Document wr2RxkGNmbgw96qoqBXymKNvD

FILE NAME Industrial Hygiene Foundation IHF DATE 1958 DOC IHF042 DOCUMENT DESCRIPTION Journal Article - An Epidemiological Study of Lung Cancer in Asbestos Miners An Epidemiological Study of ~~ Lung Cancer in Asbestos Miners af a* e DANIEL C. BRAUN M.D. and T. DAVID TRUAN M.A. Pittsburgh Ever 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 environment of man The approach used by some workers has been to suspect one or several substances and then set about in an intensive 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 14.1 of asbestosis cases examined by him In 1941 Nordmann and Sorge .. claimed to have produced lung cancer in mice which they exposed to asbestos dust * search for lung cancer among persons who have had any exposure to those materials In this connection Smith 82 writes The Since 1951 additional cases of cancer of the lung coexisting with asbestosis have been reported and according to Hueper ' tendency of authors reporting the coincidental occurrence of primary lung cancer with silicosis or with any other theoretical about 100 such cases had been reported up . ' to 1955. As result an association between ' the two diseases appears to have been ac- etiologic conditions has been to emphasize cepted by many authors and several writers , the percentage relationship in extremely . were using the term asbestosis cancer of - small series of cases with control cases the lung Werber in 1952 stated cate- 2. which are not in any way comparable gorically that in % to % of cases of y It would seem inevitable that asbestos asbestosis after a latent period of about should come under scrutiny in this manner 1to 20 years carcinoma becomes estab- _ because prolonged exposure to this material is known to cause a specific type of pneu- lished in the lung On the other hand not all authors ac- moconiosis and because persons who show this form of pneumoconiosis often come to cepted this alleged association without reservation 80 Saupe in 1939 reported that autopsy and provide a ready source of he had discovered no cases of lung cancer material for study It was in this way that among 620 cases of asbestosis which he reports of the simultaneous occurrence of had examined and in 1942 Holleb and lung cancer and asbestosis began to accu- 48 Angrist expressed the opinion that the mulate after the report of a case by Lynch number of cases of asbestosis with lung and Smith68 in 1935. Within the next 10 years about 15 additional cases were re- ported and in 1954 Merewether 76 reviewed all deaths from asbestosis recorded in Eng- cancer was too small for statistical evalua- tion In 1947 88 Wegelius reported 126 radiologically diagnosed cases of asbestosis among 476 workers in Finland and found land since March 1924. Lung cancer oc- no cases of lung cancer in this group curred in 16 of these cases Gloyne Goldblatt and Goldblatt in their section of Accepted for publication Jan. 20 1958 This study was made possible through a grant from the Quebec Asbestos Mining Association Medical Director Dr. Braun and Statistical Consultant Mr. Truan Industrial Hygiene Foundation Merewether's latest book state But at no stage in all these impressive researches was any clue obtained which might have offered any support to the possibility that asbestos could act as a carcinogen There 634 also frequently referred to connection between asbes- of the lung reported in - of the lung was present| Destosis cases examined by Nordmann and Sorge 78 produced lung cancer in exposed to asbestos dust Iditional cases of cancer of ~ ting with asbestosis have nd according to Hueper | _ cases had been reported up sult an association between appears to have been ac- ' authors and several writers 7 erm asbestosis cancer of -<' er in 1952 stated cate- % to 17 of cases of * a latent period of about | ~ ' carcinoma becomes estab- hand not all authors ac- eged association without 8080 in 1939 reported that d no cases of lung cancer s of asbestosis which he and in 1942 Holleb and ssed the opinion that the s of asbestosis with lung small for statistical evalua- 88 Wegelius reported 126 agnosed cases of asbestosis cers in Finland and found ng cancer in this group oldblatt in their section of test book state But at these impressive researches btained which might have port to the possibility that | .ct as a carcinogen There LUNG CANCER IN ASBESTOS MINERS is no reliable criterion by which one can anticipate carcinogenicity and as is well known relatively minute changes in the structure of a chemical carcinogen are suffi- scheduled areas by which is meant those areas where processes are carried on which were scheduled under the Asbestos Industry Regulations of 1931 as being cient to diminish or eliminate carcinogenic dusty There is furthermore a complete lack 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 advance the theory that until some more experimental evidence of direct carcinogenesis by asbestos or a de- composition product of it can be obtained of definition of terms as used in the published literature For example the term asbestosis as used may refer to changes observable only by microscopic examination of the lung tissue or it may mean a radiologically detectable condition Most of the published reports obviously included women among their cases but some of them do not give the number or asbestos might be considered as a car- cinogen which only induces a further de- velopment of a preneoplastic 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 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 having done so What has happened is that succeeding authors have drawn conclu sions and generalized beyond the scope of the works which they quote Nowhere for 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 of persons who also had asbestosis imply that this incidence applies to asbestos work- proportion of women involved in the study There is also a lack of uniformity as to what dealt type of exposure most studies have with Of 99 cases enumerated by 58 Hueper in 1955 only 10 appear to have originated in the United States and 7 in Canada Some of the earlier reports ap- parently 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 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 With this understanding of the limita- tions of the existing literature with respect to epidemiological generalization it may be of value to consider in somewhat more de- tail some representative earlier publications a few of which were referred to briefly ers generally unable to find We have any study likewise been which actually calculated the incidence of lung cancer among a population of persons who had asbestosis and not just those who came to autopsy With the exception of a paper by Doll none of those reviewed gave any lata on exposure and dust concentrations and even Doll's paper merely mentions above One of the most detailed studies and one which deserves the most serious considera- tion is that reported by Doll 28 in 1955 This study reviews causes of death among asbestos workers based on coroners records It also attempts to estimate the risk by studying records of men who worked for at least 20 years in exposed situations 635 Truan HEALTH A. M. A. ARCHIVES OF INDUSTRIAL . 