Inorganic composition of PM2.5 in the lower northern region of Thailand and their potential impact on human health

Abstract

This study aimed to assess the levels of inorganic substances, including trace metals and ionic species in PM_2.5 in a semi-urban region located in the lower northern region of Thailand. It also aims to investigate the potential impacts of trace metals on human health. Samples of PM_2.5 were collected using a low volume air sampler (LVS) with a flow rate of 5 L min⁻¹ over a period of 24 h. Trace metal concentrations were measured using inductively coupled plasma-mass spectroscopy (ICP-MS) and ionic compositions were determined using ion chromatography (IC). Human health risk evaluations were carried out in accordance with the health risk assessment regulations of the United States Environmental Protection Agency (USEPA). The results of this study showed that the average concentration of PM_2.5 was 69.0 ± 33.4 µg m⁻³ above the standards set by USEPA for a 24 h average. Source identification using principal component analysis (PCA) based on trace metal and ion compositions suggested that the main sources of PM_2.5 were crustal elements (28%) and a combination of biomass burning and motor vehicles (19%). High enrichment factor (EF) values (> 100) for As, Cd, and Pb indicated that these metals were significantly enriched and greatly influenced by anthropogenic sources. The trace metal hazard quotients (HQ) and excess lifetime cancer risks (ELCR) were within acceptable limits. This study suggests the need for an awareness of PM_2.5 emissions and their trace metal compositions, especially from motor vehicles and biomass burning.