Document Ka0wJB59er7XZrZjraGj3Y7o

16. Ac ? Number of Person* and Number el Lung Cancer Death* by Length el Employment Length Asbestos Thet'erd Mines Combines oS Lor.; Lung Cancer Lung Cancer Employ Cuci Deaths Deaths ment Persons Deatn Person Proven Total Persons Provec Total 5-9 lQ.19 20. 2* J0-3? 40.49 sC* Total eso 8M 342 168 l? '2 TITS 0 915 ft 1834 1 JSC 2 43 J Q 16S 0 S3 T leaf 0 1 2 3 0 0 6 0 1795 0 1 2398 1 2 922 3 S 603 5 1 IBS 0 0 55: 0 9 T5TS 9 0 1 3 7 1 0 71 Annual Lung Cancer Death Sates per 100, 000 Man. Years oi Exposure by Length of Employment Length el Emolovmer.t 5-9 10-19 20-2* 30- 34 40.49 SO* Over-all Asbestos Total 0 0 49 198 0 _0 22 Thettord Mines Proves Total 00 U 11 57 57 115 192 0 99 00 27 41 Combined Proveo Tota, 00 77 54 54 138 193 0 50 00 25 34 0170 Number of Person* and Number o' i-urtg Cancer Deaths by Exposure Category Expos* ur Cste. IOTV Asbestos Thetford Mines Combines Lung Cincer Lung Cancer Cincer Desihs Eeaths Persons Deaths Persons Pro'vcd Toni Persons Proves Total 1 11 1U Unisiowu Ton] 969 564 735 5 2173 2 1062 2 1 1586 2 0 1037 2 0 00 T 3665 6 2 2011 4 4 3 2150 3 4 4 1772 2 4 0 50 0 9 5956 9 12 Annual Lung Cancer Death Rates per 100,000 Man*Ycars of Exposure by Exposure Category Exposure Catcgori Asbestos Total 1 11 m Unloxown Over.all 34 30 0 0 22 No one exposed Tnetfore' Mines Proved Total 31 21 32 ' 27 31 32 64 0 41 Comb; r.ed Prove; Tau; 33 33 23 31 19 37 0 _0 25 34 0171 <0. U exposure to asbestos :* a-. ar.y way connected to :ung cancer, w* would expect that the longer bad heavier the exposure, the higher the rate that would be found. The only possible error is this interpret*, non could occur if the weighted exposure* were inversely related to year* of employment, in which case the heaviest weighted exposure (category 111) would show the shortest length of employment. Tables 9, 10, and 11 which list the number of persone in various exposure categories by length of employment indicate that this error has net occurred, la fact, the average number of years of employment for each exposure category is almost identical. TABLE 9 Number of Person* it. Various Weighted Exposure Categories by Length el Employment Asbestos Length of e;a,0'.ment 5.9 10-19 20-29 30. 3* -iO.4; 50 . 7 otal Av. Yrs. of bapeturt We it it ed x?csur Caterrrie t i u in 2a 273 159 9d 9 ___ 2 $6? 15.5 213 217 19 42 ) ___ 0 JoH 15.2 219 373 92 27 4 0 735 H.5 Unnnowr. 0 l 2 1 l J, ' $ 29.0 Total so 64 342 16B IT 2 2271 IS. 1 T 0172 / 41. TAB L 10 Number of Ptraon* in Varieue wanted Exposure Categories by i.CA(tti of Employment . Thetford Mine* 'Length of Employment M 10-19 20-29 >0-19 40-49 50 Total A*. Yrs. of Exposure Weighted Enoiure C*tt*3f iei -L _U - -Mi Unknown. Total 279 390 155 H9 67 22 1092 19.9 >85 868 274 176 64 21 15*6 18.7 251 476 151 110 37 10 1017 18.1 0 0 0 0 0 0 -'0 915 1514 580 435 168 53 3665 18.9 TABLE II Number of Per torn in Various Weighted Exposure Categories by Length of Employment Combined Asbestos end Thetford Mine* Length of Emoloyment 5-9 10-19 20-29 J0-J9 40.49 50 t Total Av. Vr*. of Exposure Weighted Exoosore Caterer-let 1 il 111 Unknown Total 70: 663 >14 247 76 ___ 24 2031 17.8 598 833 >63 218 67 21 2150 17.8 490 851 243 137 41 10 1 772 16.6 0 1 2 I 1 0 5 29.0 1795 -2398 922 . 603 185 55 5958 17.5 4i. Table 12, which develop* the rate* (or smoker* and non smokers, is most striking, It shows that no: s single cose of lung ^' cancer developed Among the 12bS aonsmokers end that All esses of lung cancer, both "proved" And "suspected", occurred ui smoker*. A compsrison of Tables t And 12 certainly suggests thst smoking is a greater haaard then exposure to Asbestos in tbe mining operstion*. Table 12 was so striking thst it was felt tbst further veri- ficAtien was necessary. it was possible thst some abnormal distri bution rosy have occurred, e.g., the nonsmokers msy beve included A larger percenlAgt of young men. Consequently, Addition*) Tables, 13, 14, And 15 were constructed to show the distribution of smokers end nonsmokers by Age, length of employment. And degree of exposure. Although there are slight differences, they do not Account for tbe feet thAt All Observed esses of lung cancer were in smokers. In respect to age (Table 13) tbe combined Average Age of the smokers was 4.9 ysars less than that of tbe aensmokers. Table 14 shows that as far As length of employment is concerned, the smokers bad worked about 2.3 years less oa tbe avenge than tbe nensmektr*. With longer exposure sad greater age, one would expect the nonsmoking group to show a hifthcr rate if lung cancer were due to asbestos. - Tabic 1$ shows that the average exposure category was Al most the same for the two groups. Therefore, this variable seems to be of no importance in accounting for the difference between lung cancer death rate* for smokers and noasmokers. 0174 43. TABLE U Number of Person* end Number of Lung Cancer Death* by Smoking Habit* Abc*to Thetford Mine* Combined Lung - Lung Cancer Lung Cine e r Cancer Death* Deaths P*ron Death* Ptr*on* Proved Total Ptrtsn* Proved Tote: Smoker* 1931 Nonctnoker i 340 1575Unknown Total 2 3 0 0 1 2742 92S IS 3685 6 0 0 V 9 4673 9 12 0 1265 0 0 0 . 20 0 0 5956 9 12 Annual Lung Cancer Death Rate* per 100,000 Man. Yeart of xpoure by Smoking Habit* Smoker* Noa*mokcr* Unknown Over-all Abe*to* Total 26 0 550 Thetford Mine* Proved Total 36 55 570 0 00 41 Combined Proves Toni 32 -43 00 00 25 34 0175 c ei c |*M to -a - -- I P5 *1 =ii mw: C n --* A A jI --5 |1 ap to id/ *j ** -- IN ** to X9 0 ^ f* 9 o s S ^^ * X C9 0 N *CC9* ---V N*toJ ** lO C* VI* < to -- M (m < k\ >* 9 0 * *--9 e -- wt ^ Ic* e Vi 0 5 gi 2 ^0 jrto* tpo* too ^ sr---------- Olir to C' .> *z 9 c c ^<c* tr> ^i * 5s I <9 H 9|c *-. 9 S M|*N * *4 * * 0 vs -- -- * -- 0* 9* V to *e e co jV> to !=> I -- -* e o t** 9B IS 2 oI* *o o to 9S S /N 0 9 o z9 'Nto ^ <N 2^ v c it v !-0 -* *9 O i o 4% * j^ *i * "j 4* ** to 9* ` * -- t.cfc* lim n . 1`>>% M < S< O -- to ^ ti to/" *+ * b 3jc 2 9* SJ yo <o t*too4i **ttoo*io*tot j^* 3*s-* *--*3; 0176 1 45 * * 4 s E* ) c X e ;! - Ad ta it*N X9*k # a P * it J' . jct o 9**ta g s - " Ad s ji'-/ |= * ( Ti b gi X cz 0 V I|*S* *-waj PP XX 4% *4 A< g 7 s X 0 c 0 ( Z JtVCa AJ Mt _ m ta*. -- iSC Q c C u_ to XV 0 X4 AAt e 1m*, At r 9 .U w u ta tJ ta m ta A- x 4- a 1 \ z ta zr * 1 | i t P * * X X 0 10 c ut * 0 * e o >k Dc e 0 X t *A * ta V cc V _! s 6<* oci XV 0 4c ae ** #* A4 wt Xta A* AA|jJiAO. At " * o A ta O x #A A -- [ 0 J X i c e > X Ad c * * e o X 6 X * * tad c to- ta je c I *5 ce Jf X M c *N X P X * tO ta - w x* 0 c * < b e 2 1. x * 5 mc i * # * t ow X0 J X00 mmm mm XAd AoJ tpa mm Aftmat #4 A* c e b c A mm e O (<* 9 X* o 2 e9 * ta V XVta 10 , <taVt W tar ta ta* At t ** X c e 4*. 4 * * ' 0X JC"-t m m ** < o m O m X z3i V 3 g y* V* ta Xta #* mm * $ A P < *t>a A 6 IS XA m 0 z ta XV * P p #A jt tat tai e 44 < * x c zs XV r*d gw Ata* tpaj ata? mm AJ - Pta* to ' .o Mc X A, fA <iO * *. 4 to - w0 it e X a di eV " Js gs p W 9ri ST m* ta ta P9 * H X f #> -3 < j I V e" ta * 0 > m06* J V * '2 ta * P1 P AJ At . ta *o * 9ta 9 tea tat 3' 0177 -46 ess s * jie j- f [s 11 *J "> T I -- Z *4 ** 39V . Z 9 : rN+ t^f O+4 C * 4> 9 /t*/* 4--S0* *m*4 V m* *4 ir -- ^ ^ . s 9 U r tveV 99bM 'e iI ,3 e 0ax in U >> X e4 cW^O e 1-- u 2 sv 40 SI C ^ f 01/ c Jl *4 4*0 * zo b * em *uit o V) V 9 2 9--0 ^ c g *- ^ JICf ** *r <m AI c e e o|^ : *oo c i^> if* 9 <3 3 Jt /I i * ^ * 9 9 *3 *\ ff* 9 2 '* a* *4 s . *V9 e^. **4 **J|O ** * I-- c. Li--h *j u-91l ss ** 0178 / / r. The remit of this addition; analys;s is tha: none of these laetor* appear to lessen the effect of Tabic iZ. which is therefore strongly suggestive of the importance of smoking a* compared to the other variable*. Asbestosis and Lun; Cancer ( When we attempt to relate the lung cancer death* occurring in the cohort with the reported ca*e* of a*be*to*i*, we are immediately aware of a disturbing inconsistency. Various authors report the incidence of asbestosis alter 10 or IS years of exposure a* exceeding 50%, and in one study, a* high a* 8?%. However, data on cases of asbestosis from the cohort* at Tbetforo Mine* and Asbestos pro duce a rate of only about 5%. It is true that these data are based on only those cases which have been proved at autopsy, and those whose most re cent x-ray interpretation resulted in a diagnosis of asbestosis. This in cidence may be far lower than if based on microscopic examination of the lung tissue. A* a matter of fact, Or. Cartier has estimated that there are probably 300 workers who do not show radiological evidence of asbestosis, but who have some degree of fibrosis. He also estimates that these ate perhaps 40 workers who may have died or retired with this disease. Instead of 143 cases of asbestosis in the whole working force at Thctford Mines, c. we should then have perhaps 500, but even this would result in an over-all rate of less than 10%, which is far below those widely reported. In our 0179 48. combined conort, there ire 1745 men who hive had more :har. 22 year_9f employment, and 431 of the it have worked in the heaviest average exposure. According to the records, we can account for only 136 cases of asbestosis is the combined cohorts. If even 25% of the workers with more than 20 years'exposure develop asbestosis. we should expect about 425 cases. This leads us to believe that there ie a very considerable under-reporting of asbestosie. Such a hypothcale is easily conceivable when one considers that many chest x-rays in this group may he considered normal by comparison with others 3r in the same group whereas, if they were to be compared with wha: arc considered as normal chest x-rays elsewhere, they may be inter preted as showing fibrosis. Cases of asbestosis which were accumulated from the au topsy records and from the periodical physical examinations result m . a distribution which is shown in Table 14. TABLE 14 Distribution of Accorded Asbestosis Csses In Cohurt Living Deao Total Asbestos IB 4 22 Thctfotd S4 30 114 Combined 104 13d .1 \ 49. TABLE Naasbtr of A*bc*;a*is Cates By Length of ploytaea: and Exposure Category Asbestos .Length of Entolovmeat Lt* than 10 10-19 20-29 30-19 40-49 50 Total Av. Tr*. of ClSplOJIBESt Exposure Cate e orv I II m 0 0` 0 01 2 27 4 01 4 00 1 00 0 29 n 25 25 29 Cnietowr. 0 0 0 0 0 0 0 -' Total 0 i li 5 1 0 22 27 Percentage* of Asbestos!* Catet By Length of Zspiaytsont and Zxpcsur* Category Length of Emplovrr.ent Enoiurt Catesorv 1 U Ill Lett than 10 10-19 20-29 30-39 40-4 50 Over-all 0 0 1.3 0 0 0 .2 . 0 .5 7.9 2.4 0 1.6 0 .5 4.3 14. S 25.0 1.5 * No one exposes is this i r -? Unknown 0 0 0 0 0 Total 0 .3 3.6 3.0 5.9 0 1.0 01S1 so. TABLE ;7-PortU - Number oL Aabettoti* Cum By Length 0/ Employment ud Expotur* Category Thetlerd Mice i Length of Err.olovTr.eRt bill than 10 10.19 20-29 30-39 40-49 ,50 * Total Av. Yr*. ot Employment Zjcoosurr C*t*orv _ m 0 0 '0 01 7 2 5 21 2 15 33 0 6 20 02 2 4 29 S3 30 36 34 Unlmowr. Total 0 0 0 0 0 0. -o 0 s 28 50 26 4 116 34 Percentage* ol A*be*toii Cate* B y Length ol Employmeet arc Expeturt Ca::tgory Length el Employment Exsoture Catecor V 1m Le* than 10 10-19 20-29 30-3 40-49 50 Over-all 00 0 0 .2 1.5 1.3 1.8 13.9 1.3 S. 5 30.0 0 9.4 54.1 0 9.5 20.0 , e 1.8 S. 0 * No one expoted in tbi* group Unknown * 0 0 0 0 * 0 Total o .5 4.1 11.5 15.5 7.3 3. 