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Gramoxone SL 2.0
Gramoxone SL 3.0
Gramoxone SL
Gramoxone Inteon
Cyclone SL 2.0
UPL Agricultural Solutions B.V.Privately Held
MacDermid Agricultural Solutions
Helm Agro US (HELM AG)
Helmquat 3SL
Parazone 3SL
Paraquat 3 SL
Atticus LLC
Purgatory 3 SL
Generic Crop Science
Willowood LLC
Willowood Paraquat 3SL
Altitude Crop InnovationsPrivately Held
Sinon Corp.
Innvictis Crop Care
Sharda USA
Para-SHOT 3.0
RedEagle International
Paraquat 43.2% SL
Source Dynamics
Paraquat Concentrate

Privately Held
Privately Held
Privately Held
$18.7 Billion
Privately Held
Privately Held
Privately Held
Privately Held
$8.73 Billion
Privately Held
Privately Held
Privately Held
Privately Held

FDA Approval 


N/A – Regulated by EPA


MDL Information 


No information at this time


There are more than 12 cases filed in Illinois and California against Syngenta involving paraquat and Parkinson’s disease.


Paraquat was synthesized in 1882 but its role as a weedicide was discovered in 1955 and commercialized in 1962 by Imperial Chemical Industries (ICI or Syngenta). Low-cost, efficient weed elimination and a unique mechanism made it popular for massive applications. Paraquat deviates electron flow from the photosystem that inhibits the reduction of oxidized nicotinamide adenine dinucleotide phosphate (NADP+) during photosynthesis to produce PQ+. Paraquat specifically targets photosynthesizing green plant parts where PQ+ is re-oxidized by the O2 produced in chloroplasts. During the re-oxidization, lethal superoxide radical (O+) is generated and its subsequent oxidation results in cell death. Paraquat is only sold to farmers. The product is diluted typically 200 times with water and sprayed onto weed foliage. It only works when in direct contact with photosynthesizing green tissue.


Treatment / Use

Paraquat herbicide has served over five decades to control annual and perennial weeds. Despite agricultural benefits, its toxicity to terrestrial and aquatic environments raises serious concerns. Paraquat cannot rapidly degrade in the environment and is adsorbed in clay lattices that require urgent environmental remediation. Herbicides containing paraquat include: Gramoxone, Firestorm, Helmquat, Parazone and others.

Injuries / Problems / Concerns

Paraquat has long been controversial because of its use in suicides in many parts of the world, since drinking one sip can be lethal. But now regulators in the United States are grappling with a wave of research linking paraquat to a less immediately apparent effect — Parkinson’s disease.  In a little noticed regulatory filing, the Environmental Protection Agency said, “There is a large body of epidemiology data on paraquat dichloride use and Parkinson’s disease.” The agency is weighing whether to continue allowing the chemical to be sprayed on American croplands.
While the possibility of a Parkinson’s link has been cited in studies going back more than two decades, research in the past five years has intensified, including a prominent study by the National Institutes of Health and meta-analyses of a large body of research.
The studies have looked at the exposure of farmers and others who spray paraquat, as well as people who live near where it is used, which can include nonagricultural settings like those around roads and rail tracks.
“The data is overwhelming” linking paraquat and Parkinson’s disease, said Dr. Samuel M. Goldman, an epidemiologist in the San Francisco Veterans Affairs health system who has studied the connection. “I’m not a farmer, I don’t need to kill weeds, but I have to believe there are less dangerous options out there.”
Freya Kamel, a scientist with a branch of the National Institutes of Health who has also studied the topic, said she found the breadth of the research “about as persuasive as these things can get.”
A research report published by in September 2020 stated that, “A considerable body of evidence was identified as relevant to paraquat exposure and Parkinson’s disease that can be used in developing future systematic reviews as were data gaps and scientific challenges that could be addressed by future research.”
Another report published on involved the ambient exposure to pesticides/herbicides and the risk of Parkinson’s disease.  “At workplaces, combined exposure to ziram, maneb, and paraquat increased risk of PD three-fold (OR: 3.09; 95% CI: 1.69, 5.64) and combined exposure to ziram and paraquat, excluding maneb exposure, was associated with a 80% increase in risk (OR:1.82; 95% CI: 1.03, 3.21).”
Similar to the use of NDMA to develop tumors in laboratory animals, paraquat has recently been considered as an eligible candidate for inducing the Parkinsonian syndrome in laboratory animals, and can therefore constitute an alternative tool in suitable animal models for the study of PD.
It is believed that Paraquat kills cells through a mechanism called oxidative stress, but how this happens has not been explained. The research team looked for genes involved in the underlying mechanism paraquat uses to produce oxidants, the chemicals that cause oxidative stress in cells.
They reasoned that the loss of function in dopamine neurons of the substantia nigra pars compacta, a small region of the brain, seen in Parkinson’s may be because they are more vulnerable to oxidative stress than other neurons. Paraquat would cause more damage to the dopamine neurons and thereby cause Parkinson’s in certain people with genetic susceptibility, they hypothesized.
A claim filed by Zurich American Insurance Company and American Guarantee and Liability Company v. Syngenta Crop Protection - Syngenta was awarded partial summary judgment for a declaratory judgment on Count I and Count II.  These counts involved the aforementioned insurance companies’ claims that due to prior action (alleged claim for damages related to paraquat and Parkinson’s disease) they did not have a duty to defend.
In its financial report for 2019, Syngenta addressed the litigation related to paraquat and Parkinson’s disease:  Paraquat Parkinson’s disease litigation - In early 2016, the law firm which is prosecuting the atrazine personal injury litigation notified Syngenta Crop Protection, LLC that they intended to file suit on behalf of numerous plaintiffs who allege that the herbicide paraquat caused them to develop Parkinson’s disease. Counsel for Syngenta spoke with and, in one instance, met with that law firm regarding the firm’s allegations, its proposal for litigating them, and its purported clients. No agreements with the firm were reached. In September 2017, a complaint was filed in St. Clair County, Illinois state court on behalf of plaintiffs Thomas Hoffman and Diana Hoffman against Syngenta Crop Protection, LLC, Syngenta AG, and Growmark, Inc. The complaint alleges that Mr. Hoffman suffers from Parkinson’s disease caused by chronic exposure to paraquat while working as a farmer in Illinois. On October 6, 2017 an amended complaint was filed in the same court on behalf of 12 plaintiffs (seven men who are said to have been diagnosed with Parkinson’s disease and five of their wives), including Mr. and Mrs. Hoffman who were named in the initial complaint, against Syngenta Crop Protection, LLC, Syngenta AG, Chevron Phillips Chemical Company, and Growmark, Inc. The amended complaint alleges the following counts: (1) Strict Liability - Design Defect; (2) Strict Liability - Failure to Warn; (3) Negligence; (4) Public Nuisance; (5) Consumer Fraud & Deceptive Business Practices Act; and (6) Breach of Implied Warranty of Merchantability. Syngenta’s Motion to Dismiss was denied in July 2018. Syngenta filed its answer to the amended complaint in October 2018. In that case, the parties are now engaged in discovery. On December 13, 2018, the same counsel filed a further complaint in St. Clair County, Illinois state court on behalf of plaintiffs Marvin Wendler and his wife against Syngenta Crop Protection, LLC, Syngenta AG, and various third parties. An additional complaint was filed by the same counsel in St. Clair County, Illinois state court on December 21, 2018, on behalf of plaintiffs Lloyd Pulcher and his wife against Syngenta AG and Growmark, Inc. These new complaints assert the same claims as the Hoffman complaint. Syngenta AG was served with these two complaints, Wendler and Pulcher, in March 2019 and filed Answers to both complaints in March 2019. In April 2019, the same plaintiffs’ counsel filed ten complaints in California state court (five in San Francisco County and five in Contra Costa County) on behalf of 16 plaintiffs (including ten men who are said to have been diagnosed with Parkinson’s disease and six of their wives). The complaints name Syngenta AG and Syngenta Crop Protection LLC, and various distributors as additional defendants. The ten California complaints allege the following counts: (1) Strict Products Liability; (2) Negligence; (3) Public Nuisance; (4) California Consumer Legal Remedies Act; and (5) Breach of Implied Warranty of Merchantability. Syngenta Crop Protection, LLC and Syngenta AG have been served with the complaints. The California plaintiffs’ petition to coordinate these California actions for pre-trial purposes has been granted and the cases remain at an early stage. Syngenta strongly believes that the claims are without merit and is vigorously defending against the actions.

