Document MGQ10g0Z6VJKowxNNOJ2QzK4L

FILE NAME: ZD^D/ DATE: DOC#: ^D/ DOCUMENT DESCRIPTION:hZWZZ WZZ/ J.rn. CHAIRMAJ~ Al:II narnt:RS OF THE SYT'lPOSIUM. / / ' - -r f I was as~ed to present a paper on the topic Pulmonary Cancer in the Asbestos Industry, net on account of any qualifications ~ut because I happen tJ be in charge of a Clinic which has as its primary function the supervisio~ of the pulmonary condition of soille 4,000 asbestos miners; such a group of employees workin~ in a small radius of 5 miles offers an exceFtional opportunity to study the problem of cancer of tte lung in relation to ~he inhalation of asbestos fibers. PRELIViINARY Rfl'.':ARESo This question of pulmonary cancer among the asbestos workers is as confusing 'and obscure as the etiology and the patho- ~enicity of cancer in ~eneral. From 1920 - 1950 the ~edical liter- at..ire reports a series of 58 cases of pulmonary cancer and asbestosi Jbviously this list must be inco~plete but, nevertheless, one coulc ask is it s~und to think that the mere fact of detectin~ a total of 5g cases of rulmonary cancer during a period of 30 years is sufficient to establish a causal relationship when one realizes that in 1950 an estimated nwnber of 45,000 men were e:7!ployed in the asbestos industry, and that during that period a minimuo of 100, 000 employees have inhaled a significant a111ount o: asbestos .. eust? in the It is recognized that the ~nglish statistics publishe~. Annual Report of the Chief Inspector of Factories for the . - (rY\fr~v ~~5~t~~~i: - -'--- ... year 1947 seem to indicate a causal relationship between the factor asbestos and !JUlmonary cancer but, on the other hand, in South Africa with about the sa'le number of asbestos workers as in Great Britain, and when there is also a large number of autopsies and good medical control of all employees in dusty trades, the statistics do not indicate any abnoIT.ial incidence of pulmonary cancer. If the frequency of pulmonary cancer in South Africa and in the Province of Quebec is really not higher a~ongst the asbestos workers tha~ in any conparable groups as it seeras to be, is it possible to suspect that the asbest.os mining industry might be different from the Asbestos Textile Industry as far as card.nogenie activity of t~e as~estos i. s concernea'?. The fact that th e frequency among the 30,000 asbestos workers of t~e United States who are also workinE; in the Asbestos Textile Industry is not known to be hi~her, adds still more to the confusion. -tlhv is the standardized death rate fro!TI cancer of t!ie lungs in Great Britain 3 times higher than that in t~e United States - 2)1 in comparison to 7L3 (ra~es per ~iilion)? It would indeed be very informati.re to have so:;ie ans\'ters to this list of unanswered questions before being able to form an opinion; and it J1ie:ht be that a few answers could influence or modify any conclusion concerning a causal relationship. .::. . : . . . PURPOSE OF 1HIS S7ULY. The purp0se of 1~is investigation is to try to learn as precisely as possible the incidence of rulmona~ cancer in the gro~p of asbestos mining workers; to know the incidence in groups of employees with severe or insignificant exposure and to know the incidence in group~ with or without asbestot~c fibrosis. The Saranac Laboratory and many other investigators were interested in a complete study which would incl~de an epide~iolo~ical and an experimental invest:gation and which would rerrnit to ascertain whether or not a relationship exists between the inhalation of asbestos dust and pri~ary pulmonary cancer. This ra}:'er is a prel:i!"'linary and incomplete report of the epideI'liological ' investigation and the Saranac Laboratory, the investigation has been achieved, will publish a f:nal once report. KE7HODS AND rATERIALS. This study was rendered ~oss~ble m?inly because there exists in Thetford Mines a co-operative industrial clinic where all the eMployees working in the different asbestos companies are required to have a pre-8rr.ployment examination, rlus an annual periodic examination completed each time by a standard stereogram. At this clinic it was easy to analyse all the medical records, the death certificates, the protocols and the pathological findings of the necropsies and to review the series of chest roentgenograms of each e.Tflployee. Thetford ;,~ines being a small city of 18,000 it was also easy to contact and to discuss with the treating physician the nature of any respiratory episode, to have follow-up reports on any suspicious cases and to collect additional details on the cause of the ceaths. In su~mary, this study is based on the results and findings obtained from the analysis of the medical files of 3 1 957 eoplo:rees havin.e; worked in the asbestos industry fro~ 2 - 60 years, . on the findings from 53 necropsies, on the details collected from the death certificates, on the follow-up re~orts of cases sent to specialized centers for more complete investigation and dia~nosiso It is possible, and more than likely, thc..t cases of !