known dead, cancer of the lung was considered to have been reasonably proved in 9 and to be strongly suggested in 3. The members o: the cohort were studied with respect to age, length of employment, a weighted average 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. Thirry-lour per cent of the cohort were more than 45 years of age. and thirty per cent had beer, employed for longer than 20 years. Thirty per cent had a wetghted exposure which placed them in the category of highest ex posure. The mortality rate for lung cancer, as computed on the basis of nine "proved'' deaths among the cohort was 25.3 per 100. 000. When the three "suspected" cases were added, the ''total'' rate tor the cohort rose to 33.S. The imponance of the suspected but unproved cases in determining theserates has been reiterated because it is likely that such cases would not be included in the statistics for the general population and because they jnnuence the results so mark edly. According to the findings in this study, the mortality rate from lung cancer does not appear to increase with length of ex posure or with degree of exposure, a fact which presents strong evidence against the carcinogenicity of asbestos. Comparison of (he experience among the asbestos miners with that of various seg ments of the unexposed, comparable popu lation shows that the observed number of deaths among the miners is not significantly greater than the expected number. The rate for proved cases among the asbestos miners (25.3 per 100.000) compares well with the rate of 22.S per 100.000 for the rest of the Province. 20.2 100.000 for adult males throughout the Dominion of Canada. It also compares satisfactorily with rates 650 Vo!, IT, J9ff ' LL'SC CAXCSR /X ASBESTOS M/XRS of 172, 2S.3. 2nd 28.0 obtained from various sources for adult ntales in the United States. Finally, in this matter oi comparison, it would appear that the world-wide experience of persons exposed to asbestos dust is not worse with respect to lung cancer than that of the unexposed population. The counties surrounding the asbestosproducing areas, in which it is presumed most of the asbestos miners live, have al most identical mortality rates with those of eight counties widely scattered through the Province, and are lower than those tor the remainder of the Province, and much iower than the rate for Montreal. Since 1940 there have been 19 cases in which the diagnosis Qt primary eancer of the lung may be considered to have been proved. Approximately half of these cases were associated with asbestosis. All but one died in the recognized "cancer-age" and at least one-third had only the lightest ex posure (Category li to asbestos dust. On the basis of what are believed to be complete and reliable data, it seems fair to conclude - that the asbestos miners in the Province of Quebec do not have a signif icantly higher death rate from lung cancer than do comparable segments ot the general population. Furthermore, the death rate from lung cancer in the areas contiguous to the asbes tos operations is comparable to that in areas widely scattered throughout the Province of Quebec and is lower than in some urban ized areas within the Province. REFERENCES 1. Alascio Escobar. R.: Bronchial Carcinoma: Review oi 200 Cases. Internal. Coll Surgeons 26:375-379 (Sept.) 1956. 