2 Doll concluded that lung cancer was a spe- lung cancer in other forms of pneumoconio ed cific industrial hazard of certain asbestos sis was 6.7 and in 169 cases 0 which workers and that after 20 years of expo- proved not to have any type of pneumo- sure the risk is 10 times as great as for coniosis it was 8.3 Gloyne considered the general population This article is important for several rea- the mortality of the asbestos workers to be disturbing First of all it is obvious sons in addition to the definite conclusions at which it arrives For example it begins that the paper does not deal with the mor- tality of asbestos workers and secondly by stating that in view of the infrequency it must be borne in mind that all of Dr. of asbestosis this large number of cases Gloyne's cases were submitted to him for 61 cases of lung cancer does not prove lung suggests cancer is an study because the findings were unusual for uncomplicated pneumoconiosis It can occupational hazard of asbestos workers Neither this article nor any previous one which we have examined presents any fig- including reasonably be assumed that cases those of asbestosis in which the findings were not considered unusual were not sent ures to prove that asbestosis is an infre- to Dr. Gloyne for examination As a mat quent occurrence Estimates of the number of persons potentially exposed to asbestos dust in the United States alone vary from ter of fact in the same paragraph in which he expresses concern over the incidence " rate in asbestosis Dr. Gloyne himself 10,000 to 35,000 and the incidence of asbestosis of any degree might be higher than points out that the rate for lung cancer based on necropsies at the London Chest Doll imagines Hospital was 21.3 while the figures of This study like so many others involves the Registrar showed only 2.4 autopsy records The number of persons involved in the statistical analysis is only 113 representing only 1,042.25 years of life It is also true that in selecting men who had been employed for at least 20 He thus recognized that autopsies on a cerrep- tain selected group of cases were not resentative of the general population It would seem then that notwithstanding the value of Dr. Gloyne's work its importance years the study automatically excluded as an index of the prevalence of lung can- those who died from other causes after cer in asbestotics has been misinterpreted shorter employment by some who have quoted him All that it Another reason why this publication is of importance is a statement which it con- tains to the effect that the strongest evi- dence that it lung cancer may be a hazard in asbestos workers has been produced by Merewether and by Gloyne In 1951 Gloyne presented of 1205 autopsies on persons a review 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 occurred 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- cosis and 6.9 of these also showed pri- mary cancer of the lung The incidence of really shows is the fact that in a group of 121 cases selected for special study primarily because they seemed abnormal by preliminary examination 17 or 14.1 had lung cancer Merewether 75 in 1947. in the report of the Chief Inspector of Factories reviewed all cases reported 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 cases re- ported 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 asbestotics who did not die of their asbestosis or in whose 636 Iul 17 June 1958 INDUSTRIAL HEALTH L3 UNG CANCER IN ASBESTOS MINERS which other forms of pneumoconio . and in 169 cases ) have any type of pneumo- as 8.3 Gloyne considered of the asbestos workers to First of all it is obvious does not deal with the mor ; death certificate it was not mentioned may have been missed The import of this % is enhanced by the simultaneous statement that the incidence of lung cancer in autopsies of the general population is only % The danger of attempting to compare a rate found in 344 cases with the rate for stos workers and secondly the general population without respect to Dr. me in mind that all of occupation and many other variables for age were submitted to him such as smoking habits is obvious 68 the findings were unusual Lynch who with Smith had reported ated pneumoconiosis It can the first case in 1935 reported 4 cases of assumed that cases including including carcinoma of the lung in a series of 49 tosis in which the ' findings autopsies on workers in an asbestos manu- dered unusual were not sent facturing plant who were shown to have for examination As a mat demonstrable deposits of asbestos in the the same paragraph in which lungs This of course is not necessarily concern over the incidence identical with the disease asbestosis Lynch tosis Dr. Gloyne himself himself points out that although this is an : the rate for lung cancer incidence of 8.2 both figures are too psies at the London Chest small for very serious statistical types of 21.3 while the figures of calculation Nevertheless later writers General showed only 2.4 have used this paper to strengthen the case ized that autopsies on a cer- for an association of carcinoma of the lung rep- oup of cases were not with asbestosis It is also of interest that the general population It 63 n that notwithstanding the oyne's work its F importcaann-ce> the prevalence of lung Klotz found only the same number of cases of lung cancer in a series nearly 10 times as large i e 4 in 478 cases of asbestosis s has been misinterpreted . it ve quoted him All that _ the fact that in a group of ed for special study pri- they seemed abnormal by ination 17 or 14.1 had Behrens as cited by Merewether estimated that of 309 cases of asbestosis in the literature 44 showed associated cancer of the giving an incidence of 14.2 This is an illustration of generalizing an incidence obtained in a group of cases in 1947 in the report of or of Factories reviewed : between 1924 and 1946 is was the cause of death ondition This work was include all such cases re- mber 1954 by which time aths including 205 males which were undoubtedly reported only because some of them showed lung cancer to possibly hundreds of asbestotics whose cases were never reported The same applies 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 Among them were 55 ancer of the lung 41 in males It is quite possible er of asbestotics who did asbestosis or in whose not justify generalizations with regard to mortality rates Perhaps no one has written so exten- sively on the subject as has Hueper In 1955 he reviewed the 58 cases reported Vol 17 June 1958 Truan prior to that date and enumerated a total of 99. Eleven of these were those dis- cussed by Doll 28 and may have been cases covered by other authors Eight were dis- covered by Kennaway and 82 Kennaway in an analysis of death certificates and unless Merewether's study was incomplete these cases should have been included in his re- port Of the remaining 80 it is quite possible that the 31 contributed by Merewether and the 17 by Gloyne contain some duplica- tion with 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 thought to be pertinent concerning the comparative frequency of lung cancer in different population groups has been developed from the analysis of clinical material particularly surgical and autopsy records supplemented to some extent by the reported impressions of various clinicians 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 tommunicable 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 defined population group 2 available 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 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 asbestos workers it is necessary for a study to in- clude living persons as well as the dead 637 j A. M. A. ARCHIVES OF INDUSTRIAL HEALTH Limiting the investigation to cases coming to autopsy as has been frequently done 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 low 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 studied to provide meaningful results be found in another group of the same size information but representative of the general population It is true that investigation of cases from such a sample can furnish valuable for research but the use of this information in drawing generalizations is necessarily restricted It 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 occur- study of cases of cancer of the lung ring in a group of autopsies can lead to a . proper inference concerning the frequency of lung cancer among cases coming to s. autopsy but only to such cases For in- formation from such a study be pro- inh 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- Recognizing