INGESTED SOIL - BIOAVAILABILITY OF SORBED LEAD, CADMIUM, CESIUM, IODINE, AND MERCURY

Ingestion of soil, inadvertent or otherwise, is an important route of exposure for contaminants that are not geochemically or biologically m obile. There is little known about the bioavailability of these contam inants, especially when the contaminants are sorbed onto native soil p articles. We investigated this with in vitro acid-extraction and enzym olysis experiments and with in vivo single and chronic exposure studie s with mice (Mus musculus). The only anion studied was I-125, and soil in the diet had no effect on the carcass I-125 content. The bioavaila bility of the cations tested decreased in the order of Cs-134 > Hg-203 > Cd-115 = Pb-210, and the effect of soil in the diet on concentratio ns in the carcass decreased in the same order. Soil in the diet signif icantly decreased the bioavailability of Cs-134, by more than fourfold , whereas the effect on Pb-210 was only approximate to 1.1-fold and wa s not significant. The results of the in vitro digestions ordered the elements in the same way as observed in the in vivo analyses. These re sults indicate that for contaminants that are not very mobile and are sorbed onto native soil particles, the presence of soil in the diet do es not markedly affect bioavailability in the gut.