Comparison of Methodologies to Estimate Intake Dose for Exposure to Soil Contaminants

It has been suggested that probabilistic approaches would provide more realistic estimates for human intake dose from exposure to soil contaminants than the commonly-used standard deterministic method. The objective of this study was to compare intake dose estimated by these methods for noncarcinogens and carcinogens in soil from 21 contaminated sites in Pennsylvania, USA. Intake doses by the principal human exposure routes for these contaminants were estimated by the standard deterministic method using fixed input parameter values, and by two emergent probabilistic methods. The probabilistic methods were based (a) on distribution functions for all input parameters, or (b) on some combination of these functions and fixed parameter values. Intake doses were then taken as the 90th, 95th, or 99.9th percentile of the generated cumulative output distribution and compared with the commonly-used deterministic estimates over all contaminant/site combinations. For all exposure routes, the 90th and 95th percentile intake dose estimates were not markedly different from the deterministic values or from each other. The opposite was generally the case for the 99.9th percentile estimates. These results did not indicate clear and definitive advantages in using probabilistic methods over the deterministic method for estimating human intake dose from exposure to soil contaminants.