Dr. Mengdawn Cheng is a Distinguished R&D Staff Member in the Environmental Sciences Division at Oak Ridge National Laboratory (ORNL). His core research is focused on investigating the sources, formation, and environmental behavior of airborne materials or aerosols in natural and man-made environments. Dr. Cheng has extensive experience and publications in the fields of environmental sampling, source-receptor relationship modeling and environmental impact assessment, atmospheric transport and transformation modeling, and aerosol engineering technology. His work has been supported by US federal agencies, spanning a wide range of missions and research projects that address emissions and formation of particulate matter emitted by air-breathing and ground-based vehicles, aircraft bleed and cabin air quality, energetics, and short-term climate forcing by aerosols in the Arctic. In collaboration with nanophase materials scientists at ORNL and in other domestic and international organizations, Dr. Cheng has conducted research to investigate toxicity as well as occupational and environmental exposure of engineered nanomaterials (as produced and incorporated in commercial products) and the impacts that they may have on human health. A new and ongoing research area for Dr. Cheng is in nuclear forensics as applied to homeland and global security. During his quarter of century tenure at ORNL, Dr. Cheng has won several awards in his career and served on various advising capacities in technical committees for US federal government agencies. Dr. Cheng currently holds 5 patents and has authored over 290 publications. Dr. Cheng has a Ph.D. in atmospheric chemistry in environmental engineering from the University of Illinois at Urbana-Champaign.