Relative Effect Potency Estimates of Dioxin-like Activity for Dioxins, Furans, and Dioxin-like PCBs in Adults Based on Two Thyroid Outcomes.

Slovak Medical University, Bratislava, Slovakia.
Environmental Health Perspectives (Impact Factor: 7.26). 05/2013; DOI: 10.1289/ehp.1205739
Source: PubMed

ABSTRACT BACKGROUND: Toxic Equivalency Factors (TEFs) are an important component in the risk assessment of dioxin-like human exposures. At present, this concept is mainly based on in vivo animal experiments with oral dosage. Consequently, the present human TEFs derived from mammalian experiments are only applicable for exposure situations in which oral ingestion occurs. Nevertheless, these "intake" TEFs are commonly, but incorrectly used by regulatory authorities to calculate "systemic" Toxic Equivalents (TEQs) based on human blood and tissue concentrations and consequently considered to be biomarkers for either exposure or effect. OBJECTIVES: To determine relative effect potencies (REPs) for systemic human concentrations of dioxin-like mixture components using thyroid volume or FT4 serum concentration as the outcomes of interest. METHODS: We compared the strength of association between each dioxin-like compound and thyroid endpoints in 320 adults residing in an area of eastern Slovakia polluted by organochlorines using a benchmark concentration and regression-based approach. RESULTS: REPs calculated from thyroid volume and FT4 were similar. The regression slope derived REP data from thyroid volume and FT4 level correlated with the WHO TEF values (Spearman r=0.69, p=0.01 and r=0.62, p=0.03, respectively). The calculated REPs were mostly within the minimum and maximum values for in vivo REPs derived by other investigators. CONCLUSIONS: Our REPs calculated from thyroid endpoints realistically reflect human exposure scenarios as they are based on chronic, low dose human exposures and on biomarkers reflecting body burden. Compared to previous results they suggest higher sensitivity to the effects of dioxin-like compounds.

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