Parkinson’s disease

August 22, 2023

Science takes center stage in court hearing over paraquat and Parkinson’s disease

By Carey Gillam

Testimony is underway this week in a key federal court hearing aimed at examining scientific evidence about allegations that a widely used weedkiller called paraquat causes Parkinson’s disease.

The outcome of the hearing, which began Monday and runs through Thursday in East St. Louis, Illinois, is critical for thousands of people with Parkinson’s who are suing paraquat maker Syngenta AG and former paraquat distributor Chevron.

The plaintiffs claim scientific research shows that exposure to paraquat significantly increases the risk of Parkinson’s disease, but instead of warning users the companies prioritized paraquat sales over human health. The first trial is scheduled to start in October.

When this week’s hearing concludes, US District Court Chief Judge Nancy Rosenstengel will determine whether or not the plaintiffs’ experts and their scientific analyses will be allowed as evidence in the upcoming trials. Syngenta and Chevron are asking the judge to bar each of the plaintiffs’ scientific experts from testifying, saying their experience is lacking and their analyses are deeply flawed. If the judge agrees, the plaintiffs’ cases could be virtually unwinnable.

More than 4,600 plaintiffs are part of the multidistrict litigation (MDL) being overseen by Rosenstengel. More cases are pending in different jurisdictions around the US.

Syngenta and Chevron deny paraquat causes Parkinson’s and are fighting the lawsuits. The companies say the weight of scientific evidence demonstrates no causal link between the chemical and the disease.

Plaintiff’s lawyers told the judge their case will rely in part on years of animal studies showing that paraquat interacts in the brain to kill specific cells in a manner that is a hallmark of Parkinson’s disease. Human studies also support their case, the lawyers said. When the cases go to trial, they plan to present testimony from several expert witnesses supporting their allegations.

On Tuesday, the hearing turned to testimony by one of those expert witnesses – Cornell professor of epidemiology Martin Wells. Under oath, Wells told the judge that his analysis of years of published research led him to conclude that people exposed to paraquat have a risk of developing Parkinson’s disease that is substantially higher than for people not exposed to the weed killer.

Wells calculated an odds ratio of 2.8 with respect to paraquat’s causal relationship to Parkinson’s disease, meaning the risk of disease resulting from paraquat exposure was 180 times higher than the odds absent that exposure.

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June 2, 2023

Syngenta’s “SWAT” team- Internal files reveal secret strategies to influence science

By Carey Gillam
Global chemical giant Syngenta has sought to secretly influence scientific research regarding links between its top-selling weed killer and Parkinson’s, internal corporate documents show.

While numerous independent researchers have determined that the weed killer, paraquat, can cause neurological changes that are hallmarks of Parkinson’s, Syngenta has always maintained that the evidence linking paraquat to Parkinson’s disease is “fragmentary” and “inconclusive.”

But the scientific record they point to as proof of paraquat’s safety is one that Syngenta officials, scientists and lawyers in the US and the UK have worked over decades to create, and at times, covertly manipulate, according to the trove of internal Syngenta files reviewed by the The New Lede in a collaboration with The Guardian.

The files reveal an array of tactics, including enlisting a prominent UK scientist and other outside researchers who authored scientific literature that did not disclose any involvement with Syngenta; misleading regulators about the existence of unfavorable research conducted by its own scientists; and engaging lawyers to review and suggest edits for scientific reports in ways that downplayed worrisome findings.

The files also show that Syngenta created what officials called a “PQ SWAT team” to be ready to respond to new independent scientific reports that could interfere with Syngenta’s “freedom to sell” paraquat. The group, also referred to as Paraquat Communications Management Team,” was to convene “immediately on notification” of the publication of a new study, “triage the situation,” and plan a response, including commissioning a “scientific critique.”

A key goal was to “create an international scientific consensus against the hypothesis that paraquat is a risk factor for Parkinson’s disease,” the documents state.

In another example of a company tactic, an outside lawyer hired by Syngenta to work with its scientists was asked to review and suggest edits on internal meeting minutes regarding paraquat safety. The lawyer pushed scientists to alter “problematic language” and scientific conclusions deemed “unhelpful” to the corporate defense of paraquat.

March 14, 2023

Common dry-cleaning chemical could be a cause of Parkinson’s disease, scientists say

A chemical commonly used to dry clean clothes could be key contributor to the sharp rise in the spread of Parkinson’s disease in the United States, according to a paper published on Tuesday.

Twelve scientists specializing in medical research said they found important “circumstantial” evidence linking the chemical trichloroethylene (TCE) to the doubling of global instances of Parkinson’s disease over the past 30 years. In their paper, published in the Journal of Parkinson’s Disease, the scientists called for much more research and regulation of TCE, warning that “widespread contamination and increasing industrial, commercial and military use,” pose a dire public health threat.

