Long-term monitoring of PM2.5 and PM10: Implications for air quality and public health in urban Bangkok, Thailand

Air pollution, particularly ambient particulate matter (PM) PM_2.5 and PM₁₀, poses serious health risks and is linked to high mortality rates in urban areas. A five-year study used Aeroqual Dust Profiler to measure PM levels hourly. PM_2.5 and PM₁₀ were measured at the Faculty of Engineering, Chulalongkorn University in Bangkok from 2019 to 2023, and their correlation with meteorological parameters was investigated. The ratios of PM_2.5 to PM₁₀ were estimated to assess the dominance of either PM size. The exposure risk of PM_2.5 in urban Bangkok was assessed by calculating the relative risk (RR) and attributable fraction (AF) for health outcomes, including cardiovascular and respiratory mortality, lung cancer mortality, childhood asthma, and strokes. The Air Quality Index (AQI) for PM_2.5 was also determined using the single pollutant method. During the cool dry season in Bangkok (December to February), PM_2.5 and PM₁₀ concentrations are significantly higher due to reduced mixing heights, lower wind speeds, and increased anthropogenic activities. In urban Bangkok, coarse PM is mainly attributed to road dust resuspension, construction, and regional pollutant transport. In urban Bangkok, PM_2.5 to PM₁₀ ratios were high (>0.5), indicating a significant presence of fine and secondary particulates. There was a strong positive correlation between PM_2.5 to PM₁₀ each year. Fine and coarse particles correlate differently with meteorological parameters. The RR for health outcomes was high during the cool dry season, while the annual mean AQI remained in the excellent to satisfactory range over the studied years. The monthly mean AQI is categorized as unhealthy during the cool dry season, except in 2022. In urban Bangkok, the mean annual concentrations of PM_2.5 and PM₁₀ over five years are within the limits established by the Pollution Control Department (PCD) but exceed the ambient air quality standards of the World Health Organization (WHO). The cool dry season poses a higher PM_2.5 exposure risk than the rest of the year. During the cool dry season, the monthly AQI is hazardous for vulnerable individuals. The study's limitations include relying on a single monitoring site, which may not reflect PM variability in urban Bangkok. The absence of chemical composition and number concentration analysis hinders source attribution and toxicity assessment. Multi-site studies with comprehensive analysis are needed to better understand PM-related health risks.