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22 JAMA, April 6, 1SG4 Asbestos Exposure and Neoplasia Irving J. Sclil:off, MD, Jacob Churg, MD, and E. Cuylcr Hammond, DSc, jYrit' York Building trades insulation workers have relatively light, intermittent, exposure to asbestos. Of 632 insulation workers, who entered the trade before 1913 and were traced through 1962. forty-five died of cancer of the lung or pleura, whereas only 6.6 such deaths were expected. Three of the pleural tumors were mesotheliomas; there was also one peritoneal mesothelio ma. Four mesotheliomas in a total of 255 deaths is an exceedingly high incidence for such a rare tumor. In addition, an unex pectedly large number of men died of can cer of the stomach, colon, or rectum (29 compared with 9.4 expected!. Ollier can cers were not increased: 20.5 were expected. 21 occurred. Twelve men died of asbesiosis. ALTHOUGH PULMONARY CARCINOMA had ,/xbeen observed in the earliest studies of asbes- tosis, association between the two conditions was first suggested by Lynch and Smith in 1935.' Ad ditional reports of such association followed. Per haps the most striking data was presented in the annual report of the Chief Inspector of Factories of Great Britain for J9552 EverV death^\y;lh asbestosis in the files of the Factoiy*Tlcpartmcnt. Trom tile first recognition of asbestosis as a disease entity, was studied. Altogether 305 sticli dca11 is were recorded (1924-1955). Sixtwfiye were found to be accompanied by cancer of the lung or pleura. Doll,3 after reviewing the problem and add ing data of his own, concluded that lung cancer was a specific industrial hazard of heavily exposed asbestos workers.. Nevertheless, some investigators have held that, while these observations might be suggestive, they did not establish an increased incidenee-of carci noma of the lung in pulmonary asbestosis, and further, that the association was unproved. The factor of selection was considered a poten tial weakness in evaluating reports of autopsy series. It was noted that mnplie !wl-iM(L.UR11sua1 cases wou]cl^^).p.cp,,lijk?E39~P0fllc^.to,jmtopsv, thus raising the apparent .frequency of associated lung neoplasms.'1 Further, it was argued that au topsy statistics, which dealt with particular groups of those who died, do not reflect total populations of asbestos workers.'' Additional reservations were based on the frequent absence of data regarding J-'rom the Division of Thcr.uie Dimm-jo. Dctpaitimut of Medicine, and the Drpartnwnt of l'.ithch tcy, Mount Sinai llo^iicul. Bead lit inrc ;i iniut nuvtinj: of tin* stxli.ms- on radiology and diu-asrs of the chcit and tin* Atari ican Colleue of tllu*t L'hv m'ci.u'.S at the 112th Amntal Mi*ctim! of the American Mt dic.il AsMici.itimi, Atlantic Cit>, XJ, June IT, IfJGd. exposure, smoking habits, and priSPuM.. history, on the size of series, and on inadequate histological verification in some cases. Within the last few years a number of additional problems connected with asbestos exposure have appeared, making clarification and resolution of the foregoing statistical uncertainty a matter of con siderable concern. First, there has been greatly increased use of the various types of asbestos (a fi.yfrJi!litt^ of this group of minerals, from 500,000 tons to 2,500,000 tons per year in the last 30 years), as well as a greatly in creased number and varicjy^^j^dygdi'igltgpirjica- tioiiT^T^stie^PfriJdver^OGO such uses now re corded). Second, suspicion has been growing that malignancy associated with asbestos exposure may include neoplasms other than carcinoma of the lung. Thus, a significant ~rela 11onsiiiji" 1ills'"been claimed between diffuse mesothelioma of the pleura and peritoneum and "asbestos exposnreT' This communication is concerned with investi- gations undertaken to study the following factors: (1) the incidence of deaths due to pulmcmnrv car- Xr. .jAv cinoma among a group ot workeis exposed to as-' 1 hestos '"under United States industrial conditions in the past several decades. (2) whether or not such individuals would also be found to have an \ increased rijk.oLutlior neoplasms, and (3) whether such rcsksjyfaddJ^^pcACiHJ4L.4nJUC!Ui:U)' other than the asbestos-producing or ashesies'-producls 