1 0182 SI TABLE 17- Pert .IE Number 0/ Atbettoeit Catet By Length ot Employment end Expoture Category Atbettoa end Thetford Mine* Combined Length of Employment Lett then 10 10-19 20-29 30-39 40-49 SO Towl Av. Yre. of Employment Exposure Cateeorv jl . - iii 000 029 4 12 25 2 18 37 0 8 21 22 6 3$ 94 2S 33 33 Unknown Total 00 0 11 0 41 0 S5 0 27 04 0 : 138 33 . Percentage! of Atbctt oti* Cetet By Length of Employment anc Expo tore Category Length of Emplovmer.t Exooture Cateeorv -i JL U1 Lee* then 10 10-19 20-29 30-39 40-49 SO * Over-ell 00 0 0 .2 1.0 1.3 3.3 10.3 .8 7.3 27.0 0 9.0 51.2 0 . i 20. 0 .3 1.8 5. 3 * No one exposed in tbit group UnJoown 0 0 0 0 0 Tote! 0 .5 4.4 9.1 14.8 7. 3. 2.0 0183 u. A percentage incidence of aibeitosu :'or i<c: expoiure cate goryji** ;ti: eeve.eped a* well a* for tied per:ec of employ ment, Tbit uu'er.-Biudn i* *hown m Table 17, It trill be noted tbit within an expoture category, the incidence rite* with incrc**ed length of employment, It it nits apparent tbat tbe incidence*, even in the category o haaviett *xpoeurc, arc far below tbe rate* found by tbe author* preyioutly re ferred to. It item* clear, tbat unlcs* concentration* of aabesto* du*t to which tbe miner* are expoted are very much lower tban tbote which ootam in all tbe other ttueie*, there baa been a'gro** under reporting of tbe a*beatoi* cate*. Tbe obvbou* rc*ult i* * higher relative frequency of lung cancer in a**eciauen with atbeetoti*. Table 1$ compare* death* due to lung cancer and fatal caie* with atbettoti*. alone and m combination with each ether. TABLE 18 - Part 1 St* tie tic *1 Analyti* of the Cau*t* of Death Atbciio* Caute Abc*tOi No Abcto*:* Total Percentage Lung Cancer No Lung Cancer Total Percentage 1 ( if) ItJ.S) 7 t.i 2( i.si _aj Hi.2) as 91.8 J 6.1 i ?s.9 49 Figure* in parentbeti* are the '`expected" number* 0184 \v = * 4 .r' 51. table is . ^ Statistical Analysis of the Cause* of 3e:i Thctford Mint! Cause Ai6r.on> No A*bestasis Toni Percent see Lust Cuctr No Lung Cancer Total Pircnu; 3< 1.3) ,25(26.7) 26 21.2 3{ 4.7) IQi (99.3) 104 7S,S 6 125 132 4.5 95.5 Figures in parenthesis ore the "expected" number* Table is . Fart m <` Statistical Analysis of tie Cause* of Death Asbestos and Tbetford Mine* Combined Cause Asbestosis No Asbestos:* T0tl ?ersen:a-e Long Cancer No Lung Cancer Total Percentage 4 ( 1.5) 28(30.1) 32 17.7 ii 7.4) 144(141.6} 149 62. 3 9 172 isi 5.0 95.0 Figure* in parenthesis ere tbe "expected" number* Sin death* from unknown cause* not included Tbe ntun'oer of lung cancer death* combined with asbeitosi* i* larger than would be expected in each cohort and in the combined cohort*. Thi* difference ie significant at the 55% level using tbe ehi- square test of significance. The importance of the under-reporting of asbetto*:* can be observed in Table (9. 0165 u TA.BLZ l* Statistical Aaalysis of tbe Causes of Death if 20 Nonasbestosis Cases bad been Diagnosed as Aabeatoaia Cases Aibcstogn No Asbestotis Total Percentage Lusf Cancer No Lung Cancer Total Percentage 4( 2.4) 48(49.4) 52 23.7 5{ i.4> _14(122.8) K9 71.3 9 172 i#i 5.0 95.0 Figure a in parenthesis are the "expected" numbers In tbia table, it baa been assumed that 20 o the eatei which did not bare lung cancer and which were reported to bave no aebeetoti* did. in fact, bave asbestoeie, tbe diagonal* of which was missed. Although tbe caae* el lung cancer with aabeatoaia are still bigber than would be expected, tbe difference ta no longer significant at tbe 95% level. Tbia atill ia true if fewer than 20 caaca were shifted, but it ta reaaonablc to expect that at least 20 of tbe 144 might have bown aabeatoaia bad they been subiect to autopsy. On the other band, a abaft of about 40 cates would produce an expeeted rata almost equal to tbe rate found. Explanation of tbia effect of under>reporung of aabeatotia baa been t'.retted because it seems so obvious that ia under reporting aabeatoaia tbe ttUticnsnip between it and luag cancer baa been made to appear more significant than it probably is. 0VP6 1 t 55. i t *! Four of the proved cases of lung cancer ard set of the suspected were associated with asbestosis, Since we have cr_y 3; deaths in which asbestosis wu present according to the records, the incidence in this series is 12.5%. wnile this is slightly fewer than the rates found by Merewctber, Gloync, and Wtdier, it is still much higher than could be expected if the atbeatosis incidence were anywhere near the experience reported by other authors. c Comparison of the Cchatt Dxgerienct with, that of the Province of Quebec. Dominion oi Canada, ane the United States i T#'* 1 la order to snahe 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 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, and all those.which indicated lung cancer hut did not specify the origin. were examined for the ytare 1952 through 195S. Table 20 gives a tabulation of the number of oeatis from lung cancer in the Province ana in the two cohorts for-the years 1950 through 1955, and show-* the annual rate per 100,000 in these segments. ___ 0187 Restricted Copy 31 confidential PLAINTIFF'S EXHIBIT X/fP77 INDUSTRIAL HYGIENE FOUNDATION OF AMERICA, INC. 4400 FIFTH AVENUE PITTSBURGH 13, PA. AN EPIDEMIOLOGICAL STUDY OF LUNG CANCER IN ASBESTOS MINERS Report to QUEBEC ASBESTOS MINING ASSOCIATION Quebec, Canada September, 1957 (50 Copies Reprinted January 10R'V' Induitriil Kyjicac F&urtd* rion Qi Amenc*, Iac* 4400 Tilth /iveftuc _ PiKthufiih 13, Fa. (?/bcr Trteso^M- IT7 - e%1& AN EPIDEMIOLOGICAL STUDY Of LUNG CANCER ' IN ASBESTOS MINERS For k QUEBEC ASBESTOS MINING ASSOCIATION - Quebec, Canada July, 1956 to July, 195? ] By Daniel C. Braun, M.D, Medical Director 1 September, 195? By: C, Richard W,\lmer, M.D. Managing Director 012: iV TABLE Or CONTENTS Pi|t Foreword................................. _............................................................. i Glo***ry................................................................................................... iv ( 1. Introduction.............................................................................................. 1 XL Critic*! Review of Literature................................................................. 5 III. Principle* of tie EpiocaiologicalMethod ....... 13 IV. Collection and Analyit* of Deu.................................................... It V. ReaulU *ad Interpretation .............................................................. It Aebeetoeif and Lung Cancer. ................................................ 47 Compariaoa of the Cohort Experience with that of the Province of Oucbec. Dominion of Coned*, end the United Sure*................... 55 *I Companion Between Eight Countie* Adjacent to tbc A*be tie*-Producing ` Are** and Eight Selected Countie*...................................... 66 Di*cu**ton of AU Recorded hung Cancer Caiti, Living and Dead, at Atbetto* and Tbetford Mia**............................................................................. 6# VI. Summary and Concluded* ............... ^ VI!, Bibliography.................................... ?t 012S FOREWORD The success of a study of the type herein reported de pend* very greatly upon the availability of data from many sources, end the assistance end cooperetion of those in possession of these dete. Industrial Hygiene Foundation we* fortunate in having the wholehearted cooperation of the asbestos-producing companies, and particularly of their medical and nursing personnel who have the responjibility for maintaining the medical record* of the workers. In this connection, we are especially indebted to Dr.aui Cartier and his staff at the Thetford Industrial Clinic, and to Dr, T, R. Grainger and the nurses at Asbestos. AH records in these two medical cen ter* were put completsly at our disposal, and the care and complete ness with which they are maintained assisted considerably in the preparation of the material relative to the worker population. Data on population figures and on the causes of death in the Province of Quebec were obtained with the utmost assistance and co operation from Dr. Paul Psrrot, Head of the Department of Demogra phy in the Ministry of Health. Not only were all vital statistics and reports made readily available to ut, but Dr. Parrot and his entire staff rendered valuable assistance in many ways, including tht location and interpretation of death certificates. Especially helpful in this part of the work was Miss Gauthier of Dr. Parrot's staff. The same helpful u. cooperation wi rendered by Messr*. Hardy and Hopiun* of the Stc Lif* Assurance Company of Canada in Montreal. who made available their record* of the death claim* paid under the group policy cover ing the worker* at A*be*to*. Valuable suggestions lor the conduct of the *tudy were made by Dr. J. A. Vidal, Chairman el the Silico*i* Board, and Dr. Guy, Paihologut lor the Board, a* well aa Dr. Gregoire, Deputy Min ister ol Health lor the Province ol Quebec, and Dr*. Simard, Duiresne, and Greuia, in Montreal, ( - . Statistic* lor the mortality rate* lor the Dominion ol Canada were obtained through the kindness ol Dr. Dean F. Davie*, Administra tor lor Research on Lung Cancer lor the American Cancer Society, and those lor the United States were graciously lurnished by Mis* Curalnick in the National Ollice ol Vital Statistics, Department ol Health, Education, and Wellare ol the United State* Government. Finally, the very great assistance rendered by Dr. Kenneth W. Smith, Medical Director ol Johns- ManvUle Corporation, and Mr, Ivan Sabounn. General Counsel lor the Association, in making the necesaary contacts, in travel arrangements, and in so many other ways, is gratefully acknowledged. The methodology of this research is believed to be un.qut among the reported studies of lung cancer as related to asbettosi* and exposure to asbestos. Assistance in planning the study in such a way as 0130 // IU to ***ure ** proper epidemiologic*! Approach, and *11 bio*t*tsttic*l *pplie*tiOM of the finding* were provided by Mr. T, D*vid Train, formerly of the Gr*du*tt School of Public He*lih. University of Pitt*, burgh, bad the At*ff of the laduttriAl Hygiene Pouadstioa. . The report it believed to present the finding* in *a objte* live meaner *ad is respectfully submitted for the consideretion of the Association. I IV, I- glossary For the purpose of clarity and uniformity, tie tc r-- i used is this report ere herewith defined according to the muter of their use. As he tto) workers: Worker* exposed to asbestos dust in other than mining operation*. Asbestos misers: Worker* engaged ist the mining and prepare* tioa of asbestos is. the areas under study. Asbestos:*: A generalised fibrosis of tbs lungs diagnos- able by x-ray, or by microscopic examina tion of the lung tissue, but not necessarily accompanied by symptoms or By disability. Cohort: a segment of the population, defined accord - inf to certain criteria, and representative of the whole population. Specifically m this study, s group of asbestos miner* having at least five year* of exposure in the industry and who were in the industry during 1950. Lung cancer, cancer of the lung: . A neoplasm of the lung or bronchus, wher ever situated, and including adenocarcinoma, squamous cell, and undifferentiated, round, or "oat cell" histological types. Primary cancer of the lung means such a neoplasm originating in the lung, and not secondarily in the lung as the result of a metastaais from another primary location m the body. Smoker*. As used in this presentation, the term smoker refers to t cigarette smoker, habitually smok ing more thin five cigarettes per day. Persons who smoke pipes or cigar* exclusively were not considered to be smoker* for the purpose of this study. 