Chlorinated dibenzo-p-dioxins and -furans: problems in analysis of biomarkers

Although dioxin concentrations in adipose tissue or blood lipids can suitably be used for toxicological evaluation, such data usually are not yet asked for in the risk assessment process, which is still based mainly on theoretical calculations of possible environmental exposure instead of measured concentrations in humans. The latter is necessary because the substantial kinetic differences between experimental animals and humans observed for dioxins lead to different organ concentrations and distribution patterns. Hence the classical extrapolation method for assessing toxicity on the basis of the administered oral dose is inappropriate. Also, the applied models and theoretical assumptions that often predicted a considerable human exposure by the oral, dermal, or inhalatory route in the case of contaminated soil and dust have not proved to be pertinent, since the actual burdens determined by biomonitoring in people living at heavily contaminated sites did not show markedly increased concentrations.