NEWS NOTES ON SUSTAINABLE WATER RESOURCES  Pesticides in Midwestern Streams  https://www2.usgs.gov/envirohealth/geohealth/articles/201...

NEWS NOTES ON SUSTAINABLE WATER RESOURCES  Pesticides in Midwestern Streams  https://www2.usgs.gov/envirohealth/geohealth/articles/2018-01-02-pesticides_in_midwestern_streams.html  U.S. Geological Survey (USGS) scientists measured and estimated potential acute and chronic toxicity for 227 pesticides in agricultural and urban streams in Midwestern United States. Numerous pesticides were detected at low levels. Atrazine, acetochlor, metolachlor, imidacloprid, fipronil, selected organophosphate insecticides, and carbendazim were determined to be major contributors to toxicity that was estimated in over half of the streams studied.  The Midwestern landscape has been extensively modified, with row crops and pavement replacing grasslands and woodlands. A wide variety of pesticides are used in these modified landscapes to control insects, weeds, and fungi. Exposure to pesticides can result in acute toxicity (caused by a single exposure) or chronic toxicity (caused by long-term exposure) to aquatic plants, aquatic insects, and fish.  Over 180 of the 227 measured pesticides were detected in streams at low levels. However, relatively few of measured pesticides—atrazine, acetochlor, metolachlor, imidacloprid, fipronil, selected organophosphate insecticides, and carbendazim—were measured at levels likely to be major contributors to aquatic toxicity, according to aquatic life benchmarks and the PTI. The first three pesticides are widely used agricultural herbicides, the next three are insecticides used in both urban and agricultural settings, and the last is a fungicide breakdown product. At least one pesticide in more than half of the 100 streams sampled exceeded the concentration estimated to be toxic to aquatic invertebrates.  This study provided a short-term temporal assessment of currently used pesticides and their potential aquatic toxicity in agricultural and urban streams in the Midwestern U.S. The acute and sublethal effects of complex pesticide mixtures detected in this study on aquatic organisms are unknown.  This study will also be linked on the 2018 Reports Page 02 of the Sustainable Water Resources Site at https://sites.google.com/site/sustainablewaterresources/  Tim Smith, Sustainable Water Resources CoordinatorGovernment Web Site, https://acwi.gov/Sustainable Water Resources Site, https://sites.google.com/site/sustainablewaterresources/