What Is Paraquat?

Paraquat dichloride, commonly referred to as “paraquat,” is one of the most widely used herbicides in the U.S. It was initially manufactured and sold by Imperial Chemical Industries (ICI) of the United Kindom and its subsidiaries. Manufacturer Chevron (previously known as the California Chemical Company) handled the sales in the U.S. through 1986 and was engaged with ICI in all aspects of the paraquat business from early on.

The herbicide became available in the U.S. in the 1960s. Since then, farmers have used it to kill broadleaf weeds and grasses before the planting or emergence of more than 100 field, fruit, vegetable, and plantation crops; to control weeds in orchards, and; to desiccate crops like cotton before harvest. Workers spray it directly on the plants using knapsack and handheld sprayers, aircraft, and trucks or tractors with attached pressurized tanks.

Companies that have manufactured or sold paraquat under various brand names:

• Syngenta
• Chevron Chemical Company
• Adama Group
• Altitude Crop Innovations, LLC
• Drexel Chemical Company
• United Phosporous
• Helm Agro
• Sinon USA, Inc.
• Innvictis Crop Care LLC

These companies and others make paraquat products to sell throughout the country, most of which contain about 44 percent paraquat. Popular brand names include:

• Blanco
• Gramoxone
• Quik-Quat
• Bonfire Herbicide
• Helmquat 3SL
• Bonedry
• Devour
• Para-Shot 3.0
• Cycline SL 2.0
• Firestorm
• Parazone

How Does Paraquat Work?

Paraquat is an organic salt that acts quickly on contact, locking onto leaves and stems, killing both grasses and broadleaf plants. It interferes with part of the photosynthesis process, taking electrons from a protein called ferredoxin. These electrons are transferred to oxygen, producing highly reactive superoxide free radicals—damaging and unstable types of atoms.

These superoxide free radicals then attack the fatty acids in the cell membrane, disintegrating the membrane and tissues. This causes the green parts of the plant to dry out as water escapes from the damaged membranes and the plant rapidly dies.

This ability to disrupt normal electron transfer has not gone unnoticed by scientists, who sometimes use paraquat in the laboratory to produce superoxide free radicals. Paraquat is highly toxic, but it leaves very little residue on crops and is inactivated on contact with almost all naturally occurring soils.

Common Paraquat Health Risks

Paraquat can affect human cells the same way it does plant cells. It creates free radicals and oxidative stress, damaging cells and causing cell death. It is so toxic to humans that the U.S. Environmental Protection Agency (EPA) has restricted its use to only those who have undergone specific training to become licensed applicators. During certification training, individuals learn about the toxicity of the herbicide, as well as the consequences of misuse.

Only those who can prove they are certified applicators can purchase and use paraquat products—they are not supposed to be employed for residential use. Despite these precautionary measures, occupational exposure may still occur during the mixing, loading, and application of the herbicide, or during the post-application process. Residential exposure may occur for those living near farms where the herbicide has been applied, according to the National Institutes of Health (NIH).

Paraquat is considered highly toxic to humans when it is inhaled, as it can accumulate in lung tissues and cause:

• lung damage
• acute respiratory distress syndrome (ARDS)
• a lung disease called paraquat lung
• scarring on the lungs called pulmonary fibrosis

Because of this danger, the herbicide has been placed in Toxicity Category I (the highest of four levels) for acute inhalation effects. The EPA has determined that particles used in agricultural practices, however, “are well beyond the respirable range and therefore inhalation toxicity is not a toxicological endpoint of concern.”

One Sip Can Be Fatal: EPA Actions on Paraquat

Paraquat can toxicity when ingested as well, which can accidentally occur during mixing and loading paraquat for use, or if paraquat is stored in unlabeled containers. If paraquat touches the lining of the mouth, stomach, or intestines, it can damage the esophagus, kidneys, liver, and more. If it touches a cut on the skin, it can also create health problems.

In 2013, the California Poison Control System and the American Association of Poison Control Centers (AAPCC) sent letters of concern to the EPA regarding a series of deaths from accidental ingestion of paraquat.

Though the restricted pesticide should not be accessible to the general public, somehow it was found in unlabeled containers and accidentally ingested. The EPA warned that one sip could be fatal and “there is no antidote.”

In 2016, the EPA took action to minimize accidental paraquat ingestions and to reduce exposure to workers who mix, load, and apply the herbicide. These included:

• Changing the product label and distribution of additional warning materials to highlight the toxicity and risks associated with paraquat.
• Restricting the use of paraquat to certified applicators only. Individuals working under the supervision of a certified applicator were no longer allowed to use the herbicide.
• Requiring specialized training for certified applicators to emphasize that the chemical should never be transferred to or stored in improper containers.
• Requiring new closed-system packaging designed to prevent spills, mixing or pouring the pesticide into other containers, or other actions that could lead to paraquat exposure.

After Public Comments, the EPA Takes Further Action on Paraquat

On July 24, 2017, the Unified Parkinson’s Advocacy Council (led by the Michael J. Fox Foundation) sent a letter to the EPA urging the agency to deny paraquat’s reregistration because of its potential to increase the risk of PD.

The EPA did not agree, but it did take a second look at the herbicide. In October 2019, the agency released an updated draft of the human health and ecological risk assessments for public comments. The agency noted that it found no dietary risks associated with paraquat when used according to the label instructions, but that it had identified potential risks to workers who apply it or enter treated fields after application.

“There are also potential risks from spray drift to bystanders at the edge of the field,” the EPA stated.

