Paraquat: A toxic chemical widely used as an herbicide (plant killer), primarily for weed and grass control. Paraquat is highly poisonous. It was first produced for commercial purposes in 1961.
The most likely route of exposure to paraquat leading to poisoning is ingestion (swallowing). Paraquat can be easily mixed with food, water, or other beverages. The form of paraquat marketed in the US has a blue dye to keep it from being confused with beverages such as coffee, a sharp odor to serve as a warning, and an added agent to cause vomiting if someone drinks it. Paraquat from outside the US may not have these safeguards added. Paraquat poisoning is also possible after skin exposure. Poisoning is more likely to occur if the skin exposure lasts for a long time, involves a concentrated version of paraquat, or occurs through skin that is not intact (skin that has sores, cuts, or a severe rash). If paraquat is inhaled, it could cause lung damage. In the past, some marijuana in the US has been found to contain paraquat.
The extent of poisoning caused by paraquat depends on the amount, route, and duration of exposure and the person’s condition of health at the time of the exposure. Paraquat causes direct damage when it comes into contact with the lining of the mouth, stomach, or intestines. After paraquat enters the body, it is distributed to all areas of the body. Toxic chemical reactions occur throughout many parts of the body, primarily the lungs, liver, and kidneys. The ingestion of a large amount of paraquat is likely to cause immediate pain and swelling of the mouth and throat. The next signs of illness following ingestion are gastrointestinal (digestive tract) symptoms, such as nausea, vomiting, abdominal pain, and diarrhea (which may become bloody). Severe gastrointestinal symptoms may result in dehydration (not enough fluids in the body), electrolyte abnormalities (not enough sodium and potassium in the body), and low blood pressure. Ingestion of small to medium amounts of paraquat within several days to several weeks later may lead to development of liver failure, kidney failure, heart failure, and lung scarring. In general, ingestion of large amounts of paraquat leads to the following signs/symptoms within a few hours to a few days:
Pulmonary edema (fluid in the lungs)
Lung scarring (evolves more quickly than when small to medium amounts have been ingested)
Injury to the heart
Fast heart rate (tachycardia)
Respiratory (breathing) failure, possibly leading to death.
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 esophageal strictures (scarring of the swallowing tube that makes it hard for a person to swallow). People with high-dose exposure to paraquat are not likely to survive.