Bioavailability in the Dog of Benzo(a)pyrene from Contaminated Soil

Abstract

In general, in risk assessment of contaminants from soil and other environmental matrices, bioavailability of the contaminants after ingestion is assumed to equal bioavailability after administration in a solution. However, in the latter case, generally much less complex matrices, such as water, oil or food, are used. To come to a more realistic risk assessment for benzo(a)pyrene (= B(a)P), additional information is required on the influence of the soil matrix on the absolute oral bioavailability of this contaminant. In this report, a study performed in six dogs is presented. The dogs received about 5 mg B(a)P orally or intravenously in a four-way cross-over study design. B(a)P was administered as the intravenous reference dissolved in glycofurol. B(a)P was also given orally, dissolved in olive oil. Furthermore, two types of soil, standard OECD soil and heavily contaminated soil from a dump site (TOP soil), were used in the study. Both types of soil were administered orally with food. Unfortunately, the plasma concentrations were so low that it was not possible to give a reliable estimation of absolute oral bioavailability of B(a)P from one of the matrices. It is very likely that the combination of low doses, low absorption and a high first-pass effect in the liver are the main reason for this observation. It is of great interest to gain insight into the extent of B(a)P entering the body via soil. Future research should however focus on absorption over the intestinal wall rather than on bioavailability in order to rule out effects of the first-pass effect of the liver on plasma concentrations, which is substantial for B(a)P.