What Is Paraquat Poisoning

Overview

Paraquat is a highly toxic chemical widely used as a herbicide for weed or grass control due to its rapid action and effectiveness. It was first introduced in 1961 and is the most commonly used herbicide in some parts of the world.¹ In the UK, there are stringent rules on the handling and use of paraquat.²

Paraquat poisoning can occur through accidental ingestion, often due to the consumption of contaminated food or water. It has also been associated with deliberate self-harm; hence, it is also a matter of concern in the mental health context.¹

Paraquat poisoning is exceptionally serious due to its rapid and potent toxicity, leading to severe damage to organs such as the lungs, liver, and kidneys. The absence of a specific antidote, along with its high mortality rate, underscores the urgent need for prevention, cautious handling, and immediate medical intervention.³

What products contain paraquat

Paraquat is commonly found in various herbicide products used in the agricultural and horticultural sectors. These products are designed for weed control and are used to manage unwanted vegetation in fields, gardens, and other outdoor spaces. Some of the well-known herbicide products containing paraquat that have been used in the UK include:

1. Gramoxone (also known as Gramoxone Max): This is one of the most recognised paraquat-containing herbicide products. It has been used for non-selective weed control in agricultural and non-crop areas.
2. Syngenta Touchdown: This is another paraquat-based herbicide product used for controlling a wide range of weeds. It has been employed in various agricultural and industrial settings.
3. Reglone: Reglone is a paraquat-based product commonly used for pre-harvest desiccation of crops like potatoes. It aids in the process of drying down plants before harvesting.
4. Fastac: Fastac is a paraquat-containing product that has been used for weed control in fields, orchards, and other agricultural environments.
5. Parazone: Parazone is a domestic weed killer containing paraquat, often used for controlling weeds in gardens, driveways, and paths.
6. Weedol Rootkill: This is another paraquat-based herbicide designed for garden use, primarily to target unwanted plants and weeds.

It's important to note that while these products may contain paraquat, the availability and use of specific formulations can change over time due to regulatory changes, advancements in agricultural practices, and evolving safety concerns. As such, individuals who use herbicides containing paraquat should always follow the manufacturer's instructions, wear appropriate protective gear, and adhere to regulations to ensure safe and responsible use.

Exposure to paraquat

The likely route of exposure is ingestion (swallowing). This mostly occurs from consuming contaminated food or beverages. Other sites are through the skin, especially after prolonged exposure to concentrated Paraquat or if the skin is not intact (skin that has sores, cuts or a nasty rash). At times, inhalation can occur, especially in people who mostly work around the chemical, leading to severe lung damage.⁴ 

How paraquat works

Paraquat poisoning is a fast process with a rapid onset of symptoms. The severity of poisoning depends on the route, duration of exposure and amount of paraquat an individual has been exposed to. It causes direct damage to the lining of the mouth, stomach or intestines once ingested. 

Paraquat harms the body by creating harmful molecules called "reactive oxygen species" and oxidative stress. This oxidative stress damages cell membranes, proteins, and DNA, particularly affecting tissues with high oxygen demand, such as the lungs, leading to breathing problems and other serious health issues. Additionally, paraquat accumulates in the lungs due to its strong affinity for lung tissue, leading to inflammation, fibrosis, and respiratory distress.⁵

Signs and symptoms of paraquat poisoning

Ingestion of small to medium amounts of paraquat may lead to the development of the following adverse health effects within several days to several weeks:

• Heart failure
• Kidney failure
• Liver failure
• Lung scarring/Fibrosis

Pain and swelling of the mouth and throat are associated with ingesting large amounts of paraquat. Other signs are mainly gastrointestinal (digestive tract) symptoms, such as nausea, vomiting, abdominal pain, and diarrhoea (which may become bloody).³

Severe gastrointestinal symptoms may result in dehydration, electrolyte abnormalities, and low blood pressure.

Ingestion of large amounts of paraquat can also lead to:^6,7

• Acute Kidney failure
• Confusion
• Coma
• Tachycardia (Fast heart rate)
• Injury to the heart
• Liver failure
• Lung scarring
• Muscle weakness
• Pulmonary oedema (fluid in the lungs)
• Respiratory failure, which can lead to death
• Seizures

Long-term health effects

If a person survives the toxic effects of paraquat poisoning, long-term lung damage (scarring) is highly likely. Other long-term effects may also occur, including kidney failure, heart failure, and oesophageal strictures (scarring of the swallowing tube that makes it hard for a person to swallow).⁸

Diagnosis

This involves a combination of medical history, physical exam and diagnostic tests. Healthcare professionals will assess potential exposure sources and perform tests such as blood and urine analysis to detect the presence of paraquat. Imaging studies such as X-rays and CT scans may also be conducted to evaluate organ damage.

