PFAS Forum Date Change: Now September 9-11

Dr. Ronald Kotun


Presentation Title

Variability in Per- and Polyfluoroalkyl Substances (PFAS) Toxicity Values and its Impact on Evaluating Risk

Dr. Ronald Kotun, Senior Toxicologist, Tetra Tech


A scientific literature review indicates that PFAS toxicity data are prevalent for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA); much less toxicity data are available for other PFAS.  However, differences in regulatory standards exist among state, federal and international agencies.  These differences are due to the selection and interpretation of key toxicity studies used to derive the standards. An evaluation of the variability in toxicity values will be explored and the impacts on risk-based screening levels and regulatory standards will be evaluated.


Dr. Kotun is a senior toxicologist and risk assessment specialist with Tetra Tech.  He is also the company’s technical lead for emerging contaminants, including polyfluoroalkyl substances, otherwise known as PFAS.  He has over 30 years of environmental experience.  He has prepared risk assessments and provided technical reviews for CERCLA, RCRA, and state-driven risk-based programs.  He has worked for a broad spectrum of clients including the Department of Defense and wood-treating, aerospace, steel, utilities, automobile, chemical, and retail petroleum industries.  His use of risk assessment has been instrumental in establishing site-specific remedial objectives.