Document Yrvpg3DwrxD086e4nXaJnVv8K

ruAiN i ir-r s> .r, ja srrr- > 5 & y Asbestos rMi Tkr mi T<>< Uerticmi A *, }*C4 *-w j. f :: :r, c#py*tM l*G4. *V Ar<H A/**/**#* i"C.~rtl J .-.jAmkA -idfliSdHMIHAJiDf 'S Exposiu-e and Neoplasia DUP 093 ^300 Irving J. Stlikoff, 3/D, Jacob Churg, MD, and E. Cii)Ivr Hammond, DSc, ,Ycie York Building indci insulation workers have relatively Ji-hi, intermittent, exposure to asbestos. Of 632 insulation * orken. who entered the trade before 1943 and were" traeed through 1962. forty-five died of eaneer of die lung or pleura, whereas only 6.6 such deaths were e* petted. Three of the pleural tumors were nte*othe!ioma>; there was also one peritoneal mesotheli^ ma. Four mesotheliomas in a total of 253 deaths is aa exceedingly high incidence for such a rare tumor, la addition, ao unex pectedly large number of men died of eaher of the uoniaeh, eolon. or rectum (29 compared with 9.4 expected!. Other can- ' eerswere not increased; 20.5 were expected. 22 Recurred.Twelve men died of asbestotie. ALTHOUCH PULMONARY CARCINOMA had XJcbeen observed in the earliest studies of asbestosis, association betwee n the two conditions was *u.n w|s^eiru iff AaViicu <mu dimiu IS 190S. AQ* diaeoa! reports of tueb association followed. Feehaps the most striding data wxs prewent-d in the annual report of the Chief Inspector of Factories of Great Britain for 1955.' Every death with as-bestosis in the files of the Factory Department, from the first recognition of asbestoiis as a disease entity, was studied. Altogether 365 such deaths were recorded (1924-1955). Sixty-five or 17.SS were found to be accompanied by cancer of the lung or pleura. DolL* after reviewing tbe problem and add ing data of his own, concluded that lung cancer was a specific industrial hazard of heavily exposed .asbestos workers. Nevertheless, some invest:gator? have held that, while these observaoons might be suggestive, they did not establish aa- increased incidence of tara--DOtr.a of the lung is pulmonary asbestosis, and - further, that the association w as unproved. "The factor of selection was considered a poten tial weakoess in evaluating reports of autopsy -series. It w-as noted that complicated aod unusual smses w-ould be more likely to come to autopsy, -thus raising the apparent frequency of associated lung neoplasms.* Further, it was argued that atttopsy statistics, which dealt with particular groups -of those wlio died, do not reflect total populations of .-ubestus workers.' Additional reservations were based on the frequent absence of data regarding Trim* lit# Oiwmmmi t4 TlM*ar D*#*#, Drftwii'trfMw* mi M#**trim, Um 09fiuia#>l mi PafMtvfl, lt#aM hmw HniMai, .. %mmd M f*n** immmt mi tfc# nwnt * r#4i>4wT m6 tK ** CiUi* *U OrU ! tUf exposure, smoking habits, and personal history, on the size of series, and on inadequate histological verification in some cases. NVithin the lost few years a number cf additional problems' connected with asbestos exposure h.tve appeared, making clarification and resolution of the foregoing statisticad uncertainty a matter of con siderable concern. First, there has been greatly increased use of the various types of asbestos I a five-fold increase in world utilization of tins group of minerals, from 500,000 tom to 2,300.000 tons per year in the last 30 years), as well as a greatly in creased number and variety of industrial applica tions of asbestos (over 3,000 such uses now re corded). Second, suspicion has been growing tint malignancy associated with asbestos exposure may include neoplasms other than carcinoma of die lung. Thus, a significant relationship has been claimed between diffuse mesothelioma of the pleura and peritoneum and asbestos exposure.