013 I. INTRODUCTION Tver ttiet the pronounced increase in tht incidence el lufif cancer among mates bMune apparent, there have been attempt* to associate it with eat or another of the veriou* element* in the en- yirearn eat el man. The approach used by *enve worker ha* been to suspect eae or aeveral *ubtaaee* aad then set about ia an intensive search lor lung cancer among persons who have had any exposure to these compound*. Is this connection. Smith writes; "The tea* deney of aathors reporting tht coincidental occurrence of primary iimg cancer with silicosis or with any other theoretical etiolegic con* ditieat, has been to emphasise the percentage relationship is extremely small series of caste, with control cases which are not in any way comparable." It would teem inevitable that asbestos should com* under scrutiny in this manner, because prolonged exposure to tbit material it known to caut* a tpecific type of pneumoconiosis, and because persons who show this form of pnsumccoaiosis often come to autopsy and pro* vide a ready source of material for study. It was in this wsy that re* ports of the timultaaeous occurrence of lung cancer and asbeetosi* be* |an to accumulate alter the report of o case by Lynch and Smith m I9JS. Within the neat tan years, about 15 additional caac* were reported, and m list Mcrewtiber reviewed all death* from ssbettoei* re corded in England eisc* March, 1921. Lung cancer occurred, according 2. to Merewetbtr, m 13, If* of these eases. Continuing this study to include December, 1954, Merewctber counted 55 cases of eucet of the lung utitr.j 344 coses of asbestos!*, raising the incidence to 16f. 192} Cloys*, whose work is Also frequently referred to os establishing a connection between isbestoti* and concer of the lung, reported in 19S1 the results of his findings on 1205 autopsied coses. This series included 132 Asbestos workers, of whom 121 showed osbestosis. Cancer of the lung was present in 14.1% of these osbestosis coses. In 1941, Nordmonn and Sorge claimed to have produced Lung eancer in mice which they exposed to asbestos dust. ~ Since 1951, additional coses of conccr of the lung coexisting with osbestosis have been reported, and, according to Kueper 4t>Out 109 ouch coses hod been reported up to 1955, As o result, on associa tion between the two diseases sppeors to hove been accepted by many authors and several writers were using the term "osbestosis cancer" of the lung. Werber m 1952. stated categorically that in 7% to 17% of cates of asbettons, after a latent period of about 1 1/2 to 20 years, carcinoma become* established in tbt lung. On the other hand, not all authors accepted the alleged associa tion without reservation. Saupe ^ ^ in 1939 had reported that be had discovered no cases oi iung cancer among tlC cases of osbestosis which he had examined; and in 1942, Kollcb and Angrtst expressed the opinion that the number of eases of asbestotts with lung cancer was too 0134 3. mill for statistical evaluation. In ld47, Wegelius reported 126 radiological! y eiagr.osed cases of atbestosis among 476 workers in fia-and, and found no eases of lung dancer in this group, Goldblatt and Coldblatt in their section of Mcrewethcr'e latest book, state: "But at no stage in all these impressive researches was any clue obtained whicb might have offered any support to the pot si- bility that asbestos could act as a carcinogen. There is no reliable criterion by which one can anticipate carcinogenicity and, as is well known, relatively minute changes in the structure of a chemical ear *, cinogen are sufficient to diminish or eliminate carcinogenic action. If asbestos is indeed to be regarded as a carcinogen, the need is felt to demonstrate tome property which cen 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, asbestoe might be conaidered aa a "co-carcinogen" which only induces a further development of a pre- neoplatue condition brought about by something independent of the as bestos, such as an endogenous factor. Thus the literature, while tending 10 support the thesis that asbestosis is in some way related to the development of lung cancer, is by no means unanimous. Altogether, it is perhaps more confusing than enlightening. Meanwhile, the Canadian Johns-Manville Com pony in Asbestos na* been alert to tbe whole problem, and it the Tbetford Industrial Clinic, Or. Paul Cartier *u studying the situation trnonj i working population 0/ about 6000, and made notable eontributiona to the literature ju*t cited*42*4**. Between these two areae, a number of eaee* bad been recognised and ubulated by the spring of 1956. At this time, at the tuggcetion of Dr. Kenneth W, Smith, Medical Director of the Johns-Manville Corporation, and Dr,Cartier, the Quebec Aebettot Mining Association approached Industrial Hygiene Foundation to determine whether it would be feasible to conduct an epidemiological study in order to discover whether the incidence of lung cancer was, in fact, greater among asbestos miners than among tut general popula tion, and whether there was a correlation between lung eaneer und the disease atbettosis. The Foundation submitted, in March, 1956, a pro posal for such a study based upon a preliminary survey of the type and accessibility of data which might be available. This propotsl was ac cepted by the Association through its Secretary, Mr, W. H. Soutar, and its General Counsel, Mr. Ivan Sabourin, *^, 0151 // { I. II. CRITICAL REVIEW Of LITERATURE * eoreful review of the published material on this subjeet Show* that th* majority of the reports art clinical and not epi demiological. They lack many elements necessary lor the applica tion pi epidemiological techniques-to their concent and most of the authors do not make claim to having done so. What has happened ( is that succeeding authors have drawn conciuatons and generalised beyond the scope of the works which they quote, Nowhere, lor ex *' ample, have e found references to a population ofasbestos workers, although several authors who have quoted the observed incidence of lung cancer in autopsies of persons who also hoc aspestosn imply that this incidsnce applies to asbestos workers. We have likewise been unable to find any study 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 Pall ft!), none of those reviewed gave any data on exposure and dust concentrations, and even Soil's paper merely mentions '`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 dusty." Thsrt is, furthermore, a complete lack of definition of l terms as used in the published literature. For example, the term 0137 / 1 i 'asbcstesii", as used, may refer to cimifci observas.* on.-,- by microscopic examination of the lung tissue, or tt may mA a radio- logicaliy detectable condition. Moat of the published reports obviously included women among their cases, but some of them do not give the number or pro portion of women involved in the study. There is also a lack of uniformity as to what type of ex posure most studies have dealt with- Of 99 cases enumerated by (122) , Hueper in 1955, only tea appear to have originated in the United States, and seven in Canada. Some of the earlier reporta apparently included asbestos miners, but it can be aseumed. since 62 of the 99 cases had originated in England, and since no asbestos muting opera tions sre 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 m the majority of these reports. With this understanding of the limitations of the existing literature with respect to epidemiological generalisation, it may be of value to consider in somewhat more detail some representative earlier publications, o few of which were referred to briefly in the previous section. 0138 7. On* of m* most aetailco studies and one which deierves <bi) the most serious consideration is that reported by Doll in 1955. ' Thu study review* uuiti of death among asbestos worker! bated on coroners' record*. It also attempts to estimate the risk by study ing record* of men who worked for at least 20 years in exposed situa tions. Doll concluded that lung cancer was a specific industrial hazard of certain asbestos workers and that, miter 20 years of exposure, the risk ie ten times as great as for the general population. This article ie important for several reasons, in addition to the definite conclusions at which it arrives, for example, it begins by stating that "in view of the infrequency of asbestosis, this large num ber of cases (bl cases 01 lung cancer) suggests--but does net prove -- that lung cancer is an occupational hazard of asbestos workers." Neither this article or any previous one which w* have examined presents any figures to prove that asbestosis is an infrequent occurrence. Es timate* Of the number of persons potentially exposed to asbestos dust in the United States alone very from 10,000 to 35,000 and the incidence of asbestosis of any degree might be higher than Poll imagines. . This study, like 10 many others, involves autopsy records. The number of persons involved in the statistical analysis is only 113 representing only 1,0*12.25 man years of life. It is also true that in selecting men whs had been employed for at least 20 years, the study auion.jticali v exeiwdvd those who died from ether causes after shorter employment. ' ns ( It 4*10 seem* uut Liu* rv;* doe* not ua any r,* cast* lo the literature, although Hueper in enumerating 99 <a** reported prior to 1955, lilt* 11 discussed In It. Clearly, alto, the paper it net dealing with atbetto* miner*. Another rtaton why thl* publication ia ol importance ia *taitmeat which it contain* to the elitet that "the atrongeit evidence that it (lung cancer} may be a hazard (in atbetto* worker*) ha* been produced by Merewether and by Gloyae." An examination el these relerence* leave* at icatt *ome question a* to the strength ol the evi dence produced. - (92) In 1951 Gloyae pretented a review ol 1205 autopsies on perton* woo had worked in variou* dusty occupation*. Thi* num ber included 152 asbeito* worker*, ol whom 121 ahowed "pneumoconio*i" --presumably aibeitoni. Fraary cancer ol the lung occurred. 1? time* in thi* group, an incidence rate ol 14.1% lor lur.g cancer among autootied aabettetit eatet. There were in hi* tenet 795 caac* with tilicoti*. and d.97. oi the** ai*o ahowed primary cane tr ol the lung. The incidence ol lung cancer in other Iona* ol pneumocomoti* wa* 6,7''., *nd in to'* cate* which proved not to have any type of pneumocomoti* it wat I. Jr. Gloynt considered "the mortality ol the atbetto* worker*" to be "disturbing". First ol all, it it obvious that the paper doe* not deal with the "mortality ol atbetto* worker*", and secondly, ii must bv borne mine that all oi Dr, Gloyne'* cate* were submitted to him 0140 9. f :.,f ,tudy because the findings were unusual (or uncomplicated pneumo- 9 . aniwiis. Presumably. ail cases, including cbot oC asbestos-.