Organophosphate esters in source, finished, and tap water in Wuhan, China

As important plasticizers and flame retardants, organophosphate esters (OPEs) have resulted in the contami-nation of various water bodies worldwide. However, their removal efficiency by different tap water treatment processes and seasonal variations in drinking water in China are not fully understood. In this study, source (n = 20), finished (n = 20), and tap (n = 165) water samples sourced from the Hanshui and the Yangtze River were collected in Wuhan, central China from July 2018 to April 2019 to measure selected OPE concentrations. The OPE concentrations in the source water samples ranged 10.5-113 ng/L (median: 64.6 ng/L). Most OPEs were not removed effectively by conventional tap water treatment, except for tris(2-chloroisopropyl) phosphate (TCIPP). Interestingly, trimethyl phosphate content was found to increase significantly during chlorination for water sourced from the Yangtze River. The OPEs could be removed more effectively by advanced processes with ozone and activated carbon (maximum removal efficiency of specific OPE was 91.0%). Similar cumulative OPE concentrations (sigma OPEs) values were found for the finished water and tap water in February rather than in July. The sigma OPEs (ng/L) in the tap water ranged 21.2-365 (median: 45.1). TCIPP and tris(2-chloroethyl) phosphate were the predominant OPEs in the studied water samples. Significant seasonal variations in the OPE residues in tap water were observed in this study. OPE exposure via tap water ingestion posed low health risks to human beings. This is the first study reporting the removal efficiencies of OPEs and the seasonal variations in tap water from central China. This is also the first study documenting the occurrence of cresyl diphenyl phosphate and 2,2-bis(chloromethyl)propane-1,3-diyltetrakis (2-chloroethyl) bisphosphate in tap water. Based on currently avail-able data, the contamination of tap water by OPEs is in the order of Korea > eastern China > central China > New York State, the United States. Additionally, this study provides a method involving a trap column, to eliminate OPE contamination from the liquid chromatography system.

Automated summary

This study investigated the concentrations of organophosphate esters (OPEs) in source, finished, and tap water samples from Wuhan, central China, as well as the removal efficiency of OPEs by different tap water treatment processes and seasonal variations. The results showed that most OPEs were not effectively removed by conventional tap water treatment, except for TCIPP, but could be more effectively removed by advanced processes. TCIPP and tris(2-chloroethyl) phosphate were the predominant OPEs in tap water samples. The study also found significant seasonal variations in OPE residues in tap water, with low health risks associated with OPE exposure via tap water ingestion.