Report: Harmful Pesticide Contamination Rampant in Minnesota Waters

A new report by Dr. Pierre Mineau finds that neonicotinoid pesticides ("neonics") are widespread in Minnesota surface waters at levels expected to harm aquatic life-and that pesticide-coated or "treated" seeds are largely to blame. The report draws from federal, state, and independent water testing data and highlights shortcomings in regulatory decision-making that likely place our aquatic ecosystems at risk.

Neonics are the most commonly used pesticides nationwide, and studies link even tiny concentrations of neonics in water with declines in bird populations and the collapse of fisheries.

For Minnesotans, the report underscores three main takeaways:

• Neonic contamination is severe and widespread in Minnesota. Of sampling sites regularly tested by the Minnesota Department of Agriculture, 95% contain neonics. This is consistent with independent testing finding at least one neonic in 97% percent of creek and river samples across the state.
  Contamination is frequently intense in areas of southeast Minnesota, like Austin, Pilot Mound, and Carimona. But intense contamination is found statewide, including Sauk Rapids, Stephen in northern Minnesota, and Wanamingo near the twin cities. Each shows astronomical neonic levels-at which even short-term contamination could cause serious harm to aquatic life.
• Seed treatments account for nearly all of this contamination. The report estimates that about a million pounds of clothianidin-a neonic chemical used almost exclusively as a seed coating-are used each year in Minnesota. Overall, neonic-treated seeds account for an estimated 96% of agricultural neonic use and 90% of all neonic use in Minnesota. In other words, we cannot address the harms of widespread neonic pollution without addressing these uses.
• Thresholds for harm established by U.S. EPA likely underestimate harm to aquatic life. The report notes that as EPA has gained more information about neonics, it has consistently found that neonics cause harm at lower and lower levels. However, EPA's thresholds or "benchmarks"-i.e., the amount of neonics in water that would cause harm to aquatic life-are still significantly higher than those set by regulatory bodies in Europe, where most outdoor neonic use has been prohibited since 2018. EPA's thresholds are frequently exceeded in Minnesota, but contamination even below these levels is likely causing harm.

The report's conclusions focus on harm to aquatic ecosystems, but they also have implications for human health because conventional water treatment largely fails to remove neonics from drinking water. Monitoring by the Centers for Disease Control and Prevention detected neonics in half of Americans' bodies from 2015-2016. Another study of 171 pregnant women between from 2017-2020 found neonics in 95% of women tested-with exposure worsening over the course of the study.

Two other recent studies highlight concerns about impacts of widespread exposure. The first finds that neonics have neurotoxic nicotine-like effects that EPA ignored when it was undertaking their initial safety analysis when approving neonics. The result is that the "safe" limits EPA set for neonics likely fail to protect people against these harms. The second reviews 842 poisoning reports collected by U.S. EPA, demonstrating neonics' neurotoxic effects in people-including seizures, headaches, dizziness, muscle weakness, and tremors. These build on an increasing body of evidence that neonic exposure presents widespread threats to human health.

The Minnesota legislature has considered bills in recent years to rein in the major, unnecessary sources of neonic contamination: treated seeds and lawn and garden uses. Last session, those bills failed to pass-but the 2025 session brings more hope that Minnesota's leaders will wake up and address this worsening crisis.

Critically, NRDC Action Fund and partners have also petitioned the Minnesota Department of Agriculture (MDA) to use its broad existing authority to develop a regulatory program to rein in use of neonic-treated seeds. Their response is due December 19^th of this year.

One way or another, as evidence of neonics' harms continue to mount, it is critical that Minnesota's leaders take action.

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