OVERVIEW

What is paraquat?

Paraquat is a herbicide effective against various weeds. It is rapidly absorbed by plant green tissues, causing them to wither and die. Due to its relatively low cost, it is widely used in developing countries.

How much paraquat ingestion is fatal?

Ingesting 30 milliliters (one or two mouthfuls) of paraquat at 20–24% concentration is typically fatal. Even consuming just 10 milliliters can lead to severe symptoms and consequences.

SYMPTOMS

What are the symptoms of paraquat poisoning?

• Symptoms of the mouth and digestive tract: Most common, presenting as oral pain, difficulty swallowing, nausea, vomiting, abdominal pain, etc.

• Skin symptoms: About half of patients experience a burning sensation on the skin within one to two days of poisoning.

• Respiratory symptoms: Manifested as difficulty breathing and rapid breathing. The appearance of respiratory symptoms usually indicates severe poisoning and a higher risk of death.

When do symptoms of paraquat poisoning typically appear?

Symptoms usually appear 6 to 12 hours after ingestion.

Which organs are most susceptible to damage from paraquat?

The organs most vulnerable to damage are typically those with abundant blood flow, such as the lungs, heart, kidneys, and liver. Due to the presence of a protective membrane called the "blood-brain barrier" in the human brain, paraquat has difficulty entering the brain's bloodstream, so brain tissue is less directly affected.

How is paraquat eliminated from the body?

Paraquat can be excreted from the body through the kidneys. However, since paraquat also damages the kidneys, it can impair their ability to eliminate the toxin. If the patient does not die within 24 hours, it may take over 100 hours for the kidneys to clear the poison.

Are the outcomes of paraquat poisoning always the same?

No.

Just as people have varying resistance to diseases, individuals differ in their ability to detoxify paraquat. Additionally, outcomes vary depending on factors such as the ingested dose, the time elapsed since poisoning, the treatment measures taken, and the patient's underlying health condition.

CAUSES

What is paraquat poisoning?

After intentional ingestion or accidental consumption of paraquat, it first causes corrosive burns to the oropharynx and gastrointestinal tract. Once absorbed into the bloodstream through the digestive system, paraquat travels to various organs, exerting toxic effects on cells. This leads to failure of multiple vital organs such as the heart, brain, liver, and lungs, ultimately resulting in death.

DIAGNOSIS

What tests are performed for paraquat poisoning patients?

Upon admission, doctors will first conduct blood tests, which should be repeated every 6–12 hours within the first 48 hours. The frequency of subsequent tests depends on the severity of the condition.

Tests typically include the following:

• Blood and urine paraquat concentration: Confirms the diagnosis of paraquat poisoning and helps predict the patient's prognosis.

• Electrolytes: Due to nausea, vomiting, diarrhea, acute renal failure, and multi-organ dysfunction, electrolyte imbalances are common. Testing is essential to guide clinical treatment by replenishing deficiencies.

• Kidney function: Assesses the presence of acute renal failure, which is critical for predicting outcomes. Serum creatinine is a key indicator; a slow rise suggests a higher survival rate.

• Blood gas analysis: Initial severe vomiting may cause alkalosis due to gastric acid loss, followed by acidosis from respiratory failure (CO₂ retention) or diarrhea (alkaline intestinal fluid loss). Severe acid-base imbalances can be fatal and require close monitoring.

• Blood lactate levels: Lactate is an indicator of acidosis, reflecting systemic circulatory and organ perfusion impairment, aiding in clinical assessment and treatment planning.

• Chest X-ray: Evaluates lung damage, hyperventilation, or pulmonary edema.

• Other toxic substance tests: Paraquat poisoning rarely causes altered consciousness. If present, testing for other toxins is necessary.

What conditions should paraquat poisoning be differentiated from?

If the patient is unaware or unwilling to disclose the ingested poison, paraquat poisoning must be distinguished from other conditions.

Typically, simultaneous oropharyngeal corrosion and systemic toxicity strongly suggest paraquat poisoning, as other herbicides rarely cause mucosal damage, and corrosive poisons seldom induce systemic effects like renal failure. The definitive method is measuring paraquat levels in blood and urine.

TREATMENT

Which department should be consulted for paraquat poisoning?

Paraquat poisoning is usually fatal. If ingestion is suspected, immediate emergency treatment is required! Patients with multiple organ failure need treatment in the intensive care unit (ICU) or emergency ICU.

What should witnesses do before sending a paraquat poisoning patient to the hospital?

If someone is found to have ingested poison, witnesses should:

• Immediately stop further contact between the poisoned person and the poison.
• Help the poisoned person eliminate unabsorbed toxins from the body. For those who have ingested paraquat, induce vomiting by stimulating the back of the throat or the base of the tongue with chopsticks or a tongue depressor. Take personal protective measures and promptly clean areas contaminated by paraquat.
• When sending the patient to the hospital, remember to bring the medication bottle or label.

