A Guide to Paraquat: The Next Big Mass Tort

Anjelica Cappellino, J.D.

Written by
— Updated on August 31, 2021

A Guide to Paraquat: The Next Big Mass Tort

Over a dozen lawsuits are pending against several manufacturers of Paraquat. The suits allege that exposure to the highly toxic herbicide causes Parkinson’s disease. Paraquat’s toxicity is far from new information. It’s highly regulated and can only be used by licensed professionals. But its causal connection to Parkinson’s disease is a recent development. A number of studies have suggested that exposure to the herbicide increases one’s risk of the disease. As research continues to develop and new information emerges, the Paraquat lawsuits have the potential to become momentous mass tort litigation. Attorneys will want to keep an eye on these product liability developments.

What is Paraquat?

Paraquat dichloride is a popular herbicide used for the control of weeds and cotton desiccation. Chevron Chemical Company and Growmark, Inc. are among the Paraquat manufacturers in the United States. Another producer, Syngenta, manufactures Gramoxone, the most common trade name for the chemical. It has been on the market for over 60 years and is used on more than 100 crops. These include household staples such as corn, soybeans, peanuts, almonds, garlic, pears, strawberries, grapes, artichokes, and sweet potatoes.

Paraquat Popularity

Paraquat successfully destroys weeds that are resistant to glyphosate (found in Monsanto’s Roundup weed killer—another notable subject of litigation). This weedkilling ability has only made it more popular. Over the past 25 years, Paraquat use in the United States has risen higher than ever. In fact, use has increased nearly 200% since 2009. Farmers in the U.S. use more than eight million pounds of Paraquat per year. Paraquat is, however, considered a Restricted Use Pesticide (RUP). Only trained and certified applicators may use it. Further, the products are unavailable for use in residential areas. The Federal Insecticide, Fungicide, and Rodenticide Act regulates Paraquat distribution, sale, and use. Under the Act, all purchasers must register with the U.S. Environmental Protection Agency. Internationally, European Union, China, and Brazil have all banned Paraquat.

Paraquat Toxicity

Paraquat is highly toxic and its ingestion causes death. From 1990 to 2014, there have been 200 incidents and 27 deaths from Paraquat exposure. Since 2012, there has been at least one death in the U.S. from Paraquat ingestion. Exposure can also occur via inhalation or through the skin. The extent of poisoning depends on the type of exposure, duration, and amount. Paraquat causes toxic chemical reactions throughout the body, primarily in the heart, lungs, liver, and kidneys. Additionally, Paraquat poisoning may lead to organ failure.

Attention to Paraquat’s link to Parkinson’s disease is somewhat novel. But the momentum of this theory has been gradually building over the past decade. In 2009, the American Journal of Epidemiology released a study indicating that Paraquat may cause a neurodegenerative process leading to Parkinson’s disease. The study found that exposure to Paraquat and maneb (another pesticide) within 500 meters of one’s home increased the risk of the disease by 75%.

JAMA (Journal of the American Medical Association) Neurology also published a study that year finding that “the association of disease risk with pesticides support a toxicant-induced cause of parkinsonism.” Then in 2011, the National Institute of Environmental Health Sciences published a study finding that Parkinson’s disease was strongly associated with Paraquat. It identified that farmworkers received a Parkinson’s diagnosis at a rate of 2.5 times higher than those not exposed to the chemical. The authors noted that exposure was not limited to occupational or agricultural environments. This broadens the potential reach of exposure.

EPA Review

More recently, the Unified Parkinson’s Advocacy Council reached out to U.S. Environmental Protection Agency in regards to the Paraquat issue. The Council’s outreach was intentionally in advance of the agency’s registration review of Paraquat. On July 24, 2017, the Council sent a letter to the EPA highlighting the alarming studies and urging the EPA to deny Paraquat’s reregistration.

In its 2019 draft human health risk assessment, the EPA found “insufficient evidence to link” Paraquat products to Parkinson’s Disease. In October 2020, it released its Proposed Interim Decision which suggested several mitigation measures to reduce exposure. Likewise, although the Centers for Disease Control and Prevention recognize Paraquat’s high toxicity, it has not drawn any conclusions concerning its link to Parkinson’s.