* This communication is concerned with invest!gznnas undertaken to study tlie lollowinc tactors: (1) tne incidence of deaths due to pulmonary car cinoma among a group of workers exposed to as bestos under United States industrial conditions in the past several decades, (2) whether or not such individuals would also be found to have an increased risk of other neoplasms, and (3) whether such risks would be present in an industry other than the asbestos-ptoducing or asbestos-products industries, with which most reports in the past have been concerned but which would not nec essarily represent the most important areas of as bestos exposure at this time. Further, it was hoped that studv of an industry xvith asbestos exposure of limited extent and intensity would throw some light oo the potential problems associated with minimal exposure to asbestos. Materials and Methods Our investigations have been concerned with 1,522 members of the Asbestos Workers Union in the New York metropolitan area, member, of New York LocaJ 12 and Newark. NJ. Local 32 of the International Association of Heat and Frost Insu lators and Asbestos Worker,. .As the full title im plies, these men arc insulation workers. Although the union is eonxideted one of the hiuldmvt-tr.uU- unions, its members do insulation work in a va riety of iudustrii-s. iniitidiiis slupl'uiMiuu Called "luggers" in Great Briluin. they arc often desig nated "pipe cuvercn," "insulators," or ".isbestos workers* in this country. -- -- ,,t .i,,. nldi-st in the cxiitntry. Vel US. So I L\l u-'. 1." i_iK1.11 i u *u Thr N rw York local, ail tlic "Sil.unot'Jc*r AKWK i.i lion of Build ami Pijv Frilcrs." xx.in the firs! union of insulation workers in the United State*- it amal- g.lMJlvd with oilier locals a* the current Aslx-xtos Wmkerx Union in 1*112. The stability of this union hat been reflected in the stability of it* member ship rolls. "Omv a piivvoverer. always a pipeem- rrrr* ha* hern of rptdrminlncirni importance to us and has made this primp of men particularly suit able for the study of long-term effects of asbes tos inhalation. Unlike unskilled svorkers e\posed to asbestos inhalation in poorly paid industries, there is little labor turnover among insulation xx-orhers. Accurate empim-ment records are main tained by the union, which has also been con cerned with health problems in the industry. The trade was badly hit during the depression: some men had to drop out and very few were added during the 1930V By the end of 1942 the union rolls consisted mainlj- of men with consid erable experience, plus a few who joined tn 1940. 1941. and 1942. Between 1946 and 1962 union membership increased substantially. Source of Dare -From union records, a list was prepared of every individual who was a member of either of the metropolitan locals on Dec 31. 1942. or who joined between that date and Dec 31. 1962. No one was omitted, whatever his subse quent work history. The 1942 list included 632 men; 690 men joined after 19-42. Personal data were obtained from union records, and the work history of each man xvas detailed, indudinc withdrawal from emnlovment fwar *er- vice, other employment, retirement, illness). These data pave the baseline for calculation of the onset and duration of exposure. For members wlio had died, records of the Health and Welfare Fund pro vided date and place of death. Copies of death certificates were obtained on all but one of them. Autopsy protocols, histological specimens, and hos pital records were obtained and reviewed m those deaths, approximately one half, in which the ter minal illness had occurred in a hospital. Ttatirtieal Analysis.-Previous studies have sug gested that neoplasia associated with asbestosis sel dom occurs until 20 years after first exposure to as bestos dust. Therefore, we decided to limit the present analysis to men with such an exposure history. Our complete records cover all members of the union (including active and retired mem bers, both dead and alive) during the 20-year period from Jan 1, 1943. through Dec 31. 