Refining the risk assessment of metal-contaminated soils

Determining the bioavailability of toxic metals (Pb, As, and Cd) in a diverse range of soils, allows scientifically derived data to dictate site-specific remedies to reduce the risk for sensitive human populations. Based on a series of dosing trials in a juvenile swine model, site-specific estimates of relative bioavailability of Pb in soil ranged from 3% to 86% compared to soluble lead acetate. Another experiment using a pregnant swine model revealed: 1) Pb accumulation in fetal tissues was 50% or more of maternal and; 2) pregnant females accumulated 2-to-4 times more lead in tissues than unbred females. Relative bioavailability results for arsenic- and cadmium-contaminated soils further support the view that soil metals are not always as well absorbed as soluble forms, therefore use of default toxicity factors for assessing human health risk may overestimate the hazard.