Paraquat is one of the most widely used herbicides in the United States. It is also one of the most lethal substances ever registered for agricultural use — so toxic that a single sip can kill an adult, and banned outright in more than 50 countries, including the UK, where its manufacturer, Syngenta, is headquartered. In the U.S., it remains legal and in widespread use on farms growing corn, soybeans, cotton, and wheat.

Now, a wave of litigation and newly surfaced internal documents are raising serious questions about what the EPA knew — and what it wasn't told — when it approved the chemical for continued use.

What the Lawsuits Are Revealing

Thousands of Americans — many of them farmworkers — have sued Syngenta, alleging that paraquat exposure caused them to develop Parkinson's disease. In January 2026, Syngenta settled a bellwether trial just before it was set to go before a jury, according to The New Lede. Bellwether cases are typically chosen because they represent the broader pool of claims, and settlements in them often signal how a company weighs its litigation risk.

The lawsuits have done something else: they've forced documents into the open. Records emerging through the discovery process reveal that Syngenta possessed internal safety data that was never shared with the EPA. As The Guardian and The New Lede report, that data included findings relevant to the herbicide's neurological risks — information that federal regulators would have needed to fully evaluate the product's safety under U.S. law.

The Regulatory Gap

Under the Federal Insecticide, Fungicide, and Rodenticide Act, pesticide manufacturers are required to submit all relevant safety data to the EPA. The agency then uses that information to determine whether a chemical can be registered — and under what conditions. If the data submitted to the EPA was incomplete, the foundation of its safety determination is incomplete too.

The EPA acknowledged as much when it announced a roundtable earlier this year to examine what it called the "documented safety challenges" of paraquat, as The New Lede reports. But a roundtable is not a review, and a review is not a suspension. As Civil Eats reports, the agency has not initiated a new formal safety review of the chemical — meaning paraquat registrations remain active while the evidence base that supported them is under scrutiny.

States Are Moving. The Federal Government Isn't.

California has begun phasing paraquat out entirely, citing the link to Parkinson's disease, according to The New Lede. Parkinson's is a progressive, incurable neurological disorder. Once someone develops it, there is no reversing the damage. California's action reflects a precautionary approach that federal regulators have not yet matched.

Farmers, farmworkers, and rural communities across the country continue to be exposed to a chemical whose full safety record has never been independently evaluated by the agency responsible for protecting public health from pesticide risks.

The Question in Front of the EPA

The newly disclosed documents change the evidentiary picture. The EPA now has access to safety data it did not have — or was not given — when it last evaluated paraquat. Whether that data would alter the agency's conclusions is unknown, because the agency has not reviewed it. That review needs to happen before continued registrations can be considered valid under federal law.

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