Fipronil is a phenylpyrazole insecticide that has emerged as an important pest management tool in California.  Between 2008 and 2012, approximately 43,000 lbs of fipronil were applied annually for structural control of ants and termites.  The majority of reported use surrounds large urban centers.  There is a concern that fipronil concentrations in runoff derived from residential and commercial areas are negatively effecting water quality of surrounding surface waters due to the high toxicity of fipronil and its degredates to aquatic species.  The Department of Pesticide Regulation (DPR) has been monitoring fipronil in California surface waters since 2008.  Samples have been collected at forty-nine stations within 9 watersheds located in 6 counties throughout the state to develop a robust temporally and spatially diverse dataset.  Almost half of 460 samples contained detectable levels of fipronil, as well as significant amounts of sulfone (40%) and desulfinyl (30%) metabolites.  Detection frequency correlates with the potential toxicity to aquatic endpoints, with forty-eight percent of fipronil samples and thirty-seven percent of sulfone samples at concentrations higher than the minimum aquatic benchmark value set by the US EPA.  Regional differences exist, with higher concentrations observed at stations located in southern California.   Temporal analysis has revealed no significant trend in fipronil concentrations at our monitoring stations.  Almost all fipronil containing products used for outdoor applications are restricted to licensed applicators, therefore future outreach efforts to help reduce fipronil runoff in urban streams shall be concentrated on this group.

Monitoring efforts of an emergent insecticide fipronil in California surface waters

248th National Meeting (2014)

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