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 study of an industry with asbestos exposure of limited extent and intensity would throw some light on 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, members of New York Local 12 and Newark, NJ, Local 32 of the International Association of Heat and Frost Insu lators and Asbestos Workers. As the full title im plies, these men are insulation workers. Although the union is considered one of the building-trades unions, its members do insulation work in a va riety of industries, including shipbuilding. Called daggers" in Great Britain, they are often desig nated "pipu-UMWlCJ's," "insulators," or `jsi&stos workers" in this country. The union_is_one of the oldest in the country. PLAINTIFF'S EXHIBIT 42 ASARCO ALV 0007192 Vol 1S.8, No 1 ASBESTOS EXrOSUnE--SELIKOFF ET AL 23 Tlic New York local, as the "Salamander Associa tion of Boiler and Pipe Feltcrswas the first union of insulation workers in the United States. It amal gamated with other locals as the current Asbestos Workers Union in 1912. The stability of this union has been reflected in the stanilitv of its member ship rolls. "Once a pipecoverer, always a pipecoverer Tias been of epidemiological importance to us and has made this group of men particularly suit able for the study of long-term effects of asbes tos inhalation. Unlike unskilled workers exposed to asbestos inhalation in poorly paid industries, there is little labor turnover among insulation workers. Accurate employment records are main "7 tained by the union, which-has"* also"TSeen con Lf 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 1930's. By the end of 1942 the union rolls consisted mainly of men with consid erable. expedience, plus a few who joined Ju_.jil.40, 194_<andtw1942. Between 1946 and 1962 union membership increased substantially. Source of Data.--From union records, a list was prepared of every.individual who was a member of either of (lie metropolitan locals on Dec 31, ,,]912, 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; 890 men joined after 1942. Personal data were obtained from union records, and the w<jrkhisl{>ry of each man was detailed, including withdrawal frorn.emplgypient (war ser vice, other employment.jrctir'cmcnt. illness). These data gave, the baseline for calculation of the onset and duration of exposure. For members who 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 spccimens, and hos pital records were obtained and reviewed in those deaths, approximately`one half, in which the ter minal illness had occurred in a hospital. Statistical 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 hisgr}\ Our complete records cover all members ofthe union (including active and retired mem bers, both dead and alive) during the 20-vear period from Jan 1, 1943, through Dec 31, 1962. However, with few exceptions, the only men with a history of 20 years or longer since first exposure to asbestos were the 632 men on the union rolls as of Jan 1, 1943. (The exceptions were a few men who joined the union after Jan 1, 1943, but who had been employed previously as asbestos workers elsewhere.) Of these 632 men, 255 died before Jan 1,1963. Table 1.--j^ajvYears of Experience of 632 Asbestos Workers Exposed to Asbestos Dust 20 Years or Longer Years Age 35-39 ................ 40-44 ................ 45-49 ................ ..... 50-54 ................ 55-59 ................ ..... 60 64 ................ ..... 65-69 ................ 70-74 ................ 75-79 ................ 80-84 ................ 85+ .................. 1943* 1947 85.0 339.5 382.0 221.0 31.5 Totals ......... ..... 