Oral bioaccessibility of trivalent and hexavalent chromium in soil by simulated gastric fluid

Chromium is found in soil from natural sources and anthropogenic activities . The ingestion of soil contaminated with chromium especially by children c an have toxic consequences. Therefore, it is important to quantify the oral bioaccessibility of chromium in contaminated soil, In this study, chromium -51 as chromic(III) chloride and sodium chromate(VI), was mixed with an Ats ion sandy soil and a Keyport clay soil and stored for 4 mo at either 21-25 degreesC or 2-4 degreesC. Utilizing simulated gastric conditions, the oral bioaccessibility of chromium in soil was determined. When the effects of so il on the bioaccessibility of chromium were compared, the data revealed tha t the bioaccessibility of chromium(III) from the clay soil was significantl y lower than from the sandy soil at 21-25 degreesC. However, at 2-4 degrees C, more chromium(III) was extracted by synthetic gastric fluid from the cla y soil than from the sandy soil. Temperature was also a factor as evidenced by the higher bioaccessibility of chromium(VI) in the sandy soil at 2-4 de greesC and of both chromium species in the clay soil at the same temperatur e. Reduction of the soluble chromium(VI) chemical to the nonsoluble chromiu m(III) compound in the acidic soils by naturally occurring organic matter i n soil would explain the lower bioaccessibility of chromium(VI) at 21-25 de greesC. At 2-4 degreesC, the data indicate that the rate of chromium(VI) re duction to chromium(III) was slowed. Although the results of this study are limited to one low concentration of chromium(III) and chromium(VI) and ind icate that the bioaccessibility of chromium in soil can range between 18% a nd 72%, the data also suggest that there may be a potential health hazard f rom oral exposure to chromium in heavily contaminated sites. Therefore, mor e extensive research should be conducted to determine if these findings can be extended to environmentally relevant concentrations.