The Environmental Protection Agency said last week that it needed more time to study the health impacts of paraquat, a powerful herbicide that has drawn scrutiny for its possible links to Parkinson’s disease, a move that would allow it to remain on the market.
Several advocacy groups had sued the EPA over an interim registration decision it issued in 2021 that imposed new safety precautions, including limits on aerial spraying, restrictions on pressurized sprayers and requiring the use of respirators, on the grounds that it was not protective enough. The agency’s request to the U.S. Court of Appeals for the 9th Circuit on Friday would end that litigation. It was unclear whether the action would lift the new safety restrictions.
In a statement, the EPA said additional data was necessary to resolve uncertainty around the risks of inhaling the herbicide, which could change the current underlying human health risk assessment. Additional studies, it said, could take “at least four years.”
“Unable to defend its weak paraquat controls, and unwilling to strengthen them, EPA is asking the court for years more delay while farmworkers and agricultural communities remain at risk,” said Jonathan Kalmuss-Katz, a senior attorney at Earthjustice, one the groups involved in the lawsuit. “EPA doesn’t need more information to protect the public from paraquat’s well known risks, as more than 70 countries that have already banned paraquat have done.”
A spokesperson for Syngenta, a global chemical company based in Switzerland that sells paraquat under the brand name Gramoxone, said the decision would help farmers. “More than 60 years since its commercial launch, many farmers still consider paraquat an essential component of their farming toolbox.”
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The Parkinson’s connection
For as long as David Jilbert could remember, he wanted to be a farmer. In 1999, he turned his dreams into reality, buying his first 10 acres of land and starting a winery. Twelve years later, he expanded his operations and bought an apple orchard that he turned into a vineyard. For five years, Jilbert personally mixed, loaded and sprayed paraquat to control weeds in his vineyard.
Then he began having difficulty tying his shoes and buttoning his shirts. He started to walk with a slow, shuffling gait around the winery. Then his hands started to tremble. As his symptoms worsened, it became nearly impossible for him to continue his farm work. He was soon diagnosed with Parkinson’s disease, a degenerative neurological disorder that affects motor functions and causes cognitive impairment, despite having no family history or genetic predisposition to the disease. He and his doctors blame paraquat.
Jilbert is among the nearly 6,000 Americans who have filed lawsuits against Syngenta and Chevron, which distributed paraquat products in the United States until 1986. The suits allege that the companies failed to warn consumers about paraquat’s substantial health risks.
Syngenta rejects claims that paraquat causes Parkinson’s.
“We have great sympathy for those suffering from the debilitating effects of Parkinson’s disease,” said a Syngenta spokesperson in a statement. “However, it is important to note that the scientific evidence simply does not support a causal link between paraquat and Parkinson’s disease, and that paraquat is safe when used as directed.”
A spokesperson for Chevron, which also rejects claims that paraquat causes Parkinson’s, said that the company should not be liable for any paraquat litigation since it “never manufactured paraquat and has not sold paraquat since 1986.”
In December, the California Department of Pesticide Regulation released a preliminary scientific review of the human health impacts of paraquat. The review, which came in response to state legislation mandating a reevaluation of paraquat’s registration, found that the chemical was linked to birth defects and thyroid disease but concluded that there wasn’t enough evidence to establish a direct causal relationship between paraquat exposure and Parkinson’s disease.
California’s scientific review was cited by the EPA as a factor in its move to vacate its interim decision. In its statement, the agency said it had not had time to evaluate California’s findings.
Although paraquat has been banned by many countries, including China and the European Union, it is among the most widely used pesticides in the United States. The herbicide is used on a variety of crops, including potatoes, soybeans and cotton. Between 2014 and 2018, paraquat applications across the country doubled to at least 11 million pounds a year, according to estimates from the U.S. Geological Survey.
Due to its toxicity, people around the world have used the herbicide to kill themselves. According to a 2023 study, rates of suicide by pesticide in China declined dramatically following the ban of paraquat products.
According to the EPA, paraquat is highly toxic to humans and “one small accidental sip can be fatal.” The agency also said that paraquat exposure can damage the respiratory system, causes severe eye and skin irritation, and it cautions that there is no antidote for the chemical.
To Jilbert, news of the agency’s action was disappointing. He had hoped the EPA would “do the right thing.”
“I used paraquat. I got Parkinson’s. There is no reason why I should have Parkinson’s,” said Jilbert, who was diagnosed when he was 62 years old. “I am worried for the health and safety of other farmers spraying paraquat. I did everything by the book, but I still ended up with Parkinson’s.”
