Laird Brian D, Van de Wiele Tom R, Corriveau Madeleine C, Jamieson Heather E, Parsons Michael B, Verstraete Willy, Siciliano Steven D
Graduate Program in Toxicology, University of Saskatchewan, Saskatoon, SK, Canada.
Environ Sci Technol. 2007 Aug 1;41(15):5542-7. doi: 10.1021/es062410e.
It is widely accepted that the use of total metal concentrations in soil overestimates metal risk from human ingestion of contaminated soils. In vitro simulators have been used to estimate the fraction of arsenic present in soil that is bioaccessible in the human digestive track. These approaches assume that the bioaccessible fraction remains constant across soil total metal concentrations and that intestinal microbiota do not contribute to arsenic release. Here, we evaluate both of these assumptions in two size fractions (bulk and <38 microm) of arsenic-rich mine tailings from the Goldenville, Lower Seal Harbour, and Montague Gold Districts, Nova Scotia. These samples were evaluated using an in vitro gastrointestinal model, the Simulator of the Human Intestinal Ecosystem (SHIME). Arsenic bioaccessibility, which ranged between 2 and 20% in the small intestine and 4 and 70% in the colon, was inversely related to total arsenic concentration in the mine tailings. Additionally, arsenic bioaccessibility was greater in the bulk fraction than in the <38 microm fraction in the small intestine and colon while colon microbes increased the bioaccessibility of arsenic in mine tailings. These results suggest that the practice of using a constant percent arsenic bioaccessibility across all metal concentrations in risk assessment should be revisited.
人们普遍认为，使用土壤中的总金属浓度会高估人类摄入受污染土壤所带来的金属风险。体外模拟器已被用于估计土壤中可被人体消化系统生物利用的砷的比例。这些方法假定生物可利用部分在土壤总金属浓度范围内保持恒定，并且肠道微生物群对砷的释放没有影响。在此，我们评估了新斯科舍省戈尔登维尔、下海豹港和蒙塔古金矿区富含砷的尾矿两个粒度级分（粗粒和<38微米）中的这两个假设。使用体外胃肠模型——人类肠道生态系统模拟器（SHIME）对这些样品进行了评估。砷的生物可利用性在小肠中为2%至20%，在结肠中为4%至70%，与尾矿中的总砷浓度呈负相关。此外，在小肠和结肠中，粗粒级分中的砷生物可利用性高于<38微米级分，而结肠微生物增加了尾矿中砷的生物可利用性。这些结果表明，在风险评估中对所有金属浓度使用恒定百分比的砷生物可利用性的做法应重新审视。