Steps to take following exposure

In case of any exposure to liquid paraquat on your clothes or body, follow the following steps:

1. Remove your clothing

Remove clothing with liquid paraquat immediately. Cut off clothing that needs to be pulled over the head instead of pulling it off. When assisting others, be cautious to avoid contact with contaminated areas and swiftly remove their clothing.

2. Wash yourself

As quickly as possible, wash any liquid paraquat off your skin with large amounts of soap and water.

Remove any contact lenses and glasses if your eyes are burning or your vision is blurred. Rinse your eyes with running water for 10 – 15 minutes. For contact lenses, do not put them back on, but discard them along with the contaminated clothing. As for your glasses, wash them with water and soap, and you can put them back on after washing.

3. Dispose of your clothes

After washing, place clothing in a plastic bag, avoiding contact with contaminated areas. Use gloves or tools if necessary. Seal the bag and place it inside another plastic bag to prevent chemical exposure. Inform local health authorities about the disposal method and let them handle the clothing for safe disposal.

Treatment

Paraquat poisoning is often fatal. Initial therapy consists of eliminating the paraquat from the body (decontamination) and preventing further absorption for oral exposures by inducing vomiting or using activated charcoal or Fuller’s Earth if the ingestion was recent. The activated charcoal is either taken orally or through a nasogastric tube. This helps absorb the chemical and decrease the amount taken up by the body.⁹

Hemoperfusion can also be done to remove paraquat from blood through filtering.¹⁰

A ventilator should be used to support breathing, as should intravenous fluids (fluids given through a needle inserted straight into a vein), drugs to aid with breathing and increase low blood pressure, and maybe dialysis for kidney failure. It is best to avoid administering too much oxygen because it could make paraquat toxicity worse. There is no known treatment/antidote for paraquat toxicity.¹¹

Death from paraquat poisoning is highly likely if one ingests the chemical and does not seek medical attention. 

Protective measures when handling paraquat

• Avoid areas where you know paraquat or herbicides are used.
• Wash all produce thoroughly with clean water before consuming it.
• In areas known for paraquat usage, only bottled water and other pre-packaged beverages are allowed.
• Don't consume if you believe food or drink has been in contact with paraquat.
• If you work with paraquat, read all chemical labels carefully.
• Shower immediately after using the chemical

Research and development

Ongoing research on paraquat spans multiple fronts, including unravelling its toxic mechanisms, developing antidotes, understanding its impact on respiratory health, assessing environmental consequences, informing regulatory decisions, and promoting public awareness. This comprehensive effort seeks to comprehend paraquat's effects on human health and the environment, explore alternatives, and enhance safety measures in agricultural practices, with the ultimate goal of mitigating risks and fostering responsible usage.

Advancements in agricultural practices aimed at reducing paraquat exposure have gained momentum due to the herbicide's toxic nature. These innovations prioritise human and environmental safety while maintaining effective weed control.¹²

FAQs

Where can paraquat be found?

Paraquat is present in several herbicide products used in the UK for weed control in agriculture and horticulture. Notable products include Gramoxone, Syngenta Touchdown, Reglone, Fastac, Parazone, and Weedol Rootkill, each serving various purposes such as non-selective weed control, pre-harvest desiccation, and domestic garden use.

What happens in paraquat poisoning?

Initial symptoms include gastrointestinal distress, while its distinctive and devastating impact on the lungs causes respiratory distress and dry cough. The toxin's reach extends to the liver, kidneys, and heart, often resulting in systemic organ failure, ulcers, bleeding, and acute kidney injury. 

Can paraquat effects be reversed?

Paraquat poisoning has severe and irreversible effects on organs such as the lungs, liver, and kidneys. There is no specific antidote to fully reverse its toxic impacts. Treatment primarily involves providing supportive care, managing symptoms, and reducing further absorption of the chemical. Despite medical interventions, the damage caused by paraquat poisoning is challenging to completely reverse. Prevention and prompt medical attention remain crucial, as paraquat's high toxicity can lead to severe health complications.

Summary

Paraquat, a highly toxic herbicide, is widely used for weed control due to its rapid effectiveness. The poisoning can occur through ingestion, inhalation, or skin contact, and it poses risks both accidentally and deliberately. The toxic mechanism involves oxidative stress and damage to cell structures, particularly affecting organs like the lungs. Symptoms include gastrointestinal distress, organ failure, and lung scarring. Immediate medical intervention is crucial, as there's no known antidote. Ongoing research focuses on understanding its impact, developing antidotes, and fostering responsible usage.