Arsenic transformations in the human environment

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Arsenic is well known as a poison and a cancer-causing agent. We propose to study how the chemical form of arsenic changes in the environment, and how these changes influence the potential for harmful effects to humans when they are exposed to arsenic. One of our objectives is to study the change of arsenic’s chemical form, from toxic inorganic arsenic, found in soil and plants, to non-toxic arsenobetaine, found in mushrooms. In doing this we hope to isolate the exact organisms and mechanisms that are responsible for changing arsenic from a toxic to a non-toxic form. We will also determine the arsenic forms in mushrooms commonly found in grocery stores, as well as other food products, including foraged foods, an increasingly popular food trend. We will also study the removal of arsenic from water and soil using wetland plants that take up large concentrations of arsenic, specifically Equisetum sp. (horsetails). For these studies we will use tools in which we have expertise: a synchrotron-based X-ray analysis method (called X-ray absorption spectroscopy), complemented by conventional testing methods, to characterize the distribution of arsenic; and a testing method called bioaccessibility. Bioaccessibility testing allows us to mimic the gastro-intestinal environment of humans or animals in a laboratory, and gives us the amount of arsenic that is soluble in the human stomach and intestines. The proposed work will give insight into possible detoxification and remediation strategies for arsenic contamination of water and soil, as well as the possible arsenic exposures and risks that Canadians may face in their food supply.