Document peeZ69Lz32vOjGw0G9roqn94j

183 l'P f Carcinogenicity of Amosite Asbestos Irving J. SeliUoH, MD; E. Cuyler nai.tmond, ScD; and Jacob Churg, MD, New York Few data exist concerning the comparative neoplastic potential in man of the several kinds of asbestos. In particular, there has been no evi dence concerning whether the amo3ite variety is carcinogenic. The matter is ol practical im portance, since amosite use in the United States has sharply increased. The mortality experience of a group of 230 men previously employed in an amosite asbestos factory was studied during the years 1960 through 1971. Total deaths were more than twice the number anticipated: 46.4 were expected, and 105 occurred. Some 14 deaths were due to asbestosis. Both lung cancer and mesothelioma were found in considerable ex cess. Two or three deaths from lung cancer were expected, and 25 occurred. There were five deaths from mesothelioma. Occupational exposure to amosite asbestos can be assoc._!ed with serious cancer hazard; its continued industrial use re quires rigorous control. Possible differences in the disease potential of the several common, commercially avail able varieties of asbestos fiber (chrysotile, amosite, crocidolite, anthophyllite) have been sought, since the use of asbestos might be guided accordingly.1 Experimental studies were undertaken to seek such information. These have not indicated any critical differ ences; mesothelioma can be produced easily by intrapleural inoculation of various types of asbestos.2 There is less information concern ing experimental lung cancer.3 Submitted for publication Feb 7, 1U72; accepted March 17. From the Mount Sinai School of Mt-diune, City University of New York, and the Amriican Cancer Society, New York. Kcprint tequesty to Depot Inient of ('omnuiuity Medicine, Mount Sinai S hool of Moduine, City University of New York, 1 iC(h Am* & lOOih St, New York, NY 1U02`J (Dr. Schkolt). Few data exist concerning the compara tive neoplastic potential of the several lands of asbestos in man. Some information is available for chrysotile,1 crocidolite,3 and anthophyllite.0 However, there has been no evidence to indicate whether or not the amo site variety is also carcinogenic. In large part this has been the result of epidemiological difficulties. Since there is often admixture of fiber varieties under in dustrial circumstances, the experiences of employed populations are not always readi ly attributable to a single fiber variety. Dili gent efforts have been made to investigate the occurrence of disease in the Transvaal in South Africa, the only area in which amo site is mined, and where populations ex posed only to amosite could be identified. Environmental studies in this area, reported in 1964, showed no instance of mesotheli oma in amosite miners and only isolated instances of carcinoma of the bronchus, al though asbestosis was found.7 This survey has since been complemented by a study of miners in the area. No attempt was made to study the Bantu workmen who are in the majority, since labor turnover is very high, and ". . . records kept are such that follow up of individuals over a period of time is impossible."5 The fate of white miners em ployed between 1954 and 1958 was investi gated. Unfortunately, the records turned out to be imperfect and incomplete, since the white work force in these mines was unsta ble. Only 147 white miners could be fol lowed at all, and only 20 of these were observed for more than 20 years after first exposure to asbestos. Among these 20, there was one instance of lung cancer and none of mesothelioma. Elsewhere, comment is made Arill i m,n llrnltli -- Vol 25, Sc/it 1072 I i i j i i! ST 0566532 ST65U 533 .c184 amosite ashestos ca\ci:i:--seukoee ft at that ``'I'ho position of amosile is not clear . . with only one pleural mesothelioma stated to he known in the Transvaal.11 Increasing Use of Amositc in (he US Whether or not amositc is carcinogenic is of some practical importance. Because this variety of asbestos has not been reported to cause cancer, there has been a tendency in Great Britian, for example, to substitute it for other kinds of asbestos, especially crocidolite. Moreover, increasing amounts of amositc have been sent to the United States from South Africa. There is no record of amositc being imported before 1930, and as late as 1940, only small amounts were re ceived. Since the Second World War. the situation has changed. Annual imports have risen from less than 500 tons in 1935 to 4,500 in 1945, 18,000 in 1955, and 21,400 tons in 1965 (Table 1). The US Department of Commerce has reported imports of amosite and crocidolite into the United States (in tons per vean as follows; 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 Total Amosite and Crocidolite ............................................................ ............................................................ 1,907 823 oi o ................................................... ............................................................ ............................................................ ......................... ............................................................ ............................................................ ............................................................ 233 152 501 1,432 2,928 3,282 6.129 These data should be considered with appreciation of the long-lapsed period be tween onset of asbestos exposure and ap pearance of asbestos cancer--usually 20 to 30 years or more.,,> Cancers that may be associated with the amosite now being im ported will not become clinically evident until the 1990s or after the year 2000. Current Investigation Wc have investigated the mortality experi ence of a group of workmen occupationally exposed solely to amosite whose employment startl'd between dune 1911 and December 1915. Tins cohort has been observed through June 30, 1971. Employed Population.--Nine hundred thirfy- three mm were employed for varying periods of time m an asbestos products factory in an e.i-iein <ilv of (lie United States, starting work some lime between June 1941, when the facto ry began production, and December 1915. The plant continued production until November 1971, when it closed its doors. It manufactured amosite asbestos insulation, primarily for use in shipbuilding and ship repair. Wo have sought to trace each of these men .and have successfully done so in 868 instances so far (9375). In 65 instances, tracing is still incomplete. Data concerning date of birth, on set of employment, duration of employment, and tvpc of work are known. for the purpose of this report, we hn\e investigated the mortality experience of those nuln iduals who had at least one year of em ployment There were 333 such men who began work sometime between 1941 and 1915: 88 died by Dee 31, 1959: 15 were lost to follow-up; and 230 were alive on Jan 1, 1960, and each of these men has been followed since. Table 2 provides an analysis of man-years of experience for these 230 men. by age category. We have calculated expected death rates for these men in the Jan 1, 1960 through June 30. 1971 category, using age, year, and sex specific rates for US white men. Expected deaths were then compared with those observed. Amosite Exposure.--No information is avail able concerning dust levels in this plant. Al though exhaust ventilation was used, discus sions with surviving workmen and plant man agement indicate that dust exposure, at least in some circumstances, could have been high. Res pirators were issued to the work force hut were inconsistently used. We have ascertained that only amosite asbes tos was used in this factory in several ways: 1. Review with plant management indicated that only this fiber variety was purchased and utilizer!. This is consistent with the ship insu lation specifications under which the products were made. 2. We have obtained samples of the products made; examination of these samples by polar ized light microscopy, electron microscopy, electron diffraction, and electron microprobe analysis showed only amosite to be present. 3. Asbestos was still present in the factory building's storeroom. When retrieved and ex amined, the material was found to be amosite. by employment of the same analytical methods. 4. Several workmen had kept their own res pirators, dating hack to their period of em ploy-men'. The filters in these respirators were studied. Fibers retained on the filters were Arch Environ Health--Vol 25. Sept 1972 AMOSITE ASBESTOS & CANCER--SELIKOFF ET AL Table 1.--Estimated US Asbestos Fiber Consumption (Tons) Year 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 Crocidolit. No data No data 8,700 8.500 11,700 19.600 17.100 1,907* 501* 8,068* Amosita No data No data 4,500 5,400 18.000 19.500 21,400 Canadian Chrysolite 152,000 200.700 198,200 154.200 225,900 355.800 687,400 699,100 605.800 661,100 Other 4.000 4,100 8.500 20,500 36.300 9,000 27.400 21,600 24,600 20.100 Total 156.000 204.800 208.407 175.201 270,268 378.000 72 8.700 740.400 669,580 719.700 Amosite and crocidotite combined; not separately recorded. 185 Table 2 ---Man-Years of Experience Among 230 Amosite Factory Workers (1/1/60--6/30/71) Age Under 40 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85 + Total Jan 1, 1960 Through Dec 31, 1964 471.7 528.8 501.9 415.2 347.3 285.2 198.4 ; 04 .. S9 7 3S 0 g.r> 3088.2 Jan 1, 1965 Through June 30, 1971 54.8 438.3 619.5 565.2 472.2 352.4 272.9 163.9 134.1 47.0 25.0 3145.3 1990iS Table 3.--Causes of Death Among 230 Amosite Asbestos Factory Workers (1/1/60--6/30/71)* Cause of Death Total cancer, all sites Cancer of lung, pleura, bronchus, trachea Lung cancer Observed Deaths 43 27 25 Expected Deathsf 8.5 2.4 t Pleural mesothelioma Peritoneal mesothelioma Cancer of stomach, colon, rectum 25 3` 5 1.6 Cancer of all other sites 8 4.5 Asbestosis Alt other causes 14 l 48 37.9 Total deaths 105 46.4 Analysis of lifetime work experience indicates that, lor Inrue maiority. ths was only occu pational asbestos exposure. ( Expected de.iths I9L0 1904 >irc i isrd on UL> spculic rales tor white men in 19G2. For I960 1971. rates for I'ff.H were utilized. Smokim* h jhits ore disri.