Based on public comment on the 2019 draft, the EPA released in October 2020 the Proposed Interim Decision. In this document, the EPA proposed additional protections to reduce exposure to paraquat, including:

• prohibiting aerial application except when desiccating cotton fields
• prohibiting pressurized handgun and backpack sprayer application methods
• limiting the maximum application rate for alfalfa
• requiring enclosed cabs or PF10 respirators if the area treated in a 24-hour period is 80 acres or less
• adding mandatory spray drift management label language

Then on August 2, 2021, the EPA announced that it was finalizing these new, stronger safety measures to reduce exposure to paraquat.

How is Paraquat Connected to Parkinson’s Disease?

Currently, the EPA states that “there is insufficient evidence to link registered paraquat products to any of the health outcomes investigated, including Parkinson’s Disease, when used according to the label.”

Several scientific studies, however, have come to different conclusions. Many have linked pesticides, in general, to PD. In 2000, for instance, researchers reported that people exposed to pesticides in the home or garden may have a significantly higher risk of PD. Several more studies both before and after this one showed that occupational exposure to these chemicals—particularly among farmers and farm workers—was a risk factor for the disease.

Meanwhile, studies specifically on paraquat have also suggested that it may increase the risk of PD. Animal studies have repeatedly found that paraquat can accumulate in brain tissue, and may cause nerve damage consistent with that seen in Parkinson’s Disease.

In a 2002 animal study, for instance, researchers found that paraquat injections killed dopaminergic neurons in the brain—the same neurons that are damaged in PD. “These findings,” the researchers wrote, “unequivocally show that selective dopaminergic degeneration, one of the pathological hallmarks of PD, is also a characteristic of paraquat neurotoxicity.”

In a 2005 study, scientists investigated associations between pesticide exposure and PD and found elevated incidences among farmers who used herbicides and paraquat. For a 2009 study, scientists examined data from patients with PD in the Central Valley of California and found that exposure to pesticides maneb and paraquat within 500 meters (about 1,640 feet) of the home increased the risk of PD by 75 percent.

Researchers again reported in 2011 that PD was positively associated with pesticides that impair mitochondrial function and those that increase oxidative stress, including paraquat.

Recent Studies Link Paraquat to an Increased Risk of Parkinson’s Disease

Some studies have not found a definite link between paraquat and PD. In 2010, researchers reported that paraquat had been linked to PD in epidemiological studies and animal studies, but “evidence that human exposure to the chemical results in an increased risk for PD is rather limited….”

In a later 2012 study, scientists came to the same conclusion, noting that the current literature did not provide enough evidence proving a relationship between paraquat and PD.

More recent studies, however, have turned the tables, with results lining up with earlier studies. In 2018, researchers from the University of Guelph found that low-level exposure to pesticides like paraquat and maneb disrupted cells in a way that mimicked the effects of mutations known to cause PD. Adding the effects of these chemicals to a predisposition for PD—in individuals at genetic risk for the disease, for instance—increased the risk of disease onset.

Other research suggests that it could be environmental factors like exposure to pesticides combined with a genetic susceptibility to PD that could increase the risk of the disease. In these studies, scientists found that neurotoxicity induced by paraquat (and another pesticide, rotenone) interacted with proteins to cause damage in a way similar to PD pathogenesis.

In 2019, researchers conducted a systematic review of the literature and found that PD occurrence was 25 percent higher in participants exposed to paraquat. Results from a subgroup analysis also indicated a higher PD frequency in those who were exposed to the herbicide for longer periods.

Paraquat is still used in the USA even while it has been banned or is being phased out in the European Union, China, and Brazil. With the growing evidence supporting a connection between paraquat and PD, some lawmakers are taking action. In July 2019, Representative Nydia Velasquez (D-NY) introduced the Protect Against Paraquat Act of 2019 (HR 3817) seeking to eliminate the use of paraquat in the U.S.

To learn more about the connection between paraquat and PD, see this issue of Living Safer, which provides further details.

Common Injuries Associated with Paraquat

Inhalation or ingestion of paraquat, as well as dermal (skin) contact, may result in the following injuries:

• Lung scarring and failure
• Holes or burns in the esophagus
• Inflammation and infection affecting vital organs
• Liver damage and failure
• Central nervous system damage
• Kidney failure
• Cancer
• Death

Paraquat MDL Leadership

Chaffin Luhana has a strong leadership role in the current paraquat multidistrict litigation. In July 2021, Chief U.S. District Judge Nancy J. Rosenstengel appointed founding partner Roopal P. Luhana to the Plaintiffs’ Executive Committee (PEC). In this role, Ms. Luhana will be on the front lines fighting for plaintiffs who have been harmed by paraquat manufacturers and deserve compensation.

“I am honored to be chosen by Judge Rosenstengel to help lead this important litigation on behalf of plaintiffs whose lives have been forever altered after exposure to Paraquat,” Ms. Luhana said, “and feel this really is a recognition of the exemplary work the women and men in our law firm do every day for all of our clients. My firm and I believe that those responsible for our clients’ suffering should be held accountable and we are ready to take on that fight.”

Ms. Luhana has served on several steering committees in important litigations over the past decade, including most recently having been appointed by U.S. District Judge Robin L. Rosenberg to the Plaintiffs’ Steering Committee (PSC) in the In re: Zantac (Ranitidine) Products Liability Litigation (S.D.FL.).

“Part of Chaffin Luhana’s mission is to lead in industry-impacting litigations as we have done for over a decade, and Ms. Luhana’s appointment is yet another opportunity to do so,” says Chaffin Luhana Managing Partner, Eric Chaffin.