“TCE may be the most important cause of Parkinson’s disease in urban environments in the US,” said Ray Dorsey, a neurologist at the University of Rochester Medical Center and the lead author on the paper.

TCE is one of multiple environmental pollutants implicated in the rise of Parkinson’s disease. Research has also linked particulate air pollution and certain pesticides, including paraquat herbicide, to the disease. Head trauma and genetic factors also play a role, according to research findings.

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March 7, 2023

Guest Column: Paraquat and the deliberate production of ignorance

By E. Ray Dorsey, M.D., and Amit Ray, Ph.D

Nearly 60 years ago, a chemical company found that skin exposure to very high doses of its weedkiller paraquat caused “weakness and incoordination” in rabbits. Large amounts of the herbicide, which is used on corn, cotton, and vineyards, caused some mice and rats in its labs to develop a stiff gait or tremors. A decade later, an autopsy of a farm worker exposed to paraquat showed “degenerative change” in the “cells of the substantia nigra,” a pathological hallmark of Parkinson’s disease.

Rather than remove this dangerous chemical from the market or develop a safer alternative, the company doubled down on its “blockbuster” product and sought to expand its use. Along the way, the company appeared to use techniques to underestimate the toxic effects of the chemical, hide the results of its own research from regulatory authorities, and discredit the research of an academic investigator and prevent her from serving on a U.S. Environmental Protection Agency (EPA) advisory panel.

The company’s alleged efforts seem to have worked brilliantly. Despite numerous animal and epidemiological studies linking the environmental toxicant to Parkinson’s disease, paraquat’s use in the United States from 2013 to 2018 more than doubled. As pesticides can contaminate drinking water and pollute the air their harmful effects are not limited to farmers but extend (at least) to other rural residents who also have a higher risk of developing Parkinson’s disease. Because of its health risks, over 30 countries—including China—have banned paraquat. Yet in 2021 the EPA reauthorized its use even though its own website says, “One Sip Can Kill.”

February 24, 2023

Evidence mounts linking air pollution to Parkinson’s disease

By Grace van Deelen

New research adds to evidence that people living in areas with high air pollution are at a higher risk of developing Parkinson’s disease, a progressive neurological disorder.

The research found a nationwide association between incidents of Parkinson’s and annual average particulate matter air pollution, also known as PM 2.5. Researchers found that at the highest annual exposure level, participants were 25% more likely to develop Parkinson’s disease, compared to those with the lowest exposure.

The findings are expected to be presented at the American Academy of Neurology’s meeting in April and published in the journal Neurology. The work was funded by grants from the US Department of Defense, the National Institutes of Health National Institute of Environmental Health Sciences, and the Michael J. Fox Foundation for Parkinson’s Research.

“It’s a very compelling story that we see,” said Brittany Krzyzanowski, a scientist at the Barrow Neurological Institute and lead author on the new study.

Researchers used data from over 22 million Americans, 83,674 of whom had reported a Parkinson’s diagnosis. They analyzed that data alongside geographical data showing the amount of PM 2.5 in the atmosphere. PM 2.5 is a type of air pollution that comes from vehicle exhaust, forest and grass fires, and other industrial processes, meaning that communities near highways and industrial areas are most likely to have high exposure.

The link between the disease and PM 2.5 has been suggested in numerous other studies, including a 2022 review of existing research that found air pollution to be “an emerging risk factor in the development of Parkinson’s disease.”

As well, a 2018 study of more than 2 million Ontario adults found that long-term exposure to PM 2.5 was associated with a 4% increase in instances of Parkinson’s, while a 2020 study of 63 million US adults found an association between PM 2.5 exposure and hospitalization for Parkinson’s.

February 6, 2023

Bill to strengthen pesticide protections offers farm bill “wish list”

By Shannon Kelleher

Advocates are cheering US Senator Cory Booker’s recent move to reintroduce a bill that would strengthen legal protections against dangerous pesticides used in agriculture. However, the bill may face a steep uphill journey towards being signed into law.

The measure, titled “Protect America’s Children from Toxic Pesticides Act of 2023” (PACTPA) would ban several widely used pesticides that have been linked through scientific research to a number of human and environmental health problems.

“We’d like to see the Senate and House agriculture committees look at this as a wish list,” said Christina Stucker-Gassi, a program manager at the Northwest Center for Alternatives to Pesticides. “They have the budget, they have the authority to look at that wish list and advance on some of [these issues] within the [2023] Farm Bill process,” she said, referring to a package of legislation passed every five years that could be one channel for moving PACPTA priorities forward.

PACPTA would especially benefit children, farmworkers, and rural communities, who suffer disproportionately from exposure to these toxic chemicals, according to Stucker-Gassi. The bill would help enable local communities to enact their own protective legislation against harmful pesticides and would put in place strict rules requiring employers of farmworkers to report pesticide-related injuries.

