Differing Ambient Particle Composition and Oxidative Toxicity in 12 Cities in Inner Mongolia: Reference for Regional Optimized Air Pollution Control

Current air quality standards and control measures are largely based on a universal particulate matter (PM) mass value, overlooking composition-dependent health risks that vary by source and region. Here, PM samples from 12 Inner Mongolia cities were collected using automobile air filters in studying their PM compositions and oxidative potential (OP). We show that 12 cities across Inner Mongolia differed significantly in PM compositions and OP, with mass-normalized OP varying by 7-fold across cities. Industrial cities (Baotou and Ordos) exhibited extremely high metal enrichment (e.g., Cr, Mn, Ce, and Nd) from steel production and rare earth mining, which may contribute to the highest OP, while PM-borne polycyclic aromatic hydrocarbons such as benzo[a]pyrene and pyrene profiles differed from megacities. Mn, Zn, and rare earth elements were identified as key chemical drivers of OP, while specific fungal genera (Didymella, Fusarium) affected OP both directly and synergistically with chemical components. Our findings revealed that PM components varied greatly among cities; thus, a shift from mass-based toward composition- and source-oriented risk assessment transferable frameworks is badly needed. The protocol and data obtained here can be followed by other regions in an effort to optimize health return and economic cost during air pollution control strategies.