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Environmental Medicine: Integrating a Missing Element into Medical Education
(3) Assuming the utility company mentioned in the case study sprayed the area with a dioxin-containing herbicide, when will it be safe for the children to return to the area to play?
❑ Only two effects of dioxin exposure have been confirmed in humans: chloracne and transient mild hepatotoxicity.
Dioxins are very toxic to some animal species, but the evidence for corresponding toxicity in humans has not been established. No deaths due to systemic dioxin toxicity in humans have been reported. Only two clinical effects have been repeatedly observed in exposed populations: chloracne and transient hepatic effects. Soft-tissue sarcomas, lymphomas, peripheral neuropathy, birth defects, and reproductive effects have been studied but remain unconfirmed. Because human dioxin exposure always involves mixed exposures, the specific effects of dioxin are difficult to ascertain.
In some animals, TCDD is a potent carcinogen and causes reproductive effects and birth defects. TCDD’s toxicity also appears in animals as pathologic effects in the liver, peripheral nerves, hematopoietic and reticuloendothelial systems, and skin. Acute toxicity develops after a latent period of 7 to 10 days, after which the animals experience a rapid wasting syndrome not seen in humans.
Dermatologic Effects
❑ Chloracne is a hallmark of dioxin toxicity in humans and can persist for years after exposure ceases.
Acneform lesions may appear as early as 1 to 3 weeks after dioxin exposure. The lesions are small, pale yellow cysts, which arise from altered differentiation of acinar sebaceous basal cells into keratinocytes. The lesions primarily involve the face, especially the periorbital, temporal, and malar areas, as well as the upper body. Most cases of chloracne resolve in 1 to 3 years; one case has been reported to persist for as long as 32 years. Although TCDD is one of the most potent acne-producing agents, chloracne can also be
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