Chris J. Salice
Director, Environmental Science and Studies Program
Dr. Christopher Salice is Director of the Environmental Science and Studies Program and Associate Professor of Biology at Towson University. His research focuses on applied ecology, ecotoxicology and ecological risk assessment with a focus on applying mechanistic models to improve our understanding of the effects of anthropogenic activities on ecological receptors. He obtained his Ph.D. from the University of Maryland Baltimore developing ecological and evolutionary models of the response of gastropod populations to long-term, continuous contaminant exposure. Following his Ph.D., he worked for the U.S. Army Public Health command where a key accomplishment was refining ecotoxicity testing methods for reptiles. He was then an ecological risk assessor for the U.S. EPA Office of Pesticide Programs where he focused on avian probabilistic risk assessment and helped author the agency's first probabilistic risk assessment for ecological receptors. He has authored more than 75 peer-reviewed publications, agency reports, and risk assessments and is currently supported by grants from the U.S. Environmental Protection Agency, the Strategic Environmental Research and Development Program and the NSF's National Institute for Mathematical and Biological Synthesis.
Prioritizing PFASs Mixtures and Sites for Focused Ecotoxicology, Ecological Risk Assessment and Risk Communication
There is ongoing concern regarding the health and environmental effects of per- and polyfluoroalkyl substances (PFASs). These compounds have been found in a wide variety of human, wildlife, and environmental samples. Of the many PFASs, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have received the most research attention, appear to be the most frequently detected, and are often assumed to be the majority constituents of PFASs at contaminated sites. However, these two PFASs seldom occur singly and are not exclusively dominant components of PFAS mixtures detected in environmental samples. Mixtures of PFASs often contain constituents such as perfluorohexane sulfonate (PFHxS), perfluorohexanoic acid (PFHxA), and perfluorobutane sulfonic acid (PFBS), for instance. In some cases, these less studied compounds actually comprise a considerable quantity of the total PFASs in environmental surface water samples. This is of particular importance as the lack of toxicity data on these other PFASs presents a roadblock to assessing risks of PFASs. Additionally, there are few data on the toxicity of PFAS mixtures further precluding robust estimates of toxicity and risk. Hence, an important research goal is to identify relevant other PFASs and well as representative PFAS mixtures for toxicity testing and risk assessment. To address this research goal that would facilitate ecotoxicity testing and ecological risk assessment for PFAS contaminated sites, we are developing methods for prioritizing PFAS chemicals, PFAS mixtures and PFAS contaminated sites that should be the focus of research. We worked with a data set of surface water concentrations from a number of Department of Defense facilities. Heat maps produced in Excel and the program R are especially helpful as they provide immediately interpretable output regarding which chemicals, mixtures or locations warrant the most attention. Additionally, heat maps are very intuitive and likely have applications in risk communication. Hence, the results of our prioritization efforts provide useful output for identifying (1) the most relevant PFAS chemicals and mixtures and (2) particular sites or PFAS chemicals that likely warrant immediate management or research attention. Additionally, analysis of several data sets indicates that core components of common PFAS mixtures (e.g. PFHxS and PFBS) are seldom-studied compounds and that some commonly studied compounds (e.g. PFOA) are not universally major constituents. We are now using output from the PFAS prioritization scheme to design toxicity experiments on relevant mixtures for both aquatic and terrestrial species. Collectively, this overall approach may have merit for both site-specific risk assessment as well as improving our overall understanding of PFAS toxicity and risk. In summary, we have developed methods for PFAS prioritization that aid in focusing current and future research, assessment and even risk communication.