Integrated Human Health and Ecological Risk Assessment for the South River, Virginia: a Bayesian Approach

Regional scale risk assessments can be used to determine the likelihood of effects from multiple stressors on ecological or human endpoints at multiple scales. The Relative Risk Model framework can incorporate ecosystem services as endpoints in this multiple stressor- multiple endpoint approach. Through this research, I aimed to demonstrate an approach to integrating ERA and HHRA that could be applied to assess risk to human health and ecosystem services using the South River, VA as a case study. I applied the Relative Risk Model with Bayesian networks (BN-RRM) to an integrated assessment of four ecosystem services of the South River, Virginia: Human health, Water quality, Recreation, and the Recreational fishery. The BN-RRM approach allowed for the calculation of relative risk to 14 human, biotic, and water quality endpoints from chemical and ecological stressors in the South River. Three separate conceptual models were developed for assessing risk to overall Ecosystem services, Human Health, and Recreation. The services at highest risk in the South River were Water quality and the Recreational fishery. Human health risk for users of the South River was low relative to the risk to other endpoints. Risk to Recreation in the South River was moderate with little spatial variation among the five risk regions. The sensitivity and uncertainty analysis of the BNs identified the parameters that influence risk for each endpoint in each risk region. Mercury concentrations in floodplain soils and river water influence human health risk. River temperature and E. coli bacteria were the main contributors of risk to water quality and recreational river uses. Lack of public access contributed risk to recreation and ecosystem services endpoints. This research is not meant to be a definitive assessment of human health risk to fulfill the regulatory requirements for the site. Rather, it is part of a larger effort to synthesize regional scientific research and better understand the effects of mercury contamination and other stressors in the South River watershed