1,912.0 1948* 1952 185.0 486.5 324.0 364.0 390.0 341.5 181.0 125.5 70.0 18.5 2.0 2,478.0 1953* 1957 7.0 291.5 530.0 308.0 316.0 344.0 286.0 137.0 70.5 38.5 8.0 2,336.5 1958* 1962 11.0 70.0 314.5 502.5 268.5 255.0 280.0 297.5 75.0 23.5 13.5 2,011.0 Of these 632 men, 339 had been exposed to as bestos dust prior to 1924. In other words, as of Jan 1, 1943, 20 years or 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. T]y^Wjn!i^y}i.o.MCCt'CJlh'4t-cxposed'prior to_J.924 were counted _in,,years (or up to the time of death of those who died). The 293_.wJiO first,yxpps.cd..m.19-4 or later were counted only after they reached the 20-vears-since- first-exposure point (those whajlicd,.bcl}igrcl;'oppcd at thc._JJinevvof death). When the statistics were completed, we found that we had records covering a total of 8,737.5 man-years of experience of men with a history of 20 years or longer since first exposure to asbestos dust. Of the 8.737.5 man-years, 1912.0 were in the five- year period 1943-1947; 2.47S.0 were in the period 1948-1952; 2,336.5 were in the period 1953-1957; and 2,011.0 were in the period 1958-1962. Table 1 shows the age distribution of the man-years in each of these five-year periods. XabJe 2 shows (1) the a\'cra_ge ^.ageTipcciflc^jbcalli^^ates of all US white males during each of these periods, and (2) the average age-specific death rates from cancer of the lung, pleura, mediastinum, and trachea among US white, males during each period, as reported by the US National Office of Vital Statistics. The man-vcais were then multiplied lw the cor- respc)ndmg>j;cpprtccJr,J-A.,dcatp rates to ascertain the e.v/rcc/xrLjaunibtaufiLjdt'^ths under the null hypothesis that the death rates of asbestos workers do not differ from death rates of all US white males (both age and date being taken into consid eration). The. results are summarized in Table 3. Results Total Deaths.--During 1917) only 2S deaths occurred among the asbestos workers, whereas 39.7 deaths would have occurred had their age-specific death rates been the same as for all US white males during those years (Ta ble 3). In other words, at the start of the study, the asbestos workers had below ^average death rales. This'is "by"no mcans siirprising.Tildeed. such 143 ASARCO ALV 0007193 24 ASBESTOS EXI'OSUKE--SELIKOFF ET AL JAMA, April G, 1904 Table 2.--Total Deaths and Deaths From Cancer of the Lung, Bronchus, Pleura, Mediastinum, and Trachea per 10,000 White Males per Year* Aeo 35-39 ..... . .... 40-44 ........... 45-49 ........... 50-54 ______ 55-59 ______ .... 60 64 ........... 65-69 ........... 70-74 ______ 75-79 ............ 80-84 ______ 85+ ............. 1943-1947 Total 36 55 85 133 196 295 435 634 $77 1.453 2.422 Lung Cancerf 1 2 4 5 7 7 6 6 5 3 1948-1952 Total 30 48 78 124 189 281 417 605 915 1.353 2,162 Lung Cancerf 1 3 5 8 10 11 ii 10 8 7 1953-1957 Total 26 43 72 115 178 276 416 586 878 1.346 2,017 Lung Cancerf " 1 3 6 10 14 17 16 14 12 9 1958-1962 Total 25 42 70 116 178 272 418 607 866 1,363 2,148 Lung Cancerf' 1 i 3 7 11 17 21 21 17 15 11 'Death rates as reported annually by the US National Office of Vital Statistics. A five-year average is given here for each period. Average for 195S-1962 is a prcjccticn of J95S-1960. since 1961-195? rates arc not yet available. fDcnth rates include cancer of the luis, bronchus, pleura, mediastinum, and trachea, assigned to international list code No. 47bf prior to 1949 and to No. 160-164 thereafter. is almost always found in the first few years of a prospective epidemiological study of this type. The explanation is almost certainly as follows: The 632 men in this analysis were actively employed as as bestos workers in 1012. Since disability front illness or other causes precludes cmpJovment.jH'"a trade of tin's tj'pe, thi^e-xu^,At'cre..pj;e5umably_tvcll (or at least notjjisablod) 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 and ^sabledjienmnsjiaye extreme ly high death rates. A selective effect of this type gradually wcars^off with time and largely disap pears within fi\'e "to' CciTycars Tiom the time of in itial selection. During the second fiyQ-year .period (194S-1952) the death raJLg^jMhc, asbestos ^yorkeij^ was slight ly higher than the dcaSiTate^oTall US Cvliite males, ie, 54 observed deaths compared with 50.S ex pected deaths. In later periods, the death rate of the asbestos workej;s_ wasjirqporlion at clv higher. For the period 1933-1957, there vereTSo 'observed deaths compared with 56.6 expected deaths, and for the period 195S-1932, there were 88 observed deaths compared with only 54.4 expected deaths. Table 3.--Observed and Expected Number of Deaths Among 632 Asbestos Workers Exposed to Asbestos Dust 20 Years or Longer Gau^e of Death 19431947 Total, all wauscs ..................... .... . 26 "Observed (asbestos workers) Cxpected (US white males) .... 39.7 Total cancer, all sites.................. 