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4 1S0-1SG EUMOCONIOSI Proceedings of the International Conference Johannesburg 1969 EDITED BY H. A. SHAPIRO Ph.D., M.3., Ch.B., ?.R.S.S.Af. Visits Profsasor of Foraasic Modiciae University of Natal, Durban CAPE TOWN OXFORD UNIVERSITY PRESS LONDON NEW YORK TORONTO - I97O - .. .*> - * : * * ri vm.m / MORTALITY EXPERIENCES OF ASBESTOS INSULATION WORKERS 1943 " 196S* Irving J. Shutoff, E. Cuylfr Hammond end Jacob Chcrg Environmental Sciences Laboratory, .Mount Sinai School oj Medicine and the Department of Epidemiology and Biostatistics, American Cancer Society On December 31, 1942, there were 632 members of the Asbestos Workers Union in the New York area (New York and Newark, New Jersey locals of the International Associa tion of He3t and Frost Insulators and Asbestos Workers, I.A.H.F.I.A.W.). From January 1, 1943, to December 31, 1962, another 890 men Joined the union. We have followed each of these 1,522 men prospectively to the present. Four hundred and four died by December 31, j 968. Analyses of these deaths demonstrate that serious risks have been associated with work in this trade. own observations and those of others'-1 indicate that lends practices are essrt'u'.ly un.to.-m ;nrou;.a the country, the data which follow rrjy be taken to represent mortality experience in this trade tor the United States and Canada; direct srudy of all United States union insulation worker death;, 1967-196S, supports this.4 Exposure: There is scattered information re corded concerning variation in insulation materials used in the United States, iS70-io69'-it would appear that some materials (rs, hair-felt, cork, mineral wool) have sharply decreased while others (as, fibrous glass, plastics) have increased.1 Table I lists material currently used. Table t: Insulation Matzri.vls (U.S.)-i9691 1. Minerals Containing Asbestos Product Blankets................................ Moulded.......................... Insulation block .... Finishing 'cements' Sprayed asbestos Asbestos Content IOO%-2mosire 95%-amosite (5% filler) () 85% magnesia: 10-15% emosite 4- chrysonic () 85% cal. silicate: to-15% inosite (c) 85% cal. silicate: 10-15); amesite 4- chrysotile (rf) 85% calcined diarerraceeus silica 10-15; anosite 4 chrysotile (e) 85% calcium silicate: 10-15% chrysotile () 100% chrysotile () 50% chrysotile, 50% cement 10-15% asbestos-variable 3. Fibrous Class andlor Mineral VPool Block, rolls, prefabricates, high temperature insulation, finishing cements, mineral wool and cement. 3. Plasties . Polystyrenes sod polyurethanes: prefabricated, posvdered and foamed in place. 4. Other Cork, glass flakes, adhesives (epoxy and solvents; asphalt base and solvent, whea: pan:, silicones, magnesia, Portland cement). Matf.ruls and Methods The procedures followed in this study have been described.1': riricP.y, these men install insulaLon in the construction and (to n limited extent) in the shipbuilding industries. Approximately to of Uniied States union invuljpun wo,-Iters are in the New York-New Jersey locals and since our Tlw quiniltv of aahestos used anr.uellv in ir.suintinn m.iierials h.n not chi need srry rrjrli in tnr p--.' fifiv yeirs -- ic,;oo tons in 19:0 ,mj i6.aco 1;`1 m lbb.S 11 ible a).* There are currvncls', how ever, more insulation workers than previou-Is; prr- ' This siudv was supported bv toe llrjltli P.es.arth Council of the City of New Yurk. I So X / Mortality Experiences of Asbestos Insulation Workers 1943- J968 surr.ably, less asbestos pe: workman is now the case. Asb.-uos exposure varies by type of instal lation (Table j); about 40"., of an insulation Table 2: Asscstos Used in Insulation Materials in tke U.S., 19:3-1965 Tear IOCO 1925 193 1935 1940 194J 1953 1955 19*0 1955 Short To 12,303 19,200 16,600 7,400 13,600 14,800 12,700 12,200 13,000 16,100 OBSERVATIONS 632 Members of the Union on Decemeer 31, 1942 Three hundred and eighty of these men were dead _v December 31, 196S. Age, year and sex specific expected death rates were avail able to mid-1967;'"11 observed rates by cause are compared in Table 5. All deaths to December 31, 196S are tabulated in Table 6, by cause. Table 5: Expected and Observed Deaths Among 632 NY-NJ Insulation Workers, January i, 1943 to April 30,1967* Expected'* Observed Taele 3: Use of Asbestos Insolation Varia tion av CONSTRU CTI ON TYPE, I9&9 Contraction Fibro:ts G.'sss Asbestos Othtr Commercial (Schools, factories) .... Tower rrc-ccsi (Power plants, boiler rooms) Marine ... . 