*, in *hu.h the finding* were not considered unusual were never brought to Ur. Gloyne's attention. A* * matter of (net, in the unit paragraph in which be expresses concern over the incidence rote in asbestosis, lir. Gloyne himself point* out that tb* rate (or lung cancer based on t.**eropsies *t the London Cbc*t Hospital was 21,3% while the figure* withe Itegistrar-Gcneral showed only 2.4%, He thus recognized tbzt autopsies on a certain selected group o( coses were not representative .(tb* general population. It would seem, then, th*t notwithstanding i im- value of Or. Cloyne's work, its importance a* an index of the pre ii valence of lung cancer in asbesteties has been misinterpreted by those ! *bo have quoted bun. All that it really show* is the fact that in a group i t .. .i. cases, selected for special study primarily because they seemed it.-.trmal by preliminary examination, 1?, or 14.1% had lung cancer. blerewether in loq?t in the report of the Chief In - spcctor of Factories, reviewed all cases reported between 1924 and i^db m which atbvstosi* was tbe cause of death or a coexisting con dition, This work was later extended to include all such cases reported -p to December, 1934, by which time there were 344 death* including 2-,3 males aoc l 3** female*. Among them were SS cases (16%) of cancer Ot thi lur.g, 41 ui males and 14 in females. It is quite possible that a Urge number of asbestotics who did not di of their asbestosis, or in 0141 10. whet* death certificate it *ai net mentioned, may have been matted. The import o:' that 167V it enhanced by the timultaneout statement that the incidence o lung cancer m autopsies of the general popu- Ution it only 171. The danger of attempting to compare a rat* found in 344 catet with the rat* for the general population without retpect to age, occupation, and many other variable*, tuch at taoking habiti, it obviout, Lyneh,^*^ who with Smith had reported the firtt cat* in 1935, reported four cate* of carcinoma of the lung in a teriet of 49 autopilot on workert in an aibettot manufacturing plant who were thown to have "demonttrabl* dcpeiitt of atbettot in the lung*." Thit, of court*, it net necettarily identical with the ditcate atbet- totit. Lynch, hirr.teif, pointi out that, although thit it an incidence of 1.21V, "both figure* art toe tmall for very eertout atatittical type* of calculation. * Neverthclett, later writer* have used thit paper to ttrengthen the cat* for an attociatton of carcinoma of the lung with atbettotit. It it of interest to note that Klotx found only four in stance* of lur.g cancer in 471 catet of atbettotit, a teriet 11 time* at iarge, Behrens, a* quoted m Merewcthcr estimated that, of 10' cases of atbettotit in the literature, 44 showed associated cancer of the lung--giving an mcioence of 14.27V, Thit it another eat* of generalising an incidence obtained in a group of cases which were 0142 { u. undoubtedly reported only because tom* of them showed lung cancer, to posrtbly hundred 0/ asbestotic* whole euei were neve: reported. Th iut)< applies to the conclusion of Teleky who appears to have reviewed reports of J9 autopsiee on person* with asbcstosit among which six coses of lung center occurred. Information from those sources does not justify generalisations with regard to mortality rates. Werhet who made the unequivocal statement that lung ( cancer would result in from 7% to 17% of case* Of asbestotis, allowed himself considerable latitude by qualifying it, as regards time, to an interval of 1 1/2 to 20 years. Finally, mention should be made of some entirely unsupported statements which tend to build up e mistaken view - point through mere repetition. One example is a sentence in "Noniuber- (76) culous Diseases of the Chest" where the authors say simply, "an ex cessive incidence of pulmonary cancer hat occurred among workers in other occupations, such a* asbestos industries, nickel-copper refineries, stokers in generator plants, etc." without substantiating reference. As an illustration of the ease with which a few reports which merely suggest a certain conclusion can, through the lack of a sufficiently critical attitude, be summarised to produce the conclusion in a definite 169) , form, an editorial m the Journal of the American Medical Association mentions the work of Wedler and the report of Merewcther and then es tablishes the causal relation between asbestoeis and cancer of tht lung as { settled. As a final convincing argument, it refers to "recent experimental 0143 ST"! / i 1Z. observations (by) Noremann ar.d Sorge t^U.. ^ Tjjis lt t^c exptr.rr.e-: in which iquimcui carcinoma wti said to have been produce in about * dosen whit* mice, end which be* sot beta duplicated by any other m- vtstigatori Perhepi no oat he* written *o extensively or so dogmati cally on the subject at he* Kueper la 1955 he reviewed the case* reported prior to that date end enumerated a total of 99. Eleven of these were those discussed by Doll (63) sad appear to have been case* covered by other authors. Sight were discovered by Karma* ay sad Kenaaway in an analysis of death certificates and, unless Mtrewether's study was incomplete, these eaees should have been in cluded ui his report. Of the remaining BO, it is quite possible that the 31 contributed by Merewetber and the 17 by Cloyae contain some dupli cation with each other or with other English authors. In the same paper, Hueper dismisses the ides of determining the frequency of pulmonary cancer among the total worker population of the aebestos industry on the grounds that it is immaterial how many workers in the industry develop lung cancer, since some of them have no exposure and therefore do not develop asbestostei 0145 n. IU. PRINCIPLES OF THE EPIDEMIOLOGICAL METHOD -- As 04.* been indicated, much el what it new troughs to bt fftuiial concerning the c*mp*niivt frequency el lung cancer in dL'ftrent population group* ha* been developed from the analysis of clinical material, particularly turgical and autopay record*. Thi* ha* been lupplemented to aome extent by the reported impr*a*ion* el various clinician* bated upon their pcrtenal observation*. More receatty, however, attention ba* turned to the systematic investigation at this problem, by the same methods that have proved so successful previously m the study of communicable diseases, that is to say, by tpideoiologieai methods. Epidemiology is the method of investigating a specific disease in human populations in relation to certain variable charactersues, including the environment. In contrast to the clinical method which is primarily concerned with the characteristics of the disease is individuals, epidemiological research involves the investigation of the disease as a mass pbsnomenon. It seeks to discover what propor tion of persons in a given set of circumstance* will eventually develop the disease. Epidemiology cannot predict whether a given individual will fall victim to specific disease, but it can predict the approxi mate number of case* of this disease which will develop in a population specified sue, composition, and subject to given environment. It 0145 14. proceed* by first carefully and accurately describing characteristies Of the disease m dll:'*rent population group* and its essential objective :* the formulation, testing, and verification el gencraliaationt concerning the disease in question. In order to apply this method of investigation to the pro blem under discussion, the Foundation was of the opinion that a study should be planned ao as to provide: 1, A well defined population group, 2. Available data for all members of this pop ulation, including the healthy as welLas .the ill. t 1. 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 hsve been reported, is that little or no information concerning the healthy people in the group seems to have been available to the author. Therefore, results of these studies cannot properly be generalized to include such people. In order to drew a generalization regarding ail asbestos workers,;! ti necessary for a study to include living person* as well a* the dead. Limiting the investigation to autonsird cases, as has been frequently cone in earlier studies. Still further restricts its use 0146 is. in gen*rainatisn. The problem with which the C-coc: Asbestos Mining"Assoei*t;on is concerned i* whether asbestos miners ex perience more lung cancer than docs the general population. The answer necessitate* the collection o( reliable information on asbestos miner* as a group, as well as on the general population. It seems advisable to discuss the difference* between the epidemiological approach and that uied in the ctudict which have been reported to date. A very important consideration is the lact that lung cancer, in spue of its increasing numbers, is still a disease of low incidence; lb*t is, in a given population not many persons will contract this particular disease. This fact requires that large samplet or group* must oe stueicd to provioe meaningful results. Recognising 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. t 1. Comparing the relative freauenev of cancer in various sites. 2. Comparing the relative frequency of cancer in a group of hospitalised patients. J. Comparing the relative frequency of cancer in a group of cases coming to autopsy. The frequency of cancer of the lung relative to the total of sit types oi cancer may be increased merely by reason of a decrease 0147 1 K.'t.U**1 lb. m the incidence of cancer o{ other tit**. This could be true even though the mcicente of lung cancer remaineu constant, or u' tt decreated leee rapidly than that of the other type*. Attempting to compare two population group*, looking only at the. relative frequency of cancer in various body litet, may result uffinding a higher percentage (relative frequency) in one of the groups, when, in fact, the mortality rate of cancer of a particular organ is ex actly the same in both group*. This is because the relative frequency of cancer in other organs may be lower in the second group. The mor tality rate from a particular cause is the true measure of comparison. . It is apparent that selected group* such as hospitalized patient* or autopsy cases may not be representative m any way of larger group, and that in dealing with such samples, the observer may easily find more cases of any kind than would be found in a group of the same size, but representative of the general population. It is true that investigation of cases from such a sample can furnish information valu able for research, but the use of this information in drawing generaliza tions it necessarily restricted. It is tbt obligation of both the inveetigator and of those who read bis report to make proper comparisons and to draw only lho>* conclusions which are valid and justified., A good statistical stucy o case* of cancer of the lung occurring tn a group of autopsies can lead to 4 proper inference concerning the frequency of lung cancer among cases coming to autopsy, but only to such cases. Tor -w 17. informztton from luch * ttudy to oc projected to tom* larger group, it ;* neeetizry tbit the tutoptie* repretent * good izrr.ple of thzt Urger group. To uiunt thzt tueh i* the cue in zny pzrueulzr tenet it dingerou* znd likely to be f*i*e. There 11 him danger thz: the figure* reported by tome zulhor* miy be miieonttrued z* Applying to ztbotot worker* or even itbettot miner*. when, in fzet, lb zuthori in qutttion do not moke itu* gene r Alii At ion, nor tin the gentraiizition be tnAde for the reatont tiled. Clo* ttudy of (be report! rtveii* thit the percer.tAget quoted relit* Only to the group of Autoptiei covered by the-pzrticulzr inve* liga tion. Tbe pretent ttudy, in cootntt to the earlier work*, hit been pUnned to utilize the epidcmielogicAl method. A well-defined group of Atbeatoi miner* hi* been ettzbiithed m *uch z wzy thzt it con.ititu.tet z good zmplc of the whole popuiztioft of zzbezto* miner* m Quebec. Dztz for <J1 member* of thi* group hzve been collected And AnAlyied. Thoee concerning lung eznerr hive received most cArtful con*iderztion. Dtzil* of the method* employed will be let forth in z Izter ection, but the type of Approzeh 11 contidered to permit of izir companion! And vztid generalization*. 