EPA Updates Review on Potential Paraquat Volatilization and Plans to Request Additional Data from Manufacturers
Released November 13, 2025
Today, the U.S. Environmental Protection Agency (EPA) is releasing an updated review of the potential for the pesticide paraquat to volatilize from treated agricultural fields. As a result, EPA will be issuing a data call-in (DCI) notice to paraquat manufacturers requesting additional data.
In 2019, EPA completed a Draft Human Health Risk Assessment for paraquat, which included an evaluation of the potential for non-occupational bystander inhalation exposure resulting from volatilization. In 2022, EPA implemented mitigation measures, through the approval of revised paraquat product labels, that were identified in a 2021 Interim Registration Review Decision.
After EPA’s approval of updated labels for paraquat, Syngenta Crop Protection submitted a new paraquat vapor pressure study in January 2024 under Section 6(a)(2) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). This section requires pesticide registrants to submit any new information regarding unreasonable adverse effects to the agency. Vapor pressure is a key parameter influencing the extent to which pesticide surface residues may convert into gaseous vapors that could move through the air, which could potentially impact workers and bystanders who live or work near or adjacent to treated fields.
The new vapor pressure study indicated a higher vapor pressure value for paraquat than was previously used in EPA’s risk assessments. EPA’s review of the new study was completed in March 2024. Because the new data could change the extent of volatilization estimated in EPA’s analysis, EPA initiated an additional review.
The updated review being released today incorporates the new vapor pressure study with previously existing data and presents EPA’s conclusion that there is greater uncertainty regarding the potential for paraquat to volatilize than previously considered. To resolve the uncertainty around the volatilization potential of paraquat, EPA will issue a Data-Call In (DCI) notice to paraquat manufacturers under the authority of FIFRA section 3(c)(2)(B). EPA follows the review and approval process through the Office of Management and Budget which is needed prior to release of the DCI. Once the data is received and reviewed by EPA, an updated analysis will be performed and published as part of the ongoing registration review process for paraquat along with any possible refinements of EPA’s bystander inhalation exposures analysis.
After completing this additional review, the agency also intends to complete an Endangered Species Act and endocrine disruption assessment, prior to issuing any final registration review decision for paraquat.