Submicron particulate exposure and attributable health risks

Abstract

A comprehensive investigation was conducted on the carcinogenic and noncarcinogenic health risks of various population age groups for exposure to airborne submicron particle-bound metals in a tropical urban city over South Asia. Initially, submicron particulate mass was monitored from November 2022 till February 2023 to assess any time-specific trend in particulate mass concentration. For the majority of the monitoring days (>90%), PM1 mass concentration remained ≥100 µg m−3 with occasional cases when it exceeded 200 µg m−3. Mean concentration of PM1 was 125 µg m−3 (±47 µg m−3; N: 51) with interquartile range varying from 93 to 147 µg m−3. Approximately 21% (±5%) of particulate mass was noted to be composed of airborne metals with no robust season-specific variations, while trace metals accounted for 4.4% of particulate mass and 16% of total metal abundance. Among the metals, crustal-borne calcium (6.6 ± 3.2 µg m−3) contributed maximum proportion of metallic mass, followed by K (5.1 ± 2.8 µg m−3). The presence of trace metals with specific signatures of industrial emissions, such as Mn, Fe, Cr, Co, Pb, Ni, Cd, and Cu, was also detected, sharing 4.6% of particulate mass with overall concentration of 5.1 µg m−3. Among the trace metals, Fe was the most prevalent within the particulate mass, followed by Cr. The relevant sources of PM-bound metals were further quantified using principal component analysis. It revealed the disproportionate contribution of four factors, traced by the universal signature of marker species, and explained a total variance of 87%. Crustal resuspension (46%) was found to contribute major fraction of absolute particulate mass, followed by industrial emissions (19%), whereas both biomass/waste combustion and vehicular emissions were found to individually contribute approximately 10%-11% of particulate-bound metals. Geo-accumulation index revealed major Zn contamination with respect to earth's crust. We note that exposure levels for noncarcinogenic PM1 metals were high in children, especially through consumption of metal-contaminated food. On the contrary, adults were at risk to metal exposure with carcinogenic potential through inhalation. Overall, we conclude that health risks attributed through exposure to PM1-bound metals were within the tolerable limit in the city of Varanasi with few exceptions. © 2025 Elsevier Inc. All rights reserved.