Health risk assessment of heavy metal(loid)s in road dust via dermal exposure pathway from a low latitude plateau provincial capital city: The importance of toxicological verification

The human health risk assessment through the dermal exposure of metal(loid)s in dust from low latitude and high geological background plateau cities was largely unknown. In this study, the road dust samples were harvested from a typical low-latitude plateau provincial capital city Kunming, Southwest China. The total concentration and dermal bioaccessibility of heavy metal(loid)s in road dust were determined, and their health risks and cytotoxicity on human skin keratinocytes were also assessed. The average concentrations of As (28.5 mg/kg), Cd (2.65 mg/kg), Mn (671 mg/kg), and Zn (511 mg/kg) exceeded the soil background values. Arsenic had the highest bioaccessibility after 2 h (3.79%), 8 h (4.24%), and 24 h (16.6%) extraction. Although soil assessment methods showed no health risk in the total heavy metals assessment, based water assessments showed bioaccessible heavy metals As, Mn, Ni and Cd have non-carcinogenic risks for human. In addition, the dust extracts suppressed the cell viability, increased the Reactive oxygen species (ROS) level and DNA damage, and eventually activated the mitochondria-mediated apoptosis pathway, evidenced by the upregulation of Caspase-3/9, Bax, and Bak-1. Cadmium was positively correlated with the mRNA expression of Bax. Both dermal bioaccessibility and cytotoxicity should be considered for accurate human skin health risk assessment of heavy metals in road dust, which may provide new insight for accurate human health risk assessment and environmental management.