13 ' Observed (asbestos workers) Expected (US white mak-s) .... 5.7 Cancer of lung and pleura ......... 6 Observed (asbestos workers) Expected (US while males)__ 0.8 Cancer of stomach, colon, and rectum .................................... Observed (asbestos workers) Expected (US white moles) ... 4 2.0 Canccc-of all other sites com* pined ...................................... Observ*d (asbestos workers) Expected (US white males) .... 3 2.9 Asbestosis ......... ............................ 0 Observed (asbestos workers) Years 1948- 19531952 1957 54 85 50.6 56.6 17 26 8.1 13.0 8 13 1.4 2.0 47 2.5 2.6 56 4.2 8.4 14 Total, 1953-' 19431952 19C2 88 255 54.4 203.5 39 95 9.7 36.5 18 45 2.4 6.6 14 2.3 29 9.4 7 21 5.0 20.5 7 12 Cancer of the Lung, Pleura, and Trachea--In each of the four fivc-vear periods, far more deaths from cancer of_jfj^^unguomul,^lwr^^p,ccinrcd among the asbestos workers than would have oc curred had their death rates from these diseases been the same as for all US while males (Table 3). Altogether 45 of the 632 asbestos workeis died of cancer of tl)cse**srtcsTT\Tieieas'miiv 6.6 such deaths would be expected from general US experience. Of these. 45 deaths, 42 were recorded as due to bronehogomTTSrfrnoffta and 3 to neoplasms of the pleura. The pleural neoplasms were all recorded as mesotheliomas. --~ Thus it was found that the death rate from can cer of the bronchus and pleura was C.S limes as ugh among these asbestos workers as m flic gen eral US white male population (both age and date 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 Qigaiplte^smokers,among them. We cannot an swer this questionMdii:gctly.,siiice.we have not yet been able to ascertain the smoking habits of the men who died. However, the following pieces of evidence indicate that unusual smoking habits can not account for the high death rate from lung can cer among these workers: Wc have interviewed 320 of the 377 surviving members of the 19-12 gibupTTabTe*7*gTves a sum mary of the smoking habits in this group compared with a sample of men drawn from the general population of _1.12_I^coilntji^__inJ2oj>tales.7 The un ion sample is somewhat inadequate since it does not include, the jnen who died and...clqcs_nqt in- elude-aJl_jif_tlip,,p}ej;ct,iii'i05. members of the union. Nevertheless, it shows that a substantial proportion of asbestos workers never smoked ciga rettes regularly. Certainly the 632 men in our analy sis of death rates were not all heavy cigarette smokers. In the general mjd^.ppp.yJ:Ujojy^tmg^canccr death .rales--are.. about.Acn^..tuncs..;is3igli among cigarette .smokers -as- among uousnipkers; and the MI ASARCO ALV 0007194 -i Vol 1SS, No 1 -A--S--B--E--S--T--O--S----E--X--P--O---S--U--R--E-------S--K--I-.-I-K---O--F--F----E--T----A--I-,, 25 * I Table 4.--Smoking Habits of 320 Abestos Workers Exposed to Asbestos Dust 20 Years or Longer u/ifit CamMin /->f KAon Frnm Hyp ftpnnrfll Pnniilatirm* i Never Smoked Regularly Smoked Pipe, Cigar, Never Cigarettes History of Cigarette Smoking Age 40-49 50-59 60-69 70+ Asbestos Workers, % 9.3 14.3 20.3 25.5 General Population. % 18.8 19.9 23.6 37.1 Asbestos Workers, % 4.6 6.1 10.1 11.8 General Population, % 7.5 9.9 16.2 23.9 Asbestos Workers, % 86.1 79.6 69.7 62.7 General Population, % 73.7 70.2 60.2 39.0 Sample cf men from general population as reported by Hammond and GarfcnKel.? death rate from lung cancer increases greatly with the amount of cigarette smoking.'1 However, a large proportion of all men in tlie United Stated have a history (TlegTiT;ff``cTgmet^-`*Mn<>kiiig. I'roin data in a prospective ."tuch^on^sn'ioking,e it may he esti mated that if all men smoked a pack or more of cigarettes a day (ie, if all the nonsmokers, cigar 13 smokers, pipe smokers, and light cigarette smok ers had, instead, been heavy cigarette smokers) the Vdlung-cancer death rate would he approximately 3.4 times as high as iHx^at this time. FTomTlmrvce may'eoncludc that even if till our asbestos worken>^li;u,i,,u)Qkcd a pacTT^or'moYe of cigarettes a day (and, indeed, from our sample we know they did not), and if exposure to asbestos were of _no,yignificancc..,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- cancer death ratt.yy)\iG,^,,Uij^asJjJs!' as that of white males in the general population. Gastrointestinal Cancer.