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Recent research conducted by scientists from the University of Minnesota Twin Cities, in partnership with the Minnesota Department of Natural Resources (DNR), has discovered alarming levels of certain insecticides known as neonicotinoids in some ground and surface water supplies. These findings raise potential concerns for drinking water safety.
People who depend on shallow groundwater or natural springs for their drinking water face a greater risk of exposure to these insecticides compared to those using deeper groundwater wells. The study also revealed that these chemicals could harm aquatic life in streams that are sourced from these springs.
This research was published in the peer-reviewed journal Science of the Total Environment.
Over the past several decades, the rising usage of insecticides for agricultural purposes has been linked to water contamination issues. This can pose significant risks to human health as well as non-target insect species, including bees and butterflies.
A significant portion of Minnesota’s water supply is sourced from groundwater. By analyzing the concentrations of neonicotinoids, water treatment facilities can better understand what needs to be monitored and filtered.
The study involved assessing the presence of neonicotinoids in surface and groundwater throughout Minnesota, focusing on the variables that could influence contamination levels. The DNR managed to obtain water samples from 15 springs and 75 distinct wells across 13 counties over a four-year period (2019-2022), enabling comparisons between urban and rural regions.
The researchers not only gathered data from a wide range of locations but also examined chemical concentrations at various depths. Their tests indicated that natural springs are particularly vulnerable to neonicotinoid contamination.
“Many people assume that water from a natural spring is safe to drink,” explained Bill Arnold, a Distinguished McKnight University Professor at the University of Minnesota in the Department of Civil, Environmental, and Geo-Engineering. “However, that isn’t always the case; it largely depends on the source depth of the water.”
There are several pathways through which these chemicals enter the environment. Aside from direct application, runoff from storms and melting snow can also lead to their presence in ground and surface waters. The researchers successfully mapped various classes of these insecticides across the state.
“This research represents an important initial effort to identify water pollutants, even in unexpected areas like natural springs,” Arnold stated. “In Minnesota, we utilize numerous insecticides—essentially every corn and soybean seed is treated before planting—and many of these products can be easily purchased at local hardware stores for purposes such as spraying fruit trees, controlling fleas and ticks in pets, or eradicating bedbugs.”
While researchers anticipated finding traces of the insecticide in water samples, some results were surprising.
“We were taken aback by the significant levels of neonicotinoids found in natural springs and, in some cases, even deeper well samples contained these chemicals at unexpected concentrations,” Arnold noted.
Following up on the study, researchers are working alongside county and state agencies to add these chemicals to water treatment monitoring protocols and aim to continue educating local watershed districts about neonicotinoids. They will also collaborate with the University of Minnesota’s St. Anthony Falls Laboratory to enhance stormwater treatment solutions for urban areas, particularly through biofiltration techniques for pollution removal.
Alongside Arnold, the research team included Paul Capel, a retired adjunct associate professor from the University of Minnesota’s Department of Civil, Environmental, and Geo-Engineering, former research assistant Grant Goedjen, and John Barry from the DNR’s Division of Ecological and Water Resources.
This project received funding from the Minnesota Environment and Natural Resources Trust Fund (ENTRF), as recommended by the Legislative Citizen Commission on Minnesota Resources (LCCMR). The ENRTF is a dedicated fund in Minnesota focused on supporting the conservation and protection of the state’s natural resources.
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