Arsenic transformations in terrestrial animals

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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 or animals when they are exposed to arsenic. We will do this by first measuring the arsenic chemical forms present in samples that humans or animals may be exposed to. We will also determine the reasons for the arsenic changes with a focus on whether they occur as detoxification responses. We will use two tools that we have expertise in: synchrotron-based 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 environment and gives us the amount of arsenic that is soluble in the stomach and intestines. The first step we will undertake will be to develop conventional testing methods that can identify arsenic-sulfur species, allowing us to quantify these species in samples whose arsenic concentrations are too low to study by XAS. Our second step will be to determine the chemical forms of arsenic in birds, mammals and insects, by combined conventional (including the methods developed for arsenic-sulfur analysis) and XAS methods. The third step is to measure the arsenic chemical forms that are soluble in the gastro-intestinal environment (bioaccessible) in some of these samples, which will help us to determine if humans or animals are at risk of harmful effects from arsenic exposure.