By James V. Aidala and Dennis R. Deziel

The U.S. Environmental Protection Agency (EPA) announced on August 18, 2022, it released its draft ecological risk assessment for dicamba for a 60-day public review. 87 Fed. Reg. 50854. The 287-page assessment examines the potential ecological risks associated with currently registered uses of dicamba on non-target, non-listed species. Risks to federally listed threatened and endangered species are not evaluated in the assessment. EPA is reevaluating the risks of dicamba as part of a routine review process for pesticides that occurs every 15 years. Comments are due October 17, 2022. EPA expects to propose an interim decision regarding the reregistration of dicamba in 2023.

Dicamba is a systemic benzoic acid used primarily to control annual, biennial, and perennial broadleaf weeds. First registered in the United States in 1967, it is currently registered for use on a wide variety of agricultural crops, such as soybeans, cotton, corn, grains, and sorghum, as well as for non-agricultural uses, such as rangeland, fallow fields, turf, and residential premises.

The draft assessment focuses on areas where there have been updates since the most recent national-level risk assessments of dicamba by EPA (2005 and 2020) to examine if the risk picture has changed based on new data and analysis. The 2005 risk assessment was for dicamba’s Registration Eligibility Decision (RED) based on use patterns registered at that time, which were applications to non-dicamba-tolerant plants. The 2020 risk assessment was exclusively to evaluate risk associated with relatively new uses of applications to dicamba-tolerant plants (i.e., soybeans and cotton).

In general, the risk conclusions of the draft assessment are consistent with those identified in past national-level risk assessments for dicamba with a few notable exceptions:

• Lower Risks to Birds. The risk assessment incorporates recently submitted toxicity data (chronic toxicity to birds), information that eases previously identified chronic risk concern for birds in dicamba-tolerant plants.
• New Risks to Bees. Recently submitted toxicity data indicate a previously unidentified potential chronic risk concern for honeybees from all uses on non-dicamba-tolerant plants. EPA used application rates higher than those EPA evaluated in its 2020 assessment, and potential chronic risks to bees are based on weight-of-evidence and maximum single application rates. The uses with the greatest potential chronic bee risks are asparagus, soybean, dicamba-tolerant cotton, and any registered uses on unmaintained non-agricultural areas.
• Risks to Fish. Updated exposure estimates accounting for the combined residues of dicamba indicate a previously unidentified potential chronic risk concern for non-listed fish. Updated exposure estimates accounting for the combined residues of dicamba (dichlorosalicylic acid (DCSA) and 6-CSA, degradates of dicamba) indicate a previously unidentified potential chronic risk concern for non-listed fish from one use scenario.

Also of significance, there are thousands of reported incidents allegedly caused by dicamba exposure occurring at or near a wide variety of agricultural and non-agricultural use sites and affecting a wide variety of plant species. According to EPA, a pronounced increase in the overall number of reported dicamba incidents associated with damage to non-target plants started around 2016 and appears to link to the introduction of dicamba-tolerant plants and “over-the-top” (OTT) applications to those crops. The combined evidence from field studies and incident data indicates that there may be off-site movement of dicamba via runoff, spray drift, and volatility from the use of dicamba, particularly for OTT application on dicamba-tolerant plants.

Damage to plant species near areas of application presents two separate issues of concern that will have to be addressed in EPA’s eventual decisions:

1. Does routine OTT use of dicamba cause unacceptable damage to nearby commercial crops? and
2. Does any tendency to injure nearby plants represent a possible concern about possible impacts on threatened and endangered species when EPA eventually includes Endangered Species Act (ESA) assessments as part of its review?

In 2020, EPA concluded that its 2020 label restrictions of dicamba-tolerant plants would significantly reduce incident reports about damage to nearby crops. Despite the new control measures, EPA received nearly 3,500 incident reports for the 2021 growing season of damage to non-dicamba-tolerant soybean, numerous other crops, and a wide variety of non-target plants in non-crop areas, including residences, parks, and wildlife refuges. EPA continues to monitor and evaluate new incident report submissions, and the analysis will be updated as new information becomes available. Dicamba also continues to be an important issue of discussion at State FIFRA [Federal Insecticide, Fungicide, and Rodenticide Act] Issues Research and Evaluation Group (SFIREG) meetings where data, analysis, and recommendations for dicamba continue to be discussed.

Commentary

This is the first time dicamba has been identified to pose risks to bees and fish. Worth noting, the identified chronic risks to honeybees, which could indicate that dicamba affects the larvae stage as well as the adult stage of bees, in a time of increased attention to bee health, throws dicamba into another arena of controversy previously unidentified and could garner significant attention in the environmental community, industry, and EPA.

Still, the most significant risk continues to be to possible impacts on non-target terrestrial plants from spray drift and volatilization. Almost 3,500 incident reports for a single growing season are hard to ignore. EPA has received numerous complaints about dicamba damaging non-target plants since EPA allowed the herbicide OTT application on genetically modified soybeans and cotton in 2016. Spraying dicamba over the top of crops after they have emerged is typically done later in the growing season, when temperatures are hotter and other crops/plants are maturing in nearby areas. In warmer temperatures, the herbicide is more likely to volatilize from target application areas and drift, also because of the warmer temperatures. Environmental groups sued EPA to halt the approval, and a federal appeals court ordered EPA in June 2020 to cancel all registrations for use on dicamba-tolerant crops.

In October 2020, EPA issued new registrations with new controls intended to reduce and prevent dicamba movement from volatilizing and drifting onto neighboring properties. Based on the most recent incident reporting, however, the measures did not stop the complaints about harm to nearby crops, plants, and trees.

