The phenylpyrazole fipronil is a current-use insecticide approved for urban use in California. The primary outdoor use for fipronil is structural pest control which includes outdoor spraying around buildings to control nuisance insects such as ants. Other structural pest control applications, primarily for termite control, include underground injection (into soil around foundations) and indoors in non-occupied foundation spaces (e.g., a dust injected into building wood). Fipronil is also well-known as the active ingredient in anti-flea and tick topical pet applications. Use of fipronil has been steadily increasing since its introduction in 1996 (Simon-Delso et al. 2015). This pesticide and its degradates are of ecological concern in California watersheds because of toxicity to stream insects, particularly chironomids (Weston and Lydy 2014).
Trends were calculated for the fipronil parent compound, three metabolites, and the sum of the compounds using data from 2013 to 2023. Fipronil and its degradates were measured at 40 sites with high urban land use. There was a relatively high incidence of fipronil detection in urban sediments, particularly of the fipronil sulfide and sulfone degradates, which are more toxic than the parent compound (Weston and Lydy, 2014). Statewide, trends in concentrations of the sum of fipronil and its degradates, were stable with the exception of fipronil sulfone, which was significantly decreasing.
Most sites show stable or no trends for fipronil and degradates concentrations. Fipronil is increasing at 12.5% of the sites. Sum fipronil is decreasing at 18% and probably decreasing at 10%. Statewide trends showed significant correlation of fipronil sulfide with urban land use.
Trends were calculated for the fipronil parent compound, three metabolites, and the sum of the compounds using data from 2013 to 2023. Fipronil and its degradates were measured at 40 sites with high urban land use. There was a relatively high incidence of fipronil detection in urban sediments, particularly of the fipronil sulfide and sulfone degradates, which are more toxic than the parent compound (Weston and Lydy, 2014). Statewide, trends in concentrations of the sum of fipronil and its degradates, were stable with the exception of fipronil sulfone, which was significantly decreasing.
Most sites show stable or no trends for fipronil and degradates concentrations. Fipronil is increasing at 12.5% of the sites. Sum fipronil is decreasing at 18% and probably decreasing at 10%. Statewide trends showed significant correlation of fipronil sulfide with urban land use.
