Urban arterial corridors are landscapes that give rise to short and long-term exposures to transportation-related pollution. With high traffic volumes and a wide mix of road users, urban arterial environments are important targets for improved exposure assessment to traffic-related pollution. A common method to estimate exposure is to use traffic volumes as a proxy. The study presented here analyzes a unique yearlong dataset of simultaneous roadside air quality and traffic observations for a U.S. arterial to assess the reliability of using traffic volumes as a proxy for traffic-related exposure. Results show how the relationships of traffic volumes with NO and NO 2 vary not only by time of day and season but also by time aggregation. At short-term aggregations (15 minutes) nitrogen oxides were found to have a significant linear relationship with traffic volumes during morning hours for all seasons although variability was still high (r 2 = 0.1-0.45 NO, r 2 =0.14-0.27 NO 2), and little to no relationship during evening periods (r 2 <0.01-0.03 NO, r 2 <0.01-0.05 NO 2). Comparisons with coarse annual results validate the use of traffic volumes to estimate annual exposure concentrations for morning periods (r 2 = 0.89 NO, r 2 =0.87 NO 2) and evening NO 2 (r 2 =0.46). Traffic volumes are a weak or poor predictor for annual evening NO (r 2 =-0.09) and short-term 15 minute aggregations. Seasonal and diurnal characterizations show that roadside PM 2.5 (mass) measurements do not have a relationship with local traffic volumes, leading us to conclude that PM 2.5 mass is more tied to regional sources and meteorological conditions. As epidemiology and personal exposure assessment research aims to study health impacts and pollutant levels encountered by pedestrians, bicyclists, those waiting for transit, and other road users, these results show when traffic volumes alone can be a reliable proxy for exposure and when this approach is not warranted.

Bicycling as a mode of transportation is increasingly seen as a healthy alternative to motorized transportation modes. However, in congested urban areas, the health benefits of bicycling can be diminished by the negative health effects associated with inhalation of particulate matter. Particles of small size (ultrafine particles <0.1 μm) are the most harmful, even during short-duration exposure. Because vehicular exhaust is the major source of ultrafine particles, the impact of traffic levels and bicycle lane characteristics on exposure of bicyclists was studied. Ultrafine particle exposure concentrations were compared in two settings: (a) a traditional bicycle lane adjacent to the vehicular traffic lanes and (b) a cycle track design with a parking lane separating bicyclists from vehicular traffic lanes. Traffic measurements were made alongside air quality measurements. The cycle track design mitigated ultrafine particle exposure concentrations for cyclists. Results showed statistically significant differences in terms of exposure levels for the two bike facilities, as well as correlations between traffic levels and exposure level differences. Results also suggested that ultrafine particle levels and spatial distribution were sensitive to proximity to signalized intersections. Findings of this research indicated that, in high traffic areas, bicycle facility design had the potential to lower air pollution exposure levels of bicyclists.

A directed-flow nose-only inhalation exposure system was constructed to support development of physiologically based pharmacokinetic (PBPK) models for complex hydrocarbon mixtures, such as jet fuels. Due to the complex nature of the aerosol and vapor-phase hydrocarbon exposures, care was taken to investigate the chamber hydrocarbon stability, vapor and aerosol droplet compositions, and droplet size distribution. Two-generation systems for aerosolizing fuel and hydrocarbons were compared and characterized for use with either jet fuels or a simple mixture of eight hydrocarbons. Total hydrocarbon concentration was monitored via online gas chromatography (GC). Aerosol/vapor (A/V) ratios, and total and individual hydrocarbon concentrations, were determined using adsorbent tubes analyzed by thermal desorption-gas chromatography-mass spectrometry (TDS-GC-MS). Droplet size distribution was assessed via seven-stage cascade impactor. Droplet mass median aerodynamic diameter (MMAD) was between 1 and 3 mum, depending on the generator and mixture utilized. A/V hydrocarbon concentrations ranged from approximately 200 to 1300 mg/m(3), with between 20% and 80% aerosol content, depending on the mixture. The aerosolized hydrocarbon mixtures remained stable during the 4-h exposure periods, with coefficients of variation (CV) of less than 10% for the total hydrocarbon concentrations. There was greater variability in the measurement of individual hydrocarbons in the A-V phase. In conclusion, modern analytical chemistry instruments allow for improved descriptions of inhalation exposures of rodents to aerosolized fuel.

School officials and community citizens in Georgia were concerned about the airborne trichloroethylene (TCE) that was emanating from a nearby industrial facility that used TCE as a degreaser. No measurements of airborne TCE in the community were taken by public health officials or the industrial facility. The regulation of release of TCE from this facility was governed, in part, by mathematical model predictions of dispersion into the community. In support of community health concerns, the authors collected a limited number of outdoor and indoor air samples in the affected community, including those from a school, a small business, and three homes, for the analysis of TCE. The mean outdoor air concentration of TCE for all affected sites was 0.96 microg/m3 with a peak TCE concentration of 4.59 microg/m3. The mean indoor air concentration of TCE for all affected sites was 1.40 microg/m3 with a peak TCE concentration of 4.66 microg/m3. All collected air samples were below the guideline level of 5 microg TCE/m3 of air as used by the state of Georgia in the United States, but sample levels were greater than those found in large population studies of TCE in indoor and outdoor air in Minnesota in the United States and in Ottawa in Canada. Additional air samples are needed to better characterize the exposure of the community to TCE.

This report summarizes the findings of a national project to examine the travel behavior, social capital, health, and lifestyle preferences of residents of neotraditional developments (NTD) compared to more standard suburban developments. We compare survey results from residents of matched pairs of neighborhoods in seventeen U.S. cities and towns, with each pair comprised of one NTD and one typical suburban neighborhood of similar size, age, and socio-demographic composition. The study addresses salient themes in the transportation, planning and health literatures: a national study, surveying populations of diverse incomes, collecting resident information on preferences for and attitudes towards neighborhood qualities, and addressing transportation and health outcomes for diverse community designs.