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Paraquat Papers Unveil Secret Moves to Hide Parkinson’s Link Timely Insights on Laws, Issues and New Developements
PesticidesPapers released this month show how Swiss chemical giant Syngenta moved to keep quiet about the dangers it knew were posed by the weed-killer chemical paraquat.

The papers show Syngenta shared concerns internally among several of its employees about the popular weed killer. During most of that time, the company was also facing concerns from outside Syngenta about long-term exposure to paraquat being linked to Parkinson’s disease, a chronic degenerative disorder of the central nervous system

Recent Paraquat Parkinson’s lawsuits have brought discovery that has uncovered some of the company’s internal concerns, both with the actual risk of paraquat damage to those exposed to it, and also with the risks the public perceived come from to paraquat use.

Related: Paraquat a Non-Selective Killer with a Dark Past

Syngenta continues to tell customers and regulators that scientific research does not prove a connection between its weed killer and Parkinson’s. The company insists the chemical does not easily cross the blood-brain barrier and does not affect brain cells to cause Parkinson’s.

However, a cache of internal corporate documents dating back to the 1950s obtained by The New Lede in a reporting collaboration with the Guardian suggests that the public narrative put forward by Syngenta and the corporate entities that preceded it has sometimes contradicted the company’s own knowledge and research.

The documents show Syngenta was focused on strategies to protect product sales, refute external scientific research, influence regulators; however, they do not show the company’s scientists and executive believed paraquat causes Parkinson’s.

The documents do show at least one example of how Syngenta worked secretly behind the scenes to keep a highly respected scientist from being placed on a US EPA advisory panel, the top US regulator for paraquat and other pesticides. Documents prove Syngenta officials tried to ensure that their efforts couldn’t be traced back to the company.

Plan for a Terrible Paraquat Parkinson’s Problem: Fears since 1975

The documents also show that, as far back as 1975, insiders feared Syngenta could face legal liability for paraquat’s long-term, chronic effects. One company scientist called the situation “[A] quite terrible problem,” for which “some plan could be made. . .”

Paraquat Parkinson’s Lawsuits

Those insiders’ fears are now coming home to roost. Thousands of Paraquat Parkinson’s lawsuits have now been filed by people who allege they developed Parkinson’s from long-term or chronic exposure to paraquat. The plaintiffs are suing Syngenta, as well as Chevron USA, which became the main US paraquat distributor from 1966 to 1986. Both of the Defendants deny liability. They both claim scientific evidence fails to support any paraquat link to Parkinson’s.

Syngenta issued a statement: “Recent thorough reviews performed by the most advanced and science-based regulatory authorities, including the United States and Australia, continue to support the view that paraquat is safe.”

A Chevron-issued statement said: “[Chevron] will vigorously defend against the allegations in the lawsuits.”

As part of a court-ordered disclosure in the litigation, the companies provided plaintiffs’ lawyers with decades of internal records that included hand-written memos, typed memos, internal presentations, emails to and from scientists, lawyers, and company officials worldwide. The files have not yet been made public through the court system.

Related: Parkinson’s Disease and Pesticides Linked: Experts

The New Lede and the Guardian report that the documents show that scientists with Syngenta predecessor Imperial Chemical Industries Ltd. (ICI) and Chevron Chemical were aware in the 1960s and 70s that evidence was increasingly proving paraquat could accumulate in the brain.

When Syngenta’s own internal research showed adverse effects of paraquat on brain tissue, the company withheld that information from regulators while downplaying the validity of similar findings from separate independent scientists.

Records also show Syngenta scientists were aware of evidence that paraquat exposure could impair the central nervous system (CNS), and could trigger tremors and other symptoms in experimental animals similar to those suffered by people with Parkinson’s disease. A 1975 Chevron communique reveals company concerns over “alleged permanent CNS effects from paraquat.”

Syngenta Influencing Strategy

The documents also describe what Syngenta called an “influencing” strategy “that proactively diffuses the potential threats that we face” and to “maintain and safeguard paraquat registrations.” The strategy “must consider how best to influence academia, and regulatory and NGO environments.”

A 2003 Syngenta “Regulatory Strategy” document calls paraquat a “blockbuster product” that must be “vigorously” defended to protect more than $400 million in annual sales. The records show that ensuring what Syngenta called its “Freedom to Sell” paraquat was a top priority.

Syngenta also built a website to publicly dismiss concerns about any paraquat Parkinson’s disease link and provide positive product propaganda. The company asserted on its new site that paraquat did not readily cross the blood-brain barrier; however, Syngenta’s own evidence from animal and human data showed paraquat accumulated in brain tissue. That language has since been taken down from the propaganda site.

Related: Pesticide Lawsuit | Attorney

“It is highly unethical for a company not to reveal data they have that could indicate that their product is more toxic than had been believed,” said Bruce Blumberg, professor of developmental and cell biology at the University of California, who spoke generally about corporate conduct. “[These companies are] trying to maximize profits and they jeopardize public health and it shouldn’t be allowed. That is the scandal.” 

Paraquat Ubiquitous Across the Country

Paraquat is one of the world’s most widely used weed killing chemicals. It competes with other pesticides such as glyphosate, the active ingredient in Monsanto’s Roundup. Farmers use it first to control weeds before planting their crops, and second to “dry out” crops for harvest. Paraquat is sprayed in U.S. orchards, wheat fields, pastures where livestock graze, cotton fields, and other agricultural areas. The use of paraquat has surged in recent years as weeds have become more resistant to Roundup and glyphosate.

Government data shows paraquat use in the U.S. has more than tripled from 1992 to 2018. 

Paraquat was banned in the EU in 2007. A court there found safety concerns that included evidence linking Parkinson’s to paraquat. The poison is also banned in the UK, even though it is manufactured there. It was banned in Switzerland, Syngenta’s home country, in 1989. It is even banned in China, the home base for ChemChina, which purchased Syngenta five years ago.

In the US, however, the EPA has mostly agreed with Syngenta and other chemical giants that claim paraquat can be safely used. The EPA said in 2021 that it would continue to let farmers spray paraquat from airplanes. Several environmental and health advocacy groups challenged the EPA in federal court for rubber stamping paraquat. They argued the EPA has ignored overwhelming scientific evidence of the risks paraquat poses to human health, including a paraquat Parkinson’s link. In response to that pressure in late September 2022, the EPA said it would reconsider its position on paraquat.


  • Parkinson’s Lawsuit – Paraquat Pesticide
  • Parkinson’s Pandemic Linked to Toxic Chemicals, says Dutch Neurologist
  • Paraquat Lawsuits Pending
  • Do Pesticides cause Parkinson’s?
  • Paraquat Lawsuit Update – August 2022

by Matthews & Associates

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