0149 IS. IV. COLLECTION and ANALYSIS cr DATA A preliminary survey of potential sources of information ,u February of l?5b involved discussions with the physicians in charge ui the sibestos companies' programs had with clinicians, pathologists, representatives of City ead Provincial health departments and of the Canadian Cancer Society, had other interested persons. It was tuund that morbidity data, although somewhat limited, were available iron such sources as the hospitals in Montreal and Quebec City, and the 13 Cancer Detection Centers in the Province, However, because m ihe high mortality in lung cancer, it seemed advisable to depend upon Lu relating to deaths. These we found to be obtainable at the vital statistics department of the Ministry of Health in Quebec City, Prom the preliminary survey, it was apparent that extensive and detailed in formation could be gathered with respect to both the persons employed i the asbestos mining industry and mortality figures for the general population. '' Following this exploratory survey, the initial effort was iirected to the collection of data relating to all workers wbo had been ;.'ntn tnrougr. the clinic at Thetford Stines since its inception in 1'H?, Similar information was obtained regarding all workers at the Canadian Johni-Manvilie Company tn Asbestos. 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. 015 / 19. aad th count of the individual'* health statu* or the cause of hi* death. ' Altheyh the ii:i to th*e two instance* were not e.tictly imiUr m * form, the inelution of record* from the personnel deportment it A* - betto* covering employee* who hid retired, died or become disabled provided diti sufficiently alike for the purpose of the *tudy, From thi* informition it we* po**ible to formulate for both Aebeeto* end The ifor d Mine* "cohort*" which could be well defined, ( should be representitive of coch group, end could be followed for i de finite period of time. A11 of the iveilible experience indicite* thit the i* development of aebestosi* in lc*i than five yeir* of exposure must be tomewhit rere. Accordingly, the cohort* were defined i* including every worker who hid i totil exposure of five or more yeir*, ind who wi* on the employment roll* it Asbestos or Thctferd Mine* in 1950. These cohorts were then followed by mein* of the annual physicil ex - imi&iuon record* through i *ix-yir intervil, 1950 through 1955. All diti regirding tbe*e group* were then tibulited m order to determine :>- the chericteristic* of the cohort*. For the** who urviv*d the entire r*b period, reference was mode to the physical eximinition result* ind x* r*y finding* it the end of the period. Those who hid died were tibulited sepiritely ind the ciutc of dcoth corroborited by examination of the dcith certtficitei, A further search we* made concerning those m the ongutil cohorte who rcmiined unite unted for when the living ind the known dead had been tabulated. They reprotent men who hid left 0151 id. TABLE ? Number of person* and Number el Lung Cancer Death* by Length of Employment Length Aibestot Thetfer d Mines Combined of Lur.g Lung Cine*: Lur.g Cancer Employ- Cancer Beat bs Death* mtn: Ptr*en* Death* Per*cr.s P rovttt Total Per ton* Proves Total $.<? i0*19 20-2* *0-39 40-45 Total 8S0 864 342 168 IT 2 m 0 <915 0 1534 1 SBC 2 435 0 168 0 51 T Tool 0 1 2 3 0 0 e 0 1795 0 0 1 2398 1 1 2 922 3 3 5 603 5 7 1 185 0 1 0 55: 0 Q 9 5937 7 71 Vf O 4 Annual Lur.g Career Death Bate* per 10C, HOC Man-Year* oi Exposure by Length of Employment Length of Emslovmer.t 5-9 10-19 20-24 30-39 40-49 50* Over-all Atbesto* Total 0 0 49 198 0 _0 22 Thetford Mines Proves Total 00 11 11 57 57 115 192 0 99 _0 0 27 41 Combined Proven Tot*. 00 77 54 54 138 193 0 90 00 25 34 0170 39. 'AB LS 6 Number 0/ Person* end Number of Lung Center Deaths by Exposure Category Exposur* Cat*< *orv Asbestos The: ford Mines Combined Lung Cancer Lung Cancer Cancer Deaths Death* Per sons Death.* Persons Proved Total Person* Proves Total I 969 2 1062 2 2 2031 4 4 11 564 1 1586 2 3 2150 3 4 UJ 735 0 1017 2 4 P72 2 4 Vnknowa 5 0 00 0 50 0 Total 2173 3 3665 6 9 5956 9 12 Annual Lung Cancer Death Rates per 100,000 Man-Years of Exp osur* by Exposure Category xpo*ure Caiecor-. Asbestos Total 1 U ill Uolmown Over-all 34 30 0 0 22 No one exposed T'netford Mines Proved Total 31 31 21 32 32 64 *0 27 41 Comb: r,ed Proves tau. 33 33 23 31 19 37 00 25 34 0171 40. exposure to ustiici it vr. ar.y ay connected to lung cancer, we would expect that the longer And heavier the exposure. the higher the rite that would bt found. The only possible error in this interpreta tion could occur if the weighted exposures were inversely related to year* of employment, in which cat* the heaviest weighted exposure (category Ull would thew the shortest length of employment. Tablet 1, 10, and 11 which list the number of persons is various exposure tstegoriet by length of employment indicate that this error has not occurred. In fact, the average number of years Of employment for etch exposure category is almost identical. TABLZ 9 Number of Persons m Various Weighted Exposure Categories by Length of Zmployment Asbctto* Length of EiiiOiOvmer.t 5-9 !0-! 20-29 30-3* iO.-t; 50 * Tout Av. Yrs, of Lspcturt Weichted J_ 425 27J 159 9 9 2 559 15.5 Caietrnes ii III linhnowr. Total 213 217 89 42 3 ___ 0 So4 15.2 239 JT3 92 27 4 0 735 14. 5 0 1 2 1 1 0' 5 29.0 ago 164 342 165 IT 2 22 7 3 15.1 T 0172 4;. TA3LC io Number of Persons ir. Various Weighted Exposure Categories by Length of Employment Thetford Mines 'Length of Employment 5-9 10-19 20-29 3009 40-99 50 Totel Av. Yrs, of Exposure Weighte d Exsosure Cettgories J_ JL ' iii 2*9 390 155 149 67 22 1062 19.9 385 666 2*4 176 64 21 1556 18,7 251 478 151 110 37 10 1037 18.1 UnJtnour 0 0 0 0 0 0 - `0 Total 915 1539 580 435 168 53 3655 18.9 TABLE U Number of Period in Vsnou* Weighted Exposure Categories by Length of Employment Combined Asbestos end Thetford Mines Length of Emolovment 5-9 10-19 20-29 30-3 40-49 50 Total A*. Yrs. of Exposure We;*hted x94IU?C CetetOTies 1 u HI T' 707 663 3M 247 76 24 2031 17.8 598 883 363 213 67 2! 2150 17.8 490 851 243 137 41 10 1772 16.6 Unknown 0 1 2 ( 1 0 s 29.0 Totsl 1795 '2398 922 60 3 185 55 5958 17.5 C17 V Table 12, which develop* the rate* for smoker* and r.on- smoker*, vs most striking. It shows that no: single esse of lung cancer developed among; the 12bS nonsmokcr* end that all ease* of lung cancer, both "proved" and "suspected", occurred vn smoker*. A comparison of Tables S and 12 certainly suggest* that smoking i a greater hasard than exposure to asbestos in the mining operations. Table 12 was so striking that it was felt that further veri fication was accessary. It was possible that some abnormal distri bution may have occurred, c.g., the nonsmokcr* may have included a larger percentage of young men. Consequently, additional Tables, 13, H, and 15 were constructed to show the distribution of smokers and nonsmokers by age, length of employment, and degree of exposure. Although thtTt are slight differences, they do not account for the fact that all Observed case* of lung cancer were in smoker*. In respect to age (Table 13) the combined average age of the smokers was 4.5 year* leas than that of tbc nonsmokcr*. Table 14 shows tbat as far as length of employment is concerned, the smokers had worked about 2.3 years less on the average than the nonsmokcrs. With longer exposure and greater age, one would expect the nonsmoking group to show a higher Tate if lung cancer were due to asbestos, - Table 15 show* that the average expoeurc category was al most the same for the two groups. Therefore, this variable stems to be nf no importance in accounting for the difference between lung cancer death rates for smokers and nontmokcri. 0174 43. TABLE 12 Number of Person* and Number of Lung Cancer Deaths by Smoking Habit* __A*betos__ Thetford Miner Combined Luaf - Lung Cancer Luaf Cancer Cancer Death* Death* Pereon* Deaths Person* Proved Total Person* Proved Total Smoker* Nonsmoker* Unlsowa Total 19)1 340 2 Utj 3 0 0 1 2742 925 ie 3625 6 0 0 6 9 4673 9 12 0 1265 0 0 0 . 20 0 0 5956 9 12 Annual Lung Cancer Death Kate* per 100,000 34an<Year* oi Exposure by Smoking Habit* Smoker* Noafmokers Unknown Over -all A*be*to* Total 26 0 0 7T Thetford Mine* Proved Total 36 55 00 00 n 41 Combined Provee Toll, 32 43 00 00 25 34 0175 ( \ 1 tL.u. 44, & S o U o * < > a * o --e c I 9 I z c2T,i' -IS- E il t* *4 O 5*> |a \< Z S < *4 ** -- <4 C -- -- j0 O' r* f- o ift ^'T --^ S--O --w |*4 *0. ?*** o e w i I -- ** o I** S tA n m 01i9s*- | c . i. M QU C <0 ^ i'*' C > * < :0 ! w "? '3T A < -r 1 *; po- * * -o a ^ a. 9 O >* <a 4o e o Z c o (A 9 o o t e v v i! = ii ss Z lA p> O <r * fi ae g*'. C ^m *6 -- i5 32 a- e -- < -- * <d -- *I * -- gi 0* O ^ *A ^-- 9" eeo e o A tfi 5 5S Z: OCA G "tf *0 *^ "*(o **4*9* 8 U c03. *<$ C >3 " O / A A -5 9 ^ * * 5 " !.* dun .usy* 0178 t * . . 45. t jo I At e 9 1[At 9 9 mm s, r C O s* -3 3C *4 1 * fa ft* A A/ C* tf* * *4 10 N * i- VA --. ,V - JC _9 e --. e Z *4 <A -- _ a. eV i u sr Ac u 9 jo r* A1 ft* ** o im m m. * r* 9 t a* ft* OO -- f* * . 9 w *4*4( e 9 A* 10 ys Arf g_ (A l*' ! i c V i tt e * At o 9 9 *0 j * e 9 rv -- SI 9 e; | 9* 9 --' AJ JL * Al * pj J * V e* > -1 s 9 o% *di u* ** Al ** * *4 A 0* A4 Jt e 2 9 c e Z V ^ C % * *n PJ r , 4 #o 9 4 10 O 9' 9? 1 zc IP 9 9 40 -0 V 0 9 *f 9- P* *4 A* Af 9 * A# * ii - - e e oi* *2 9 e h tt 4C , 9, <0, <0 4 9 0 W*1 |A w 6 * <A JC 0 . 9 e e o 9 e 0; 1 1 ` 1s 9* * w-i <0 *5 Ml * v it s* 0 r * 9 A* Z 9 9 at y *1 o I* 0 U9 r* m 9 ;* + * o 2 9 Z * % N< * . 5 v C e y* * *0 A* K A. 9 < 9 r r* A* * 9 *1 r PA A 1t1 o ** C %> 4A X > 3* - 3- " m 2= *s e y ft "" ** r CM V i_ * mi 2 * C m9 c 1 9 *4 e * 9 3 0 * 1* < 0 V i * "9 ~tf e jr a * c* a* k * "W PA 9o M 9 W P9A 9 4T 9 0 ! 0177 -46 : i; .**- m. -* c * JXJi i** <st *i* i*i v* .r - *> v -j -|<* r c 3)^ r --> 2 s *^^ > ^1/ f* K> If* s^ . * . 0 9 9* 23 9i I ** ^tf **V3 C If u 9 9 V nr %i *f * -a *r< * ^ r* o 90 K u ^ e ejt^ V 0| 9 if* t. x0 W* >. A p* otur- 0 n 5g 0 *J-<J 0I|^ 0> *rfv I* c 2 Z\m+ *4 V 0 Z 0 < s 0 i- 2 w * => 1 e o[n ^ C S'- or i^ * *- -Si JVC A 9 s e : |5 > S f> lA e * 9 w -4 *9 ~ e 5 * irf' * 9 Z z 9 J V rfv itt * ' Jt i . 9 ** f ^ *4 *si 1 2 * ^ - "* ** S* I-- . =* - tt . t1t O O 4|'*' I ^* ^-s*i *1; ; ^ -* !