Summit Toxicology Principals
(CVs available on request)

Sean M. Hays, Ph.D., President
Dr. Hays is the President and founder of Summit Toxicology, LLP, and is located in Bozeman, Montana. He also holds positions of Assistant Clinical Professor in the Colorado School of Public Health at the University of Colorado and affiliate faculty in the Department of Chemical and Biological Engineering at Colorado State University.  Dr. Hays has over 18 years of experience, specializing in conducting exposure assessments, deriving acceptable exposure limits (for general population and occupational exposures), and developing pharmacokinetic (PK), physiologically based pharmacokinetic (PBPK), and pharmacodynamic (PD) models for drugs and chemicals.  He is the current Vice President of the Risk Assessment Specialty Section of the Society of Toxicology and an active member of the Society for Risk Analysis and the International Society ofExposure Science.  Dr. Hays received a B.S. in biomedical engineering from Texas A&M University, an M.S. in Physiology from the University of Vermont, an M.S. in Chemical Engineering from Colorado State University, and a Ph.D. in Toxicology from the University of Utrecht.  

David Pyatt, Ph.D., Principal
Dr. Pyatt is a Principal and co-founder of Summit Toxicology, LLP.  He also is an Assistant Clinical Professor in the School of Public Health and an Adjunct Professor in the School of Pharmacy, both in the University of Colorado.  Dr. Pyatt is a graduate level instructor in the Environmental Sciences Department at the University of Colorado, Denver campus. He has been actively involved in toxicology research and consulting for the past 20 years, and his work has resulted in approximately 100 peer-reviewed publications and abstracts in the fields of environmental and occupational toxicology, experimental hematology, carcinogenesis and immunology.  A primary focus is laboratory research and an area of continued interest is to understand chemically induced blood disorders, including those related to benzene and lead. Over the past 18 years, Dr. Pyatt has been an instructor and/or course director for graduate and medical courses in environmental toxicology and risk assessment, environmental epidemiology, occupational and industrial health, toxicology, and immunology.  He is a full member of the Society of Toxicology, American College of Toxicology and the International Society of Experimental Hematology. Dr. Pyatt received a B.S. in Biological Sciences from North Carolina State University, and a Ph.D. in Toxicology from the University of Colorado.  

Christopher R. Kirman, M.S., Principal
Mr. Kirman is a Principal at Summit Toxicology, LLP, located in Orange Village, Ohio.  Mr. Kirman is a toxicologist with more than 20 years of experience in regulatory toxicology, dose-response modeling, exposure assessment, and human health risk assessment.  Mr. Kirman has published extensively in the areas of quantitative risk and safety assessment and has developed a number of chemical-specific reference doses (RfDs), reference concentrations (RfCs), cancer slope factors (CSFs), and biomonitoring equivalents (BEs) using techniques such as benchmark dose modeling, physiologically based pharmacokinetic modeling, and pooling of data sets. Mr. Kirman has used Monte Carlo methods to gain understanding of the impact of uncertainty and variation in exposure and dose-response assessments.  Additionally, Mr. Kirman has extensive experience conducting weight of evidence and mode of action evaluations.  He earned his B.A. in Chemistry from Case Western Reserve University (CWRU) and his M.S. degree in Toxicology and Nutrition from CWRU.