Ambient volatile organic compounds (VOCs) in two coastal cities in western Canada: Spatiotemporal variation, source apportionment, and health risk assessment.

Ambient volatile organic compounds (VOCs) in urban areas is of great interest due to their important roles in the atmospheric photochemistry as well as their potential adverse effects on public health. Limited information is available on the spatiotemporal variation, sources, and health risks of VOCs in the coastal cities of Canada, where the population density is much higher than inland areas. In this study, we investigated ambient VOCs levels, their potential sources and associated health risks in two coastal cities in Metro Vancouver during 2012-2016. Levels of the total measured VOCs were relatively higher in an industrial region in Port Moody (56.7 μg/m) than an urban area of Burnaby south (38.0 μg/m). A clear seasonality was observed for VOCs species with significantly higher levels in winter than in summer except for isoprene. Alkanes were the most dominant compounds at both sites accounting for up to 59.4% of the total measured VOCs, followed by halocarbons, aromatics, and alkenes. Industrial-related emissions (30.5%) and traffic-related emissions (35.8%) were the major sources contributing to ambient VOCs in Port Moody and Burnaby south, respectively, as calculated by the positive matrix factorization (PMF) model. A hybrid health risk assessment strategy using deterministic and stochastic approaches revealed that non-cancer risks of ambient VOCs exposure were all below the safe level of 1 at both cities, while the cumulative cancer risks of toxic VOCs exposure in Port Moody (9.2 × 10) and Burnaby south (7.6 × 10) were significantly higher than the provincial acceptable risk level (1.0 × 10). Surprisingly, the probabilities for cumulative cancer risks of VOCs exceeding the US EPA tolerable risk level (1.0 × 10) were 33.7% and 18.6% in Port Moody and Burnaby south, respectively. From a risk management perspective, greater emphasis on the reduction of emissions of carbon tetrachloride, benzene, and 1,3-butadiene is highly recommended in both cities of Metro Vancouver.