the difficulty of obtaining such large samples most earlier writers gerous and likely to be false There is some danger that the * figures deviated from the epidemiological method reported by some authors may be miscon- ^' and sought to circumvent the requirement of observing well persons by 1 compar- strued as applying to asbestos workers or even asbestos miners when in fact the | ing the relative frequency of cancer in vari- authors in question do not make this gen- * ee ous sites 2 comparing the relative eralization nor can the generalization be . Ue a frequency of cancer in a group of hospital- ized patients 3 comparing the relative made for the reasons stated Close study of - the reports reveals that the percentages : frequency of cancer in a group of cases cited relate only to the group of autopsies coming to autopsy covered by the particular investigation Attempting to compare two population groups looking only at the relative fre- quency of cancer in various body sites may result in finding a higher percentage relative frequency in one of the groups when in fact the mortality rate of cancer of a particular organ is exactly the same in both groups This is very clearly demonstrated in the excellent article by Dorn.30 The mortality rate from a particular cause is 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 The present study in contrast to the earlier works has been planned to utilize the epidemiological method A defined group of asbestos miners has been estab- lished in such a way that it constitutes a good sample of the whole population of asbestos miners in Quebec Data for all members of this group have been collected and analyzed Those concerning lung can- cer have received most careful considera- tion Details of the methods employed will be set forth later but the type of approach is considered to permit of fair comparisons and valid generalizations a larger group and that in dealing with such samples the observer may easily find more cases of a given disease than would Collection and Analysis of Data A preliminary survey of potential sources of information in February 1956 involved 638 I'ol 17. June 1958 INDUSTRIAL HEALTH LUNG CANCER IN ASBESTOS MINERS her group of the same size e of the general population Investigation of cases from can furnish information earch but the use of this drawing generalizations is icted It is the obligation stigator and of those who make proper comparisons ly those conclusions which istified A good statistical f cancer of the lung occurof autopsies can lead to a concerning the frequency among cases coming to y to such cases For in- : such a study be pro%-: rger group it is necessary ca 3 represent a good ~ sample oup To assume that such = y particular series is dan- | to be false ae : danger that the figures ^ authors may be miscon- > g to asbestos workers | or on do not make this gen- ' be can the generalization =: ' ons stated Close study of als that the percentages : to the group of autopsies ' articular investigation * tudy in contrast to the 5 been planned to utilize .1 method A defined 5 miners has been estab- way that it constitutes a the whole population of in Quebec Data for all group have been collected ose concerning lung can- most careful considera- e methods employed will but the type of approach ermit of fair comparisons zations 1 Analysis of Data arvey of potential sources February 1956 involved Vol 17. June 1958 discussions with the physicians in charge of the asbestos companies programs and with clinicians pathologists representatives of City and Provincial health departments and of the Canadian Cancer Society and other interested persons It was found that morbidity data although somewhat limited were available from such sources as the hospitals in Montreal and Quebec City and the 13 cancer detection centers in the Prov- ince However because of the high mor- tality in lung cancer it seemed advisable to depend upon data relating to deaths These we found to be obtainable at the vital statistics department of the Ministry of Health in Quebec City From the preliminary survey it was apparent that extensive and detailed information could be gathered with respect to both the persons employed in the asbestos mining industry and the mortality figures for the general population Following this exploratory survey the initial effort was directed to the collection of data relating to all workers who had been processed through the clinic at Thetford Mines since its inception in 1947 and similar information regarding all workers 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 information it was possible to formulate a cohort which could be well lefined should be representative of the whole group and could be followed for a definite period of time All of the available experience indicates that the development of asbestosis in less than five years of ex- posure must be somewhat rare Accord- ingly the cohort was defined as including every miner who had a total exposure of five 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 cohort was then followed by means of the annual physical examination through records through a year interval 1950 through 1955. All data regarding this group were then tabulated in order to determine the characteristics of the cohort For those who survived the entire period reference was made to the physical examination results and ray findings at the end of the period Those who had died were tabulated sepa- rately and corroborated certificates the cause of death by examination of the A further search was was death made concerning those in the original cohort who remained unaccounted for when the living and the known dead had been tabulated They represent men who had left employment through retirement or resignation Eventually all but a small number of these were accounted for as either living or dead and in the latter event the cause of death was substantiated in a similar manner and the results added to the original list of deaths Death certificates for the Province of Quebec for the years 1952 to 1955 inclusive were reviewed in the department of vital statistics of the Provincial Health Ministry together with statistical sum- maries of the causes of deaths in the Prov- ince by counties All cases in which death was certified as having been due to pri- mary cancer of the lung were examined for such information as place of residence occupation date of death hospital in which death occurred and whether or not an autopsy was performed Cases in lung cancer was given as a cause of but in which it was not specified which death as to whether the cancer originated in the lung were also reviewed in an effort to include all instances of primary carcinoma of the lung in the study The statistics for the Province of Quebec relate to population total deaths from all causes total deaths from cancer of all types and deaths from lung cancer These were collected and tabulated by counties and by sex for the years 1950 to 1955. inclusive Truan 639 M. A. ARCHIVES OF INDUSTRIAL HEALTH From them death rates for the general population of Quebec and of individual counties were calculated for specific years and analyzed by cause In addition to this analysis of deaths occurring in the cohort and during the years under observation every known death from cancer of the lung as well as every case Practically all employees of one company are covered by a group policy of life insurance 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 diagnosed but still living has been tabulated and analyzed They will be discussed separ- ately from those includedin the population mortality and interval under study A comparison of lung cancer mortality in the asbestos ee counties has been producing far made with that in counties which are removed from the asbestos mines and in small number As an 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 under