Document qkEVyEm25Q1OvBOj9xOpqM00k

. .f:... /]r\A*1 ( \t S';1 . . . PLAINTIFF'S EXHIBIT /rem Hie A. .U. A Ateh.;;t nf [mhulrwl IlcMlh Jum* 19H. I'al. IT. />/. 0Jt-6SJ Ceffright 19SX, by !unticim Maina! .him talion Ail Epidemiological Sludy of Pit!. orott. Exhibit No--------- d Lung Cancer in Asbestos Miners . OANIU C MAUN. M.O.. T. OAVIO TAUAN. M.A.. Plt)ikr|li Dot*------ Witness Judith E. Thiel, N.P. Ever since the pronounced increase in the incidence of lung cuicer among nudes 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 stances and then set about in an intensive search for lung cancer among j>erson> who have had any exposure to those materials. In this connection. Smith ** w rites: "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 exjiosure to this material is known to cause a specific type of pneu moconiosis, and becau-e- persons u ho show this form of pneumoconiosis of ten conic 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 1951 Merewether'* reviewed all deaths from asbestosis recorded in Eng land since March. 192-1 Lung cancer oc curred in 16of these cases. GInyne.*1 Accepted fur publication Jan. TO. 1958. This stud)- wa> mule possible through a Kraut front the Quebec A'U-slus Muimr As'--o.iliun. Medical Director (Dr. flraiiu) and Statistical Consultant (Mr. Trtuu). Industrial Hxicm Foundation. whose work is also frequently referred to as establishing a connection Lctwcctt asbes tosis and cancer of the lung, reported in 1951 that cancer of the lung was present in 1-1.1 rc of asbestosis cases examined by him. In 1941, Xordmann and Sorgc * claimed to have produced lung cancer in nice which they exjKjscd to asbestos dust. Since 1951, additional cases of cancer of the lung coexisting with asbestosis have been fqioncd, and, according to Hueper1* 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 bv many authors, and several writers were using-the term "asbestosis cancer" of the lung. Wcrbcr,99 in 1952, stated cate gorically that in 7c,'o to Y7c,o of cases of asbestosis, after a latent period of about lyi to 20 years, carcinoma becomes estab lished in the lung. On the other hand, not all authors ac cepted this alleged association without reservation. 5au(<c 99 in 1939 repotted that he had discovered no cases of lung cancer among 620 cases of asbestosis which he had examined; and in 1942, Hoileb and Angrist41 expressed the opinion that the number of cases of asbestosis with lung cancer was too small for statistical evalua tion. In 1947, Wegchus99 reported 126 radiological!)' diagnosed cases of asbestosis among 470 workers in Finland, and found no cases uf lung cancer in this group. Goldbiatt and Goldblatt in their section of Mercwethcr's latest book,*4 state: "But at no Mage in all these impressive researches was any clue obtained which might have offered any support to the |>uSsibiliiy dial asbestos could act as a carcinogen. There 634 380 LL W'G CANCER IN ASBESTOS MIXERS is no reliable criterion by which one can anticipate carcinogenicity anti, as is well known, relatively minute changes in the strueture of a chemical carcinogen are surficicnt to diminish or eliminate carcinogenic action. If asbestos is iinleed to be regarded a> a carcinogen, the need is felt to demonstrate some property which can be regarded as something more thati inertness." These authors advance the theory tliat, until some more experimental evidence of direct carcinogenesis by asbestos or a de composition product of it cau be obtained, asbestos might be considered as a "co-car cinogen" which only induces a further de velopment of a preneoplustic condition brought about by something iiuic|>endciu of the asbestos, such as an endugenous 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 ot the reports arc clinical and not epidemiological. They lack many ele ments 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 hapj>citcd is that succeeding authors have drawn conclu sions and generalized beyond the scope of the works which they quote. Nowhere, for example, haie we found references to a population of asbestos workers, although several authors who have quoted the ob served incidence of lung cancer in autopsies o( persons a.*Ao also haJ asbestosis imply that this incidence applies to asbestos work ers, generally. We have likewise been unable to find any study which actually calculated the incidence of lung earner among a population of persons who had asbestosis, and not just those who came to autopsy. With the exception of a p;i|>vr by Doll,** none of those reviewed gave any data on cxjwsiire and dust concentrations, and even Doll's paper merely mentions 'Sclk-dtilvd" areas, by which is meant, "those a teas where processes arc carried on which were scheduled under the Asbestos Industry Uegtil.ttiotts of 19.11 as being dusty." 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 of the lung tissue, or it may mean a radio logically detectable condition. , Most of the published re(*urts obviously inciudcd women among their cases, but some of them do not give the nuinler or proportion of' women involved in the study. There is also a Lack of uniformity as to what tyje of exposure most studies have dealt with. Of 99 cases enumerated by f fuv|>cr14 in 1955. only 10 ap{>car 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 arc also notably absent in the majority of these rqiorts. With this understanding of the limita tions of the existing literature with respect to epidemiological generalisation, it may be of value to consider in somewhat more de tail some representative earlier publications, a few of which were referred to briefly above. One of the most detailed studies and one which deserves the most serious considera tion is that reported by Doll ** m This study reviews causes of death among asbestos workers based on coroners' rec ords. (t alo. attempts to estimate the risk by studying records of men who workcJ fur at least 20 years in exposed situations. Broun--Tntan 381 *635 T iiih is meant, ,are carried on ,-r the Asbestos 1931 a* being i complete tack fed in the pubmpie, the term refer to changes fic examination mean a radio* a. rports obviously heir cues, btit i the nundier or >cd in the study, uniformity as to ost studies have enumerated by ) appear to have . and 7 in /eports ap i miners, but it of the 99 cases d, and since no i are carried on of the reported ?s in the textile ip habits, family of time in the (dividual case are majority of these 'E of die limiuture with respect <ratian, it may be mewhat more deirlier publications, tferred to briefly d studies and one serious considers- Doll3* in 1955. i of death among - oners' rec ite the risk ..on vs ho worked xpoed situations. m A. At. a. Attain ts ot tsix-.xT/tt.tt. tn.u.Tu Dull cuiicludcd that lung cancer was a spe cific industrial Iwizard of certain asbestos workers and that, after 20 year.