1962. However, with few exceptions, the only men with a history ef 20 years or longer since first exposure to asbestos were the 632 men on the union rolls as of Jan 1. 1943. (The exceptions x*ere a few- men who joined the union after Jan 1, 1943, but who had been employed previously us asbestos xvorkers elsewhere.) Of these 632 men, 255 died before Jan 1.190. ! Table 1 --Ujn Y*jrs of Cxa*i',et ef 632 tvsruss Warhtn Ct0e%*d to Atotot Own 20 "**** or lOhjif Tmm 34 34 40 44 ........ ........... 44 44 .. , ......... 40 44 ......... ....... 54 if ............ ...... 90*4 .......... .. ... 94 *9 ....... ..... 70 74 ......... ... ....... 74 7f ......... . ....... 0*4 ............. 99* ....._____ 140 i4 S4 0 2)0 4 534 4 391.4 312.0 272-0 2340 93.0 32.4 4.4 3-4 UfH ............ 2.912.0 144ft. 2942 114 0 419 4 374 0 JW 0 390 0 341 4 it: o 114.4 70 0 It.! 2J5 2.471.0 244) 14)7 7.0 241 4 430 0 309 0 3)90 )44 0 799 O 237.0 70S 39.4 90 2.339.1 1441 1943 21 0 70 0 )U 4 402 4 741 4 74) 0 710 0 1)7.4 75 0 21 S 13.5 2.022.0 Of these 622 mm. 339 had been exposed to as bestos dust prior to 1924. In other words, as of Jan 1. 1943. 20 years dr longer had elapsed since these 339 men were first exposed. The remaining 293 men reached the 20-years-sinee-first-exposure point at some time after Jan 1, 1943, and before the end of 1962. The 33f< men xvbo xxcre first exposed prior to 1924 xvere counted in each of the 20 years 'or up to the time of death of those who died). The 293 who xxere first exposed in 1924 or laier "'ere counted only after they reached the 20-vears-sincefirst-exposure point (those xx-ho died being dropped at the time of death). When the statistics were completed, t found that w-e had records covering a total of 5,737.5 man-years of experience of men with a history of 20 years or longer since first exposure.to asbestos dust. Of the 6,737.5 man-years, 1912.0 were in the fivevear period 1943-1947 ; 2,478.0 were in the oeriod I94S-I532. 2.2363 xvere in the period i333-j537; and 2,011.0 xvere in the period 1956-1962. Table 1 shows the age distribution of the mun-yeers in each of these five-year periods. Table 2 shows (1) the average age-specific death rates of all US xvhite males during each of these periods, and (2) the axerage age-specific death rates from cancer of the lung, pleura, mediastinum, and riachea among US x'hite males during each period, as reported by the US National Office of Vita! Statistics. The man-years xvere ilien multiplied by the cor responding reported US death rates to ascertain the expected number of deaths under the null hypothesis that the death rates of asbestos workers do not differ from death rates of all US xvhite males (both age and date being taken into consid eration). The results are summarized in Table 3. Result* Total Deaths.--During the first five years (19431947) only 25 deaths occurred among the asbestos workers, xvhereas 39.7 deaths would haxe occurred had their age-specific death rates been the same as for all US xvhite males during those years (Ta bic 3). In other xvords. at the start of the study, the asbestos xvorkers had beloxv average death rates. This is by no means surprising Indeed, such DUP 09303C1 DU? 09303 24 asbestos Oirosunc-scuvarr et al JAMA. April C. 1904 Tftbt* 2.--ToUi Ocitnt 4nd Deaths ^rom Cancer of the Lunj. B'onchu*. Pleura. Medatt>num. and Trachea per iO.CCO wnae Meie* per Yar# mu*? 1949.1*52 kf ^ TMH snrr------------" "jl 40*4 - - 59 45-4*_______ 15 six. ______ ,, ' ' ui 59________ 1M lfri _______ m 54* . "455 W* ----------- 434 7S-7f ~ *77 IftM " Tii IW________ 2.42} (.