This draft ecological risk assessment puts dicamba under scrutiny once again and may signal important registration challenges for the herbicide in 2023.

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By Susan M. Kirsch

On September 30, 2019, the U.S. Environmental Protection Agency (EPA) released an updated Aquatic Life Benchmarks Table for registered pesticides.  The update includes four newly registered pesticides and their degradants as well as new values for more than 30 previously registered pesticides. The benchmarks inform state and local regulators in their interpretation of water quality monitoring data. Waterbodies where benchmarks are exceeded may be prioritized for further investigation.  EPA derived the latest updates from toxicity values from the most recent ecological risk assessments for the registered pesticides as part of the regular registration review. EPA aims to update the table on an annual basis.  The full table and links to source documents for each of the benchmarks are accessible on EPA’s website here.

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By Lisa M. Campbell and Timothy D. Backstrom

On September 9, 2019, the U.S. Environmental Protection Agency (EPA) Office of Pesticide Programs (OPP) published a notice in the Federal Register announcing the availability of, and an opportunity for comment on, a document describing an “interim process” that OPP’s Environmental Fate and Ecological Effects Division is currently using to evaluate potential synergistic effects of mixtures of pesticide active ingredients on non-target organisms. As part of a lawsuit challenging the 2012 decision by EPA to register Enlist Duo Herbicide (a combination of 2,4-D and glyphosate), OPP scientists learned that patent applications for some registered pesticide products included claims that particular combinations of active ingredients provide “synergistic” control of target species.  Although EPA was not at that time considering potential synergies in assessing the risk for ecological effects on non-target organisms, based on the patent application claims regarding synergy for Enlist Duo, EPA decided to request that the reviewing court vacate its registration decision and remand the application for Enlist Duo for further study of these effects and any measures that might be needed to mitigate the risk to non-target organisms.  This decision sparked much controversy, and many in industry were concerned that patent application claims were not being correctly interpreted by EPA for the category of pesticide products at issue.

The new document released by EPA for review and comments is entitled: “Process for Receiving and Evaluating Data Supporting Assertions of Greater Than Additive (GTA) Effects in Mixtures of Pesticide Active Ingredients and Associated Guidance for Registrants.”  EPA states that it “has generally been applying this interim process since 2016.” The process described in the document has five steps: (1) registration applicants must search for any granted patents that include synergy (GTA) claims for combinations of pesticides; (2) applicants must review the patent claims and supporting data for relevance to ecological risk assessment; (3) applicants must report to EPA all effects testing data from the relevant patents; (4) applicants must do a statistical analysis (using a method prescribed by EPA) to determine whether any observations of GTA effects are statistically significant; and (5) EPA will review all submitted information to decide whether it should be utilized in ecological risk assessment.

In the Federal Register notice, OPP lists five specific areas pertaining to the interim risk assessment process described in the document on which it is requesting comment:

• Are there technical aspects of the interim process that warrant change? If so, what changes are recommended?
• What aspects of the process could be applied to the evaluation of open literature sources of GTA effects pesticide interactions?
• Should EPA consider standardizing a more detailed search and reporting approach, and how should EPA do that?
• Should EPA continue the evaluation process as described in this document? If so, what performance metrics (e.g., number of evaluations) should EPA consider before deciding the utility of this approach?
• What applicant burden is associated with the activities described in this memorandum, including compiling, analyzing, and submitting the information? Specifically, does an estimate of 80-240 hours of burden per applicant cover the respondent burden associated with the interim process?

When the National Research Council (NRC) evaluated the importance of toxicological interactions between pesticide active ingredients in 2013, the NRC concluded that such interactions are rare, but that EPA should nonetheless consider such interactions when the best available scientific evidence supports such an evaluation.  In the current Federal Register notice, EPA makes it clear that it is uncertain concerning the utility for risk assessment of the information used by manufacturers to support synergistic effects claims in pesticide patents.  According to EPA, 24 applicants for new registrations have submitted patent data to date, but only three of these submissions contained information that indicated a need for further testing and no submission ultimately led to any adjustment of the ecological risk assessment.  At this juncture, EPA will continue collecting patent data that may be pertinent to GTA effects, but when it has sufficient experience upon to base a general policy it may either continue or improve this process or discontinue it after explaining why.

Commentary

When EPA requested that the reviewing court vacate and remand the registration EPA had granted for Enlist Duo, the parties seeking judicial review located data in the patent applications that EPA had not previously seen or reviewed and that EPA believed could possibly be pertinent to potential adverse effects on non-target plants.  EPA concluded that it should revisit the decision based on the additional data.  Although EPA decided to request vacatur and remand, the applicant Dow AgroSciences had arguably followed all of the procedures then in place, because FIFRA Section 3(c)(5) allows EPA to waive data requirements pertaining to efficacy, and EPA typically registers pesticide product that are not intended to protect public health without any independent evaluation of efficacy data.  Nevertheless, in general EPA may choose to evaluate pesticidal efficacy data; such circumstances in the past often involved cases where EPA was required to consider whether pesticide benefits are sufficient to outweigh identified risks.  In the Enlist case, EPA determined that it should do so where potential synergy in pesticidal efficacy is pertinent to evaluating ecological effects on non-target species.

What EPA must decide now is how often efficacy data that has been deemed adequate by the Patent and Trademark Office to support a patent for a new pesticide mixture will have any material significance in the context of ecological risk assessment.  Before EPA makes a determination whether or not patent data has sufficient pertinence to continue requiring routine collection and evaluation of such data, EPA has decided it is prudent to afford all stakeholders an opportunity to comment on whether EPA has been asking the right questions.

All comments on the draft document must be submitted no later than October 24, 2019.

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