-- t i r *j I? K1 wu 2 '-- 2s 5 t C^9U < w >* 0r ~ J u s --2* i5 0178 ./ / ' 4^. Tie resuit of this additional anaJyis* 14 that none of these factor* appear to iciten the effect of Table 12. which ; therefore atrengly mggestivc of the importance of smoking a* compared to the other variable*. Abe*toi* and Lun; Cancer c When we attempt to relate the lung cancer death* occurring in the cohort with the reported catea of asbestosi*, we are immediately aware of a disturbing inconsistency. Various authors report the incidence of asbestosi* after 10 or IS years of exposure a* exceeding $0%, and m one study, at high at 8?>, However, data on cases of stbestesi* from the cohort* at Tbctford Mines and Asbestos pro duce a rate of only about 5%. It i* true that these data are baaed on only those estet which have bees proved at autopsy, and those whose most re cent x-ray interpretation resulted in a diagnosis of asbestosi*. This in cident* may be far lower than if based on microscopic examination of the lung tissue. As a matter of fact. Dr, Cartier ha* estimated that there are probably 300 worker* who do not *how radiological evidence of asbestosi*, but who have tome degree of fibrosis, He al*o estimates that there are perhaps 40 worker* who may have died or retired with this diseaac. ln*t*ad of 143 caacs of a*bc*to*i* tn the whole working force at Thetford Mine*, we should then have perhaps S00, but even thi* would remit in an over-all L rale of lei* than 10', which it far below tho*e widely reported, in our 0179 combined conort, there are 1765 men who have bed more then 22 years_pf employment, end 431 of theee have worked in the heaviest average exposure. According to the records, we can account for only 136 esses of asbestosis in the combined cohorts. U even 35% of the workers with more than 20 years'exposure develop asbestosis, we should expect about 425 cases. This leads us to believe that there is a very considerable under-reporting of asbestosis, Such a bypothe als is easily eonceivabls when one coatiders that many chest x-rays in this group may be considered normal by comparison with others t' in the same group whereas, if they were to be compared with wha: are considered as normal chest x-rays elsewhere, they may be inter preted ae showing fibrosis. Cases of asbestosis which were accumulated from the au topsy records and from the periodical physical examinations result m a distribution which is shown in Table 16. TABLE 16 Distribution of Recorded Asbestosis Case* In Cohort Living Deao Total Asbc stos 16 4 22 ThcUorci 66 30 116 Combined 104 _J4 135 49. TaB l7-J>t.-El N'JSitr of Aibeiu<:t Cate* By 1-er.gti of Employment and Eapoture Category Atbettot .Length of Employment tin than 10 10-19 20-29 SO-19 90-49 50 Total Av. Yr*. of Employment Expoture Catecerv _1_ ,U ui 0 0' 0 01 2 27 4 01 4 00 1 00 0 29 n 25 25 29 Cnior.owr. 0 0 0 0 0 _0_ 0 -' Total 0 3 11 5 1 0 22 27 Perccntaget of Atbestoai* Catet By 0(10 of Employment and Exposure Category Length of Employment Exposure Cat ecorv m Lott than 10 10-19 20-29 10-19 40-4 50 Over* *li 0 0 1.1 0 0 0 .1 . 0 .5 7.9 2.4 0 l*fe 0 .5 4.3 14. 8 25.0 1.5 * No one *x?oftC3 ^ xiui Untaown 0 0 0 0 * 0 Totai 0 .1 3.5 1.0 5.9 0 1.0 0181 50. TA3L :T - Far: U Nuir.ber oC Asbtetoai* Cue* By Lcogtb of ir.pioyTBent and Expoturt Category Thet'arb Mines Length of Err.olovrr.er.t Un than 10 10-19 20-29 30-39 40-45 .50 Total Av. Yrs. of Employment Exoosur* Category _ 111 0 0 '0 01 7 1 5 21 2 15 33 0 6 20 02 2 4 25 3 30 36 34 UnJctowr. Total 00 0a 0 26 0 50 0 26 04 "0 116 34 Percentage* of Atbtliei;s Caeci Bi Length of Employsesc anc Exposure Ca: "gory Length of Eroolovrr.cr.t Enosure Caterer V II 111 Unknown Total -if7: Lee* than 10 0 0 0 * o 10-19 0 .2 1.5 0 .5 20-29 1.3 1.8 13.9 0 4.8 30-3" 1.3 8.5 30.0 0 11.5 40-49 0 9.4 54.1 0 15.3 50 * 0 9.5 20.0 T.5 Over-all .4 1.8 8.0 0 3.1 * No one exposed 1a tbit group 0182 SI TABLE 17 . Pert .112 Number oi Asbestosis Cases By Length of Employment and Exposure Category Asbestos ud Tbetford Mint* Combined Length ot Emoloymer.t Lee* than 10 10-1? 20-2? 30-39 40-4? so Tout Av, Yrs. el Employment Cnoiurt Catesorv J1 . - iii 00 02 4 12 2 16 06 _0_ Z 6 >8 2$ 33 0 9 25 37 21 2 94 33 Unknown Total 0 0 0 0 0 0 0: 0 11 41 55 27 4 138 33 . Percentage* of A*be: otis Cases By Length of Employment ar.c Exposure Category Length oi Emolovmer.t Lf then 10 10-19 20-29 30-39 40-49 50 Over-ell n<uM Catetjorv i. JL 111 00 0 0 .2 1.0 1.3 3.3 10.3 .8 7.3 27.0 0 9.0 51.2 0 *.5 20.0 .3 l.S 5.3 * No one exposed in this group Unknown 0 *0 0 0 0 Total 0 .5 4.4 9. 1 14.6 7.5 2.0 0183 52. A percentage uscider.ec of asbestoses :'er t<ci exposure category m in: ceveicped a* well as lor tech pertoc of employ ment, This information is shewn ia Table 17. It will he noted that within an exposure category, the incidence rises with increased length el employment. It is else apparent that the incidences, even in the category of heaviest ex posure, ere fer below the retes found by the authors previously re ferred to. It seems clcer, the: unless concentrations of esbestos dust to which the miners ere exposed ere very much lower then those which eotem in ell tbe other stuctes, there bes been e'gross under reporting of the tsbestosis esses. The obvious result is e higher rcletive frequency of lung ceaccr in association. with sabestosis. Tebte 19 comperes deeths due to lung center end fatal esses with sbettotis, elone end m combination with eech other. TABIX It . Pert 1 Statistical Anelysis of the Ceuses of Death Asbestos Cause Asbestos is No Asbestosts Total Percenter e Lung Center No Lung Cenctr 1 ( .2) 2< 2.E1 J 6.1 19 aj. e Total 7 45 49 Percentage 9.2 91.9 Figures in parenthesis ere the "expected" numbers 0184 Z' c taer-' \v =\ im- . , if Si. tab - i# - p*.~. y Statistical Analysis of tit Causes ei 2*:t Thttford Mine* Cause Asbestos is No Asbestos;* Total Percentage Lung Cancer No Lung Cancer Total Ptretauft ' il t.3) .25 (26. 7) ib 21.2 3( 4.7) 101 <99.3) '104 . 6 126 132 4.$ 95.5 figures in parenthesis art tbs "`expected'* number# TABLE 18 . Part SI < Stat.ir deal Analysis of the Causes oi Death Asbestos and Toetford Mint* Combined Cause Asbestosis No Asbestos*.* Toil; Percents'* Lung Cancer No Lung Cancer Total Percentage <{ 1.6) ^8(30.4) 32 17.7 5 { 7.4) 144(141.6) 149 82.3 9 172 181 5.0 95,0 figures in partnchciia art tbt "expected"' number* - Six death# from unknown causes not included The number of lung cancer death* combined with asbestos!* it larger than would be expected in each cohort and in the combined cohort*. Thi* difference ie significant at the 55% level uaing the chi* square test of significance. The importance of the under-reporting of asbestos;* can be observed in Table 19. 0165 54. TAB LX P Statistical Analysis of the Ctutt ot Death if 20 Konasbestosis Cases bad beta Diagnosed as Asbestosis Cases Cause Asbestosis No Asbestosis Total Ftrcewtaee Lung Caneer No Long Cancer Total Percentage 4( 2.6) 44(49.4) 52 24.7 St 6.4) 1241122.6) 129 71.5 9 172 141 5.0 95.0 Figures in paresthesia are the "expected" number* Is this table, it has bees assumed that 20 ot the cases which did sot have lung cancer had which were reported to have so asbestosis did, intact, have asbestosis, the diagaosts ot which was missed. Although the eases ot lusg cancer with asbestosis are still ' higher than would be expected, the ditteresce ts ao longer sigsiticast at the 95% level. This still it true it fewer than 20 cases were ehitted hut it ts reasoaablc to expect that at least 20 ot the 144 might have shown asbestosis had they beea subject to autopey. Oa the other bead, a shift of about 40 cases would produce an expected rate almost equal to the rate found. Explanation of this effect of under-reporting of as* bestosis has been stressed because it seems so obvious that la under, reporting asbestosis the relationship between it and lung cancer has been made to appear more significant than it probably is. Oi!P* c irjr- / **$ ; , . .. Four of the proved ca*e of lung cancer and cot of :h* *u*pceted were a**ociatee with a*be*to*i*. Since we hove er_y 12 death* in which a*be*to*i* was present according to the rcecrc*, the incidence ia this aerie* i* 12.5%, woile tti* i* (lightly lower than the rate* found by Mcrewetber, Gloyne, and Wcdler. it it (till much higher than could be expected if the a*besto*i incidence were anywhere near the experience reported by other autbora. e Comsarieon of the Cohort xeerienc with that Of tbe 1 Province of Quebec. Dominion oi Canaoa. ar.c the United Stater la order to mahe a companion of the experience among aabeitoi miner* with that of the gcacral population of the Province of Quebec, autiatici were gathered, a* etated earlier, ia the office of tbe Division of Demography ia tbe Proviacial Miantry of Health. Tbe data oa total dcatha, death* from all form* of caacer, and death* from caacer of the luag were obtained by **x and by eouaty for the year* 1150 through 1955, In addition, all death certificate* which *pectfied primary cancer of the lung, and all tbote.which indicated lung cancer but did not apecu'y the origin, were examined for the year* 1952 through 1955. Tablt 20 give* a tabulation of tbe number of deatt* from lung cancer in the Province ano in the two cohort* for-the year* 1950 through 1955, and *bow* the annual rate per 100,000 in thce (Cgmrr.t*. 0187 U ill be notec from the table tbit the mortality rat* for the Asbestos cohort it almost exactly the taste at that lor the Province, while tie rate !ot "proved" caret in the Thctiord Mint> cohort it only slightly higher. When the "suspected" caret are included in the calculation, the rater let the Thetfcrd Miner cohort rirer to 41.4 per 100, 000 which ir nearly twice at high at the rate lor the Province. Thir. it will be recalled from the previous discussion el the "suspected" cater, ap proach** but doer not exceed the sigaidicani level. One further interesting observation Iroax Vable 10 ir the rather marked increase in the total number of carer lor the Province between 1-50 and 1955. It is assumed that at least part o this increase ir due to improved recognition and reporting of lung cancer during the interval. For this reason, the yean 1954 and 1955 were thought to be more nearly representative el actual conditions. Even so, it ir quite tfiri likely that the general population is not studied lor lung cancer with the same diligence with which this disease is looked lor is the miners, and it seems probabis that the mortality rate's lor the Province would tend to be low. This would appear to be substantiated by the fact that the reporting of cases in the combined cohort showed no such inert ait ever the same period. Table 21 was compiled to show the annual age-specific ;ung cancer rate of cases in which the death certificate merely read "cancer of the lung", as distinguished from, thosu in which the diagnosis was 01SS \ A C sz. tn the I'ru v in c c fig u r e * . It h e * been a**um e<t *11 m ale lung c a n c e r d e a th * a re fo r m en o f 20 1 y e a r*. 