Paraquat — What Is It?

Paraquat, which is also sold under the brand name Gramoxone, is one of the most widely-used herbicides (also known as weed killers) in the world. It is extremely toxic to humans and animals and can lead to death quickly if it is ingested in even small amounts.

Paraquat (Gramoxone) is chiefly used as a weed-killer and to limit the growth of unwanted grasses. It is often used in tandem with other weed killers, particularly Roundup (glyphosate), which is a known carcinogen and is extremely toxic itself.

Roundup (glyphosate) — the world’s top-selling herbicide — is used primarily on industrial monoculture food crops such as grain and produce that have been genetically modified to survive the application of glyphosate. Since glyphosate has been used for so long, several weeds and grasses have developed resistance to it. Additionally, growing safety concerns and lawsuits surrounding Roundup in the US have contributed to Paraquat and other herbicides seeing a recent surge in use as complementary or replacement weed killers.

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Is Paraquat (Gramoxone) Safe?

In short, Paraquat is extremely dangerous when not handled with extreme care and poses serious health risks no matter how it is handled.

The sale of Paraquat in the US is limited to those who are licenced to handle the chemical, which has reduced the incidence of acute Paraquat poisoning among Americans. However, it has been linked to Parkinson’s Disease and is still one of the top causes of fatal poisonings around the world — especially in developing countries — due to the fact that ingesting even small amounts of the chemical can quickly lead to death.

The History of Paraquat Use Around the World

Paraquat was originally developed in the late nineteenth century, but it was not discovered to be a potent herbicide until 1955, when Imperial Chemical Industries, a United Kingdom firm, recognized its potential use on crops and began to market and sell it under the name Gramoxone. It was on the global market by 1962 and has become one of the top selling herbicides worldwide.

Paraquat is, however, currently banned in 32 countries. Switzerland was one of the first nations to ban the use of the popular herbicide in 1989, though the Swiss firm Syngenta continues to manufacture Paraquat for export.

In 2004, the European Union approved Paraquat for use on crops, but Sweden led a group of countries that included Denmark, Finland, and Austria in appealing that approval. They succeeded in 2007, basing their appeal on the known links between Paraquat and Parkinson’s Disease, and the chemical has been banned in the EU since 2013. The United Kingdom has also banned Paraquat, though it is still manufactured there for export.

South Korea, citing the use of herbicides in suicide, banned Paraquat in 2011 and has since seen a 46% drop in suicides by self-poisoning. Despite the fact that Paraquat is manufactured in China, that country also began a gradual phaseout of Paraquat in 2012 citing the danger it poses to humans. Currently, all Paraquat produced in China is sold for export.

The United States is another story. While a license to handle Paraquat is required of anyone seeking to purchase it, Paraquat is still widely available to the industrial agriculture sector and its use has been steadily increasing in recent years. In fact, Paraquat use on US crops doubled from 2013 to 2017 and sales have reached over ten million pounds of the herbicide per year, likely due to the growing resistance of crops to Roundup (glyphosate) and a growing number of lawsuits centered on Roundup’s links to several cancers.

Paraquat is much easier to obtain in some developing countries in Latin America, Asia, and the South Pacific, and has come under fire for its role in suicides and murders since it can be fatal in very small doses. Because farming supplies are less regulated in these countries, Paraquat can often be purchased by anyone who chooses to.

There is a growing push for an international ban on Paraquat (Gramoxone) due to the known dangers it poses, and several countries have urged that it be placed on the list of banned chemicals under the Rotterdam Convention, a multilateral agreement on the import, export, trade, manufacture, and use of hazardous chemicals.

However, that effort has been blocked by a small group of developing countries that rely on access to cheap Paraquat as an herbicide. Paraquat manufacturers have also used those countries as a public relations shield and have quietly financially backed their efforts to block a global ban under the Rotterdam Convention.

The US Environmental Protection Agency (EPA) and Paraquat

Though Paraquat is still commonly used in industrial agriculture in the US, the Environmental Protection Agency (EPA) announced in 2016 that they would be revisiting the effects of Paraquat on humans and the environment, citing growing evidence of the connection between Paraquat and Parkinson’s Disease.

