Health risks of PM2.5-bound metals at a street canyon: Implication for traffic non-exhaust emissions

Traffic non-exhaust emissions are a significant source of toxic metals in fine particular matter (PM_2.5), and thus pose adverse effects on human health. PM_2.5-bound metals were sampled at a street canyon and urban background site during ozone and haze periods in Zhengzhou. Higher metal concentrations were observed at the street canyon than at the urban background site, which was more affected by traffic non-exhaust, oil combustion, and dust emissions. Consequently, PM_2.5-bound metals may cause significant non-carcinogenic and carcinogenic hazards to residents at the street canyon. Traffic non-exhaust and oil combustion were the primary contributors to the non-carcinogenic and carcinogenic risk at the street canyon, respectively. Furthermore, the severe health risk of PM_2.5-bound metals from traffic non-exhaust emissions will remain for a long time at street canyons. This work reveals the health risks from vehicles at street canyons, which is beneficial for further reduction of traffic-related emissions.