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Reprinted from: BIOLOGICAL EFFECTS OF MINERAL FIBRES. Voi.2 J.C. WAGNER Lyon. UARCSaetutpc Publication* No 301 1980 ASBESTOSIS AMONG MAINTENANCE WORKERS IN THE CHEMICAL INDUSTRY AND IN OIL REFINERY WORKERS R. LTLIS, S. DAUM, H. ANDERSCN, G. ANDREWS & I.J. SELIKCFF Environmental Sciences Laboratory, Department of Community Medicine, Mount Sinai School of Medicine of the City University of flew York, New York, NY, USA INTRODUCTION Clinical field examinations of several large groups of workers in various plants of the chemical Industry - three vinyl chloride polymeri zation plants (Lills et al., 1975, 1976), a styrene polymerization plant (Lorimer et al., 1976), a titanium dioxide manufacturing plant (Daum et al., 1977) and a dye manufacturing plant - undertaken by the Environ mental Sciences Laboratory in the last few years, have called our attention to the occurrence of chest X-ray abnormalities (small irregular opacities and/or pleural changes) of the type known to be induced by dust exposure. Chest X-rays were read without knowledge of age, past medical history, occupational history or findings on physical examina tion. Yet when parenchymal changes (Irregular or rounded opacities) and/or pleural changes (chickening or calcification) were found, expo sure to asbestos, silica or coal dust had usually occurred. When examining workers from chemical plants, special efforts were made to include maintenance personnel, since it is well known chat their work implies a risk from significant overexposure to toxic substances, expecially when repair becomes urgently necessary. POPULATION AND METHODS To obtain information concerning the potential dimensions of asbestos hazards among workers in the chemical industry, a cross-sectional investigation of maintenance workers of a large chemical plant in New Jersey was undertaken. -795- 002243 18-0000823 796 LIUS ET AL. All were volunteers, end represented about half the men in mainten ance categories in the plant (welders, carpenters, electricians, pipe fitters, etc.}* Efforts were made to include as many as possible of* those with terms of employment of more chan 10 years, and to examine only a sample of employees with shorter durations of exposure; 26Z of those Examined had less than 10 years, and 592 had more than 20 years from onset of exposure (Tables 1 A 2). Table 1. Age distribution of 185 maintenance workers in a chemical plant Age (yrs) 20 - 29.9 No. X 27 15 30 - 39.9 --No. * --to -- 18 10 40 - 49.9 No. % -- -- 34 18 50 - 59.9 No. X 85 46 60+ No. Xmm 21 n Table 2. Duration since onset of first asbestos exposure (yrs) for maintenance workers in a chemical plant < 10 No. Oi9f 10 - 19.9 No. %_ 20 - 29.9 No. O*f 30+ No. %_ 49 26 27 15 41 22 68 37 A similar study of 137 oil refinery workers was conducted. Employees with a duration of employment of more chan 20 years were studied; almost half of chose examined had more than 30 years of employment (Tables 3 A 4). Table 3. Age distribution of 137 refinery vorkers Age (yrs) 40 - 49" No. 50 - 59 No. X 60 - 69 No. Omf 37 27 79 57.7 18 13.1 70+ No. ant 3 2.2 a No refinery workers under 40 years of age were examined. 002244 .. 18-0000824 ASBESTOSIS AMONG MAINTENANCE WORKERS 797 Table 4. Duration since onset of work (yrs) in 137 refinery workers 15 - 19 Wo. Vm 20 - 29 No. X___ 30 39 Wo. %___ 4Q+ No^ *4 1 0.7 74 54.0 50 36.5 12 8.8 The examination protocol included a lifetime occupational history, past medical history, smoking history. Medical Research Council respir atory questionnaire, complete physical examination, standard 14 * 17 inch posteroanterior chest X-ray films and pulmonary function tests (spirometry and maximal expiratory flow volume curves). Chest X-ray films were read with no knowledge of past medical history, occupational history, respiratory symptoms