2ND FOLLOW-UP OF A DUTCH COHORT OCCUPATIONALLY EXPOSED TO PHENOXY HERBICIDES, CHLOROPHENOLS, AND CONTAMINANTS

A retrospective cohort study of workers exposed to phenoxy herbicides, chlorophenols, and contaminants (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other polychlorinated dioxins and furans) has been conducte d in a chemical factory in the Netherlands. Male workers exposed to ph enoxy herbicides or chlorophenols showed increased relative risks (adj usted for age, calendar period at end of follow-up, and time since fir st exposure/employment) for total mortality (relative risk (RR) = 1.8, 95% confidence interval (CI) 1.2-2.5), cancer mortality (RR = 4.1, 95 % CI 1.8-9.0), respiratory cancer (RR = 7.5, 95% CI 1.0-56.1), non-Hod gkin's lymphoma (RR = 1.7, 95% CI 0.2-16.5), and ischemic heart diseas es (RR = 1.8, 95% CI 0.9-3.6) compared with an internal referent group of nonexposed workers. By using TCDD levels (predicted at the time of maximum exposure), based on extrapolated TCDD levels that were measur ed in a subset of the cohort, estimated relative risks for workers wit h medium and high TCDD levels were comparable with risks derived from the simple and earlier applied dichotomous exposure classification. In general, relative risks were highest in the highest category, indicat ing exposure-related increases in risk with TCDD level. In conclusion, results of this cohort study support the evidence of a high cancer ri sk in workers exposed to phenoxy herbicides, chlorophenols, and contam inants.