Is received dose from ingested soil independent of soil PAH concentrations?—Animal model results

Abstract

19Human exposure to polycyclic aromatic hydrocarbons (PAHs) often occurs through the oral 20 route during hand to mouth transfer of contaminated soils. It is accepted that PAH bioavailability 21 from ingested soils will vary between soils, however, the nature of this variation is not well 22 characterized. Here, we used the juvenile swine model to link external exposure to internal 23 benzo influencing internal exposure of PAHs. We propose four PAH risk assessment options: (i) 34 assume 100% bioavailability, (ii) assume constant internal exposure below 1,900 mg kg -1 , (iii) 35 assume <100%, e.g. 21%, bioavailability below 1,900 mg kg -1 , or (iv) model internal exposure 36 through AUC versus soil characteristic relationships. In our opinion, our data best supports 37 option (ii) because we could not detect an increase in AUC with increasing soil concentrations 38 and our best efforts at (iv) do not robustly predict uptake of different PAHs. 39

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

“…This issue is described more fully in Ruby et al 2016, 12 and is illustrated by a recent PAH bioavailability study where RBA was not measurable in animals using contaminated site soils (BaP up to 300 mg/kg), and only quantifiable in spiked soils containing BaP concentrations in the range of 1000 or 10 000 mg/kg. 16 In contrast, risk-based cleanup goals for carcinogenic PAHs are often 1 ppm or less. As a consequence, RBA measurements are made at PAH concentrations orders of magnitude higher than concentrations for which regulatory decisions must be made.…”

“…However, an important limitation of all is the use of animal models that require PAH concentrations in the 10s of ppm (or higher) to be able to measure bioavailability. This issue is described more fully in Ruby et al 2016, and is illustrated by a recent PAH bioavailability study where RBA was not measurable in animals using contaminated site soils (BaP up to 300 mg/kg), and only quantifiable in spiked soils containing BaP concentrations in the range of 1000 or 10 000 mg/kg . In contrast, risk-based cleanup goals for carcinogenic PAHs are often 1 ppm or less.…”