Prioritizing emerging organic pollutants in rivers of Thailand using suspect screening analysis with high-resolution...

Efforts to regulate emerging organic pollutants (EOPs) as new chemicals enter the market are often inadequate, and many potentially harmful EOPs remain unregulated especially in Thailand. Wastewater treatment plants, which are ineffective at eliminating EOPs, act as key sources of these substances in aquatic environments. In this study, four river water samples from different regions of Thailand were analyzed using a suspect screening approach based on a suspect list of 951 EOP compounds. More than 200 suspect features were matched with suspect lists, and 185 features out of them were found in all river samples, which indicates the widespread presence of EOPs in these water sources. Among the detected features, 43 had agreement with product ion spectra in the mzCloud database. The concentration was estimated using machine learning tool, and five compounds exceeded predicted no effect concentration (PNECs). Subsequent analyses using reference standards confirmed the presence of 17β-estradiol (3-15 ng L^-1 in the four river water samples), 17β-trenbolone (98-282 ng L^-1), imidacloprid (9-24 ng L^-1), buprofezin (1-4 ng L^-1), and triphenylphosphine oxide (16-86 ng L^-1). Most of these results exceeded their PNECs, which is consistent with the machine learning tool, indicating potential ecological risks. These findings highlight the need for continuous monitoring of high-risk EOPs. Overall, this study presents a practical framework for wide-scope screening and prioritization of unregulated micropollutants, particularly applicable to environmental management in developing countries.