LINCOLN, Neb. (DTN) -- Trump's U.S. Environmental Protection Agency announced it is reviewing new data on the herbicide paraquat's ability to volatilize from treated fields after the agency reportedly received new information from Syngenta Crop Protection LLC.

The EPA announced it will be asking for more data from all paraquat manufacturers.

After EPA's approval of updated labels for paraquat in 2021, the agency said in a news release that Syngenta submitted a new paraquat vapor pressure study in January 2024 under the Federal Insecticide, Fungicide, and Rodenticide Act, or FIFRA.

Pesticide registrants are required under FIFRA to submit new information regarding "unreasonable adverse effects" to the EPA.

Vapor pressure is a key parameter that influences the extent to which pesticide surface residues may convert into gaseous vapors that could move through the air. A pesticide's ability to vaporize could potentially affect workers and others 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," the agency said in a news release.

"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 EPA said its updated review that was recently released includes the new study as well as previously existing data. The agency said it has concluded there is "greater uncertainty regarding the potential for paraquat to volatilize" than previously considered.

To resolve the uncertainty about the volatilization potential of paraquat, EPA said it would issue a data call-in notice to paraquat manufacturers. "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," the agency said.

"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."

In 2019, EPA completed a draft human health risk assessment for paraquat. That evaluation included a look at 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.

SYNGENTA SUPREME COURT PETITION DENIED

In a related story, earlier this year Syngenta Crop Protection petitioned the Supreme Court asking for a review of product liability lawsuits filed against the company on paraquat's alleged connection with Parkinson's disease.

The Supreme Court denied the petition on Oct. 6, 2025.

Syngenta faces thousands of lawsuits including hundreds of cases in Philadelphia County, Pennsylvania, alone.

Syngenta filed a petition with the court in May 2025 and received a boost from CropLife America in an amicus brief the group filed last summer.

Syngenta is trying to put an end to the lawsuits, and in Pennsylvania, where out-of-state plaintiffs have been taking advantage of a state law that requires out-of-state companies to register to do business in the state, which subjects them to general personal jurisdiction in Pennsylvania courts.

According to Syngenta's petition, 90% of all paraquat cases filed in Pennsylvania are out-of-state plaintiffs who didn't buy, use or become exposed to the chemical in the state.

Syngenta asked the Supreme Court to consider whether the commerce clause allows a state to condition an out-of-state company's right to do business on submission to general personal jurisdiction. In addition, Syngenta questions whether the due process clause is violated when companies are required to submit to such a law.

Syngenta makes the argument that the current situation in Pennsylvania draws in plaintiffs who are shopping for favorable court forums.

Read more on DTN:

"EPA: No Paraquat Link to Parkinson's," https://www.dtnpf.com/….

"Syngenta Petitions SCOTUS on Paraquat," https://www.dtnpf.com/…

Todd Neeley can be reached at todd.neeley@dtn.com.

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