or findings on physical examination, and categorised according to the HO D/C Inter national Classification of Radiographs of Pneumoconioses (International Labour Office, 1972). Results of pulmonary function tests - measure ments of forced vital capacity (FVC), forced expiratory volume 1 second (FEVj) and forced expiratory flow over the mid-FVC (FEF25-75) " were compared with the values predicted by Morris et al. (1971), with no knowledge of occupational history, radiological findings, symptoms or findings on physical examination. Radiological findings RESULTS 1. Chemical 'plant maintenance workers Small irregular opacities, mostly in the lower lung fields, some times extending to the middle lung fields, indicating parenchymal inter stitial fibrosis, were present in 24Z of those examined; in 10Z this was the only abnormality (Table 5). Pleural thickening and calcification (with or without thickening) in 10Z and 4Z of cases, respectively, were found in the absence of definite radlologlcally evident parenchymal abnormalities; 14Z of all those examined had pleural abnormalities only; in another 14Z, both parenchymal and pleural changes were seen. The overall prevalence of parenchymal and/or pleural abnormalities consistent with asbestosinduced changes was 38Z. As expected, the prevalence of all chest X-ray abnormalities was higher in workers with more than 20 years since onset of work (Table 6); pleural changes were a more frequent abnormality in the group than were parenchymal ones. 002246 18-0000825 798 LIUS ET AL Table'5. Chest X-ray abnormalities consistent with asbestos-induced changes (parenchymal and pleural) in 185 maintenance workers in a chemical plant . Radiological change (ILO U/C)a Proportion of workers No. Of * None 0/0-0/1 e Parenchymal changes, total 1/0-1/2 2/1-2/3 3/2-3/4 Parenchymal changes only Pleural changes, total Pleural thickening only Pleural calcification (with or without thickening) 115 45 42 3 0 19 ' 51 18 7 62 24 22.4 1.6 - 10 28 10 4 a International Labour Office (1972) Careful analyses of life-long occupational histories recorded for all 185 maintenance workers revealed that in 140 there had been no previous specific, defined occupational or nonoccupational dust exposure. In 45 vorkers, asbestos exposure,ranging from minimal to significant, had occurred in the past, preceding employment in the chemical plant. Among chose considered to have had significant previous exposure were workers who had been employed in an asbestos manufacturing plant, had been active as pipefitters or pipecoverers, had worked in brake maintenance and repair, or had participated in boiler repair work. Those considered to have had minor previous exposure included vorkers involved in spackling, shingle trimming, brake repair (minimal, inter mittent), and in one case, residence in the neighbourhood (two blocks away) of an asbestos products manufacturing plant. A separate analysis was made of workers with no (even minimal) known pre-existing asbestos exposure. When comparing the results with those obtained for the entire group of 185 workers, it was found that the prevalence of radiological abnormalities, both parenchymal and pleural, was almost identical (Table 7). The relationship between radiological abnormalities and duration since onset of exposure (Table 8) was very similar in the group of 140 maintenance workers with no previous known asbestos exposure and in the 002246 l8-0000826 r ASBESTOS IS AMONG MAINTENANCE WORKERS 799 Table 6. Duration since onset of asbestos exposure and chest X-ray changes In 185 maintenance workers _______ Radiological changes2 Normal (0/0-0/1) Parenchymal changes (total) 1/0-1/2 2/1-2/3 3/2-3/4 Parenchymal changes only Proportion of workers Less than 20 years (N = 77) No. % -- 66 86 9 12 8 10 11 0- 8 10 More than 20 years (N = 108) No. t " 49 45 36 ` 33 34 31 02 2 * n 10 Pleural changes (total) Pleural thickening only Pleural calcification (with or without thicken ing, without parenchymal changes) 3 1 1 . 