In 1987, the Minnesota Legislature amended the Minnesota Pesticide Control Law (MN Statute 18B.04). It directed the MDA to determine the impact of pesticides on the environment, including the impacts on surface water and groundwater.
In response to this charge, the MDA initiated a pesticide groundwater monitoring program in 1987. In 1991, surface water monitoring began. The MDA also conducts edge-of-field water quality monitoring for nutrients and sediment. The MDA has one of the most comprehensive pesticide monitoring programs in the country.
Surface Water Monitoring Results for 2021
The MDA’s ambient surface water monitoring focuses on pesticide sample collection from rivers and streams around the state. In 2021, the MDA collected 864 pesticide samples from 55 rivers and stream locations.
- The MDA analyzed for 181 pesticides and pesticide degradates in 2021.
- Seventy-three pesticide analytes were detected at least once.
- Forty-eight pesticide analytes were detected in 10% or less of the samples.
- The herbicides 2,4-D, metolachlor, and atrazine were detected in 83%, 54%, and 52% of samples, and all detections were below the applicable reference values.
- Degradates of the herbicides atrazine, metolachlor, and acetochlor were detected in over 66% of the samples in 2021, and all detections were below the applicable reference values.
- Acetochlor was detected in 28% of the samples in 2021, with two detections collected from different streams over the numeric chronic standard (3,600 ng/L)
- Chlorpyrifos was detected in five samples collected from four streams in 2021, including one detection over the maximum standard (83 ng/L) and three detections over the chronic standard (41 ng/L).
- Clothianidin and imidacloprid were detected in 8% and 15% of the samples, respectively.
- Forty-six detections were above an applicable numeric water quality reference value, including
acetochlor (2), chlorpyrifos (4), clothianidin (13), diuron (4), imidacloprid (21), and malathion (2).
- All detections above an applicable numeric water quality reference value require a duration assessment to determine if both the numeric and duration component of the reference value was exceeded to fully assess risk to aquatic life.
- Minnesota water quality standards are available for acetochlor and chlorpyrifos. The Minnesota Pollution Control Agency (MPCA) will assess the water quality data, as well as the concentration duration, for any applicable MN Ch. 7050 standard violations.
- Pesticides without state standards in the above list (clothianidin, diuron, imidacloprid, and malathion) were compared to U.S. Environmental Protection Agency (USEPA) aquatic life benchmarks.
- Glyphosate was detected in 4% of the samples, and the maximum glyphosate detection (1,760 ng/L) was less than 1% of the lowest water quality reference value.
- Bentazon AIBA, piperonyl butoxide, and Imazamethabenz-methyl were detected for the first time in Minnesota surface water, and all were detected in less than 1% of samples in 2021.
- Five pesticides are designated as "surface water pesticides of concern" by the Commissioner of Agriculture.
Surface Water Pesticides of Concern
The Commissioner of the MDA may designate a pesticide as a “surface water pesticide of concern” in accordance with the state Pesticide Management Plan. Currently, there are five pesticides with the “surface water pesticide of concern” designation:
For more information on this designation and the supporting resources for the determination to designate clothianidin and imidacloprid, visit the surface water pesticides of concern page.
Surface Water Pesticide Impairments
Minnesota pesticide impairments for currently registered pesticides.
|Pesticide||Impaired Waters List Year||Stream||County||Violation that Resulted in Impairment|
|Acetochlor||2016||Silver Creek||Carver||chronic (3,600 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2018||Beauford Ditch||Blue Earth||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2018||Beaver Creek||Murray||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2022||Bevens Creek||Carver||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2018||Chetomba Creek||Renville||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2020||Double Lake||Cottonwood||chronic (41 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2016||Dry Weather Creek||Chippewa||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2020||Dutch Creek||Martin||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2018||Jack Creek||Jackson||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2018||Lac qui Parle River||Lac qui Parle||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2018||Sleepy Eye Creek||Redwood||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2014||Tamarac River||Marshall||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2020||Three Mile Creek||Lyon||maximum (83 ng/L) Minnesota water quality standard|
|Chlorpyrifos||2020||Yellow Medicine River||Yellow Medicine||maximum (83 ng/L) Minnesota water quality standard|
Four waterbodies have been removed from the USEPA 303(d) Impaired Waters List for currently registered pesticides. The Le Sueur River and Beauford Ditch were designated as impaired for acetochlor in 2008 and were removed on the 2014 Impaired Waters List. Seven Mile Creek was designated as impaired for chlorpyrifos on the 2012 Impaired Waters List and was removed on the 2018 Impaired Waters List. Grand Marais Creek was designated as impaired for chlorpyrifos on the 2014 Impaired Waters List, updated on the 2016 Impaired Waters List and was removed on the 2022 Impaired Waters List. Removal from the USEPA 303(d) Impaired Waters List occurred after several years of water quality monitoring without pesticide detections above the applicable standard.
Visit the MPCA Minnesota Impaired Waters List for more information.
Chlorpyrifos Response Plan was developed in response to continued detections of chlorpyrifos in rivers, streams and lakes and the determination of chlorpyrifos water quality impairments of rivers and streams in agricultural areas of Minnesota.
Data Availability and Future Work
All of the pesticide data collected as part of the MDA's ambient monitoring program is publicly available through the Water Quality Portal or by contacting the MDA. The MDA will continue to improve its program to expand monitoring to new locations and to include additional pesticide analytes, as resources and needs permit. The MDA is committed to maintaining its long-term data record to allow for continued assessment of the impacts of pesticides on surface water from routine use.