Sources, bioaccessibility and health risk of heavy metal(loid)s in the particulate matter of urban areas

Exposure to heavy metal(loid)s in airborne particulate matter (PM) could lead to various adverse health effects. The study investigated the total contents and the bioaccessibility of PM-bound heavy metal(loid)s (Cr, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb), identified their potential sources and evaluated the associated health risk via inhalation in eight typical cities in China (Nanjing, Mianyang, Huangshi, Nanchang, Kunming, Xiamen, Guangzhou, and Wuzhishan). In the study, PM-bound Cr (VI) and As of all eight cities exceeded the limits of World Health Organization, while traffic and industrial emissions were identified as primary sources in most urban areas. The bioaccessibility of PM-bound heavy metal(loid)s exhibited large variations, with their means following the order of Cd > Mn > Co > Ni > Cu > Cr > As > Zn > Pb. The emission sources have important effects on the bioaccessibility of PM-bound heavy metal(loid)s. In particular, atmospheric Cu has its bioaccessibility significantly correlated with the contributions from traffic emissions. The bioaccessibility-based assessment obtained different results from those obtained by using total contents, showing that the non-carcinogenic risks posed by most metal(loid)s were below the acceptable level except for As in Huangshi and Nanchang. These findings highlight the source dependence of inhalation bioaccessibility of heavy metal(loid)s in airborne PM, which could facilitate the identification of priority pollution sources and enhance effective risk-oriented source regulatory strategies in urban areas.