Physiologically-relevant bioaccessibility measurements of inorganic contaminants

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There are more than 22,000 contaminated sites in Canada [1], and exposure to soil contaminants poses risks to human health [2]. These risks are traditionally evaluated based on the total concentration of a contaminant in soil taken up from incidental ingestion, but this may overestimate the dose because non-soluble portions move through the digestive system without being absorbed into systemic circulation. In-vivo tests may provide physiologically-relevant data, but are costly and ethically problematic. Instead, bioaccessibility tests measure the portion of a contaminant available for absorption by the human body, and thus provide a physiologically-relevant measurement. When bioaccessibility is factored in, remediation efforts can target areas where risks have been identified. This approach allows for significant cost savings while protecting sensitive environments, which would otherwise be unnecessarily disturbed by overconservative remediation activities. Building on recent advances in this field, we propose to develop bioaccessibility tests that accurately reflect physiological conditions and yield representative results. The long-term goal of this program is to produce fully characterized and physiologically-relevant bioaccessibility data for risk assessors and policy makers to measure exposure to soil contaminants, (e.g. arsenic and new products, such as silver and nickel-alloy nanoparticles). To this end, we will focus on the following short-term objectives: (A) computational fluid dynamic simulations of gastrointestinal mixing parameters. These models will (B) be applied in-vitro to appropriately simulate digestive movement. Expanding on these results, we will (C) investigate the effects of mixed contaminants, such as polycyclic aromatic hydrocarbons (PAHs) on arsenic in soils, and adjust the chemical make-up of bioaccessibility test fluids. Finally, we propose to (D) study transport and epithelial absorption of colloids and small particles using an artificial porous medium, which may enhance the reliability of the data, especially in cases where comparisons with in-vivo results are not available. Ultimately, the vision of this research program is to render in-vivo tests obsolete.This program will train highly qualified engineers (2 PhD, 3 MSc, 5 UG), providing them with rigorous training to develop a solid expertise in the evaluation of risks from contaminated soils. The outcome of this proposed research is directly applicable to protecting human health, and will guide Canadians, environmental regulatory agencies, and risk assessors toward a targeted remediation of identified risk areas, resulting in less intrusive and more cost-effective redevelopment of contaminated sites.