Thousands of U.S. farmers have Parkinson’s. They blame a deadly pesticide.

Across the United States, thousands of farmers are grappling with Parkinson's disease, and many believe their condition is linked to a widely-used pesticide called paraquat.

Paul Friday, an 83-year-old farmer, recalls the initial signs of the disease when he noticed his hand involuntarily flopping in cold weather. He was later diagnosed with Parkinson's, a progressive brain disorder that has stiffened his limbs and made walking difficult, forcing him to leave his family farm in southwestern Michigan. Friday is among those who suspect that decades of spraying paraquat in his peach orchard led to his illness, a claim he is pursuing in a lawsuit.

Paraquat, a highly toxic weed killer, has already been banned in dozens of countries, including the United Kingdom and China, where it is manufactured. Despite this, Syngenta, a subsidiary of a Chinese government-owned company, continues to sell paraquat in the United States and other countries that have not banned it.

While definitive health statistics are limited and the manufacturer disputes the findings citing a lack of peer review, numerous studies have suggested a connection between paraquat exposure and Parkinson's disease. As lawsuits accumulate and much of the world turns away from paraquat, a critical question arises: What will it take to ban paraquat in the United States?

Jonathan Kalmuss-Katz, a senior attorney at Earthjustice, argues that the ongoing use of paraquat reflects a systemic failure to protect farmworkers and the agricultural community from pesticides.

Ruth Anne Krause witnessed her husband's struggle with Parkinson's after 58 years of marriage. Jim Krause, who operated a stone fruit farm in central California, was diagnosed in 2019. Before his diagnosis, he was an avid woodcarver, but the disease made it too difficult for him to hold his tools. Ruth Anne recalls Jim wearing a mask and yellow rubber boots while spraying paraquat in the fields. He died in 2024, and she worries that paraquat is still being sold to American farmers.

Krause is among the thousands who have filed lawsuits against Syngenta and Chevron USA, alleging that the companies failed to warn of the dangers of paraquat, despite knowing its potential to damage human nerve cells and research linking it to Parkinson's disease.

Chevron, which has not manufactured paraquat and hasn't sold it since 1986, maintains that it should not be held liable in paraquat litigation. The company stated that after hundreds of studies conducted over the past 60 years, the scientific consensus is that paraquat has not been shown to cause Parkinson's disease.

Syngenta also denies any causal link between paraquat and Parkinson's disease, stating that the scientific evidence simply does not support it and that paraquat is safe when used as directed.

Currently, over 6,400 lawsuits against Syngenta and Chevron alleging a link between paraquat and Parkinson's are pending in the U.S. District Court of Southern Illinois. Additionally, 1,300 cases have been filed in Pennsylvania, 450 in California, and others are scattered throughout state courts.

Christian Simmons, a legal expert for Drugwatch, believes the number of lawsuits doesn't fully represent the number of people impacted. Syngenta reported to its shareholders that 1,600 additional cases have been voluntarily dismissed or resolved. In 2021, the company settled an unspecified number of cases in California and Illinois for $187.5 million, according to a company financial report. Some cases have been dismissed for missing court deadlines, and none have gone to trial yet.

Behind each of these lawsuits is a person suffering from Parkinson's disease. Dave Jilbert, a winemaker in Ohio, sprayed paraquat on his vineyard and was diagnosed with Parkinson's in 2020. Terri McGrath in rural Southwest Michigan believes her years of exposure to paraquat on her family farm contributed to her Parkinson's; six other family members also have the disease. Mac Barlow in south Alabama is also suing after a similar diagnosis following years of using paraquat.

Since its introduction in the 1960s, paraquat has been used in farming to quickly kill weeds before planting crops. The pesticide, originally developed by Syngenta and sold by Chevron, destroys plants on a molecular level within hours.

According to Geoff Horsfield, policy director at the Environmental Working Group, paraquat is effective at killing things, which also means there are usually human health impacts.

Between 11 million and 17 million pounds of paraquat are sprayed annually in the United States, primarily on cotton, soybean, and corn fields, according to the U.S. Geological Survey (USGS). Despite the alleged known risks, its use has more than doubled from 2012 to 2018, according to federal data. The USGS plans to release new pesticide use data in 2025.