In late 2020, the EPA announced a Proposed Interim Decision under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) on the use of Paraquat and sought public input on new, stricter proposed safety measures beyond designating the weed killer a Restricted Use Product (RUP).

The new measures include labeling changes, aerial spraying restrictions, and quantity limits for certain crops, among other changes designed to reduce the ecological and health risks associated with Paraquat use on crops. The public comment period came to a close in December of 2020 and an Interim Decision is expected to be released shortly on the proposed new risk mitigation measures.

Paraquat’s Mechanism of Action on Plants and the Human Body

Paraquat belongs to the non-selective contact class of herbicides. Non-selective herbicides contrast with selective herbicides in that they are engineered to kill most plants they come into contact with, rather than a particular plant or group of plants.

Paraquat is popular — especially in no-till farming — for its ability to eliminate a broad range of grasses and broad-leaved weeds and because it works quickly, becomes resistant to being rinsed away by rain within minutes of application, and is partially deactivated by contact with soil.

Paraquat disrupts photosynthesis — the process by which plants convert solar energy into chemical energy that allows the plant to absorb nutrients from carbon dioxide and water — by acting as an oxidizing agent that interferes with electron transfer. Electron transfer is an essential process for all life forms, however, not just plants.

The EPA has identified four toxicity levels for chemicals including herbicides. Inhalation of Paraquat by agricultural workers poses the greatest risk of accidental acute poisoning, leading the EPA to place Paraquat inhalation in Toxicity Category I, the highest level in their ranking system. Because the alveolar epithelial cells of the lung — essential to the absorption of oxygen into the bloodstream — concentrate Paraquat, it is particularly dangerous when inhaled.

When ingested orally, Paraquat has been placed in Toxicity Category II (high toxicity) by the EPA. Even in small amounts, Paraquat can lead to severe health consequences when ingested orally, including multiple forms of organ failure and even death. These effects can occur within hours, days, or weeks of ingesting Paraquat, depending on the amount ingested.

Paraquat causes severe eye irritation, placing ocular exposure to the herbicide in Toxicity Category III (moderately toxic) along with dermal exposure; skin contact with Paraquat can cause irritation in small amounts, though long-term or high-quantity skin exposure can cause acute Paraquat poisoning, which can lead to organ damage and even death.

Paraquat Poisoning: Symptoms and Outcomes

Paraquat has no antidote and is extremely toxic. Ingesting even small quantities can lead to organ failure within a matter of days and poses the risk of death for up to thirty days after it has been ingested. Exposure to larger quantities is almost certain to lead to death, while chronic exposure — such as in the case of agricultural workers or those who live near areas in which Paraquat is used — can cause damage to the lungs, kidneys, heart, esophagus, and eyes.

The most common vector for Paraquat poisoning is swallowing, and symptoms arise quickly. Whether the chemical is inhaled or ingested, the most immediate symptom is swelling and pain in the mouth and throat as Paraquat causes irritation almost immediately on contact with skin and other tissues.

Other symptoms of Paraquat poisoning that are likely to arise quickly include:

  • Nausea
  • Vomiting
  • Pain in the abdomen
  • Diarrhea
  • Difficulty breathing
  • Nosebleeds

Within days or weeks of ingesting small quantities of Paraquat, patients face the danger of scarring of the lungs, respiratory failure, heart failure, liver failure, and kidney failure.

When larger amounts of Paraquat are ingested, severe symptoms can develop within hours to days, including:

  • Muscle weakness
  • Mental confusion
  • Seizures
  • Increased heart rate
  • Difficulty breathing
  • Respiratory failure
  • Coma
  • Kidney failure
  • Liver failure
  • Pulmonary edema
  • Death

The Use of Paraquat in Suicides and Murders

Though the dangers of Paraquat in the industrial food production sector have played a large role in national bans on the chemical in China, Europe, and elsewhere, more sinister uses for the herbicide have also factored into those bans.

