Document NEzMRKg1zgaE8XozZV61jL0zE

Int Arch Occup Environ Health (1989) 61 :261-270 `1nst.ltuteof Occupational Health. 'Clinics L. Devoto", Via S m Barnaba. 8. Unibrrsith degli Studi di Milano, 1-20122 Milano. Italy 'Clinics del Lavoro. Istituti Clinici di Prrfezionamento, 1-20122 Milano. Italv Summary. The mortality experience of 1595 male workers empIoyed in one of the largest Italian refineries in the period from 1949-1982 was examined. From the comparison with national and local death rates, increases in mortality owing to lung and kidney can- cers, brain tumors, and leukemias emerged. No defi- nite trends according to duration of exposure and years since first exposure were apparent. The increases regarding cancer of the lung, kidney and brain appearred t o be associated with the early period of operations. Analysis by exposure category suggested an -ation of the increased mortality from leukemias with working in production (observed = 2; expected = 0.61). Kidney cancer mortality was elevated among m b t e n a n c e workers (obs. = 2; exp. = 0.18). Small nWbers prevented firmer conclusions. Workers in tb moving department had a significantly increased mortarity from all cancers (obs. = 22; exp. = 11.7), and lung cancer (obs. = 11; exp. = 3.6). Confounding by smoking could be excluded as sufficient explaW b n of the three-fold increase in lung cancer deaths. It was in moving that highest airborne levels of polynudear aromatic hydrocarbons had been discovered an independent environmental investigation. h`words: Polynuclear aromatic hydrocarbons -(PAWS) - Epidemiology - Mortality - Occupational Oil refinery perimental. as well as epidemiological studies in the process of human carcinogenesis [19-22, 301. Over the last decade, particular attention has been devoted to the possible cancer risk carried by exposures pertaining to working in petroleum refineries. Studies have been conducted in various settings and countries, and different approaches have been implemented: ecological investigations [6,7,13,28], mortality [ l ,9, 10, 14-17, 23, 29, 33, 35, 38-41, 43-47] and incidence [37] studies, and case-control studies [3. 4, 8. 25, 26, 341. Despite certain limitations, mainly related to non availability of exposure data, and faiIure to control for confounding, these investigations have suggested possible cancer risks associated with working in oil refineries [36]. The findings. however. were not fully consistent, and further research was deemed necessary [ 181. We thought it useful, therefore. to study the can- cer mortality experience of the employees at a refin- ery plant located in the vicinity of Milan (Italy), one of the Iargest and earliest in the country, after verifying the availability of a good data source since the late 1940s. The aim o f the study was twofold: to ascertain whether a cancer risk existed in that particular working population, and to investigate whether the risk, if any. was associated with specific jobs or plant processes and. hence. exposures. Imhduetion PcQOleum and petroleum products have a complex -mWition. The principal constituents are hydro- some of which have been implicated by ex- 8s to: P. A. Bertazzi Subjects and methods Srudy populunon All male worker5 ever employed at the plant in any department between January I , 1949 and December 3 1. 1982 were considered eligthle. The examinatton of personnel file4 led to the identification of 1595 subjects meeting the admission criteria Despite changes in the uwnership of the plant, contidence could be placed on the complete enumeration of the cohort, since regulations in Italy require that a complete t I p.+rtazzi et al.: Cancer and oil refinery ,$+V T&I. Completion of the follow-up at the closing date of the snap.@ecernber31,1982) S"&Cr-* No. Percent W&em in the study 1595 1363 213 19 100.0 85.4 13.4 1.2 Tdle 2. Person-years of observation accrued during the study period (1949-1982), and their distribution by attained age and vw of first emdovment Year of the first employment Total < 1954 1954-1962 > 1%2 199.5 2278.5 4 108.0 4921.5 2872.0 923.5 91.5 ' 15394.5 209.0 1230.0 1870.0 1412.0 671.5 211.5 42.0 5646.0 729.0 3274.0 2946.5 893.5 154.0 4.5 0.0 8001.5 1137.5 6782.5 8924.5 7227.0 3697.5 1139.5 133.5 29042.0 Results 263 The vital statistics were successfully ascertained for nearly 99% of the study subjects (Table 1). Two hundred thirteen deaths had occurred and 201 complete death certificates were obtained. During the study period, nearly 30000 personyears of observation were accrued. Their distribution according to attained age and year of first employment is shown in Table 2. In Table 3, results of the comparison of mortality from selected causes or group of causes in the study population with the