“In Silico Estimation of PFAS Properties” by Dr. Paul Tratnyek (SERDP Project ER20-1481)
The environmental fate, effects, and remediation of chemical contaminants are determined by their properties, such as phase partitioning coefficients, reaction rate constants, and toxicities. For emerging contaminant families—such as in sensitive munitions compounds (ISMs) and per- and polyfluoroalkyl substances (PFAS)—these property data tend to be lacking. Therefore, methods are needed to estimate these properties using statistical correlations (i.e., quantitative structure-activity relationships [QSARs]) and/or chemical structure theory. This presentation will focus on the development of such methods to provide estimates of physico-chemical properties for most PFAS. These methods have two major benefits in addition to property prediction. First, they are very effective for assessing the quality of existing data. Second, they can be a powerful tool for diagnosis of underlying processes (e.g., modes of toxicity). However, the prediction of properties of PFAS presents special challenges. They are usually present as cations and/or anions, whereas most prediction methods work well only for neutral compounds, and carbon-fluorine bonds are not well represented in prediction models for chemical transformations. To overcome the former challenge, the project team is developing a way to estimate partition coefficients for anions from data for the neutral forms. This method requires pKa’s for PFAS, which we can estimate from fully in silico calculations. With respect to the effects of carbon-fluorine bonds on partitioning, the project team is exploring a variety of hybrid models.
“PFAS Bioaccumulation in Freshwater Fish ” by Dr. Christopher Salice (SERDP Project ER19-1193)
Aquatic systems are often sinks for PFAS contamination. Freshwater fish can accumulate PFAS when exposed, which may result in ecological effects or fish consumption advisories. Moreover, fish are often the focus of PFAS monitoring and assessment programs. There are important gaps in our knowledge and understanding of PFAS bioaccumulation in fish. For example, there can be substantial variability in PFAS accumulation across fish species and studies and different PFAS. This presentation will focus on research to better understand how environmental, physiological and ecological factors may influence bioaccumulation of different PFAS in environmentally common yet understudied fish species. The project team found that data highlighting temporal, spatial, and species-specific differences in PFAS revealed several factors to consider for better understanding and predicting PFAS concentrations in fish tissues. Moving forward, a combination of laboratory, field and modeling efforts are likely to yield important insights and predictive tools.
Dr. Christopher Salice is a professor in the department of biological sciences and director of the environmental science and studies program at Towson University in Towson, Maryland. Prior to moving to Towson, Dr. Salice was an associate professor in the department of environmental toxicology at Texas Tech University. Before entering academia, he was an ecological risk assessor with the U.S. Environmental Protection Agency (EPA) Office of Pesticide Programs and a toxicologist with the U.S. Army Public Health Center. His research has focused on understanding the effects and risk of anthropogenic chemicals to algae, birds, and reptiles. Since 2010, he has been working on ecotoxicity and ecological risk of PFAS, using field research, laboratory toxicity studies, and risk modeling. Dr. Salice’s current SERDP projects include a focus on bioaccumulation of PFAS in fish and ecotoxicity of PFAS and PFAS-free foams to ecological receptors, especially reptiles. He received his doctoral degree in toxicology from the University of Maryland, Baltimore.
Dr. Paul G. Tratnyek is a professor in the School of Public Health at the Oregon Health & Science University in Portland, Oregon. Dr. Tratnyek has served as a National Research Council (NRC) Postdoctoral Fellow at the U.S. EPA Laboratory in Athens, GA and as a Research Associate at the Swiss Federal Institute for Water Resources and Water Pollution Control (EAWAG). He joined the faculty in the department of environmental science and engineering at the Oregon Graduate Institute (OGI) where he became involved in OGI’s Center for Groundwater Research and the University Consortium Solvents-In-Groundwater research program based at the University of Waterloo where he became involved in research on zerovalent iron (ZVI) for remediation of contaminated groundwater. Since then, Dr. Tratnyek’s areas of research have expanded to include most aspects of in situ chemical reduction and oxidation, including some of the earliest work on abiotic reduction of contaminants and the largest body of high-impact research on ZVI. Much of this work has targeted chlorinated solvents and explosives, but also applies to emerging and recalcitrant contaminants like 1,2,3-trichloropropane and PFAS. A cross-cutting theme in most of Dr. Tratnyek’s work is the use of correlation analysis to develop predictive models for contaminant fate determining properties. He received his doctoral degree in applied chemistry from the Colorado School of Mines.