* of ex|in sure, the risk is 10 times a> great as for the general imputation. This article is im|ortant fur several rea sons, in additiun to the definite conclusion* at which it arrives. For example, it begin* lung cancer in other forms of pneumoconio sis wa b.7r,(, ami in 169 cases which proved nut to have any type of pneumo coniosis it was 8.3^c. Gloync considered "the mortality of ihe asbestos workers" to be "disturbing." First of all, it i> obviou* that the |ia|cr does not deal with the "mor tality of asbestos workers." and secondly, it must be borne in mind that ail of Dr. 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--that lung cancer is an oceu(>ationai 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. Estimate* of the number of persons potentially exposed to asbestos dust in the United States alone vary from 10,000 to 35,000, and the incidence of as bestosis of any degree might be higher than Gloyne's cases were submitted to him for study because the findings were umoual for uncomplicated pneumoconiosis, (i can reasonably he assumed that cases, including those of asbestosis. in which the finding* were not considered unusual were not sent to Dr. Gloync for examination. As a mat ter of fact, in the same paragraph in which he expresses concern over the incidence rate in asbestosis. Dr. Gloync himself |ioiiit* out (hat the rate for lung cancer based on necropsies at the London Chest Hospital was 2l.3r/c while the figures of Doll imagines. the KegistrAr-Gcneral showed only 2.4^e. This study, like so many others, involves He thus recognized th.it autopsies on a cer autopsy records. The number of persons tain selected group of cases were not rep involved in the statistical analysis is only resentative of the general population. It 113, representing only 1.042.25 man-years would seem, (hen, that notwithstanding the of life. It is also true that in selecting men value of Dr. Glovnc's work, its imiortnncc who had been employed for at least 20 as an index of the prevalence of lung can years, the study automatically excluded cer in asbestotics has been misinterpreted those who died .from other causes after by sonic who have quoted him. All that it shorter employment. really show* is the fact that in a group { Another reason why (hi* publication is 121 cases, selected for special study pn- of importance is a statement which it con marily because, they seemed abnormal by tains to the effect that "the strongest evi preliminary examination, 17, or I4.1^r, had dence that it (lung cancer) may be a hazard lung cancer. (in asbesto* workers) has been produced Mercwcther 13 in 1947, in the report of by Mercwcther and by Gloync." the Chief Inspector of Factories, reviewed In 1951 Gloync " presented a review ait ca*e> reported between 1924 and 1946 of 1205 autopsies on persons who had in which asbestosis was the cause of death worked in various dusty occupation*. This or a coexisting condition. This uork was number included 132 asbcsios workers, of later extended to include all such cases re whom 121 showed "pneumoconiosis'*--pre ported up to December. 1954. by which time sumably asbestosis. Primary cancer of (he lung occurred 17 times in this group, an incidence rate of 14.!^e for lung cancer among asbestosis cases coming to autofix. There were in his series 796 cases with sili cosis, and 6.9Ce of these also showed pri mary cancer of the lung. The incidence of there were 344 deaths, including 205 males and 139 females. Among them ucre 55 cases (l6^o)` 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 Vmt. 17, Jtff, MX 6J6 382 n' :rauil a total :rc those diswe been cases ight were dis'.runaway *3 in t5. and, unless oinpiete, these Jed in his re t is quite po-- iy Merewether some duplicathose of other miological much of what :nt concerning if lung cancer beet* dr* steal nta- autopsy *nc extent by various clinisonai observaever, attention atic tnvestigasame methods ii previously in liseascs, that is ethods. hod of investi* discussion, we tudy should be I a well-defined >ble data for all . including the (3) a sample of the poputaid observations vr study. (o most of the ported, is that concerning the to have order to 1 asbestos a study to in3 as the dead. KV . . I . I , iI I , , . -' j I i ' '1 A. U. A. ARCilirBS OF IXnUsTHl.ll. Ill.ll.ilI Limiting the investigation tn cases coming to autoTty. as has been frequently done in earlier studies, still further restricts its uc in generalization. The problem with which we arc concerned is whether asbestos miners experience more lung cancer than does the general iwpulatioii. 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 ref*ortcd to date. A very irrqiomnt 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 stud ied to provide meaningful results. Recognizing the difficulty 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 relative frequency of 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 eases coming to autopsy. Attempting to compare two jKjpulation groups, looking only at the relative fre quency of cancer in various body sites, may result in finding a higher iercentago (relative frequency) in one of the groups, when, in fact, the mortality rate of cartcer of a particular organ is exactly the same in both groups. This is very clearly dem onstrated in the excellent article by Dorn.J* The mortality rale from a particular cause is the true measure of comparison. It is apparent that selected group' such as hospitalized patients or autopsy cases may not be in any way representative of a larger group, ami that in dealing with such simples, the observer may easily find more cases of a given disease than would lie found in another group of the same size, but representative of the general |ipulatiiui. It 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 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 study of 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 eases coming to autopsy, but only to such eases. For in formation front such a study to be pro jected to same 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 l>e false. There is some danger (hat the figures rqmrted 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. nor