corresponding mortality of the national and the local population are reported. In fact, quite different standardized mortality ratios were obtained depending upon the reference rates used. Overall mortality did not differ from the na- tional one, while it was significantly lower than that of the local population. For each of the cancer causes considered, observed mortality was greater than ex- pected from national rates with a few exceptions. The 207.71 102 89-117 53.10 149 118-185 18.45 1.44 125 208 79-187 53-567 8.37 131 2.81 71 1.69 177 2.41 83 1.78 112 69-22a 12-235 45-483 14-274 19-371 14.54 199 136-283 0.92 325 83-887 2.35 170 54-411 4.29 186 87-354 1.89 1.90 74.12 33.61 17.97 14.41 20.93 13.52 22.20 159 264 88 107 61 35 62 44 81 40-432 %583 68-112 75-148 32-106 13-77 34-103 18-92 50-126 267.02 80 69-91 80.58 98 78-I22 26.86 86 54-128 1.97 152 24-355 11.60 95 50-165 3.38 .-59 10-195 2.47 121 31-330 3.16 63 11-209 2.93 68 14-225 23.80 122 82-175 0.84 358 91-974 2.08 193 61-464 5.67 141 65-268 2.90 103 26-281 2.03 246 90-544 94.83 68 53-87 48.47 23.56 74 52-103 47 25-81 15.16 33 12-74 25.81 18.53 50 28-84 32 13-67 20.51 88 57-136 264 TI& 1.Mortality from selected cancer causa of oil rebaer), workers according to length of employment in the plant; refe- n n t , local Dodation Cause of death Length of employment (years) c5 5-15 >15 Au cancers Obs/Exp 8111.19 SMR 72 Digestive system cancers ObsIExp 113.79 SMR 26 Stomach ObsIExp 111.88 S M R 53 Lung cancers OblExp 412.89 SMR 139 Kidney cancers ObsIExp 010.14 SMR 0 Braintumors ObslExp 110.33 SMR 303 Lymphatic and hemapoietic callcers '- ObslExp SMR 211.13 177 Leukemia ObslExp 110.45 S M R 223 '95% Confidence interval = 102-2002 b95% Confidenceinterval = 114-1219 35134.24 102 10111.95 a4 515.39 93 1519.39 160 210.33 606. 110.85 118 2/23 84 UO.92 109 36135.16 102 12111.12 108 514.32 116 10111.53 87 110.37 270 210.91 2u) 412.16185 310.67 448b P.A.Bertrmi et al.: Cancer T1MkiMobtalitgfropltrdeabwl~ workm accordingtooaleadar period of ferent, local population Cause of death Digestive system Cancers Stomach Lung cancers Kidneycancers Braintumors SMR 102 ObslErp 17120.04 M.11 S M R 85 98 ObslExp 8f8.85 3/2.15 SMR 90 139 ObdExp 24116.93 514.61 SMFt 142 108 ObslExp 30.63 110.17 SMR 318 0- 3/1.45 010.40 Lymphatic and hemopoietic cancers ObSlExp 313.81 211.1 sMR79 Table 5. Mortality from selected cancer causes of oil refinery workers according to years elapsed since the beginning of employment; referent, local population Cause of death Years since first employment <10 10-20 >20 All cancers ObslExp 9112.24 SMR 74 Digestive system Cancers ObslExp 114.23 SMR 24 Stomach ObsIExp 112.50 SMR 40 Lung cancers ObslExp 313.03 SMR 99 Kidney cancers ObslExp 010.12 SMR 0 Brain tumors ObslExp 210.42 SMR 479 Lymphatic and hemopoietic cancers ObslExp 211.42 SMR 141 Leukemia Obs/Exp 1/0.59 SMR 171 '95% Confidence intervai = 119-1276 30126.91 111 1219.68 124 714.29 163 917.28 163 110.20 500 210.78 256 411.82 220 310.64 46g8 4141.45 96 10112.94 77 314.80 62 17113.49 62 210.52 385 010.88 0 212.43 82 110.82 122 noted excesses turned out to be statisti cant for all cancers and lung cancer, and nificant for deaths due to leukemias. In co with the local rates, for no cancer sites did depart significantly from 100. Deaths from the esophagus, rectum, lung, and lympho plasms were slightly higher than expected. MO nounced, albeit statistically not significant, wasthe excess mortality from kidney cancer, brain tumors,md leukemias. Among malignancies, the only instawes in which the SMRs were higher when based on local. rather than national expected figures were kidney cancer and brain tumors.One single case of melanoma and one of prostate cancer were observed. The numbers of observed deaths from non-malignant diseases were consistently lower than expected. The only exception was ischemic heart disease, when compared with national rates. In particular, the large deficits in mortality from non-malignant respiratory diseases, diseases of the digestive system, and &- rhosis were noteworthy. In the following tables, only comparison with local rates will be reported, the one consid most appropriate in the light of the previou tioned inter-regional variations in cancer m 1 p. A. B e d et al.: Cancer and oil refinery 265 T W 7. Mortality from selected sancer causes of oil refinery workers according to the department in which they had ver worked; referent, local population Cause of death Exposure classification by department (ever worked) Production Delivery Moving Maintenance Power plant L a b - Clerical ratories Others All cancers Digestive system cancers Stomach Lung cancers Kidney cancers Brain tumors Lymphatic and hemopoietic canc&rs Leukemia OIE SMR OIE SMR OIE SMR OIE SMR OIE SMR OIE SMR OIE SMR OIE SMR 19121.50 1315.61 22111.68 16118.10 1116.