Cancer Incidence in Swedish Oil Refinery Workers

Abstract

BackgroundOil 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.AimThe objective was to investigate cancer incidence, especially leukaemia, at low to moderate exposure to benzene in employees at three Swedish oil refineries.MethodsCancer 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 rates (SIR) with 95% confidence intervals (CI) were calculated.ResultsIn 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 cumulative benzene exposure increases the risk of leukaemia.ConclusionThe present study in Swedish oil refinery workers showed increased risk of leukaemia, likely caused by low to moderate exposure to benzene.

Note:
Funding declaration: This research was supported by the Swedish Research Council FAS (nr 2007-0503).

Conflict of Interests: None.

Ethical Approval: The study was approved by the Ethics Review Board of the University of Gothenburg, Sweden (document number dnr 212-07).

Keywords: Leukaemia, Benzene, Oil refinery, Retrospective exposure assessment