24
Jan
Study Finds Waterway Contamination with Neonicotinoid Insecticide Threatens Aquatic Ecosystems and Biodiversity
(Beyond Pesticides, January 24, 2025) Based on data collected from government sources and independent monitoring, a multidisciplinary team of researchers at the University of Connecticut find that 46% of Connecticut waterway samples are contaminated with levels of the most widely the neonicotinoid insecticide, imidacloprid—one of the most widely used insecticides in the United States on lawn and golf courses.
The authors relied on federal data from U.S. Environmental Protection Agency (EPA) and U.S. Geological Survey (USGS), state-level data from Connecticut Department of Energy and Environmental Protection (CT-DEEP), and a small-scale data collection study by the Clean Rivers Project funded by the nonprofit Pollinator Pathway, Inc. In their report, Neonicotinoids in Connecticut Waters: Surface Water, Groundwater, and Threats to Aquatic Ecosystems, the researchers provide the most comprehensive view to date of neonicotinoid levels in Connecticut and offer critical recommendations for future testing within the state and nationally, given glaring data gaps.
It is important to note that the authors acknowledged early in the report the “abandonment” of Integrated Pest Management in “the use of neonicotinoids has coincided with and been implicated in the decline of many non-target species of insects, in particular pollinators such as bees () and monarch butterflies.”
They point out that the use of this systemic pesticide, typically incorporated into seeds and then integrated into the vascular system of plants and expressed through their pollen, nectar, and guttation droplets, constitutes the “abandonment” of a basic principle of Integrated Pest Management (IPM), “an approach predicated on minimizing the use of chemical pesticides in favor of pest monitoring and pesticide application only when necessary (Metcalf and Luckmann, 1994).”
IPM has been highly criticized as a land management system because it lacks a uniform definition, is not limited to least-toxic pesticides, and provides no enforcement mechanism, key elements incorporated in organic certification. (See Beyond Pesticides’ Parks for a Sustainable Future program—a novel initiative that works with land managers across the nation looking to move to organic practices and principles that replace chemical-intensive practices with pest prevention and management strategies, incorporating soil science and the natural cycling of nutrients.)
Advocates, organic farmers, farmworkers, physicians, and community leaders alike welcome science-based and criteria-driven solutions to avoid pesticide industry greenwashing or co-optation of climate solutions to perpetuate the use of toxic products, as has been made evident with the failure of IPM to eliminate hazardous pesticide use, climate-smart agriculture and carbon markets (See Daily News here), and regenerative agriculture. (See Daily News here.)
Background and Methods
The three authors of this study, Steven J. Presley, PhD, Cristopher R. Perkins, MS, and Michael R. Willig, PhD, are research specialists in environmental science, biology, and ecology at the Center for Environmental Sciences and Engineering and Institute of the Environment at University of Connecticut. The existing data, as referenced above, comes from a variety of federal and state-level agencies, however there was also some original data gathering.
CT-DEEP collected data on macroinvertebrates along the Norwalk River between 1989 and 2020. USGS data was collected from October 2001 to January 2024 testing for imidacloprid levels in 600 surface water and 62 groundwater samples from across the state. Surface and ground water testing has not been consistent over the decades on record, leading to support for the 2024 Clean Rivers Project in the southeastern region of the state.
The goal of this small-scale study was “to detect and quantify the presence of six neonicotinoids (i.e., nitenpyram, thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) in surface waters adjacent to large expanses of manicured lawns such as golf courses, which commonly use neonicotinoids to control pests that damage turf.” (See The Clean Rivers Project Neonicotinoid Data section on pages 8 to 9 of the report for more information.)
Funding for this data gathering, particularly the 2024 Clean Rivers Project, came from various sources including a grassroots fundraiser led by CT Pollinator Pathway and contributions from Sustainable CT, National Resources Defense Council, and Friends of the Earth. Norwalk River Watershed Association and East Norwalk Blue are credited with gathering water quality samples for the 2024 Clean Rivers Project. (See Acknowledgments section on page 3 of the report for more details.)
The UConn authors focus on imidacloprid concentrations in aquatic systems for numerous reasons documented in the report. Imidacloprid was the only neonicotinoid detected in the 2024 Clean Rivers Project, the only neonicotinoid for which USGS has publicly available data, the “single most commonly used insecticide in the world,” and an expansive listing of uses across agricultural and non-agricultural contexts.
