A U.S. Geological Survey review identified the herbicides atrazine and metolachlor and the neonicotinoid insecticide imidacloprid as the pesticides posing the highest risk in U.S. surface waters, according to the study findings. The study, published in May in
Environmental Science & Technology, analyzed pesticide concentrations across the Continental United States between 2013 and 2022.
Atrazine recorded the most acute aquatic life benchmark exceedances, while imidacloprid had the highest proportion of affected sites and increasing trends, the researchers reported. Pesticides are nearly ubiquitous in U.S. water systems, and the researchers reported that at least one pesticide was detected in 41% of public supply groundwater wells in a national sample. [1]
Study Scope and Methodology
Researchers examined 80 pesticides, including 54 active ingredients and 26 degradation or transformation products, using data from the USGS National Water Quality Network, according to the study. The network includes 102 surface-water and 258 groundwater sampling locations; 81 surface sites were included in the analysis, yielding more than 10,000 samples and nearly 1 million measurements.
For aquatic life, benchmarks were based on EPA acute and chronic toxicity values, while human benchmarks came from EPA drinking water screening levels including Maximum Contaminant Levels, the study said. The authors noted that periodic