Cancer risk for chemical workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

To describe the long term mortality experience of a cohort of 2187 male chemical production workers previously exposed to substantial levels of dioxin.

Vital status for a previously identified cohort was determined for an additional 10 years, to 1995. Dioxin exposures took place before 1983 and were sufficient to result in chloracne in 245 individuals. Mortality rates were compared with national figures and with a large pool of co-workers in unrelated production jobs.

All cancers combined (standardised mortality ratio (SMR) = 1.0, 95% CI 0.8 to 1.1) and lung cancer (SMR = 0.8, 95% CI 0.6 to 1.1) were at or below expected levels. Rates for soft tissue sarcoma (SMR = 2.4, 95% CI 0.3 to 8.6) and non-Hodgkin's lymphoma (SMR = 1.4, 95% CI 0.6 to 2.7) were greater than expected overall, but below expectation in the update period. No trend of increasing risk with increasing exposure was observed for these cancers. Workers who developed chloracne had very low all-cancer rates (SMR = 0.5, 95% CI 0.3 to 1.0), and lung cancer rates (SMR = 0.3, 95% CI 0.0 to 1.1).

We found no coherent evidence of increased cancer risk from dioxin exposure in this cohort. Our study highlights the wide range of cancer rates and the lack of consistency across dioxin studies.