** C*c#rt ' T#ii _ " ' 30 1 49 2 71 4 174 9 It* 7 71! 7 417 9 405 15 * ' i.lil 9 2.142 lwf ... 1 3 5 C 19 U n 19 4 7 1**1 1*57 Tl#i 34 43 77 115 174 774 4)4 544 171 134* 2.017 Lw*t 1 t 4 18 14 17 14 14 12 te>Omttt* rttta ***fc*t>A***<*)<*i*a*irt&tno# %uj** mi-iuO;r*** **# *Si*,**iiw% *A<<` ytii 1Dtth rattt *<* onctf t< *** WAp* ****evt. ****. fNMMmwn. t* 1*4* * he. lid 1*4 tne'taftfr. t% t 1*54.1*62 T*t#i 75 47 79 124 174 277 4U 407 44 1.9 if 2.144 lunt 1 1 5 7 31 17 h 22 17 15 22 ** ** mf<m **'* *t (Ml M*. 47M prior if almost ahv.iyi found in the first few yean of a prospective epidemiological study of this type. Tlie explanation is almost certainly as follows: The 612 men in this analysis were actively employed as as* best.! workers in 1912. Since disability from illness or other causes precludes employment in a trade of this type, these men were presumably well (or at least not disabled) at the start of the study pe* riod. Almost any group so selected as to exclude the ill and disabled has a lower death rate during the ensuing few years than does the general popu lation. since ill aod disabled persons luve extreme ly high death rates. A selective eBect ot tms type 'gradually wears ofi with time and largely disap. pears within five to ten years from the time of in itial selection. During the second five-year period (1WS-1932) the death rate of the asbestos workers was slightly higher than the death rate of all US white males, ie. Si observed deaths compared with 50.S ex pected deaths. In later periods, the death rate of the asbestos workers was proportionately higlier. For the period 1963-1957, there were S5 observed deadu compared with 56.6 expected deaths, end for the period 195S-1962. there were S3 observed deaths compared with only 54 .-J expected dcatlis. Table 3.--Observed and Expected Number el Deaths Amonj 632 Asbestos Workers Exoeseb to Asbestos Oust 20 Years or Lsneer CauM of 2*43. 1*47 Tvtftt. (iun ....... 24 Ohfvtg MtitMl Until'. (US -I-I. ,, 19.7 tiAcir. all *#* . ... ... 19 Q&*r*4 C*MCl* (Vl Ni -- 5.7 ***' * OlMtsM UbMUM Mtwri) UpKIM (US A*( ... 4 4,9 0* !**. C*n. rrttwm ................. . Oltf'sH >**) 4 (U5 . 4 2.0 C**Cr* 0* Ml MM' >*% 4Mb* 4**4 .... --_ 3 06tr4 **> (ifMtH (US mittii . , 2.9 06Wt*4 (**( W0>*0*tl **1952 94 5Q9 > 9.2 4 2.4 4 24 9 42 l 2*53. 1957 U 944 24 13.9 13 2.0 7 2-4 < 44 4 m* 1*42 44 *4 4 39 9.7 It 2.4 14 24 7 10 7 2*4> 1942 254 2055 *5 41.9 4* 4.4 29 *4 22 29.5 12 Cancer of the Lung. Pleura, and Trachea.--In each of the four five-year periods, far more deaths from cancer of the lung and pleura occurred among the asbestos workers than would have oc curred had their death rates from these diseases been the same as for all US white males (Table 3). Altogether 45 of the 632 asbestos workers died of cancer of these sites, whereas only 6.6 such deaths would be expected from genera! US experience. Of these 45 deaths. 42 were recorded as due to bronchogenic carcinoma and 3 to neoplasms of the pleura. The pleural neoplasms were all recorded as mesotnetiomas. Thus it was found that the death rate from can cer of the bronchus and pleura was 6.S times as high among these asbestos workers as in the gen eral US white male population fboth age and dace being taken into consideration). It may be asked whether the high rate of lung cancer among these asbestos workers could pos sibly be attributed to an unusually large proportion of cigarette smokers among them. We cannot an swer this question directly, since we have not vet been able to ascertain the smoking habits of the men who died. However, the following pieces of evidence indicate that unusual smoking habits cansot account for the high death rate from lung can cer among these workers: \Ve heve interviewed 320 of the 3< i surviving members of the 1942 