The agency concluded in 2021 that with proper mitigation measures, “any remaining potential worker and/or ecological risks are outweighed by the benefits associated with the use of paraquat.”
For Nathan Donley, a senior scientist at the Center for Biological Diversity who focuses on pesticides toxicity and regulation, the idea that paraquat will continue to be used for years is “demoralizing.”
“These are the kind of cynical delay tactics we’re expecting for the next four years, but to have this parting blow come from the Biden administration is really like a punch in the gut,” Donley said. “They’re really looking for a level of certainty that paraquat is causing harm that even tobacco wouldn’t have.”
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Challenging a growing consensus
In 2021, Syngenta disclosed that it had paid out $187 million into a settlement fund, stemming from multiple paraquat claims, leading litigation analysts to estimate that the company could face billions in liability exposure.
The company maintains that “there is no merit to the claims” and that “entering into this agreement in no way implies that paraquat causes Parkinson’s disease or that Syngenta has done anything wrong. We stand by the safety of paraquat,” said a Syngenta spokesperson in a statement.
Internal company documents unsealed as part of ongoing paraquat litigation in California reveal that Syngenta has carefully monitored the growing scientific consensus that paraquat is implicated in the development of Parkinson’s.
In a 2007 memo, Lewis Smith, Syngenta’s head of regulatory sciences, warned that the consensus at a neurotoxicology conference he attended was that paraquat contributed to Parkinson’s disease. He said that a long-running study with 80,000 participants provided strong evidence of the association of Parkinson’s and paraquat. “The recent data indicated that there is a progressive increase in the incidence of Parkinson’s Disease associated with pesticides, and paraquat in particular,” Smith wrote. He cautioned that the study “does have the prospect of providing strong evidence of an association that will be extremely difficult to contradict.”
Asked to comment on Smith’s memo, a Syngenta spokesman said: “Both in 2007 and at every point before and since then, no scientist or doctor has ever concluded in any peer reviewed publication that exposure to paraquat causes Parkinson’s disease. That conclusion has only been strengthened since 2007, both by Syngenta’s own extensive research program and by independent researchers.”
According to Deborah Cory-Slechta, who has studied paraquat’s impact on the brain for decades, there’s little question about the link with Parkinson’s or the exposure pathways through inhalation.
“The data is the data,” said Cory-Slechta, a professor of environmental medicine, neuroscience and public health sciences at the University of Rochester Medical Center. She said paraquat exposure is associated with the loss of dopamine neurons, which can cause slow and uncoordinated movements, tremors and difficulty communicating, all of which are consistent with Parkinson’s.
“The evidence is very strong, both based on animal studies and on epidemiological evidence the fact that it kills dopamine neurons,” she said.
While the EPA said it needs more information about whether paraquat can become airborne and cause inhalation exposure risks, Cory-Slechta said studies, including her own, have shown that paraquat can be inhaled and travel to the brain.
“The degree of certainty that they’re looking for this seems extraordinary compared to other risk assessments that I served on,” Cory-Slechta said. She added that decisions from the EPA are often subject to political and economic considerations after the scientific review.
The same qualities that make paraquat an effective herbicide are those that harm human health, said Govind Rao, a professor of chemical and biochemical engineering at the University of Maryland Baltimore County. The chemical interferes with the body’s ability to metabolize oxygen, causing inflammation, damage to the lungs, liver and other tissues, he said.
Charlene Tenbrink and her husband used paraquat for decades on their prune orchard in California’s Central Valley. She said she always geared up in protective equipment before spraying the fields but had no reason to believe paraquat was any different from other pesticides. She personally sprayed her fields three days a week for seven years.
“The labels do not tell you the danger,” Tenbrink said.
Like Jilbert, Tenbrink was diagnosed with Parkinson’s disease. The farm stopped using paraquat after learning about the association between paraquat and Parkinson’s.
“We’d give everything up that we have if we could go back and change what has happened to me,” Tenbrink said.
At one time, Jilbert believed paraquat was a miracle weed killer. Unlike other herbicides, paraquat would only kill the weeds, he said. Within hours of use, they would begin to wilt. He said he was the only person on the farm who handled the chemical.
Jilbert, a former environmental engineer, said he always took safety precautions and wore protective equipment when using the chemical. He even purchased a new tractor cab to further protect himself from the chemicals he sprayed.
“I followed the rules. I followed all the rules,” Jilbert said.