Was it "drunk" so much that it stopped production? Why is this pesticide still being used despite repeated bans?

Audit expert: Wu Xinsheng

Deputy Chief Physician, Department of Gastroenterology

Paraquat is an efficient, clean and cheap herbicide that has been on the market in China for more than 30 years. It has gone from being highly praised to being a deadly killer. What has happened to paraquat that has turned it from a powerful weed killer into a deadly killer?

What is paraquat?

Paraquat , whose chemical name is 1,1'-dimethyl-4,4'-bipyridinium chloride, was first synthesized in 1882. The herbicide with it as the active ingredient was registered and produced by the British company Syngenta (ICI) in 1962.

Source: China Agriculture Network

**As a herbicide, paraquat has many excellent properties. **First, its excellent weed control effect and inactivation in soil have enabled the rapid development of no-till farming technology, effectively reducing soil nutrient loss and erosion, and improving land utilization. Secondly, paraquat can also be used as a ripening and withering agent. Spraying it when crops are about to be harvested can speed up crop maturity, while quickly dehydrating and drying straw to improve the efficiency of mechanical harvesting. In addition, its low price can greatly reduce the cost of manual weeding, making the originally time-consuming and labor-intensive weeding work easy and labor-saving.

Source: unsplash

These excellent characteristics have established paraquat's status as the king among herbicides, and once it was launched, it was quickly promoted and used, becoming the world's second largest herbicide. In the 1980s, my country first introduced paraquat, and cracked the production technology of paraquat in 2004, and began mass production. In 2011, the output reached 80% of the world's total output.

Why is paraquat still used despite repeated bans?

Paraquat is best known for its strong toxicity. A 20% concentration of paraquat aqueous solution only requires one bottle cap (about 5-15 ml)** to kill an adult. **Since paraquat was introduced into China, people have attempted suicide by taking paraquat almost every year. After China's breakthrough in the technology of synthesizing paraquat, the number of people has increased significantly, but very few people can be saved. In desperation, the state issued policies to ban the sale and use of paraquat aqueous solution and paraquat soluble gel in the country in 2016 and 2020 respectively. Paraquat has thus become the first pesticide in China's agricultural history to be stopped from production and sales after being drunk by someone, but it has not disappeared.

Girl poisoned by paraquat Source｜Hebei TV Farmers Channel Weibo

The reason why paraquat is repeatedly banned is that its excellent properties have brought it a huge market. Under the "temptation" of demand, some unscrupulous merchants take risks and still sell paraquat in secret. Of course, they can't print the three big words "Paraquat" on the packaging of their products openly, so they can only do the trick of selling dog meat under the guise of sheep. In the results of the 2021 pesticide supervision and random inspection by the General Office of the Ministry of Agriculture and Rural Affairs, the "Diquat" pesticides of four manufacturers were detected to have paraquat as the active ingredient. Second, there are still some paraquats in rural areas that have not been handed in in time and have been piled up, which also created this phenomenon.

Symptoms of paraquat poisoning

Paraquat is so toxic that it can cause poisoning whether it is taken orally or exposed to large amounts for a long time. The symptoms of the two routes are different, but both are very painful. This article mainly introduces the symptoms of oral administration.

There are no obvious symptoms after taking paraquat (unless the dose is too large). If you go to the hospital in time and induce vomiting after gastric lavage, you may feel that it is no big deal. However, the subsequent developments will not make them feel so relieved.

In the early stages, sore throat and oral ulcers will make it very difficult for patients to speak and eat, and they can only rely on liquid food to take in nutrition. At the same time, toxins will flow through the blood and cause damage to other organs.

In the late stage, patients will suffer greatly because the hallmark symptom of paraquat poisoning - pulmonary fibrosis - is occurring. Patients will experience hypoxia symptoms such as chest tightness and palpitations, accompanied by acute respiratory distress syndrome or acute lung injury.

Six days after paraquat poisoning, ground-glass high-density shadows appeared in the lungs and pleural effusion increased. Source: Baidu Encyclopedia

The most terrifying thing is that paraquat does not cause severe damage to the human nervous system. The patient will maintain a relatively clear consciousness and slowly feel the deterioration of his or her body, and will eventually suffocate to death due to respiratory failure.

Diagnosis and treatment of paraquat

Paraquat is so terrible. Do we have any means of treating patients who have been poisoned?

The answer is yes. Regarding poisoning, I believe everyone knows the saying that "talking about toxicity without mentioning the dosage is just a hooliganism", and this saying is valid even for highly toxic drugs like paraquat. The most authoritative institution for the treatment of paraquat poisoning in China, Qilu Hospital of Shandong University, joined forces with many experts in this field in China and proposed the "Qilu Plan" for the treatment of paraquat poisoning in 2014. The plan proposed diagnostic grading standards and standardized treatment processes for paraquat poisoning.

According to the different ingested doses, paraquat poisoning is divided into three levels:

For paraquat poisoning, the first thing to do is to prevent the toxin from being further absorbed, which is the common vomiting and gastric lavage . Then you need to use diuretics, blood purification and catharsis to accelerate the excretion of the poison.

Next comes drug treatment. Glucocorticoids and immunosuppressants can effectively reduce the inflammatory response caused by paraquat's corrosion of the human body. The former can also inhibit lung fibrosis in the later stages of poisoning. Pirfenidone can be used as an anti-fibrotic drug to increase the patient's chances of survival. Antioxidant drugs should also be used to avoid oxidative overreactions, and various anti-infective drugs can prevent the human body from being invaded by various viruses and bacteria when immunosuppressants weaken the body's immune response.

Source of the chemical formula of glucocorticoids | Baidu Encyclopedia

Other treatments include oxygen therapy, ECMO, lung transplantation , etc. Lung transplantation is a treatment option for late-stage pulmonary fibrosis, but it is almost impossible to promote due to the scarcity of lung sources, high surgical fees, and the need to take immunosuppressants for life.

ECMO treatment source | Tencent News Client

After standardized treatment, most mildly poisoned patients can fully recover, more than half of moderately poisoned patients can recover, and only a few of severely poisoned patients can survive, with serious sequelae. The hospital will follow up on discharged patients to confirm their recovery.

Our understanding of paraquat makes us realize that life is precious and fragile, and we should never be reckless or impulsive when dealing with life.