2. Allen. M. L.: Bronchiogenic Carcinoma As sociated with Pneumonoeoniosis: Report oi 2 Cases. J. Indust. Hyg. 16:346-347 (Nov.) 5934. 3. Carrier. P.: A Contribution to the Study of Asbestosis. Arch, mal profess. 10:559-595. W9. *. Anderson. C S, and Oible, J. H.: Silicosis and Cardnoma oi the Lung. J. Hyg. 38:185-204 (March) 1938. 5. Baider, E. W.: Asbestosis, Deutsche med. Wchnsdtr. 65:407^08 (March 17) 1939. b. llehiois. W.: Exptnnienv.il Asbestosis. Ssliwcu. Ztsehr. till*. Path. 14:275-297. t05l. 7,iBehrens. W.. Jr.: The Clinical Picture and P.nhol.rgj oi Asbestosis. Ztsclir Lmiallmcd. u. Berui'Wr.mkh. 45:120-140 (June IS) 1952. 3. Eerbltttgcr. W.: Increase ot Lung Cancer and Diseases Due io Dust Inhalation. Med. Klin. 27:1337.1342 iSept. il) 1931. 9. Bercnblum. I.: Irritation and Carcinogenesis. Areh. Path. 33-233-244 (Oct.) 1944. 10. Bonne: Asbestosis. Deutsche med. Wehnsciir. 62:92S-930 (June 5) 1936. 11. Bohme, A.: Results of Periodical Examina tions oi Workers in an Asbestos Factory. 3e::r. Silikosc Forseh. 11:34. 1951. 12. Bowies. O.: Asbestos-Milling. Marketing and Fabrication. Information Circular No. 6369. U. S. Department oi the Interior, bureau ot Mines. 1935. pp- 1-26. 13. Bresiow. L.; Hoaclin. L.: Rasmussen. C.. and Abrams. H. K.: Occupations and Cigarette Smoking as Factors in Lung Cancer. Am. .1. Pub. Hea;:h. -U iT'.-ISI i.-t;) 5954. 14 Bristol. L. J.: Roentgenoiogie Aspects ot Silicosis and Asbestosis. A. M. A. Arch, indust. Health 11:159-195 (March) 1955. 15. Cancer ot the Lung: An Evaluation oi the Problem. Proceedings oi the Scientific Section. Annual Meetmc. American Cancer Society. Ine.. Nov. 3-4. 1V53. New York. American Cancer Society. Inc.. 1956. 16. Cartier. P.: Asbestosis Cancer oi the Lung, in discussion on Smith, W. E.: Survey oi Some Current British and European Studies oi Occupa tional Tumor. Problems. A. M.A. Arch. IncuK. Hyg. 5 -262-263, 1952. 17. Cartier, P.: Some Clinical Observations oi Asbestosis in Mine and Mill Workers. A. M. A. Arch. Indust. Health 11:204-207 (Match) 19:5. 18. Clerens, }: Research into Pulmonary Asbes tosis in Belgium. Arch, beiges med. Sociaie S*:5*565 (Nov.) 1951. 19. Clynes: Asbestosis and Silicosis. Brit. M. J. 13*9. 1931. 20. Cofiin. G. I.; Duryee. H. C.; Maier. H. C; Pardee. H. E. B., and Wyrtter. E. L.: The Effects ot Tobacco Smoking. Panel Meeting. Bull. New York Acad. Med. 32:133-156 (Feb.) 1956. 21. Cohan. E. M.: Lung Cancer and Economic Status. Cancer 8:1126-1129 (Nov.-Dee.) 1955. 22 Cooke, W. E-: Pulmonary Asbestosis. Brit. M. J. 2:1024-1025 (Dec. 3) 1927. 23. Cureton. R. J. R.: Squamous Cell Carcinoma Occurring in Asbestosis of the Lung. Brit. J. Cancer 2:249-253 (Sept.) 194$. 24 * l.* `-'H-'eiderrr.an, M. A. and Greenhouse. S- W.: Some Statistical Considers- Brtttm--Troon /v A. Li. A. ARCHIVES OF INDUSTRIAL HEALTH lnj* in the Study -jt Cancer in Industry. Am. J. Pub. Health 44:1139-1166 (Sept.) 1954. 23, Davies. D. F.: Current Status of Lung Cancer Research: Some Pathogenetic Aspects, CA 6:169-174 (Sept.) 1956. 