The results of the study, published in Environmental Pollution, "found levels of neonicotinoid insecticides at up to 20 times the concentrations deemed toxic to aquatic organisms," reports the Summit County Citizens Voice in Frisco, Calif. Traces of the chemicals were found in the Mississippi and Missouri rivers. "The rivers studied drain most of Iowa, and parts of Minnesota, Montana, Nebraska, North Dakota, South Dakota, and Wisconsin. These states have the highest use of neonicotinoid insecticides in the nation, and the chemicals were found in all nine rivers and streams." (USGC map: where studies were conducted)
"They found one or more of three different kinds of neonicotinoids in each of the 79 samples," Marcotty writes. "The highest concentrations were found in smaller watersheds where farming was the dominant use of the landscape; lower concentrations were found in the big rivers that drained areas with more diverse uses."
Kathryn Kuivila, a scientist at the USGS Oregon Water Science Center in Portland, Ore., and the study's lead author, said it was not clear what impact the pesticides have in aquatic ecosystems, Marcotty writes. "Levels considered toxic by the EPA are many times higher than those found in the USGS samples. But Kuivila said that other studies have found that toxicity can be much lower for some species, and others have found that the number of tiny worms and other soil insects drops precipitously at very low concentrations." (Read more)