Detections of the neonicotinoid insecticide imidacloprid in surface water of three agricultural regions of California, USA, 2010-2011

California’s Department of Pesticide Regulation conducted monitoring for imidacloprid in surface water of three agricultural regions: Salinas Valley, Santa Maria Valley, and Imperial Valley. There were a total of 23 monitoring sites, including rivers, small creeks, and agricultural drains, that were sampled between March and October when most agricultural uses take place. Imidacloprid was detected in 85% of Salinas Valley samples, 100% of Santa Maria samples, and 93% of Imperial Valley samples for an overall detection rate of 89%. The EPA toxicity benchmark of 1.05 µg/L was exceeded in 19% of all samples, with the highest detection at 3.29 µg/L. When the authors compared the detections to the Canadian interim water quality guideline of 0.23 µg/L, 71% of the samples exceeded the guideline. The European guidelines for acute (0.20 µg/L) and chronic (0.067 µg/L) were exceeded in 73% and 88% of the samples, respectively. The authors note that since this study focused on agricultural areas, it does not consider the potential off-site movement of urban imidacloprid applications. Urban and agricultural applications and detections should be considered separately since they have differences in application timing and in off-site movement. It also does not include degradates of imidacloprid, at least one of which may be more insecticidal than the parent compound (imidacloprid olefin).

Authors: 
Starner, K., and K.S. Goh
Journal: 
Bulletin of Environmental Contamination and Toxicology
Year published: 
2012