% 515.26 15121.00 13117.99 88 232" 188h 88 158 95 71 72 616.73 89 412.73 147 516.80 73 010.20 0 210.65 307 411.89 212 110.78 127 311.67 179 010.06 0 110.14 695 413.74 107 111.59 63 1113.61 305' 010.12 0 310.33 9ood 616.00 100 312.55 118 315.44 55 210.18 1112c 110.46 219 212.29 88 210.98 204 612.11 285' 010.07 0 110.19 540 111.63 61 110.63 158 211.65 121 010.05 0 110.17 573 517.30 69 113.22 31 615.96 101 010.24 0 010.47 0 216.04 33 112.57 39 715.31 132 110.20 501 010.44 0 211.66 121 210.61 330 010.36 0 010.11 0 010.85 0 010.30 0, 111.25 80 110.43 232 010.48 0 010.16 0 110.40 247 010.13 0 211.32 152 110.45 222 211.19 169 110.42 238 '95% Confidenceinterval = 129-386 b95% confudenceinterval = 118-285 '95% condidence interval = 160-530 d95% Confidence interval = 229-3000 '95% confidenceinterval = 186-3675 '95% -rice interval = 115-592 Analysis by length of employment yielded the reJults reported in Table 4. No definite patterns or cle8r.cut increasing trends in mortality were discern- ible, with the possible exception of digestive and StOllLIch cancer. Three leukemia deaths in the cate- goqofkmgest exposure made up a four-fold, statisti- cally Jisnificant excess. Also significant was the in- weasod SMR for kidney cancer among those in the 5 15 year category; only two deaths, however, were o~rved. h a i y s i s by years since first employment failed to show Consistent patterns in mortality (Table 5 ) . The ' a r m excesses were seen, in general, after 10 to 20 Yeam h c e starting work in the plant. The departure From100 of the SMR for leukemia in this subcohort stathtica~ysignificant. 'bcalendar time of first employment appeared to be somehow associated with the mortality experi- enceOf the employees. Intervals were chosen, on an Priori basis,so as to correspond to periods of major h the production history of the plant. As *&Table 6, the lung cancer excess, although nonsignificant,was confined to those first employed in the early period of operation, prior to 1954. Three of the four brain tumors and two of the three kidney cancer deaths had occurred in this same subcohort of workers, making up respectively a twofold and three-fold statistically not significant excess mortality. The increased mortality from lymphopoietic neoplasms reached statistical significance among those first employed after 1962, and was entirely due to leukemia deaths. As regards cancer mortality by exposure category, workers were first classified as having ever worked in any of the categories (Table 7). Consequently, some of them are included in more than one category, and their deaths are counted more than once (total = 287 deaths, instead of 213). In Production, none of the SMR was significantly different from 100, although suggestions of increased mortality from stomach cancer and, particularly, leukemias and brain tumors were noted. Mortality from all cancers among work- ers ever employed in Delivery was significantly elevated. N o clusters of cancer deaths at specific sites departing significantly from expectations were seen; yet, mortality from cancer of the digestive tract and I I I I I I P. A. Bertazzi et a/.:Cancer and oil refine ry Table 8. Mortality from selected cancer causes of oil refinery workers having always operated in a single dpartment; referent, population Cause of death Expowre classification by department (uniqueJob) __4 Produc- Dellvery Moving tlon Maintenance Po\ler plant Laho- Clerical Othe;;'ratories All cancers Digestive system cancers Stomach Lung cancers Kidney cancers Brain tumors Lymphatic and hemopoietic cancers Leukemia O/E SMR OIE SMR O1E SMR O/E SMR O1E SMR O/E SMR OIE SMR O/E SMR 718 57 82 312.66 113 211.09 184 012.71 0 010.08 0 010.26 0 210.71 282 210.28 704" 11091 109 110.32 314 110.15 674 010.25 0 010.01 0 010.02 0 914.40 204h 311.46 206 110.65 155 111.30 309 010.05 0 010.12 0 010.07 0 010.02 0 010.32 0 0/0.11 0 12111.35 413.18 I06 126 413.83 105 211.66 120 313.36 89 210.11 1750' 0/0.27 0 211.10 181 210.50 399 110.92 109 010.04 0 110.06 1632 311 81 166 9/13 98 h4 110.53 188 110.20 492 110.59 169 010.02 0 010.06 0 315.02 60 012.30 0 313.80 79 010.17 0 010.28 0 7/9.84 71 013.43 0 011.52 0 412.73 147 U0.12 838 0lO.u 0 110.77 129 110.28 362 010.21 0 010.08 0 110.15 675 010.05 0 210.87 231 110.32 314 2/0.64 314 110.24 417 '995% Confidence interval = 118-2327 b95% Confidence interval = 100-375 '95% Confidence interval = 293-5781 lung was clearly elevated. Among workers in Moving, statistically significant increases were noted for all cancers and cancer of the lung, based on 22 and 11 deaths. respectively: also significant was the elevated mortality from brain tumors. Indications of an unusual mortality experience