Street Canyon Air Pollution and Pedestrian Health Risk Affected by Household Volatile Chemical Products (VCPs) Emission

Abstract

Household volatile chemical products (VCPs) have emerged as a significant source of volatile organic compounds (VOCs) in urban environments. This study uses a computational fluid dynamics (CFD) model, APFoam, which integrates a comprehensive ozone (O₃)─nitrogen oxide (NO_x)─VOCs photochemical mechanism, to qualitatively evaluate the influence of VCPs emissions on pollutant distributions in the regular canyons (i.e., aspect ratio, AR = 1). Compared to scenarios without VCPs emissions, VCPs emissions at levels comparable to traffic emissions lead to an approximately 60% increase in the concentration of O₃ within the street canyon. The pedestrian-level pollutant concentration and health risk were evaluated, suggesting that more nitrogen dioxide (NO₂) exposure was on the leeward side, while the levels of O₃ exposure were higher on the windward side, with health risk increasing by 1.6–2.2 times with increased VCPs emissions or reduced traffic emissions. A total of 39 emission scenarios, varying in traffic and VCPs emission strengths, were analyzed to assess different mitigation strategies, including traffic-only, VCPs-only, and combined reduction pathways (i.e., adjusting the traffic-to-VCPs emission ratio, T/V). The results indicate that the concentration of O₃ can be effectively reduced only when T/V = 1:5, suggesting that substantial reductions in VCPs emissions are necessary to mitigate pollution. This finding underscores the need for increased focus on VCPs controls, even in the context of vehicle electrification, as traffic reductions alone are insufficient to curb the level of O₃ pollution. The study provides critical insights for air quality management, emphasizing the importance of integrating VCPs emission controls into urban pollution mitigation strategies.