can the generalization be made for the reasons stated. Close 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 way that it constitutes a good simple of the whole population of asbestos miners in Quebec. Data for all members uf this group have been collected and analyzed. Those concerning lung can cer have received must careful considciatmn. Details of the methods employed will be set forth later, but the ty|c of approach i> considered to i-ermit of fair compari-ous and valid - generalizations. Collection and Analysis of Data A preliminary survey of [inieiilial Sources of inlc.rm.nion in February, 1956, involved 636 Vo! IT. June. WX 384 3 Lt'XC C.tXCl.R /.V .l-S/f/.srm MIXI KS discussion* with the physician* in charge cohort was then followed by means of the of the asbestu* comjintties' programs ami aiiiui.il physical examination records with clinicians. pathologists. representatives through a six-year interval, 195(1 through i of City and Provincial health dc|Mruiiciits 1955. All data regarding this group were and of the Canadian Cancer Society, ami then tabulated its order to determine the other interested i*-rsou>. It wa> found that eiiaracteristics of the cohort. For those who morbidity* data, although somewhat limited, survived the entire period, reference was were available from Mich sources as the made *.u the physical examination results hospitals in Montreal and Queliee City, and and x-ray findings at the cud of the |>criod. the 13 cancer detection centers in the I'rm- Those who had died were tabulated sepa ince. However, because ol the high mor rately. and the cause of death was tality in lung cancer, it seemed advisable corroborated by examination of the death to depend u{>on data relating to deaths. certificates. A further search was made These we found to be 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 and the known dead had been tabulated. liminary survey, it was apparent 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 jicrsnns Eventually, all but a small number of these employed in the asbestos milling industry were accounted for as either living or dead, and the mortality figures for the general and in the latter event, the cause of death I I* population. was substantiated in a similar manner, and Following this exploratory survey, the the results added to the original list of initial effort was directed to the collection deaths. of data relating to all workers who had Death certificates for the Province of been processed through the clinic at Thct- Quebec for the years 1952 to 1955, inclu ford Mines since its inception in 194/. and sive. were reviewed in the department of similar information regarding all wmkers vital statistics of the Provincial Health at Asbestos. Que. Data front the clinical Ministry, together with statistical sum records included the age, family ami |<er- maries of the causes of deaths in the Prov sotial medical historic:-. Miioking habits, ince by counties. All cases in which death number of years of cxt<o>ure. an estimate was certified as having been due to pri of weighted ex[>o>ure, and the course of mary cancer of the lung were examined for I the individual's health Main* nr the cau*c such information as place of residence, of his death. occupation, date of death, hospital in which I From this information it was possible death occurred, and whether or not an to formulate a "cohort" which could lie well autopsy was performed. Cases in which defined, should be representative of the lung cancer was given as a cause of death, whole group, and could be followed for a but in which it was not specified as to I definite period of time. All of the available whether the cancer originated in (he lung, experience indicates that the development were also reviewed in an effort to include of asbestosis in less than five years of ex all instances of primary carcinoma of the posure must be somewhat rare. Accord- lung in the study. irtgly, the cohort was defined as including The statistics for the Province of Quebec I every miner who had a total exposure of relate to population, total deaths from all I five or more years, and who was on the causes, total deaths from cancer of all tyjics. i employment rolls in 1950. Office and other amt death* from lung cancer. These were nouexposed personnel, regardless of length collected and tabulated by counties and by i of employment, were not included. This sex for the years 1950 to 1955, inclusive. Brmtm--Tntam 439 385 / / iieatis of the hi records 950 through group were :(cnnine the jr those who Terence wa> nion results l the period, ulated sepadeath was >f the death was made cohort who n the living n tabulated, left employ* resignation, her of these ing or dead. ' death - r, and mat list of Province of 1955, inclu>artment of cial Health stical sum* n the Provvhich death Jue to pri:aiuincd for residence, al in which or not an i in which *e of death, ified as to n the lung. to include inta of the of Quebec s front all ' ypes, - were . and by . inclusive. AN ' j ; | I | I j j | A. St. A. AKCtitn.s or ixdustmai. ni.At.Ttt From them, death rates fur the general population of Quebec and of individual counties were calculated for specific years and analyzed by cause. Practically all employees of cine 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 an additional check u;>oti 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 (>oiicy. and particular notice was taken of the claims in which the proof of death was based on cancer of the lung. In addition to this analysis of deaths oc curring in the cultnrt and during the years under observation, every known death from cancer of the lung, as well as every case diagnosed but still living, has been tabulated and analyzed. They will be discussed separ ately front those included in the population and time-interval under study. A comparison of lung cancer mortality in the asliestos-producing counties has iieen made with that in counties which arc 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, and for the United Stales, according to the most recent published ami unpublished material. Deaths from lung cancer among asbestos 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 mcviicai services. In this man ner. there was established a list of cases in which primary cancer of the lung is con sidered to have been proved as the cause of death. A few cases in which lung cancer i> strongly suspected but not proved as the cause of death were considered scparatelv. Mortality rates have been calculated using both the "proved" and the total of "proved" and "sus|ectcd" cases during the years un der observation. Comparisons were then made between the death rates from the same 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 of the cohort will be presented here as a preface to the results of the study: OriKttuI Coknrc [MtitKIftl * Final Cafe*** Laim< n IVSI ml wirnl) UrMi fcr I4JJ Cm*err af lu**f QwfHNfMbk canctr af lunf Other cauaea I'aJsfMtan (turn SfiaAm VintawUti * I'nbima 4.0*1 111 !.