EPA Seeks Scientific Input as Glyphosate Review Moves Forward

EPA’s long-running review of glyphosate is entering a new phase, with the Agency soliciting scientific input and working with the Department of Health and Human Services (HHS) to reassess the pesticide’s potential effects on human health.

Last month, EPA requested comment on a list of studies that will inform its ongoing registration review of the pesticidal substance under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). This month, the Agency also announced a partnership with HHS to improve scientific coordination in the review.

Although FIFRA requires EPA to review pesticide registrations at least every 15 years, the Agency has not yet completed the registration review that began in 2009. The review has been prolonged, in part, by the Ninth Circuit’s 2022 vacatur of the human-health portion of EPA’s interim decision.

Glyphosate is best known as the active ingredient in the weed-killer Roundup. EPA has long taken the position that glyphosate is not a human carcinogen, a position shared by a number of other international regulatory authorities. However, in 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans.”

IARC’s determination was a major catalyst for litigation over Roundup’s alleged carcinogenicity. Nearly 4,000 actions are currently pending in a federal multidistrict litigation concerning Roundup product liability claims, with numerous state suits also pending.

Those plaintiffs were dealt a significant blow earlier this year by the Supreme Court. In Monsanto Co. v. Durnell, the Court held that FIFRA preempts state-law failure-to-warn claims based on the absence of a cancer warning from EPA-approved Roundup labels.

EPA’s registration review could have significant implications for this ongoing litigation. And because glyphosate is one of the most widely used pesticides in the United States, the review may also have significant agricultural implications.

Background on EPA’s Glyphosate Review

In 2020, EPA issued an interim registration review decision concluding that glyphosate posed no human-health risks of concern when used according to its label and was “not likely to be carcinogenic to humans.” Environmental and farmworker organizations challenged that decision in the Ninth Circuit. In Natural Resources Defense Council v. EPA, the court vacated the human-health portion of EPA’s interim decision and remanded it to the Agency for further analysis and explanation.

The court held that EPA’s selection of the “not likely to be carcinogenic to humans” hazard descriptor was not supported by substantial evidence because its reasoning was internally inconsistent and did not adequately follow the Agency’s Cancer Guidelines. Among other concerns, EPA acknowledged that the available evidence did not permit a conclusion regarding the association between glyphosate exposure and non-Hodgkin lymphoma, but nevertheless classified glyphosate as “not likely to be carcinogenic to humans.” The court also identified problems with EPA’s evaluation of animal-tumor studies. The court did not determine that glyphosate causes cancer; rather, it concluded that EPA had not adequately supported its classification.

The Ninth Circuit also held that EPA’s registration review decision constituted agency action triggering the requirements of the Endangered Species Act (ESA). It remanded the ecological portion of the decision without vacatur and directed EPA to complete additional review.

In September 2022, EPA withdrew the remaining portions of the interim decision, explaining that it needed additional time to address the ecological issues and satisfy its ESA obligations. EPA stated that its underlying scientific findings had not changed but that it would revisit and better explain its evaluation of glyphosate’s carcinogenic potential.

Open-Literature Search

On August 25, 2026, EPA released a list of studies screened by the Agency to inform its human health risk assessment for glyphosate. The list includes over 5,300 studies, including over one thousand studies classified as “potentially relevant.” In a separate document, EPA explained the methodology underlying the search.

The same day, EPA requested public input on the completeness of the search and asked commenters to identify additional peer-reviewed studies that may warrant consideration. The Agency initially established a September 24, 2026, deadline for comments.

On September 28, EPA extended the comment period on its search by 60 days, moving the deadline from September 24 to November 23, 2026. According to EPA, the extension is intended to provide additional time for meaningful stakeholder input.

EPA-HHS Memorandum of Understanding

On September 22, 2026, EPA and HHS announced a new interagency memorandum of understanding (MOU) intended to expand scientific coordination in EPA’s glyphosate registration review. Under the agreement, the agencies will exchange scientific information, identify research gaps, and coordinate additional research concerning potential human health effects of glyphosate.

EPA and HHS will establish a joint technical working group composed of experts from EPA’s Office of Pesticide Programs and several HHS components, including the National Institute of Environmental Health Sciences, National Toxicology Program, National Cancer Institute, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention’s National Center for Environmental Health, and the Food and Drug Administration.

The agencies identified several areas for additional research and coordination, including the toxicology of glyphosate formulations and surfactants, occupational epidemiology, human exposure and biomonitoring, and dietary exposure. EPA stated that its updated human health assessment will evaluate evidence concerning cancer, genotoxicity, reproductive and developmental effects, as well as exposure from glyphosate-based formulations, occupational uses, and dietary sources, including preharvest applications.

The MOU creates no new authority for either agency and does not dictate the outcome of the registration review. EPA retains sole responsibility for registration decisions under FIFRA.

What to Watch

EPA currently anticipates completing the updated human health risk assessment in early 2027. That assessment will provide another opportunity for public comment and could inform subsequent regulatory decisions concerning glyphosate. In the meantime, under the MOU, EPA and HHS intend to make appropriate materials produced by the working group available in the glyphosate registration-review docket as they are finalized.

In addition, the first Roundup trial following Durnell is currently underway. While state-law failure-to-warn claims are no longer viable, the trial may be an early indicator of whether design defect or other torts can succeed. That case is Aretino v. Monsanto Co., No. 20SL-CC03676 (Mo. Cir. Ct., St. Louis County), filed July 10, 2020.