4 48 1 17 16 44 16 6 a International Labour Office (1972) tocal group of 185 examined workers (Tables 5 & 6); there was no statistically significant difference in prevalence of parenchymal or pleural changes.. 2. Oil refinery workers Small irregular opacities, indicating interstitial pulmonary fibrosis, were detected in 31 (23%) cases; in 20 (15%) this was the only radio logical abnormality. Radiological abnormalities of the pleura (pleural fibrosis and/or calcification) were found in 34 (25%) cases; in 23 (17%), pleural abnormalities were found in the absence of radlologically detectable parenchymal changes (Table 9). 18-0000827 800 LIUS ET AL. Table 7. Chest X-ray abnormalities consistent with asbestos-induced changes (parenchymal and pleural) in 140 .maintenance workers with no previous asbestos exposure Radiological change (IL0 U/C) Proportion of workers No. None(0/0-Q/1) Parenchymal changes, total 1/0-1/2 2/1-2/3 3/2-3/4 Parenchymal changes only Pleural changes (total) Pleural thickening only Pleural calcification (with or without thickening) 90 34 31 3 0 12 ' 38 14 2 64 24 22 2 - 9 27 10 1 a International Labour Office (1972) When che six insulation workers were removed from che analysis (Table 10), che prevalence of parenchymal abnormalities remained iden tical, while that of pleural abnormalities was found to be slightly lower: 22.5% of cases had pleural changes, and in 1ST these were the only radiological abnormalities. Clinical findings - symptoms and signs The only symptom reported with a higher frequency in workers with radiological abnormalities was dyspnoea on exertion. Cough and sputum production consistent with a diagnosis of chronic bronchitis (Table 11) were found in 20% of the chemical plant maintenance workers examined. The difference in prevalence between current smokers and individuals who had never smoked regularly was not significant (22% versus 14%) in this group. In the oil refinery workers, chronic bronchitis was found with a prevalence of 23.5% and was significantly higher in current smokers (Table 12). Abnormalities on physical examination were infrequent; rales were present mostly in persons with pleural changes. G0224<3 18-0000828 ASBESTOS IS WONG MAINTENANCE WORKERS 801 Table 8. Ouration since onset of asbestos exposure and chest X-ray changes in 140 maintenance workers with no previous asbestos exposure Radiological changes Normal (0/0-0/1) Parenchymal changes (total) 1/0-1/2 2/1-2/3 3/2-3/4 Parenchymal changes only Pleural changes (total) Pleural thickening only Pleural calcification (with or without thicken ing, without parenchymal changes) Proportion of workers Less than 20 years (N = 61) No. X ---- 54 89 6 10 58 12 0m 4* 7 35 12 0 More than 20 years (N = 79) No. 1111 m "1 36 46 28 35 26 33 23 0 8 10 35 44 13 16 23 a International Labour Office (1972) ^ 'Parenchymal changes only* was the only radiological abnormality with significantly higher prevalence in workers with previous asbestos exposure (x2 = 4.63; P < 0.05). Results of pulmonary function tests In chemical plane maintenance workers, pulmonary function tests (Table 13) indicated a relatively low prevalence of restrictive dys function (5Z of cases), probably related to the small number of cases with advanced parenchymal fibrosis. An obstructive pattern, was found more often and was, as expected, more prevalent in current and ex smokers. The finding of a lower chan normal FEV]:FVC ratio in 172 of maintenance workers with a negative smoking history suggests that dust, irritant fumes and gases in an industrial environment may have an adverse effect on respiratory function. 