Aquatic systems were chosen given the importance of marine ecosystems for the New England economy. They were also selected since EPA has acute and chronic benchmarks for freshwater aquatic invertebrate exposure to insecticides.
The researchers identify five main goals for their report:
- “Determine long-term and seasonal patterns of the frequency of imidacloprid occurrence in surface and ground waters of Connecticut;
- Determine seasonal variation in imidacloprid concentration in Connecticut waters;
- Determine spatiotemporal variation in imidacloprid concentration in Connecticut surface water and groundwater;
- Leverage long-term sampling from a site in the Connecticut River from northern Connecticut (Thompsonville) as a case study to evaluate long-term patterns in imidacloprid concentration that reflect impacts from a “light urban” region that contains urban, forested, and agricultural areas in Massachusetts that flow south into Connecticut; and,
- Use the Norwalk River, a watershed with relatively little agriculture, as a case study to evaluate long-term trends in imidacloprid concentration from nonagricultural outdoor sources, and long-term trends in aquatic macroinvertebrate richness and abundance.”
Main Conclusions and Recommendations
Long-Term and Seasonal Patterns: Frequency of Imidacloprid Occurrence
Researchers find that the frequency of imidacloprid detection in Connecticut waterways increased in surface waters but “show[ed] no significant temporal trend in groundwaters.” Beginning after the 2012 sampling period, “46% of samples collected since 2012 have detected imidacloprid, with at least half of the samples testing positive for imidacloprid during 5 of the past 9 years.” It is important to note that groundwater testing for neonicotinoids has not been tested since 2017, which exacerbates the researchers’ concern over “the ability of neonicotinoids to persist for extended periods of time when not exposed to sunlight.”
See Daily News here for related analysis of pesticide contamination in water wells in Wisconsin for lessons to be learned on improving groundwater detection of pesticides.
Seasonal Variation in Imidacloprid Concentration
Similar to the previous section’s results, imidacloprid detection in Connecticut surface water corresponds with the “seasonal applications of neonicotinoids for agriculture and for turf grass management (e.g., lawns and golf courses.)” Average imidacloprid concentrations in June and July are found to be “six times greater than the USEPA freshwater aquatic chronic benchmark.”
Groundwater sampling is deemed “insufficient” to determine seasonal trends.
Where in Connecticut is Imidacloprid Most Concentrated?
Researchers find imidacloprid concentrations increasing closer to Connecticut coastal waterways. “In contrast, there is no significant pattern of imidacloprid concentration going from east to west in the state, there are no significant differences between water sources (surface versus ground water), and there is no interaction between water source and time or between water source and space,” the researchers write. They suggest that the concentration of imidacloprid in the eastern parts of the state “is greatest in agricultural and suburban areas, and the proportion of area represented by the combination of agriculture and suburban developments increases toward the coast, with northern areas often being highly forested, which is a habitat type in which the use of neonicotinoids is uncommon.”
The researchers raise concerns that groundwater along the Connecticut coast “has rarely been tested for imidacloprid.”
The Thompsonville Case Study
The USGS site in Thompsonville tested for imidacloprid concentration from water wells in the Connecticut River Basin, finding “no significant temporal change in groundwaters, but with decreasing mean imidacloprid concentration in surface waters.” Researchers attribute these contrasting results with several factors including,
- Samples were only collected in 2003 and 2017;
- The first year of sampling incorporated skewed data that was otherwise corrected for each consecutive year (2013-2023) for EPA chronic benchmark criteria; and,
- Reliance on inconsistent access to private wells for groundwater data
The Norwalk River Case Study
“Importantly, the 2024 data from the Clean Rivers Project represent the only targeted sampling for neonicotinoids in Connecticut, with water samples taken specifically when (July and August) and where (near manicured turf grasses) one would expect to find high concentrations of neonicotinoids,” the researchers reflect on the implications of data gathered through the 2024 Clean Rivers Project. “This suggests that targeted sampling of areas (e.g., waters near row crops such as corn and soybeans, near golf courses, or near suburban areas with manicured lawns) during the summer months is more likely to reflect the current presence of neonicotinoids than are the data that are currently provided by the USGS.”