from kidney cancer emerged among Maintenance workers; only two deaths were observed, but they made up a significant increase above expectations. Workers in Power Plant exhibited a higher than expected mortality from cancer causes: the excess of lung cancer deaths reached statistical significance. In the Laboratories feu deaths were observed. Among Clerical workers the only SMR above 100 was noted for lymphopoietic neoplasm deaths. Workers classified as Others exhibited a number of deaths due to lung cancer and Iymphopoietic neoplasm slightly higher than expected. Analysis by job held longest tended to confirm the prebious findings: of course, smaller numbers affected statistical significance. Table 8 presents results of analysis for those workers always employed in one single department. The two leukemia deaths among Production workers yielded an SMR of around 700. statistically significant. The increase in all cancer mortality among mov- ing operators was of borderline significance; the previously noted three-fold increased lung cancer risk remained essentially unchanged. The elevated risk from kidney cancer among Maintenance workers was confirmed. Lung cancer mortality among moving operaton was further analyzed in order to control for possible confounding by smoking. The plant health service had been recording the smoking habits of the worken. as reported by workers themselves at the time of hiring. Unfortunately. not all the records had been kept and thus at the time the study was conducted, thc smoking habits were known for more than 95.0% 01 the active workers. but only for 10.4?'0 of former employees. The proportional distribution of these retired workers by exposure category turned out to be almost identical to that of current employees, thus suggesting that this sample was not heavily biased. and probably representative of the smoking habits of the past workforce. We thought it reasonable, then. to base the estimate of the smoking habits in the entire cohort upon this information, even though it was limited. The percentage of habitual smokers in each exposure category turned out to be as follows: Production 71%. Delivery 67%. Moving 70%, Mainte- ' I p. A.Bertavi et al.: Cancer and oil refinery Table 9. Hypothetical smoking adjusted SMRs for lung cancer among Moving operators (unadjusted SMR = 305), and smok- ing distribution in the referent population to be assumed to sustained the hypotheses Adjusted SMR Smoking distribution in the referent population (dgarettesld) Non- < 10 10-20 > 20 smokers 100 > 75% <20% < 5 % 0Yo 150 > 45% 5-SOYo < 2SYO 5% 200 > 20% 5-7590 e 35% < 15% nance 60%, Power plant 60%, Labs 67%, Clerical 73%, Others 56%. Based on these data. it seemed quite hard to interpret the outstanding excess of lung cancer deaths noted among Moving operators on the sole basis of smoking habits. The method suggested by Axelson in order to control for smoking [ 5 ] was adapted to our data. The distribution of smoking habits among the workers was estimated from the available data. Estimates of the lung cancer relative risk associated with different smoking habits were as- sumed to be 5.0 for smoking < 10 cigarettedd, 10.0 for 10 to 20 cigarettedd, and 20.0 for >20 cigarettes/ d. We then calculated the smoking habit distribution in the referent population necessary to explain the three-fold increase in lung cancer mortality noted among these workers solely on the basis of differences in Smoking habits between the study and referent Population, viz. true SMR after controlling for smoking = 100. This distribution is shown in Table 9, and appeared too extreme to be credible. The table gives a amre general view of the extent of confounding m b l y introduced by smoking in these results. Only a mkmg adjusted SMR = 200 (or greater) appeared possibly correspond to reasonably anticipatable rmhgdistributions in the referent population. Un %cohort of Italian oil refinery workers had a cancer mortality significantly higher than expected from lhe Population of the same sex and birth cohort in the wholecountry. The excess mortality was noteworthy forseveral causes, which corresponded well to those "Us8ested by previous studies, i.e. lung (the elevated Rs' being statistically significant), digestive tract, lymphatic and hemopoietic tissues and brain. a different pattern was obtained when local rateswere used to calculate expected numbers. et-*' the dramatic decrease of nearly all SMR excess mortality from kidney cancer, brain tumors and leukemias remained essentially un- changed. Under the assumption that an association between workers' mortality and working experience exists, one expects that the longer the employment, the more pronounced the effect will be. Exception to that are