Document BKE0wav5b86NpZ4ZBeadBxVo

Asbestos-associated Disease in United States Shipyards Irving J. Selikoff, M.D. and E. Cuyler Hammond, Sc.D. CLINICAL LATENCY OF ASBESTOS-ASSOCIATED CANCER During the past 15 years the important disease potential of asbestos exposure has been clarified. The principal hazards have been demonstrated to be cancer of a num ber of sites, and asbestosis. Among asbes tos workers, approximately 20 percent of all deaths are due to lung cancer, six per cent or seven percent to pleural and/or peritoneal mesothelioma, and there is an excess found in several other categories (e.g., cancer of the esophagus, stomach, colon-rectum, oropharynx, larynx, kid ney). Table 1 provides an analysis of causes of death among 17,800 asbestos insula tion workers in the United States and Canada followed prospectively from January 1, 1967 to January 1, 1977. Risk of asbestos-associated disease has also been observed in workers in other trades where asbestos exposure occurs -- Dr. Selikoff is Professor of Medicine, and Director, Environmental Sciences Laboratory, Mount Sinai School of Medicine, City Univer sity of New York, New York, New York. Dr. Hammond is Vice President, Epidemiology and Statistics, American Cancer Society, Inc., New York, New York. This is a special report from the Environmental Cancer Research Project, American Cancer Society and the Environmental Sciences Lab oratory of the Mount Sinai School of Medicine of the City University of New York. for example, where individuals simply working near "asbestos workers" are ex posed to the same dusts. Risk extends even to individuals not employed in an asbes tos-contaminated environment; mesothe lioma has been found among family con tacts of asbestos workers residing in the same households, as well as among people living within a quarter of a mile or so of asbestos plants or other facilities which have used asbestos-containing materials. Although mesothelioma is not neces sarily the most common disease resulting from asbestos exposure, it provides a very useful index of such problems, since it is only uncommonly seen as a result of ex posure to other agents or without iden tified cause. Large scale investigations of series of cases of mesothelioma in France, Great Britain, the Netherlands13 and else where have demonstrated that the large majority of these cases can be traced to prior asbestos exposure. For these neoplasms, as for all can cers due to asbestos exposure (and, in deed, for extensive asbestosis as well), a rather uniform characteristic has been found: the disease usually does not be come clinically evident for 15, 25, 35 or more years from onset of asbestos ex posure. The initial decades are periods of grace with no illness or disability. While some -early X-ray changes may be seen after five to 15 years, they are limited in extent and not usually accompanied by significant symptoms. They merely dem- VOL. 28, NO. 2 MARCH/APRIL 1978 87 LAM 019117 DPMC-12740 TABLE 1 Deaths among 17,800 asbestos insulation workers in the United States and Canada January 1,1967-January 1, 1977 Number of men Man-years of observation 17,800 166,855 Expected* Observed Total deaths, all causes Total cancer, all sites Lung cancer Pleural mesothelioma Peritoneal mesothelioma Cancer of esophagus Cancer of stomach Cancer of colon-rectum All other cancer Asbestosis All other causes 1,660.96 319.90 105.97 7.01 14.23 37.86 154.83 1,351.06 2,270 994 485 66 109 18 22 59 235 162 1,114 *Expected deaths are based upon white male age specific mortality data of the U.S. National Center for Health Statistics for 1967-1975 and extrapolation to 1976. These ara rare causes of death in the general population. The membership of the International Association of Heat and Frost Insulators and Asbestos Workers, AF L-CIO, CLC, was enrolled on January 1, 1967, and has been observed since. onstrate that enough asbestos exposure has occurred to produce such changes. In this sense, they are harbingers of future risk of clinical disease. Tables 2-5 illustrate the characteristic latency of asbestos disease. In one group of 1,117 asbestos insulation