Abstract: Objective To investigate the concentration levels of nonylphenol (NP) and bisphenol A (BPA) in the drinking water of four Chinese provinces and to assess the associated health risks. Methods From June to August 2022, samples of source water, finished water, and tap water were collected from 49 municipal water supplies across four provinces. The concentrations of NP and BPA were determined using solid-phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A non-carcinogenic health risk assessment was subsequently conducted for NP. Results The detection frequencies for NP and BPA were 65.31% and 44.90%, respectively, with median detected concentrations of 5.09 ng/L and 0.04 ng/L. The concentration of NP was significantly higher than that of BPA (z=-4.27, P<0.01). Significant inter-provincial variations were observed: the median NP concentration in Province D (164.00 ng/L) was the highest, followed by Province C (58.24 ng/L), Province A (5.17 ng/L), and Province B (0.04 ng/L) (χ²=40.90, P<0.01). For BPA, the median concentration in Province A (10.02 ng/L) was highest, followed by Province C (3.07 ng/L), Province D (0.04 ng/L), and Province B (0.04 ng/L) (χ²=56.84, P<0.01). The median NP concentration was significantly higher in surface water (9.86 ng/L) compared to groundwater (1.50 ng/L) (z=-3.09, P<0.01). The median BPA concentration in source water (4.80 ng/L) was significantly higher than in finished water (0.04 ng/L) and tap water (0.04 ng/L) (χ²=9.26, P<0.01). A significant positive correlation was identified between NP and BPA concentrations (P<0.01), as well as between NP concentration and water temperature (P<0.01). The non-carcinogenic risk from NP ingestion via direct drinking was higher for children than for adults, with the highest hazard quotient observed for male toddlers aged 1 to<2 years, calculated as 1.34×10⁻² and 4.47×10⁻¹ based on Danish and Australian reference values, respectively. Conclusion Trace quantities of NP and BPA, at the ng/L level, were detected in the drinking water of the four provinces. BPA concentrations were all below the regulatory limit set by China's drinking water standards (GB 5749-2022). The non-carcinogenic risk associated with NP was below the threshold of 1, indicating an acceptable level.

Key words: Drinking water contamination, Nonylphenol, Bisphenol A, Health risk assessment, Solid-phase extraction, Liquid chromatography-tandem mass spectrometry