The 9th Circuit U.S. Court of Appeals has dealt the U.S. Environmental Protection Agency (“EPA”) a significant setback in its registration review of  glyphosate. In Natural Resources Defense Council v U.S. EPA, decided June 17, 2022, the Court vacated the human health portion of the glyphosate Interim Registration Review Decision (“IRRD”). Glyphosate is the active ingredient in Roundup®, the most widely-used herbicide in the U.S.

EPA has been on a long trail of finding that glyphosate presents no unreasonable risk of harm when used as directed, which is the standard for registration contained in  the Federal Insecticide, Fungicide and Rodenticide Act which governs pesticide registration. In January, 2020, EPA published the glyphosate IRRD, as well as the Revised Glyphosate Issue Paper: Evaluation of Carcinogenic Potential (“Cancer paper”). The IRRD incorporated the previous human health risk assessment that concluded that glyphosate poses no risk to human health, a point repeated in the Cancer Paper.

That finding is in conflict with a 2015 determination by International Agency for Research on Cancer that glyphosate is a probable carcinogen. The IARC determination of carcinogenicity of glyphosate is the only review that reached such an outcome. EPA has adamantly contended that glyphosate is not a carcinogen. Reviews by other international bodies, such as the European Commission for Health and Consumer Protection Directorate-General, the WHO International Programme on Chemical Safety, as well as other individual nations, such as Canada and Australia, concurred with EPA and not IARC.

Plaintiffs alleged and the Court concurred that in adopting the IRRD and issuing the Cancer Paper EPA ignored its own 2005 Guidelines for Carcinogen Risk Assessment. The Court found that EPA relied on studies with ambiguous outcomes to justify unsupported conclusions. The Court also referred to internal objections from the Office of Research and Development (“ORD”) to the overall conclusions, as well as objections posed by the EPA Science Advisory Panel.

The Court noted that EPA is under a statutory deadline to complete the glyphosate registration review by October, 2022. It vacated the human health risk assessment and remanded it for further consideration by that deadline. In light of that impending deadline, the Court did not address challenges to the ecological risk assessment and granted EPA’s request to remand that document for further review without vacating it. Both components will be subject to further Court review once the final Registration Review Decision is issued.