Mortality update of butadiene production workers

Abstract

This is a further update of a cohort mortality study of 2795 male workers employed at least 6 months between 1942 and 1994 at a 1,3-butadiene facility. Earlier reports on this cohort found a statistically significant deficit for all causes of death and lower than expected mortality for most leading causes of death. Prior reports noted an excess of deaths from lymphosarcoma primarily in those employed less than 10 years, first employed before 1946, and employed in jobs with the potential for daily exposure to butadiene (BD). There was a nonsignificant elevation for leukemia in persons potentially exposed to BD on an intermittent basis. The purpose of this update was to examine the patterns of mortality with four additional years of follow-up. Persons who had become eligible since the cohort was last updated through 1990 were also added. A total of 1222 deaths were identified, and death certificates were obtained for all but 20 of the deaths (1.6%). The standardized mortality ratio (SMR) for all causes of death is 88 (95% confidence interval (CI) = 83-93), and for all cancer, the SMR is 92 (95% CI = 82-104). There were 42 deaths from lymphohematopoietic cancers (LHC) with 28.6 expected (SMR = 147, 95% CI = 106-198), 9 observed vs. 4.7 expected deaths for lymphosarcoma (SMR = 191, 95% CI = 87-364), 13 observed vs. 11.5 expected deaths for leukemia (SMR = 113, 95% CI = 60-193), and 15 observed vs. 9.9 expected deaths from cancer of other lymphatic tissue (SMR = 152, 95% CI = 85-250). Subcohort analyses showed that the elevated risk of all LHC and its subcategories was restricted to persons who were first employed before 1950. As an adjunct to the SMR analyses, modeling was done using a qualitative cumulative exposure score as a time-dependent explanatory variable for, (1) all LHC (ICD 200-209); (2) lymphosarcoma (ICD 200); (3) lymphosarcoma and other lymphoma (ICD 200, 202); (4) multiple myeloma (ICD 203); and (5) leukemia (ICD 204-207). The cumulative exposure score was not significantly associated with any of these cancers. Cancer risk was found to increase with age for all of the LHC groups analyzed, except for lymphosarcoma. Similarly, cancer risk was found to increase with age-at-hire for all of the LHC groups except for multiple myeloma.