Cancer incidence in Swedish oil refinery workers exposed to benzene.

BACKGROUND: Oil refinery workers are exposed to benzene, which is a well-known cause of leukaemia, but results on leukaemia in oil refinery workers have been mixed, and the data on workers' exposure is limited. Oil refinery workers are also exposed to asbestos and several studies have shown increased risk of mesothelioma. AIM: The objective was to investigate cancer incidence, especially leukaemia, at low to moderate exposure to benzene in an update of a previous study of employees at three Swedish oil refineries. METHODS: Cancer incidence was followed up in 2264 men (1548 refinery operators) employed at three oil refineries in Sweden for at least one year. Job types and employment times were collected from complete company files. A retrospective assessment of the benzene exposure was performed by occupational hygienists in collaboration with the refineries using historic measurements as well as detailed information on changes in the industrial hygiene and technological developments. Cases of cancer were retrieved by a linkage with the Swedish Cancer Register through 35-47 years of follow-up and standardized incidence ratios (SIR) with 95% confidence intervals (CI) were calculated. RESULTS: In total, 258 tumors had occurred versus 240 expected (SIR 1.07; 95% CI 0.95-1.21). There were 10 cases of leukaemia, all in refinery operators (SIR 2.4; 95% CI 1.18-4.51). There were three cases of pleural mesothelioma, two of which in refinery operators. The mean estimated cumulative benzene exposure for the cases of leukaemia was 7.9 ppm-years (median 4.9, range 0.1-31.1). DISCUSSION: The study suggests that low to moderate average cumulative benzene exposure increases the risk of leukaemia. Limitations include the modest number of cases and potential misclassification of exposure. CONCLUSION: The present study indicated an increased risk of leukaemia in male oil refinery workers with low to moderate exposure to benzene.

Genotoxic effects in workers exposed to low levels of benzene from gasoline.

To study genotoxic effects of exposure to low levels of benzene, single-strand breaks (SSB) in DNA of leukocytes and urinary levels of the oxidative DNA adduct 8-hydroxydeoxyguanosine (8OHdG) were determined in 33 men occupationally exposed to benzene from gasoline and in 33 controls. The average exposure to benzene over a shift was determined by personal air sampling in the breathing zone. The 8-hr time-weighted average exposure to benzene was 0.13 ppm (mean value, range 0.003-0.6 ppm). Exposed workers had a significant increase of SSB (p = 0.04) over the shift compared with controls. Storage time of the samples seemed to affect the results. An analysis of samples with the same storage time showed a nonsignificant increase among the workers compared with controls. Urinary 8OHdG increased over the shift among the exposed workers but not among the controls. The highest values among the exposed workers were seen in late evening, with a slight decrease the next morning. Multiple linear analysis adjusting for smoking habits showed a significant association between the exposure level of benzene during the shift and the increase of 8OHdG in the urine over the shift among exposed workers (p = 0.02). These findings indicate a genotoxic effect in humans of benzene at relatively low exposure levels, that is, about 0.1 ppm (0.3 mg/m3).

Leukaemia, lymphoma, and multiple myeloma in seamen on tankers.

OBJECTIVES: To investigate the risk of lymphatic and haematopoietic malignancies in deck crew on tankers exposed to cargo vapours. METHODS: The study design was as a nested case-referent study in two cohorts of male Swedish seamen 20-64 years of age at the national census 1960 (n 13,449) and 1970 (n 11,290), respectively. Cases were detected by record linkage with the Swedish Cancer Register 1961-79 and 1971-87, respectively. For each case, three to five age matched referents from the population were selected. Exposure was assessed from data in the Swedish Registry of Seamen and from a register of Swedish ships. RESULTS: Seamen in the 1970 cohort, who had been exposed to cargo vapours for at least one month on chemical or product tankers, had an increased risk of lymphatic and haematopoietic malignancies (Mantel-Haenszel odds ratio (OR) 2.6, 95% confidence interval (95% CI) 1.1 to 5.9)) with a significant exposure-response relation (conditional logistic regression analysis, p = 0.04). The ORs were increased for both lymphoma (3.2), multiple myeloma (4.0), and leukaemia (1.6), but the increase was only significant for non-Hodgkin's lymphoma (OR 3.3, 95% CI 1.1 to 10.6). There were no significantly increased risks for the 1960 cohort or for seamen exposed only on crude oil tankers, but these groups had few exposed cases and low cumulative exposure to benzene and other light petroleum products. CONCLUSIONS: Seamen exposed to cargo vapours from gasoline and other light petroleum products on chemical or product tankers had an increased incidence of lymphatic and haematopoietic malignancies. One possible cause is exposure to benzene during loading, unloading, and tank cleaning operations.

Acute nonlymphatic leukemia among deck officers on coastal tankers: a report of two cases.

Deck officers on coastal tankers may be exposed to high concentrations of cargo vapors during loading and tank-cleaning operations. Two cases of acute nonlymphatic leukemia are described. Both men had worked as chief officers on coastal tankers transporting benzene and other petroleum products.