002243 18-0000829 802 LILIS ET AL. Table 9. Chest X-ray abnormalities consistent with asbestos-induced changes (parenchymal and pleural) in 135 refinery workers0 Radiological change (ILO U/C)* Proportion of workers No. i None (O/O-O/l) Parenchymal changes (total) 1/0-1n 2/1-2/3 3/2-3/A Parenchymal changes only Pleural changes (total) Pleural thickening only Pleural calcification (with or without pleural thickening, without parenchymal changes) 81 31 28 3 0 20 34 20 3 60 23 20.7 2.2 - 14.8 25.2 14.8 2.2 a Two of the workers' chest X-ray films were unreadable. b International Labour Office (1972) Table 10. Chest X-ray abnormalities consistent with asbestos-induced changes (parenchymal and pleural) in 129 refinery workers with no direct asbestos exposure0 Radiologipal change (ILO U/C) Proportion of workers No. O<f None (O/O-O/l) Parenchymal changes (total) 1/0-1/2 2/1-2/3 3/2-3Z4 Parenchymal changes only Pleural changes (total) Pleural thickening only Pleural calcification (with or without pleural thickening, without paren chymal changes) 80 30 27 3 0 20 29 16 3 62.0 23.3 20.9 2.3 15.5 22.5 12.4 2.3 a Excluding six insulation workers b International Labour Office (1972) 02250 18-0000830 ASBESTOSI5 AMONG MAINTENANCE WORKERS 803 Table IV. Prevalence of chronic bronchitis in maintenance workers in a chemical plant Smoking habits Total no. examined Proportion with chronic bronchitis NO. V* Present smoker Ex-smoker Never smoked Total* 67 75 42 184 15 15 J5 36 22 20 14 20 a Medical Research Council respiratory questionnaire * Excluding one subject for whom no smoking history was recorded Table 12. Prevalence of chronic bronchitis in oil refinery workers Smoking habits Total no. examined Proportion with chronic bronchitis No. % Present smoker Ex-smoker Never smoked Total* 42 55 _39 136 ' 16 11 5 32 38 20 12.8 23.5 a Medical Research Council respiratory questionnaire Excluding one subject for whom no smoking history was recorded In the oil refinery workers, restrictive ventilatory dysfunction (TVC < 80X of predicted) was found in 141 of cases, while an obstructive pattern was detected in 10.3Z of cases (Table 14). The prevalence of restrictive ventilatory dysfunction in oil refinery workers was higher chan in the chemical plant maintenance workers. An obstructive pattern of respiratory dysfunction was not found in oil refinery workers with a negative smoking history. This confirms that irritant fumes and gases in the chemical Industry sig nificantly contribute to the obstructive ventilatory dysfunction found, even in nonsmokers. ; ; i 1 21 l 002251 18-0000831 804 LIUS ET AL. Ttble 13. Pulmonary function abnormalities - restrictive and obstruc tive pattern in maintenance workers in a chemical plant Restrictive dysfunction FVC 791 of predicted Obstructive dysfunction FEV,:FVC * 741 (only) FEF25.75 f 571 of predicted (only) Both abnormalities Total obstructive dysfunction Current saoker (N ** 67) No. s Ex-saoker (N = 75) No. 1 Z <U* 3 6 (3)b 8 6 9 10 13 0 -1 1 12 18 17 23 18 27 28 37 Never sacked (N = 42) No. 1 25 7 17 0- 0- 7* 17 Total (N = 184) No. 1 10 5.4 23 12.5 1 0.5 29 15.7 53 28.7 a FEYi - forced explretoiy volwne (1 see); FVC - forced rial eeoerfty; FEF,, . forced explritory flow over the 1d-FVC -/s 6 Figure* In perenthescs - alxed ventlletory dysfunction, predoalnently restrictive 0 Tests Inooieplete In two subjects (FEF2J_75 not ivslleble) ^ Difference in prevtlence of obstructive dysfunction between current saokers *nd nonsmokers sutlstlcelly nonslgnlflcent (xJ = 1.52; P s 0.25) Table 14. Pulmonary function abnormalities - restrictive and obstruc tive pattern - in refinery workers Restrictive dysfunction FVC 4 79* of predicted Obstructive dysfunction FEV,;FVC 4 7** Curent smoker (N = 42) No. 1 Ex-smoker (N = 55) No. 1___ Never smoked (N s 39) No. 1 Total . (N = 136)* No. X____ 9 21.4 6 10.9 4 10.3 19 14 7 16.7 7 12.7 0 - 14 10.3 a FVC - Forced vita) capacity; FEVi - Forced expiratory volume 0 