Update of the mortality experience of employees with occupational exposure to 1,2-dibromo-3-chloropropane (DBCP)

DBCP (1,2-dibromo-3-chloropropane), a nematocide, was used in the United States from the mid-1950s until 1977. The U.S. Environmental Protection Agency (EPA) restricted and eventually banned its use after the 1977 discovery of DBCP-induced sterility in production workers. The present study is an update of the mortality (1957-1989) experience of a cohort of 548 male employees who had potential for exposure in the production and formulation of DBCP. While adjusting for age, calendar-year, and pay status of all other Midland-area Dow Chemical male employees, there were 68 total observed deaths in the cohort compared to 72.1 expected (Mantel Haenszel Relative Risk 0.9, 95% Confidence Interval 0.7-1.2) and 19 deaths from all malignancies compared to 19.0 expected (RR 1.0, 95% CI 0.6-1.6). Of the a priori anatomic cancer sites of interest, there were no deaths from stomach, liver, kidney, testes, or nasal cavity cancers. Altogether, there were 7 deaths from lung cancer compared to 6.6 expected (RR 1.1, 95% CI 0.5-2.3). Among the 81 employees with exposure categorized as direct for 1 or more years, there were 3 observed lung cancer deaths compared to 0.9 expected (RR 3.3, 95% CI 1.1-9.6). Smoking was a confounding factor in the interpretation of this observation. Although the present analysis nearly doubled the number of person-years from the original study, the conclusions remain limited by the cohort's size and duration of follow-up.