Health risks and source apportionment assessment of potentially toxic elements in PM_2.5: a one year observation study...

Potentially toxic elements (PTEs) pollution in PM_2.5 and its health risks have attracted increasing attention. In this study, nine PM_2.5-bound PTEs (Cr, Mn, Co, Cu, Zn, Cd, Ba, Pb, Fe) were continuously measured in Chengdu during 2023 and their concentrations, sources, seasonal variations and health risks were systematically evaluated. The annual mean concentrations of Cr(VI) (0.48 ng/m³) and Cd (15.66 ng/m³) exceeded the limit value of the Chinese National Ambient Air Quality Standards (0.025 ng/m³ and 5 ng/m³, respectively) by factors of 19.3 and 3.1, respectively. Monthly concentrations exhibited a U-shaped pattern, peaking in January-May and November-December. Overall, non-carcinogenic risks for all population groups were below the safety threshold, whereas carcinogenic risks for adult male were of concern. Source apportionment showed that mixed industrial-crustal (MIC) sources (43-64%) dominated PTEs in all seasons and were the largest contributor (86-94%) to the hazard index (HI). The contributors to total carcinogenic risk (CR) varied seasonally: in spring and autumn, traffic and MIC sources were the primary contributors; in summer, MIC sources were dominant; and in winter, traffic emissions were leader, accounting for 72% of CR. A fireworks episode during the Spring Festival sharply increased Cu, Cr, Ba and Pb, with short-term exposures posed risks comparable to or exceeding seasonal levels, contributing 46% of HI and 55% of CR. This study reveals discrepancies between source apportionment by mass and by health risk, and highlights overlooked health risks from fireworks.