Ambient air sampling campaigns were carried out in Windsor, Ontario, Canada as well as in Detroit, Michigan, USA and Sarnia, Ontario over a five year period. Sampling campaigns were for two-week periods in each of the four seasons of 2004-2006 in Windsor, fall 2005 in Sarnia and fall (2008) and spring (2009) for Windsor - Detroit. In Windsor, analyses of the benzene, toluene, ethylbenzene, and xylene (BTEX) species for 2004, 2005, and 2006 is reported in this thesis along with BTEX for Sarnia in 2005. Across the international airshed encompassing Windsor and Detroit, simultaneous sampling of nitrogen dioxide (NO2), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and BTEX is reported for 2008 and 2009.

Temporal and spatial patterns of concentrations, ratios and correlations among pollutants, as well as the effects of sampler placement, wind patterns and transboundary pollution were studied. Windsor experienced similar concentrations compared with Sarnia and lower concentrations than Detroit. Correlation and inter-specie BTEX ratio analysis identified traffic as the common source of VOCs, BTEX, and NO 2 in Windsor and Detroit. An innovative approach was applied in Sarnia using BTEX concentrations and ratios to characterize mixtures of industrial and mobile sources in different areas of the city.

Temporal and spatial variability was observed. Seasonal comparisons to annual concentrations and spatial patterns indicate that if resources are limited, fall would be preferred to conduct air quality campaigns in Windsor. The locations of hot spots in Windsor were not qualitatively associated with wind patterns during the sampling periods. Additionally there was a lack of association between air mass pathways and measured NO₂ and PM_2.5 concentrations in Windsor.

Comparisons between concentrations obtained from the sampling campaigns and those from central monitoring stations indicate that these stations are adequate for representing citywide averages. For residential exposure assessment however, these could result in misclassification up to a factor of six. Risk maps demonstrate BTEX exposure risk across Windsor.

Study design recommendations were made for future air quality campaigns. These include sampling frequency, density, and placement, exposure misclassification associated with central site measurements, and for identifying sources for pollutant reduction initiatives.