group. Table 4 gives a summary of the smoking habits in this group compared with a sample of men drawn fsom the genera! population of 1.12J counties in 23 states.' The un ion sample is somewhat inadequate since it does sot include the men who died and does not in clude all of the present living members of the uninn. Nevertheless, it shows that a substantial proportion of nsluvlus workers never smoked cm.trettes rrsularlv. Certainly the <V52 men in our unnlv- sis of deatli rates were uul all heavy cigarette smokers. In the general null* |k>i nihilism, lmig-c.im.vr death rates are about ten times as high among cigarette smokers ax among nnnvmokcrs. and the wTasiait : a; 'aw* ~ V%1 l h*, S X i.'.> *v;aiswv!*-: -- ..'.wi / t_ * .\ ^ TjW 4.--Smofcmf mj&ms of 320 Aotitot wo**n *DSfd to Ai&eitov Outt 20 *tr% or Cnrrpared With Simeif 8* Me from fnr Gtntraj hoou>t<on* *** *9. *e 4*4* SO SI 4f 7*+' " "1 AibHiat toa*rfv % IJ ___ I4.J ' 201 11.1 < awn tram Ciwul % ltJ If* rii J7.i AlWtlM MtAUffb A 4.4 ft i 10 1 11J 9% rtaartM ajr niffimani 6*orstl */ 7.1 if 1*2 21.* HHttrjr wt Aikeiiai W***<, % ft 1 714 49 7 42.7 Ctne'll 73*7 70 2 *0 1 it e dath rate from lung cancer increases greatly with the amount of cig.iretic smoking.* However, a large proportion of all men in the United States have history of regular cigarette smoling. From data in a prospective study on smoking.* it may be esti mated that if all men smoked a pack or more of cigarettes a day (it, if all the nonsmokers, cigar smokers, pipe smokers, and light cigarette smok ers had, instead, heen heavy* cigarette smokers) the lung-cancer death rate would be approximately 3.4 times as high as it is at this time From this we may conclude that even if fit our asbestos workers had smoked a pack or more of cigarettes a day (and, indeed, from our sample we know they did not), and if exposure to asbestos were of no significance, then their lung cancer death rate would have been about 3.4 times as high as the rate in the general US male popula tion. Clearly, the smoking habits of the asbestos workers cannot account for the fact that their lung- death rat; *.vaa ? 5 timaa -* hi**1*_tha* of white males is the general population. Gastrointestinal Cancer --Rather to our surprise, the death rate from cancer of tiie stomach and the death rate from cancer of the colon and rectum were higher among the asbestos workers than would be expected from the rates reported for the US white male population, calculated in the same way as for lung cancer. Twelve deaths from gastric cancer occurred among the asbestos workers, as compared with only 4.3 expected. Seventeen deaths from canter of the colon and rectum occurred among the asbestos workers, as compared with 5.2 expected. Ccncrr of All Other Sites.--The combined death rate from cancer of all sites other than lung and pleura, and stomach, coion. and rectum was not increased. Twenty-one such deatlts occurred among asbestos workers, as compared with 20.5 expected. Asbestosis.--01 the 255 deaths, 12 were due to asbestosis (pulmonary insufficiency, cor pulmo nale). The lapsed time from first asbestos exposure to death from asbestosis averaged 45.8 years, with a range of 32 to 59 years. Comment Carcinoma of the Lung.--The results with regard to carcinoma of t!>e lung are dear. Industrial ex posure to asbestos by insulation workers, as stud ied here, results in a marked increase in the inci dence of cancer of the lung, approximately six to seven times the expected incidence. Aiiogether. 45 (17.65) of 255 men with more than 20 years elapsed since the onset of exposure died of cancer of the lung or pleura. These data do not give the "incidence of cancer of the lung in asbestosis.