Seasonal variation and health risk assessment of organophosphate esters in surface and drinking water in Nanjing, China

Purification of tap water sourced from river water is a complex process, and little is known about the concentration change in organophosphate esters (OPEs) in this process. The aim of our study was to investigate the levels and seasonal variability of OPEs from surface to drinking water and clarify the health risk of tap water in Nanjing, China. From April 2017 to February 2018, surface (including river and source water) and drinking water (including effluent and tap water) samples were collected, and every point was sampled in four seasons. Twelve OPEs of water were analyzed by high-performance liquid chromatography. Mann-Whitney U test, spearman correlation analysis and principal component analysis were conducted. High median concentrations of total OPEs (sigma OPEs) were both found in surface (601.88 ng/L) and drinking water (608.26 ng/L). Compared to surface water, the levels of most compounds in drinking water made no change except trimethyl phosphate and triphenyl phosphate. The highest levels of sigma OPEs were found in winter in both types of water. Spearman correlations and principal component analysis showed the different sources of OPEs in surface and drinking water. There was no carcinogenic and non-carcinogenic risk of OPEs in tap water, but higher risk was found in winter. This study provided important information on the levels of OPEs from surface to drinking water in Nanjing, and suggested more attention on the potential human health risk.