Current intelligence bulletin 40 - 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD, "dioxin") (with reference package).
Hazards associated with exposure to 2,3,7,8-tetrachlorodibenzo-p- dioxin (1746016) (TCDD) are presented, and recommendations relating to its classification as a potential occupational carcinogen are given. TCDD occurs as a contaminant in phenoxyacetic acid herbicides and as a combustion product of these and of polychlorinated biphenyls. Exposure can occur during production or use of these chemicals, from contaminated waste materials, or from transformer fire contamination. Toxicity in experimental animals includes hematologic, reproductive, and immunologic effects, as well as carcinogenic activity. Male and female rats and mice have developed a variety of cancers following long term oral or skin exposure. Effects in human populations have been difficult to assess due to concomitant exposures and lack of accurate exposure data. Chloracne and symptoms of systemic poisoning, such as gastrointestinal disturbances and metabolic disorders, have been seen with exposure to TCDD and other halogenated aromatic chemicals. No clear human reproductive effects have been seen, although there have been reports of increased spontaneous abortion rates or congenital malformations, especially of the spine. Various mortality studies have provided limited evidence of human carcinogenicity when exposure has included TCDD. The most significant data indicate an excess of lymphoma and stomach cancer associated with exposure to TCDD in phenoxyacetic herbicides. It is concluded that TCDD should be treated as a potential occupational carcinogen. Recommendations include assessment of worker exposure through environmental sampling of workplaces, decontamination procedures for equipment and personnel, protective clothing, respiratory protection, and follow up analysis and sampling of areas and equipment following decontamination.