56. confirmee iy autopsy, surgery, or biopsy. The tern: 'spcstftee primary-' refers to those cates is these sane two categories m which the tumor was specified as having originated tr the lung. It *Ui he noted that, of the total cases certified is 1955, a much higher percentage than is 1984 was specified as primary. The tabic also shows that a higher percentage of the total cases certified in 195$ were proved, agais isdicatisg increasing interest in this dissass, A comparison has bten made between the agc-epeeiiic rates shown m Table 21, and those for the cohort shown is Table i. An average of the 1954 and 1955 rates for the Province hat been, used, since the 1955 figure was higher and may have been exceptional. This comparison, summarised in Table ii, shows that the observed number of deaths in our sample is not significantly greater than the expeetea number of deaths, based on the average of the 1954 and 1955 figures for the Proviacs. It is true that, in the case of the age group of e$ and over, the five deaths provide a figure which ia al most significant at the 95?* level. However, it should be noted that this number includes one oi the suspected but unproved cases previously referred to, furthermore, it is rather likely that the rate for the gen eral population is understated in this age group, for the obvious reason that the exact cause of death in the very old ia not a matter of the same intensity of interest as it ia in younger persons. 0190 / \ X4* 59. Before leaving this comparison of the Province with :he muitrt, it should be shown that their age distributions art reasonably the umt. That this is the cast can b* observed from the following tabulation; Age Distribution of Adult Males for the Province of Quebec, 1951 (Rapport, 195+1 Age Crouo Number 20*4+ 45*54 55*64 65 Total 727,135 Itt,952 128.94+ 113,46* -- 1, 158,496 Percentage 63 16 11 10 100 Percentage Combined Cohorts t 66 19 10 5 100 It should be remembered that the miners retire and con* sequently, it can be expected that the oldest age group will be larger is the general population. The data presented in Table 23 indicates that the lung cancer rate generally decreases after age 70, and we could expect the rate for all people over 65 would be smaller than the rate for a group of 65 to 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 which are somewhat lower than if we had been able to exclude the general population over 7$. 0191 C 5^. r~ \ 2 5 toa s6 -- v < " ii *> - *5 ** u * *5 s S3 ? 2; aV* -oW* . 2 *2 i U *e* 3 V2 iZ wt '-n .2 *m iz ** v U *t9o f*.t 5s w5 Hfi ~* to9 3C * *1 i. 0to a to --*- <^ * *Nf^ 9* W* ft f ft tfH *i ft ft Ift -- ^ *4 9-le ft ft ft|em m ;* si* -- V ^ tf|r- ft Xft ^ ft'jIAJ * s -- >|J^ - -I* 9 1 91 C *4 f*t* ft ft -* -- f94t ^*i4*^1 *. * ft ft* <d ft _ *9 to A *0* E to *e &6bs * ft to * to to tSoft 0 teo SV tttfooot --to _ to 9- . *" > C ~"" > ^ "ft i 1 *f0t 4 *v Az * c V S5 S* *^42 f-t* *5 t/ oa~ ft to to o ^e s 41 ^ 2< 31 *a U ft ! 1 ,9b 4to(. C* 'N it. * <4 Xl*J* -- f' -j' * i* * * to 4? 0I oOe* H to U _ ft ft ft ^ {*40 f9t* y* ffttlf to V ft rV * V 5 e X S *--tb9o C>to G Aft AW to W vto cT 01 H U *r mz a* 9 -J ft jo m ftl * ^* k-- "3 9ce < to ft C 3? H U N N 0 f* ' l*^it< v X* N ^ tft C V 0192 c:. . TABLE ;; Comparison of the Actual and Liptcttd Number of Lung Cancer Death* by Age Among Asbestos Miner* Age Groun Province Total Specified Primary Pate oer 100.000 No. of Mine r * Expected* No, of Deaths Observed No. of Death* Proved Total 20-44 45-54 5S*64 65 4 Unknown 1.8 24.5 67.6 <5.2 35D1 0* 1 1 1124 2 13 615 2 33 315 2 45 3 00 Actually . 4 c + Tbe expected number is based cr. the ave:rage of tbe 1554 and 1555 age-spceific rate* far tb* Province of Cue bee. Table 22 also answer* a question previously raised. It shew* that tb* members of these cohorts have ot died from lung can. car at as age earlier than tb* general population, and that such an ex. planatioe cannot be offered for tbe absence of lung cancer is 240 men with more than 40 years of employment referred to on page 17. A comparison between tbe asbcites miner* and tbe popu lation of the Dominion a* a whet* was made, using statistical material from srveral sources. In on* source, Phillip* gave age. and sex. Specific rates for Canada for three period* between 1531 and 1552. Tbe rates for males are given m Table 2}. 0193 tabu: :j Annual Death Rate* per 100,000 ter Cancer et tic Lu( in Cutu* Age Grttsi Under 30 10-34 35-39 40-44 45-49 50-54 55-S9 60-54 65-69 70-?4 75-79 10-64 85 All Age* ' 1931-1933 0.2 0,9 2.0 i.o 5.2 6.2 12.7 12.5 15. 1 10.7 15.8 6.2 11.4 2.8 Crouo* of Year* 1941-1'lJ ' 0.5 0.9 3.2 5.4 12.5 18.9 27.0 33.7 34.5 30.6 30.0 27.9 14.3 7.1 1950-1=52 ` 1.0 0.8 3.0 6.5 16.7 17.2 59.7 _< ' 77.8 102.9 86.3 83.9 59.7 71.0 15.8 "Mortality from Luj Cancer in Canada", 1931 to 1952, These figure* show strikingly lit* increase in rate* be tween J93l and 1952, and this inert*** ia particularly marked alter age SO, confirming an obeervation previously made, to the eilect that lung cancer hat probably been under-diagnosed in the older age group* in the general population. To use tfcesc figure* for purpoit* of companion, 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 population* m each age group for the years indicated is not known. 0194 this mult be as approximation. However, tbt rittt would be jorr.ewhat el follows: Ace Crous 20-44 45-54 55-54 65 o Bate 5 rr 69 90-95 Tbeie ratea axe, is general, lower then thoie developed for the totel (proved sad impeded) eates of lung cancer among the aibeito* miser*. The only large difference, however, i* is the 4f< group of 6$ yeir* tad ever, end it i* quite poitible thst the rete for thii group may have iacreaied for Canada between 1952 asd 1954 at it did for the Provisec of Quebec. (See Table 21) A further eompariton bat been made with an over-ail rate obtained from the Americas Cancer Society for roipiratery can cer death* is Canada is 1952. Thii rate, for male*, it 20. t per . 100,000, an inert ate of 5 per 100,000 over Phillip*' ln50-195I rate, asd compare* with 25. 5 per 100, 000 for proved eaaei asd 14. 0 per 100,000 for total cate* among the aabeato* miner* in thi* ttudy. It t* therefore obviou* that there are no important difference* between the rate* for atbette* miner* and thoie for tbt general population of Quebec asd the Dominion of Canada, 0195 54. Since i; :> prooabie that figure* for the L'rutec ire mor* complete and, therefor*, possibly more comparable to the data for the miner*. age-epeeifie rate* were computed from "Viui S:i:n- tic* of the United Sut**", Volume* I and II. for 1951. The** rates have been tabulated m Table 24. TABLi 24 Number of Death* and Death Bate* per 100,000 by Age Croups for the Adult Male Population of the United States--Data From .. "Vital Statistic* of the United State*", Volumes I dad II, 1952 Ace Crouo 20-44 45-54 SS-64 6b + Total -Pooulatior. 24,544,000 1,065,000 6,340,000 5,670, 000 44,619, 000 Cases 83 2979 6254 64 S3 16.599 Rate oer 100, 0C0 3.6 36.9 98.6 114. 3 37.2 It i apparent that these rate* compare favorably with those for the a*bc*to* miner * a* abewa in Table 6. Still other rate* for the United Statee were obtained from the American Cancer Society, and for male*, thete were 15.1 per 100, 000 tn 1951, and 2S. 0 per ICO, 000 in 1955. They are not identical with the rate calculated from the figure* oi the office of Vital Statistics, but this it possibly because the American Cancer Society rates are tor males oi all age*. Nevertheless, they, too, compare favorably with the rate* of 25 (or 34 for total cases) obtaining among the asbestos miner* 0196 V \* 65. Returning :o a comparison between the asbestos miners * *d persons who ire exposed to asbestos in on* term or Another [as distinguished frent the general population {roup* ;ust discussed, who have no exposure) an interesting observation eon be developed by ce* suction. Hueper has stated that th.tr* nr* about 15,000 persons exposed in tbe United States, sad w hay* found that th* Canadian nines employ about 6, 0C0. Elsewhere, it has been estimated that th* workers is England wbo bav* exposure total between 1,000 and $,CGC. With workers is Africa, Denmark, Norway, and other countries, st V least 50,000 persons must be exposed throughout the world, asd it can be assumed that this number bas been fairly constant in tbe 10 years stscc 1915 when tbe first case of asbestosit with lung cancer was re ported. At least million man-years of exposure has thus been accumu lated, and this figure can be divided by the approximately 150 cases of lung cancer with asbestosis reported during the 10-year period. Tnis gives a rat* of 15 per 100, 000 which is at least indicative that any lung cancer rat* which caa be calculated for workers exposed to asbestos dust is sot much greater than that for the unexposed persons. 0197 bo. Corrcar-.;r. Sura.-or, .jht Cjur.iies ,Ap titr'. *.? :~.c Ate<>:ot-?rai;u:..'; Aruus if.* t.:v. MK't'.cc u.o-n:it To compare lung cinctr mortality rate* m the coun ties surrounding th* asbestos-producing areas with another group Of count;*! in which no asbestos minor* art likely to re*ide, the rates *r* computed on the btni of figure* for the years 19S0 through i555. To* eight countie* *elct*d for companion were Argtniewil, Chateaugay, Montmagny, Pormeul, Richlieu, Rivieredu-Loup, St. Hyacinth*, and Terrebonne, mainly because they re present a wide geographic distribution throughout the Province. The counties selected because of their proximity to the asbestos mine* include Artsabatka, Seauce. Drummond, Frontenac, Megaatic, Richmond, Sherbrooke, ana Wolfe. Table 2S shews th* number of lung cancer deaths for the years 1950 through 1955 foT each of these counties, and a mortality rate, based on the adult mole population in 1952. To empnatn* th* comparison Megaatic County has been shown separately, as sat the Province of Quebec and alto the Pro vince with the tight soestos-preeueing" counties subtracted. Be cause o: its unique ;u.v; cancer Ocath rate, Montreal tt Isle dr Jesus has also oeen iiiteo m oreer to provide further comparison. 0198 r~ \ r m **tr n w o fi ? i ^ * *fftt * > ** * Vfti * 5. ft wnaft.. 