Information on the Topic of Paraquat

Paraquat Dichloride – EPA Interim Decision (10-22-2020)


NTP Research Report on the Scoping Review of Paraquat Dichloride Exposure and Parkinson’s Disease: Research Report 16 [Internet] (9-2020)


Superior Court of the State of Delaware: Zurich American Insurance Company and American Guarantee and Liability Company v. Syngenta Crop Protection (8-3-2020)


New Restrictions on Widely Used Herbicide: Paraquat Dichloride (4-14-2020)


Changes to Paraquat Use Requirements and Labeling (12-18-2019)

Paraquat and Parkinson's Disease: A Systematic Review and Meta-Analysis of Observational Studies (9-2-2019)


Paraquat Degradation From Contaminated Environments: Current Achievements and Perspectives (8-2-2019)


Carolyn and Ronald C Mansfield vs Syngenta AG – Case #00669 (4-2-2019)


New Legislation Aims to Ban Herbicide Linked to Parkinson’s (2-6-2019)


Study Uncovers Cause of Pesticide Exposure, Parkinson’s Link (5-23-2018)

Cellular Senescence in Astrocytes May Play Central Role in Parkinson’s Disease



Researchers Unravel Link Between Herbicide Exposure and Parkinson’s (10-27-2017)


A CRISPR Screen Identifies a Pathway Required for Paraquat-Induced Cell Death



Unified Parkinson’s Advocacy Council (7-24-2017)


Paraquat and Parkinson’s Disease: A Systemic Review Protocol According to the OHAT Approach for Hazard Identification (5-15-2017)

This Pesticide is Prohibited in Britain.  Why is it Still Being Exported? (12-20-2016)


Exposure to Pesticides or Solvents and Risk of Parkinson Disease (5-28-2013)


Traumatic Brain Injury, Paraquat Exposure, and Their Relationship to Parkinson Disease (11-13-2012)


Epidemiology and Etiology of Parkinson’s Disease: A Review of the Evidence



Parkinson’s Disease Risk from Ambient Exposure to Pesticides (4-20-2011)


Cancer Incidence Among Paraquat-Exposed Pesticide Applicators in the Agricultural Health Study (3-16-2011)

NIH Study Finds Two Pesticides Associated with Parkinson’s Disease (2-11-2011)


Rotenone, Paraquat, and Parkinson’s Disease (1-26-2011)


Paraquat and Parkinson’s Disease (1-22-2010)


Parkinson’s Disease and Residential Exposure to Maneb and Paraquat from Agricultural Applications in the Central Valley of California (3-6-2009)


Paraquat Exposure as an Etiological Factor of Parkinson’s Disease (7-3-2006)


Paraquat and Marijuana: Epidemiologic Risk Assessment (7-1983)

Paraquat Resources – ScienceDirect

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