Source apportionment and health risk assessment of PM2.5-bound heavy metals in peri-urban municipalities adjacent to megacities: Evidence from northern South America

Abstract

Rapid urban expansion in municipalities surrounding major Latin American cities has increased concerns about the health risks associated with PM_2.5-bound heavy metals and metalloids (HMMs). This study investigated the concentrations, sources, and health risks of PM_2.5-bound HMMs in a peri-urban municipality within the Bogotá metropolitan region, Colombia. Fifty PM_2.5 samples were collected between November 2021 and May 2022 (16.7 L/min), and twelve HMMs (V, Cr, Co, Ni, Cu, As, Cd, Sb, Sn, Ba, Pb, and Zn) were quantified by ICP-MS. Monte Carlo simulations were used to assess variability and uncertainty in health risk estimates. The mean PM_2.5 concentration was 33.7 ± 7.2 μg/m³. Zinc, Ba, Pb, Sn, and Cu were the dominant elements, while enrichment factors revealed strong anthropogenic influence, particularly for Sb, Cd, and Sn (EF > 85), indicating contributions from vehicular non-exhaust emissions and industrial activities. Positive Matrix Factorization identified five major sources: non-ferrous metal processing (27.4%), metal-enriched industrial emissions mixed with mineral dust (27.3%), industrial coal combustion (20.8%), heavy fuel oil combustion (18.7%), and traffic-related emissions influenced by brake wear (5.8%). Carcinogenic and non-carcinogenic risks were acceptable for both age groups but higher in adults. In both groups, Ni, As, and Cd dominated non-carcinogenic risk, whereas Cr(VI) accounted for approximately 85% of carcinogenic risk. Monte Carlo analysis confirmed Cr(VI) as the principal contributor to carcinogenic risk and uncertainty. The findings suggest that peri-urban municipalities near large urban centers may face degraded air quality from PM_2.5-bound HMMs, in areas with substantial industrial activity and limited monitoring capacity.