Can paraquat cause pulmonary fibrosis

Some people may accidentally ingest paraquat. In fact, the toxicity of this pesticide is quite strong. There is no very good way to cure this disease. It may endanger people's lives. But the most important thing is that there will be a latent period after this situation occurs. During that period, the patient will not feel very serious symptoms. Only after the incubation period is over will the patient develop related conditions of pulmonary fibrosis.

Toxicology

Paraquat is also known as paraquat and chlorpyrifos, and is called paraquat in Taiwan Province of my country. This product has two types: dichloride and dimethyl sulfate. The former is code-named PP148 and the latter is code-named PP910. Chemically, it belongs to bipyridine heterocyclic compounds, and its chemical names are 1,1-dimethyl-4,4-bipyridine dichloride and dimethyl sulfate.

Animal experiments showed that it is moderately toxic, with the oral LD50 of dichloride and dimethyl sulfate salt being 155-203 mg/kg and 320 mg/kg respectively in rats. However, it is highly toxic to humans, with the estimated lethal dose for adults being about 5-15 ml or 40 mg/kg of a 20% aqueous solution. It is the herbicide with the highest mortality rate in acute poisoning among humans. Hundreds of deaths have been reported abroad, most of which were caused by accidental oral ingestion. Among them, all 49 cases who accidentally ingested more than 30 ml of 20% aqueous solution died. There have been many reports of acute poisoning cases in China, and those who accidentally ingested more than 30 ml of 20% aqueous solution orally have all died. Paraquat can be absorbed through intact skin, respiratory tract and digestive tract, but the absorption is not complete. After absorption, it is distributed to tissues and organs throughout the body with the blood, but the content in the lungs is very high, often ten to dozens of times greater than the content in the blood. It is rarely degraded in the body and is often excreted in its intact original form with feces and urine. A small amount can be excreted through breast milk. About 30% of oral exposure is excreted with feces. The absorption and excretion rates are both fast. When dogs were given 14C-methyl paraquat chloride orally or intravenously, the plasma concentration was highest 90 minutes after poisoning, and 50%-70% was excreted through the kidneys within 24 hours; while those injected intravenously were excreted through the kidneys within 6 hours, 80%-90% was excreted within 24 hours. Paraquat is irritating and corrosive to the skin and mucous membranes. Systemic poisoning can cause multi-system damage, especially serious lung damage, which can cause pulmonary congestion, hemorrhage, edema, hyaline membrane formation and degeneration, hyperplasia, fibrosis and other changes. In addition, it can cause liver and kidney damage and affect the circulatory, nervous, blood, gastrointestinal tract, bladder and other systems and organs. The toxic mechanism has not yet been elucidated. Most scholars believe that paraquat is an electron receptor that can be actively transported by type I and type II lung cells and taken up into the cells, acting on the redox reaction of the cells. Activation into oxygen free radicals in the cells is the basis of the toxic effect. The excessive superoxide anion free radicals (O=) and hydrogen peroxide (H2O2) formed can cause lipid peroxidation of cell membranes in the lungs, liver and many other tissues and organs, thereby causing damage to multiple system tissues and organs.

Signs of systemic poisoning affect multiple organ systems. Except for pulmonary edema and bleeding that occur quickly after accidental oral ingestion of large amounts, most symptoms develop gradually. Necrosis of the lungs, kidneys, liver, heart, and adrenal glands will occur within about 1-3 days, and fever may be present during the course of the disease. 1. Digestive system: Nausea, vomiting, abdominal pain, diarrhea and bloody stools appear in the early stage. After a few days (about 3-7 days), jaundice, abnormal liver function and other liver damage symptoms appear, and even liver necrosis may occur. A case of oral poisoning death from acute liver necrosis was reported in Dalian, China. 2. Urinary system: Symptoms of bladder irritation such as frequent urination, urgency, and pain when urinating, abnormal urine test results, changes in urine volume, and even acute renal failure may occur, which usually occur 2-3 days after poisoning. 3. Lung damage: more prominent, with pathological histological changes similar to oxygen poisoning. Clinical findings generally include the following three types of signs, but some cases have been cured without lung damage.