='ulmonary cane er we have e~ployed that the results have been missed; nevertheless, we i:.hink th c.t a stand~rd procedure in this investigation and therefore are of sufficient interest to make this nublication worthwhileo RESULTS o Before submitting the results of this ~nv~sti~ation, it would seem proper to give a few routine ta bl es in orae:- to reach a better uncerstanding of this communication. ' - TABLE 1. FO?u1.A TI 011 SA.1.:?L.SD o A~e group diEtribution of 3,9B7 esoestos workers. I' AGE GF.0'U?S I ' Ii Num';)~r of l foployees I 15 - 19 - 20 - 29 30 I 39 40 - 49 50 - 59 1 , 60 - 69 70 & O':""er --TOT I 76 1113 '1091 766 505 307 99 c 7. u~ This table Eives the age group distribution of the s am rled ropulation and needs no comment except to ~ention that the average a~e of the asbeslos wo~kers is sc~ev;hat higher than that of the average indu:;tr~al worker; i.e., 35 in comparison to 33 for most other industrial ~roups. This :::-err.ark is logical when v:e know that the labor turnover in the Quebec Asbestos ~iining Industry is about the lowest of all the industries in the whole of Canada. This first table also shows that some 2,000 asbestos workers are 35 years of age and over - a repre- sentative ~roup for the study of a cancer problem. TABLE 2. Yee.rs employed in the e.sbestos industry by 3,~57 asbestos workers. Y-=ars in the b.dustry - l~umoer of ::.:pl oyees Ee..n - Years 2 - 4.9 5 - 9.~ 10 - 14 .9 15 - 19.9 20- 24.9 I 25- 34. s 135 l: Over 640 1920 1060 7420 645 7740 476 281 ~092 6182 I 546 1~742 309 : ! 12360 ?,SI.'.ARKS: 2,257 men have spent 10 years and o>er in the asbestos industry. The second table indicates the ~umber of years spent in the asbestos mining i~dustry by the J,957 employees studiedo Of course this table is not as significant as one indicating the specific exr.osure for each eriploy2e by categories; but after many attempts it has seeQed impossible to f~nd a common denorr.inator which ~ould permit to add to~ether the years spent in different degrees of exposure by the sa~e eGployee. The man-years exposure has in the mind of oany investt- gators no great meaning in ,general, but in this case the fact that 56,456 man-years.asbestos exrosure having given rise to only 10 confirmed cases of pulmonary cancer might indicate that we are not facing an acute problem, f I f The following table 3 shows classification of various r l exposures in the asbestos minine; industry. I realize that such ,. a classification could be discussed at length and possibly other dusty industries, it is impossible to translate with a strict mat}JeMatical precision the different concentrations of dust particular to each job. This classification is given notwithstanding its limitations because it is based on dust counts Derformed by different competent a~encies and, ~oreover, because we feel that a satisfactory classification is very useful in understanding more clearly scientific and medico-legal problemso TABLE 3. Classification of various 1 eY.posure in the asbestos rr.ining industry. Estimated degree of haze.rd. 0 1 2 3 4 5 Industrial Operations To~e.l dust count ~.P.P.C.F. of air :a..'!l.pled. Open Pit, Shops Less than 1 Open Pit: Box Loader, Cobber Du.mp Primary Crusher Dryer Concer.tre.ting Underground: e.11 jo~s under r.et condition. Short exposure of skilled employees 1- 3 1 - ~ v 2- 3 2 6 2- 5 3 6 Open Pit: dry drilling Secondary Crushing Storage Bin 2 - E 10 - 12 10 - 14 j l-er:::ent . fiber count L~s!i tha..ri 2 Less the.n Le~ s the.n 2 5 6 5 1-2 1- 2 4- 6 4- E Underground: cry drilling Grizzlies Shed Cobbing Shipping Shed: Cleaners, Pilers ~ill: 1.;illwrig;hts, Oilers, Sweepers. Testers. 