75 20 20 10 15 60 20 70 10 worker's time is sr-r.: in work using asbestos mate rials (Table 4). Table 4: Us: of Asbestos by Insolation Workmen IN THE U.S., 1569 Materia! Asbestos . . . Fibrous glass. . Other . . . Volunu % of Total 35 45 20 Application % of Time 43 40 17 Exposure of insulation workers in the United States cannot necessarily be equated with that of similar workmen in other countries. For one thin;, besides variations in working conditions, the type of fiber nr.J materials used may be different. Until 19AO, chrysot-ie was almost the only asbestos used, amosite ina':in;a its appearance later and croeidolite practically not at all (see brlosv). Second, spraying ot insulation has not been, until recently, widely used in thia countrv, in contrast to some other areas and, in so iar as titis cttccts exposure, would not be reliedcd in our m.ortjlity obstrv.i'ions. Finally, because of union juri-.uiep.unal agreements, the men we hive studied are restricted to insula tion cttiinst temperature change: acoustical insula tion and fireproofing arc the work of men in ot her trades and variables peculiar to such work would not be demonstrated by our data. All causes.......................... Lung Cancer .... G.I. Cancer .... Pleural Mesothelioma . Peritoneal .Mesothelioma All other Neoplasms . . Asbestosis.......................... 25T-0 S-9 11-2 +* 2J-0 349 66 37 6 14 21 27 * Of workmen reaching 20 years from first exposure. In addition seven men died before reaching this point. * Based on United States Mortality data.1- > United States data not available, but these are rare causes of death in general popuiation. Table 6: Causes of 3S0 Consecutive Deaths Among 632 Insulation Workers, January i, 1943 - to Decemser 31, 196S Before 20 Years from First Exposure After 20 Yearsfrom First Exposure Lung cancer .... Pleural Mesothelioma . . Peritoneal Mesothelioma . Gastrointestinal Cancer . Oropharvnv Larynx Cancer Cancer of Pancreas . . . All other Neoplasms . . Asbestosis.......................... All other causes. . . . 0 7* 06 0 16 0 37 z5 03 0 ` 19 0 30 6 1S5 7 373 LUNG CANCER One in five deaths.was caused by lung cancer. Despite the recent rise in p--ninence of meso thelioma, this remains ti.. most important asbestos-associated nei'pla Ft among insula tion workers. It is of inter.-sr, therefore, that there appears to be a special relationship to 1 i 1 1 \ .- i- .; 1 \ i iSa I. J. Selikotf, E. Cuyler HjmmonJ and J. Chur^ TaBLB 7; PLrVR-U. AND PrRITONFAJL MiSOTHFLJOMA AMONG NYC ASOTSTOS INSULATION VToRXXRJ,* January i, 1943 to Decimbfr 31, 1968 . Nnn&er Age at Onset (Years) Mean.................................................... Median............................................. S.D.......................................................... Range.................................................... Age at Death {Years) Mean.................................................... Median............................................. S.D......................................................... Kar.ge .................................................... Lapted Pi nod {Years) Mean.................................................... Median.............................................. S.D.......................................................... Range.................................................... Mesotheliama Pleural 6 Peritoneal 16 Bronchogenic Carcinoma 72 Ashettcsit 3 *5'21 5-4 17-45 20-0 >9 4-3 16-30 =5-4 25 6-36 16-54 24 24 * 5 5' 6 14-36 $6-o 55 2-4 54-60 62 >7 60 JO-2 JO-83 ' 63-8 64 7-=5 39-83 66-7 66 8-02 53-79 34-8 34-5 2-3 32-38 43 0 40-5 i8*9 32-61 38-7 39 = 3-5 22-60 42-8 44 7-69 30-59 In addition, we have observed 2 peritoneal mesotheliomas found at autopsy, in men who had died of broncho genic carcinoma. cigarette smoking among asbestos insulation workers10 (see below). Overall lung cancer death rates were' seven times expected.