From the U.S. Geological Survey:
“Levels of pesticides continue to be a concern for aquatic life in many of the Nation’s rivers and streams in agricultural and urban areas, according to a new USGS study spanning two decades (1992-2011). In contrast, pesticide levels seldom exceeded human health benchmarks.
Over half a billion pounds of pesticides are used annually in the U.S. to increase crop production and reduce insect-borne disease, but some of these pesticides are occurring at concentrations that pose a concern for aquatic life.