By STEVE BROWN
OLYMPIA -- Pesticide concentrations have generally declined in several of Washington state's salmon-bearing streams flowing into Puget Sound and the Columbia River, officials say.
Water quality monitoring conducted by the Washington state departments of agriculture and ecology over the past decade looked at both agricultural and urban watersheds.
"This is certainly the direction we would have wanted to see," WSDA Director Dan Newhouse said. "This monitoring program is unique in that it provides growers with real-world data on the potential impact pesticide use could have on local streams and creeks, which in turn allows farmers to apply pesticides wisely and continue these efforts to protect salmon and the environment."
The report is the first to identify increasing and decreasing trends for individual pesticides.
Agricultural areas monitored for the report include the Lower Skagit-Samish, Lower Yakima, Wenatchee and Entiat watershed areas. Urban areas include the Cedar-Sammamish and the Green-Duwamish watersheds.
From March through September, researchers collect weekly samples and test them for more than 170 pesticides and related compounds, issuing brief annual reports and a longer, more comprehensive report every three years. When detected, scientists found that most pesticides showed up at concentrations below levels of concern for aquatic species.
Ten pesticides were associated with increasing concentrations over a five-to-nine-year period, so the WSDA will focus attention on them to ensure that farmers and pesticide applicators are aware of the trend and that the pesticides are being applied in a manner that will not negatively impact the environment.
Those pesticides include the herbicide metolachlor; the insecticides bifenthrin, chlorpyrifos, DDVP, diazinon, endosulfan, ethoprop, malathion, methiocarb, methomyl and an endosulfan breakdown product (endosulfan sulfate). DDT, which is no longer registered for use, and its breakdown products have also been detected at levels above the standards.
WSDA communications director Hector Castro said this is information farmers can use. "A lot of farmers are as interested in protecting the environment as anything else," he said.
Researchers also used the data to estimate the potential effects of pesticide mixtures. Even where levels are low, several pesticides in combination could pose a problem. By using toxicity information and the concentrations found in the samples, researchers were able to calculate "toxic units" for each pesticide found in a given sample.