>( .77l 147 ,* i 14* 4 4.47J U4S X Tables I, 2. 3. and 4 present age, number of years of employment, weighted average exposure, and smoking habits of the cohort. cause among sjvecific segments of unex|Htscd persons. All lung cancer deaths, both suspected and proved, were carefully ana lyzed to determine [>ossib!c relationship or correlation* between the devclotHiieiit of A com|iari>oii of the exjiOMire to asbestos dust is pre.-eiited in Table 3. All members of tic cohort were placed in one of three categories, representing increasing degrees of cx|<osure based oil 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 cancer, i>ersoiial history of heavy smoking, coexistence of asbestosis, or exposure to asbestos. dustiiK-ss. The degree of dustiness for each job category was determined after consulta tion with |>crsoiis familiar with the environ ment and conditions in the various work 6*0 ' VA. IT. Immt. 19U 386 LUNG CANCER IX ASItI. \Tus MIXERS Table I.--A*umber and Percentage Distribution TaUX 2.--Number and Pereealtuie Distribution by by Age Length of Employment Acs 9m..........*.................... ................................................................ IH ................................ IIU*n,,...................... ... .. AffriCt Aft......--............. * Lot mm *4%. NarnWr rtrCaal || 1||* | IM Unflhil CllpW|HM Nuibbm Armaa run el aaiptariMai....... Par Cam Jrt 40 It 10 * 1 too areas. For'the puquscs ot 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 Gitcgory I. uaily smoking more than five cigarettes per day. Persons who smoke |ipes or cigars exclusively were not considered to be smok ers for the puq>ose of this study. Table 5 presents the year-by-year ex perience of the cohort and indicates the Tame 3.--Number and Percentage DietAbutum . by Exposure Category IlptMIt CWIMI I................. .......... ,, n................................ . m....................................... . Oak asm................ ............ Tatala...................... Asmara Etpoiun_______ _ * iMituojt;. Minabar fat Cant Table 4.--Number and Percentage Distribution try Smoking Habits fCNfctOf Tawlr.... . NucaOT ...... ton Par C4K[ T3O1 im * U llvuli%. 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, hahit- 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 supj'ortcd bv an autopsy or surgical resection of the lung with microscopic examination of the re moved tissue. In one case so considered, however, diagnosis was confirmed by bron- T*tu S.--Ytar-by-Ytor Experience of Cohort and Death Rates per 100000 Han-Years of Risk Tme ACNMA.f\Atwintlififw 1H11tt0Is9OM3i3).......................................................................................... *^^*aaaaa.aaaaaaa*.. :IMCI3.M..M.0tIi4;MSoAJ; T<uh... ....... CaNMifwI.Mirflf 3t3tI t CtUM*C DMtk CtauP.inftwmrUltMrfrilf COWlhwM - 0*s1 JUS3ftO4T;t f MO *ntTnu ot IOD.OUO W ruk* ---- as Uakaam* 004f1t ,0 Ma1aRVuiai h t|3.i.UUn0)i 3.7MI.1 9JIU Twl'ns ot IVt,OQO at rbk M4 Ml 387 tkigt Dittributum by jymtnt Naatn 1.7BI UM wtx MB 111 U uu u rwcttn 40 It M 1 1 M ve cigarettes per pipes or cigars :red to be smokstudy.. ' ear-bv-year exd indicates the tagr Distribution If hr C4At f ^z7 Si from $[iecified as considered rimary cancer i showed that ported by an i of the lung n of the rco considered, med by bron- j i * But LALMjUCOQ1 A LLl>MXUJ BJ7U 611 St. A. ARCH117..V Of IXUL'STlUAt. lU.At.TU Tabu. 6 --"Pr.t' - '/ Primary Confer of the Lung > i5 s DW J-JIhW * > *13 AUbVpMf V** Yu N Yt Y Yr* Yi Yi Y > N N* Y** Yi Y No N choscopy with visualization and hit-. - another, although there was no atito, -. -.i< would be very* close to the 95c,b level diagnosis of primary cancer of the c of significance. However, having found iust seems to have been beyond question ; 12 cases, we arc not above this level, and The term "suspected" primary car,. - ol the lung was applies! to tho>e e.iv. f m which the diagnosis remains in dot:. - :-.ni some of the evidence points to cancer *: :Se lung. There were three ruch cases. The term "man-years of risk" h.> :<rn used to mean the number of men at r-k for the year under observation. A perron who lived throughout the year was coI as a full man-year of risk, but one who . ;d during the year was counted as one-ha:: a therefore the hyjothcsis that asbestos miners do not have a higher mort-V-ty from lung cancer than does the general ;-o'.iilntion can not be rejected. Xeverth'-!'.-. j. the occur rence of 12 cases in this sample would increase the rate to a point w f.-.'. 'n approaches the significant level. Because of the tre mendous importance of the questionable eases in this respect, some dr'ad regarding them will be given here. In one of these cases, the suspicion of man-year. cancer of the lung is based vy-n the x-ray Deaths occurring in the cohort, and :n which lung cancer is considered to h.-.-.e been proved as a cause, are shou u in T.-.: . 6. In Table 7 are shown three death* \\ r > have been considered as "suspected" lure interpretation, and. although *'< autopsy ss-as perfonned, the death ccrt:**'-'e indicates that death was due to lung ' -ncer. it is well known that the x-ray . -war.tnce of ' fibro-ts. especially if a loca: /**- density or cancer cases. a su|>rritnpo>ed tuberculous *: w* * pres An indication of the importance of those "suspected" cases in interpreting the re-:: of the calculations is desirable before :~~ther discussion of the mortality rates wh- -- are derivetl in later tables. For example. * happens that the rate found for the prove-* cases is close to the "expected" rate haso on the general population figures for t.-<: Province, as will be shown later, and cr this basis we should find eight deaths frrrr lung cancer among the cohort. Aetna'', ent. on simulate that of a * ,,r. lnd by itself, does tint justify the if* :-un ol" ***> case as one of "proved" lung. A second case was cer: r-*`- f the having died by rca-on of hydrothora / *.