"Mobile source emissions present a unique public health threat," said Timothy Buckley, PhD, senior author of the study and professor with the School's department of Environmental Health Sciences. "This study provides a unique, real world assessment of the relationship between traffic volume, vehicle class, the weather and curbside concentration of carcinogens. Our findings give us a basis for assessing the public health gains from alternate fuels, control technologies or, best of all, the removal of traffic emissions from our neighborhoods through non-fossil fuel mass transit."
Dr. Buckley and doctoral student Amir Sapkota measured levels of the carcinogens benzene, 1,3-butadiene and PAHs at a tollbooth at Baltimore's Harbor Tunnel over a one week period. Meteorological information and traffic data were also collected and analyzed. Results showed that pollution levels varied 6 to 20 fold depending on both traffic volume and the type of vehicle. The lowest levels were recorded in the middle of the night and the highest levels occurred with the morning rush hour.
Larger vehicles with more than two axles, such as buses, motor homes, and tractor trailers, were found to emit 60 times more PAHs, 32 times more 1,3-butadiene and nine times more benzene compared to smaller vehicles with just two axles. The researchers suggest that the increased emissions associated with the larger vehicles are due in part to the diesel engines that more likely power these larger vehicles.
"In Baltimore's urban communities as with many other U.S cities, many people live in close proximity to busy streets. What's more, in many communities, the curbside stoop provides a venue for socialization, recreation or relief from the summer heat, exacerbating their exposure potential. The models we created from this study may be useful for evaluating exposure, risk and control strategies in theses urban environments," said Dr. Buckley.
"The Mobile Source Effect on Curbside 1,3-Butadiene, Benzene and Particle-Bound Polycyclic Aromatic Hydrocarbons Assessed at a Tollbooth" was written by Amir Sapkota and Timothy J. Buckley.
Research was supported by grants from the Johns Hopkins Education and Research Center Pilot Project Research Training Fund, National Institutes of Environmental Health Sciences and Environmental Protection Agency.
Link to the Johns Hopkins Bloomberg School of Public Health at www.jhsph.edu.
Journal of the Air & Waste Management Association