First National-Scale Reconnaissance of Neonicotinoid Insecticides in United States Streams

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Neonicotinoid insecticides (neonicotinoids) were present in a little more than half of the streams sampled across the United States and Puerto Rico, according to a new U.S. Geological Survey (USGS) study. This is the first national-scale study of the presence of neonicotinoids in urban and agricultural land use settings across the Nation and was completed as part of ongoing USGS investigations of pesticide levels in streams.

USGS scientist collecting a water-quality sample from Zollner Creek, Oregon

USGS scientist collecting a water-quality sample from Zollner Creek, Oregon (USGS Site ID 14201300) for a national-scale investigation of the environmental occurrence of neonicotinoid insecticides in agricultural and urban settings. The view in the photo is a oblique downstream view from right bank with the Monitor-McKee Road bridge in the background. Photo credit: Hank Johnson, USGS.

Neonicotinoids are one of the fastest growing classes of insecticides worldwide and are registered for use throughout the United States and the world.  They are used in agricultural and urban settings and some are used predominately as seed coatings to protect seedlings such as corn and soybeans. The insecticides are also used as foliar sprays on horticultural, vegetable, and ornamental crops, pastures, and grasslands, and for domestic pests.

During the single-sample national reconnaissance study of 38 streams, imidacloprid was detected most frequently (37 percent), followed by clothianidin (24 percent), thiamethoxam (21 percent), dinotefuran (13 percent), andacetamiprid (3 percent), and thiacloprid (undetected). Concentrations of imidacloprid were related to the amount of urban land use, whereas clothianidin and thiamethoxam were related to the amount of cultivated crops.

As an addition to the national reconnaissance study, four complimentary studies were led to determine how neonicotinoid concentrations varied in streams over time and during different streamflow conditions. Neonicotinoids were present in urban streams throughout the year, whereas pulses of the insecticides were typical in agricultural streams during the crop planting season.

None of the neonicotinoid concentrations exceeded U.S. Environmental Protection Agency aquatic life criteria, and all detected neonicotinoids are classified as not likely to be carcinogenic to humans. However, the occurrence of low levels in streams for extended periods of time highlights the need for future research on the potential effects of neonicotinoids on aquatic life and terrestrial animals that rely on aquatic life.

This study was supported by the USGS Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology) with additional support from the Georgia Department of Agriculture, USGS Priority Ecosystems Science, and USGS National Water Quality Program

USGS Scientist collecting a water-quality sample from the South Fork Zumbro River, MN

USGS scientist collecting a water-quality sample from the South Fork Zumbro River near Rochester, Minnesota (USGS Site ID 05373005). The USGS is conducting going investigations of pesticide levels in streams in agricultural and urban settings. Photo Credit: Donald S. Hansen, USGS.