--Rather to our surprise, the death rate from cancer of the stomach and the death rate h'cnr'S^iej^T^tTie^a^on^an^rectum were higher"^m5jng^.,tJie^,sisbcsto.5 ,, workers than would be expected from the rales reported for the US white male population, calculated in the same way as for lung caneerr'Twclve deaths from gastric cancer occurred nmdng tfie"asbcstos workers, ns compared with onlv 4.3 expected. Seventeen deaths from cancer of'tfie colon and rectiinT occurred among the asbestos workers, as compared with 5.2 expected. Cancer of All Other Sites.--The combined death rate from cancer of all sites other than lung and pleura, and stomach, colon, and rectum was not increased. Twenty-one such deaths occurred among asbestos workers, as compared with 20.5 expected. Asbestosis.--Of 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.S years, with a range of 32 to 59 years. Comment Carcinoma of the Lung.--The results with regard to carcinoma of the lung are clear. Industrial ex- --JMWllWO..!-.. --( t(. posurc to asbestos by insulation workers, as stud ied here, results in a marked increase in the inci dence of cancer ofthe lung, approximately six to seven, times the_expected incidence. Altogether, 45 (17.6^) of 255 men with more than 20 years elapsed smeethe onset of exposure died of cancer of the lung or pleura. These data dgjjpX.give the "iilild^Mfi-GLCAmcer of thg.Jurig.iiJ.i)Abcs,tosis." They relate to thej>pe- cific conditions of our investigation: to a group of men with only intermittent exposure,.tot<materials containing limited mnounls^foften 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, they relate to the relatively recent past, in a trade with the shorter work week oF the strong huiUlins trades unions, in an era when industry lias been aware of potential asbestos hazard and the working popu lation has had some consciousness of potential risk associated with dust exposure. These data would not necessarily apply to asbestos, exposure in other industries, sucITasTtie'facfoi'y production of asbestos products, the asbestos textile industry, etc, where conditions of employment might be quite different. Our results do not contradict the even higher incidence of lung cancer suggested in other studies '; they are merely a shade less strik ing. Diffuse Pleural and Peritoneal Malignancy-- Mesothelioma.--Determining, the incidence of dif fuse jdennd^nicsQ11)idioma is complicated by the insecurity"" of its histological 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.,fihrosmxxjmaof the pleura. It is difficult to evaluate completely the published re ports of diffuse pleural mesothelioma in asbestosis in the absence of complete details of each case. To the present lime, there has been no informa tion concerning the incidence of diffuse pleura! mesolhejjo.ma in asbestosis, since the published cases are reported without reference to a total pop ulation in which they occur. Nevertheless, the I'-r 145 ASARCO ALV 0007195 26 ASBESTOS EXPOSURF.-SELIKOEF ET AL JAMA, April fi, 1904 growing number of reports of individual cases suggests that these tumors are perhaps becoming relatively frequent complications of asbestos ex posure. Our observations in this series arc similarly sug gestive. In three of the 255 deaths among the men who had worEe?rTo?"20 VcTuTDr more, the exam ining pathologist considered the dealli due to dif fuse pleural mesothelioma, and in the two cases in which wcTllave been able to review the histological material, the histological appearance was that of ten so categorized, and asbestos bodies were pres ent. This incidence of more than 1% of deaths from pleural mesothelioma is stnkingK''Ingrrfor a tumor which is generally considered to be extreme ly rare. In one case in our series pathological ex amination suggested diffuse peritoneal mesotheli oma. Tin's single experience is too fragmentary for evaluation. Gastrointestinal Carcinoma.--Isolated instances of gastrointestinal carcinoma in the presence of asbestosis have been known, but there have been no data to indicate that these were more than coinci dental findings. Among the asbestos workers studied here, cancer of the stomach, colon, and rectum was throe times as frequent as expected. These data suggest that there may perhaps be an ctiologiealTcTafi6nsl`iii)''beTv.reei)')iidiisIinil asbestos exposure and earemoma ' of the gastrointestinal tract. Environmental Asbestos Exposure.