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State study finds pesticides in salmon streams, but at mostly low levels

OLYMPIA — Concentrations of pesticides found in salmon-bearing waters in five Washington state watersheds are low and generally below levels of concern for most pesticides, according to just-released report from the state departments of Ecology (Ecology) and Agriculture (WSDA).

The report's authors concluded that pesticide concentrations found between 2006 and 2008 are not expected to directly affect salmon. However, pesticide concentrations found at some sites may harm aquatic invertebrate populations that serve as a food source for salmon.

Since 2003, the joint-agency program has collected weekly samples from salmon-bearing waters in Washington that represent both agricultural and urban landscapes. The program is one of the most intensive pesticide monitoring efforts for surface waters in the country.

"This pesticide monitoring project provides policymakers with a valuable tool to inform their decision making," said WSDA Director Dan Newhouse. "Federal or state agencies and lawmakers need accurate data about the low levels of pesticides present in the waters of our state as they evaluate the effectiveness of our current regulations and laws."

Rob Duff, manager of Ecology's Environmental Assessment Program said, "This news is encouraging, however we need to consider the combined effects from multiple pesticides and other stressors such as higher stream temperatures and low dissolved oxygen."

The new report contains results from surface water samples the program collected from 2006 to 2008. The state collected water samples from Thornton Creek in Seattle, the Skagit Delta, the lower Yakima Valley, and from the Wenatchee and Entiat basins.

During the three year period, the state analyzed 1,194 samples for more than 160 pesticides and pesticide-breakdown products. Analysis detected 74 pesticides or break-down products, with nearly all present at concentrations so low that they did not violate state or federal water quality standards.

Periodically, the program detected six currently registered insecticides (permethrin, chlorpyrifos, diazinon, azinphos-methyl, malathion and endosulfan) at levels that do not meet state or federal water quality standards.
The program also detected levels of DDT that do not meet water quality standards. DDT persists in the environment even though it has not been registered for use in the United States since 1972.

The lower Yakima Valley sites had the greatest number of pesticide detections that did not meet water quality standards.

WSDA and Ecology compared the data collected during this sampling period to data from 2003 to 2005. The only statistically significant trend the agencies identified was a decrease in the number of herbicide detections in Thornton Creek, an urban watershed that drains into Lake Washington.

WSDA continues to work with pesticide applicators to identify steps to reduce pesticide exposure in salmon habitat, including uses of application techniques that reduce potential transport of pesticides to water. The agency plans for future monitoring efforts to evaluate the success of such strategies and determine if further action is needed.

The report is called "Surface Water Monitoring Program for Pesticides in Salmonid-Bearing Streams 2006-2008 Triennial Report - A Cooperative Study by the Washington State Departments of Ecology and Agriculture."

To read the report, visit the WSDA Web site at http://agr.wa.gov/PestFert/NatResources/SWM or go to Ecology's website at http://www.ecy.wa.gov/biblio/1003008.html.

For more information about Ecology's pesticide monitoring, visit www.ecy.wa.gov/programs/eap/toxics/pesticides.htm. The WSDA Pesticide Management Division Web site is http://agr.wa.gov/PestFert.

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