the policy and particular notice was taken of the claims in which the proof of death was based on cancer of the lung which presumably no asbestos miners live compari- Finally in order to broaden the Fi son of death rates in different population groups the rates have been collected for : Canada generally and for the United States " according to the most unpublished material recent published " and = PeeAFh.ee Deaths from lung cancer among asbestos Results and Interpretation miners were thus determined from the clinical records in the medical 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 AP The cohort which was constructed accord- - ing to the criteria describedin the preceding S~ s section has been considered individually and 2 compared with the general population ~. Description of the cohort will be presented here as a preface to the results of the study - Original Cohort Lost Persons Deducted 6,091 133 which primary cancer of the lung is considered to have been proved as the cause of Final Cohort Living in 1955 Dead by 1955 working and retired 5,958 5,771 187 death A few cases in which lung cancer is strongly suspected but not proved as the cause of death were considered separately Mortality rates have been calculated using both the proved and the total of proved Cancer of lung Questionable cancer of lung Other causes Unknown causes Smokers Nonsmokers Unknown 9 3 169 6 4,673 1.265 20 and suspected cases during the years under observation Comparisons were then made between the death rates from the same Tables 1 2 3 and 4 present age number of years of employment weighted average exposure and smoking habits of the cohort cause among specific segments of unexposed persons All lung cancer deaths both suspected and proved were carefully ana- A comparison of the exposure to asbestos dust is presented in Table 3. All members of the cohort were placed in one of three lyzed to determine possible relationship or correlations between the development of categories representing increasing degrees of exposure based on a weighted average lung cancer and any factor known from the of the years spent at various levels of clinical records such as family history of dustiness The degree of dustiness for each cancer personal history of heavy smoking job category was determined after consulta- coexistence of asbestosis or exposure to tion with persons familiar with the environ- asbestos ment and conditions in the various work 640 Vol 17. June 1958 OF INDUSTRIAL HEALTH > this analysis of deaths occohort and during the years on every known death from ung as well as every case till living has been tabulated hey will be discussed separe included in the population al under study 1 of lung cancer mortality producing counties has been in counties which are far the asbestos mines and in ly no asbestos miners live der to broaden the compari- ites in different population es have been collected for , and for the United States most recent published and LUNG LUNG CANCER IN ASBESTOS MINERS TABLE Number and Percentage Distribution by Age Age + Number 3,901 1,124 615 315 3 5,958 41 Per Cent 820 820 820 820 . 18 18 Less than 0.5 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. TABLE Number and Percentage Distribution by Exposure Category TABLE Number and Percentage Distribution by Length of Employment Length of Employment Number 1.795 2,398 922 603 185 55 5,958 18 Per Cent W5588 W5588 W5588 W5588 W5588 - 81 100 ually smoking more than five cigarettes per day Persons who smoke pipes or cigars exclusively were not considered to be smok- ers for the purpose of this study Table 5 presents the year ex- perience of the cohort and indicates the TABLE Number and Percentage Distribution by Smoking Habits and Interpretation re a. ich was constructed accord-of a described in the preceding considered individually and the general population he cohort will be presented : to the results of the study * 6,091 d 133 ng and retired cer of lung 3 4,673 1,265 20 and + present age number loyment weighted average oking habits of the cohort of the exposure to asbestos in Table 3. All members re placed in one of three senting increasing degrees ed on a weighted average ent at various levels of gree of dustiness for each determined after consultafamiliar with the environons in the various work Vol 17 June 1958 Number 2,031 2,150 1,772 5 5,958 2.0 Per Cent 1.885 1.885 1.885 1.885 1.885 Habits Number 4,673 1,265 20 Totals 5,958 Less than 0.5 Per Cent 22 22 ' 18 Less than 0.5 The fourth variable smoking habits was . similarly tabulated and is shown in Table + This was included because the informa- tion was available and because smoking was regarded as one of the variables which besides the environment could 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 causes In general a case was considered to be proved as one of primary cancer of the lung when the records showed that the diagnosis had been supported by an autopsy or surgical resection of the lung with microscopic examination of the removed tissue In one case so considered however diagnosis was confirmed by bron- TABLE Year Experience of Cohort and Death Rates per 100,000 Man Years of Risk Cause of Death Year Year No. Alive At Beginning of Year Proved Primary Ca. of Lung Suspected Primary Ca. of Lung 5,958 -202-310 20 10 10 5,942 -202-310 20 10 10 5,922 -202-310 20 10 10 -202-310 201010 5,885 -202-310 20010010 5,848 5.810 -202-310 201010 Totals wenecerensseeeecee . -202-310 20 10 10 35,271.5 " Proved " rate per 100,000 years of risk-35,271.5 25.5 12 " " Total rate per 100,000 years of risk 35,271.3 = 34.0 Other Causes 21633818 21633818 21633818 21633818 21633818 21633818 21633818 Unknown 2 0 4010 2 0 4010 22004010 2 0 4010 2 0 4010 2 0 4010 2 0 4010 Years of Risk 5,950 5,932 5.903.5 5,866.5 5.829 5,790.5 35.271.5 641 Braun No. Case No. 12340 12340 12340 12340 12340 10 = 00 ( Age 833275858 833275858 833275858 833275858 833275858 833275858 833275858 833275858 833275858 M. A. ARCHIVES OF INDUSTRIAL HEALTH HEALTH 4 TABLE Proved Cases of Primary Cancer of the Lung Smoker Yes Yes Yes Yes Yes Yes Yes Yes Yes Exposure 26 yr in Cat II 34 yr in Cat I 37 yr in Cat I 32 yr in Cat I 22 yr in Cat II 33 yr in Cat III 30 yr in Cat II 16 yr in Cat I 28 yr in Cat III Died 10-12-51 5-3-55 5-3-55 7-20-55 8-20-50 -51 4-30-53 11-22-53 8-5-54 8-5-54 5--55 5--55 Autopsy Yes Yes No Yes Yes Yes Yes Yes Bronch se Asbestosis Yes Yes No No Yes Yes Yes No No 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 evidence points to cancer of the lung There were three such cases The term years of risk has been used to mean the number of men at risk for the year under observation A person who lived throughout the year was counted as a full year of risk but one who died during the year was counted as half a year ; Deaths occurring in the cohort and in which lung cancer is considered to have been proved as a cause are shown in Table 6. In Table 7 are shown three deaths which have 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 fur- ther discussion of the mortality rates which are derived in later tables For example it happens that the rate found for the proved cases is close to the expected rate based on the general population figures for the Province 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 however the 3 additional suspected cases were included increasing this figure to 12 the total would be very close to the 95 level of significance However having found just 12 cases we are not above this level and ' therefore the hypothesis that asbestos miners do not have a higher mortality from lung cancer than does the general population can- not be rejected Nevertheless the occur- rence of 12 cases in this sample would - increase the rate to a point which approaches the significant level Because of the tre mendous importance of the questionable respect regarding cases in this some detail them will be given here In one of these cases