The Mortality Experience of Workers Exposed to 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in a Trichlorophenol Process Accident

Epidemiologic studies on dioxin, specifically 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), have not consistently found an increased cancer risk. This study examines mortality rates for 754 employees at a chemical plant after an accident in 1949 in which 122 workers developed chloracne from high exposure to TCDD. We also examined exposure to 4-aminobiphenyl, a potential bladder carcinogen. Although the numbers are small, and confounding factors cannot be ruled out, workers exposed to 4-aminobiphenyl who developed chloracne from the accident had increased mortality rates from soft tissue sarcoma, bladder cancer, and respiratory cancer. All soft tissue sarcomas occurred among workers with potential 4-aminobiphenyl exposure, whereas no soft tissue sarcomas occurred among workers with TCDD exposure alone. In these workers, exposure to TCDD alone at levels great enough to cause chloracne was not associated with increased cancer rates.