Characteristics of trace elements bound to ambient nanoparticles (PM) and a health risk assessment in southern Thailand.

Ambient nanoparticles, or PM and thirteen trace elements (Al, Ba, K, Fe, Cr, Cu, Ni, Na, Mn, Mg, Ti, Pb, and Zn) were studied in Hat Yai, Thailand during the year 2018. The annual average PM mass concentration was 8.45 ± 1.93 µg/m. The PM levels in Hat Yai were similar to those in large cities in South East Asia, such as Hanoi and North Sumatra, but lower than other cities in Thailand. The sum of thirteen trace elements was 207.83 ± 17.06 ng/m and was dominated by Na, Zn, K, Mg, and Al. The highest concentration of elements occurred in the pre-monsoon season followed by the dry and monsoon seasons. A principal component analysis (PCA) indicated that PM comes from motor vehicles, crustal dust, industrial and biomass burning. The PM was dominated in the pre-monsoon season, suggesting that biomass burning from the southwest direction could cause an increase in the levels of Cr, Ti, and Ni. The total cancer risk from all the carcinogenic elements was 1.98 × 10 in adults, indicating that the carcinogenic risk is in a tolerable risk assessment range. The increasing levels of PM during transboundary haze pollution and local source emissions are a concern.