the suspicion of ray cancer of the lungis based upon the x interpretation and although no autopsy was performed the death certificate indicates . that death was due to lung cancer It is well known that the ray appearance of fibrosis especially if a localized density or a superimposed tuberculous lesion is pres- ent can simulate that of a tumor and by itself does not justify the inclusion of this case as one of proved cancer of the lung A second case was certified as having 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 having been due to chronic myocarditis with nephritis and pulmonary 9 congestion and possibly cancer of the lung On the basis of these facts it seems unwar- ranted to include these three cases among TABLE Suspected Primary Cancer of the Lung Case No. 123 123 123 Age 49 46 65 Smoker Yes Yes Yes Exposure 32 yr in Cat III 33 yr in Cat III 42 yr in Cat II Died 10-25-50 7- -53 9-30-55 Autopsy No Yes No Asbestosis No Yes No 642 Vol 17 June 1958 OF INDUSTRIAL HEALTH Ee LUNG CANCER IN ASBESTOS MINERS f the Lung Autopsy Yes Yes No Yes Yes Yes Yes Yes Bronch ed Asbestosis Yes Yes No No Yes Yes Yes No No .., close to the 95 level ; However having found just not above this level and othesis that asbestos miners igher mortality mortality from from lung lung the general population can- i Nevertheless the occur-* es in this sample would o point which approaches ' vel Because of the tre- <= proved instances of lung other hand they cannot in regarded completely It is that mortality rates have cancer On the fairness be disfor this reason been calculated both ways Table 8 gives the rates by age groups The rates by length of employment are shown in Table 9. During the first 40 years of employment the rate rises an observation which seems plausible since the men were growing older However after 40 years of exposure there are no proved cases reported for a total of 240 men dur- ing the six years or about 1440 years of exposure When the suspected cases are added one case does show up in this TABLE Lung Cancer Deaths by Age Groups 5 ince of the questionable neh. ect some detail regarding & n here regarding <^'. Number of Persons and Number of Lung Cancer Deaths No. of Deaths Age Group Proved Total se cases the suspicion of | g is based upon the ray 7% , although no autopsy was *: death certificate indicates lung ue to cancer is It yas the ray appearance of ^' if a localized density or te aberculous lesion is pres- PadEs ' that of a tumor and by stify the inclusion of this Annual Age group Lung CYaencaerrsDeofath I -3012 Rates per 100,000 Proved Total 4 * $ * 3 1 proved cancer of the 1 * TABLE Lung Cancer Deaths by Length of Employment Number of Persons and Number of Lung Cancer Deaths Length of Employment No. of Persons No. of Deaths Proved Total 0-350 0-3120 Totals 5,958 Annual Lung Cancer Death Rates per Years of Exposure 100,000 Length of Employment Proved Total 073012 01-8015 07330012 01-88015 dicates that the members of the cohort did not die from lung cancer at a younger age than the general population The rates by weighted exposure are shown in Table 10 and it will be noted that they present strong evidence against asbestos being a carcinogenic agent for if exposure to asbestos is in any way connected to lung cancer we would expect that the longer and heavier the exposure the higher the rate that would be found The only possible error in this interpretation could occur if the weighted exposures were inversely related to years of employment se was certified as having ydrothorax possibly due out again there was no postmortem examination Although it was subjected hologists disagreed as to r was present The death ving been due to chronic nephritis and pulmonary period This would produce a rate of 69 per 100,000 again demonstrating the im- portance proved because of these cases to questionable but un- - the final conclusion if there were 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 have demon- TABLE Lung Cancer Deaths by Exposure Category Number of Persons and Number of Lung Cancer Deaths Exposure Category I. ere rerrrress II I . II Unknown eee I eeee ee Unknown No. of Persons 2.031 2.150 1,772 5 No. of Deaths Proved + 3 2 0 Total 4 + 4 0 Totals 5,958 9 ",, " ssibly cancer of the lung ese facts it seems unwar- these three cases among ing Autopsy Asbestosis strated considerable resistance This is a bio- logical phenomenon which has been observed previously and is consistent with the theory of an intrinsic or endogenous factor in cancer The only other explanation would be that the susceptible members of this age Annual Lung Cancer Death Rates per Years of Exposure 100,000 Exposure Category I .. Enns II . ens II I I . Unknown . eee ee Proved 382013 382013 382013 382013 Tota 865 865 865 No Yes No No Yes No group had died earlier of lung cancer Table Over 382013 4 18. which appears later in this section in- Vol 17 June 1958 Braun 643 A. M. A. ARCHIVES OF INDUSTRIAL HEALTH TABLE Number of Persons in Various Weighted Exposure Categories by ' Length of Employment Length of Employment 10-19 20-29 30-39 40-49 50+ Weighted Exposure Categories I II III 707 598 490 883 851 314 363 243 247 218 137 76 67 41 24 10 Unknown 0 1 2 t 1 9 Total 1,795 2,398 923 603 185 55 TABLE Lung Cancer Death for Smokers and Nonsmokers Number of Persons and Number of Lung Cancer Deaths by Smoking Habits No. of Deaths Smokers Nonsmokers Unknown Totals Persons 4,673 1,265 20 5,958 Proved 9 0 0 9 Total 20012 20012 20012 20012 Totals Average years exposure 2,031 17.8 2,150 17.8 1,772 16.6 5 29.0 5,958 17.5 Annual Lung Cancer Death Rates per 100,000 Years of Exposure by Smoking Habits in which case the heaviest weighted exposure Category III would show the shortest length of employment Table 11 BR m~me No. of Deaths Proved Total 80013 30013 80013 30013 80013 30013 which lists the number of persons in various 80013 30013 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 date smokers may have included a larger Tee ' oye percentage of young men Consequently ad- ditional Tables 13 14 and 15 were con- structed to show the distribution of smokers Table 12 which develops the rates for smokers and nonsmokers is most striking It shows that not a single case of lung cancer developed among the 1265 nonsmokers and that all cases of lung cancer both proved and suspected occurred in smokers Table 12 was so striking that it was felt and nonsmokers by age length of employment and degree of exposure Although there are slight 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 shows that was tion further verification was necessary It possible that some abnormal distribumay have occurred g the non- TABLE Number and Percentage Distribution of Smokers and Nonsmokers by Age Groups Number that as far as length of employment is con- TABLE Number and Percentage Distribution of Smokers and Nonsmokers by Length of Employment Length of Employment Number Smokers Nonsmokers Unknown Smoker 3,200 896 411 164 2 4.673 4.673 39.3 Nonsmoker 689 224 202 150 0 1,265 44.2 Unknown 12 4 2 1 1 _ 20 40.7 Totals Average length of employment 1,408 1,967 722 433 110 33 4,673 17.0 377 426 199 166 75 22 1,265 19.3 07210018 07210 18 07210018 07210 18 07210 18 07210 18 07210018 07210018 16.0 Percentage Distribution Smoker 68.5 19.2 8.8 3.5 . 