workers in the New York metropolitan area, most of 725 workers with less than 20 years from on set of exposure (Table 2) had normal Xrays. When changes were present, they were minimal in extent. On the other hand, after the 20-year point, most X-rays were found to be abnormal, frequently exten sively so.4 Tables 3-5 show that few meso theliomas and little excess cancer of the lung occurred less than 20 years from on set. Most occurred 30 or more years from onset of exposure. A young man may be gin work at the age of 18; his risk of as bestos-associated cancer does not become substantial until he is 40, 50 or older. EARLY STUDIES: MESOTHELIOMA IN SHIPYARDS In 1968, the first warning that asbestos se CA-A CANCER JOURNAL FOR CLINICIANS LAM 019118 DPMC-12741 Onset of exposure (yrs.) 40+ 30-39 20-29 10-19 0-9 TABI E 2 X-ray changes in asbestos insulation workers4 Asbestosis (grade) %% No. Normal Abnormal 1 23 121 5.8 194 12.9 77 27.2 379 55.9 346 89.6 94.2 87.1 72.8 44.1 10.4 35 51 28 102 49 18 35 17 4 158 9 0 , 36 0 0 Total 1.117 51.5 48.5 366 126 50 disease might be a serious problem in shipyards was sounded by Harries sin Great Britain and Stumphius6in the Neth erlands when they reported instances of mesothelioma among shipyard workers. What was worrisome was that the men were not "asbestos workers" but rather, individuals employed in other trades. At the Devonport shipyard of the Royal Navy, for example, mesothelioma in a boilermaker, a fitter, a shipwright, a weld er and a laborer were described. This raised the important question of whether asbestos use in shipyards might result in the exposure of the workers em ployed in many trades, to dust derived from the few "asbestos workers" in their midst. In 1943, in the United States, for example, approximately one in 500 ship yard workers was an insulator. The other 499 included welders, shipfuters, machin ists, pipefitters, electricians, boilermakers and painters (Table 6). The significance of this question is made apparent by the fact that during World War II, approximately 4,500,000 men and women worked in our shipyards, many of them under conditions in which exposure to asbestos was possible. After World War II the total number of shipyard workers rapidly decreased from a high of 1,700,000 in the last months of 1943 to 200,000 or so. During the period of 1946-1976, total employment remained in this range, fluctuating with economic conditions and the country's shipbuilding program. The 200,000-250,000 figure characterized the total number in the yards at one time; however, there was much turnover, and the total number of different individuals was much larger. There are no accurate data readily avail able which could tell us how many differ ent people--carpenters, riggers, electri cians, draftsmen, welders, etc.--were so employed. Nevertheless, the early obser vations (soon augmented by later stud ies78) pointed to a potentially serious problem. Harries has recently published his fur ther observations at Devonport, through 1973.9 By the end of the year, he had ob served 55 cases of mesothelioma in that shipyard alone. Again, trades other than "asbestos workers" gave evidence of the hazard. Only two of the 55 worked directly with asbestos (lagger, sprayer). The other 53 included 14 shipwrights, nine boiler makers, eight fitters and eight electricians (Table 7). John Edge of High Carley Hospital has published similar data from shipyards in Barrow (Table 8)10; his most recent observations are particularly disturbing.11 In Barrow, 429 individuals were seen, be- VOL. 28, NO 2 MARCH/APRIL 1978 89 LAM 019119 DPMC-12742 TABLE 3 Deaths among 17,800 asbestos insulation workers in the United States and Canada January 1, 1967-January 1,1977: Analysis by duration from onset of employment Total men Man-years of observation 12,683 89,466 12,051 77,389 Before 20 years from onset 20 or more years from onset Expected* Observed Expected* Observed Total deaths, all causes 283.93 324 1,377.01 1,946 Cancer, all sites 42.65 83 277.25 911 Lung cancer Pleural mesothelioma Peritoneal mesothelioma Cancer of esophagus Cancer of stomach Cancer