* They relate to the spe cific conditions of our investigation: to a group of men with only intermittent exposure to materials containing limited amounts (often 25 to 20") of asbestos 'under working conditions varying from very dusty, as in extracting old insulation in closed quarters, to those with little dust exposure, as in building construction in open air. Moreover, (hey relate to the relatively recent past in a trade with the shorter work week of the strong building trades unions, it an era when industry has been aware of potential asbestos hazard and the working popu- I . I ts . #. SdllWia IMU MAW MMttC tOlIKMMMMCil Wl ywsytlUAi risk associated with dust exposure. These data would not necessarily apply to asbestos exposure in other industries, such as the factory production of asbestos products, the asbestos textile industry, etc, where conditions of employment might be quite different. Our results do not contradict tbe even higher incidence of lung cancer suggested m other studies they are merely a shade less strik-. ing. Diffuse Pleural and Peritoneal Malignancy-- Mesothelioma.--Determining tlie incidence of dif fuse pleural mesothelioma is complicated by the insecurity of .its histologicnl verification. While some pathologists will so categorize a high propor tion of diffuse pleural tumors, in the experience of others it is a very rare tumor and may be mim icked by anaplastic peripheral carcinoma of the lung and diffuse fibrosarcoma of the pleura. It is difficult to evaluate completely the published re ports of diffuse pleural mesothelioma in asbesiosts in the absence of complete details of each -case. To the present time, there has been no informa tion concerning the incidence of diffuse pleural .mesothelioma in asbestosis, since the published cases are reported without reference to a total pop ulation in which they occur. Nevertheless, the DUP 0930303 ' <ii8atCTt jrgilih r-- :: 's.r-:i^w 2 asbestos exfcxvbe-seukoff ET al IAMA. April 0. IMA growing number of reports of individual eases suggests that time tumors arr pcrlwps becoming relatively frequent complications of asbestos ex posure. Our observations in this scries are similarly sug gestive. In three of the 235 deaths among the men who had worked for 20 vi-ars or mnre. the exam ining patholocist considered llic death due to dif fuse pleural mesothelioma. and in the two eases In which w e lave been able to review the histological material, the histological appearance was that of ten so categorized, and asbestos liodics were pres ent. This incidence of more than 1*1 of deaths from pleural mesothelioma is strikingly high for a tumor which is generally considered to be extreme ly rare. In one case in our series pathological exjunination suggested diffuse peritonea! mesotheli oma. Tiu's single experience is too fragmentary for evaluation. Gastrointestinal Carcinoma.--Isolated instances of gastrointestinal carcinoma in the presence of as- bestosis have been known, but tlicre have been no data to indicate that these 'sere mnre than coinci dental findings. Among the asbestos workers studied here, cancer of the stomach, colon, and rectum was three times as frequent as expected. These data suggest tliat there may perhaps be an etiolocical relationshin between industrial asbestos exposure and carcinoma of the gastrointestinal tract. Znviranmcntal Asbestos Eiposurr.