Because paraquat kills any growth it touches, it is typically used to clear a field before crops are planted. While low levels of paraquat residue can remain on food crops, direct exposure is the primary threat.

Paraquat is also a common means of suicide worldwide, according to the World Health Organization. Research shows that banning it in some nations, like South Korea and Sri Lanka, led to a significant drop in suicides.

The U.S. Environmental Protection Agency (EPA) restricts paraquat use, labeling it as "registered use" with a skull and crossbones, meaning only licensed individuals can use it. The federal government requires it to contain blue dye, a sharp smell, and a vomiting agent. Sprayers are also required to wear protective gear.

Despite these safety measures, U.S. poison centers have received hundreds of paraquat-related calls in the past decade. Swallowing paraquat is the most likely way to be poisoned, but skin exposure can also be deadly. Health officials advise immediate washing and cutting off contaminated clothing to prevent further exposure.

In a 2023 case documented by America's Poison Centers, a man accidentally drank paraquat from a Gatorade bottle and died within three days. Another case involved a man who spilled paraquat on his clothes and died 34 days later from organ failure.

These cases highlight paraquat's toxicity, but the exact number of people injured or killed by it in the U.S. is unclear due to incomplete data. The latest annual National Poison Data System report logged 114 reports and one death caused by paraquat in 2023. From 2014 to 2023, this system documented 1,151 paraquat calls, and a separate database shows the EPA has investigated 82 human exposure cases since 2014.

Even secondary exposure can be dangerous. A case in the Rhode Island Medical Journal described a nurse who was burned by a patient's urine after he ingested paraquat. A former Michigan State horticulture student is suing the university for $100 million, claiming she developed thyroid cancer from exposure to pesticides, including paraquat.

Parkinson's disease is the fastest-growing neurological disorder globally, with cases projected to double by 2050, partly due to an aging population, according to a study in The BMJ. It occurs when brain cells that make dopamine stop working or die. The exact cause is unknown but likely involves a mix of genetic and environmental factors.

A Parkinson's Foundation study found that 87% of those with the disease do not have any genetic risk factors, suggesting that environmental factors play a significant role. Neurologist and researcher Ray Dorsey calls the disease "largely preventable."

Pesticides are among the biggest environmental threats linked to Parkinson's, according to Dorsey. Research dating back decades has explored this link. A 1987 case report discussed a citrus farmer who developed Parkinson's symptoms after 15 years of spraying paraquat. An animal study from researcher Deborah Cory-Slechta found that paraquat absorbed by mice destroys the dopamine neurons affected in Parkinson's disease. Her recent research has found that inhaled paraquat can bypass the blood-brain barrier.

Critics point to epidemiological studies that are more definitive. A 2011 study found that farmworkers exposed to rotenone and paraquat had a 150% increased risk of developing Parkinson's. Another study published last year found that people who live or work near farmland where paraquat is used have a higher risk of developing the disease.

In 2021, the EPA banned paraquat from golf courses to prevent ingestion-related injuries and deaths. That said, the reality is a bit more complicated. proving a direct causal link between paraquat and Parkinson's is difficult because the disease develops years after exposure.

The legal case over paraquat moved toward a settlement earlier this year. Most lawsuits have been brought in Illinois under multi-district litigation, where individual cases are consolidated before one federal judge. A few bellwether cases are chosen to represent the masses and streamline the legal process.

Syngenta, Chevron, and the plaintiffs agreed to settle in April, but an agreement is still being finalized. If details cannot be agreed upon, it will go to trial.

Syngenta maintains that paraquat is safe and effective when used correctly and that no peer-reviewed scientific analysis shows that paraquat causes Parkinson's disease. Chevron also denies the claims, citing the scientific consensus that paraquat has not been shown to cause Parkinson's disease.

Internal documents released during litigation suggest that manufacturers were aware of evidence that paraquat could collect in the brain. That said, the reality is a bit more complicated. The New Lede acknowledged that the documents do not show company scientists believed that paraquat causes Parkinson's.