10 15 5 - 15 3- 5 4 - 15 10 25 8 20 - 30 -1 3 2 14 - 1 10 - 14 25 ,- 9 20 28 This table indicates that the total dust count and the percent fiber count are both cor.stituents of the degree of hazard, meaning that a rather low total dust count may beco~e a risk when the percenta~es of fibers is high and inversely, that a high total dust count ma:r also become harmless in producing pulmonary fibrosis if the fiber percent count is low . The percentage of fibers in relation to the 0otal count is calculated for fibers 5 m:crons and over, and on the principle that only particules having a length at le2st twice its width are fibers. As you may see in the table, the industrial operations are grouped in 6 different cate~ories and these categories are asain sub-divided by a dduble line in two main groups. The upper group includes the jobs wfuich in our experience do not ~reduce fibrosis of som clinical importance and the lower group the jobs which can produce asbestosis. There is an obvious exnlanation why the r.Jer1 .-mrking in the open pit do not develop asbestosis and also why the men working a~ baggers might develop asbestosis, but it is more difficult to explain why some ind us trial operations '-d th about the same dust concentration as secondary crushing, storage bin on one part, the grizzlie~ and shed cobfuing on the other part have been classified in different categories. We admit that in adopting such a classification we have been influenced by our clinical findings to some extent, but also by the fact thRt in the operations of catego1 J, the fiber concentration is.more constant and work much heavier than in the operations of category 2. There is a marked differenc< in "the degree of hazard of categories 1,2 and 4 and 5, but the difference is not so marked for the categories 2 and J. This table is important in order to fully understand those to follow. It is true that the Main purpose of this presentation is to report the incidence of pulmonarv cancer in a group of J,957 asbestos workers, but the nude statement that 10 cases of pul~onary cancer have been detected would not be significant unless we can compare this prevalence with that in comparable groups. i This task of finding a good co~parable group or a control group in this study as in any similar studies is very difficult. We wish it had been possible to find a control group in other industries or in other industrial centers in the Province ' o~ Quebec or elsewhere in Canada. We soon realized that no other industries were interested in that problem of cancer of the lungs nor did they ha~e the necess~ry data for co~~arison. No other industrial city has ever had two-thirds of its male adult populatio o: the sa~e age group so clcsely ~edically supervi5ed with a c~inical and routine - roent~_,eno~raD. hic examiuation as has been done i:-i Thetfcrd }.~ines for the 2.ast 7 years. The mass =-urve~s in different cities did not help the situation; the findings were toe dificient doubtless because a too small proportion in the 40-year and over a~e group is taking advantage of the mass surveyo As a matter of fact, a mass survey in Thetford Mines in 1950 by the Provinc:al Department of Health did not detect a single case of pulmonary cancer as in most of the other centers, and the analy~ of the results is not very helpfulo It seems probable that the general increase in the frequency of lun~ cancer is not purely apparent, but when we observe in m~~y cities a sudden and the lung cancer mortality rates such as the increase in the City of J'Jontreal from 7. 7 in 1946 to 12. 9 in 194 9, we must adrii t that the medical diagnosis f?.cilities are responsible to an appreciable extent for such an increase. Therefore the exclusive analysis of death certificates in ~arious centers which do not have the same medical facilities, has to be used with caution not should it be used unless the fac~ljties are comparable. In .this study the comparative statistical analysis of the death certificates statistician the National was not used because in the of the ' City of Montreal and Cancer Institute of C2nada, opinion of tte official of the Statistician of the death certificates of the asbestos group consisted of a highly selective group and a si~ilar selective group was not available e~sewherec For all the reasons mentjoned above and t~e fact of being unable to make a better se~ection, we decided to compare the incidence of pulmonary cancer in different groups of asbestos workers who have been submitted to the sane ~edical investigation, and who at the same time were presenting enough characteristics to permit certain conclusions or impressionsQ TABLE 4. Incidence of pul~o~~ry cancer according to degree and length of expos~re by o.;e groups. ::'...:...::ber c.f ::l:-.plcyees ?revalence of ?ul:ronary Cancer GROUP lo GROUP 2. Unsibnificant exposure Sibnificant exposure AGE GROUPS 16 - 39 l I 2229 I 40 - 86 - 1367 I 0 6 (0.