* MESOTHELIOMA :Twenty-tsvo of the 380 deaths were due to mesothelioma,--pleural and 16 peritoneal. Two occurred -943-1954; 20, 1955-1968; average lapsed Viod f"om onset of exposure was longer a . average age at death was greater for peritoneal than for pleural meso thelioma. Peritoneal mesothelioma does not seem to be related to cigarette smoking--we have seen 4 such cases in men who never smoked cigarettes. In the 3 cases of pleural meso thelioma for which we personally recorded smoking histories, all had smoked cigarettes. The preponderance of peritoneal meso thelioma among our cases, as in the series of Enticknap and Smither/1 is not necessarily contradictory to the observations of Wagner,i: Hourihane11 and others in which pleural neoplasms were largely seen. If may, rather, reflect the derivation of the cases--consecu tive scries with regular occupational exposure on the on: hand, against random cases, many with nor.-cccupational environmental cx- Thcre are, in addi'ian, three men found to have lung cancer during our survey, and who are now alive followin' therapy. posurc, on the other. It may be that in those people who develop mesothelioma in associa tion with asbestos exposure, the siic of the mesothelioma tends to vary to some extent with the intimacy 2nd duration of exposure-- pleural with lesser exposure and peritoneal with greater. GASTROINTESTINAL CANCER As in our first observations/ we have con tinued to see more deaths due to cancer of the stomach and colon than expected. However, the ratio is only 3 times expected and, with so few deaths, we are not yet certain of the relationship. " CANCER OF PANCREAS; OROPHARYNGEAL CANCER The same insecurity noted with gastro intestinal cancer is associated with these as well. We are, however, concerned that the incidence of both of these neoplasms will be increased among asbestos workers. As a practical measure, we now inspect the oral cavity during all clinical examinations of asbestos workers; one cancer of the lip has been discovered and successfully excised. It is of interest rear 2 of the 3 recent deaths of tongue cancer, 'v/cre in men who never smoked cigarettes. 182 I. J. Svli';olT, E. CuyW Hammond and J. Chung TaDLB 7: PlIXTRAL AND riRITONt.U. MESOTHELIOMA AMONG NYC ASBTSTOS INSULATION 'K'OFOURS,* January t, 1943 to Decemsfr 31, 1968 . Ni/w/f Age at Onset ( Years) Mean.................................................... Median............................................. S.D.......................................................... Range.................................................... Age at Death (Years) Mean.................................................... Median............................................. S.D.......................................................... Range .................................................... Lapsed Period {Years) Mean.................................................... Median.............................................. S.D.......................................................... Range.................................................... A '.tsothelioma Pleural 6 Ptritental 16 Bronchogenic Careinuma 72 Ashestosis 30 25 : 21 5-4 n-25 20-0 19 4-3 16-30 =5-4 25 6-36 16-54 24 24-5 5-6 14-36 56'O 55 2-4 54-o 62-7 60 10-2 SO-83 63-8 64 7-25 39-83 667 66 802 53-79 34-8 3 45 2-3 32-38 430 40-5 iS 9 32-6r 38-7 39 = 3-5 22-60 42-8 44 769 30-59 Jo addition, we have observed 2 peritoneal mesotheliomas found at autopsy, in men who had died of broncho- geaic carcinoma. . " cigarette smoking among asbestos insulation workers1' (see below). Overall lung cancer death rates were' seven times expected.