short-term employees, whose mortality usually appears to be unfavourable [121. Suggestive increases in mortality with increasing length of employment were only noted for cancer of the digestive tract. The time elapsed since the beginning of employment is not only a popular, but also a viable approximation of the time required for a long-term effect (e.g. cancer) of chemical exposure to become manifest [31]. In our data, however, no clear indications of an increased risk with increasing number of years since first employment emerged. The calendar period in which employment started is of interest for several reasons. For instance, it is reasonable to assume that in early periods working conditions were poorer, owing to both the type of technology in use and the quality and extent of pro- tective devices available. In addition. such an analysis may help in pinpointing periods of the production history involving particular risks. It was thus noted that the slight increase of lung cancer mortality noted in the entire cohort was clearly related to early years of employment. This was also the case for kidney cancer and brain tumors. The statistically significantly elevated risk from neoplasms of lymphatic and hemopoietic tissues, and more specifically leukemias, noted for those first employed after 1962, could not be associated, to the best of our knowledge, to peculiar exposure opportunities inside the plant during such a time period. Thus, results for the entire cohort of refinery workers provided suggestions of a possibly unusual mortality owing to leukemias, kidney cancer, brain tumors and lung cancer in some segments of the cohort. Analysis according to job held inside the plant shed some further light. The increased risk from leukemias appeared to be associated with working in production. Interpretation of the nature of this association was hampered by the small number of deaths observed. Exposure to hydrocarbons (including benzene) in recent years was shown to be well below the current limit values. Measurements in the past years were not available, yet the assumption that concentrations in the past were higher is most reasonable. The two workers always employed in production who died from leukemia (one "acute leukemia" and one chronic lymphatic leukemia) started work in the early MOs, and their exposure lasted for more than 15 years. An increased risk from leukemias had been suggested by previous investigations [10, 24, 37, 40, 11 ,1 1; I I! I i 268 41,451. In one study a statistically significant increase was found; the excess mortality was mainly due to acute myeloid leukemia [24], and it was not possible to relate this excess to any particular job or department, or specifically to benzene exposure [4]. In another one [41], the increase was related to working in Treating (a job title similar to our production), and Boiler-making (included in our maintenance). The latter job was also found at risk in another study [lo]. The most distinctive pattern of increased cancer mortality seemed to be the one observed in association with moving operations. Significant excess mortality from all cancers, lung cancer and brain tumors was noted. Analysis by longest job held, and always in that job, confirmed, despite obvious numerical changes, the findings for all cancers and lung cancer, but did not allow attributing the increased brain tumor risk specifically to working in this department. The four lung cancer cases always employed in this department, all started work before 1955, and had a minimum length of exposure of 15 years. Exposure was composite, given the numerous operations performed, and possibly included. other than various hydrocarbons, hydrogen sulphide, tetraethyl lead, and several substances employed for denaturing commercial products; denaturing agents included, among others, dyes (in liquid and sometimes powder state), furfurole, diphenylamine, phtalates. All operations were automated. However, tanks of denaturing substances were sometimes filled up manually and samples taken manually for quality control purposes. The greatest opportunity for exposure to volatile hydrocarbons occurred during the loading operations, which required the manual connection of oil filler pipes to truck and train tanks, and manual measurements of product levels in tanks. In addition, workers were exposed, while staying at the filling platform, especially during the hot season, to volatiles coming from open tanks of standing trucks and trains. No measurements were available. as already stated. at the beginning of the study. They were taken. however. in 1985 and documented that a potential for high exposure actually existed. This, in fact, turned out to be the only department inside the plant where