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Dioxins build up primarily in fatty tissues over time (bioaccumulation), so even small exposures may eventually reach dangerous levels. In 1994, the US EPA reported that dioxins are a probable carcinogen, but noted that non-cancer effects (reproduction and sexual development, immune system) may pose a greater threat to human health.
Dioxins are well established carcinogens in animal studies, although the precise mechanism is not clear. Dioxins are not mutagenic or genotoxic. [1] [22] [40] The United States Environmental Protection Agency has categorised dioxin, and the mixture of substances associated with sources of dioxin toxicity as a "likely human carcinogen". [41]
In 2000, the Expert Group of the World Health Organization considered developmental toxicity as the most pertinent risk of dioxins to human beings. [14] Because people are usually exposed simultaneously to several dioxin-like chemicals, a more detailed account is given at dioxins and dioxin-like compounds.
Human exposure to dioxins and DLCs is a cause for public and regulatory concern. [5] Health concerns include endocrine, developmental, immune and carcinogenic effects. [12] The route of exposure is primarily through the ingestion of animal products such as meat, dairy, fish, and human breast milk. [12]
Dioxins break down slowly. It still threatens public health at low levels. Since industry has mostly stopped producing dioxins, one of the largest contributors releasing harmful dioxins left in the United States is waste incineration. Dioxins have been proven to cause cancer, reproductive and developmental issues, and immune system damage.
More human studies on the toxicity of heptachlorodibenzo-p-dioxin are not available. However, animal studies showed non-human toxicity levels: LD 50 rabbit, oral > 5000 mg/kg, LD 50 rat, oral > 5000 mg/kg, [10] and LD 50 guinea pig, oral > 600 ug/kg. [11] Heptachlorodibenzo-p-dioxin is not classifiable as to its carcinogenicity to humans. [12]
Short term exposure to dioxin leads to a condition known as chloracne. [58] Fetuses and infants are very sensitive to dioxin exposure, and can suffer very harmful effects. [58] Mercury. The impact of mercury pollution is extensive in regard to human health.
The Dioxin Reassessment Report refers to the United States Environmental Protection Agency's scientific reassessment of the health effects of exposure to dioxins. It began in April 1991, and in 1994 was published for public review.