Spatial variation of fipronil and its derivatives in tap water and ground water from China and the fate of them during drinking water treatment in Wuhan, central China.

Fipronil (FP) is an emerging insecticide, however, its occurrence in drinking water and source water is limited. In this work, a total of 789 tap water and 95 ground water samples were collected from China in June 2019 in order to assess occurrence of FP and its derivatives (FPs). FPs were also analyzed in source, treated (n = 10, July), and tap water samples (n = 81, July and October 2019) originating from the central Yangtze River and its tributary, the Hanshui River in Wuhan. The sum concentrations of FPs (ΣFPs) in the tap water in China ranged from not detected (ND) to 5.07 (median: 0.03 ng/L), with FP found in 55.3% of the samples, and other targets ≤ 50.0%. Significant regional variations in the ΣFPs values were found between East China (75th percentile: 0.31 ng/L) and Northwest China (0.04), as well as between East China and North China (0.04). Similar ΣFPs values were found for ground water and tap water. The estimated daily intake of ΣFPs via water ingestion was below 200 pg/kg-bw/day for all age groups and was lower than the reference dose for FP (0.2 μg/kg-bw/day). Additionally, FPs were found in all of the source water samples collected in Wuhan with concentrations in the range of 0.84-2.72 ng/L for ΣFPs (median: 2.39). Most of these FPs were removed during water treatment. Higher concentration of ΣFPs in tap water was observed in July (median: 0.04 ng/L) compared to that in October (ND). This is the first study on the occurrence of FPs in the Yangtze River, the fate of FPs during the tap water treatment, and the regional distribution of FPs in tap water from China.