How is paraquat poisoning treated?

• If medical attention is sought promptly, gastrointestinal decontamination (vomiting induction, gastric lavage) should be performed immediately. After lavage, administer activated charcoal or bentonite via a gastric tube to prevent further absorption. Hemoperfusion, hemodialysis, or hemofiltration can also accelerate the elimination of absorbed paraquat.
• If the patient arrives too late and shows life-threatening signs, immediate resuscitation and emergency treatment are required.
• Wash skin exposed to paraquat immediately.

Symptomatic treatment is also provided based on the patient's specific condition.

What is hemoperfusion in the treatment of paraquat poisoning?

Hemoperfusion involves drawing blood from the body, passing it through a device containing solid adsorbents to remove toxins, and then returning the blood to the body. It is an effective and rapid detoxification method.

If a patient seeks medical attention within 4 hours of ingesting paraquat, hemoperfusion may be performed.

What are hemodialysis and hemofiltration in the treatment of paraquat poisoning?

Hemodialysis or hemofiltration involves passing the patient's blood through a dialyzer, using a semipermeable membrane to separate toxins from the blood based on solute concentration differences.

If hemoperfusion is unavailable, hemodialysis or hemofiltration can be performed for patients who ingest paraquat. Patients with acute kidney injury should also undergo dialysis or filtration to allow kidney recovery.

How is oral mucosa and skin damage from paraquat poisoning treated?

Rinse affected skin and mucous membranes with plenty of water. For severe skin damage, dermatological or cosmetic treatment may be required after stabilizing the patient.

Can paraquat poisoning be cured?

Paraquat poisoning has an extremely high mortality rate. The outcome can usually be predicted within one or two days of ingestion.

Is follow-up treatment needed after surviving paraquat poisoning?

• Kidney damage may persist for weeks, and some patients may require dialysis until renal function recovers.
• Severe lung damage may necessitate a lung transplant.

When should aggressive treatment be abandoned in favor of palliative care for paraquat poisoning?

If multiple organ failure, respiratory distress, hypoxemia, shock, severe acidosis, or rapid kidney function decline occurs, the prognosis is usually poor. Families may consider switching to palliative care to alleviate suffering.

Generally, ingesting more than 30 mL of 20–24% paraquat solution is almost always fatal.

What is palliative care for paraquat poisoning?

Palliative care involves relieving suffering without aggressive medical interventions or hastening death. For patients with severe paraquat poisoning and no chance of survival, providing pain relief (e.g., morphine, fentanyl) allows a more peaceful passing.

Are there special considerations for paraquat poisoning in children?

Unlike adults, children usually ingest paraquat accidentally rather than intentionally. Since it is difficult to determine the ingested amount, prompt medical attention is crucial.

Fortunately, paraquat is not sweet, so children often vomit it out. If a child shows only oral corrosion without systemic symptoms, the outcome may be favorable.

DIET & LIFESTYLE

What is the current usage status of the herbicide paraquat in China?

Due to its extremely high fatality rate after poisoning, most countries worldwide have implemented strict controls or bans on paraquat.

Since July 1, 2014, China has revoked the registration and production licenses for paraquat aqueous solutions, halted domestic production, while retaining export registrations for manufacturers supplying overseas markets. Domestic sales and use of paraquat aqueous solutions were completely banned from July 1, 2016.

However, previously sold paraquat products may still remain in users' possession, leading to occasional cases of paraquat poisoning.

PREVENTION

Can paraquat poisoning be prevented at the manufacturer level to avoid intentional ingestion or accidental consumption?

Manufacturers add emetics, odorants, coloring agents, and cellulose-based formulations that slow gastrointestinal absorption to paraquat. These measures aim to reduce accidental ingestion, induce vomiting after consumption, or delay toxin absorption.

How to avoid paraquat poisoning in agricultural production?

• First, avoid selecting or storing paraquat.

• If accidentally exposed, paraquat is minimally absorbed through the skin. Spray contact may only cause localized skin damage and is not fatal.

• However, paraquat is rapidly absorbed through the gastrointestinal tract, so accidental ingestion must be strictly avoided.

How to prevent paraquat poisoning?

Although paraquat sales are banned in China, some regions may still use it. Users should label containers clearly, store them securely, and prevent accidental ingestion. Specific measures include:

• Centralized management, strictly prohibiting private storage;

• Attaching warning labels to containers;

• Wearing long sleeves, pants, and protective goggles during use, avoiding bare skin exposure and spraying against the wind;

• For those with suicidal thoughts, cherish life, seek help, and share distress—suicide may prove unnecessary.