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.  He teaches courses on air pollution control, environmental exposure and risk assessment, and sustainable infrastructure.  He is also an adjunct professor in the Division of Environment and Sustainability at the Hong Kong University of Science and Technology, where he has taught on urban air quality and conducts research on exposure to air pollution.

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 has served on CASAC review panels for all six criteria air pollutants, including ozone, particulate matter, nitrogen dioxide, sulfur dioxide, carbon monoxide, and lead.  He was a member of the U.S. EPA Science Advisory Board from 2012 to 2018.  He current serves on an advisory committee on EPA’s “MOVES” vehicle emission factor model. 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.  He currently serves as a member of the Transportation and Air Quality Committee (ADC20) of the Transportation Research Board and on the Editorial Board of the journal Atmospheric Environment.  He is a member of the Publications and Critical Review committees of the Air & Waste Management Association.  In 2018, he wrote and delivered the 48th Annual A&WMA Critical Review on “Trends in Onroad Transportation Energy and Emissions.”

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 the 2019 Frank A. Chambers Award of the A&WMA for excellence in air pollution control. 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.


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.

Honors and Awards

  • Frank A. Chambers Excellence in Air Pollution Control Award from the Air & Waste Management Association, 2019
  • Excellence in Review Award from Environmental Science & Technology, 2017
  • Lyman A. Ripperton Environmental Educator Award from the Air & Waste Management Association, 2012
  • Fellow, Air & Waste Management Association, 2008
  • NCSU Alumni Association Outstanding Research Award, 2008
  • Fellow, Society for Risk Analysis, 2006
  • Chauncey Starr Award, Society for Risk Analysis, in recognition of exceptional contributions to the field of Risk Analysis, 1999


Comparison of real-world vehicle fuel use and tailpipe emissions for gasoline-ethanol fuel blends
Yuan, W., Frey, H. C., Wei, T., Rastogi, N., VanderGriend, S., Miller, D., & Mattison, L. (2019), FUEL, 249, 352–364.
Effect of Air-Conditioning on Light Duty Gasoline Vehicles Fuel Economy
Khan, T., & Frey, H. C. (2019), TRANSPORTATION RESEARCH RECORD, 2673(5), 131–141.
Indoor Exposure to Ambient Particles and Its Estimation Using Fixed Site Monitors
Che, W., Frey, H. C., Li, Z., Lao, X., & Lau, A. K. H. (2019), Environmental Science & Technology, 12(2), 808–819.
Quantification of Energy Saving Potential for A Passenger Train Based on Inter-Run Variability in Speed Trajectories
Yuan, W., Frey, H. C., & Rastogi, N. (2019), TRANSPORTATION RESEARCH RECORD, 2673(5), 153–165.
Comparison of real-world and certification emission rates for light duty gasoline vehicles
Khan, T., & Frey, H. C. (2018), Science of The Total Environment, 622-623, 790–800.
Dynamics of coarse and fine particle exposure in transport microenvironments
Kumar, P., Rivas, I., Singh, A. P., Ganesh, V. J., Ananya, M., & Frey, H. C. (2018), NPJ CLIMATE AND ATMOSPHERIC SCIENCE, 1.
Effect of Light Duty Vehicle Performance on a Driving Style Metric
Tanvir, S., Frey, H. C., & Rouphail, N. M. (2018), TRANSPORTATION RESEARCH RECORD, 2672(25), 67–78.
Real-world fuel use and gaseous emission rates for flex fuel vehicles operated on E85 versus gasoline
Delavarrafiee, M., & Frey, H. C. (2018), Journal of the Air & Waste Management Association, 12(3), 235–254.
Trends in on-road transportation, energy, and emissions
Altshuler, S. L., Ayala, A., Collet, S., Chow, J. C., Frey, H. C., Shaikh, R., … Watson, J. G. (2018), JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION, 68(10), 1015–1024.
Trends in onroad transportation energy and emissions
Frey, H. C. (2018), Journal of the Air & Waste Management Association, 3(6), 514–563.

View all publications via NC State Libraries


Efficacy and Durability of Advanced Retrofitted Emissions Controls for Passenger Service Diesel Locomotives
NC Department of Transportation(8/01/19 - 7/31/21)
Impacts of Autonomous Vehicle Technology on Transportation Systems
NC Department of Transportation(8/01/18 - 7/31/20)
Development of Real-World Light Duty Gasoline Vehicle Emissions Data
US Environmental Protection Agency (EPA)(11/30/-1 - 5/15/18)
Real-World Light Duty Gasoline Vehicle Emissions Measured Using Portable Emission Measurement Systems
US Environmental Protection Agency (EPA)(1/01/18 - 2/28/18)
Evaluation of Real-World Emissions Impacts of Octane and Splash-Blended E25 for Light Duty Gasoline Vehicles
Urban Air Initiative(8/15/17 - 2/28/18)
Managing Energy and Emissions for Rail Operations
NC Department of Transportation(8/01/17 - 8/15/19)
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 - 5/31/19)
Characterizing the Determinants of Vehicle Traffic Emissions Exposure: Measurement and Modeling of Land-Use, Traffic, Emissions, Transformation and Transport
US Environmental Protection Agency (EPA)(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)