Health Effects in Humans
Dioxins build up primarily in fatty tissues over time (bioaccumulate), 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. TCDD, the most toxic of the dibenzodioxins, is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). TCDD has a half-life of approximately 8 years in humans, although at high concentrations, the elimination rate is enhanced by metabolism. The health effects of dioxins are mediated by their action on a cellular receptor, the aryl hydrocarbon receptor (AhR).
Exposure to high levels of dioxins in humans causes a severe form of persistent acne, known as chloracne. High occupational or accidental levels of exposures to dioxins have been shown by epidemiological studies to lead to an increased risk of tumors at all sites. Other effects in humans (at high dose levels) may include:
- Developmental abnormalities in the enamel of children's teeth.
- Central and peripheral nervous system pathology
- Thyroid disorders
- Damage to the immune systems
- Endometriosis
- Diabetes
Recent studies have shown that high exposure to dioxins changes the ratio of male to female births among a population such that more females are born than males.
Dioxins accumulate in food chains in a fashion similar to other chlorinated compounds (bioaccumulation). This means that even small concentrations in contaminated water can be concentrated up a food chain to dangerous levels because of the long biological half life and low water solubility of dioxins.
Read more about this topic: Polychlorinated Dibenzodioxins
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