Pollution Characterization and Health Risk Assessment of VOCs, CO, and NOx in Underground Garages
This study investigated air pollution and associated health risks in two underground parking garages located in educational and commercial districts of Nanjing, China. Concentrations of non-methane hydrocarbons (NMHC), volatile organic compounds (VOCs), carbon monoxide (CO), and nitrogen oxides (NOx) were monitored. NMHC levels ranged from 0.35–0.55 mg·L−1 (as C) in Garage A and 0.36–1.75 mg·L−1 (as C) in Garage B, peaking during evening rush hours. A total of 23 VOC species were identified, including benzene, toluene, ethylbenzene, xylenes, dichloromethane, and 1,2-dichloroethane. Benzene series compounds constituted over 90% and 70% of total VOCs (TVOCs) in Garages A and B, respectively. Daily average TVOC concentrations were 146.0 μg·m−3 (weekday) and 49.7 μg·m−3 (weekend) in Garage A, and 2398.1 μg·m−3 and 3401.6 μg·m−3 in Garage B. Maximum CO concentrations reached 10.1 mg·m−3 and 12.6 mg·m−3, exceeding the Chinese indoor standard of 10 mg·m−3 (1-h). NOx levels also exceeded standards. Non-carcinogenic hazard indices (HI) were 0.03 and 0.18, below the EPA threshold of 1. However, carcinogenic risks reached Level II and III, with primary contributors being benzene, 1,2-dichloroethane, and naphthalene in Garage A, and ethylbenzene, benzene, and 1,2-dichloroethane in Garage B. The findings indicate potential health threats to garage users, necessitating enhanced ventilation and exposure mitigation.