Insolubility of Cr2O3 in Bioaccessibility Tests Points to Requirement for a New Human Oral Reference Dose for Trivalent Chromium |
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Authors: | Iris Koch Maeve Moriarty Jie Sui Breanne Gibson Kenneth J. Reimer |
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Affiliation: | 1. Environmental Sciences Group , Royal Military College of Canada , Kingston, ON , Canada;2. Deployable Health Hazard Assessment Team , National Defence , Trenton, ON , Canada |
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Abstract: | Bioaccessibility measurements have the potential to improve the accuracy of risk assessments and reduce the potential costs of remediation when they reveal that the solubility of chemicals in a matrix (e.g., soil) differs markedly from that in the critical toxicity study (i.e., the key study from which a toxicological or toxicity reference value is derived). We aimed to apply this approach to a brownfield site contaminated with chromium, and found that the speciation was CrIII, using a combination of alkaline digestion/diphenylcarbazide complexation and X-ray absorption near edge structure analysis. The bioaccessibility of Cr2O3, the compound on which a reference dose for CrIII is based, was substantially lower (<0.1%) than that of the CrIII in the soils, which was a maximum of 9%, giving relative bioaccessibility values of 13,000% in soil. This shows that the reference dose is based on essentially an insoluble compound, and thus we suggest that other compounds be considered for toxicity testing and derivation of reference dose. Two possibilities are CrCl3·6H2O and KCr(SO4)2·12H2O, which have been used for derivation of ecological toxicity reference values and are soluble at a range of dosing levels in our bioaccessibility tests. |
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Keywords: | trivalent chromium oral reference dose bioaccessibility soil XANES |
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