PMPC Meeting Agenda and Notes

Josh Stamper, MDA, welcomed participants to the meeting, explained the 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 select comments received from members the previous year. The MDA’s Indigenous Land Acknowledgement statement was read.

MDA Presenter: Dave Tollefson

The presentation provided an overview of the MDA’s monitoring program and introduced the main sections of the 2024 report. Changes to the 2024 analyte list were highlighted along with groundwater and surface water program design elements.

Questions/Comments: 

• A member asked if the MDA has looked at the effectiveness of reverse osmosis (RO) in removing any other herbicides beyond cyanazine and if it recommended for drinking water wells with elevated concentrations of 4-hydroxychlorothalonil. The MDA noted that RO is effective for many pesticides; however, the MDA does not have data on the effectiveness of RO for 4-hydroxychlorothalonil specifically. 

• A member asked whether there was specific guidance for comparing detected concentrations to health-based guidance values when evaluating pesticides for common detection status. The MDA explained that the guidance in the Pesticide Management Plan lists several factors to consider in evaluating a pesticide for common detection status, including concentration. However, no specific thresholds are given (e.g., 50% of a reference value). The member expressed a need for more clear language about considering concentrations with respect to health-based values.

• A member noted that the Pesticide Management Plan deals with water but ignores the nonaquatic environment despite the impacts of pesticides on land. The MDA clarified that the Pesticide Management Plan and the PMPC, which was established by the plan, is intentionally focused on water quality and that impacts of pesticides outside this context is beyond the scope of the meeting. 

MDA Presenter: Kim Kaiser

The presentation focused on the groundwater results from the 2024 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). Highlighted topics included: pesticides detected in PMR 4 (Central Sands), detections of 4-hydroxychlororthalonil and neonicotinoids, and detections of cyanazine degradates in private wells.

Following the main presentation, Kate Hall briefly shared additional background on chlorothalonil and recent EPA actions (e.g., reducing allowable rates). MDA actions being taken to better understand and address detections of the chlorothalonil degradate, 4-hydroxychlorothalonil, in groundwater were also highlighted (e.g., expanding monitoring, developing best management practices).

Discussion focused on:

• How pesticide use patterns relate to groundwater detections

• When concentrations of parent and degradate compounds should be treated as additive

• The ecological effects of atrazine and cyanazine and historical concerns

  • Historical concerns over atrazine’s effects on frogs were discussed along with the data supporting/not supporting the claims. The MDA noted that it previously conducted a special registration review on atrazine that goes into more detail on its potential ecological effects. 

• Use of the 90th percentile value in evaluating concentration data and trends

  • A member asked about the use of the 90th percentile concentration evaluating concentration data. The MDA explained that the 90th percentile concentration was selected for trend analysis due to the variability of the data; maximum concentrations also are evaluated separately along with any individual detections that exceed a reference value. 

  • It was suggested that the MDA evaluate concentration data using the 95th percentile values instead of 90th percentile values, and the MDA agreed to consider this. 

• The reference value used to evaluate 4-hydroxychlorothalonil concentrations

  • A member asked if a Health Risk Limit (HRL) could be developed in place of the current Risk Assessment Advice (RAA) for chlorothalonil. The MDA explained that a HRL was requested; however, MDH was only able to develop RAA for the chemical due to limitations with the available toxicity data. The MDH representative further elaborated on the development and use of the RAA value.

• Impacts of high rainfall on the groundwater well network

  • A member commented that we had above average rainfall in much of the state in 2024 and asked how that may have impacted the groundwater well network. The MDA replied that impacts can vary by region and that the groundwater network is relatively stable regardless of precipitation (compared to surface water). 

MDA Presenter: Matt Ribikawskis & Dave Tollefson

The presentation focused on the surface water results from the 2024 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) also were 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.

Following the main presentation, Kate Hall briefly reviewed monitoring highlights for acetochlor, 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 by the Minnesota Pollution Control Agency (MPCA) and the current use of Environmental Protection Agency (EPA) aquatic life benchmarks as guidance to evaluation detected concentrations

  • 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).

  • Another member asked if water quality standards create additional regulations. The MDA explained how it uses the EPA aquatic life benchmarks as guidance, but water quality standards are required to list a waterbody as impaired. Waterbody impairments initiate the total maximum daily load process by the MPCA or the development of response plans for targeted inspections, education, and possible restrictions by the MDA.

• Status of aquatic insects in neonic-impacted streams and the coordination of aquatic invertebrate monitoring with pesticide monitoring

  • A member asked about how aquatic insects are doing in neonic-impacted streams and whether there is any data of note. A toxicologist from the MPCA, which conducts aquatic invertebrate monitoring, responded that there is nothing conclusive yet, but there appear to be some trends. The MDA added that not a lot of the pesticide monitoring stations are at the same location as invertebrate monitoring, but they are working on trying to get more coordinated data. 

• Evaluating the effectiveness of the MDA’s voluntary clothianidin/imidacloprid best management practices (BMPs) and the general timeline for when effects may be measurable

  • A member asked what the MDA’s plan and timeline is to evaluate the effectiveness of the water quality BMPs for clothianidin and imidacloprid that were published in February 2023. The MDA replied that they do not have a specific timeline but are continuing to track trends and promote the BMPs. 

  • A member asked how long it typically takes to see changes in surface water detections and concentrations after BMPs are published. The MDA explained that it can take years depending on the nature or use and outreach, and impacts can also be site specific. 

• The contribution of neonic-treated seed to detections of neonics in surface waters

• Regulatory authority over neonic-treated seeds and options for regulatory action 

  • The complexity of regulating treated seed at the state level was discussed. It was noted that certain decisions are up to the commissioner, and a recent audit of the MDA’s pesticide programs requested that the legislature address treated seeds. 

• Monitoring of per- and polyfluoroalkyl substances (PFAS) and Minnesota’s regulation of intentionally added PFAS in pesticide products

  • A member asked if the MDA would begin monitoring for PFAS. The MDA noted that a handful of the active ingredients and degradates monitored would be considered PFAS under Minnesota’s definition. Regulations surrounding intentionally added PFAS in pesticide products were explained along with the opportunity for currently unavoidable use exemptions. Additional information is available on the MDA’s PFAS website and in the MDA’s report to the legislature on PFAS in pesticides.