Nanoparticles (NPs), nanoaerosols (NAs), ultrafine particles (UFPs), and PM_0.1 (diameters ≤ 0.1 µm or 100 nm) are used interchangeably in the field of atmospheric studies. This review article summarizes recent research on PM_0.1 in Thailand. The review involved peer-reviewed papers that appeared in the Scopus and the Web of Science databases and included the most recently published articles in the past 10 years (2013–2022). PM_0.1 mainly originate from combustion processes such as in motor vehicles. The highest mass concentration of PM_0.1 occurs during the dry season, in which open fires occur in some regions of Thailand. The northern area of the country has higher PM_0.1 mass concentrations, followed by the central and southern areas. Carbonaceous nanoaerosols are produced during normal periods, and the proportions of organic to elemental carbon and char to soot suggest that these originate from motor vehicles. However, in haze periods, biomass fires can also produce carbon-containing particles. PM_0.1 pollution from local and cross-border countries also needs to be considered. The overall conclusions reached will likely have a beneficial long-term impact on achieving a blue sky over Thailand through the development of coherent policies and managing new air pollution challenges and sharing knowledge with a broader audience.

PM_0.1was found to be a major contributor to the mass fraction of perfluoro alkyl substances, which is more influenced by the type of land use than country differences.

PM_0.1 (particles with a diameter ≤ 0.1 µm), nanoparticles (NPs), or ultrafine particles (UFPs) were interchangeably used in the scientific communities. PM_0.1 originated from both natural and human sources; however, PM_0.1 and its effects on the environment, visibility, and human health to understanding air pollution levels, sources, and impacts in Southeast Asia (SEA) countries continue to be challenging. The concentrations of PM_0.1 in most SEA countries are much worse than in western countries’ environments. A further motivation of this reviewed article is to provide a critical synthesis of the current knowledge and study of ambient PM_0.1 in SEA cities. The primary influence of characteristics of PM_0.1 appears to be local sources, including biomass burning and motor vehicles. Continuous monitoring of PM_0.1 in mass and number concentration should be further understood. A critical review is of great importance to facilitating air pollution control policies and predicting the behavior of PM_0.1 in SEA.

The concentration of total suspended particles (TSP) and nanoparticles (PM_0.1) over Hat Yai city, Songkhla province, southern Thailand was measured in 2019. Organic carbon (OC) and elemental carbon (EC) were evaluated by carbon aerosol analyzer (IMPROVE-TOR) method. Thirteen trace elements including Al, Ba, K, Cu, Cr, Fe, Mg, Mn, Na, Ni, Ti, Pb, and Zn were evaluated by ICP-OES. Annual average TSP and PM_0.1 mass concentrations were determined to be 58.3 ± 7.8 and 10.4 ± 1.2 µg/m³, respectively. The highest levels of PM occurred in the wet season with the corresponding values for the dry seasons being lower. The averaged OC/EC ratio ranged from 3.8–4.2 (TSP) and 2.5–2.7 (PM_0.1). The char to soot ratios were constantly less than 1.0 for both TSP and PM_0.1, indicating that land transportation is the main emission source. A principal component analysis (PCA) revealed that road transportation, industry, and biomass burning are the key sources of these particles. However, PM arising from Indonesian peatland fires causes an increase in the carbon and trace element concentrations in southern Thailand. The findings make useful information for air quality management and strategies for controlling this problem, based on a source apportionment analysis.