of colon-rectum 12.03 ** ** 0.66 1.56 4.07 36 2 3 1 1 4 93.94 * 6.35 12.67 33.79 449 64 106 17 21 55 Asbestosis ** 8- 154 * Expected deaths ere based upon white male age specific mortality data of the U.S. National Center for Health Statistics for 1967-1975 and extrapolation to 1976. * `These are rare causes of death in the general population. tween 1964 and 1971, with radiologically evident pleural plaques; these plaques were considered to signal prior shipyard employment. Controls were 429 men from a neighboring city (Carlisle), matched for age and date ofX-ray; they had no plaques on their roentgenograms. Both groups were observed through 1976, i.e., for a minimum of five years. Among the 429 men with pleural plaques, there were 127 deaths; those with no plaques suffered 74 deaths. The excess was primarily in two categories, lung cancer and mesothelioma. There were 19 deaths from lung cancer and 23 from mesothelioma among the former shipyard workers. As for the con trols, four died of lung cancer and none died of mesothelioma. Findings of an extraordinary increase of mesothelioma were also reported last year from the French shipyard area in Western Brittany. Lajartre et al. analyzed cases of pleural mesothelioma in Nantes. In the period 1957-63, there were two cases; from 1964-1970 there were 12; and from 1971-1974 there were 24.12 This was interpreted as consistent with the mark edly increased shipbuilding program dur ing and after World War II, and with its attendant risk of asbestos exposure. 90 CA-A CANCER JOURNAL FOR CLINICIANS LAM 019120 DPMC-1274 TABLE 4 Deaths among 17,800 asbestos insulation workers in the United States and Canada, Jan. 1,1967-Jan 1,1977: Analysis by duration from onset of employment Duration Num from ber onset of (years) men Personyears of observation Lung cancer Expected* Observed Pleural mesothelioma No./I 000 person-years Peritoneal mesothelioma No./IOOO person-years <10 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45+ 5,552 9,063 9,948 8,887 6,596 3,547 2,019 1,108 1,030 26,393 29,003 34,069 31,269 20,657 11,598 5,401 3,160 5,305 0.69 2.77 8.57 17.03 21.04 18.48 11.47 8.12 17.82 0 7 29 59 104 112 66 39 69 0 0 0.06 0.19 0.73 0.86 2.96 1.27 2.45 0 0 0.09 0.10 0.87 1.90 3.33 5.06 5.47 Expected deaths are based upon white mate age specific mortality data of the U.S. National Center for Health Statistics for 1967-1975 and extrapolation to 1976: Smoking habits not taken into account. ASBESTOS DISEASE IN U.S. SHIPYARDS There has been comparatively little writ ten concerning the potential for asbestosdisease hazards in U.S. shipyards. In part, this may have been due to the fact that in the latter part of World War II a survey directed to this question failed to demon strate the prevalence of significant asbes tos disease. At that time, 1,074 insulation workers employed in U.S. yards were examined and, with few exceptions, no evidence of disease was found. ^Unfortu nately, the significance of the fact that the very large majority of men had begun working only a short time before was not appreciated; neither was it understood that X-ray evidence of disease could not be expected to appear until one or two de cades later. During the 1960's, evidence accumu lated that "asbestos workers" (insulation) employed in shipyards had unhappy dis ease experience, with markedly increased death rates of cancer (lung cancer, pleural mesothelioma, peritoneal mesothelioma, gastrointestinal cancer) and asbestosis. These observations, however, were con fined to insulation workers, and while they pointed to a possible accompanying difficulty among other shipyard trades, expecially in view of British experience, detailed observations concerning other workers were not available. The potential for asbestos disease in U.S. shipyards was further highlighted by accumulating knowledge that the workers who manufactured the asbestos insulation materials used in U.S. yards during and after World War II were themselves found to suffer serious asbestos disease. Investi gations of the employees at one such plant showed markedly increased risk of neo plastic disease and asbestosis, including increased risk of death of cancer with as little as one month of employment. 