Bioaccessibility and health risk assessment of Pb and Cd in urban dust in Hangzhou, China

Heavy metals in urban dust can enter the human body through a variety of ways, thus endangering human health. Understanding the bioaccessibility of heavy metals in urban dust is a key to its risk assessment. After the G20 summit in 2016, Hangzhou city has received much attention, including its environmental health risk. The surface dust collected from three different functional areas in Hangzhou were subjected to the in vitro physiologically based extraction test (PBET) to measure the bioaccessibility of Pb and Cd. In terms of spatial variation, the distribution of Pb bioaccessibility was in the order of residential areas > city parks > main roads > the Botanic Garden, while for Cd ordered in city parks > residential areas > main roads > the Botanic Garden. For temporal variation, the bioaccessibility of Pb was higher in autumn and winter, and the bioaccessibility of Cd was higher in spring and autumn. Based on multiple linear statistical analysis, the relationship between the spatial and temporal distribution differences of the bioaccessibility of Pb and Cd in the city and the main components was discussed. Meanwhile, the non-carcinogenic hazard quotients of Pb and the carcinogenic risk of Cd were calculated and showed no harm to human health, except the total Pb in the surface dust with a high non-carcinogenic risk for infants. Urban dust in Hangzhou city has a slight pollution and health risk from Pb. Currently, controlling and reducing the city's Pb emission is the key to maintain Hangzhou city's air quality and matching with its international tourism city.