Physiologically-relevant bioaccessibility measurements of inorganic contaminants

加拿大有22 000多个受污染的场地[b]，接触土壤污染物对人类健康构成风险[b]。这些风险传统上是根据偶然摄入的土壤中污染物的总浓度来评估的，但这可能高估了剂量，因为不溶性部分通过消化系统而没有被吸收到体循环中。体内试验可能提供与生理相关的数据，但成本高昂且存在伦理问题。相反，生物可及性测试测量污染物可被人体吸收的部分，从而提供与生理相关的测量。当考虑到生物可及性时，补救工作可以针对已经确定风险的区域。这种方法可以在保护敏感环境的同时节省大量成本，否则过度保守的补救活动将不必要地干扰敏感环境。

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.