MORTALITY STUDY OF WORKERS IN 1,3-BUTADIENE PRODUCTION UNITS IDENTIFIED FROM A CHEMICAL WORKERS COHORT

The international Agency for Research on Cancer has given the designat ions of sufficient evidence of carcinogenicity of 1,3-butadiene in exp erimental animals and limited evidence of carcinogenic effect in human s. To investigate the carcinogenic effect in humans, we conducted a co hort mortality study amount 364 men who were assigned to any of three 1,3-butadiene production units located within several chemical plants in the Kanawha Valley of West Virginia, including 277 men employed in a U.S. Rubber Reserve Plant which operated during World War II. The bu tadiene production units included in this study were selected from an index developed by the Union Carbide Corporation, which listed for eac h chemical production unit within their South Charleston, West Virgini a and Institute, West Virginia, plants all products, by-products, and reactants. Departments included in the study were those where butadien e was a primary product and neither benzene nor ethylene oxide was pre sent. A total of 185 deaths were observed; the standardized mortality ratio (SMR) for all causes of death was 91, reflecting lower mortality among the study population than the U.S. population. The study found a significantly elevated standarized mortality ratio (SMR) for lymphos arcoma and reticulosarcoma based on four observed cases (SMR - 577; 95 % CI = 157 - 1480), which persisted in an analysis using county refere nt rates. An excess of lymphosarcoma and reticulosarcoma among all wor kers and among workers with routine exposure to 1,3-butadiene was also observed in the only other cohort of 1,3-butadiene production workers previously studied. A statistically nonsignificant excess of stomach cancer was observed in the overall cohort (n = 5; SMR = 243; 95% CI = 79 - 568) that was most pronounced among workers or most pronounced am ong workers employed in the rubber reserve plant for 2 or more years ( n = 5; SMR = 657; CI = 213 - 1530). We conclude that the results of th is study add to the weight of evidence suggesting that butadiene is ca rcinogenic in humans.