On December 23, Tsinghua University’s official Weibo announced that Zhu Ling, a 1992 alumnus of the school, passed away on December 22. Zhu Ling was a chemistry student at Tsinghua University. He began to suffer from strange illnesses at the end of 1994, and was diagnosed with thallium poisoning on April 28, 1995. Subsequently, all parties were convinced that he had been poisoned, and the police had opened a case for investigation, but so far there has been no clear conclusion. Although the hospital vigorously treated and detoxified her, it still caused her to suffer from severe sequelae throughout her life. Some people say that Zhu Ling popularized thallium knowledge for people at the cost of almost his life.
Thallium is a naturally occurring element in the earth’s crust and exists mainly as a monovalent element. In seawater, locally strongly oxidized fresh water and soil, it mainly exists as trivalent oxides. Generally found in soil, it is easily soluble in water under acidic conditions. In the dissolved state, monovalent thallium is relatively stable, while trivalent thallium can precipitate out of water in the form of oxides or hydroxides.
Thallium and thallium oxides are toxic and can cause lesions in the central nervous system, gastrointestinal system, kidneys and other parts of the human body. Thallium poisoning can occur if a person drinks water contaminated with thallium or inhales dust containing thallium compounds.
Thallium is a chemical substance strictly controlled by the country, and people generally do not come into contact with it in daily life. Thallium poisoning is mostly caused by poisoning, and the onset of the disease is acute and severe. Because thallium salt is a colorless, odorless crystal and has no special taste when dissolved in water, it is difficult to detect, often leading to misdiagnosis. In China, incidents of thallium poisoning are not uncommon.
In December 2014, the media reported that a family of six in Linquan County, Fuyang City, Anhui Province suffered from thallium poisoning, and five of them were in serious condition. The client suspected that the leftovers were poisoned and said that this was not the first time he was poisoned. After being poisoned, the family involved suffered from body pain, hair loss and other symptoms.
In April 2016, Xiao Zhao, a 15-year-old boy living in Qujing City, Yunnan Province, secretly bought a few grams of thallium from the Internet to prepare for chemical experiments. But he accidentally got a little bit on his hand, and then developed symptoms of poisoning.
In February 2022, media reported that a 1-year-old girl in Fuzhou, Fujian suffered from unexplained thallium poisoning.
Thallium is more toxic to mammals than metal elements such as lead and mercury, and is comparable to arsenic. Its minimum lethal dose for adults is 12 mg/kg body weight, and for children it is 8.8 to 15 mg/kg body weight. Symptoms after poisoning include numbness or pain in the lower limbs, low back pain, hair loss, headache, mental restlessness, muscle pain, trembling hands and feet, and unsteady walking.
According to “Baidu Encyclopedia”, thallium is a widely used industrial raw material. Thallium-containing alloys mostly have special properties and are raw materials for the production of corrosion-resistant containers, low-temperature thermometers, and superconducting materials. Some thallium compounds are sensitive to infrared rays and are important raw materials for the optoelectronics industry. Thallium compounds can also be used to prepare insecticides, hair loss agents (thallium acetate), etc. In addition, the raw materials for the production of firecrackers (firecrackers) often contain high amounts of thallium, and its by-product sodium chloride (non-edible salt) is also contaminated. When the human body consumes this non-edible salt, it can cause poisoning. Thallium poisoning is mostly caused by the oral administration of thallium salts or the external application of thallium-containing ointment to treat tinea pedis (which is no longer used in my country). A few cases are caused by the mistaken intake of rodenticides, insecticides, and mosquito killers containing thallium.
Can we be exposed to thallium in our lives? How to prevent thallium poisoning in life?
1. Avoid contact with thallium. The general population has relatively few opportunities to be exposed to thallium in daily life, but some workers on the front lines of production need to wear masks, gloves and other protective tools when exposed to thallium. Cases have shown that acute thallium poisoning may occur after 2 hours of exposure to thallium-containing dust.
2. Avoid eating contaminated vegetables, etc. When growing edible vegetables in some mining areas, attention should be paid to the accumulation of harmful substances. Due to the collection and processing of thallium-containing ores (mercury ores), the thallium-containing slag is covered with soil to create land for growing vegetables. In drought years, groundwater penetrates the slag layer and is absorbed by vegetables with long root systems such as cabbage. People eat it. A large amount of vegetables containing thallium can cause thallium poisoning.
3. Avoid accidentally ingesting thallium. There are also cases in life where thallium salts are mistakenly taken as table salt. Therefore, if you are exposed to thallium salts in your life and work, do not store them randomly or mix them. Don’t eat salt that is not exclusively sold by the country.