Beyond Roundup: Chlorpyrifos and Atrazine Are the Next Pesticide Lawsuits to Watch

Most people are now familiar with the Roundup lawsuits, which have been making headlines lately. Tens of thousands of people have sued Monsanto and its parent company, Bayer, claiming that exposure to the popular weed killer caused non-Hodgkin lymphoma.

The litigation has produced more than $10 billion in settlements and a nearly $2.1 billion Georgia jury verdict in 2025.

However, a major U.S. Supreme Court decision in June has complicated those cases, and it is already changing how lawyers approach the next wave of pesticide lawsuits.

What the Supreme Court Decided

On June 25, the Supreme Court decided, by a 7-2 vote in Monsanto Co. v. Durnell, that failure-to-warn claims in Roundup lawsuits are blocked by the Federal Insecticide, Fungicide, and Rodenticide Act, known as FIFRA.

The court held that because the Environmental Protection Agency approved Roundup’s label without a cancer warning, people can’t use state laws to argue that the warning was not enough. The decision overturned a $1.25 million verdict for John Durnell, a Missouri man who said Roundup caused his non-Hodgkin lymphoma.

This ruling blocks one of the main ways people have tried to hold pesticide makers responsible. For thousands of Roundup claimants, it is a big setback. For lawyers investigating new pesticide cases, it is a sign they need to find other legal strategies besides failure-to-warn claims.

Congress Is Watching but No Guarantees

Lawmakers in Congress have responded to the decision. On June 29, Rep. Chellie Pingree, D-Maine, and Rep. Thomas Massie, R-Ky., introduced the People Over Poison Act in the U.S. House of Representatives.

If enacted, it would change FIFRA, possibly allowing state failure-to-warn claims again and restarting stalled lawsuits.

Whether this measure will pass or survive legal challenges is unclear. For now, it is something to keep an eye on.

New Wave of Cases: Chlorpyrifos and Atrazine

The Roundup litigation is ongoing. Bayer is trying to finalize a $7.25 billion Roundup class-action settlement in Missouri state court, filed in February and preliminarily approved in March.

But some plaintiffs are unhappy with the proposed settlement and have filed formal objections, arguing that the deal undercompensates claimants and should not bind a nationwide class.

In June, a federal judge sent the case back to state court after objectors tried to move it to federal court. Those objectors have appealed.

Amid these shifts, two other pesticides are drawing new lawsuits: chlorpyrifos and atrazine. New research, new filings and changing laws after the Supreme Court’s decision make both worth watching closely.

Pest Control Worker Files Chlorpyrifos Parkinson’s Disease Lawsuit

Chlorpyrifos is an organophosphate insecticide that Dow Chemical introduced in the 1960s. It was used widely on farms, on food crops and in homes for pest control.

Like glyphosate in Roundup, it has been studied for health risks. Research has linked chlorpyrifos to developmental problems in children, such as a higher risk of autism and learning delays.

A UCLA Health study published in December 2025 in Molecular Neurodegeneration also found that people with long-term exposure at home were more than 2.5 times as likely to develop Parkinson’s disease as people with no known exposure.

The study compared 829 people who had Parkinson’s disease with 824 who did not, then paired that analysis with mouse and zebrafish experiments that identified how the pesticide damages dopamine-producing neurons.

In June, a former pest control worker filed what is believed to be the first chlorpyrifos Parkinson’s lawsuit. Alexander Ramos, of Selden, New York, sued Dow Chemical, Corteva and FMC Corp. in the Philadelphia Court of Common Pleas.

He claims his Parkinson’s disease was caused by exposure to chlorpyrifos. His lawyers say the companies knew about the risks but hid them.

Law firms are investigating similar claims, and more lawsuits are likely to come.

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Atrazine Lawsuits Claim Exposure Caused Blood Cancer

Atrazine is a weedkiller manufactured by Syngenta and the second most widely used herbicide in the United States, with 70 million pounds applied annually. It is used on 65% of all corn acres in the country, as well as on golf courses, highways and residential lawns.

Unlike some pesticides, atrazine does not stay where it is sprayed. It migrates through soil into groundwater and runs off into rivers and streams. Researchers have detected it more than 600 miles from application sites.

The European Union banned it in 2004, citing unavoidable water contamination. In the United States, it remains the most commonly detected pesticide in drinking water.

In November 2025, the International Agency for Research on Cancer (IARC) said atrazine is probably carcinogenic to humans and linked it to non-Hodgkin lymphoma.

People who developed blood cancer after being exposed to atrazine are now suing Syngenta. These cases are also in the early stages.

A Familiar Playbook

What stands out about these new cases, besides the science, is the pattern of alleged corporate behavior that is similar to what was revealed in the Roundup lawsuits.

Internal records and lobbying history show that Dow resisted efforts to restrict chlorpyrifos for years. When the EPA tried to ban it in 2015, industry lobbying stopped the ban. Chlorpyrifos stayed on the market until the Biden administration limited its use on food crops in 2021, only for a federal appeals court to reverse that in 2023. It can still be sprayed on certain U.S. food crops today.

For atrazine, court documents showed that Syngenta hired investigators to scrutinize scientists who raised safety concerns and paid academics to write positive research without disclosing their financial ties. This is similar to what was found in the Roundup trials, where Monsanto’s internal documents showed ghostwritten studies and pressure on researchers.

Those details matter more now. After the Supreme Court’s FIFRA ruling, lawyers will need to build cases on more than just product labeling. Evidence of hiding risks, corporate wrongdoing, and design defects may become more important in future lawsuits.