100 100 Nonsmoker 54.5 17.7 16.0 11.8 0.0 _ 100 Less than 0.05 Unknown 60.0 20.0 10.0 5.0 5.0 100 100 644 Length of Employment Percentage Distribution Smoker 30.1 42.1 15.4 9.3 2.4 0.7 100 Nonsmoker 29.8 33.7 15.7 13.1 5.9 1.8 100 Unknown 50.0 20.0 10.0 20.0 0.0 0.0 100 I'ol 17 June 1958 F INDUSTRIAL HEALTH LUNG CANCER IN ASBESTOS MINERS Lung Cancer Death ffoor r rs and Nonsmokers nd nd Number of LungLung Lung Cancer Smoking Habits Dea Persons 4873 1,285 2 No. of Deaths Proved Total 9 12 0 0 TABLE Number and Percentage Distribution of Smokers and Nonsmokers by Exposure Category Number Smokers Nonsmokers 1.553 474 1,691 452 1.425 338 t 1 Unknown 4 rs 9 0 Demography in the Provincial Ministry of 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 certificates which specified primary cancer of the lung 5,968 9% " Totals category Average exposure -seceeee 4,673 2.0 1,265 1.9 20 and all those which indicated lung cancer 2.3 but did not specify the origin were exam- Death Rates per re by Smoking Habits No. of Deaths Proved 80013 80013 80 13 80013 Total 70013 70013 70013 2| Exposure Exposure Percentage Distribution Smokers 33.2 36.2 30.5 0.1 100 Nonsmokers Unknown 37.5 35.7 28.7 0.1 20.0 35.0 45.0 0.0 100 100 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 for 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 larger ave included a in ig men Consequently ad- *- 3 14 and 15 were con- js yage yage length of employ- of exposure Although : differences they do not %. ct that all observed cases re in smokers In respect average : ) the combined & 3 was 4.9 years less than* okers Table 14 shows h of employmentis con- * proved cases in the cohort is only slightly cerned 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 if lung cancer were due to asbestos Table 15 shows that higher than the rate for the Province When the suspected cases are included in the calculation the rate for the cohort rises to 33.8 per 100,000 which is about % higher than the rate for the Province This it will be recalled from the previous dis- the average exposure category was almost the same for the two groups Therefore this variable seems to be of no importance cussion of the effect of the suspected cases on the results approaches but does not exceed the significant level in accounting for this difference One further interesting observation from The result of this additional analysis is - Table 16 is the rather marked increase in that none of these factors appears to lessen the total number of cases for the Province the effect of Table 12 between 1950 and 1955. It is assumed that td Percentage Distribution Vonsmokers by Length mployment emaber rs) % if 2 3 1s 33 Nonsmokers 377 426 199 166 75 22 Unknown 82-0 18 82-018 82-0018 82-0 18 82-0 18 82-0018 Comparison of the Cohort Experience with that of the Province of Quebec Dominion of Canada and the United States.- 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 stated earlier in the office of the Division of at least part of this increase is due to im- proved recognition and reporting of lung cancer during the interval For this reason the years 1954 and 1955 were thought to be more nearly representative of actual conditions Even so it is quite likely that the general population is not studied for lung cancer with the same diligence with which wz 1,265 82-0018 .0 19.3 16.0 e Distribution ker L i % ba . % Nonsmoker 29.8 33.7 15.7 13.1 5.9 1.8 100 Unknown 50.0 20.0 10.0 20.0 0.0 0.0 100 l'ol 17 June 1958 TABLE Comparison of Cohort with Province of Quebec Province Cobort Proved Province excluding asbestos workers NumbeNr umber 1950 1,198,000 196 5.923 3 1 1,192,000 193 1951 220 218 Lung Cancer Deaths 1952 1953 1954 245 303 303 002 3 1 002 2 1 002 300 302 Annual Rate per 1955 Total 100,000 357 1,624 28 3 12 3 9 354 1,612 33.8 25.3 22.5 population for estimated In the Province figures it has been assumealdlmale lung cancer deaths are for men of 20+ midpoint of the enumerated population for 1951 and the Approximate mographie Number alive in cohort at beginning of 1952 for 1954 Rapport Div de la De- Braun 643 Age Group M. A. ARCHIVES OF INDUSTRIAL TABLE Lung Cancer Deaths for the Province of Quebec * HEALTH Estimated Estimated Population Number of Deaths 1954 Total Certified Total 17 67 100 111 Proved 818885 Specified Primary Total = Proved : a . 1955 Total Certified Total 17 60 117 148 342 Proved Specified Primary ~ Total Proved 12585 12585 12585 12585 337 1954 Age Group 20-44 45-64 55-64 deeeee Total Certified Total 2.2 33.2 73.0 91.7 Proved 1.7 17.8 17.8 27.3 Specified Primary Total 1.4 21.3 50.4 - 56.2 Proved 1.2 14.4 23.4 24.0 23.8 9.7 15.4 8.0 * Data from death certificatescertificates in REasptpimoartte for population Div de obtained byby Demographie applyingapplying 1951 percentages ffoorr age groups for 1955 Total Certified Specified Primary Total 2.2 29.7 85.4 122.3 Proved 1.2 17.3 41.6 44.6 Total 2.2 27.7 84.7 122.3 Proved 1.2 15.8 41.6 44.6 27.6 12.5 27.2 12.3 males to the total population for 11995544 as given this disease is looked for in the miners and it seems probable that the mortality rates for 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 17 was compiled to show the an- nual specific lung cancer rate of cases in which the death certificate 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 1955 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 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 646 This comparison summarized in Table 18 shows that the observed number of 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 of the age group of 65 and over the five deaths provide a figure which is almost significant at the 95 level How- ever it should be noted that this number includes one of the suspected but unproved cases previously referred to it is rather likely that the Furthermore rate for the general population is understated in this age group for the obvious reason that the exact cause of death in the very old is not TABLE Comparison of the Actual and Expected Number of Lung Cancer Deaths by Age Among Asbestos Miners Age Group Province Total Specified Primary Rate per 100,000 20-44 1.8 45-54 24.5 55-64 67.6 65+ 89.3 Unknown - No. Miners Expected Expected Expected No. Deaths * Observed No. of Deaths Proved Total 3,901 1,124 615 315 3 ed 2 2 2 -- 1 1 3 4 0 1 3350 3350 3350 3350 * The expected number based on the average the 1954 and for she of 1955 specific rates Province of Quebec - Actually 0.4 ae ge Vol 17 June 1958 INDUSTRIAL HEALTH Quebec* sSSSSy LUNGLUNG CANCER IN ASBESTOS MINERS Age Distribution of Adult Males for TABLE _=__the Provi. nce of Quebec 1951 Table Annual Death Rates_per_100,000 Rates_per_100,000 Rates_per_100,000 for Cancer of the Lung in Canada 1955 Certified Proved 236313 236313 236313 236313 Specified Primary Total Proved 17 56 519980 116 519980 148 519980 oo Group Age nee weeceeere Total -- Province Number 727,135 188,952 128,944 113,467 1,11,15588,,4948 98 Percentage 32 32 11 218 218 in Cohort 822018 822018 822018 Age Group Under 30 30-34 35-39 40-44 55-59 1931-1933 0.2 0.9 2.0 Groups of Years 1941-1943 0.3 0.9 5.45.4 18.9 12.7 27.0 1950-1952 1.0 0.8 6.5 59.7 236313 337 519980 * 1955 Certified Proved 12 17.3 41.6 14.6 12.3 Specified Primary Total Proved 27.7 84.7 41.6 122.3 44.6 a2 12.3 the total population for 1954 as given n summarized in Table he observed number of mple is not significantly spected number of deaths age of the 1954 and 1955 _ - ovince It is true that in e group of 65 and over rovide a figure which is at the 95 level How- noted that this number ^ suspected but unproved ferred to Furthermore that the rate for the is understated in this obvious reason that the h in the very old is not rison of the Actual ber of Lung Cancer by Age Among stos Miners and No. Miners Expected No. of Deaths* Observed No. of Deaths Proved Total 3,901 1,124 615 315 3 Ot Ot 2 1 033 2 3 0333 2.: 4 0333 -- 0 0333 based on the Province of Quebec average of the the 1954 and 41602 Rapport 1954 intensity intensity a matter of of thethe samesamesame ofof iinntteerersetst as it is in younger persons Table 18 also answers a question pre- 70-74 8805-+84 All Ages 10.7 30.6 86.3 15.8 27.9 50.750.7 27.9 71.0 11.4 14.3 2.8 7.1 15.8 * Mortality from Lung Cancer in Canada 1931 to 1952 viously raised It shows that the members of the cohort have not died from lung can- cer at an age earlier than the general population and that such an explanation cannot be offered for the absence of lung cancer in 240 men with more than 40 years of increase is particularly marked after age 50 confirming an observation