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To examine the trends of particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5) and its elemental constituents during two distinct seasons at a site away from the city center of Delhi and the National Capital Region (Delhi-NCR) of India, this unique study aimed at the development of source-receptor-effect linkages. This research paper presents results of occurrence, long-range transport (LRT), source apportionment, and human health impact assessment of 24 PM2.5-bound trace elements (Al, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Na, Ni, Pb, S, Se, Si, Te, Tl, Zn, and Zr). The concentration of PM2.5 during winter (296 ± 45 μg/m3) was significantly higher than in summer (114 ± 48 μg/m3) and exceeded 24 h Indian standard on most of the measurement days. The seasonal concentration ratios (winter/summer) of individual elements varied from 1.7 (Si) to 5.9 (Tl). The backward trajectory of air masses showed that transboundary transport of pollutants occurred in the downwind direction during winter, indicating that this remote site was affected by transported particulates and local activities. The principal component analysis–absolute principal component score (PCA-APCS) model confirmed five significant sources, vehicles (22.3%), soil/road dust (23.1%), coal combustion (20.9%), open burning (13.8%), and other industries (10.2%) responsible for particulate emission. The results from the multiple path particle dosimetry model (MPPD) showed higher deposition of particulates in the human respiratory system occurred during winter (44%) than in summer (40%). The elements with crustal sources of origin had a higher deposition fraction in the head region (0.27 for Si) compared to elements of anthropogenic sources (0.13 for Li). The excess lifetime carcinogenic risk (ELCR) under winter episodic events increased significantly at 128 × 10−6 compared to the summer non-episodic period at 41 × 10−6.

During the synthesis of engineered nanomaterials (ENMs), various occupational exposures occur, leading to health consequences. To date, there is paucity of studies focused on modeling the deposition of nanoparticles emitted from ENMs synthesis processes. This study aimed to characterise and assess exposure to gold (AuNPs) and silver nanoparticles (AgNPs) during a synthesis process in a research laboratory in South Africa. AuNPs and AgNPs synthesis processes were monitored for an hour in a laboratory using a Scanning Mobility Particle Sizer. The monitoring was conducted at a height of 1.2–1.5 m (m) and 1.5 m away from the hood, assuming a 30 cm (cm) breathing circumference zone. Each synthesis process was monitored thrice to generate reliable point estimates, which were used to assess exposure over 8 hours. A time-weighted average concentration was calculated and compared to the derived 8-h occupational exposure limit (OEL) for AgNPs (0.19 μg/m3) and the proposed provisional nano reference value for AuNPs (20,000 particles/cm3). The Multiple-Path Particle Dosimetry model was used to calculate the deposition and retention of both AuNPs and AgNPs. NPs emitted during the synthesis process were dominant in the nuclei (79% for AuNPs and 54% for AgNPs), followed by the Aitken (12% for AuNPs and 29% for AgNPs), with fewer particles in the accumulation mode (9.2% for AuNPs and 17% for AgNPs). AuNPs and AgNPs generated during the synthesis process were determined at 1617.3 ± 102 cm3 (0.046 μg/m3) and 2,687 cm3 ± 620 (0.077 μg/m3), respectively. For the three exposure scenarios, none exceeded the occupational exposure limit for both AuNPs (provisional) and AgNPs (OEL). Workers in the synthesis laboratory are exposed to a concentration below the recommended occupational exposure limit for silver and the proposed provisional nano reference value for gold. Although, the concentrations to which laboratory workers are exposed to are below safe levels, the assessment of the lung deposition patterns indicate a high particle lung retention which raise concerns about long term safety of workers.