-The recent demonstrition, by South African * and British * investigstors of pleural and peritoneal neoplasms among individuals who had chance environmental exposure to asbestos many years before raises the very important question of possible widespread carcinogenic air pollution. The possibility of en vironmental exposure has Ions been known. Soon after the initial clarification of asbestos is is a clinic entity, Haddow " demonstrated asbestos bodies io a man not employed in the industry but living next door to an ashc-iios f.iciory. Tin's finding was later mirrored in the finding of chronic ber\i!mm dis ease among residents of a community n*ar a beryl lium fnctury." What ts new. however, is an appre ciation of the potential extent of the problem. Thomson and associates " have reported the fre quent findings of asbestos bodies in the lungs of urban dwellers. Among 6,312 individuals x-rayed in an area about an asbestos mine in Finland. Kfviluoto " found -JOT cases of pleural calcification of the type cliaract'-nstically seen among asbestos workers, without obvious cause. In a comparable area without any asbestos mine, no eases sscrc found among 7J0I persons x-rased. It should be noted that these were not people ssho worked in the mine--none did-but, rather, were farmers, housewives, and others who lived in the general location. In one subject svho came to autopsy, polarized-liglit microscopy demonstrated asbestos fibers in the lung. Similarly, the lung of a cow- graz ing near the mine also showed the presence of asbestos. A particular variety of environmental exposure may be of even greater concern. Asbestos exposure in industry will not be limited to the particular craft tliat utilizes the material. The floating fibers do not respect job classifications. Thus, for ex ample, insulation workers undoubtedly sliare their exptnufe whu linrif MUiMtum io utuei intimate contact with asbestos is possible for etcc* tricians, plumbers, sheet-metal workers, steamfitter*, laborers, carpenters, boiler makers, and fore men; perhaps even the supervising architect should be included. 1 200th St, New York 10029 (Dr. Selikoff). This study ti supported by thi Health Research Coun cil of die City of New York. Cooperating in this investigation ere the executive of ficers of the International Association of Heat and Frost lnulttors and Asbestos Workers, Washington. DC. and the office!*' snd memlwrthip of the New York and Newark. NJ, locals of this Union. References 1. Lynch, K.M., and Smith, \t\APulmonary Asbetiotit: Carcinoma of Lung is Asbeto*Sihcost&, Amti / Cancer 2C3G-H (May) 1933. 2. Annual Report of Chief Inspector of Factories for Year 2933. London; Her Majcity's Stationery Office. 2956, aasnd 6, p 206. 3. Doll. A.: Mortality From Lung Cancer in Asbestos Voilw. 6r* S Induat Med 12.61*6. 2955. 4. BoMig. H-, and Jacob. C.: Xeue Gesidurpunirte iiber <dea LunctiJcrebt der Asbesiarbeiter. DcufacA Med Wechr SI *231-233 (Feb 17) 1*2M. 5. Braun. DC, amt Tnun, TO.: Ep*drmdn\-K*4l Simiy of Lung Cancer in A*be4n Maten, AA/A Arch (mduur Hvuhh tjmi. ) JlrtS. 6. Wagner, J C.; bii-giti. C~\,, amt Mnrchaml, F.. Dtiluac rieur.U Mnothduxiu ami HipMiire in North YWnUrn Ope I'timme, In/ i ittluUr Mvti 17:200-271, 2900. 7. Hjfflnvrtnl. EC., am] L: Smoking (labiti of Men am) Women. J Sut Cu>< t iu*t 2?i4!')-442 (Vug) 11X32. fi. Hammond, E.C,, and Horn, D.; Smoking and Death Rates: Report on Forty-Four Months of Follow-up of 117,* 763 Men. I. Total Mortality; II. Death Rates by Cause. JAMA IC5:I159-1172 (March I); 2294-2303 {.March 25) 2956. 9. McCanghey, W.T.E.; Wade. O.L.; and Elmes. P.C.; Exposure to Asbestos Dust and Diffuse Pleura! Mesotheliamas. 9nt Med J 2:1397 (Nov 24} 1962. 20. Haddow, A.C, in Report of Annua! Meeting of British Medical Association, Manchester, 1929, Lancet. 1:230-232 (Aug 3) 2939. U. Chenier. C.. Clnmiie Pulmntuiv CwM*m.itnss in Residents of Community Neat B*ryilmm I'l.mt. Thfrv Autuptn'd CLum., Ann fn/rrn Mvtl 32.1U2S-Id IS (/mud 12. Thomson, J.G.; KusthuLi, H-O-C., and M.icOmwikl. RR.; A*h***/ns At Modern Urban Hazard, S Aft Med ) 37;77*1 <J.m I'V 1002. 13. Kivduoto, JL: Thniral Cih i/icaUm as Rm*liJ*nJ*isif Sign of Non*Occuputoul Endemic Aiitlntili>lliie-A*U.*>torn. Aetn Ror/iVd Suppl 294, pp 1-67, iOCdi. DUP 0930304