Arsenic Bioavailability, Bioaccessibility, and Speciation.

The term bioavailability has many different meanings across various disciplines.  Often bioavailability is concerned with human health aspects such in the case of urban children interacting with contaminated soil.  The still utilized approach to base risk assessment on total metal content in soils is an outdated endeavor and has never been proven to be scientifically sound.  Yet to reverse this trend, much work is required to establish base-line bioavailability measurements and to develop complementary methods that are capable of predicting bioavailability across a whole range of impacted media in a cost efficient manner.  Thus, regulators have recognized site-specific human health risk assessments play a key role in decision-making processes at contaminated sites. 

 One option to understand and relate bioavailability in humans is to employ animal surrogates despite unique physiology of most animals as well as the tremendous cost and time involved relative to chemical surrogates.  Chemical surrogate methods generally only require knowledge of the total metal content so that a percent bioaccessible number can be generated from in vitro extractions that simulate digestive systems or mimic responses to sensitive ecoreceptors.  Adaptation of spectroscopic speciation techniques to identify metal phases is extremely beneficial in bioavailability research to understand the variability of biologically available metal uptake, to manipulate the ecosystem to reduce bioavailability via in situ amendments, to monitor the long-term stability of elements to ensure bioavailability indicators do not change over time, and to develop comprehensive predictive models based on speciation.

 Our work emphasizes an integrated multidisciplinary research approach utilizing expertise in soil science, chemistry, toxicology, biology, and spectroscopy to address complex issues of arsenic bioavailability.  Advances in understanding arsenic bioavailability (mice in vivo model), bioaccessibility, and speciation via synchrotron methods will be discussed for soils with differing contaminant sources, concentration, and soil types.