's.ie VOL. 28. NO. 2 MARCH/APRIL 1978 91 LAM 019121 DPMC-12744 Fig. 1 S.P.4J.M. Extensive bilateral pleural calcification in former shipyard workers. Asympto matic. No part of pleura is immunecostal; diaphragmatic, mediastinal, pericardial. Bilateral calcifi cation of this sort rarely seen except with prior asbestos exposure. Even wives and children of the employed workers showed evidence of asbestos dis ease, indicating that exposure of lesser intensity might be seriously hazardous as well.17 RECENT SURVEY OF SHIPYARD WORKERS, GROTON, CONNECTICUT Cases of asbestos-associated disease among workers employed in a shipyard in Groton, in 1974-1975, were brought to our attention. Against the background of what was already known concerning the poten tial for asbestos disease in shipyards, it appeared useful to obtain information concerning whether there was the likeli hood of a high incidence of such disease or whether the cases seen were isolated, random exceptions. Lung cancer, mesothelioma, extensive asbestosis and other serious complications of asbestos exposure are late findings. Limited X-ray change (parenchymal, with- in the lung, or pleural) often precede these serious consequences. While such changes may occur to an extent visible by X-ray without subsequent cancer or disabling asbestosis, their appearance among a group of workers provides evidence of prior significant asbestos exposure. Ab sence of such X-ray changes is no guar antee that important asbestos exposure has not occurred. Many workers may have had asbestos exposure sufficient to cause death from mesothelioma, for example, without showing X-ray change. Neverthe less, taken as a whole, absence of X-ray change in a group of workers suspected of having been exposed to asbestos provides some evidence that the exposure was lim ited. On the other hand, the presence of characteristic asbestotic X-ray abnormal ities is prima facie evidence that, overall, there was important asbestos exposure in the group. In light of this, we sought to ascertain whether there was significant prevalence of asbestotic X-ray abnormalities among Groton shipyard workers. Examinations 92 CA-A CANCER JOURNAL FOR CLINICIANS LAM 019122 DPMC-12745 Fig. 2 J.B. Both fibrotic plaques and pleural calcification in x-ray ot former shipyard worker. Asymptomatic. Their presence is merely evi dence of prior asbeslos exposure and not in dicative that mesothelioma will necessarily follow. Fig. 3 J.W. Age 49, 1975. Truck driver until 1960, when he became "pipe coverer" in a ship yard. X-ray, fifteen years later, shows reticular (irregular) opacities of moderate profusion (2/2 in the ILO U/C Classification). Some shortness of breath on exertion. Note: infiltrate in lower lung fields, upper lobes clear. This is common. were largely limited to those whose em ployment had begun 15 or more years be fore; all were volunteers. A caveat is in order: there is no way of knowing, under these circumstances, whether those who volunteered were necessarily represen tative of the entire work force, or even of their specific employment category. Al together, 1,000 men were examined, in cluding 157 boilermakers, 121 pipefitters, 73 insulators, 82 painters, 69 carpenters, 117 welders, 104 electricians, 108 outside machinists, as well as laborers, molders, lead bonders, office workers, draftsmen, guards, and decontamination technicians. Films were categorized using the Inter national Classification of Radiographs of Pneumoconioses (I LOU/C) (Appendix 1). Overall, approximately half of the workers examined showed X-ray evidence of pulmonary and pleural changes of the sort regularly seen following direct or in direct occupational exposure to asbestos (pulmonary asbestosis, pleural asbestosis). The findings are outlined in Tables 9 and 10. One or another abnormality was present in 274 of 636 workers with less than 20 years from onset of exposure (43.1 percent) and among 185 of 364 shipyard workers 20 or more years from onset (50.8 percent). Parenchymal disease was