26. Desmeules. R.; Rousseau. L.; Giroux. M, and Sirois, A.: Asbestosis and Pulmonary Cancer, Semauie de. hop. Paris 23:1S20-1S23 (Aug. 7) 19*7. '' 27. Doll. R.: Bronchial Cardnonu: loodence and Aetiology (Milroy Lectures, abridged). Brit. M. J. 2:321-327 (Sepc 5); 355-390 (Sept. 12) 1933. - 28. Doll, R.: Mortality from Lung Cancer Among Asbestos Workers, Brit. J. Indust. bled. 12:81-86, 1955. 29. Donnelly, j.: Pulmonary Asbestosis, Am. J. Pub. Heahh 23:1275-1281 (Dec.) 1933. 30. Dont. K. F, and Cutler. S. J.: Morbidity from Cancer in the United States. Pub. Health Monograph No. 29. P. H. S. Publiation No. 418. U. S. Public Health Service. 1935. 121 pp. 31. Dom. H. F.: Cancer Morbidity Surveys: A Tool for Testing Theories oi Cancer Etiology. Am. .1. Pub. Health 45:615-621 (May) 1955. 32. Egbert. D. S,, and Geaser. A. J.: Pulmonary Asbestosis and Carcinoma: Report of a Case with Necropsy Findings, Ant Rev. Tuberc. 34:143-150 (July) 1936. 33. Elhnan. P.: Pulmonary Asbestosis: Its QinicaL Radiological, and Pathological Features and .Associated Risk of Tuberculosis Infection. J. Indust Hyg. 15:165-183 (July) 1933. 34. Ellman. P.: Pulmonary Asbestosis. Proe. Roy. Sot Med. 34:557 (July) 1941. 35. FciL A.: Pneumoconiosis in Asbestos Workers. Presse med. 39:1872-1874 (Det 19) 1931. 36. Fulton, W. B.; Dooley, A.; Matthews,- J. L. and Huuta. R. L.: Asbestosis: Part III. The Effects of Exposure to Dust Encountered is Asbestos Fabricating Plants on the Health of a Group of Workers, Special Bulletin No. 42, Pennsylvaraa Departmen of Labor and Industry. Bureau of Indust. Standards, Sept. 20, 1935. 37. Gardner, L. U-, and Cummings. D. E.: Studies on Experimental Pneumoconiosis: Inltala- tion of Asbestos Dust; Its Effect upon Primary Tuberculous Infection, J. Indust Hyg. 13:65-81 (Feb ); 97 (March) 1931. . 38. Gilliam. A. G.: Mortality Trends in Lung Cancer. Cweer 8:1130-1136 (Nov.-Dee.) 1935. 39. GiUiam. A. G.: Mortality Attributed to Lung Cancer m the Large Gties of the United States m 1948 and 1949, J. Nat Cancer Inst !5:130?-13tZ 1953. 40. Gkiync. S. R.: Two Cases of Souaiuous Carcinoma of else Lung Occurring in Asbestosis. Tubercle 17:5-10 (Oct) 1935. 4|. Gloyne. S. iL: Pneumoconiosis: A Histo logical Survey ut Necropsy Material in 1205 Cases. Lancet 1:810-814 (Apr:! 14) 1951. 42. Gloyne. 5. R.: A Case of Oat-Cell Car cinoma of the Lung Occurring in Asbestosis. Tubereie 18:100-101 (Dee.) 1936. 43. Gloyne. S. R, and Merewether. E. R. A.: Asbestos, Occupauon and Health, Supplement to Encyclopedia on Occupadon and Health, Geneva. International Labor Office, 1938 44. Goidblatt M. W,, and Goidbiatt J.: In dustrial Carcinogenesis and Toxicology, in In dustrial Medicine and Hygiene, edited by E. R. A. Merewether. London. London. Butterworth tc Co.. Ltd. 1956. VoL 3. pp. 185-188 45. Haenstei. W. M.: Epidemiological Tests of Theones on Lung Cancer Etiology. Pub. Health Rep. 71:163-172 (Feb.) 1956. 46. Hammond E C.: Lung Cancer and Cornmen inhalants. Cancer 7:1100-1108 (Nov.) 195*. 