Abstract: Increasing epidemiological and toxicological evidence links cardio-respiratory and more recently neurological health effects with exposures to ambient particulate matter (PM), and in particular to ultrafine nanoparticles (diameter < 0.15 µm). Emission inventories suggest that mobile traffic sources may be primary direct contributors of these particles to urban atmospheres. Given the amount of traffic in most urban areas, it is important to understand how particles from these sources behave after emission as they are transported away from busy roadways and other major sources, which are also abundant in all other urban areas in which over 50% of the earth’s population resides. This seminar will present a comprehensive summary of the research undertaken over the past almost decade by the Southern California Particle Center (SCPC) to investigate the sources, formation mechanisms, physical and chemical characteristics, population exposure patterns, and health effects of atmospheric particles with a particular emphasis on PM from mobile sources. This will be an overview of research described in greater detail in over 400 refereed publications, and used by federal (US EPA) and state (CARB) agencies to revise and promulgate new air quality PM standards.
Utilizing mobile particle concentrators and other state-of-the-art technologies developed by the USC Aerosol lab, SCPC researchers set about characterizing the physical and chemical PM characteristics on/near freeways, in source and receptor areas of the Los Angeles Basin, the impact of mobile sources on indoor environments as well as ultrafine PM characteristics and emission factors of light-duty or heavy-duty vehicles. We show that concentrations of elemental carbon (EC) and other primary organics on freeways decreased by nearly 50% over five years. This reduction can be related to the effectiveness of the Port of Los Angeles Clean Truck Program, which adopts various regulations targeting diesel vehicles, such as ﬂeet turnover and retroﬁt requirements. To further assess the effectiveness of PM regulations on vehicular emissions, we quantified sources of ambient PM2.5 (dp < 2.5 µm) in Los Angeles during the decade of 2002-2013. Results indicated that, compared to 2002-2006, the median value of daily-resolved vehicular emissions in 2008-2012 statistically significantly decreased by 25%, despite an overall increase or similarity in the traffic flow at the sites following 2007. These findings emphasize the effectiveness of the 2007 emissions standards in reducing the contribution of mobile sources to PM mass. While effective at reducing PM mass emissions, after-treatment devices cannot control non-tailpipe emissions such as break and tire ware. We show that emission factors for metal tracers of break and tire ware have increased on surface streets and freeways by at least 2-fold in a decade, highlighting the rising importance of non-tailpipe emissions on PM toxicity. Lastly, we demonstrate the effectiveness of developing alternative public transportation and revitalizing city centers in the drastic reduction of population exposures to deleterious PM components.
Brief Biography of the Speaker: Dr. Constantinos Sioutas, Sc.D., is the first holder of the Fred Champion Professorship in Civil and Environmental Engineering at the University of Southern California (USC). His research has followed an integrated approach to the problem of the well-publicized and significant effects of particulate air pollution on health and the environment. His research has focused on investigations of the underlying mechanisms that produce the health effects associated with exposure to air pollutants generated by a variety of sources. He has developed many state-of-the-art technologies used by many academic institutions and national laboratories for aerosol sampling and characterization. He has authored over 370 peer-reviewed journal publications, 5 book chapters and holds 13 U.S. patents in the development of instrumentation for aerosol measurement and emissions control. His work has been cited in more than 23,000 scientific publications. He is the recipient of the American Association for Aerosol Research (AAAR) David Sinclair award in 2014 (AAAR’s highest distinction), the Hagen Smit award of Atmospheric Environment for seminal publications, the 2010 Scientific and Technological Achievement Award by the U.S. Environmental Protection Agency, a Fulbright fellow and a trustee of his undergraduate alma mater, the Aristotle University of Thessaloniki in Greece.