To further investigate the mortality risk of employees who worked in the petroleum refinery industry, we updated an earlier investigation by extending the mortality follow-up by an additional 14 years through 2003.
The cohort consisted of 10,621 employees with an average follow-up of 34 years. We used the standardized mortality ratio (SMR) adjusted for age, race, and calendar years as a measure of risk.
Overall mortality (SMR = 0.77, 95% confidence interval [CI], 0.74–0.79), all cancer mortality (SMR = 0.87, 95% CI = 0.82–0.93), and most cause-specific mortalities for the total study population were lower than or similar to that of the population of Harris County, Texas. This study did not show a significant increase in leukemia in the total population or in any of the subgroups. The only statistically significant excess of mortality found in this study was an increase in mesothelioma among maintenance employees; the SMR was 4.78 (95% CI = 2.54–8.17) among employees who worked for a minimum of one year and was 7.51 (95% CI = 3.75–13.45) among those with 10 or more years of employment and 20 or more years of latency.
After more than half a century of follow-up, employees at this facility continue to show more favorable mortality outcomes than the general local population. Overall, no statistically significant increase of leukemia or of any of the specific cell types was found. The increased mesothelioma is likely related to past exposure to asbestos.
From Shell Health Services, Shell Oil Company, Houston, TX.
Address correspondence to: Shan P. Tsai, PhD, Shell Health Services, Shell Oil Company, One Shell Plaza, P.O. Box 2463, Houston, TX 77252-2463; E-mail: firstname.lastname@example.org.