Source specific health risks of size-segregated particulate bound metals in an urban environment over northern India

Particulate-bound metals are reported to be toxic upon exposure through multiple pathways. In this study, both non-carcinogenic and carcinogenic health risks of diverse population age groups from the exposure of particulate-bound metals were systematically investigated considering size-segregated (PM1.1; PM2.1; PM > 2.1) metal concentration measured in between 2015 and 2018. Among the three particulate sizes, metal abundance was high in coarse fraction (PM > 2.1; mean ± SD: 43.1 ± 17.7 μgm−3) compared to fine (PM2.1: 18.5 ± 14.1 μgm−3) and sub-micron particulates (PM1.1: 11.4 ± 9.9 μgm−3). Calcium and sodium were the most abundant species irrespective of particulate sizes, accounting 53–58% of detected metal concentration. Potassium and zinc were the next two dominating species with increased abundance during biomass burning episodes. Potential sources of airborne metals were explored using advanced receptor model. Resuspensions of crustal and road dust were the most dominating sources (30–58% of metal abundance) irrespective of particulate sizes. The other recognized sources were emissions from industrial and vehicular sources, and from biomass/waste burning. Assessment of source-specific health risks indicates shared responsibility, industrial emissions (80%) being the most relevant one for carcinogenic risks. Both biomass and waste burning emissions, and vehicular emissions were found to induce non-carcinogenic risks. The non-carcinogenic health risks were mostly attributed to ingestion of metal contaminated food, especially for children (0.9–2.13 × 10−4). Carcinogenic risks, in contrast, were associated with inhalation of carcinogenic metals e.g., Cr, Pb, Co, Ni and Cd, and were high for adults (3.07–6.04 × 10−5). Health risks associated with exposure to size-segregated airborne metals were within the tolerable level (1 × 10−4) but well exceeding safe level of exposure (1 × 10−6). This emphasizes adapting more strategies and control measures of particulate sources to safeguard the health of resident population.