The Lawsuits (So Far)

Currently, there are at least 20 lawsuits pending in six different federal district courts. They each allege similar causes of action against Chevron, Syngenta, and other Paraquat manufacturers. One of the first lawsuits was filed in October 2017 against Syngenta and Growmark (and later adding Chevron Chemical as a defendant). None of the lawsuits have settled nor gone to trial.

One plaintiff filed his lawsuit, Rakoczy v. Syngenta Crop Protection LLC, et al., in the U.S. District Court for the Northern District of California. Here, the plaintiff alleges he was “repeatedly exposed to and inhaled, ingested, or absorbed Paraquat” between 2013 and 2017. The plaintiff subsequently received a Parkinson’s diagnosis on or about December 1, 2015. However, he was never aware of any associations between Parkinson’s and Paraquat. Further, he wasn’t aware that exposure could cause any latent neurological injuries which would require precautionary measures. The plaintiff alleges that Paraquat is unreasonably dangerous. Allegedly, its design leads to greater inhalation, ingestion, and absorption to the body. This, in turn, makes it more likely to cause latent neurological damage.

Negligence & Liability Claims

Similar lawsuits have been filed under negligence and strict liability theories. This is the case for plaintiff James Hemker, who developed Parkinson’s disease in 2008 after years of exposure to Syngenta and Chevron products. One plaintiff’s attorney, Steve Tillery, has taken the allegations a step further. He recently asserted that he has obtained internal documents that show Syngenta knew about its product’s risks but failed to do anything.

Most recently, a Missouri federal court judge denied the defendants’ motion to dismiss a similar complaint. Syngenta and Chevron argued that the plaintiffs’ claims were preempted by federal law governing EPA regulations of Paraquat. The defendants assert that Paraquat is safe for use so long as “EPA-prescribed precautions are taken and instructions are followed.” They further allege that additional labeling requirements would be in violation of the Federal Insecticide, Fungicide, and Rodenticide Act. The district court was not persuaded, holding that registration approval by the EPA is not an absolute defense to claims of mislabeling. It also noted that EPA approval doesn’t preempt failure to warn claims brought under state law.

On April 7, 2021, plaintiff Paul Rakoczy submitted a motion with the United States Judicial Panel on Multidistrict Litigation seeking to consolidate and transfer the lawsuits against Chevron and Syngenta to the Northern District of California. In the motion, the plaintiff argues that these actions involve common questions of law and facts concerning paraquat-induced Parkinson’s disease. The decision is pending.

How Can the Experts Help?

Like any product liability case of this nature, one of the major questions will be whether Paraquat is unreasonably dangerous. Further, these cases will seek to determine whether the manufacturers failed to adequately warn the consumers.

Although it is indisputable that Paraquat is toxic, whether it causes Parkinson’s disease is another matter. The studies, so far, have been telling. A majority of the research has found a causal connection between the herbicide and the disease. However, some studies have not found any clear links. This includes one study recently published in 2020 that did not find strong evidence of a causal relationship.

Environmental Science

Experts in agricultural and environmental science will be of particular importance in the litigation. This expertise is highly relevant since the risk of Paraquat exposure is most common in commercial agricultural settings. Farmworkers and other agriculturalists experience the most direct exposure to the herbicide. As such, it’s necessary for researchers to continue their probe in this field.


As previous studies have found that even low-level Paraquat exposure can adversely impact a person, toxicologists will be needed during litigation. This expertise can establish exactly how this exposure is occurring. In order for any theories of latent exposure to be advanced, especially to those that do not directly work with the herbicide, the nature of Paraquat’s toxicity will become an issue even greater than it already is. The effects of Paraquat on both specialized fields and the general population of a whole will likely require an in-depth epidemiological study.


Lastly, it is important to remember that the direct cause of Parkinson’s disease has long evaded the scientific community. Genetics is only partially responsible for this progressive, chronic neurological disease. Research has found that genes play a role in only a small percentage of cases. Rather, the main cause of Parkinson’s disease is environmental factors. As previous studies have found, Paraquat creates “oxidative stress” that results in the degeneration and death of neurons. This finding led to the subsequent study of its link to Parkinson’s. It’s inevitable that neurologists, especially those within the subspecialty of Parkinson’s research, will be at the forefront of the litigation.

Paraquat remains a popular herbicide in this country. This potentially exposes millions of people to the chemical. Given its prevalence in agriculture and growing litigation attention, it’s likely Paraquat litigation is still in its infancy.



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