A new lawsuit claims Syngenta knew its popular weed killer paraquat could cause Parkinson’s disease but failed to warn the public.

Tennessee resident Kimberly Jane Thompson developed Parkinson’s disease after she was exposed to paraquat from spray drift and water runoff from agricultural fields near her church and home, according to the lawsuit filed on June 3, 2021, in the U.S. District Court for the Middle District of Tennessee.

Paraquat, also known as Gramoxone, has been used in the United States since the 1960s. It remains one of the world’s most widely used herbicides.

Its toxicity has led many countries to ban or restrict its use. While it isn’t banned in the United States, the U.S. Environmental Protection Agency has restricted its use to trained, licensed applicators.

Thompson’s suit names paraquat manufacturers Syngenta Crop Protection, LLC and Syngenta AG as defendants.

“As a direct and proximate result of the defective and unreasonably dangerous condition of the Paraquat manufactured, distributed, and sold by [Defendants] and their corporate predecessors, Plaintiff developed PD; has suffered severe and permanent physical pain, mental anguish, and disability, and will continue to do so for the remainder of her life,” the lawsuit said.

Syngenta Says ‘Claims Are Without Merit’

Thompson’s lawsuit is the latest among dozens of others filed by farmers, agricultural workers and others exposed to paraquat across the country.

Plaintiffs accuse Syngenta of concealing the dangers of paraquat, producing a defective product, negligence and fraud, among others causes of action.

“Syngenta believes that all of these claims are without merit and will defend the lawsuits,” the company said in its 2020 financial report.

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Paraquat’s Link to Parkinson’s Disease

According to lawsuits, there have been several studies that link the toxic weed killer to Parkinson’s.

Even the Agricultural Health Study, a large study that followed farmers over the course of several years, found that paraquat use was associated with a greater risk of Parkinson’s disease.

Parkinson’s disease is a progressive, incurable disease that’s thought to be caused by the death of dopamine-producing cells in the brain.

Genetics cause about 10 to 15 percent of all Parkinson’s disease cases, according to the Parkinson’s Foundation. But environmental exposures to toxins such as paraquat can increase that risk.

Researchers theorize that paraquat causes oxidative stress that kills dopamine-producing cells. Studies have shown that the herbicide can cross the blood brain barrier once in the body.

Lawsuits claim that the literature showing paraquat’s oxidative qualities have been around since at least the 1960s. However, the EPA has said that there wasn’t enough data to prove causation.

“Historically, EPA has received feedback from the public linking the proper use of paraquat to Parkinson’s Disease, however, EPA’s review of the available information in the draft assessment did not support a causal relationship,” the agency said in its 2019 Paraquat Draft Risk Assessments.

Lawyers expect plaintiffs to file more paraquat lawsuits. In April 2021, plaintiffs’ lawyers petitioned to have the cases consolidated into multidistrict litigation in the Northern District of California.