Dioxins - the most poisonous substance known


On February 3 this year, a train carrying toxic chemicals derailed and caused a fire in Ohio, USA. Because the Norfolk Southern Railway Company, which owned the derailed train, conducted a "controlled release" of vinyl chloride carried by the train by burning it, and the burning of vinyl chloride produces dioxins, some experts called this disaster the "Ohio version." Chernobyl”. Dioxin is called "the most dangerous chemical in the world" and has "non-degradable" characteristics. People are worried that "it may cause global food problems" because Ohio is rich in corn, soybeans, oats and other food crops. It is one of the main sources of imported agricultural products for many countries.

A month later, the U.S. Environmental Protection Agency (EPA) said it had directed Norfolk Southern to test the wreckage of the derailed train for dioxin. At that time, an independent testing agency had discovered nine new toxic compounds containing dioxins around the site of the accident. Now, several months have passed since the accident, and the ghostly shadow of dioxin is still lingering.

Dioxins is a general term for a class of chemical substances. There are 210 chemical substances that have been discovered that can be classified as dioxin, 17 of which can cause great harm to the human body. "2, 3, 7, 8-4 Chlorinated dibenzo-p-dioxin (TCDD) is considered to be the most toxic substance known so far. Its biological toxicity is 130 times that of cyanide and 900 times that of arsenic. In 1997, the World Health Organization classified TCDD as a Category 1 carcinogen, that is, a "confirmed carcinogen."

In addition to being carcinogenic, dioxins also have irreversible "teratogenic and mutagenic" toxicity. Dioxins mainly affect the hormone secretion of the reproductive system and endocrine system, causing a sharp decrease in male sperm count, interruption of testicular development, permanent sexual dysfunction, and gender self-perception disorder. Dioxins can also cause uterine cancer, breast cancer, ovarian dysfunction and other problems in women. Some scientists pointed out that the long-term and chronic interference of dioxin on human hormones has never occurred in the history of human evolution. In many countries, infants and young children are the primary groups to prevent dioxin contamination, because dioxin is very good at seizing "timing" and can transmit toxicity during the mother's pregnancy and breastfeeding process. Infants and young children exposed to even "very trace amounts" of dioxins will suffer irreparable harm, because dioxins may cause permanent impairment of immunity, intelligence and motor ability.

In addition to being carcinogenic and teratogenic, dioxins are highly enriched in animals through the food chain. When the concentration reaches a certain value, their reproductive toxicity, immunotoxicity and endocrine toxicity will cause various diseases in the skin, internal organs and other parts of the body. disease. Therefore, dioxin has another nickname - the invincible poison. At the same time, dioxin is also non-degradable and will be deposited in the natural environment, causing great harm to soil and water sources. Human beings are at the top of the food chain and are the final "gathering place" for pollution, which means that they are not directly Dioxins that enter the human body will eventually enter the human body through the food chain.

Generally speaking, when toxic substances are diluted to a certain level, they will reach a safe level that is basically harmless to the human body. Dioxins are an "exception". According to the recommendations of the World Health Organization and the World Food and Agriculture Organization, it is safe for an adult weighing 60 kilograms to consume no more than 4,200 picograms of dioxins per month (1 picogram = 10-12 grams). The EU recommendation is 3600 pg. However, in life, this is an almost impossible "safe level" to achieve. Although trace amounts of ingestion will not immediately cause disease, dioxins are extremely stable and difficult to be excreted once ingested. Even if they are no longer ingested, their half-life in the human body is as long as 7 to 11 years. Therefore, dioxin is called the "poison of the century" by scientists.