Paraquat has been used in several murders, and it is one of the world’s most widely-used agents of suicide, unfortunately. As many as 30% of the world’s suicides are carried out using herbicides including Paraquat; in fact, over 90% of fatal Paraquat poisonings worldwide have been deemed suicides, chiefly in developing countries where the chemical faces looser regulations and may be readily and cheaply available to anyone who wishes to purchase it.

In a particularly gruesome example, it has been found that from 1979 to 2001, up to 70% of those who committed suicide in the island nation of Samoa did so using Paraquat. In the Caribbean, Trinidad and Tobago reports that in the late 1990s, more than 75% of suicides in the country involved Paraquat, almost always while the person committing suicide was under the influence of alcohol. Because Paraquat is so cheap and easy to access in these countries, it is no surprise that it has been a chief factor in so many intentional and accidental suicides.

Illegal storage of Paraquat in improper containers such as beverage cans and bottles, a common practice in the developing world, has led to a significant number of accidental deaths when the unwitting victim picks up a can or bottle they believe contains soda or beer and ends up with a mouthful of a highly toxic chemical that — even if it is immediately spat out — can still lead to death for up to 30 days.

Because it can be disguised in food and drinks and because as little as two teaspoons of Paraquat can be fatal, it is no surprise that it has been used in murders. In 1981, a British woman used the chemical to murder her husband, for example. A few years later in Japan, in 1985, a dozen people died in the infamous “Paraquat murders” after drinking beverages left in or near the vending machines found commonly in public spaces in the country. The perpetrators of those murders have never been found.

Paraquat Linked to Parkinson’s Disease

Several important studies have demonstrated a link between Paraquat exposure — particularly among agricultural workers and those who lived in close proximity to areas in which Paraquat was routinely spayed — and an increase in the incidence of Parkinson’s Disease.

Parkinson’s disease — a progressive disorder of the nervous system that negatively affects motor control — is incurable. The symptoms begin slowly, often with tremors or stiffness in the extremities, and accelerate until facial movements, speech, and overall motor coordination are impacted to the extent that they can lead to permanent disability, loss of quality of life, and eventually death.

A 2011 study carried out by the National Institutes of Health in the US determined that there was a link between Paraquat exposure and an increased incidence of Parkinson’s Disease among farm workers. One of the researchers for that study indicated that Paraquat has the capacity to harm the structure of cells it comes into contact with, and that such cellular damage would make those exposed to the chemical more likely to develop the disease.

Another 2012 study entitled the Genetic Modification of the Association of Paraquat and Parkinson’s Disease similarly demonstrated that a particular genetic variation made some populations up to eleven times more likely to develop Parkinson’s after exposure to Paraquat. A further study, published in 2016 in the journal Nature Chemical Biology, noted that Paraquat’s mechanism of action — inducing cell death via oxidative stress — was also a contributing factor to a more than doubling of the chance of developing Parkinson’s Disease among those exposed to Paraquat.

Paraquat and Other Herbicides Implicated in Parkinson’s Disease Lawsuit

An ongoing lawsuit filed in St. Clair County, Illinois was filed in 2017 on behalf of several agricultural workers who had developed Parkinson’s Disease after being exposed to Paraquat. Though the case was originally filed against Paraquat manufacturers Growmark and Syngenta, Chevron Chemical was later added to the suit as a co-defendant for their role in the distribution of the chemical.

Plaintiffs in the case allege that these firms hid the longer term health risks associated with Paraquat and other herbicides and that they were unaware of those risks until the 2011 study and subsequent studies showing that Paraquat could cause Parkinson’s Disease came to light.

If you or a loved one have been exposed to Paraquat and have developed early symptoms of or received a diagnosis of Parkinson’s Disease, you could be qualified to participate in the ongoing lawsuit against Syngenta, Chevron Chemical, and Growmark.

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    1) Were you or a loved one exposed to the herbicide Paraquat®? (Gramoxone®, Firestorm®, Helmquat®, or Parazone®)

    2) Approximately how often was Paraquat used?

    3) Were you or your loved one diagnosed with Parkinson's disease after being exposed to Paraquat®?

    4) Age at time of diagnosis?

    5) Year of diagnosis