| Exposure to automobile exhaust is a significant public health concern because it is ubiquitous in communities and it contains numerous hazardous air pollutants (HAPs) including 1,3-butadiene, a known human carcinogen. In addition to being ubiquitous, concentration of automobile exhaust is elevated in densely populated urban areas due to high vehicle density and increasing congestion, further exacerbating risks. This thesis work was designed to advance our understanding of mobile source-related exposure to 1,3-butadiene including the development of methods for measuring internal dose. Together, these advances address critical uncertainties in risk assessment and epidemiological studies linking automobile exhaust and cancer.; To investigate the relationship between vehicle counts and ambient 1,3-butadiene levels, concurrent measurements of both variables were made at the Baltimore Harbor Tunnel (BHT) tollbooth facility in Baltimore, MD, over consecutive 3-hour intervals on 7 weekdays (n = 56). The 3-hour outdoor 1,3-butadiene concentrations varied according to time of day and traffic volume. The minimum levels occurred at night (12 a.m.--3 a.m.) with a mean of 2.0 mug/m 3 (SD = 1.3, n = 7) while the maximum levels occurred during the morning rush hour (6 a.m.--9 a.m.) with a mean of 11.9 mug/m3 (SD = 4.6, n = 7). The corresponding 3-hour traffic counts were 1,413 (SD = 144) and 16,893 (SD = 692), respectively. Using multivariate regression, a significant association (p < 0.001) between traffic and curbside pollutant concentrations was observed. As much as 62% of the variability in ambient 1,3-butadiene levels was explained by traffic volume, class, and meteorology. Results suggest that >2-axle vehicles emit 32 times more 1,3-butadiene than do 2-axle vehicles. This study provides an empirical model for estimating curbside air pollution levels associated with traffic that may be relevant to exposures in the urban environment.; The study was further extended to assess worker exposures. The potential workday exposure of tollbooth workers to 1,3-butadiene (and other HAPs) and the protection offered by the tollbooths were evaluated using simultaneous indoor and outdoor measurements at the BHT tollbooth. Mean outdoor 1,3-butadiene concentrations varied by shift with the morning (10.7 mug/m3) exceeding afternoon (7.2 mug/m3) and the lowest levels observed during the night (3.7mug/m3) when traffic volume was the lowest. (Abstract shortened by UMI.)... |
