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Symposium #19: Mobile Source Air Toxic Concentrations at Residential Sites Proximate to Busy Roadways in Detroit, Michigan

Timothy M. Barzyk1, BJ George1, Alan Vette1, Carry Croghan1, Ronald Williams1, Carvin Stevens1, Jonathan Thornburg2, and Charles Rode2
1U.S. EPA, National Exposure Research Laboratory, RTP, NC;
2RTI International, RTP, NC

Mobile source air toxics (MSATs) are carcinogenic air pollutants emitted by cars, trucks and non-road vehicles. People living, working or going to school near busy roadways are at risk of being affected by these air toxics, and the closer a structure is to a busy roadway, the higher the concentration levels of MSATs. However, perpendicular distance to a roadway is not the only contributing factor to elevated MSAT levels. Ambient background concentrations, wind speed and direction, traffic density, microscale (< 103 m length scales) geographic features, and atmospheric stability also affect near-road concentration gradients. The Detroit Exposure and Aerosol Research Study (DEARS) monitored air pollutants at a central community site (Allen Park), 48 residential locations (indoor and outdoor), and personal exposures. In Year 1 of the study, 34 residential sites were within 500 m of a busy roadway. A linear mixed effects model was employed to determine the contribution of ambient background concentrations, perpendicular distance, and wind speed to outdoor residential MSAT concentrations for 16 pollutants. Model results were significant (p < .05) for six volatile organic compounds (VOCs) and three fine particulate matter (PM2.5) analytes. Ambient concentrations were the most significant contributor to outdoor residential concentrations for these nine MSATs. Perpendicular distance to roadway was a significant contributor for four of the nine MSATs, and wind speed was significant for one. A more precise model is in development that will include annual average daily traffic; a parameter for distance as a function of wind direction relative to the roadway; proximate industrial point sources; and wind fetch over a given roadway. To increase the statistical power of the model, 232 additional sample days will be included from the Year 2 sampling season.

Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

DEARS Home | Human Exposure & Atmospheric Sciences | Exposure Research

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