-p,<if dcd. J US data not avail.ji,U- i.hi Ii, urc should tie mil/ shidilly less than 2.4. i US dato not jvaiUhli. t>ut Hu s' .ire r ire (.nti^cs ot death in ucnur.il population. /t/i7i /.nrif'itt ifiti/fh -l u( 'J>, Sc{>( I'JfJ I 1 4 >I i i i I ;> ST 0566535 -T '9 / n< 186 AMOSITE ASIIESTOS X- CA.XCl.li -SFI.IKOFF FT AL removed nnrl analyzed They were invariably amosite. 5 We have extrneted minora! fillers from I In' lungs of individuals in 11 is cohort who had died. Large numbers of fillers wore present Electron difTrnrtinn and clrctron mioroprnlio analysis showed them lo he amositc.11 except for the occasional chrysolite fibril expected to he present in the lungs of urban dwellers in (his area.1-'2 3 4 5 * Results The mortality experience of this group of workmen, 1960 through 1971, demonstrates that a serious health hazard was associated with this industrial use of amosite. Table 3 records expected and observed deaths. Total deaths were more than twice the number anticipated: 46.4 were expected and 105 occurred. This excess death rate was limited to two categories: cancers of various sites and asbestosis. Fourteen deaths were due to asbestosis, when virtually none was expected. That amo'-ite can result in asbestosis has been previously recognized.7 In physiological studies of a select group of workmen at this particular factory from 1954, serious pul monary insufficiency had been demon strated.''1 Roth lung cancer and mesothelioma were also found in considerable excess. It was anticipated Ih.at 2.4 deaths from lung cancer would eventuate; 25 occurred. The calcula tion of expected rates disregarded smoking habits, since the smoking habits of individu als not examined by as are not accurately known. In prosjxx:tivc studies from this point on, smoking habits will be taken into account.'1 Mesothelioma caused five deaths: two pleural and three peritoneal. Each has been histologically verified in material obtained during operations in two instances and at autopsies in three. In one case, there had hern prior chrysotile exposure; in four, only amosite asbestos exposure had occurred. Parenthetically, additional iastances of meso thelioma have occurred among.men working in this plant, other than in the cohort re ported here. It may lie of interest that more deaths from cancer of the stomach, colon, and rec tum have occurred than expected The in crease is only threefold, however. As with similar previous experiences, further obser vations are required before this association can be regarded rs clearly established.1' This investigation has been supported in part hv research grant ES 00358 of the National Institute of Environmental Health Sciences, US Depaitment of Health, Education. and Welfare. Field investigations were earned out by Doco'.hv Perron, Shirley Levine, Rayla Margolies, and Charles V. Nolan. References 1. Whipple HF fed): Biological effects of asbes tos. Arm NY Acrid Sci 132:700-721, 1905. 2. Wagner JC, Berry G: Mesotheliomas in rats following inoculation with asbestos. Brit J Cancer 23:567-581, 1960 3. Smith WF., Miller I,, Churg J: An experimen tal model for study of co-carcinogenesis in the respiratory tract. Oak Ridge, Tenn, Atomic Energy Commission symposium scries 21, 1970, pp 299-316. 4. McDonald .TC, McDonald AD, Gibbs GW, et al: Mortality in the chrysotile asbestos mines and mills of Quebec. Arch Environ Health 22:677-086, 1971. 5. Wagner JC, Sleggs CA, Marchand P: Diffuse plcuial mesothelioma and asbestos exposure in the North Western Cape l'rovinrc Brit J Induslr lifed 17 2< 0-271, 1960. 6 Kiviluoto R, Miicrmnn L: Results of asbestos exposure in Finland, in Shapiro HA fed): Proceed ings of Internalnmnt ('onirrenee an Pneumoconiosis, lohanneshurp lith*). Capetown, South Africa, Oxford Crmorsitv Press, Inc, ]070. pp 190-191. 7 S|ms Hcnier CK Asbestosis in South Africa: t '< rt iin gi n'p ajihica1 and enx ironmcntal considera tion. Arm NY Arad Sci 1.(2 215-234, 1965. 8. Sluis-Cremer GK: Asbestosis in South Africar asbestos miners. Environ Res 3:310-319, 1970. 9. Wagner JC: Asbestos cancers, editorial. J No Cancer Inst 4G:v-ix, 1971. 10. SelikofT I.J, Bader RA, Bader MF,, et ai Asbestosis and neoplasia, editorial. Amer J 7f 42:487-196. 1967. 11. I-anger AM, Rubin I, SelikofT IJ: Electior microprobe analysis of asbestos bodies, in Shupirr HA fed): Proceedings of Internationa! Conference on Pneumoconiosis, Johannesburg 1969. Capetown South Africa, Oxford University Press, Inc. 1970, pi 57-69. 12. Longer AM. SelikofJ IJ, Snstre A: Chrvsolili asbestos in the lungs of persons in New Yok Citx Arch Environ Health 22:348-361, 1971. 13. Bader ME. Bader RA, Selikoff I T: Pulmonnrx function in asbestosis of the lung: An ah eolaremit lory block syndrome. Amer J Med 60 235 212, l:`5t 14. SelikofT l.T, Hammond EC, Churg .1. Ashcxtn exposure, smoking, and neoplasia. JAMA 30! 106 112.1903 15. Selikoff 1.1, Churg .1, Hammond F.C. A-ho-tn exposure and neoplasia. J \MA lc3 22-26. ItV-i Arch Environ Health--Vol 25, Sept 1072 s 531 rC^N & u a <y 0 >1 i s4zJ r--t n3 0) co H > Ccd -C ai-i < ASBESTOSIS to 0 4tOJ 0) X5 w to < Q >1 * 4-> *H CO u~0 U-t E0 < .* H Q 4*4 fH 0 0) CO * > 4J O' in M o 3 0 x: H cr CJ Cc 0) r~4 A O' > 0 0 in u cM r4 *-3 u uV <0 u >c CQ rtf