2&n ft ; 9 JcfDt o C 9 o cCa ' f<tt 0 1 r> z sscr n r I nft an ft fOt *H 5> 9ft r n 9ft ft Xft o eo Sft 9t f*ftt< ( 49 Q4$S 68. It it apparent It ore the tabic that the lung cancer ceaii rate lor the eight counties immediately surrounding the asbestos* producing areas is practically identical with that o eight counties selected lor comparison. While hlegastic County ha* a rate nearly twice that el the combined eight selected counties, it is lower than the rate lor the Province, and considerably lower than the tat* lor Montreal. The figure lor Montreal would certainly he higher except lor the very lew numbers el death* reported lor 19S0 and 1981, and it would appear that some error in reporting ha* undoubtedly been toads. On the basis ol the other years, 1980 and 19S1 death* would be expected to be about 200 greater, and this would result in a rat* ol *0 per 100,000. The only possible conclusion Item this comparison is that there is no evidence that the persons who live in the counties surrounding and adjacent to the a*bcsto*producing area* have any greater incidence ol lung cancer than those who live elsewhere in the Province, Discussion of All Recorded Lunc Cancer Cates, Living and Dead, at ,-tios ano Thciiord Mine* Although a simple enumeration ol all the known or cut* pec ted cases of cancer of the lung in tbsst area* has no particular value from a statistical point ol view, it it ol interest to summarise 0200 . ,--- \ B*. such cases lor the record. There were :,ac death* pr;sr to the oeginarrg of the tunc period covered by the study, including one in which the diagnosis ui mediastinal lymphosarcoma. All of the*e nan* cases oteuTred at Thetlord Mines. It it somewhat surprising that there i* eo record of any lung cancer death* am eng the Atbeito* group is the interval preceding the beginning of the *tudy and equally o that so caaet have bees reported in 1956 and 195 7, During the period covered by thu* invaatigation, there were improved case* and three auapccted cate* at Thetford Mint*, a* well a* three proved cam at A*be*to*. Through 1956 and to date in 1957, there were eight death* at Thetlord Mine*, six ol which were merely suspected and included *uch diagsoae* a* mediastinal lymphosarcoma, maaothelioma, cancer of the leg with metata** to lung, ab*e*( of lung, and cancer of the pancrea*. One other *a* diagaeied on the batia of x-ray only. In addition, there are now living four cac* is which the diagnostic evidence ie etrongly auggestivc of lung cancer. Thit it a total of 15 caaet of all type*, including ten "suspected" but unproved caaea, and four that are atill living. The renaming 19 constitute the total of proved cate* of cancer of the lung in both area* since 1940. Sixteen of these have been at Thctford Mine* and only three at Asbestos, all of which occurred during the period of the study. The proved case* averaged 59 year* of age at death, and varied between J? years and a! year*. Their working span covered 0201 70. period* varying between t minimum of 14 year* end maximum of 17 years. Only three men. bed let* then IS years el employment in the industry. Seven mtnj those on whom such information is available had a weighted exposure placing theta la category III. sad six worked ia aa exposure represented by category 1. Although they were subjected to post-mortem examination, there were three among these proved iuag cancer cases ia which we do aet have information regarding the prcacace of asbestoais. Of the remaintag 17, asbestosis was present in niae, although it was minimal ia two, aad two pathologists disagreed regarding its prtsencs is one. Sight of the proved lung cancers, therefore, were not accompanied by aabestosis. o?o~ 71. vi. SUMMARY AN5 CONCLUSIONS loterett in the quetliOn cf whether there me/ he in a*, sociation berwseo luag eancer and a*be*te*i* or exposure to atbe*. to* bo* beta evident since the report in 1935 by Lynch had Smith of a e** ia which lung cancer aad e* be* to tit were both present. A* additional ca*e* ia which the two disease* coexisted were reported, a causal association appears to bare been gradually accepted by many authors, although a few worker* considered the correlation to be in. conclusive. Cases of long cancer which had occurred among the as bestos miners ia Quebec bad been carefully recorded over the years, and the preaeat study was commissioned ia aa effort to determine whether causal relationship did, ia fact, exist between exposure to asbestos and cancer of the lung. Jteference to the literature shews a rsmarkabl* uniformity both of method and of conclusion*, la general, the method bat beta to tody a circumscribed strict of case* of a*b**to*i* sad to enumerate those ia which luag cancer occurred. The series may ceaaist of cases coming to autopsy or of dtaib certificate* mentioning aabeetesis, and the total number bat served at the denominator by which the number of lung cancer cate* t* divided to produce a certain "incidence rate''. This rate, a* reported by various author* ha* been continently high, and it* uniformity i indicated by the following tabulation. 0203 Author Mcrewcther Wedler Wyers Lynch L Cannon Gloyne Totals Asbesto*is Deaths 34a 92 1 IS 40 121 712 . Cancer of Luntj 55 15 17 3 P 107 Percentage Incidence 16.016.3 14. i 7.5 14.1 15.0 r Ik notable characteristic of all previous publications is the adherence to tbs development of s percentage relationship in , " ' (63) a relatively small sad very selected (roup of esses. Only Doll, among all of these authors, has described a representative population group and studied it for the mortality rate from lung cancer and corn* pared this rate with that for a control group. His investigation dealt with only 113 men in the study population. itj.- Siaee most earlier studiee bad 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 men* tioned, it was apparent that they could not fulfill the requirements of an epidemiological and statistical approach to the problem. The pre sent 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 tbe asbestos mine* m Cuebee. based on medical records at the two mam locations 0204 73. ef these operation*. Conoru were defines according to ctrst;.*. cri teria and 411 worker* who met thete criteria were included in the study. Through their medic*: record*. d*t* relative to their choreeteriitic* were collected and their status at the end oi a six-year period of observation wa* determined. In the caee of those who had died, an exhaustive search of death certificates and-insuranct records was carried out in order to determine as nearly as possible the exact cause of death. Mortality rate* from lung cancer for the general population of the Province of Quebec and it* various eountics and for the Dominion of Canada, as well a* the United States were calculated from statistic* collected in the appropriate places. Comparisons el the rates obtained for asbestos workers and lor the other population group* were made according to accepted statistical methods which hsve been explained in some detail is section IV. Record* were obtained on 6091 person* who fulfilled the criteria of our cohorts. It was not possible to trace 133 of these Iot the whole period, hut 5771 of the remaining 5956 were found to be still living in 1955 or later. Of the 167 Imown dead, cancer of the lung was considered to have been reasonably proved in nine and to be strongly suggested in three. The members of tbc cohorts were studied with respect to age, length of employment, a weighted average of their exposure, and their smoking habits. Pour thousand, six hundred and stventv-three 1 . 1 . - H. were fevnc to be smoker* *itbin the definition 0/ tha: leem 11 ^ice in this study. Thirty-four percent of the cohort were more this 4$ years of dge, sad 30% bad been employed for longer than 30 years. Thirty percent had a weighted exposure which placed them in cate gory ill. The mortality rates for lung cancer, as computed on the basis of tin "proved" deaths among the Thetford Mines cohort and three "proved" deaths among the Asbestos cohort, were Z?.h per 100,000 for the Thetford Mines group, and 22.2 per 100, 000 fv'the Asbestos group. When the three "suspected" cases were added, the "total" rate for ihe Thetford Mines cohort rose to 41.3, The rate for the combined cohort was 25.3 per 100,000 for "proved" cases, and 34 per 100,000 for "proved" and "suspected" cases. The importance of the suapectcd hut unproved cases in determining these rates has been reiterated be cause it is likely that such cases would not be included in the statistics for the general population. According to the findings in this study, the mortality rate from lung cancer does net appear to increase with length of exposure or with degree of exposure, a fact which presents strong evidence agamst the carcinogenicity of asbestos. On the other hand, the study indicates that cigarette smoking is a very important factor m the in cidence of cancer of the lung. A comparison of relative frequency of lung cancer and ashestosis is lets reaaturtne. hut we believe that this is because of an . 0^06 *5. -v.: cases. Tut i; stt-ei-.ii.s indicated by tie medical record* is Ur below that which would be expected on the basis of oil previously published figure*. Naturally, when the diet of lung cancer are compared with an artificially tow figure, it* relative incidence will be higher than it ihould. However this may be, 12.5 7* of the recorded carer of a*be*to*i* in thi* *tudy developed lung cancer, a figure etighUy lower than those quoted by authors who confined themselves to thi* type of comparison. Comparison of the experience among the asbestos miners .. ** with that of various segments of the unexposed, comparable population shows that the observed number of deaths among the miners is not significantly greater, Tbe rate for proved cases among tbe asbestos miner* (25. S per 100,000) comparts well with tbe rate of 22.5 per 100,000 lor the rest of the Province, and 20. 6 per 100, 000 for acull males throughout tbe Dominion of Canada. It also compares satisfacto rily with rates of 57,2, 25.3, and 28.0 obtained from various sources for adult males m the United States. Finally, in this matter of com parison, it would appear that the world-wide experience of persons ex posed to asbestos dust n net worse wub respect to lung cancer than that of the unexposed population. The counties surrounding the asbestos-producing areas, and in which it ii presumed most of the asbestos miner* live, have almost identical mortality rates with those of eight counties widely scattered r E~ T6. through the Provir.ee, and are lower than those for the rerr.ainaer c.' the Province, and much lower than the rate /or MentreaL. Sine* 1940, there have been 19 caret m which, the diag* notit of primary cancer of the lung may be considered to have been proved. Approximately half of these cates were associated with as. btstosts. All but one died in the recognised "cancer age" and at least ne*third had only the lightest exposure (category 1) to asbestos dust. Conclusions ; On the basis of a careful and detailed study of what are believed to be complete and reliable data, it seems fair to conclude that the asbestos miners at Thetford Mines and Asbestos in tht Pro vince of Quebec do not have a significantly higher death rate from lung cancer than do comparable segments of the general population. Despite this, (he results suggest that a miner who develops the disease asheslosis does bave a greater likelihood of developing cancer of the lung than a person without this disease. We suspect, however, that under, reporting of asbestosis case* bad led to a fallacious finding m this con. nection. The death rate from lung cancer in the areas continguous to the asbestos operations is comparable to that in areas widely scattered throughout the Province of Quebec and is lower than tn some urbanized t.i wf.hin t.-.v Province. CJ3uo u. The present study indicates that the efleet el cigarette smoking is a much mere isporta.it consideration m the production c litspauttr than is exposure to asbestos, and ut tbit respect, it tend* to confirm recent studies dealing with the el.'eet of smoking. The value of this investigation would he considerably en hanced by continuing the observation of the cohorts formulated herein on a year-by-year baais. It ia strongly recommended that the chest X-rays of all workers be submitted to an independent reading lor the diagnosis of asbestoses, since an inaccurately low incidence rate for this disease creates an artifically high relative incidence for lung cancer. 0209 78. VI. BIBLIOCRAPKY 1. Adler, I.. Primary malignant growth* of the lung* aod bronchi. London, Longman*, Croon 6 Co., 1912, p.39, 2. Alatcio, *cobar R. Bronchial carcinoma; review of two hundred ca*e*. J. lute mat. Cell. Surgeon*. 26: 375-379, September, 1956, - 3. Allen, M.L. 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