Chemical composition and oxidative potential of fine particulate matter (PM2.5) in urban parks of Bangkok, Thailand: Implication for public health

PM_2.5 poses serious health risks, worsening respiratory and cardiovascular conditions and increasing chronic disease risk. Weather conditions and emission sources affect their composition. PM_2.5 samples are collected from Lumphini and Thonburirom Parks in Bangkok from January 30 to February 8, 2024, and analysed its chemical components and the oxidative potential (OP) using the dithiothreitol (DTT) assay. A correlation analysis was conducted to assess the contributions of PM_2.5 components to and its OP in both parks. The enrichment factor and principal component analysis (PCA) were used to identify potential sources, while multiple linear regression (MLR) analysis quantified their contributions. Additionally, the study investigates the cancer and non-cancer risks associated with heavy metals. Lumphini Park has a mean PM_2.5 concentration slightly higher than Thonburirom Park. Both parks show a higher concentration of organic carbon (OC) in their PM_2.5 levels. Additionally, Thonburirom Park exhibits a higher volume-normalized OP (DTT_v) of PM_2.5 than Lumphini Park, suggesting that inhaling PM_2.5 may induce redox activity and oxidative stress. In Lumphini Park, DTT_v strongly correlate with OC, elemental carbon (EC), and metals, while in Thonburirom Park, it correlates with metals and secondary organic carbon (SOC). PCA identifies primary sources of PM_2.5 as mixed combustion sources (including vehicle emissions and biomass burning), industrial emissions, secondary aerosol (SA) formation, and road dust resuspension. The MLR analysis indicates that mixed combustion sources dominate PM_2.5 concentration in Lumphini Park, while Thonburirom Park is primarily affected by industrial emissions and SA formation. Cr is notably enriched in both parks, indicating significant anthropogenic sources. Furthermore, both parks exceed the acceptable cancer risk threshold of 1 × 10⁻⁶ for Cr, indicating an increased cancer risk for adults and children. This study presents the first-ever analysis of OP of PM_2.5 and its potential sources in urban parks of Bangkok. Average PM_2.5 concentration in both parks exceed WHO standards but remain within Pollution Control Department (PCD) thresholds. Notably, the DTT activity of PM_2.5 is higher in Thonburirom Park than in Lumphini Park. Further studies are required to identify PM_2.5 and its OP sources using more advance receptor models. Additionally, it is important to extend such studies across Southeast Asia to support long-term air quality monitoring efforts.