values higher than the current threshold limit values (TLV) were measured. Thus, for instance, at the "super gas oil" platform. during the manual sampling of filled tanks. five samples of total hydrocarbons showed values between 230 and 419mg/m3. vs a TLV of 180mg/m': two samples taken by means of personal passive sampler had values of 223 and 851mg/m'. Potential exposure to polynuclear aromatic hydrocarbons (PAHs) also existed during manual loading of packed bitumen. Thus, the excess lung cancer mortality noted among employees in this department might assume credibil- P. A. Bertazzi et ai.: Cancer and oil cry &,ity in the light of the environmental findings. sociation of lung cancer mortality with working in the petroleum industry was first suggested by mortality a]investigations in the general population [13, and ecological studies [6, 71. Further studies gave contrasting results. Two of them showed significantly elevated risks for lung cancer [14, 391, but could not associate that increase with occupations involving sPecific exposures. Five studies, on the other hand, found relative risks lower than 1.00 [15. 33, 37, 45, 471. Oil refinery workers have been shown to smoke less than workers in other industries [42]. We had no data from our country to corroborate those findings. However, smoking could be excluded as sufficient explanation for the increased lung cancer risk noted in this exposure category, for several reasons. First, internal comparison among exposure categories showed that the pattern of the estimated frequencyof smokers could not represent a satisfactory explana. tion for the results. Second, it was shown that for smoking to be the explanation of the three-fold increased lung cancer risk, it was necessary to assume a distribution of smoking habits in the reference population clearly not credible. Third, mortality from causes other than cancer known to be associated with smoking was definitely lower than expected; so,for example, five deaths from cardiovascular diseases were observed among moving workers vs 12.5 expected, and no deaths from chronic respiratory diseases were found vs 1.9expected. The increased mortality from all cancers suggestively associated with working in delivery might also find a possible explanation in the sort of exposure just described for moving. As a matter of fact, workers in delivery had the potential for exposure to the same type of chemicals as the movers, especially during weighing operations. The excess lung cancer mortality noted amoncg power plant workers almost disappeared when analysis was restricted to those always employed in the department. Still. the type of exposure. and the concentrations being possibly much higher in the past, renders this finding noteworthy too. The possible link between petroleum hydrocarbons and renal damage has been extensively reviewed recently [27], and a possibly elevated kidney cancer risk was suggested [15. 25. 26. 40, 461. In our study. having always worked in maintenance appeared to carry an increased risk from kidney cancer in comparison with the local population. Apart from statistical significance. the small number of deaths observed prevented firmer conclusions. The suggested increase can be hardly associated with any specific exposure because of the very nature of maintenance jobs. The two workers deceased from kidney cancer had been .. . . -.. . .. p. A.Bertaui et al.: Cancer and oil refinery both exposed for more than ten years, in the early period of operations (< 1954), and died 10 and 22 \rearsafter first exposure. The increased mortality from brain tumors, which was noteworthy in the whole cohort, could not be linked to any specific job or working process. The as- sociation of such an increased risk with oil refining had been suggested by numerous studies [2, 10. 15, 29, 37, 38, 401. None, however, could conclusively establish a causal link. On the basis of these findings, we thought that a further study of workers engaged in operations such as pumping and moving of petroleum products, and allied operations (e.g. marketing and distribution) was likely to be the most motivated and rewarding. Accordingly. we are collecting a larger cohort of similar workers from other plants and distribution centers, in order to further explore the cancer risk, if any, actually carried by exposures occurring during such operations. Concurrently, extension in time of the follow-up for the entire cohort has been planned. .+kknoulcdgemenrsT. his study was supported by a grant of the h b n National Research Council, Special Project "Oncology", contrsct no.86.00310.44. The skillfull technical assistance of Mr. Eorico Radice is gratefully acknowledged. 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