* MESOTHELIOMA ; Twenty-two of the 380 deaths were due to mesothelioma, JL. pleural and 16 peritoneal. Two occurred : 943-1954; 20, 1955-1968; average lapsed viod from onset of exposure was longer a everagt age at death was greater for pen.oaeal than for pleural meso thelioma. Peritoneal mesothelioma does not seem to be related to cigarette smoking--we have seen 4 such cases in men who never smoked cigarettes. In the 3 cases of pleural meso thelioma for which we personally recorded smoking histories, all had smoked cigarettes. The preponderance of peritoneal meso thelioma among our casts, as in the series of Enticknap and Smither," is not necessarily contradictory to the observations of Wagner,'5 Hourihane'; and others in which pleural neoplasms were largely seen. It may, rather, reflect the derivation of the cases--consecu tive series with regular occupational exposure on the one band, against random cases, many with nor.-cccupational environmental ex- Thcre arc, in addition, three men found to have lung cancer during our survey, s.nd who are now alive following therapy. posure, on the other. It may be that in those people who develop mesothelioma in associa tion with asbestos exposure, the site of the mesothelioma tends to vary to some extent with the intimacy and duration of exposure-- pleural with lesser exposure and peritoneal with greater. GASTROINTESTINAL CANCER As in our first observations,1 we have con tinued to see more deaths due to cancer of the stomach and colon than expected. However, the ratio is only 3 times expected and, with so few deaths, xve are not yet certain of the relationship. ' CANCER OF PANCREAS; OROPHARYNGEAL CANCER The same insecurity noted with gastro intestinal cancer is associated with these as well. ^Te are, however, concerned that the incidence of both of these neoplasms will be increased among asbestos workers. As a practical measure, we now inspect the oral cavity during all clinical examinations of asbestos workers; one cancer of the lip has been discovered and successfully excised. It is of interest that 2 of the 3 recent deaths of tongue cancer, Avcre in men who never smoked cigarettes. 1" **v.*v*r T> l:y E-r<fl,r" *' f Ast'*'kl0J Insulation Workers 1943-19S8 8 3 ASEESTOMS Thirty deaths of the respiratory insufficiency jSo were due to with cor pulmonale. 890 MEN ENTERING UNION AFTER DECEMBER 3t, I942 ' Fifty-four of those men had prior insulation work experience before entering this union in 1943 or later; S36 did not. By and large, therefore, the men in this group are younger and would not be expected to have yet achieved a lapsed period from onset of exposure sufficient to have brought them to a period of serious risk of neophstic death. This theoretical consideration has so far been, con firmed by our experience (Table E). cancer among asbestos insulation workers." On January 1, 1963, there were 370 men still alive of our original 632 cohort (all now with long-lapsed periods from onset of exposure and very much at risk). Eighty-seven never smoked cigarettes: one died of lung cancer by December 7:, 196S. Two hundred and eighty three hac a history of cigarette smoking --27 have died of lung cancer (Tabic 9). Ta3le 9: Cicarette Smoking and Luxe Cancer in Ascestcs Insulation VPokxetls. Experience of 370 Min Followed Prospectively January i, 1963 to December 31, 1968 A'o History of Cigarette Smoking History of Cigarette Smoking Tabes 8: Onsst cf Exposure and Deaths of Neoplasm among 890 Min Who Joined Insulation VPorxirs* Union, 1943-1962 Year Onset ef Asbestos Insulation Number Exposure 1 ^19:9 . . . 2 1930-1942 3 *943-1947 4 'ti-1952 . 5 .3-1957 6 ;3-i952 . 8 46 164 250 iS5 236 r S90 Deaths 1943-1968 Total Neoplasm 3 3 22 .9 4 50 5O 00 24 8 Number of men . . . Expect edlun; cancer deaths to 4.30.67 .... Observed deaths 104.30.67 Observed deaths to 12.31.68 Total cases to 12.31.68 . . 87 O-lS 0 I X 283 1 98 24 27 30* *3 men still alive (all cigarette smokers). Computations suggest that an asbestos worker who smokes cigarettes has 90 tim;s the risk of dying of lung cancer compared with a naan who neither works with asbestos nor smokes cigarettes. 1: CA Lung (31), CA Lunc f. Leukemia (31). 