sec) * No smoking history was obtained for one worker. DISCUSSION While in these groups of chemical plant maintenance vorkers and oil refinery workers chest X-ray abnormalities were relatively frequent, pleural changes being more prevalent than parenchymal fibrosis, subjec tive symptoms and pulmonary function abnormalities were much less pro minent. This constellation has been found to be rather characteristic for relatively less Intense asbestos exposure. While progression to severe disabling parenchymal asbestosis is less probable under such circumstances, the risk for lung cancer and mesothelioma remains. 1S_0000832 * ASBESTOSIS AMONG MAINTENANCE WORKERS 805 The chemical plant maintenance workers examined had had various degrees of asbestos exposure; more than half of t' "tamined had never been directly engaged in work with asbestos.* ' '*s they had been present in areas where such work was per A list of some of the job designations in this las' Table 15. Table 15. Maintenance workers' occupations w' asbestos Labourer Stock man Area mechani Sheet-metal Mechanic's Maintenanc Mlllwrigh' Repair mr Pipefitt Product insulators. A list of job designations of oil refinery wo. is given in Table 16. Table 16. Refinery workers' occupations with no direct handling of asbestos Boilermaker Carpenter Crane operator Distillation worker Electrician Filter plant operate Forklift operator Inspection worker Labourer Painter Shipping checker Still operator Welder Comparative analysis of the entire group of maintenance workers, and of the 140 subjects wit exposure,- yielded interesting results: prevalec abnormalities (both parenchymal and pleural) wei 002253 18-0000833 .806 LIUS ET AL. The relxdonship between prevalence of radiological abnormalities and duration since onset of exposure was also very similar. Also, in the group of oil refinery workers, exclusion from the analysis of six . employees who had been insulators did not influence the prevalence of ' . radiological abnormalities. These findings strongly suggest that asbestos exposure characteristic of maintenance work in chemical plants and in oil refineries. Including indirect ('bystander') exposure, results ifi risks comparable, although not identical, to those documented for other types of asbestos exposure in other industries and occupations. The higher prevalence of radiological pleural abnormalities (pleural fibrosis and/or calcification) chan of parenchymal small irregular opacities (interstitial pulmonary fibrosis), -the fact that parenchymal abnormalities were not very advanced (in only a small proportion of cases exceeding 2/1) and the paucity of clinical abnormalities all indicate that the risk for disabling asbestos!s is less with this type of asbestos exposure. In 1971, reports by Blttersohl (1971) and by Bittersohl & Ose (1971) had called attention to asbestos hazards in the chemical industry. Twenty-six cases of mesothelioma had been observed over a period of four years (1967-1971); this was in sharp contrast with the extreme rarity of this type of malignancy in the preceding period. Twenty-two patient/" had worked in a large chemical industry (Leuna), two in another chemical * plant (Buna) and one in a foundry. The only female patient bad had no occupational exposure to asbestos, but was the wife of a worker at the Leuna plant. Only 16 patients had had direct occupational exposure to asbestos, while nine had had indirect exposure (working in areas where asbestos was occasionally handled by other workers); is one case there was only a history of household exposure. Chest X-ray films taken before the development of mesothelioma were available in 23 cases; in 17, pleural thickening and pleural plaques were present. It was known that extensive insulation work had taken place in several departments of the Leuna chemical plant in the early 1950s. Large