Abundance, Source Apportionment and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons and Nitro-Polycyclic Aromatic Hydrocarbons in PM2.5 in the Urban Atmosphere of Singapore

Abstract

In this study, the levels of fine particulate matter (PM2.5), polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in PM2.5 samples were determined from 2020 to 2021 in Singapore. For analysis convenience, the sampling period was classified according to two monsoon periods and the inter-monsoon period. Considering Singapore’s typically tropical monsoon climate, the four seasons were divided into the northeast monsoon season (NE), southwest monsoon season (SW), presouthwest monsoon season (PSW) and prenortheast monsoon season (PNE)). The PM2.5 concentration reached 17.1 ± 8.38 μg/m3, which was slightly higher than that in 2015, and the average PAH concentration continuously declined during the sampling period compared to that reported in previous studies in 2006 and 2015. This is the first report of NPAHs in Singapore indicating a concentration of 13.1 ± 10.7 pg/m3. The seasonal variation in the PAH and NPAH concentrations in PM2.5 did not obviously differ owing to the unique geographical location and almost uniform climate changes in Singapore. Diagnostic ratios revealed that PAHs and NPAHs mainly originated from local vehicle emissions during all seasons. 2-Nitropyrene (2-NP) and 2-nitrofluoranthene (2-NFR) in Singapore were mainly formed under the daytime OH-initiated reaction pathway. Combined with airmass backward trajectory analysis, the Indonesia air mass could have influenced Singapore’s air pollution levels in PSW. However, these survey results showed that no effect was found on the concentrations of PAHs and NPAHs in PM2.5 in Indonesia during SW because of Indonesia’s efforts in the environment. It is worth noting that air masses from southern China could impact the PAH and NPAH concentrations according to long-range transportation during the NE. The results of the total incremental lifetime cancer risk (ILCR) via three exposure routes (ingestion, inhalation and dermal absorption) for males and females during the four seasons indicated a low long-term potential carcinogenic risk, with values ranging from 10−10 to 10−7. This study systematically explains the latest pollution conditions, sources, and potential health risks in Singapore, and comprehensively analyses the impact of the tropical monsoon system on air pollution in Singapore, providing a new perspective on the transmission mechanism of global air pollution.

Main Emission Sources and Health Risks of Polycyclic Aromatic Hydrocarbons and Nitro-Polycyclic Aromatic Hydrocarbons at Three Typical Sites in Hanoi

“…[2-NFR]/[2-NP] ratios close to 10 and 100 are typically used to determine if the formation pathway of NPAHs is dominated by OH and NO 3 radical-initiated reactions, respectively [88,89]. As shown in Figure 5a, the [2-NFR]/[2-NP] ratio in this study ranged from 1.89 to 20.8, and closer to 10, the results of which are similar to those in our previous studies in Hanoi, Singapore and Xinxiang, China [32,58,63]. This result showed the importance of the OH radical-initiated reaction pathway in Hanoi in both summer and winter.…”

Seasonality of Polyaromatic Hydrocarbons (PAHs) and Their Derivatives in PM2.5 from Ljubljana, Combustion Aerosol Source Apportionment, and Cytotoxicity of Selected Nitrated Polyaromatic Hydrocarbons (NPAHs)

“…On the other hand, NPAHs and OPAHs could cause especially severe adverse effects on the environment and human health [ 3 , 5 ]. While toxic equivalency factors (TEFs), which are used to express human toxicity of a pollutant in terms of BaP, are already available for many unsubstituted PAHs; TEFs for NPAHs are often missing [ 16 ]. Although NPAHs have rarely been tested even on human cell lines [ 17 ], their toxic potential is theoretically huge due to the aromatic nitro groups [ 5 , 18 ].…”

Spatiotemporal Distribution Characteristics and Inventory Analysis of Near-Road Traffic Pollution in Urban Areas

“…where EF i is the enrichment factor of element i in atmospheric particulate matter, M i and M Al are the concentrations of elements i and Al in atmospheric particulate matter, and S i and S Al are the abundances of elements i and Al in crustal surface soils, respectively [29][30][31][32].…”