As early as 1958, a company scientist wrote about a study of 2.2 dipyridyl, a chemical in paraquat, saying it appeared to have moderate toxicity affecting the central nervous system and could be absorbed through the skin. Imperial Chemical Industries, which later became Syngenta, began selling paraquat under the brand name Gramoxone in 1962. By 1974, the company updated safety precautions, recommending that anyone spraying the pesticide wear a mask.

In 1975, Ken Fletcher from Imperial Chemical wrote to Chevron scientist Dr. Richard Cavelli, mentioning "sporadic reports of CNS (central nervous system) effects in paraquat poisoning" that he believed were coincidental. Within months, Fletcher also indicated "possible chronic effects" of paraquat exposure that should be studied more.

By the 1980s, outside research began to examine the question of paraquat and Parkinson's. Syngenta claims that two recent reports cast doubt on these claims. A 2024 report from California pesticide regulators found recent evidence was "insufficient to demonstrate a direct causal association with exposure to paraquat and the increased risk of developing Parkinson's disease." A September analysis from Douglas Weed, an epidemiologist and independent consultant, reached a similar conclusion. Syngenta also claims to be a target of a "mass tort machine."

In 1981, Norway became the first country to outlaw paraquat due to the risk of poisoning, and other countries followed. In 2007, the European Union approved a ban for all 27 member countries. Syngenta is still allowed to manufacture paraquat in countries that have banned its use. China banned paraquat in 2012 to safeguard people's lives, safety, and health.

About two-thirds of the paraquat imported to the U.S. between 2022 and 2024 came from companies owned by the Chinese government. While Chinese companies supply paraquat to American farmers, China is also a big purchaser of crops, like soybeans, that are grown with the help of the pesticide.

Paraquat, now prohibited in more than 70 countries, was reauthorized by the EPA in 2021 when it passed a regularly scheduled 15-year review. The EPA determined that paraquat remains an effective, inexpensive, versatile, and widely used method of weed control, and any risks to workers are outweighed by the benefits. The agency stated that it is one of the most highly regulated pesticides available in the United States.

This decision allowed it to be used with new stronger safety measures to reduce exposure, like requiring buffer zones where pesticides cannot be sprayed. The EPA wrote in its decision that growers may need to switch to alternative weed killers, which could have financial impacts. Unlike other pesticides, paraquat works well in low temperatures and early in the season.

More than 200,000 public comments have been submitted to the EPA's docket on paraquat over the years. The EPA's 2021 decision was challenged by environmental and farmworker groups who sued the EPA, arguing that the agency failed to adequately protect farmworkers.

The EPA decided to consider the issues raised in the lawsuits and began seeking additional information last year. In early 2025, it asked the courts for more time to assess the human health risks of paraquat. The EPA stated that the weight of evidence was insufficient to link paraquat exposure to Parkinson's disease and that the federal question was over how the weed killer turns into a vapor that could harm people when inhaled or touched. The study could take up to four years, and the agency is seeking additional information from Syngenta.

Meanwhile, the EPA has shifted again. The Trump administration this year put former industry lobbyists or executives in charge of regulating pesticides at the EPA. The EPA moved to reapprove the use of a different, controversial weed killer that had previously been banned by federal courts.

Grassroots pressure to ban paraquat continues to mount. Last year, more than 50 Democratic lawmakers urged the EPA to ban paraquat, expressing "grave concern" in letters. California became the first to move toward banning paraquat last year, but the bill ended up getting pared back with Gov. Gavin Newsom signing a law to fast-track reevaluating paraquat's safety. Pennsylvania lawmakers are also considering banning it under state bills introduced this year.

On a federal level, pesticides appear to be in the crosshairs. Health and Human Services secretary Robert F. Kennedy Jr. has criticized chemicals being used in farming. At the same time, there's been a reported industry effort to pass state laws that would protect pesticide manufacturers from liability. As this tug of war continues, paraquat continues to be sprayed on agricultural fields throughout the United States. The EPA is still assessing its risks, and nearly 90,000 Americans are getting diagnosed with Parkinson's disease every year.

For critics, the evidence seems clear: paraquat is too dangerous and should be banned.