Characterization of ultrafine particles and number size distribution of airborne particles in Buddhists religious places in Bangkok

Abstract Burning incense is a common practice in Asian countries that has been shown to be a significant source of indoor particulate matter and other contaminants. Despite this, there remains a substantial gap in our understanding of the particle size distribution and characteristics of ultrafine particles resulting from incense burning. The objective of this research is to characterize the particle number size distribution observed near incense burning source and far from incense burning source in temples/shrine in Bangkok, Thailand. Sampling was conducted in four different temples and a shrine located throughout Bangkok. The sampling period of one day at each site cover the operating hours from 10 AM to 5 PM. This study utilized real-time aerosol measurement instruments, namely the Scanning Mobility Particle Sizer (SMPS) and the Optical Particle Sizer (OPS). Together the instruments were capable of detecting particle from 10nm to 10μm. Two sets of instruments were deployed concurrently to indicate near-source and far-from-source situations. The highest particle number concentrations were recorded at 1.62×10 6 particles/cm 3 and 5.11×10 5 particles/cm 3 for near source and far from source, respectively. The “near-source” concentration was consistently almost an order of magnitude higher than the “far-from-source” concentration. The hourly particle size distributions at all sites generally exhibited three modes, with occasional periods showing four or five modes. In general, almost all peak number concentrations occurred in the ultrafine particle size range (<100 nm). Based on the hourly average particle number concentration, the predominant size range was 10-100 nm. The results suggest that individuals whose work involves the use of incense are exposed to very high concentrations of ultrafine particle (UFP). Given that the particles emitted from incense sticks are predominantly in the UFP size range, prolonged inhalation of this smoke poses significant health risks.