Health effects and risk assessment of halogenated aromatic hydrocarbons
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abstract
Polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) are industrial chemicals or by-products of industrial processes and combustion. These compounds are highly stable and lipophilic and have been identified as contaminants in almost every component of the global ecosystem including air, water, sediments, fish, wildlife, diverse food products, and human adipose tissue, serum and milk. Human exposure to relatively high levels of these compounds has been associated with multiple adverse health effects including chloracne, hepatic dysfunction, and porphyria and there is evidence in some studies of an increased risk for specific cancers. Adverse health effects associated with dietary exposure to relatively low levels of PCBs, PCDDs, and PCDFs are unknown however results of some correlational studies suggest that in utero or early postnatal exposure may lead to neurodevelopmental deficits in children. Humans are invariably exposed to complex mixtures of halogenated aromatic hydrocarbons (HAHs) and hazard and risk assessment has utilized a toxic equivalency factor (TEF) approach. The toxic equivalents (TEQs) of any mixture are equal to the sum of the concentration of individual (i) congeners times their potencies (TEF(i)) relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, TEF = 1.0). TEQ = [PCDD(i)] x TEF(i) + [PCDF(i)] x TEF(i) + [PCB(i)] x TEF(i) The TEQ (or TCDD equivalents) can be readily calculated from analytical data and provides an estimate of the toxicity of any mixture containing HAHs.
