Bioaccessibility of mercury from traditional northern country foods measured using an in vitro gastrointestinal model is independent of mercury concentration

Human health risk assessment of dietary mercury (Hg) exposure in Canada assumes that all Hg from fish consumption is in the form of methylmercury (MeHg), the more bioavailable and hazardous form of Hg. In contrast, the risk assessment of dietary Hg to Inuit in northern Canada assumes that no more than two-thirds of dietary Hg is MeHg since mammal organs consumed by Inuit contain substantial concentrations of inorganic Hg. In vitro gastrointestinal models (e.g., the Simulator of the Human Intestinal Microbial Ecosystem) are often used for the evaluation of soil contaminant bioaccessibility, i.e., the fraction solubilized into gastrointestinal fluids, for use in site-specific human health risk assessment. In this research, we digested northern country foods using the SHIME for the measurement of Hg bioaccessibility, a novel approach for the assessment of dietary Hg bioavailability. We demonstrated that small intestinal Hg bioaccessibility from 16 fish. wild game, and marine mammal samples consumed by Inuit in northern Canada ranged between 1 and 93% and was independent of food HgT (MeHg + Hg-II) concentration. Additionally, we demonstrated that gastrointestinal microbes may affect Hg bioaccessibility of the 16 country foods, either increasing or decreasing bioaccessibility depending upon the type of food. These results indicate that gastrointestinal absorption of Hg is not likely limited by the concentration of Hg in the food, which is in agreement with in vivo Hg bioavailability studies. Furthermore, these in vitro results support the hypothesis that the gastrointestinal absorption of Hg from Inuit country foods is dependent upon food type. (C) 2009 Elsevier B.V. All rights reserved.