Pesticide occurrence and aquatic benchmark exceedances in urban surface waters and sediments in three urban areas of California, USA, 2008-2011

California’s Department of Pesticide Regulation sampled water and sediment for pesticides in three urban areas unaffected by agriculture from 2008-2011. Urban pesticide use is a concern because usage rates are not clearly accounted for since only professionals must report their applications – this does not include residential uses by homeowners. More than 90% of the water samples contained at least one pesticide, with half containing five or more, suggesting that pesticide mixtures are common. During the course of sampling, the detection frequency, number of pesticides per sample, and pesticide concentration all increased during rain events. Imidacloprid was the second most commonly detected insecticide, but it was not monitored for in San Francisco bay, and only eight samples were evaluated from Sacramento. Imidacloprid was detected in half of the samples from Orange County. Levels of imidacloprid were detected up to 0.67 µg/L, so it did not exceed the 1.05 µg/L EPA benchmark, but its prevalence was still concerning. Their findings suggest that imidacloprid may be present in more urban surface waters than have currently been analyzed. The authors recommend continued monitoring of urban waterways.

Ensminger, M.P., R. Budd, K.C. Kelley, and K.S. Goh
Environmental Monitoring and Assessment
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