--The recent demonstration, by South African * and British " in vestigators of pleural an^j?cn'toneal,,neoplasins among individuals who had chance environmental exposure to ast^^3TiHvj'y'S,before raises the very important question of possible widespread carcinogenic air pollution. The possibility of en vironmental exposure has long been known. Soon after the initial clarification of asbestosis as a clinic entity, lladdow'0 demonstrated asbestos bodies in a man not employed in the industry but living next door to an asbestos factory. This finding was later mirrored in the finding< of chmnic_benHitim dis ease among residents of a community near a berylh'iiijpfitctory.1'2W3 h4a5t *is7 iw, however, is an appre ciation of the potential extent of the problem. Thomson and asst>ciaTes`vrTlave 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, Kivilttolo found 4fff) cases of pleura] calcification of the type characteristically seen among asbestos workers, without obvious cause. In a comparable area without any asbestos mine, no cases were found among 7,101 persons x-rayed. It should be noted lliaPTIiese-.veiWnot people who worked in tlie mine--none cncl--but, rather, were farmers, housewives, and others who lived inTFuTgeneral location. In one subject who came to autopsy, polarized-light 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 that utilizes the material. The floating fibers do not respect job classifications. Thus, for ex ample, insulation workers^midqubledlv share their exposure with'Their'workmates in otTilr trades: intimate con IffclWeitTf `astiest os *i s possible for elec tricians, plumbers, sliect-mctal workers, stenmfitters, 1aboi"fsTTa;yfi3TiTeTsrkiuTI(TTvial:crs, and fore men; perhaps even the supervising architect should be included. 1 E 100th St, Xew York 10029 (Dr. Selikoff). This studs' was supported by the Health Research Coun cil of the City of New York. Cooperating in this investigation were the executive officeis of tlie International Association of Heat and Fio>: Insulators and Asbestos Woikcrs, Washington. DC, and the officers and membership of the New York and Xcw.uk, XJ, locals of this Union. 1. I.ynch, K.M., ami Smith, W.A.: Pulmonary Asbestosis: Carcinoma of Lung in Asbcsto-Silicosis, Anier J Cancer 24:50-01 (May) 1935. 2. Annual Report of Chief Inspector of Factories for Year 1035, London: Her Majesty's Stationoiy Office, 1950, emnd 0, p 206. 3. Doll, II.: Mortality From Lung Cancer in Asbestos Workers, Brit J Industr Mai 12:81-fid, 1955. 4. Rolilig, 11., and Jacob, C.: Neue Gesichtspunktc iiber den Lungc'.ikrebs dcr Ashestarbcitcr, Dcut.sch Med Wschr 81:231-233 (Feb 17) 1950. 5. Braun, D.C., and Tnian, T.D.: Epidemiological Study of Lung Cancer in Asbestos Miners. AMA Arch lndustr Health 17:G34-G53 (June) 195S. 0. Wagner, J.C.; Sleggs, C.A.; and Marehaiid, P.: Diffuse I'leural Mesothelioma and Asbestos Exposure in North Western Cape Province, Brit ] Iuihu.tr Med 17:260-271, 1900. 7. Hammond, E.C., and Caifinkel, L.: Smoking Habits of Men and Women, J Sul Cancer lint 27:419-112 (Aug) 1961. 8. Hammond, K.C., and Horn, D.: Smoking and Death Rates: Report on Forty-Four Months of Follow-up of 1S7,783 Men. I. Total Mortalitv; II. Death Rates bv Cause, JAMA 1CG:1159-1172 (March 8); 1294-1308 '.March 15) 1958. 9. McCaughcv, W.T.E.: Wade, O.L.; and Finns. P.C.: Exposure to Asbestos Dust and Diffuse Pleural Mesothelio mas, Brit Med J 2:1397 (Xnv 241 1902. 10. Haddow, A.C., in Report of Annual Meeting of British Medical Association, Manchester, 1929, Lancet 2:230-231 (Aug 3) 1929. 11. Chesncr, C.: Chronic Pulmonary Granulomatosis in Residents of Community Xear Beryllium Plant: Three Autopsied Cases, Am: Intern Med 32:1028-10 IS (June) 1930. 12. Thomson, J.C.; Kasclmla, R.O.C.; and MacDonald, R.R.: Asbestos as Modern Uiban Hazard, 8 Ajr Med J 37:77-81 (Jan 19) 1963. 13. Kiviluoto, R.: l'lcural Calcification as Roentgenologic Sign of Xon-Occupational Endemic Authophjlhtc-Axbestosis, Acta Badiol Suppl 194, pp 1-67, 1960. 146 ASARCO ALV 0007196