Aims:To assess mortality and cancer morbidity in Canadian petroleum workers and explore exposure-response relations for specific petroleum agents.Methods:A total of 25 292 employees hired between 1964 and 1994 were linked to the Canadian tumour registry and national mortality database. Exposure-response trends were assessed for hydrocarbon solvents/fuels, hydrocarbon lubricants, petroleum coke/spent catalyst, and hydrogen sulphide (H2S).Results:External comparison analyses (mortality and incidence) showed deficits for all causes and all malignant neoplasms combined and were consistent with expectation for most malignant and non-malignant sites analysed. Gall bladder cancer mortality was increased among males based on four deaths, but cases had no common job assignments and the increase was focused in workers employed <10 years. Mesothelioma incidence was increased. Most exposure-specific analyses were compromised by small numbers. Statistically significant increases were observed for H2S exposure and a subgroup of accidental deaths as well as for petroleum coke/spent catalyst exposure and lung cancer. While both findings have a degree of biologic plausibility, the H2S association, which exhibited a clearer exposure-response pattern, could be subject to unmeasured confounders. Additionally, interpretation was complicated by the high correlation between hydrocarbon and H2S exposures. With regard to lung cancer, the analysis could not adequately control for smoking, was based on small numbers, and exhibited a tenuous exposure-response pattern.Conclusion:The findings for mesothelioma suggest the need for continued attention to asbestos in the petroleum industry. The relation between accidental deaths and H2S exposure deserves closer scrutiny in similarly exposed populations. Further analyses of lung cancer are underway and will be reported separately.
This paper describes a multistage process to improve the completeness and time-/cost-effectiveness of ascertaining deaths in large employee cohorts. The process uses the vital status data service of the Social Security Administration (SSA) to identify people who can be confirmed as living, in order to reduce the number of records submitted for a National Death Index (NDI) search. The accuracy of SSA results is verified by submitting a sample of known-living and known-deceased people. For the NDI search results, an algorithm based on a discrete combination of matching variables is applied to distinguish NDI records as true, false, or questionable matches to reduce the number of death certificate requests to state offices. Subsequent decision making is based on manual reviews at various stages. In a cohort of over 200,000 employees, an SSA vital status search reduced the size of the NDI death record search by 85%. The algorithm sorted thousands of NDI records into 15 distinct strata and reduced the number of death certificate requests by 76%. The authors believe that the matching process is enhanced by obtaining paper copies of death certificates from the states, because death certificates often provide additional information and aid in determining true matches to company employees.
This study updates mortality rates for 19,075 active and terminated workers at three refinery/petrochemical plants. Mortality rates of the workers were compared with both national and state rates. The results indicated deficits of deaths for all causes, all malignant neoplasms, and respiratory and prostate cancer. The noteworthy finding was a statistically significant increase in leukemia among Louisiana male subjects (standardized mortality ratio [SMR], 181; 95% confidence interval [CI], 122 to 259), which showed suggestive trends of increasing SMRs with increasing tenure. This excess was largely due to increased chronic lymphocytic leukemia (SMR, 351; 95% CI, 168 to 645). The rate of kidney cancer remained elevated among Louisiana male subjects, but this finding was no longer significant, and there were no patterns in SMRs by tenure and latency. Mesothelioma was increased at the Louisiana (SMR, 198; 95% CI, 72 to 430) and Texas (SMR, 246; 95% CI, 99 to 507) locations. The leukemia findings have prompted a study of leukemia incidence at the Louisiana location.
This comprehensive study indicates an overall favorable mortality profile for this workforce. For a few elevations, the study helps guide decisions about future surveillance, focused studies, and other follow-up actions.
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