PMPC Meeting Agenda and Notes

Josh Stamper (MDA) welcomed participants to the meeting, explained purpose of the committee, and emphasized the importance of discussion and member feedback. PMPC Members and MDA leadership introduced themselves. 

Kate Hall (meeting facilitator, MDA) went through housekeeping items and presented background slides on PMPC. The presentation provided an overview of the MDA’s Pesticide Management Plan, “common detection” and “surface water pesticide of concern” designations, and meeting goals. The MDA’s Indigenous Land Acknowledgement statement was read.

Dave Tollefson (MDA) presented an overview of the MDA’s monitoring program and introduced the main sections of the 2025 Water Quality Monitoring Report. Groundwater and surface water program design elements were reviewed along with rainfall data and a broad detection summary for 2025.

Questions/Comments: 

• In response to a note about the method reporting limit (MRL) being lowered for methyl parathion, a member noted that there is no current use of methyl parathion in the U.S. The MDA confirmed that it is no longer registered for use.   

Kim Kaiser (MDA) and Brennon Schaefer (MDA) presented the groundwater results from the 2025 monitoring season. Current common detection pesticides were reviewed, and trend maps were presented showing changes in detection frequency and concentration for individual pesticide monitoring regions (PMRs). Data for select additional pesticides were highlighted including 4-hydroxychlororthalonil, cyanazine degradates, and several neonicotinoid insecticides.

Kate Hall (MDA) presented additional background on chlorothalonil and recent EPA actions (e.g., reducing allowable rates). MDA actions were also highlighted, including the publication of water quality best management practices (BMPs) for chlorothalonil and expanded monitoring efforts.

Discussion focused on: 

• Chlorothalonil use and common detection status
  • Chlorothalonil use and application rates on turf vs. potatoes were discussed. It was noted that use can largely vary depending on weather with less be applied in dryer years. 
  • A member asked why chlorothalonil is not in common detection status if MDA is already creating BMPs for it. The MDA noted that EPA actions on chlorothalonil have been a factor along with wanting to better understand the extent of detections in Minnesota and other states. 
  • A member asked if 4-hydroxychlorothalonil needs a Health Risk Limit (HRL) from the MN Dept. of Health to designate chlorothalonil in common detection status. The MDA explained that the existence of an HRL can be considered, but it is not required for the designation.
• Classification of 4-hydroxychlorothalonil as a “marginally performing analyte”
  • A member asked if the contract lab that analyzes private well samples for 4-hydroxychlorothalonil also considers has issues that make it a marginally performing analyte. The MDA explained that “marginally performing analyte” is an internal term used to describe analytes that fail to meet validation requirements. The MDA is not aware of any validation concerns with data from the contract lab. 
  • The MDA further explained that part of the reason analytical challenges can arise with 4-hydroxychlorothalonil is because the MDA is analyzing 4-hydroxychlorothalonil as part of a multi-residue method. When trying to simultaneously analyze a large number of chemicals, it can be difficult to optimize individual chemicals. 
• Trends in total cyanazine detections 
  • A member asked about the potential reason for the increasing trend in the 90th percentile total cyanazine concentration in Southeast MN (PMR 9). The MDA responded that while the trend is statistically significant, the actual 90th percentile concentrations are low and remain below the HRL. 
  • A member asked why we aren’t starting to see total cyanazine levels going down since cyanazine hasn’t been used in 20 years and why it is so persistent. The MDA responded that even though it hasn’t been used in many years, it can persist due to a combination of chemical properties and geology (e.g., old groundwater sampled). Total cyanazine includes the parent that was originally applied and its breakdown products. 
• Metolachlor detected concentrations
  • A member noted that the maximum detected concentration for metolachlor (65,100 ng/L) seemed high and asked if more information was available on the detection. The MDA did not have additional information on the detection during the meeting but followed up after. 
• Sulfentrazone detected concentrations
  • A member asked about the sulfentrazone detection above its reference value and whether it was related to a point source. The MDA responded that the exceedance was from a single well in eastern MN (PMR 5), and the MDA will continue to watch this site closely. It was also explained that sulfentrazone was included in the “additional pesticides” category based on its detection frequency. 
• Status of neonicotinoid-treated seed use data
  • A member asked if there has been any progress on getting more quantitative data on treated seed use in MN, specifically for neonicotinoids. The MDA replied that they are currently having discussions with registrants to try to get MN specific data.

