Effects of Source and Concentration on Relative Oral Bioavailability of Benzo(a)pyrene from Soil

The objective of this study was to examine the influence of soil composition, PAH concentration, and source material type on PAH bioavailability using an approach capable of measuring uptake at low, environmentally relevant PAH concentrations (down to 1 ppm). Contaminated soil samples were constructed using PAHs from three source materials-solvent, soot, and fuel oil-to which ³H-benzo(a)pyrene (³H-BaP; total BaP concentrations of 1, 10, and 100 ppm) was added in a mixture of PAHs. The soils were weathered for 8 weeks using weekly wet-dry cycles. Each soil was administered as a single dose to rats, and blood samples were taken over 6 days. Relative oral bioavailability (RBA) of the BaP from soil was estimated by comparing the area under the curve (AUC) for ³H concentration versus time in blood with the AUC observed from the same PAH mixture dosed in a food matrix. The extent to which BaP RBA was diminished in soil versus food varied among the source materials, but little or no difference was observed among the soil types examined unless carbon amendments were added. These results suggest that the type of PAH source material can have a strong influence on PAH oral bioavailability.