~4~) ' ----,_,l,_GE GrtGlJPS 16 - 39 I 40 - 86 I I I 56 305 ! l Il 0 4 (1 \",. -/"O'') Rfi!ARKS: Unii gnificant exposure includes rr.en wi tr. exposure 0-1-2 acd less than 15 years 3-4-5. Sinificant exposure includes only men with more than 15 yee.rs 3-4-5. (See '.racle 3) The usual calculations of the standard error show that the observed difference in percentages of incidence in the 2 groups (.87} is inferior to twice the Standard Error (1.346). This table shows that there is no statistical evidence that the incidence of pulr.icnary -cancer in the grot;.p 2 including the employees who have sustained severe exposure and all those who i have also developed asbestosis, is higher than in group 1 of employees those without significant exposure and without any clinical asbestosise -12- It is recognized that this table might lose a lar~e part of its meaning if it is shown that 2ny intensity of ashestos inhalation or any amount of asbestotic fibrosis could be considered as cancerigenic because then a large number of emrloyees in group 1 will be transferred to group 2 and it is orobable that an unknown number of pulmonary cancers in the group 1 would also have to be transported to gro~p 2, changing raGidly the observed difference in incidence as well the conclusiono As a logical complement to this table, we wish we could ~ive a long series of other tables showing the incidence of pulmonary cancer in 'groups w.ith recent or remote exposure; i~ groups with gradual exposure of 1-2 to 15 years or a similar exrosuie of lodg duration, 15 years and over; also in groups with extensive exposure and asbestosis or without asbestosis. The data obtained from such tables might tell us in the hypothesis of a causal rel~tionship whether the inhalation of ashestos dust is mo::-'e important than the rresence of asbestosis itself also what approxi~ative degree of asbestos inhalation can ~e considered as predispos~r.g to cancero !\u.'!lber J.-..:t::i :::s ied l:u1iber of ::"-.: lrc cna.ry Cancer ?ere E:.!'"it in :::ac.b Group TABLE S. Cor1pere. ti ve Incider.ce cf F\.:lrionary Cancer in 2. i;roups of 53 Autopsied f..Eoestcs workers. I I l GROUP lo ' Emplcyees v;ith Asbestosi~ GROUP 2. :E:::plcyees wit.bout Asbestosia TOTAL 34 19 53 4 t.:.., 10 11.7':[ ' Zl. 5% This table shows the prevalence of rul~onary cancer :.r. a series of 53 autopsies asbestos 11orf:ers- h2vi.nis worked in the asbestos :ninir.p; industry from 17 to 40 vears in di.fferent d~grees of exDosureo This series of autorsies is not as import2nt as the series published in the Annual Report of Great Britain for the year 1947, but can be considered as less selective and more representative in not being conposed from cases of asbestosis exclusively but composed of all the employees who happen to be autopsied; although it should be mentioned that there was an -14- involuntary selection in the sense th2t rnost of these employees have been autopsied because they were presenting some respiratOD' symptoms. This coincidental selection might explain to some extent the high percentage of cases of asbestosis, but in many instances the amount of asbestotic fibrosis detected was described as minimal and of no clinical impo~tance bec2use not sufficient to produce symptoms. Because the o~served difference in percentages of inc~dence is inferior to twice the Standard Zrror, this table does not reveal a statistical evidence of a causal relationship between asbestosis and 'pulmon~ry ca~:er. , ~ c. ...L l.. employee~ who die, it remains difficult tc explain why i:-i our series there are less c2ses of pulncnary c2ncer in the asbestotic group and I think we h~ve here a gocd ill~stration as to why many statisticians counsel nLlt t~ draw any conclusions from statistius based on a selective group even if such a gr0up be in the 'autopsy' category because the role played by the ~actor co-incidence might be too greato T.AbLE 6. tec.ths fror.i Pulrr,one.ry Cancer as a proportion of deaths from Can~er of all sites. 1S40 - lS50 rovince of Quebec .'..'tJ of ~ontr~c.l ,::ty of Quebec . .: ~., J. ~J c-f Thetford 1.:ine s H~ber of C!iDcer All forms 43643 15247 2543 172 NUI:lber of Pulmonury Cancer U93 918 94 9 Percentages 3.2 I 6.0 3.7 s.2 Table 6 was prepared for t~e p~rpose of determining if the ratio between the num'ber of cancer detiths all sites and the pulmonary cancer deaths was somewhat differe~t in Thetford Mines from the ratio observed in few ot'.