Oral Bioaccessibility of Trivalent and Hexavalent Chromium in Soil by Simulated Gastric Fluid

Abstract

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

Metal Contamination of Soils and Prospects of Phytoremediation in and Around River Yamuna: A Case Study from North-Central India

“…The same was observed in the case of Zn and Co with Organic matter. Phosphate is able to increase water-soluble lead forms from contaminated soils by 56.8-100% [61]. This is clearly shown by the phosphate values (Table 2) obtained for different samples with maximum in zone 2 followed by zone 1 which probably led to higher Pb values in zones 1 and 2 ( Mean concentrations of heavy metals in soils at the sites studied were compared with threshold values of soil suggested by the Canadian Environmental Quality Guidelines [58].…”

Bioaccessibility Extractions for Contaminant Risk Assessment

“…Few studies report on the following applications: cobalt and tungsten in powders used in the manufacture of cemented tungsten carbides, 102 cobalt compounds (provided by the Cobalt Development Institute), 103 platinum group elements in particulates from catalytic converters, 104 chromium species in spiked soils and commercially available enriched yeast, [105][106][107][108] and antimony in soil. 71 Organic contaminants have most frequently been tested in soils, with PCBs, PAHs, and, to a lesser extent, PCDD/Fs being targeted most frequently.…”

SBAT: A Tool for Estimating Metal Bioaccessibility in Soils

“…These results are consistent with observations in Stewart et al (2003) that showed that Cr(III) bioaccessibility was limited in systems with high levels of inorganic and organic carbon. Skowronski et al (2001) also noted that Cr(III) bioaccessibility was lower on an organic-rich sandy soil vs. a clay soil that had significantly less organic carbon. In the Cr(VI) system, the two A-horizon soils and the Melton Valley B-horizon (MV-B) showed statistically significant lower Cr bioaccessibility than WB-B for all treatment concentrations and aging times.…”

“…The exposure pathway of concern is usually the ingestion of contaminated soil, especially by children who traditionally have greater handto-mouth contact (Paustenbach, 1989;Skowronski et al, 2001). U.S. EPA soil action levels for Cr(III) and Cr(VI) are 78,000 and 390 mg/kg, respectively, which are protective of soil-ingestion exposures for children in residential sites.…”

“…Thus, the bioaccessibility of Cr(VI) was significantly influenced by the reduction of Cr(VI) to Cr(III). Skowronski et al (2001) also suggested that Cr(VI) bioaccessibility in their soils was influenced by oxidationreduction processes. In order for reduction to occur, there needs to be a source of electrons.…”