Secret Push to Bury Paraquat’s Link to Parkinson’s Disease

Paraquat is an herbicide and registered desiccant that has been used on American farms since 1964. A desiccant is a chemical that speeds up the ripening of the crop and dries it out, which facilitates harvesting and allows it to be harvested sooner than were the crop left to dry naturally.

Desiccation is also used to improve profits, as farmers are penalized when the grain contains moisture. The greater the moisture content of the grain at sale, the lower the price they get.

While 50 countries have banned paraquat due to its extreme toxicity and adverse effects on health (a single sip is lethal to a human¹), the chemical remains legal in the U.S., provided farmers receive training on its application. Proper application doesn’t ensure its safety, however, as recent lawsuits by thousands of farmers make clear.

Paraquat Linked to Parkinson’s Disease

A considerable body of evidence² links paraquat to Parkinson’s disease and, as of mid-March 2023, 2,998 lawsuits filed by farmers with Parkinson’s disease had been consolidated in Illinois federal court. The first bellwether trial is scheduled to begin in October 2023.³

The farmers are suing Syngenta, the lead manufacturer, and Chevron, a key distributor, arguing the herbicide caused their disease, and that the manufacturer was aware of this risk and concealed it from the public.

The discovery process has unearthed a trove of documents⁴ showing Syngenta has indeed known that paraquat poses neurological risks and feared the possibility of lawsuits for decades.

Most of the paraquat lawsuits are taking place in Illinois federal court, but class actions have also been filed with state courts in California, Florida, Pennsylvania, and Washington. The first state court trial is scheduled to begin in September 2023 in California.⁵ As reported by the Miller & Zois law firm, which is handling paraquat cases in all 50 U.S. states:⁶

“Parkinson’s disease is a progressive neurodegenerative disorder of the brain that affects primarily the motor system, the part of the central nervous system that controls movement.

The characteristic symptoms of Parkinson’s disease are its ‘primary’ motor symptoms: resting tremor; bradykinesia (slowness in voluntary movement and reflexes); rigidity; and postural instability. There is currently no cure for Parkinson’s disease.

Existing treatments do not slow or stop their progression; such treatments are capable only of temporarily and partially relieving motor symptoms. These treatments also have unwelcome side effects the longer they are used.

Paraquat is a toxic chemical that is a highly effective plant killer. Unfortunately, the same properties that make paraquat toxic to plant cells also make it highly damaging to human nerve cells and create a substantial risk to anyone who uses it.

Oxidative stress is a major factor in — if not the precipitating cause of — the degeneration and death of dopaminergic neurons which is the primary pathophysiological cause of Parkinson’s disease.

Paraquat is designed to injure and kill plants by creating oxidative stress, which causes or contributes to causing the degeneration and death of plant cells. Similarly, Paraquat injures and kills animals by creating oxidative stress, which causes the degeneration and death of animal cells.

The causal link between Paraquat and Parkinson’s disease is well established. Hundreds of animal studies involving various routes of exposure have found that paraquat creates oxidative stress that results in pathophysiology consistent with that seen in human Parkinson’s disease.

Many epidemiological studies have also found an association between Paraquat exposure and Parkinson’s disease, including multiple studies finding a two- to five-fold or greater increase in the risk of Parkinson’s disease in populations with occupational exposure to paraquat compared to populations without such exposure.”

Attorneys working on these cases have also highlighted recent research⁷ linking paraquat exposure to end stage renal disease,⁸ so it’s possible that the litigation effort against Syngenta might expand even further.

Syngenta Obfuscated the Evidence

In a June 2, 2023, article⁹ in The Guardian, journalist and author Carey Gillam reviews evidence from the paraquat lawsuits showing Syngenta has known about the chemical’s risk to human health for decades, and went out of its way to bury that evidence.

Some of the research¹⁰ out there suggests lifetime exposure to paraquat raises your risk of Parkinson’s by as much as 250% (odds ratio 2.5), primarily through oxidative stress. In the 2020 book, “Ending Parkinson’s Disease: A Prescription for Action,” four leading neurologists also cite paraquat as a causative factor for the condition.¹¹

Not surprisingly, Syngenta relied on the same strategies developed and perfected by the tobacco industry in years past. While independent researchers kept linking paraquat to Parkinson’s disease, Syngenta sowed doubt by maintaining the evidence was “fragmentary” and “inconclusive,” even though it wasn’t.

Indeed, internal documents obtained during the discovery process reveals Syngenta knew that paraquat accumulated in the human brain and could permanently impair the central nervous system.^12,13,14 As reported by Gillam:¹⁵

“Though it worked to publicize research that supported paraquat safety, Syngenta kept quiet about a series of in-house animal experiments that analyzed paraquat impacts in the brains of mice, according to company records and deposition testimony.

Scientists who study Parkinson’s disease have established that symptoms develop when dopamine-producing neurons in a specific area of the brain called the substantia nigra pars compacta (SNpc) are lost or otherwise degenerate. Without sufficient dopamine production, the brain is not capable of transmitting signals between cells to control movement and balance.

The Syngenta scientist Louise Marks did a series of mouse studies between 2003 and 2007 that confirmed the same type of brain impacts from paraquat exposure that outside researchers had found. She concluded that paraquat injections in the laboratory mice resulted in a ‘statistically significant’ loss of dopamine levels in the substantia nigra pars compacta.”