47. Hammond E. C.: Etiology of Bronchiogenic Carsr.Kns. CA 6:15^163 (Sept) 1956 48. Kolleb. H. B~ and Angrist, A.: Broncciogeme Carcinoma in Association with Pulmonary Asbestosis: Report oi 2 Cases. Am. J. Path. 18: 123-135 (Jan.) 1941 49. Homburger, F.: The Co-Incidence of Primary Carcinoma of Lungs and Pulmonary Asbestosis: Analysts of Literature and Report of 2 Cases. Am. J. Path. 19:797-807 (Sept) 1943. 50. Horn, D.: Is Lung Cancer on the Increase? Evaluation of Present Day Evidence: Cancer of the Lung, Proceedings of the Scientific Section, Annual Meeting, American Cancer Society, Inc. Nos*. 3-4. 1953. 51. Homig. F.: Clinical Considerations on the Question of Industrial Canecr of Asbestos Work ers, Ztsehr. Krebsiorsch. 47:281-287, 1938. 52. Kueper, W. C: Cancer in Its Relation to Occupation and Environment, Bull. Arc Soc Control Cancer 2S:63-69 (June) 1943. 53. Hueper. W. C: Significance of Industrial Cancer in the Problem of Cancer, Oecup. bled 2:190-200 (Sept) 1946. - 54. Hueper, W. C: Environmental and Occupa tional Cancer, Public Health Sendee. Supp. 209, U. S. Public Health Service. 1949. 55. Hueper. W.-G: A Methodology for Environ mental and Occupational Cancer Surveys. Public Health Monograph No. I, P. H. S. Publication No. 12. U. S. Public Health Service, 1950. 56. Hueper, W. C: Environmental Lung Cancer. Indust. Med 20:49-62 (Feb.) 19S1. 57. Hueper. W. C: Occupational and Envircn- mental Pulmonary Cancers with Special Reference. to ...... r.iKccdings, 7th Saranac Symposium no Pneumoconiosis. 1952. S8 Hueper. W. C: A Quest into the Environ mental Causes of Cancer of tl* Lung. Pub. 652 Vol. 17, /w. 195! LUNG CANCER IN ASBESTOS MINERS neaun Mwwgraph No. 36. P. H. S. Publication No. 432. U. S. Public Health Service. 1933. 39. Hueper. W. C: Environmental Causes of Cjncer or the Lung other than Tobacco Smoke. Dis. Chest. 30:141-153 (Aug.) 1936. 60. Isscibacher. K. J.; Klaus. H.. and Hardy, H. L.: Asbestosis and Bronchogenic Carcinoma: Report of One Autopsied Case and Review oi Available Literature, Am. J. Med. 15 ;721 -732 (Nov.) 1953. 61. Kennaway. E. L. acd Kemaway. N. M.: A Study of the Incidence of Cancer of the Lung and Larynx, j. Hyg. 36:236-267 (June) 1936. 62. Kennaway. . L, and Kennaway. N. M.: Studies of Incidence of Cancer of the Lung and Larynx. BriL J. Cancer 5:153-158 (June) 1951. 63. Klou. M. 0.*' Association oi Sitttcsis and Carcinoma of the Lung, Am. J. Cancer 35:38-49 (Jan.) 1939. . 64. Lanza, A. J.; McConnell. W. and Fennel. J. W.: The Ejects of the Inhalation o: Asbestos Dust cm the Lungs of Asbestos Workers: Pre liminary Study, Pub. Heaith Rep. 50:1-12 (Jan. 4) 1933. 65. Lanza. A. editor: Silicosis and Asbestosis. New York and London. Oxiord University Press. 1938. 66. Lew. E. A.; Use of Life Insurance Com pany Records lor Cancer Studies. A. M. A. Arch. Indust. Hyg 5:198-203 (March) 1932. 67. Linabach. A. J, and Wedlcr. H. VV.: Occu pational Cancer among Asbestos Workers. Arch, path. Anat. 307:387-409. 1941. 68. Lynch. K. M., and Smith. W. A,: Pul monary Asbesiosis: Carcinoma of Lung in Asbesto-Silicosis. Am. J. Cancer 24:56-64 (May) 1935. 69. Lynch, K. SL, and Smith, W. A.: Pul monary Asbesiosis: A Report of Bronchial Car cinoma and Epithelial Metaplasia, Am. J. Cancer 36:567-573 (Aug.) 1939. 