-->iblv due lo lung cancer, but again ***' 1V''1* no surgery and no posiin>>rl< *. * waminatmn. In the third case, although * ^subjected to aun*t'V. two patholog-:' > d- --f'ved as to whether hint cancer was jwrw"' "Fhc ilealh wa* ertimcd as having I...... d-<* ' chrome ^yfieafdiiis with nc|lir-<< imlmmiars nine cases were observed. If. however, trr And |nkm|iI|* ill* r.` * hc lung. 3 additional "suspected" cases were in On tin* tv** of these f.v** * ****** unssar- cluded, increasing this figure to 12, the tot.:. ranted ** mvhnte these ice among Ns At* I * Taux 7.--"SutprcttdT tmnkrr YYrh Y Ctpai Un f|Tt.. lIaU sa rr. u *t ,kr l.nnf I- s* * l-~KI ! *# IM fit J~. fmmr. lU 388 LL'XG CAXiT.R IX .Is IWSTOs' MIXHRS "proved" instances of luii|' cancer. On ihc other hand, they cannot. in fairness. he dis regarded completely. It is for this reason that mortality rates have been calcubtcd both ways. Table 8 gives the rates by age group*. The rates by length of employment are shown in Table 9. During the first 40 years of employment, the rate rises, an observa tion 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 man-years of exposure. When the "sus|ecled" cases are added, one case docs show up in this Taslc 8.--Lung Cancer Deaths by .4ge Groufs Taklt. 0 --l.unn Cancer Deaths by Len.jlli / Hmfi.-ym.-nt Nunfttr nl Pit1ww*% ansi Number mi Lunc Cancer taUpmbirNUelM I'tfIMI Ne.nf UntM rret4 Tetnl j1nf0t-*.1^f9ti..................................... ................ .............. 2.43ww0n3n ffff1tttt ft TMISfff1(t*tt . Annual ImcMCwanclewr iDc(ufftt.spRnaaluer*e per ioo.ooo UmiucI Fmwml Tefal H............. . so-......... tM....... ........ . ....... IfMtfafTtt Ift--MtoSff1tt ft4 Nuakr mi r<rMi and Xumtor ef Lmc Cancer Oculit Am Onvp tO-44.............................. O-M.............................. ^44 ................................ Ukian.____ ..... Ne.ef FertBus S.ftOI 1,I2 4U u 4 X*. d Dratta Teut ft i fIt f4t fffftttt T.CU___ ___ S.ftS* ft is Annual Uai Cancer Death date* per 100.000 Man Vcara et Ufatute Anmup fn%4 TMU fS4tffttH--*MI...*........................................................................................... ........ 11? ' 4144 Jt3ft OWT-UI............ ft4 period. This would produce a rite of 69 per 100,000, again demonstrating the im portance of these questionable. but un proved. cases to the final conclusion, because, if there * ere no cases in this number of men with lung cximsure. ami if asbestos is a carcinogenic agent, it must be concluded that these 240 men have demon strated considerable resistance. This is a bio logical phenomenun which has been observed previously and is consistent with the theory of an intrinsic o*- endogenous factor in can cer. The only other explanation would be that the susceptible members of this age group had died earlier of lung cancer. Table 18, which ap|>cars bier in this section, in- --7Vuou 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 Tabic 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 con nected to. lung cancer, we would expect that the longer and heavier the cx{o*urc. 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. Table 10.--Lung Cancer Deaths by Exfasure Category Numtar mi PcrMM ' fttfwttuiv Cautery I................................ II .................................... ni ...................... t'ubmirif.................. Tetali............ Nwmkr el Un( Cancer OrwM a N*e. el Itreene Nn. Dnihi . Frefe* Tetnl 1031 1.IU .m i 4 I t 4 4 4 I.W ft U Annual F.ifwuir Caieturf III.......................... -. III........................ Uuinum.. .... Overall, Ctnrer Dca<K Kate* per 100.000 Man*l*r a* Lapoaurc he*4 xt s Iftt n Tele xs SI XT ft ft4 643 389 j by Lcntitk ftC Ctmttt 0r*l^#4 t IlnlM i*4 TmsI 1 i 4 1 If , m too.000 IT 4 T~l 1 14 .I1 M intu % *4 s* Sc cohort younger 'exposure arc will be noted idcnce against : agent, for, if any wav conuld expea that exposure, the x found. The interpretation exposures were if employment, tr by ExfJjure ' -4 Ctmr DniM K*. ml QmiIu *4 Taut t4 t4 I4 ' ` ii m ioo.ooo Tm> aiKt U *U A. U A. AKCIIII I \ ill IXlH STKI.il. lll.AI.Tll Taoit II . L . r. t .m I'jn.ims f, ` ' J' 1 Taw. 1/ -Ciiiiv. /Vttik /it i#ui Mc*ntHnkt'rs f ******* .--:--------- -- " UpHklMM I 11 M l JM r-> IV-M i: t KM v" limit inn f tApetur* VLjt* I tI I I TM Tttftl 1.^1 U4 vn 4 a ni NtMMkr ( wl Sumter ( f.u4 T*mcf IV-M*** kf btM4tHg IIjImU Nt. ftf KlrttUt funwftt fraiH Ttui >mft|irt .... .......... TmbIi . . . .. 4.471 I.J44 a I.*u t 1 13 IS Ammm! U#| C .w*r (Wails Rale* prr IthlOOO *< f.|*wia bjr SftAMH ttfe*U Ni. #1 Or%iM I b which ca*e *'**'" ^ .'j^'lhow the I posure (Ca:vS-'ry 111' *vU' * . ' <ie.*ktf*........ .. shortest leng.n of empS-,^.. TaWcll < ****...... rn<H aos T*wl u which lists ;!-* number o ,***"> exposure cartes h, *- ^ - '^ o*t**n ment indicate-. that thi> ** curred. In ta.t. the au'u>" of employment tor ca.h <NV*.re catcgo., is almost identical. Table 12. which de\vh-;' lhe rat" . 'r smokers and nonsotoU- * striking smokers iim)' have included a larger percentag*- of young men. Coit'ctjucntly, ad ditional Tahl.-*, Id, 14. and 15 were con structed to 0,i,w the distribution of smokers and nonMi.ol cr by age. length of employ ment, and d- gree of exposure. Although It shows that not a cancer developed among *c " '.here are ilight differences, they do not ' account for the fact that all observed cases smokers and that all ca-c- of lung a:.'*r were in smokers. In respect both "proved " and ">upeu. ocsm to age n'.!e 13) the combined average "nosers. . .- age of the trookers was 4.9 years less than Table 12 "J' > triki.<< u "a hat of ti^- hoitsmokers. Table 14 shows that further \erihcanoi* "J> *. ' was possibc that *- " ___ ion may hue occutivd. t.{, the oo- that as far as length of emplovnirnt is con01 ?4ftL 14 --`.Mt/rff end Pfr<vnldl* PiffWMiflVH of Sm.' ktft and Somsmokcrt ^y LvngtU ... . i r T**^rUTN* V^ of Smokes -*- A **** Dutribu:i. C"`r! ___----- Lannli *4 Impl|rarK / Emfiioytburnl Kwmbftr Iftbitn SMMwkiri UMfwn 1 I ifi Qmup Sawiif C .......... . Ttuk........ otmo K............ IiMll 1 i*ri m et**r IM LM V4.................... O 4s I I tl.jm*Nur n ITT iII;MM Tk a XI Tm limn ftnf'i v *jei ija aipHirfDrf^ ... ITJ ui it41 4 tu Ttt* . fvrfttr* psM*****1 IfftlM k* 1 IMt i IS HA irr HI II 1 t - CilM m mo mo ti u *w-i hwup DttrtWliMi l^ncth ItHilf - Vftftimsirr W4..................................... it................... . ................... -W................... . m m................... ..................... . Ml ni u tJ * IT T9 4 U.T n.: ui i.t 1A T"--............ *% toor. I'tkMtA * 70 6 100 900 ft A in% mjSa. S'#/, /r. /<'. /o.< 390 i b LL'XC CAXCER IX ASULSTOS MIXERS TaMX IS.--Xtunber and Percentone DistrU'uti.m f Smokers ukd Ximlmtikcn by Exposure Category CtpMur* Ciumj I............. II....................... Ill .................... T.ult ... AttrUwW* It.p.B..Mu*L,, Somber fiUn NtNtMMkin m 4 au i MU i* IJ 4 * t a u Demography in the Provincial Ministry of Health. The data on total death*, death* from all [onus of cancer, and death* from cancer of the lung were obtained h\ sex and by county for the years 1950 through 1955. In addition, all death certificate* which sjiecificd primary cancer of the lung, and all those which indicated lung cancer but did not specify the origin, were exam ined for the years 1952 through 1955. tamuu OutnbuiiM Iiptiun CwiHjr III................ Ill_______ Utlo Inten Xammakin JiJ u.; 3C7 Cl t'ulfMn o fe.0 4*4 00 Tula.. ..... 100% wo% 100% Tabic 16 gives a tabulation of the number of deaths from lung cancer in the Province and in the cohort for the year* 1950 through 1955, and shows the annua! 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 cerned, the smoker* had worked about 2.3 year* less on the average than the non smokers. W ith longer exposure and greater age, one would expect the nonsmoking group to >how a h'njher rate if lung cancer were due to asbestos. Table 15 shows that the average exposure category was almost the same for the- two group*. 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 factor* 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.-- higher than the rate for the Province. When the "susjiected" cases are included in the calculation, the rate for the cohort rises to 33.8 [cr 100,000, which is about 50Co higher than die rate tor the Province. Thu. 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 part of this increase is due to im proved recognition and rcjmrting of lung cancer during the interval. For this reason, In order to make a comparison of the the years 1954 and 1955 were thought to be 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 more nearly representative of actual condi tions. Even so. it is quite likely that the general population i* not studied for lung cancer with the same diligence with which FmriMa T*ul h*td tuciiMliai uUm< Tails 16 --Comparison of Cohort with Province of Quebec fnm l.lW.ono * mf i.tn.ono luo IM 3 1 10) tut SB f 3 318 IttAI Cancer Dauhi UU IU1 1I8M tu an n tt i t i >u xs 303 till 117 I I au T*ut 1.034 13 IAU Aoruul * lUi* prr Hfi.OUO TtA 330 tu U tha rVt*rfv (Uurv*. it bu l*va uiuinrd all nuk lurtc cirtcaf duiht arr fur mtitaf 20 V _ * ApptvniMW mhliAHiiiini laumraifd |ai|NiUiwn iwr lUi, im |rpuUiA fc* IK4 (Rapport, Dir. 4a U Dt- amwnal. tNwmovf all** M r*hvrt al batmain* M 13.12* Broom--Troon 64$ 391 jl Ministry of deaths, deaths d deaths from sained by sex . 1950 through ith certificates cr of the lung, d lung cancer n, were examagh 1955. i of the number in the Province rs 1950 through ate per 100,000 noted from the rate for the is only slightly the Province, are included in the cohort rises 'ut 50fc .nee. This, e previous dis* he "suspected" uches but does vel. bservation from icd increase in or the Province is assumed that < is due to imx>rting of lung For this reason, re thought to be of actual condi - likely that the tudied for lung aice with which ...........Tul LCM Aiatul lUtr try wojOuu ttJk 09 3Z*U3 0lt. 4* to Oi MS At# Greui* *3-44 AMI *MT*t*U A. M. A. AKLItlfCS OF INDUSTRIAL UF.Ai.Tlt Tamx 17.--f.tmtf Cumeer Ucatht for the Province of Quebec EmIrmaI f TTT.ftrti JR.Mtlt 131.00 M37.UU0 Nukr at 1034 Tawl C*mftnl fpccmnl rnuurr TmaI tr : toi lit its l*m% ad tl U M U 130 Tout tl 43 *9 M lt 79 33 39 m T*t.4 Orttltai TtKil IT 0 mu U7 37 140 M 313 133 toss sptcift4 rmvr Tiul 17 33 71 II* 31 140 34 277 U3 i 8 I AttOrwp It -44........................ 43-34....................... AM4....................... . tH......................... . Of.*-all__________ D*uA lUln per 1034 Taial CmiAnl DnciAKl l-rtaurr Tatal fnirl Taut rmat 11 33.3 no 1.7 1.7 173 37.7 373 1.4 71J As 30*3 14 l. SI M3 n* t.T tt.4 U 1033 Total Cintltol !l*nlM Ifinurr Tatal rmi Tatal t.J rt.j IH ISJ V* 1.7 173 41.0 94.0 123 7.7 r.r 04.7 1333 773 13 13.1 4I-* 44.4 1X3 * Oiu tram UfJth ermAatrt. f Euinv* Ini obi tine I bf ifipiKlf); ltil pifMlam tar ( (Vbupt tor itikt ! ito c*ut popuUMMi tor IIM, u |lffl ! Rapt***, Oii.de U Umu(n|tnie. this disease is looked for in the miners, and This comparison, summarized in Table it seems probable that the mortality rates 18, shows that the observed number ot for the Province may be low. This would deaths in our sample is not significantly appear to be substantiated by the fact .that greater than the expected number of deaths, the reporting of cases in the cohort showed based on the average of the 1954 and 1955 no such increase over the same period. figures for the Province. It is true that, in Table 17 was compiled to show the an the case of the age group of 65 and over, nual age-specific lung cancer rate of cases the five deaths provide a figure which is in which the death certificate merely read almost significant at the 95Vo level. How "cancer of the lung." as distinguished from ever, it should be tinted that this number those in which the diagnosis was confirmed includes one of the suspected but unproved by autopsy, surgery, or biopsy. The term cases previously referred to. Furthermore, "specified primary" refers to those cases in it is rather likely that the rate for the these two categories in which the tumor was general population is understated in this I specified as having originated in the lung. age group, for the obvious reason that the It will be noted that, of the total cases .exact cause of death in the very old is not reported in 1955, a much higher percentage than in 1954 were specified as primary. The table also shows that a higher |>erccntage of the total cases ccrxificd in 1955 were proved, again indicating increasing interest Taslk l&--Comparison of the Actual ami Fxfelifd Number r/ Lung c oncer Deaths'by Age Among Asbestos Miners in this disease. A comparison has been made between the age-sjiccific 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 OAfwff# ' rta.im* Tail SiwiM rtplnitixIUf.UJLHUiJt* V3-44 43-M AH4 UalMmm 13 743 *7.0 ' 403 Obl *1 Of n MVin. r#f1* IWV.ilMat * fTMM **! 3.WI i.m 413 313 3 1 3 t 3 figure was higher and may have been ex ceptional. Ttaf,|frt minilar t> Awl AKa >' at IDa l*U met im illf nul M Ilf ITu.irvra at Miaiw. t AnaaUf tt.t. ml 64A FW. ITm /0<J \ LL'XG C.iXi r.ft tx A\nt:STOS M/XCJtS Tamx 19.