2: CA Luo? (31), Pancrearitis. ,, 3: CA Lung (21), Asbesto' Peptic Ulcer, CA Pancreas (20), CA Tones. a), CA Colon (17), Pulm. embolism, Cirrhosis, Coronary. 4: Acciilcnt, Coronary, Cong. Heart Failure, Coronary, Coronary. j: Pneumonia, Rheumatic H.D., Coronary, Cir rhosis, S.5.E. 6: ( ) -- years from onset of exposure. MULTIPLE NEOPLASMS We have seen several instances of more than on; primary neoplasm in the same individual lung-lung; lung-larynx, etc.). These have been too infrequent to warrant more than arief recording except perhaps for two men vho died of bronchogenic carcinoma and ere found, at autopsy, to also have peritoneal atsorhelioma. EFFECTS OF CIGARETTE SMORtNG "here appears to be an important influence of garotte smoking on the incidence of lung AGE AT ONSET OF EXPOSURE Table 10 records the mortality experience of the 632 men, by age category at onset of exposure. FIBER VARIETY AND MESOTHELIOMA; EVIDENCE FROM PRESENT OBSERVATIONS Crocidolite seemed initially to be unique among asbestos varieties in having a special relationship to mesotheliomas. It has been considered desirable to obtain further evidence on this 'question, by study of populations exposed to other fiber varieties.11-'1 It may be useful, therefore, to evaluate the experiences of N.Y.-N.J. insulation workers in this regard. CROCIDOLITE EXPOSURE OF INSULATION WORKERS IN THE UNITED STATES There is no crocidolite mined in the United States: all must be imported either from South Africa, Bolivia or Australia. It has been possible, by review of import data, to accurately calculate crocidolite use. >S4 I. J. Se'.isfT, E. Cuyler Hammond and J. Churt Tabus io: Moxtaeity Experience or 631 NYC Khoatjox \To\usJ, By Act at Oxset of Exposum Cancer of Lun^ . . Pleural Mesothelioma . Peritoneal Mesothelioma GaurcL-itcstmal Cancer All ocher neoplasms . Asbestoses .... All other causes . . Deceased 15.31.68 Alive lz.31.63 Total Aje ct Ontet rf E*f*nurt 230 :i-30 30+ 14 (5*7%) .1}C5*3M 13 U'9li) 6 n u-jri) 45 101 5* (I7'3*i) ]}C3-7M 17 (5*7%) 15 IS 9= 199 6 (71%) ?}(=%> 8 (9 4%) 7 4 (4-7.i) 54 So US 10a 5 34 30: ss Total 73 16 37 rS 30 191 3so 333 632 Yrar 1920 1935 1930 1935 1940 1945 1950 1955 i960 1955 Tabus 11: Estimates U.S. Asbestos Fiber Consumption CrocidoUtt No data No dara 8,700 8,500 11,700 19,600 17.: _ i97 501 8,063 Arrotire No dara No data 4.500 5.400 18,000 19,500 21,400 Canadian Chrysotile 152,000 200,700 193,200 154,200 225,900 355.300 687,400 699,100 605,800 661,100 . Other 4.000 4.100 8,500 20,500 36,300 9.000 27.400 n,6oo 24,600 20,100 Total 156,000 204,Soo 208,407 175,301 270,268 378,000 738,700 740,400 669,580 719.700 Total Amositt and Crocidolite * 1930 1931 193* 1933 1934 1935 1936 1937 1938 1939 Source: U.S 1.907 . 823 . 212 233 152 501 1.432 . 2,938 . 3,282 . 6,1=9 panmerr of Commerce. Very little crocidolite catered this country until World War II (Table 11). Asbestos used here was almost entirely chrysotile. The largest asbestos manufacturer in the United States first used crocidolite in 1929 (for sheet packing, not insulation). This company never used crocidolite for the manufacture of insulation at any time (1929-196S), employing it only in two product lines (asbestos cement pipe, and packings;.'* These data arc consis tent with an analysis of insulation materials used in past decades on the United States west coast, where only chrysotile and amosite were found.1 During these same years, 19:0-1940, more than 267.000 tons of chrysotile were used for insulation purposes. This is not to say that it can be proven that crociaoiiic was never used before 1930 for insulation in the United States. Rather, if any was so utilized, it could only have been in very small amounts. Therefore, crocidolite exposure of United State*, nsulation workers before 1930 and probably oefore 1940 is un likely to have occurred *o any significant  ...jrtjliry Experiences of Asbestos InueUtion Workers I943-I96S iS3 extent and. as seen in Tabic i, is still a very minor affair. MESOTHELIOMA AMONG UNITED STATES INSULATION WORKERS The firs: mesothelioma