From Science:
Researchers visited 186 streams and 5000 wells across the country. Every stream had at least one pesticide at some time, and 10% had levels that exceeded the benchmark at which human health effects are possible. The prevalence of pesticides was much lower in ground water; only 1.2% of wells exceeded the benchmark. There is more concern for aquatic organisms and the wildlife that feed upon them. Of the 178 streams near farms or cities, 56% had one or more pesticides exceeding benchmarks. “Aquatic life in urban streams is particularly threatened,” said report author Robert Gilliom, who leads the USGS’s Pesticide National Synthesis Project Study Team.
More here.