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).

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