“It’s high time that farmworkers are included within the farm bill in substantial ways,” said Stucker-Gassi.

Booker initially introduced the bill in 2021 but it failed to gain traction amid strong resistance from powerful farm lobbying groups and the agrochemical industry, which reaps billions of dollars in revenues from pesticide sales.

October 27, 2022

Amid calls for ban on weed killer linked to Parkinson’s, a battle over science

By Carey Gillam

When US regulators issued a 2019 assessment of the widely used farm chemical paraquat, they determined that even though multiple scientific studies linked the chemical to Parkinson’s disease, that work was outweighed by other studies that did not find such links. Overall, the weight of scientific evidence was “insufficient” to prove paraquat causes the brain disease, officials with the US Environmental Protection Agency (EPA) declared.

The EPA reiterated its assessment in a 2021 report. The agency said after extensive analysis of numerous factors, including concerns about Parkinson’s risk, it determined farmers could safely continue to apply the weed killer across millions of US acres to help in the production of soybeans, corn, cotton and an array of other crops.

The determination has been significant for Syngenta, the longtime maker of paraquat weed killers. The company is facing calls in the US for a paraquat ban, as well as more than 2,000 legal claims brought by farmers and others alleging they developed Parkinson’s disease because of their exposure to paraquat.

Syngenta cites the EPA assessment of the science on paraquat in defense of the pesticide, and says scientific research “does not support” a causal relationship between the chemical and the disease. On a Syngenta-run paraquat information website, the company highlights several studies it says also backs that position, including many conducted by company scientists or by outside scientists who received company funding for their work.

Last week the Guardian and The New Lede reported that internal corporate records show Syngenta had knowledge of science linking paraquat to Parkinson’s decades ago but sought both to refute the evidence with various secret tactics. The documents are available at the Paraquat Papers Media Library.

US farmworker, health and environmental advocacy groups say in contrast to the corporate science, research conducted by independent scientists provides abundant evidence of paraquat’s ability to cause Parkinson’s and other health dangers, and the EPA is improperly discounting that body of research.

More than 50 groups have called for the US to follow the lead of dozens of other countries in banning paraquat. The Michael J. Fox Foundation for Parkinson’s Research submitted a petition to the EPA with 107,000 signatories calling for a ban. The foundation cited a study that found people exposed to paraquat in their teens or as young adults had an increased Parkinson’s risk of 200 to 600 percent, depending on the overall exposure.

October 20, 2022

Secret “Paraquat Papers” reveal corporate tactics to protect weed killer linked to Parkinson’s disease

By Carey Gillam and Aliya Uteuova

For more than 50 years, Swiss chemical giant Syngenta has manufactured and marketed a widely used weed killing chemical called paraquat, and for much of that time the company has been dealing with external concerns that long-term exposure to the chemical may cause the dreaded, incurable brain ailment known as Parkinson’s disease.

Syngenta has repeatedly told customers and regulators that scientific research does not prove a connection between its weed killer and the disease, insisting that the chemical does not readily cross the blood-brain barrier, and does not affect brain cells in ways that cause Parkinson’s.

But 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 at times contradicted the company’s own research and knowledge.

And though the documents reviewed do not show that Syngenta’s scientists and executives accepted and believed that paraquat can cause Parkinson’s, they do show a corporate focus on strategies to protect product sales, refute external scientific research and influence regulators.

In one defensive tactic, the documents lay out how the company worked behind the scenes to try to keep a highly regarded scientist from sitting on an advisory panel for the US Environmental Protection Agency (EPA). The agency is the chief US regulator for paraquat and other pesticides. Company officials wanted to make sure the efforts could not be traced back to Syngenta, the documents show.

And the documents show that insiders feared they could face legal liability for long-term, chronic effects of paraquat as long ago as 1975. One company scientist called the situation “a quite terrible problem,” for which “some plan could be made….”

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May 26, 2022

EPA backing of pesticide poses human health risks, groups allege

The Environmental Protection Agency (EPA) is risking the health of farmworkers and other Americans by allowing continued widespread use of a highly toxic pesticide called paraquat that has been linked to Parkinson’s disease and other health problems, a coalition of advocacy groups alleged in court filings this week.

The group of eight organizations is challenging a 2021 EPA decision that the group’s allege violates federal law. They say the EPA failed to adequately account for the “magnitude” of the risks posed by paraquat use, and improperly determined that the benefits of paraquat for crop production outweigh the dangers to farmworkers and others.

May 10, 2022

Guest column: Syngenta’s paraquat product kills weeds, but also people

By Jon Heylings

From 1986 until 2008, I worked as the lead scientist on a project aimed at creating a “safer” paraquat-based weed killing product for what was then known as the ICI Central Toxicology Laboratory, which became part of Syngenta AG in 2000.