--Ane Distribution of Adult Muirs fur Taru 20 --Anowit Dt'Oih Rutrs t*r lOftpOO fur the Hrminer of Qm-bct. 1951 C'llHCvr of Itn- Lun.-J Lumlda ApuOiuvp 0-S4......................... U44......................... +........................... TmaI______ Number rr.ua 1>.M4 IU.44.1 i.w.m . rmrnuta hmMM* t* Cv4mw( U It It It It It M1 mm tUppurt. IM4. i nutter of the same intensity of interest as it is in younger persons. Tabic 18 also answers a question pre viously raised. It show* that the members of the cohort have tint died from lung can cer at an age earlier than the general popu lation. and that such ail explanation cannot be offered for the absence of lung cancer in 240 men with more than 40 years of employment referred to on page 64.1. Before leaving this couq>arison of the Province with the miners, it should be shown that their age distributions arc 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 exacted that the oldest age group will be larger in the general [>puiation. The data presented in Table 20 indicate that the lung cancer rate generally decreases after age 70. There fore, we could expect the rate for all people over 65 to be smaller than the rate for the group between 63 and 75. which would apply to the oldest group of miners. It is felt that by using the whole adult male iopulntion. we have developed rates for the gen eral population which arc 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. u>iug statistical material from several sources. In one source. Phil lips '* gave age- and scx-.*jecinc rates for Canada for three j*criods between 1931 .aud 1952. The rates for males arc given in Table 20. These figures show strikingly the increase in rates between 1931 and 1952. and this AceOmup Uiutrr 3U 1*39 n JW-*4 U-At CO *4 even 7t*U *>-4 to* AH AM Ormip* Viin IMI-IVU t 3* 37 9.7 II.T HA 1.4 1 M. 11.1 -? 11.4 It 91 Of u A4 l?> IM T7 0 U.t U3 709 Ar.ltt IO T.I It taAw> ai?t ai m; T7A lost Hi U.t M.T no Ui * MMwuUtv ft*m l,uni Cimwct m tut * IMS. increase is iwrticularly marked after age 50, confirming an observation previously made, to the effect that until recently lung cancer, has prolxibly been underdiagnosed in the older age groups in the general popu 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 follows: Ac* Ctmtft 20-** !*< SS-44 4$ 4- Kjm S - 27 *S These rates arc, in general, lower than those develoftcd 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 and over, and it is quite possible that the rate for this group ntav have increased for Canada hctuccit 1952 and 1954 as it did for the Province of Queliec f Table 171. A further comparison has been made with an over-all rate obtained fram the American Cancer Society for respiratory cancer deaths in Canada in |953. This rate, for male*, is 20.8 per 100.000. or 5 more per 100.000 than Phillips' 1950-1952 rate, and compares with 25.3 |<*r 100.000 for proved cases and 33.8 |er 100,000 for total cases among the Bramr--Tnum 647 393 r.T IPOPOO for "tu*tda r 4 IttO-lkll IjB In4 M MI xr.a M.T TT4 ln> u TMIA 4." IM1 u IIS. ked after age ion previously i recently lung tndcrdiaguo-cd : general popu- poses of .nbine the >s in order to >ns used in this I.uions in each idicated is not approximation, e somewhat as s 17 49 Mil -al, lower than il (proved and iccr among the arge difference, of 65 years and e tiiat the rate increased for 1954 as it did (Tahir 17). been made with n the American y cancer deaths a* 'or males. . r 100.000 compares oved cases and ascs among the 647 A. At. A. AKClttriiX Ol` tXnUSTKl.tt. /II..11.Til Tavlc 2l.--Xumbcr of ami Dratk Rttlsi ft* 100,000 /v sftft* OVdufx f\*r thf Atiuit Malt /VfM/ifli.M of tiw (`mt*d Stairs* wav, and other countries, at least 50.0UU jicrsuns must be cxjwsctl thrniiglti<m the world, and it can be assumed that this Af Oihi ClMI KM* |Vf 100,000 number has been fairly constant in the 20 30-44 4S-M KMOIQ lUvVtkti *4 years since 1935 when the first case of i MS- I.XtMUJ it<a 44.4 IIU asbestosis with lung cancer was rc|xru-d. Tsui +4,41t.OO U.KV 17.3 At least 1,000,000 man-years of exjwurr has thus been accumulated, and this figure D4* tmm **>*! Sututta f im l'ua IMn,h VL 1 M4 2, IU3. ' can be divided by the approximately 150 cases of lung cancer with asbestosis re asbestos miners in this study. It is there ported during the 20-ycar period. This fore obvious that there are no important gives a rate of 15 per 100.000, which is at differences between the rates for asbestos least indicative that any lung cancel rate miners and those for the general jwpulatioii which can be calculated for workers ex of Quebec and the Dominion of Canada. posed to asbestos dust is not much greater Since it is probable that figures for the than that for the unexposed population. United States arc more complete and, there fore, possibly more comparable to the data for the miners, age-specific rates were com puted 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, arc 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, coni|arc 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 a>bcstos in one form or another (as distinguished from the gen eral population groups just discused, who have no exposure) an interesting observa Comparison Bctivccn Eight Counties Ad jacent to the Asbestos-Producing Areas and Eight Selected Counties.--To compare lung cancer mortality rates in the counties sur rounding the asbestos-producing areas with another group of counties in which no as bestos miners arc 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 Argentcuil, Chatcaugay. Montmagny, Tortneuf. Richiicu, Rivierc-du-Loup, St. Hyacinthc. and Terrebonne, mainly l*ecnue they represent a wide geographic distribu tion throughout the Province. The counties selected because of their proximity to the asbestos mines include Arthabaska, Deauce, Drummond. Prontcuac, Megantic, 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 jwpulat ion in 1952. To emjihasiac the conijarison. Megantic County has been shown scjwratcly, as has tion can be dc\ eloped by deduction. Hue- the Province of Quebec and also the Prov per** has stated that there are about 35,000 ince with the eight "asbestos-producing" persons exposed in the United States, and counties subtracted.. Because of its unique we have found that the Canadian mines lung cancer death rate, Montreal et Me de employ about 8000. Elsewhere. it has been Jesus has also been listed in order to provide estimated that the workers in England who further comparison. have cx|*'ure total between 3000 and 5000. It is apjiarcnt from the table that the With workers in Africa, Denmark, Nor- lung cancer death rate for the eight counties 64* . VoL IT. Jmme. 19IS 394 LL'NC CANCER IN ASBESTOS MINERS TaiLE 22.