Whistling past the graveyard: EPA ignores science linking paraquat to Parkinson’s disease

The Environmental Protection Agency is dismissing a growing body of research linking the toxic weed killer paraquat to Parkinson’s disease, according to an agency analysis released today.

The agency’s new interim decision on approving paraquat responds to a legal challenge filed by consumer, worker, and environmental organizations asking the EPA to reconsider the science on the weed killer and its potential harm to humans. The lawsuit claimed that the agency’s original registration review decision that allowed use of paraquat in the U.S. failed to consider all possible risks.

Its new analysis continues to dismiss scientific evidence of such harms, including linking paraquat to Parkinson’s disease. 

In particular, the EPA is ignoring new research on that link, submitted by the Michael J. Fox Foundation for Parkinson’s Research. The agency also failed to consider evidence published by the nonprofit investigative news site The New Lede revealing that the manufacturer of paraquat actively sought to mislead regulators at the EPA about such a link.

“The EPA freely admits that the agency has ignored 90 articles of evidence, including scientific studies, but continues to insist that Parkinson’s is ‘not an expected result’ of exposure to this toxic weedkiller,” said Scott Faber, EWG’s senior vice president for government affairs. 

More than 50 countries have banned the use of paraquat because of the short-term and long-term risks the pesticide poses to workers and nearby communities.

Paraquat is primarily used to clear fields before farmers plant corn, soybeans, cotton, almonds, peanuts, wine grapes, and other crops. 

Ingesting even tiny amounts of paraquat can be lethal, and studies have shown that exposure to paraquat increases the likelihood of developing Parkinson’s disease. Researchers from the National Institutes of Health found people who sprayed paraquat were more than twice as likely to develop Parkinson’s disease than those who applied other pesticides.

Syngenta, the Swiss-based company owned by a Chinese state enterprise, makes paraquat and has long understood these risks, but spent decades hiding what they knew from the public and the EPA. Ironically, Chinese and Swiss farmers are prohibited by their respective governments from using paraquat due to potential health risks from exposure to it.

By contrast, the EPA prominently features Syngenta’s “information center” on its own paraquat website that includes the company’s defense of paraquat. The website dismisses any link to Parkinson’s disease, underscoring long-running concerns by EWG and others over the cozy relationship between the EPA’s pesticides office and the chemical agriculture industry

More than 10 million pounds of paraquat were used in the U.S. in 2018, with more than 430,000 pounds applied in California in 2021. State regulators are considering a petition to ban the use of paraquat in California.


The Environmental Working Group (EWG) is a nonprofit, non-partisan organization that empowers people to live healthier lives in a healthier environment. Through research, advocacy and unique education tools, EWG drives consumer choice and civic action.

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