CANCER MORTALITY IN WORKERS EXPOSED TO PHENOXY HERBICIDES, CHLOROPHENOLS, AND DIOXINS - AN EXPANDED AND UPDATED INTERNATIONAL COHORT STUDY

The authors examined cancer mortality in a historical cohort study of 21,863 male and female workers in 36 cohorts exposed to phenoxy herbic ides, chlorophenols, and dioxins in 12 countries. Subjects in this upd ated and expanded multinational study coordinated by the International Agency for Research on Cancer were followed from 1939 to 1992. Exposu re was reconstructed using job records, company exposure questionnaire s, and serum and adipose tissue dioxin levels. Among workers exposed t o phenoxy herbicides contaminated with 2,3,7,8-tetrachlorodibenzo-p-di oxin (TCDD) or higher chlorinated dioxins, mortality from soft-tissue sarcoma (6 deaths; standardized mortality ratio (SMR) = 2.03, 95% conf idence interval (CI) 0.75-4.43) was higher than expected from national mortality rates. Mortality from all malignant neoplasms (710 deaths; SMR = 1.12, 95% CI 1.04-1.21), non-Hodgkin's lymphoma (24 deaths; SMR = 1.39, 95% CI 0.89-2.06), and lung cancer (225 deaths; SMR = 1.12, 95 % CI 0.98-1.28) was slightly elevated. Risks for all neoplasms, for sa rcomas, and for lymphomas increased with time since first exposure. In workers exposed to phenoxy herbicides with minimal or no contaminatio n by TCDD and higher chlorinated dioxins, mortality from all neoplasms (398 deaths; SMR = 0.96, 95% CI 0.87-1.06), non-Hodgkin's lymphoma (9 deaths; SMR = 1.00), and lung cancer (148 deaths; SMR = 1.03) was sim ilar to that expected, and mortality from soft-tissue sarcoma was slig htly elevated (2 deaths; SMR = 1.35). In a Poisson regression analysis , workers exposed to TCDD or higher chlorinated dioxins had an increas ed risk for all neoplasms (rate ratio = 1.29, 95% CI 0.94-1.76) compar ed with workers from the same cohort exposed to phenoxy herbicides and chlorophenols but with minimal or no exposure to TCDD and higher chlo rinated dioxins. These findings indicate that exposure to herbicides c ontaminated with TCDD and higher chlorinated dioxins may be associated with a small increase in overall cancer risk and in risk for specific cancers.