previously made to the effect that until recently lung cancer has probably been underdiagnosed in the older age groups in the general popu- | employment referred to on page 643 Before leaving this comparison of the Province with the miners it should be shown that their age distributions are 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 oldest age group will be larger in lation To use these figures for purposes of comparison it is necessary to combine the rates for 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 approximation However the rates would be somewhat as the general population The data presented in Table 20 indicate that the lung cancer rate generally decreases after age 70. Therefore we could expect the rate for all 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 population 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- 79 lips gave Canada for 1952. The age- and specific three periods between rates for males are rates for 1931 and given in Table 20 These figures show strikingly the increase in rates between 1931 and 1952 and this follows: Age Group 20-44 45-54 55-64 65+ Rate 5 27 69 90-95 These rates are in general lower than those developed for the total proved and suspected cases of lung cancer among the asbestos miners The only large difference however is in the age group of 65 years over and it is quite possible that the for this group may have increased Canada between 1952 and 1954 as it and rate for did for the Province of Quebec Table 17 A further comparison has been made with an over 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 proved cases and 33.8 per 100,000 for total cases among the 647 Vol 17 June 1958 Braun A. M. A. ARCHIVES OF INDUSTRIAL HEALTH TABLE Vumber of Deaths and Death Rates per 100,000 by Age Groups for the Adult Male Population of the United States* Age Group 20-44 45-54 55-64 65+ Total Population 24,544,000 8,065,000 6,340,000 5,670,000 44,619,000 Cases 883 2.979 6.254 6.483 16,599 Rate per 100,000 3.6 36.9 98.6 114.3 37.2 * Data from Vital Statistics of the United States Vol 1 2 and 1952 asbestos miners in this study It is therefore 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 States are more complete and therefore possibly more comparable to the data for the miners specific rates were computed from 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 8. 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 28.0 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 or 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 Hue- 58 per has stated that there are about 35,000 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- 648 way and other 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 of asbestosis with lung cancer was reported At least 1,000,000 years of exposure has thus been accumulated and this figure can be divided by the approximately 150150 re- cases of lung cancer with asbestosis ported This during the year period gives a rate of 15 per 100,000 whichis at rate least indicative that any which can be calculated lung cancer for workers ex- posed to asbestos dustis not much greater than that for the unexposed population " nb Comparison Between Eight Counties Ad1 jacent to the Producing Areas and Eight Selected Counties compare lung cancer mortality rates in the counties sur- producing with rounding the areas as- another group of counties in which no bestos miners are likely to reside the rates , were computed on the basis of figures for ~ the years 1950 through 1955. The eight counties selected for comparison were Ar- * genteuil Chateaugay Montmagny Port- neuf Richlieu Riviere St. * Hyacinthe 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 Rich- Drummond Frontenac Megantic mond Sherbrooke and Wolfe Table22 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 Megantic County has been shown separately as has the Province of Quebec and also the Prov- ince with the eight 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 from the table that the lung cancer death rate for the eight counties Vol 17 June 1958 Megan Eight Eight Provir Provi adj Montr It 1111r duci of| Wh twi cou Pro rat WOI ver 195 in un oth ex WO CO1 the tie inliv C P C P -A F INDUSTRIAL HEALTH countries at least 50,000 e exposed throughout the an be assumed that this 1 fairly constant in the 20 5 when the first case of lung cancer was reported 00 years of exposure cumulated and this figure by the approximately 150 re- ancer with asbestosis he year period This This 5 per 100,000 which is at hat any lung cancer rate alculated for workers ex. 1 dust is not much greater- e unexposed population greater tween Eight Counties Ad- Producing Areas and ~ ounties compare lung rates in the counties sur- 5 producing areas with _ counties in which no as- : likely to reside the rates In the basis of figures for through 1955. The eight for comparison were Ar-3. igay Montmagny Port- Riviere St. -* errebonne mainly because wide geographic * distribu- ' he Province The counties of their proximity to the clude Arthabaska Beauce ntenac Megantic Rich- 2. and Wolfe Table 22 r of lung cancer deaths O through 1955 for each , and a mortality rate t male population in 1952 le comparison Megantic shown separately as has Quebec and also the Prov- ght producing d Because of its unique| rate Montreal et Isle de 1 listed in order to provide n from the table that the rate for the eight counties Vol 17 June 1958 LUNG CANCER IN ASBESTOS MINERS TABLE Number of Lung Cancer Deaths and Rate per 100.000 Years Counties M. antic County Eight Adjacent Counties Eight Selected Counties Province of Quebec Province of Quebec less eight adjacent counties Montreal et Isle de Jesus Adult Male Population 1952 1950 13.100 3 97.600 5 83.000 2 1,198,000 196 1.100.000 190 394.000 3 1951 1 3 10 220 217 7 " Male Lung Cancer Deaths 1952 3 9 5 245 236 158 1933 3 16 18 303 287 192 1954 1 + 3 303 299 185 1955 t 16 9 337 341 225 Total 15 34 49 1624 1370 770 * It is assumed that all male lung cancer deaths occurred after age 20 Rate per 100,000 18.9 9.4 9.8 22.6 23.8 32.3 immediately surrounding the asbestos ducing 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 Province and considerably lower than the rate for Montreal The figure for Montreal would certainly be higher except for the very 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 the 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 evidence that the persons who live and work in the coun- ties surrounding and adjacent to the as- suggestive of cancer of the lung and included such diagnoses as mediastinal lymphosarcoma mesothelioma cancer of the leg with metastases to lung abscess of lung and cancer of the pancreas One other was diagnosed on the basis of ray only In addition there are now living four cases in which the diagnostic evidence is strongly suggestive of lung cancer This is a total of 33 cases of all types including 10 sus- pected but unproved cases and + that are still living The remaining 19 constitute the total of proved cases of cancer of the lung among the asbestos miners since 1940 The proved cases averaged 59 years of age at death and varied between 37 years and 68 years Their working span covered periods varying from a minimum of 14 years to a maximum of 37 years Only three men had less than 25 years of em- producing areas have any greater incidence of lung cancer than those who ployment in the industry Seven among those on whom such information is avail- live elsewhere in the Province able had a weighted exposure placing them Comment on All Recorded Lung Cancer Cases Living and Dead among the Asbes- in Category III and six worked in an exposure represented by Category I. tos Although a simple enumeration of all the known or suspected cases of cancer of the lung in these areas has no particular value 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 covered by the study including one in which the diagnosis was