2025 Volume 35 Pages 1-7
Concentrations of fipronil and its degradates (fipronil sulfone, fipronil sulfide, and fipronil deslfinyl: collectively “fipronils” hereafter) were measured with a liquid chromatography-tandem mass spectrometry in influent and effluent samples of a small-scale municipal wastewater treatment plant (WWTP) in Japan, which were monthly sampled for a year, and stream water samples to which the WWTP effluent is discharged. Stream water was sampled from upstream and downstream points of the WWTP. Fipronil was detectable in all the WWTP samples with the median being 1.8 and 2.3 ng/L for influent and effluent, respectively, while the degradates were less frequently detectable (detection frequency: 0-33%). Detection of intact fipronil in influent indicated the use of fipronil insecticide in household. There was no statistical difference between fipronils concentrations in influent and effluent samples indicating that removal of fipronils was inefficient during the treatment process. Fipronil was frequently detectable in stream waters but with lower median concentration by one order of magnitude (0.22 and 0.41 ng/L for upstream and downstream) than WWTP samples. Detection of degradates was more frequent in stream water (25-80%) than in WWTP samples indicating occurrence of degradation products of agriculture-derived fipronil in the environment. There was no statistical difference between fipronils concentrations in upstream samples and those in downstream samples indicating that the discharge of this particular WWTP does not influence stream fipronils concentrations.
