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Scientists have discovered an overall improvement in the amount of pesticides flowing in Washington State streams.

That announcement wouldn t mean much in the past because the levels can change from year to year depending on rainfall, stream flows, temperature and dozens of other factors. But now, researchers with the state departments of Agriculture and Ecology have ten years of accumulated testing, enough to show a trend.

State Agriculture officials said pesticide concentrations declined over the past decade in salmon bearing streams. They also said most were below levels of concern. But they did find 10 of the 74 pesticides they test for were increasing in concentrations.

The trend would not have been allowed in researchers from the Departments of Agriculture and Ecology hadn t spent the last decade building a baseline to compare the levels.

Rain or shine the teams are wading through the state s most vital streams taking measurements and samples. On Tuesday they were in Seattle s Thornton Creek, where they usually find mostly household pesticides. They will also sample rural streams for pesticides used by farmers and ranchers.

Certain pesticides can kill aquatic life from plants and organism and threaten the health of fish and anything else that lives in or drinks from water bodies downstream.

The goal is to identify and measure pesticides then go to the sources to see if changes can be made.

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