mediastinal lymphosarcoma During the period covered by this There were only 17 among these proved lung cancer cases in which we have information regarding the presence of as- bestosis Asbestosis was present in nine although it was minimal in two Two pathologists disagreed regarding its presence in another At least seven of the 19 proved lung cancers therefore were not accom- panied by asbestosis investigation 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 Summary and Conclusions Interest in the question of whether there may be an association between lung cancer 649 Braun e A. M. A. ARCHIVES OF INDUSTRIAL HEALTH and exposure to asbestos has been 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 cases 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 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 certain 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 availability of reliable 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 were in the industry in 1950. Data relative to their characteristics were collected and their status at the end of a year period of observation was de- termined In the case of those who had died an exhaustive search of 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 of 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 accepted 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 remaining the whole period but 5771 of the 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 of 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 Thirty per cent of the cohort were more than 45 years of age and thirty per cent had been _ Thirty employed for longer than 20 years ~ per cent had a weighted exposure which- placed themin the category of highest ex- posure 4 The mortality rate for lung cancer as : proved 4. computed on the basis of nine ; deaths among the cohort was 25.3 per 100 : 000. When the three suspected cases % were were added the total rate for the cohort rose* to 33.8 The of the a importance suspected = but unproved cases in these~ determining rates has been reiterated because it is likely that such cases would not be included in . the statistics for the general population and because they influence 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 exposure or with degree of exposure a fact which presents strong evidence against the carcinogenicity of asbestos Comparison of the 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 22.5 per 100,000 for the rest of the Province and 20.8 per 100,000 for adult males throughout the Dominion of Canada It also compares satisfactorily with rates Vol 17 June 1958 LUNG CANCER IN ASBESTOS MINERS e to trace 133 of these these d but 5771 of the ad to be still living remaining living in 1955 he 187 known dead is considered to have been ed in 9 and to be strongly of 37.2 25.3 and 28.0 obtained from various sources for adult males in the United States Finally in this matter of comparison it would appear that the world experience of persons exposed to asbestos dust is not worse with respect to lung cancer than that | of the cohort were studied studied -$- of the unexposed population The counties surrounding the asbestos- age length of employment producing areas in which it is presumed age of their exposure and abits It was found that " most of the asbestos miners live have alF most identical mortality rates with those of ers within the definition of F eight counties widely scattered through the in this study Thirty . Province and are lower than those for the cohort were more than 45 remainder of the Province and much lower i d thirty per cent had been than the rate for Montreal nger Thirty than 20 years weighted exposure which x he category of highest ex- Since 1940 there have been 19 cases in which the diagnosis of primary cancer of the lung may be considered to have been a proved Approximately half of these cases rate for lung cancer " ~' e basis of nine proved : cohort was 25.3 per 100 *: ree suspected cases were . rate for the cohort rose were associated with asbestosis All but one "/ died in the recognized cancer and at least third had only the lightest exposure Category ) to asbestos dust On the basis of what are believed to be suspected portance of the =. ses in determining these 3 terated because it is likely vould not be included in he general population and complete and reliable data it seems fair to conclude that the asbestos miners in the Province of Quebec do not have a significantly higher death rate from lung cancer than do comparable segments of the general ence the results so mark- population Furthermore the death rate from lung e findings in this study from lung cancer does rease with length of ex- gree of exposure a fact ong evidence against the asbestos he experience among the ith that of various seg- posed comparable poputhe observed number of niners is not significantly pected number The rate nong the asbestos miners compares well with the 0,000 for the rest of the per 100,000 for adult e Dominion of Canada atisfactorily with rates cancer in the areas contiguous to the asbestos 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. 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Saupe E Further Contributions to the Roentgenological Gewerbepath u 81. Smith K. Diagnosis of Asbestosis Arch Gewerbehyg 391-406 1939 W Pulmonary Disability in Asbestos Workers M. A. Arch Indust Health 198-203 Aug. 1955 82. Smith L. W Pneumoconiosis and Lung Cancer with Special Reference to Silicosis and Asbestosis Compens Med 3-10 Nov. 1949 83. Smith W. .: Survey of Some Current British and European Studies of Occupational Tumor Problems Part III Asbestos M. A. Arch Indust Hyg 242-263 March 1952 84. Stoll R Bass R. and Angrist A Asbestosis Associated with Bronchogenic Car- cinoma M. Arch Int Med 88 831-834 Dec. 1951 85. Teleky .: Occupational Lung Cancer Acta Union internat contre Cancer 253-273 1938 also Zentralbl Gewerbehyg 27:33 1940 86. Vorwald A. .; Durkan T. M. and Pratt P. .: Experimental Studies of Asbestosis M. Arch Indust Hyg 1-43 ( Jan. 1951 87. Wedler H. W Asbestosis and Lung Cancer Deutsche med Wchnschr Aug. 6 1943 88. Wegelius .: Changes in the Lungs in 126 Cases of Asbestosis Observed in Finland Acta radiol 28 139-152 1947 89. Werber M Pulmonary Asbestosis Associated with Carcinoma Zentralbl Arbeitsmed u Arbeitsschutz 179-180 Nov. 1952 90. Wood W. B. and Gloyne S. .: Pulmonary Asbestosis Complicated by Pulmonary Tuberculosis Lancet 954-956 Oct. 31 1931 91. Wyers H Asbestosis Postgrad Med 25 631-638 Dec. 1949 92. Wynder E. L. and Graham E. .: Etiologic Factors in Bronchiogenic Carcinoma with Special Reference to Industrial Exposures Report of 857 Proved Cases A. M. Arch Indust Hyg 221-235 Sept. 1951 653 VOLUME 17 JUNE 1958 NUMBER 6 INDUSTRIAL HEALTH Mutual Goals of Public Health and Occupational Medicine L. E. Burney | New Techniques in Teaching Occupational Medicine Jean Spencer Felton Significance of the 1956 Social Security Amendments to the Insurance Business John H. Miller The Reconciliation of Pensions and Social Security Disability Insurance Robert E. Royes Occupational Medicine and Modern . Drugs Albert H. Holland Jr. Practical Psychiatry in Industry R. H. Felix Practical Techniques AplicationApIplnicadtiuonstroyf PsycPhsyichaiattrriic c Ralph T. Collins . Potassium Alloy Finkel Asher J. Finkel and Willard Willard B. ~ Lyons An Epidemiological Study of Lung Cancer in Asbestos Miners Daniel C. Braun and T. David Truan CollectionCollection of Integrated Samples of Gaseous Effluents Brief Richard S. Brief and Philip A. Drinker . Practical Significance to Industry of Recent Developments in Tuberculosis Management Edward T. Blomquist Industrial Health in the Atomic Energy Industry James H. Sterner Executive Health Examinations Robert Clyne Tellurium Oxide Marvin L. Amdur Practical Aspects of a Hearing Conservation Program Lloyd B. Shone News and Comment Books AMERICAN MEDICAL ASSOCIATION PUBLICATION