reported in which occupational asbestos exposure was described, occurred in an insulation worker, a member of the I.A.H.F.I.A.W., in I946.ir It is not known whether cases occurred before then, but they have been noted since.15 Wc have seen zz cases, 1947-190S, in our group of men. as detailed above. Every one l:as occurred .in an insulation worker who begen work bejore 1930 (Table 12). The mean lapsed period from onset of exposure to death of mesotheliomas among the S36 men in our study who began work in 1943 or later (Table 8). These considerations' are relevant only to conditions in the United States, among insula tion workmen They do not disprove a special role for croct-olite elsewhere, in other circum stances. They should, however, engender caution in r..' ing on other asbestos varieties always to be significantly less likely to cause mesothelioma. The relative mesothelioma hazard for each fiber variety is still to be denned in humans. At this time our data suggest that it would be prudent to regard all fiber varieties as potentially hazardous, and to utilize appropriate industrial hygiene measures for all. Table 12: Lapsed Period from Onsct or Exposure to Death of ca Casts of Mesothelioma, 1947-1968, Among 63a Insulation Workers Followed Prospectively from January i, 1943 Patient T. A.C. . z. A.M. . * AS. . T.D. . F.C. . T.C. . E.M. . 8. F.S. . 9- 10. M.H. . 11. 12. H D. . 13- W.N. . 14. A.C. . 15 J.D. . 16. J LaG. . 17. J.O'C. . 13. G.V, . 19. H.C . 20. JIP. . 21. R.B. . 22. rf.T. . .- Site Pleural Pleural Pleural Pleural riaural Pleural Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Peritoneal Year Onset Em^lay*mnt 1022 1923 1929 1929 1927 1928 1910 1923 1924 1918 190s 192s 1919 191s 1924 1929 1917 1924 1929 1929 1907 1929 Year of Death 947 19*6 1961 1963 1964 1956 1949 1956 1956 1959 1963 1963 1964 1964 1965 1965 1966 . 1957 1967 1968 1968 196S Ase at Death 60 53 54 54 53 55 6l 5 52 60 86 66 63 6S 58 53 79 59 57 58 83 56 Years from One1 25 33 32 34 37 38 39 33 32 At 58 33 45 46 4t 36 49 43 38 39 6x 39 was 34.8 years for pleura] mesothelioma and 43.0 years for peritoneal. As detailed, crocidolite exposure of United States insulation workers, to the extent that it occurred, could not have been very exten sive be.ore 1940. Therefore, if a long lapsed period is required for asbestos-induced metotheliorna, crocidolite exposure alone cannot easily explain the mesotheliomas seen among insulation workers in the United States. Of course, it may be that crucidolitc's virulence makes for shorter lapsed periods between onset of exposure and death. Hut if ,us is so, it is difficult to explain the absence References 1. SelikofT, I. J., Churs, J. and Hammond, E. C. (1964): J. Amer. Med. Assoc., IRS. 22. - 2. Selikoff, I. J., Chur?, J. and Hammond, E. C. (1965): Ann. N.Y. AcaJ. Sc., 132, 130. 3. Fleischer, W. E., Vites, F. J., Gadc, R. L. and Drinker, P. (1946): J. Ir.dust. 1 lyg., 28, 9. . 4. Keane, VC. T. and Zavon, M. R. (1966): Arch. Envir. Health, 13, I7f. 5. Cooper, W. C. (196S): /merrier. Con/. ZJio/. bfjccts Asbestos. Dresden. 6. Selikoff. 1. J., Hammond, E. C. and Chur", J. (1969): Unpublished data. 7. Atarr. \V. T. (1964): Amtr. '.Just. Hys. Assoc. J., 25. 264. i XJSIiyvaitw*>iuua iS$ I. J. Selikoff, E. Cuylcr Hammond and J. Churg S. Pundsack, F. L. (1969): Personal communi cation. 9. Jobe, J. B. (19S9): Personal communication, jo. Seliko5, I. J., Hammond, E. C. and Churg, J. (196s): J. Amer. Med. Assoc., 204. 106. Tt. Fnticknap, J. B. and Smither, W. J. (1964): Brit. J. Indust. Med., 21. 20. 12. VCapner, J. C., Sleeps, C. A. and Marchand, P. (1560): Brit. J. Indust. Med, 17, 260. 13. Hourihane, D. 0`B. (1955): Ann. N.Y. Acad. Sc, 132, 647. rj. VC'agner, J. C (>963): Ann. N.Y. Acad. Sc, 132. 691. lj. Gilson, J. C. (1965): Ann. N.Y. Acad. Sc, 132, 696. 16. Pundsack, F. L. (196S): Personal communi cation. 17. Case Records of the Massachusetts General Hospital. '1947): Case No. 33m. New Eng. J. Med, :JS. 407. 18. Selikoff, I. J, Churg, J. and Hammond, E. C (19SJ): New Eng. J. Med, 132, 696.