--S'umbrr of Lunn Cunerr Prolkj and Rate fer 100.000 Mnn-Years CMintto* Mronitf Cminir F-UM AdjMTIU1' CfMlfUkr* Euhl >*h*rirvt 4,'num* rrovmrw wm-tve irtc* ( Wurtsrr IfU fifW Mtttml( Ute am iciut Adult Mil* I'nfMtk n*n IttlJ U.iro f? hi mi I.IV1.IU1 l.iman tuo 3 3 life 100 3 (lit i 3 to 3 317 7 Mali Uun Canrrr laraim * ' -- - IV3 IM IM4 Ifttt 33 If 3 14 4 14 3 3tt 303 337 BA >: 3M 341 m in 1*3 333 (l It ywl th-u U nat time euim tiemtht weeumO after ace JO. TuJ ts 3 it 1631 IJftt no i" Ritt (r llO.IUi Ift t 4 . 33.4 233 immediately surrounding the asbestos-pro ducing areas is practically identical with that of eight counties selected for comparison. While Megnntic 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 tie 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 bestos-producing areas have any greater incidence of lung cancer than those who live elsewhere in the Province. Comment on All Recorded Lung Cancer Cares, Living and Decul, among the Asbes tos Miners.--Although a simple enumera tion of all the known or su-pected cacs of cancer of the lung in these areas ha's 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 fierind covered by the study, including one in which the diagnosis was mediastinal lymphosar coma. During the [criod covered by this inves'igation, there were nine proved cases and three suspected cases in the cohort. Through 1956 and to dale in 1957, there were eight deaths, six of which were merely suggestive of cancer of the lung and in cluded 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 x-ray only. In addition, there arc 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 4 that are still living. The remaining 19 constitute the total of proved cases of cancer of the lung among the aslwstos miners since 1940. The proved cases averaged 59 years of age at death, and varied between 37 years and 6S 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 ployment in the industry. Seven among those on whom such information is avail able had a weighted exposure placing them in Category III, ami six worked in an exposure represented by Category t. There were only 17 among these proved lung cancer cases in which we have in formation regarding the presence of asbestosis. Asbestnds was present in nine, although it was minimal in two. Two jwtholugists dix.ign.vd regarding its presence in another. At least seven of the 19 proved lung cancers, therefore, were not accom panied by asbestosis. Summary and Conclusions Interest in the question of whether there may be an association between lung cancer Braun--Truan ' - 649 395 ~1' ,~yflirt Tal M M W MM iy* 77t *l* ptf lao.uju IM f.4 .ft B. Si CJ e lung and in i as mediastinal na, cancer of the . abscess of lung. . One other was x-ray only. In ing four cases in knee is strongly T*-U is a total of .g 10 "sus.4 4 that are ;V 'constitute the incer of the lung since 1940. iged 59 years of between 37 years ting span covered minimum of 14 37 years. Only 25 years of cmj. Seven among ormation is availnure placing them ix worked in an Category I. nong these prosed hich we have int presence of as present in nine, in two. Two pathing its presence in of the 19 proved were not accofu "" ] ! I sions n oT whether there etween lung cancer M9 A. h. a. ARHurns or txnusrKun nn.ii.ru and exposure to asbestos has been evident since the report in 1935 by Lynch and Smith of a case in which lung cancer and asbestosis 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 de termine 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 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 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 six-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 s(ati>tics 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 650 was not |Missililc to trace 133 of tiu-se for the wlmlc period, but 5771 of the remaining 595S were found to be still living in 195.'' or later. Of the 187 known dead, cancer of tiie 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-four per cent of the cohort were more than 45 years of age, and thirty per cent hat! been employed for longer than 20 years. Thirty per cent had a weighted expo-ure which placed them in the category of highest ex posure. The mortality rate tor lung cancer, as computed on the basis of lime "proved" deaths among the cohort was 25.3 per 100. 000. When the three "su>jectcd" cases were added, the "total" rate for the cohort rose to 33.8. The importance of the suspected but unproved cases in determining these rates has been reiterated because it is likely that such cases would not be included in the statistics for the general population and because they influence the results so mark edly. ___ According to the findings in this study, the mortality rate from lung cancer docs not appear to increase with length of ex posure or with degree of exposure, a fact which presents strong evidence against the carcinogenicity of --- Comparison of the experience among the asbestos miners with that of various seg ments of the uncxposed, comparable popu lation siiows 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 |*cr 100,000) <,oui|iarcs well with the rate of 22.5 per 100,000 for the rvt of the Province, and 20.8 per 100.000 for adult males throughout the Duminiun of Catrula. It al>o compares satisfactorily with rate* _ Vt. 17. 1--t. 396 Lt'XC C.tXCl.K IX .ISIIHSTOa MtXllKS of 37.2, 25.3. ami 2S.0 obtained front varionsources for adult males in the L'liucd State.-. Finally, in this matter of cumpari-oit, it would ap|ar that the world-wide e.\)*ericuce of persons exposed to a-liestos du>t is not worse with respect to lung cancer than that of the unexpused [>opulation. The comities surrounding the a-lesto>producing areas, in which it is pre-umed most of the asbestos miners live, have al most identical mortality rates with tho-c of eight counties widely scanned through the Province, and arc lower than those for the remainder of the Province, and much lower than the rate for Montreal. Since 1940 there have been 19 cases in which the diagnosis of primary cancer of the lung may l>e considered to have been proved. Approximately half of those cases were associated with asbeslosis. 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