Atmospheric Heavy Metal Pollution Characteristics and Health Risk Assessment Across Various Type of Cities in China

This study investigates the spatiotemporal trends and health risks of nine atmospheric heavy metals (Pb, As, Mn, Ni, Cr, Cd, Zn, Cu, Fe) in PM_2.5 across 50 Chinse cities, comparing resource-industrial cities (RICs) and general cities (GCs) before (2014-2018) and after (2019-2021) China's 2018 Air Pollution Prevention and Control Action Plan. Post-2018, concentrations of all metals except Fe declined significantly (33-77%), surpassing PM_2.5 reductions (25%). Geospatial analysis revealed elevated heavy metal levels in northern and southern regions in China, aligning with industrial and mining hotspots. While RICs exhibited persistently higher metal concentrations than GCs, the inter-city gap narrowed post-2018, with RICs achieving greater reduction. Pre-2018, the combined non-carcinogenic hazard index (HI < 1) remained below safety thresholds, but the combined carcinogenic risk total (CRT) for children exceeded 10^-4, driven primarily by As and Cr(VI). HIs were 1.5-2.0 times higher in RICs than in GCs. Post-2018, the CRT declined by 69.0-71.1%, aligning with reduced heavy metal levels. Despite improvements, CRTs necessitate targeted mitigation for As (contributing 81.1-86.2% to CRT) and Cr(VI) (11.7-14.0%). These findings validate the policy's effectiveness in curbing industrial and vehicular emissions but underscore the need for metal-specific controls in resource-intensive regions to safeguard child health.