title: Gastrointestinal microbes increase arsenic bioaccessibility of ingested mine tailings using the simulator of the human intestinal microbial ecosystem.
abstract: 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.
authors.affiliation: Graduate Program in Toxicology, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Laird
authors.forename: Tom R
authors.initials: TR
authors.lastname: Van de Wiele
authors.forename: Madeleine C
authors.initials: MC
authors.lastname: Corriveau
authors.forename: Heather E
authors.initials: HE
authors.lastname: Jamieson
authors.forename: Michael B
authors.initials: MB
authors.lastname: Parsons
authors.forename: Willy
authors.initials: W
authors.lastname: Verstraete
authors.forename: Steven D
authors.initials: SD
authors.lastname: Siciliano
mesh_terms: D001151:Arsenic / Q000378:metabolism*; D001682:Biological Availability; D003106:Colon / Q000378:metabolism; D004435:Eating; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006801:Humans; D007421:Intestine, Small / Q000378:metabolism; D008906:Mining; D008954:Models, Biological; D010316:Particle Size; D012989:Soil Pollutants / Q000378:metabolism*