Chris Frey

Glenn E. Futrell Distinguished University Professor

H. Christopher Frey is a professor of environmental engineering in the Department of Civil, Construction, and Environmental Engineering at NC State. His research interests are measurement and modeling of real-world fuel use and emissions of onroad and nonroad vehicles; modeling and evaluation of advanced energy conversion (e.g., combustion, gasification) and environmental control systems; development and application of methods for quantification of variability and uncertainty and for sensitivity analysis in environmental systems models; and exposure and risk analysis.

Dr. Frey was Chair of the U.S. Environmental Protection Agency’s Clean Air Scientific Advisory Committee (CASAC) from 2012 to 2015.  He chaired CASAC review panels on ozone, nitrogen dioxide, and lead.  He currently serves on CASAC review panels for particulate matter, nitrogen dioxide, and sulfur dioxide.  He is a member of the U.S. EPA Science Advisory Board and an advisory committee on EPA’s “MOVES” vehicle emission factor model. In recent years, he has served on the Board of Environmental Studies and Toxicology of the National Research Council, an EPA Science Advisory Board panel on expert elicitation, National Research Council committees on review of the toxicological assessment of tetrachloroethylene and of EPA’s New Source Review program, a NARSTO assessment of multipollutant air quality management, and a World Health Organization working group on uncertainty in exposure assessment. He was a lead author for 2006 guidance by the Intergovernmental Panel on Climate Change (IPCC) regarding uncertainty in greenhouse gas emission inventories.

Dr. Frey is a Fellow and Past President of the Society for Risk Analysis and a Fellow of the Air & Waste Management Association. Recent awards include a 2008 NCSU Alumni Association Outstanding Research Award, 2008 Mobile Clean Air and Renewable Energy Award, the 2009 Earthwise Faculty Award, and the 2012 Lyman A. Ripperton Environmental Educator Award of the A&WMA. Dr. Frey has a B.S. Mechanical Engineering from the University of Virginia, and from Carnegie Mellon University he has a Master of Engineering in Mechanical Engineering and PhD in Engineering and Public Policy.

More information is available from Dr. Frey about the scientific review of the National Ambient Air Quality Standard (NAAQS) for Ozone.


Ph.D. 1991

Engineering and Public Policy

Carnegie Mellon University

M.S. 1987

Mechanical Engineering

Carnegie Mellon University

B.S. 1985

Mechanical Engineering

University of Virginia

Research Description

Dr. Frey is interested in air pollution emissions, prevention and control; measurement and modeling of activity, energy use, and emissions of on-road and non-road vehicles; exposure and risk analysis; quantification of variability and uncertainty; modeling and evaluation of energy conversion and emission control technologies.


Real-world freeway and ramp activity and emissions for light-duty gasoline vehicles
Frey, H. C., Delavarrafiee, M., & Singh, S. (2017), Transportation Research Record, (2627), 17-25.
Characterization of PM2.5 exposure concentration in transport microenvironments using portable monitors
Li, Z. Y., Che, W. W., Frey, H. C., Lau, A. K. H., & Lin, C. Q. (2017), Environmental Pollution, 228, 433-442.
Dose-response models are conditional on determination of causality
Frey, H. C. (2016), Risk Analysis, 36(9), 1751-1754.
Effect of biodiesel fuels on real-world emissions of passenger locomotives
Graver, B. M., Frey, H. C., & Hu, J. C. (2016), Environmental Science & Technology, 50(21), 12030-12039.
Evaluation of light-duty gasoline vehicle rated fuel economy based on in-use measurements
Khan, T., & Frey, H. C. (2016), Transportation Research Record, (2570), 21-29.
Comparison of vehicle-specific fuel use and emissions models based on externally and internally observable activity data
Hu, J. C., Frey, H. C., & Washburn, S. S. (2016), Transportation Research Record, (2570), 30-38.
Sequential measurement of intermodal variability in public transportation PM2.5 and CO exposure concentrations
Che, W. W., Frey, H. C., & Lau, A. K. H. (2016), Environmental Science & Technology, 50(16), 8760-8769.
Real-world activity, fuel use, and emissions of diesel side-loader refuse trucks
Sandhu, G. S., Frey, H. C., Bartelt-Hunt, S., & Jones, E. (2016), Atmospheric Environment, 129, 98-104.
Comparison of over-the-rail and rail yard measurements of diesel locomotives
Graver, B. M., & Frey, H. C. (2015), Environmental Science & Technology, 49(21), 13031-13039.
Variability in light-duty gasoline vehicle emission factors from trip-based real-world measurements
Liu, B., & Frey, H. C. (2015), Environmental Science & Technology, 49(20), 12525-12534.

View all publications via NC State Libraries


Evaluation of Real-World Emissions Impacts of Octane and Splash-Blended E25 for Light Duty Gasoline Vehicles
Urban Air Initiative(8/15/17 - 12/31/17)
Managing Energy and Emissions for Rail Operations
NC Department of Transportation(8/01/17 - 7/31/19)
Characterizing the Determinants of Vehicle Traffic Emissions Exposure: Measurement and Modeling of Land-Use, Traffic, Emissions, Transformation and Transport
US Environmental Protection Agency (EPA)(1/01/17 - 12/31/17)
Characterizing the Determinants of Vehicle Traffic Emissions Exposure: Measurement and Modeling of Land-Use, Traffic, Emissions, Transformation and Transport
US Environmental Protection Agency (EPA)(8/15/15 - 6/30/17)
Development and Demonstration of Methods for Measurement of Human Exposure to Air Pollution Using Portable Sensors Applied to High Potential Dose Scenarios in Urban Environments
NCSU Center for Human Health and the Environment(8/16/15 - 12/31/16)
Pollutant Exposure in Microenvironments: Examining Air Pollution at a Division I College Football Stadium
NCSU Faculty Research & Professional Development Fund(7/01/15 - 6/30/16)
Traveler Response Architecture using Novel Signaling for Network Efficiency in Transportation (TRANSNET)
US Dept. of Energy (DOE)(10/01/15 - 5/22/18)
Evaluation of Locomotive Emissions Reduction Strategies
NC Department of Transportation(8/16/15 - 12/31/17)
Comparison of Air Pollution in Transportation ENvironments (CAPTEN): Development and Demonstration Based on Selected UK and US Cities
University Global Partnership Network (UGPN)(8/01/14 - 7/31/15)
Measurement of Locomotive Head End Power Engine Fuel and Emissions
NC Department of Transportation(8/16/14 - 8/15/15)