amounts of asbestos had been used, and evidence was available that there had been high concentrations of airborne fibres in the pest. Maintenance work was thought to carry a special risk. The risk of lung cancer and mesothelioma is of concern for main tenance workers in the chemical industry and for oil refinery workers, since accumulated experience indicates that low-level asbestos exposure (Indirect occupational, neighbourhood or household exposure) is suffi cient to result in a significant risk of developing mesothelioma (Harries ec al., 1972; Newhouse 6 Thompson, 1965; Selikoff, 1977; Wagner er el., I960). It is possible that an increasing number of such cases may occur, since spectacular growth of these industries ha# taken place over the last 25-35 years, which is, on the average, the critical latent period (Selikoff, 1977). 002254- is- o0l T ASBESTOS IS AMONG MAINTENANCE WORKERS 807 SMftRf . Adverse health effects associated with asbestos exposure are wall known and docum&ted for occupational groups directly exposed to asbestos - asbestos miners, asbestos textile workers, insulation workers, - Bow* ever, the health hazards due to asbestos have not been completely ascer tained for chose workers who are indirectly exposed in industries where asbestos insulation was used extensively. In order to evaluate the potential asbestos hazards in maintenance workers in the chemical Industry and in oil refinery workers, two cross sectional clinical field examinations were conducted: 185 maintenance workers in a large chemical plant and 137 oil refinery worker* were studied. Long-term employment (more than 20 years) was characteristic for both groups. In the chemical plant maintenance workers, radiological evidence of parenchymal interstitial fibrosis was found in 24Z of the group; in 10Z this was the only abnormality. Pleural fibrosis and/or calcifi cation was found in the absence' of parenchymal fibrosis in 14Z of cases; in another 14Z, both parenchymal and pleural abnormalities were detected. The prevalence was significantly higher in those employed for 20 or more years. In the oil refinery workers, small Irregular opacities, indicating interstitial pulmonary fibrosis, were detected in 31 (23Z) eases; in 20 (15Z), this waa the only radiological abnormality. Radiological abnormalities of the pleura (pleural fibrosis and/or calcification) were found in 34 (25Z) cases; in 23 (17Z), pleural abnormalities were found in the absence of radlologlcally detectable parenchymal changes. In both groups, pleural abnormalities were more prevalent than parenchymal changes. These findings indicate that radiological evidence of asbescosls is to be found with significant prevalence in chemical plant maintenance workers and in oil refinery workers. The risk of developing severe disabling pulmonary fibrosis seems to be unlikely, since few of the cases had small Irregular opacities graded 2/1 or higher. The risk of lung cancer and/or mesothelioma in these workers has yet to be assessed. 00225-5 * i i8-0000S35^ A. 808 LILIS ET AL.' RESCUE Lea*effeta adverse* aur la sant associs 1 1'exposition % l'amiante aone bien conaus et bien tudls dans les groupes professionnels direccement exposes 1 cette substance - mineurs d'amiante, travaillenra de 1'Industrie textile exposes i 1'amiantc, travailleurs de l'lndustrie des isolants. Mala on n'a pas complfctement dtermini les dangers de 1'aslante pour les travailleurs qui sent lndirectement exposes dans les industries ayant fait un large eaploi de l'aaiance comae isolant. Afin d'evaiuer les dangers potentials de l'amiante pour le per sonnel d'entretien de 1'Industrie chimlque at pour celui des raffineries de pitrole, les auteurs ont effectu deux enquetes cliniques tranaversales: 185 membres du personnel d'entretien d'une grande entreprise chimlque et 137 membres du personnel d'une rafflnerle