Matt Ribikawskis (MDA) presented the surface water results from the 2025 monitoring season. Pesticide waterbody impairments were presented along with an overview of how Minnesota water quality standards are used to evaluate data. Current surface water pesticides of concern were reviewed, and trend maps were presented showing changes in detection frequency and concentration for individual PMRs. Comparisons of detected concentrations to relevant standards or guidance values (i.e., reference values) were also presented, focusing on pesticides detected at concentrations >10% and >50% of relevant reference values. Additionally, analyses of 21-day duration concentrations and detection seasonality were presented for the neonicotinoid (neonic) insecticides clothianidin and imidacloprid.

Kate Hall (MDA) presented monitoring highlights for acetochlor, chlorpyrifos, clothianidin, and imidacloprid and provided additional background on the MDA’s actions to mitigate detections in surface water. 

Discussion focused on: 

• Development of water quality standards for neonics
  • A member asked about the estimated timeline for the MPCA to develop water quality standards that could be used to evaluate neonic concentrations in surface water. It was explained that both clothianidin and imidacloprid were included in the MPCA’s Triennial Standards Review as candidates for rulemaking (i.e., standard development and adoption).
• Calculation of neonic 21-day average concentrations
  • A member suggested calculating a running 21-day average instead of only discrete preset 21-day timeframes to more thoroughly assess the data. The merits and challenges of changing the current method were discussed. It was noted that EPA had conducted daily monitoring of atrazine and, by comparison, MDA’s sampling after storm events appears to capture the key high-concentration data. 
• MDA’s public comment period on neonic-treated seed
  • A member asked for clarification on MDA’s request for comments and how the comments will be used. The MDA explained the specifics of the request and that a judge ordered the public comment period. It was noted that next steps will involve evaluating whether Minnesota Rule Chapter 1505 is adequate, taking into account the comments received. 
• Hydroxyatrazine detection frequency
  • A member asked about the detection frequency of hydroxyatrazine. It was noted that the 2025 detection frequency in surface water was 96%, but detected concentrations remain well below the reference value. 
• Atrazine detection trends in northwest MN
  • A member asked about potential explanations for the observed increasing trends in atrazine detection frequency and concentration in northwest MN (PMR 1). It was noted that one contributing factor may be that more corn is now being grown in the region which previously had more diverse crops. 
  • A member asked about atrazine sales and use in the region. The MDA responded that there has been a slight increase in statewide atrazine sales over the past decade.
• Regional pesticide sales data
  • A member asked if pesticide sales data is available for specific regions. The MDA explained that regional sales data can be generated, but there are challenges with sharing and using the data. For example, there may be data protection concerns depending on the number of sellers in a region, and pesticides sold in one county may not be used in that same county. 
• Chlorpyrifos water body impairments
  • A member asked if the water bodies being delisted as impaired for chlorpyrifos are likely to be re-listed as impaired. It was explained that the MN Pollution Control Agency makes impairment decisions based on exceedances of the standards. While impairments may reoccur, it is not necessarily likely. Some of the water bodies proposed for delisting were initially impaired based on a single exceedance of the acute standard. 

• Criteria used to select pesticide analytes for monitoring
  • A member asked what criteria are used to select analytes for monitoring. The MDA explained that it considers several factors including overall use, likelihood of reaching water, and toxicity. Newly registered active ingredients are also evaluated for potential inclusion. Detections by other states or organizations are also considered. 
• Detections of pesticides in tile drain water
  • A participant described an ongoing study monitoring for select pesticides in tile drainage and noted that clothianidin has been detected but not acetochlor. They asked if there is potentially due to the MRL (30 ppb). The MDA noted that it could share the methods being used by the MDA lab for acetochlor. It was also noted that acetochlor would not necessarily be expected in tile drainage because it quickly breaks down in soil. 
• Monitoring of trifluoroacetic acid (TFA)
  • A member asked if MDA has considered adding TFA to its monitoring program, noting that the MN Dept. of Health is developing a health-based guidance value for TFA and the increase in registration of fluorinated pesticides that can break down to form TFA. The MDA responded that they are not planning to add it into the program at this time. TFA can come from many sources besides pesticides, and it presents analytical challenges that would likely require a separate method. It was noted that the U.S. Geological Survey is conducting a nationwide project monitoring for both pesticides and TFA in streams.
• Private well testing
  •  A member asked when the 2025 private well testing report will be made available online. The MDA responded that it should be posted within the next few weeks. The Private Well Pesticide Sampling Project Data Summary Report, 2019-2025 has since been posted.
  • A member asked how many reverse osmosis treatment systems have been installed in Dakota County for private wells. The MDA responded that there have been 62 systems total, with 39 in the south metro. Upon further review, the MDA later confirmed that there were 69 systems total, with 15 installed in Dakota County.
• Meeting/report content and presentation
  • Two members requested that the total concentrations for additive parent and degradate chemicals be presented with the rest of the data rather than being included as an appendix.