Upon reflection of the various datasets, researchers arrive at the following recommendations that can set the tone for neonicotinoid insecticide regulations in the state of Connecticut moving forward:
- “Execute synoptic sampling (coordinated sampling in space and time) of neonicotinoid concentrations and macroinvertebrate abundance and richness;
- Expand the geographic sampling to include little studied areas of Connecticut (e.g., northwestern and eastern portions of the state);
- Increase the testing of ground water and well water for neonicotinoids, as these water sources are under-represented in the available data and may relate more intimately to human health concerns;
- Amplify testing to include samples of sediment, which may represent areas of contaminant accumulation and exposure for some benthic species;
- Enlarge the suite of neonicotinoids whose concentrations are being monitored throughout the state, including newer generation compounds such as cycloxaprid, imidaclothiz, paichongding, sulfoxaflor, guadipyr, and flupyradifurone;
- Implement before and after studies that focus on known pesticide application periods and major rainfall events to gather data that are relevant to possible acute levels of neonicotinoids;
- Explore the extent of sub-lethal effects of neonicotinoids on insects that include characteristics related to demographics such as emergence times, size at emergence, and proportion of individuals that reach maturity;
- Consider banning the use of seeds treated with neonicotinoids;
- Recommend the use of alternatives to neonicotinoids, including biological control and natural products, where feasible;
- Where non-toxic alternatives are not feasible, recommend the use of non-neonicotinoid insecticides such as chlorantraniliprole, which have low toxicity to bees, though they are toxic to aquatic invertebrates and butterflies; and,
- Conduct testing of effects of neonicotinoids on aquatic larvae in areas that are used for shellfish production. Many shellfish producers seed their oysters in the brackish areas near the mouth of large rivers, including the Quinnipiac River.”
Environmental and public health professionals resonate with these recommendations as they take to heart the importance of applying the precautionary principle in the regulatory review process, while simultaneously proposing crucial starting points for additional future research on neonicotinoid contamination, sampling sources (i.e. well water and groundwater sources), more aquatic animal populations such as shellfish, and factors such as “sublethal” exposure or accounting for recent rainfall.
Neonicotinoid Regulations in Review
Policymakers, by the consistent and decades-long urging of dynamic coalitions and communities within the state, have already taken strides in protecting the public from petrochemical-based pesticide exposure. Branford, Greenwich, Stamford, and Norwalk are several examples of the cities that have moved toward organic land management and/or pesticide bans in the spirit of protecting children’s public health. In the past several legislative sessions, there have been bills in the state legislature calling for restricting neonicotinoid insecticides. (See here previous testimony from 2024 legislative session submitted to Joint Environment Committee.) Beyond Pesticides will continue to monitor for future actions this session.
The U.S. regulatory review process for uses of neonicotinoid insecticides has failed to consider numerous studies linking neonicotinoid insecticide exposure to adverse health effects, including breast cancer, nervous system impacts, irritable bowel syndrome (IBS), neurological impacts, heightened risk of obesity, and transferability between mother and fetus. Neonicotinoid applications have been linked to elevated hazards to honeybee populations. Neonicotinoid-treated seeds have been linked to precipitous declines in bird and monarch butterfly populations. Meanwhile, studies have exposed the shortcomings of EPA’s ecological risk assessment process and the broader pesticide risk assessment process.
The chemical Industry will continue to intervene in the regulatory process, as was made evident last month by investigative reporters from Canada’s National Observer, which found pesticide manufacturer Bayer colluded with environmental and public health regulators to reverse Canada’s proposed neonicotinoid insecticide ban originally introduced in 2018. (See Daily News here.)
Take Action
Several states, including Vermont and New York in 2024, have taken actions to restrict the use of neonicotinoid insecticides across certain uses. Advocates expect more bills to be introduced in various state legislatures this year to address the biodiversity, public health, and climate implications of the continuous use of neonicotinoids, neonicotinoid-treated seeds, and systemic pesticides.
See recent Daily News here on the impacts of neonicotinoid insecticides on monarch butterfly populations in North America. Take action today by telling the U.S. Fish and Wildlife Service to finalize its proposed listing of monarchs as threatened.
For a deeper dive, see Poisoned Waterways: The same pesticide that is killing bees is destroying life in the nation’s streams, rivers, and lakes.
Source: University of Connecticut
