Comparative bioavailability of the 2,3,7,8 chlorine substituted dioxins and furans from flue ash and flue ash extract in rat liver

Abstract

To determine the bioavailability of PCDD and PCDF, rats were fed a low dose and high dose of a pure flue ash, and a low dose and high dose of a flue ash extract for two weeks. A chemical analysis was performed to obtain the concentrations of the seventeen 2,3,7,8 chlorine substituted dioxins and furans in the flue ash and extract, and in rat liver and carcass. There was a selective retention of the seventeen congeners from the flue ash and extract in rat liver. The results were used to calculate the percentage bioavailability of the congeners from flue ash and extract into rat liver. A principal components analysis of correlation coefficients between individual animals showed no difference in bioavailability for the seventeen congeners, due to dose level. But, bioavailability from the flue ash extract was three times higher then from the pure flue ash, consistent for all seventeen congeners. All figures were comparable with reported outcome from similar studies. It was concluded, that bioavailability of the seventeen 2,3,7,8 chlorine substituted dioxins and furans from a mixture does not depend on the composition of a mixture, nor from the concentrations of the various congeners. On the other hand, bioavailability does depend on physico-chemical properties of the matrix of the mixture. The results indicate, that after an oral exposure to a mixture of dioxins and furans, the internal dose of the seventeen congeners will be higher if they are in an extracted form in the mixture, then when bound to an abiotic matrix. The difference has to be taken into account when making a risk assessment of an oral exposure to a mixture of dioxins and furans.