seen in 29.6 percent of the former group and 36.8 percent of the latter. Pleural changes were found in 23.1 percent of the less experi enced workers and in 29.7 percent of the men with longer experience. The high prevalence of pleural changes was not un expected, having been found previously among shipyard workers in Britain and elsewhere.18 The importance of duration from on set of exposure is clearly seen in Table 10, where it is found that among 303 workers who began work only in 1961 or later, 115 (38.0 percent) had abnormalities on X-ray. In contrast, among 166 workers whose employment began in 1950 or before, 85 (51.2 percent) were abnormal. No trade was immune to changes. Tables 11 and 12 indicate that this was as true for painters as it was for electricians, for carpenters as for machinists, and for VOL. 28, NO. 2 MARCH/APRIL 1978 93 LAM 019123 DPMC-12746 -n TABLE 5 Deaths among 17,800 asbestos insulation workers in the United States and Canada, Jan. 1,1967-Jan. 1,1977: Analysis by duration from onset of employment Years from onset of employment <10 10-14 15-20 20-24 25-29 30-34 35-39 40-44 45+ Total deaths 51 85 188 320 388 340 253 203 442 Lung cancer 0 8.24 15.43 18.44 26.80 32.94 26.09 19.21 15.61 Percent of all deaths Mesothelioma Pleural Peritoneal 0 0 1.06 1.88 3.86 2.94 6.32 1.97 2.94 0 0 1.60 0.94 4.64 6.47 7.11 7.88 6.56 Total 0 0 2.60 2.82 8.40 9.41 13.43 9.85 9.50 Total 2270 21.37 2.90 4.80 7.70 boilermakers as for welders. Review of work practices makes this quite under standable, of course. The conditions of shipyard work have been such that it is likely that asbestos exposure would have occurred among all individuals at a work site where the material was being installed, repaired or removed. Data are less certain for the less common crafts, where fewer workers were examined. Although evi dence of asbestotic changes was found among some of these men and women as well, one can estimate a proportion only with less assurance. Thus, exposure to asbestos under past conditions, of an intensity sufficient to cause significant asbestotic X-ray change, was common at the shipyard in Groton. As a result, a large number of workers now have pulmonary changes associated with such exposure. The prevalence of such a high proportion of asbestotic X-ray changes raises the question of increased risk of asbestos-associated neoplasms in the future. Those to be considered include cancer of the lung, pleural mesothelioma, peritoneal mesothelioma, and esophageal, stomach, colorectal, oropharyngeal, la ryngeal and renal cancer. The extent of this risk is not now known. CURRENT SITUATION In terms of public health, the overwhelm ing problem is the undoing, ameliorating or modifying of both current and antici pated results of past mistakes. The prob lems are straightforward and, simulta neously, complex. To a considerable de gree, the complexity derives from the fact that we have had little experience to guide us in such matters, especially on the scale found in the present situation. The following recommendations -- 94 CA-A CANCER JOURNAL FOR CLINICIANS LAM 019124 DPMC-12747 necessarily incomplete and tentative--are offered: 1. Knowledge concerning asbestos expo sure: Dissemination of information: under standing the disease potential of asbes tos exposure (past and future) would be valuable for both worker and manage ment. Avoidance of additional exposure: appropriate engineering and industrial hygiene methods are crucial; removal or repair of asbestos materials now in place presents a problem for the future. 