Publication Summary

Initiated in 1991 by the Department of Ecology, the Washington State Pesticide Monitoring Program (WSPMP) has analyzed ground water, surface water, fish tissue, and sediments for pesticide residues. The results of these analyses are used to provide information on the distribution of pesticides in Washington State and to determine if these patterns are changing over time.

WSPMP surface water samples were collected at the mouths of two urban streams, Juanita Creek in Kirkland and Indian Creek in Olympia, every other week from April 28 to August 18 of 1997.

Initiated in 1991 by the Department of Ecology, the Washington State Pesticide Monitoring Program (WSPMP) has analyzed ground water, surface water, fish tissue, and sediments for pesticide residues. The results of these analyses are used to provide information on the distribution of pesticides in Washington State and to determine if these patterns are changing over time.

WSPMP surface water samples were collected at the mouths of two urban streams, Juanita Creek in Kirkland and Indian Creek in Olympia, every other week from April 28 to August 18 of 1997. Samples were also collected from five upstream source identification sites on May 12, July 7, and August 26.

Twenty-one pesticides and breakdown products -- 15 herbicides, five insecticides, and one fungicide -- were detected in 35 water samples collected for the 1997 WSPMP. The most frequently detected herbicides were dichlobenil, triclopyr, 2,4-D, MCPP, and prometon. Diazinon and chlorpyrifos were the most commonly detected insecticides. Diazinon exceeded water quality criteria in 11 samples from Juanita Creek and in two samples from Indian Creek. Three samples from Juanita Creek (King County) and one from Indian Creek (Thurston County) contained levels of chlorpyrifos above water quality criteria.

Pesticide contamination in Juanita Creek was comparable to the most contaminated agricultural drainages in the state that have been sampled for the WSPMP, including irrigation returns in the Yakima Valley and Mid-Columbia Basin. The total number of pesticides detected and the average number per sample are among the highest in the state. Only 14 pesticides were found in samples from the Indian Creek drainage, and only two of these compounds were detected in more than half of the samples. The average number of pesticides per sample was 5, compared to 10 for Juanita Creek.

The most frequently detected pesticides in samples from both streams are readily available to the public for home use. The remaining compounds detected are pesticides that have been found in other WSPMP samples from urban areas, and were probably applied by professional applicators. As a group, the home use pesticides were detected almost twice as often as the professionally applied chemicals.

Stormwater runoff samples tended to contain higher numbers of pesticides and/or higher concentrations of the detected pesticides.

Link to EIM data for User Study ID WSPMP97W