-ier contr0l ,:;r0ups. First it should be mentioned that about 90% of t~e cases of pul~onary cancer in Montreal and 100% of the cases of the 'lhst.:'or-d Group are autopsy cases and both ~ities have t~8racic clinics, so these two groups are reasonably comparable~ ln ~uebec City for the specific period 19Li.5 - 1950 inclusiv~, 5% of all cancer deaths Here also pulmonary cancer. It wC:ts thought the..t had a special ractor existed in Thetford Mines the ratio between the number of total cancer and.the n~~ber of pulmonary cancer would have been differento The difference observed here is not sufficient to draw any conclus5on either positively or negatively., ':'ABLE 7o Co:npe.rative 10 Yee.rs Expectancy and 10 fear! Prevalence of Pulrronary Cancer in 2 cities. - i ' PLACE i . I I TI-.etford l.:ines I . ! ~'.cntres.l I YEARS 1941 - lS50 1941 - 1950 10 YU.RS :s:>..?EC TJ.J;CY 10o5 693 10 YEARS FRbv.AL::J(CE 9 856 : Based on U.S~ Public Health Service rteport 2537. A random populetion of ~8,833 giving a year pulmonrrry ce.nce" eY.p8ct- ancy of 7 ce.ses per 100,000 pcP'..:.lation. Table 7 was prepared at the suggestion of Dr. Philipps, ( Statistician for the National Cancer Institute of Canada who thinks that the comparative study of the lC years expectancy and 10 years actual prevalence of pulmonary cancer in Thetford Mines and ~n Montreal will be more informative and more conclusive than analysis of the mortality rates. According tJ the suriey of Dr. Dorn, takin~ random population of 4B,83J, an annual incidence of pulmonary cancer of 7 cases per 100,000 c~n be exrected, giving a year expectancy of 7o It is true that Dr. Dorn's survey was ~ade in 194Y-45 and that the year expectancy might havs increased recehtlyo As a matter of fact, ~atson of Saskatoon, Canada, found in 1948 a year expectancy of 8.5; t:1erefore, a year expectancy of 7 is a rather conservative standard. On that basis Thetford Mines with an average population of 15,000 for 1940 - 1950 period. is supposed to have 10o5 cases of pulmonary cancer, and the actual prevalence is 9 cases. Again it seems lo~ical to think that the 10 year prevalence for pulmonary cancer in Thetford 1~ines where two-thirds of its adult population is working in the asbestos industry would be hi,E;her than t~e nor:nal 10 year expectancy, should the factor asbestosis be considered carcinogenico smw.ARY. The etiology and the po.thogenici ty of the pul>nonary cancer in relation to asbestos factor is as obscure and confusing as those of cancer in general, and in presence cf contrddictory data, the many different aspects of the problem should be considerec before arriving at a conc\usion. The purpose of this study is to learn the incidence of pulmonary cancer' amongst the 3,957 asbestos mi~ing workers and to co~pare this incidence wit~ other comparable groups. This incomplete epidemiological re~ort is a contribution to a more complete investigation under progress at the Saranac Laboratory. According to the standard procedure the medical files~ the results of medical supervision, the annual stercograms of all the asbestos workers having worked from 2 to 60 years and the findings of 53 autopsies have been ~sed as materialo .. The results have been tabulated and compared to control groups and we think that the data collected in the Asbestos Mining .. Industry are not exactly superposable to the results found in the .._... . : . - ~: .. ... : . . -... . ......... . : ...... -:: .-: .:::: English Asbestos Textile Industry of G~eat Britain and if they do not permit to deny a causal relationship between the inhalation of asbestos dust and the occurence of oulmonary cancer, they do not seem either to bring any positive evidenceo / :liscJssion , .:J?. :;::oJ.~S: I wc.s inte.restec in I:r. C~rtier' s remc.rf.. t:.1c.t t:-!E: ::iuss survey / Ti1ose ere :10t re .<ti~1e l .<to)sies? ?Jio .~:s: cc.ncer to :or~~ers i1~t:1is ,r)<.:.rtic\ilc-.r gro..l). ?eric.ps tn=.t in:sr~ilce is true. e::-::cs.-..re to c.sbestos? Lr. Cc;.riter, t . - J..l'; .rJ.;.-."."_-..(".",'"t",'; .: - ~ ZF.. C.J.TI::?.: I cc :iot belieYe foere are an:, speci:'ic. s:,:a?to::r.s. If t:-,e fi lc:::oI::. o..:.r 5rc1:? we ;1c..ve m . ci. 9S c:.ses cf asbestosis. T{iese .!.:.C.ivic~[..ls ::.-.=.ve ::.aG. c. I:.::.r:..ec expcs:~re to e:.sbestos fer :;earf L'ld ::-..~1y of th~rn, c:: reac:-;.ing c..ge 5J to 55, a.re :-:-.c~e d.yspneic auci ses.:i to C.ie ::!ere re:.;:is..ly Id t..1.oit r~:uch C.ise~se. ::. :?-.:.o,:._:s: Of w::c.t o.c -'vhe:r die? d~sea.sss, so:n~ from brcLJ.C~liec~c.:.sis. --.--.- ,.e sig_este2. to :.r. Cut~er -:~.~-t ~:E: :L?... :r~:et.DS: Lid yo disccver hl;y cc.ncer CC;..ses, in so dcing? I>?... CJ.I:TI:='F.: Yes, '.:ith t.."1e X-rs.;>. llo cas-es -.~ere revec..led by t:1e ::ic.ss ::u..rvey; all tne c;c_ses ~eye detected in the cli!".ic. -- .' ..~ ::-- ! "')c..