State Ag Department Happy withby Shannon Dininny, Associated Press
YAKIMA, Wash. -- Low levels of pesticide residues were detected in four Washington state drainages in the second year of a pesticide monitoring program, according to a new report.
However, high concentrations of one pesticide, malathion, in one drainage raised concerns. Malathion is an insecticide commonly used on crops such as alfalfa, asparagus, apples and cherries.
Overall, the state Department of Agriculture praised the findings in the report. The agency contracted with the state Department of Ecology in 2002 to monitor pesticides in salmon-bearing streams.
"We're generally pleased. We wanted to come right out and say we did see this one detection, but from all the samples and analysis we've done, we're very pleased with what we're seeing," Bridget Moran, manager of the Agriculture Department's Endangered Species Program, said Friday.
Results of the three-year study will help determine any mitigation efforts that might be needed to reduce exposure.
Three drainages in the Lower Yakima Valley watershed were selected for monitoring, representing agricultural pesticide use. They are Spring Creek, Sulphur Creek and Marion Drain. Thornton Creek in King County, in the Cedar-Sammamish watershed, is being monitored to represent pesticide use in an urban area.
In 2004, sampling occurred weekly from March to October at all downstream sites in all the selected drainages. Samples were taken every other week at upstream locations on Spring Creek and Thornton Creek.
Surface waters were sampled for 144 chemicals, including 87 currently registered pesticides, products that evolve from the breakdown of pesticides and a number of pesticides that were used historically but are now banned.
Five pesticides were found at concentrations above established water quality values. Four were repeats from last year, including DDT. DDT was a pesticide used in orchards between 1940 and 1970. The chemical is now banned.
One of the five, diazinon, was found in Thornton Creek, the urban drainage. The other four, including DDT and malathion, were found in the Lower Yakima Valley watershed, the report said.
Just one of the five found this year - malathion - was at a level that raised concerns, Moran said.
In one sample, the concentrations of malathion in the Marion Drain approached, but did not exceed, a specific water quality value known as the lethal concentration for rainbow trout.
Lethal concentration is the point at which scientists would predict death to half of the species present over a given period of time.
"We're in the process of trying to determine the uses in that area, the crops that are right around it," Moran said. "We don't really want to draw all the correlations until we're done with the three-year study cycle."
Sampling for the third and final year of the study began in March and will continue through the end of October. Results of the study are expected to be released next summer.
learn more on topics covered in the film
see the video
read the script
learn the songs