engleski

Dioxins and Human Toxicity

The term "dioxins" is usually covering polychlorinated dibenzo-dioxins (PCDDs) and polychlorinated dibenzo-furans (PCDFs). It is considered that 2, 3, 7, 8-TCDD has the highest toxic potential and the toxic potentials of other PCDDs and PCDFs are defined in comparison to it. Human exposure to dioxins may happen through environmental (background) exposure or occupational and accidental pollution. Upon entering the human body dioxins are in part metabolized and eliminated, and the rest is stored in body fat. There is certain variability among people and their capacity to eliminate TCDD. TCDD elimination is dose- dependent - at higher exposures elimination rate is much faster than at lower exposures. The liver microsomal P4501A1 enzyme oxygenates lipophilic chemicals such as dioxins. It is encoded by the CYP1A1 gene. Cytosolic aryl hydrocarbon receptor (AhR) mediates their carcinogenic action. It binds to dioxin, translocates to nucleus and together with hydrocarbon nuclear translocator (ARNT) and xenobiotic responsive element (XRE) causes increased expression of CYP1A1. Dioxins are classified as known human carcinogens but they also cause noncancerous effects like atherosclerosis, hypertension, and diabetes, disrupted nervous, immune, reproductive and endocrine system, especially in long-term exposures. Short-term exposure to high levels of dioxins causes damaged liver function and chloracne. The most sensitive population to dioxin exposure are infants, both in prenatal as well as in postnatal period. A large number of health effects have been documented in the scientific literature and they all emphasize dioxins as one of the most toxic chemicals known to men.

dioxins ; exposure ; health effects ; TCDD ; toxicity

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