In vivo measurement, in vitro estimation and fugacity prediction of PAH bioavailability in post-remediated creosote-contaminated soil

- Low PAH bioavailability in remediated creosote soil limited further biodegradation.
- However residual PAHs were highly bioavailable when assessed using an in vivo model.
- In vitro PAH bioaccessibility underestimated in vivo PAH bioavailability.
- Fugacity modelling underestimated in vivo PAH bioavailability.
- These results impact exposure and risk calculations for incidental soil ingestion.

In this study, PAH bioavailability was assessed in creosote-contaminated soil following bioremediation in order to determine potential human health exposure to residual PAHs from incidental soil ingestion. Following 1000 days of enhanced natural attenuation (ENA), a residual PAH concentration of 871 ± 8 mg kg− 1 (∑ 16 USEPA priority PAHs in the < 250 μm soil particle size fraction) was present in the soil. However, when bioavailability was assessed to elucidate potential human exposure using an in vivo mouse model, the upper-bound estimates of PAH absolute bioavailability were in excess of 65% irrespective of the molecular weight of the PAH. These results indicate that a significant proportion of the residual PAH fraction following ENA may be available for absorption following soil ingestion. In contrast, when PAH bioavailability was estimated/predicted using an in vitro surrogate assay (FOREhST assay) and fugacity modelling, PAH bioavailability was up to 2000 times lower compared to measured in vivo values depending on the methodology used.