22
Aug
USGS Report Shows Dozens of Pesticides Consistently Found in Midwestern Streams, Underscoring the Need for Organic Practices
(Beyond Pesticides, August 22, 2017) Streams in the Midwestern U,S. are polluted with complex mixtures averaging over 50 pesticides each, according to a U.S. Geological Survey (USGS) report published earlier this month. This is the latest and also most extensive study on pesticide contamination in U.S. streams to date. The shocking results put many aquatic plants and animals at existential risk, leading health and environmental advocates to ask how the federal government can continue to permit U.S. streams to be used as a mixing bowl for toxic pesticide compounds.
Each week between May and August of 2013, USGS sampled 100 streams located in 11 Midwestern states for 228 pesticides and their breakdown products. Based on site location, 88 of these streams are considered agricultural, while 12 are considered urban. “About 150 million pounds of pesticides are applied annually in the Midwestern U.S.,” said Lisa Nowell, PhD, research chemist and lead scientist on the study. “Understanding which pesticides are occurring at levels potentially toxic to aquatic life, and where they occur, is crucial to informing management decisions.”
Of the 1,200 samples collected over the study’s 12 week period, scientists detected 183 pesticide compounds (98 of the 124 herbicides tested, 71 of the 88 insecticides, and 14 of the 16 fungicides). In general, herbicides were detected more often and at higher concentrations than fungicides or insecticides. The study noted detections of atrazine, metolachlor, and acetochlor herbicides more often in agricultural streams, and glyphosate, 2,4-D and prometon more often in urban areas. That being said, glyphosate was still found to be widespread – in 63% of urban sites, compared to 41% of agricultural sites. Insecticides and fungicides were more prevalent in urban than suburban areas. Notably, the fungicide carbendazim, often incorporated into paints, adhesives, textiles, and other building materials, and also a breakdown product of thiophanate methyl, a chemical used on turfgrass and ornamental shrubs, was detected in roughly 95% of all urban site locations.
Mixtures of multiple pesticides were detected in all but 1 of the 1,200 samples USGS scientists tested. Each sample tested contained a median number of 25 compounds, and overall each site contained 54 pesticide compounds per stream.
Using Environmental Protection Agency (EPA) ecotoxicity reference values for individual compounds, and a screening tool called the pesticide toxicity index for mixtures, researchers estimated harm to aquatic insects and plants. Results show that in over half the streams sampled, at least one pesticide surpassed levels considered toxic for aquatic insects when chronically exposed. In 25% of streams, there were found to be between two and four pesticides compounds that exceeded aquatic invertebrate chronic toxicity thresholds. In general, chronic and acute aquatic toxicity thresholds were exceeded more often in urban sites (75% and 33,% respectively), than sites with medium to high agricultural activity (52% and 10,% respectively). Despite the range of tools available to researchers to determine toxicity, the study ultimately notes that, “The impacts of concurrent exposure to multiple pesticides at chronic effect levels are unknown.”
USGS has consistently been at the forefront of scientific research investigating the presence of pesticide contamination in U.S. waterways. The agency’s Pesticide National Synthesis Project catalogues these data, and presents maps of estimated annual agricultural pesticide use throughout the country. A study published in 2016, for instance, provided a snapshot of the current study, finding neonicotinoid pesticides widespread in U.S. waters. Research published in collaboration with the U.S. Fish and Wildlife Service in 2016 linked the prevalence of pesticides in wildlife refuges in the Northeast to the rise in bass with intersex characteristics.
This current research is the first in a five part series of stream quality assessments that will also include the Southeast, Pacific Northwest, Northeast, and California. The prevalence of tens of different pesticides in the majority of streams in both urban and agricultural areas points to a need to rethink current pest management approaches. By moving to organic practices on farms and in urban and suburban landscapes, toxic pesticide use can be drastically reduced. With little indication that EPA will incorporate this concerning data into their current assessment framework for pesticides, it is up to state and local governments, forward-looking farmers and businesses, and local advocates to enact these needed changes.
Source: USGS Press Release
