Updated epidemiological study of workers at two California petroleum refineries, 1950–95

Abstract

Objectives: To further assess the potential role of occupational exposures on mortality, a second update of a cohort study of workers at two petroleum refineries in California was undertaken. Methods: Mortality analyses were based on standardised mortality ratios (SMRs) and 95% confidence intervals (95% CIs) using the general population of California as a reference. Additional analyses of lymphatic and haematopoietic cancer deaths and diseases related to asbestos were undertaken. Results: The update consisted of 18 512 employees, who contributed 456 425 person-years of observation between 1950 and 1995. Both overall mortality and total cancer mortality were significantly lower than expected, as were several site specific cancers and non-malignant diseases. In particular, no significant increases were reported for leukaemia cell types or non-Hodgkin's lymphoma. Mortality excess from multiple myeloma was marginally significant. The excess was confined to employees enrolled before 1949. Furthermore, there was no significant upward trend based on duration of employment, which argues against a causal interpretation relative to employment or exposures at the refineries. No increase was found for diseases related to asbestos: pulmonary fibrosis; lung cancer; or malignant mesothelioma. There was no significant increase in mortality from any other cancers or nonmalignant diseases. Conclusion: This second update provides additional reassurance that employment at these two refineries is not associated with increased risk of mortality.

Increased risk of acute myelogenous leukemia and multiple myeloma in a historical cohort of upstream petroleum workers exposed to crude oil

“…In our study, the median time between the first year of registered engagement and diagnosis of acute myelogenous leukemia and multiple myeloma for cases in the job category ''upstream operators offshore'' included into the cohort prior to 1986 was 6 (range 5-21) and 18 (range [13][14][15][16][17][18][19][20] years, respectively. This is compatible with a longer latency in multiple myeloma, but the rather short follow-up time together with the low number of cases, limit the possibility of a powerful discussion on the latency issue based on our data.…”

“…A marked limitation of the earlier studies in the petroleum industry is the likely presence of a healthy worker effect due to an overall mortality and overall cancer incidence among these workers that are significantly lower than in the general population used as a reference [12,13,22]. The healthy worker effect might mask increased risks of both multiple myeloma and non-Hodgkin lymphoma even in studies capable of showing an increased risk of acute myelogenous leukemia.…”

“…Studies of petroleum workers have shown an association between benzene exposure and leukemia [9][10][11][12]. Some studies of petroleum workers have found an elevated risk of multiple myeloma [13][14][15], while others have not [9,12,16]. Further, although a relation between non-Hodgkin lymphoma and benzene exposure has been suggested [7,8], most studies in the petroleum industry have not found any increased risk [5,17].…”

Multiple myeloma: A review of the epidemiologic literature

“…143-150 A significant excess of multiple myeloma mortality (SMR 5 1.64, 95% CI: 1.03-2.48) was reported in California petroleum workers enrolled before 1949, 151 however, and in Canadian petroleum workers in marketing or distribution (SMR 5 1.94, 95% CI: 1.11-3.15). 148 In a cohort of petroleum workers exposed to gasoline, Wong et al 152 observed a nonsignificant inverse association (SMR 5 0.79, 95% CI: 0.46-1.24) based on 17 observed cases.…”

The non-Hodgkin lymphomas: A review of the epidemiologic literature

“…Relative risks have been near unity in petroleum worker cohort studies in California, 177,178 Texas, [179][180][181] Louisiana, 182,183 US, [184][185][186] Canada 187,188 and Australia. 189 Inconsistent nonsignificant associations were found in an updated (1970-1997) mortality cohort study of 2 refinery/petrochemical plants (SMR for Baton Rouge facility 5 1.47, 95% CI: 0.98-2.11; SMR for Baytown facility 5 0.84, 95% CI: 0.47-1.39).…”