70. Lynch. K. M, and Cannon. W. M-: Asbestosis: Analysis.of 40 Necxopsied Cases. Dis. Chest 14:874-889 (Nov.-Dee.) 1948. 71. McPhecters, S. B.: A Survey of a Group of Employees Exposed to Asbestos Dust. J. Indust Hyg. 18:229-239 (April) 1936. 72. Merewether, E. R. A.: The Occurrence of Pulmonary Fibrosis and Other Pulmonary Affec tions in Asbestos Workers, J. Indust. Hyg. 12: 198 (May): 239 (June) 1930. 75. Merewether, . R- A.: Annual Reports of 'ihe Chief Inspector nf Factories. London. His Majesty's Stationery Office. 1947. 76. Merewether. E. R. A., editor: industrial Medicine and Hygiene. London. Butte'wonh & Co.. Ltd.. 1936, Vol. J. 77. Xordmann. M.: The Industrial Cancer oi Workers in Asbestos. Ztsehr. Krcbsioreh. 47:2S8302. 1938. 78. Noramann. M.. and Sorge. A.: Pulmonary Cancer Produced by Asbestos Dust in Experi mental Animals. Ztsehr. Krebsforch. 51:168-182. 1941. 79. Phillips. A. J.: Mortality from Cancer of the Lung in Canada (1931-1932). Canad M. A. J. 71:242-244 (Sept.) 1954. 80. Saupe. E-: Further Contributions to the Roentgenological Diagnosis o( Asbesiosis. Arch. Gewerbepath. u. Gewerbehyg. 9:39l-M36. 1939. 81. Smith. K. \V.; Pulmonary Disability in Asbestos Workers. A. M. A. Arch. Indus;. Health 12:198-203 (Aug) 19S5. 82. Smith. L W.: Pneumoconiosis ami Luug Cancer with Special Reference to Silicons anii Asbesiosis. Compens. Med 2:3-10 (Nov.) 19-9. S3. Smith. W. E.: Surrey of Some Current British and European Studies oi Occupational Tumor Problems: Part III. Asbestos. A. M. A. Arch, indust. Hyg. 5:242-263 {March) 19:2. 84. :cil. R.; Sass. R.. and Angrssi. A.: Asbestosis Associated with Bronchogenic Car cinoma. A.M. A. Arch. Int. Med. 88:831-834 (Dec.) 19SI. 83. Teleky. L.: Occupational Lung Cancer. Acta Union internal, contre Canter 3:253-273. 1933; also. Ztmralbl. Gewerbehyg. 27:33. 19*0. 86. Vorwald A. J.; Durkan. T. M., and Pratt. P. C: Experimental Studies of Asbestosis. A.M.A. Arch. Indust. Hyg. 3:1-43 (Jan.) 1931. 87. Wedler, H. W.: Asbestosis and Lung Cancer. Deutsche med Wehnsehr. 69:5*5-376 (Aug. 6) 1943. 85. W'egeiius. C: Qianges in the Lungs in 126 Cases oi Asbestosis Observed in Finland Acta radiol. 28:139-152, 1947. . 89. Werber, M.: Pulmonary Asbestosis Asso ciated with Carcinoma. Zentrslbl. Arbeitsmed u. Arhelusthutt. 2.179-lSQ (Nov.) 1952. 90. W'ood W. B., and Gioync. S. R.: Pulmonary Asbestosis Complicated by Pulmonary Tubercu losis. Lancet 2:954-956 (Oct 31) 1931. 73. Merewether. E. R_ A^ and Price, C W.; Report on Effects of Asbestos Dust on the Lungs and Dust Suppression in the Asbestos Industry, London. His Majesty's Stationery Office, 1930. 74. Merewether, E. R- A.: A Memorandum on Asbesiosis. Tubercle 15:109; (Dee.) 1933; 15: 152 (Jan.) 1934. 91. Wyers. H.: Asbestosis, Postgrad. Med 25: 631-636 (Dee.) 1949. 92. Wyntler, E. L- and Graham. E. A.: Etinlugic Factors in Brondiiogcnic Carcinrma Mini neicrcnce to Industrial Exposures; Report of 857 Proved Cases, A.M.A, Ardc lndusb Hyg. 421-235 (Sept.) 1951. Brow*--Truon Priattl fstlilM m Ikr V-itti 4ul *f 4<wn<4 5SJ itnacs, y^rj US?J.TC?.T ACC IL'ICH NO. I&-57-03 October 27, 1?5? around 12 oocr. AU7CPST: Performed on the tfa day at 7 ?.H. in Kanrills, J. KLzhei Janij, h. 2. fa. /<' v/b A