2. Medical surveillance programs: Asbestosis: awareness of the presence of this disease by both the patient and the treating physician would be im portant, since most deaths of asbestosis are due to intercurrent respiratory in fections, rather than to progressive pul monary fibrosis. Pulmonary infections can be well treated, and experience has shown that many lives can be saved. Lung cancer: early diagnosis can in crease the likelihood of successful treat ment to some extent (by no means as much as we would like). It is not known whether more energetic surveillance (as with frequent sputum cytology examin ation) will increase the percentage of those successfully treated. Studies are now in progress to investigate this pos sibility. Colorectal cancer: early diagnosis in creases the likelihood of cure. Oropharyngeal, laryngeal or renal car cinoma: awareness of the increased risk of these cancers improves chances for early study and diagnosis of the pres ence of these conditions, which can be cured in many cases. Pleural and/or peritoneal mesothelio ma: effective therapy is not now avail able and early diagnosis does not sig nificantly increase the likelihood of survival. However, research concerning therapy is now underway in the United States, Great Britain and France, and it may be hoped that improved treatment methods will become available. Education programs: Smoking: lung cancer risk is greatly TABLE 6 Percentage distribution of trades in private shipyards, June 1943 Trade Welders Shipfitters Machinists Pipefitters Electricians Carpenters Laborers Burners Painters Sheetmetal workers Riggers Chippers and caulkers Boilermakers Crane operators Percentage 15.3 11.0 8.1 7.2 6.6 6.1 5.5 3.8 3.1 3.0 2.8 2.8 2.3 1.3 Pipe coverers AM other 0.2 21.1 Source: Bureau of Labor Statistics. Bulletin 824 multiplied by asbestos exposure.19 It is urgent that this information become available to workers who have been ex posed to asbestos, and that every assis tance be afforded them to help in their efforts to control and eliminate smok ing, especially cigarette smoking. Some data are also available suggesting that cessation of smoking will, after a num ber of years, reduce the risk of lung cancer, even with a history of prior cig arette smoking. Should these experi ences be confirmed, it will be even more urgent to identify and alert former ship yard workers, to acquaint them with theimportant risk of lung cancer should they continue cigarette smoking. Cigar ette smoking also increases the risk of serious disability associated with pul monary fibrosis, and of the develop- VOL. 28. NO. 2 MARCH/APRIL 1978 LAM 019125 DPMC-12748 TABLE 7 Mesothelioma tumors in Devonport Dockyard, England, 1964-1973* Asbestosis (disability) No. % 16 10.3 36 23.1 15 9.6 4 2.6 15 9.6 11 7.1 6 3.8 5 3.2 48 30.8 156 Occupation Sprayers Laggers Shipwrights Boilermakers Engine fitters Electricians Caul kers*R iveters Welders All others Mesothelioma (deaths) No. % 1 1.8 1 1.8 14 25.5 9 16.4 8 14.5 5 9.1 3 5.5 3 5.5 11 20.0 55 Harries, P.G., Envlr. Res. V : 261-267, 1976. TABLE 9 X-ray abnormalities among workers employed in shipbuilding and ship repair TYPE OF ABNORMALITY Less than 20 years from onset of shipyard em ployment (636) 20 or more years from onset of shipyard em ployment (364) Total Number % Number % Number % Any abnormality All parenchyma Parenchyma only Parenchyma & pleura All pleura Pleura only 274 188 127 61 147 86 43.1 29.6 20.0 9.6 23.1 13.5 185 134 77 57 108 51 50.8 36.8 21.1 15.7 29.7 14.0 459 322 204 118 255 137 45.9 32.2 20.4 11.8 25.5 13.7 96 CA-A CANCER JOURNAL FOR CLINICIANS LAM 019126 DPHC-12749 TmBLE 8 Mortality experience of 429 shipyard workers in Barrow, England with pleural plaques on x-ray (1964-1971) compared with control men in Carlisle, without pleural plaques Tracing to December 31, 1976 Alive Dead Not traced Causes of death Lung cancer Mesothelioma G. 1. cancer All other cancer Ischemic heart disease Chronic bronchitis All other causes Plaques 299 127 ( 30%) 3 (0.7%) 429 Plaques 19 23 7 13 34 9 22 Controls 347 74 (17.2%) 8 ( 1.9%) 429 Controls 4 0 4 7 29 9 21 TABLE 10 X-Ray abnormalities among workers employed in shipbuilding and ship repair: analysis by duration from onset of work NORMAL ABNORMAL Onset of work < 1950 1951-1955 1956-1960 > 1961 Total 166 198 333 303 1000 No. % 81 48.8 98 49.5 174 52.2 188 62.0 541 54.1 No. % 85 51.2 100 50.5 159 47.8 115 38.0 459 45.9 VOL. 28, NO. 2 MARCH/APRIL 1978 97 LAM 019127 DPMC-12750 TABLE 11 X-Ray abnormalities among shipyard workers employed in shipbuilding and ship repair: major crafts CATEGORY All crafts Painters Machinists (outside) Pipefitters Insulators Electricians Boilermakers Welders Carpenters Years from onset of shipyard work AH groups 20 or more years Abnormal Abnormal Number Number % Number % 1000 459 45.9 185 50.8 82 44 53.7 10/25 40.0 108 58 53.7 12/32 37.5 121 66 54.5 25/34 73.6 73 38 52.0 2/7 28.6 104 55 52.9 23/34 67.8 157 80 51.0 41/84 48.8 117 42 35.9 25/48 52.1 69 38 55.1 12/33 36.4 831 Total 1000 459 45.9 185/364 50.8 ment of cancer of the esophagus. Again, educational programs would be ofvalue. information is required for proper clin ical surveillance. 