EPA Makes Draft Risk Assessments Available for Dicamba as the Next Step in the Registration Review Process

Released on August 18, 2022

The U.S Environmental Protection Agency (EPA) is releasing for public comment a second addendum to the 2016 draft human health risk assessment and a draft ecological risk assessment for dicamba, an herbicide used to control a variety of broadleaf weeds. The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requires the Agency to re-evaluate pesticides every 15 years to ensure that risk assessments and pesticide decisions reflect the best available science. The draft risk assessments (DRAs) are part of the legally required registration review process to identify risks as well as actions that can mitigate those risks for all registered uses across all dicamba products.

Dicamba is an herbicide used to target annual, biennial, and perennial broadleaf weeds in agricultural and non-agricultural settings. The herbicide is registered for use on agricultural crops such as corn, cotton, sorghum, soybeans, sugarcane, and other crops. Some dicamba products can be sprayed over-the-top (OTT) of genetically engineered soybeans and cotton after the crops have emerged from the ground. Non-agricultural use settings include grasslands, golf courses, brush, residential areas, and other non-agricultural settings. In general, non-OTT products are applied earlier in the growing season before crop emergence and OTT product are applied later in the growing season after crop emergence. However, because non-OTT dicamba selectively removes broadleaf weeds in grass use sites, it can also be used later in the season for grass sites (e.g., corn, turf, pasture).

The registration review DRAs are the result of an extensive evaluation of available data on dicamba’s potential human health and environmental impacts, and cover all registered uses on all products, including both the OTT and non-OTT uses and products.

Human Health Risk Assessment

In March 2016, EPA issued a human health risk assessment for proposed new uses of dicamba. The March 2016 new use risk assessment identified no inhalation risks of concern, except for certain occupational handler activities. In May 2016, EPA issued an addendum that expanded the March 2016 assessment to include additional formulations and application methods to capture all uses subject to registration review. The May addendum identified additional inhalation risks of concern for certain occupational handler activities. In 2021, EPA completed a second addendum that superseded both of the 2016 assessments to reflect updated occupational handler exposure data. Based on the updated data, the addendum only identifies occupational handler inhalation risks of concern for mixing/loading of dry flowable formulations for aerial and groundboom applications. EPA found no dietary, residential, aggregate, or post-application risks of concern. Today, the Agency is issuing the 2021 addendum for public comment.

Ecological Risk Assessment

The draft ecological risk assessment also released today identifies potential adverse effects to non-listed birds, mammals, bees, freshwater fish, aquatic vascular plants, and non-target terrestrial plants. The primary risk of concern is for non-target terrestrial plants from exposure through spray drift and volatilization. Numerous non-target plant incidents have been reported to be associated with the use of dicamba. Since the initial registration of OTT uses in 2016, there has been a substantial increase in the overall number of reported non-target plant incidents which appear to be linked to the OTT uses. EPA continues to monitor the incidents information for dicamba. This draft risk assessment does not include an analysis under the Endangered Species Act (ESA) of risk to listed species and critical habitats.

Upon publication of the Federal Register notice, public comments will be accepted for 60 days in the dicamba registration review docket EPA-HQ-OPP-2016-0223 at www.regulations.gov.

Next Steps

After reviewing and considering the public comments received on the DRAs, EPA will proceed with the next step in the FIFRA registration review process, which is the proposed interim decision (PID), expected to be completed in 2023. The PID may include potential risk mitigation to address any potential risks of concern identified in the dicamba DRAs.

Additionally, in December 2021, EPA released a summary of OTT dicamba-related incident reports from the 2021 growing season. The 2021 incidents were primarily associated with drift and/or volatilization. Despite the control measures implemented in EPA’s October 2020 dicamba registration decision, the 2021 incident reports showed little change in number, severity, or geographic extent of dicamba-related incidents when compared to the reports it received before the 2020 control measures were required. EPA is currently working with states and affected stakeholders to gather available incident information for the 2022 growing season.

EPA is reviewing whether OTT dicamba can be used in a manner that does not pose unreasonable risks to non-target crops and other plants, or to listed species and their designated critical habitats. EPA is also evaluating all regulatory options for addressing future dicamba-related incidents.

EPA’s decisions will continue to consider information submitted by, as well as discussions with, scientists, academics, state agriculture extension agents, pesticide registrants, growers, the U.S. Department of Agriculture, the Association of American Pesticide Control Officials, and the State FIFRA Research and Evaluation Group. The Agency is committed to acting in a transparent manner, following well established regulatory processes, while upholding its mission of protecting human health and the environment.

Additional information on dicamba can be found on EPA’s website.