de petrole ont t Studies. Les deux groupes se caractrlsaient par un emploi de longue duree (plus de 20 ana). Parmi le personnel d'entretien de l'usine cbimique, on a observi des aignes radiologiques de fibrose interstitlelle parenchymateuse chez 24Z des sujets; chez 10Z ils constltuaient la seule anooalie. Uhe fibrose et/ou une calcification pleurales ont t constaties en 1'absence de fibrose parenchymateuse dans 14Z des cas; dans une autre proportion de 14Z, on a detecti des anomalies la fols parenchymateuses et pleu rales. La prevalence s'avirait senslblement plus forte chez les personnes employees pendant 20 ana ou plus., Parmi les employes de la rafflnerle de ptrole, de petites opacits irregulifcres, rvelatrices d'une fibrose pulmonalre interstitlelle, ont et& decelees dans 31 (23Z) eas; chez 20 sujets (15Z) elles constltuaient la seule anomalie radiologlque. Des anomalies radiologiques de la plSvre (fibrose et/ou calcification pleurales) ont t observees dans 34 (25Z) cas; chez 23 sujets (17Z), les anomalies pleurales s'observalent en 1'absence de lesions parenchymateuses radiologiquement dScectables. Sana les deux groupes, la prvalence des anomalies pleurales 1'emportait sur celle des lsions parenchymateuses. Ces observations lndlquent qua les aignes radiologiques d'asbestose se rencontrent assez frquemment chez le personnel d'entretien des usines chlmiques et chez les travailleurs des raffineries de ptrole. Le risque d'apparition d'une fibrose pulmonalre grave et invalidante semble peu probable, car rares etalent les sujets prsentant des petites opacits lrregullires 0o. vJ O`-V' A')- Io l8-0000836 < ASBESTOSIS WONG MAINTENANCE WORKERS 809 classics 2/1 ou plus. Le risque de cancer du poumon et/ou de mesothiliome chez ces travailleurs rescc 2 determiner. <* ______ HEFHaCES Bittersohl, von G. (1971) Epideraiologische Untersuchungen uber Krebserkrankungen is der chemischen Industrie. Arch. Geschsulst- forach., 38, 198-209 . Bittersohl. von G. 4 Ose, H. (1971) Zur Epidemiologie des Pleuramesotheliooa. Z. gea. Byg., 17, 861-864 Daum, S.t Anderson, H., Lilia, R., Lorlmer, V.V., Flschbeln, A.S., Miller, A. 4 Selikoff, I.J. (1977) Pulmonary changes among titanium workers. B. Soc. Med. occttp. Med., 70, 31-32 Harries, P.G., Mackenzie, F., Sheers, G., Kemp, J.HOliver, T.F. 4 Wright, D.S. (1972) Radiological survey of men exposed to asbestos in naval dockyards. Br. J. ind. Med., 29, 274-279 International Labour Office (1972) Classification of Radiographs of the Pneumoconioses, 1971 (Occupational Health and Safety Series, Bo. 22) (revised), Geneva Lilis, R., Anderson, H., Nicholson, W.J., Daum, S., Fiachbein, A. 4 Selikoff, I.J. (1975) Prevalence of disease among vinyl chloride and polyvinyl chloride workers. Ann. B.I. Acad. Set., 248, 22-41 Lilis, R., Anderson, H., Miller, A. 4 Selikoff, I.J. (1976) Pulmonary changes among vinyl chloride polymerization workers. Cheat, 69, 299-303 Lorimer, V.V., Lilis, R., Nicholson, W.J., Anderson, H.A., Fischbein, A., Daum, S., Rom, W., Rice, C. 4 Selikoff, I.J. (1976) Clinical studies of styrene workers: initial findings. Environ. Health Perapect., 17, 171-181 Morris, J.F., Kolski, A. 4 Johnson, L.C. (1971) Splrometric standards for healthy nonsmoking adults. Am. Rev. reap. Dia., 103, 57-67 Newhouse, M.L. 4 Thompson, H. (1965) Mesothelioma of pleura and peri toneum following exposure to asbestos in the London area. Br. J. ind. Med., 22, 261-269 Selikoff, I.J. (1977) Cancer risk of asbestos exposure. In: Hiatt, H.H., Watson, J.D. 4 Winsten, J.A., eds. Origins of Human Ccncer, Cold Spring Harbor, N.Y., Cold Spring Harbor Laboratory, pp. 1765 1784 00225/ 18-0000837 8V) LIUS ET AL. Vagner, J.C., Slcgga, C. A Marchand, P. (1960) . Diffuse pleural nesothellona and asbestos exposure in the North Western Cape Province. Br. J. incL. Mad., 17, 260-271 e C0'225<3 18-0000838 r