3.Assessment of the potential for ship yard asbestos disease: Household contact asbestos disease: while families of asbestos workers are at risk, it is not known whether ship yard workers tended to contaminate their homes with appreciable amounts of asbestos in the past, and whether this has resulted in disease risk. Such Necessary additional data: appropriate studies of mortality experience, status of retired workers and effects of mini mal exposure are required for complete evaluation of the potential for future shipyard asbestos disease. Nevertheless, enough is now known to warrant rapid development of effective medical sur veillance programs. Further research can proceed apace. 98 CA-A CANCER JOURNAL FOR CLINICIANS LAM 019128 DPMC-1275 r> TABLE 12 X-Ray abnormalities among workers employed in shipbuilding and ship repair: less common crafts Heavy equipment operators Laborers Inside machinists Mofders Lead bonders Decontamination technicians Guards w/o previous job in yard Office workers -- Draftsmen w/o previous job in yard No. 13 7 30 12 21 12 12 37 Abnormal 8/13 1/7 15/30 4/12 7/21 5/12 3/12 16/37 % 62 14 50 33 33 42 25 43 References 1. Bientz, M.; DiMenza, L.; Nebut, M., and Bignon, J.: Registre des mesotheliomes matins de la pleure el du peritoine. Premiere resultats. Nouvelle PresseMed. 6:3114,1977. 2. Greenberg, M., and Davies, T.A.L.: Meso thelioma Register 1967-68. Brit. J. Indust. Med. 31:91-104,1974. 3. Zielhuis, R.L.; Versteeb, J.P.J., and Plantejdt, H.T.: Pleural mesothelioma and exposure to asbestos, lnt. Arch. Occup. Envir. Health 36:1-18,1975. 4. Selikoff, I.J.; Churg, J., and Hammond, E.C.: The occurrence of asbestosis among in sulation workers in the United States. Ann. N. Y. Acad. Sci. 132:139-155, 1965. 5. Harries, P.G.: Asbestosis hazards in naval dockyards. Ann. Occup. Hyg. 11:135-145,1968. 6. Stumphius, J.: Epidemiology of mesothe lioma on Walcheren Island. Brit. J. Indust. Med. 28:59-66,1971. 7. McEwen, J.; Finlayson, A.; Mair, A., and Gibson, A.M.M.: Asbestos and mesothelioma in Scotland. Int. Arch. Arbeitsmed. 28:301-311, 1971. 8. Fletcher, D.E.: A mortality study of ship yard workers with pleural plaques. Brit. J. Indust. Med. 29:142-145,1972. 9. Harries, P.G.: Experience with asbestos disease and its control in Great Britain's Naval dockyards. Envir. Res. 11:261-267,1976. 10. Edge, J.R.: Asbestos-related disease in Barrow-in-Furness. Envir. Res. 11:244-247, 1976. 11. Edge, J.R.: Personal communication, December 16,1977. 12. Lajartre, M., et al.: Mesotheliomes pleuraux diffus et amiante. Ouest Med. 29:615-621, 1976. 13. Fletcher, W.E.; Viles, F.J., Jr.; Gade, R.L., and Drinker, P.: A health survey of pipe covering operations in constructing naval ves sels. J. lnd. Hyg. Toxicol. 28:9-16,1946. 14. Selikoff, I.J.: Disease prevention in as bestos insulation work. Int. Symp. on Safety and Health in Shipbuilding and Ship Repairing, Helsinki, Finland, 1971. Occupational Safety and Health Series #27, ILO, Geneva, 1972. 15. Selikoff, I.J.; Hammond, E.C., and Churg, J.: Carcinogenicity of amositeasbestos. Arch. Env. Health 25:183-186,1972. 16. Seidman, H.; Lilis, R., and Selikoff, I.J.: Short-term asbestos exposure and cancer risk. Proc. Third Inti. Symp. Detect. Prev. Cancer, 1977. 17. Anderson, H.A., et al.: Household-contact asbestos neoplastic risk. Ann. N.Y. Acad. Sci. 271:311-323,1976. 18. Sheers, G., and Templeton, A.R.: Effects of asbestos in dockyard workers. Brit. Med. J. 3:574-579,1968. 19. Selikoff, I.J.; Hammond, E.C., and Churg, J.: Asbestos exposure, smoking and neoplasia. JAMA 204:106-112,1968. VOL 28. NO. 2 MARCH/APRIL 1978 99 LAM 019129 DPMC-12752