Carcinogenic.
Has reproductive toxicity and endocrine toxicity.
Immunosuppressive effects
Basic information:
Dioxin, 1,4-dioxane, is a monocyclic organic compound . It is a by-product that is not useful in industry. Generally speaking, the term "dioxin" in a broad sense refers to derivative compounds containing the aforementioned structure, such as tetrachlorodiphenylcyclodioxin, which is often used in animal experiments. (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Dioxins and their derivative compounds have different toxicities. In addition, because these compounds are fat-soluble, they will accumulate in animal fatty tissues and certain parts of plants.
Dioxins include 210 compounds. These substances are very stable, have a high melting point, are extremely difficult to dissolve in water, and can be dissolved in most organic solvents. They are colorless and odorless fat-soluble substances, so they are very It easily accumulates in organisms and is seriously harmful to the human body. ?
Substance introduction:
Dioxin, also known as dioxin (qǐ), is a colorless, odorless, severely toxic fat-soluble substance. One oxygen atom connected to two benzene rings substituted by chlorine atoms is polychlorinated dibenzofurans (PCDFs). Each benzene ring can be substituted with 1 to 4 chlorine atoms, thereby forming numerous isomers, including 75 isomers for PCDDs and 135 isomers for PCDFs.
Natural microorganisms and hydrolysis have little impact on the molecular structure of dioxin. Therefore, it is difficult to naturally degrade and eliminate dioxins in the environment. It includes 210 compounds. It is very toxic, 900 times more toxic than arsenic. It is known as the "poison of the century". One ten thousandth or even one hundred millionth of a gram of dioxin will cause serious harm to health. In addition to its carcinogenic toxicity, dioxin also has reproductive toxicity and genetic toxicity, directly endangering the health and life of future generations. Therefore, dioxin pollution is a major issue related to human survival and must be strictly controlled. The International Center for Research on Cancer has classified it as a first-level human carcinogen.
Dioxins have properties similar to those of the "12", a group of dangerous chemicals known as persistent organic pollutants. Experiments have proven that dioxin can damage a variety of organs and systems. Once it enters the human body, it will stay for a long time because it is chemically stable and easily absorbed by fat tissue. From then on, it accumulates in the body for a long time, possibly through indirect physiological effects. ways to cause cancer. Their half-life in the body is estimated to be 7 to 11 years. In the environment, dioxins tend to accumulate in the food chain. The higher the reliance on animal foods in the food chain, the higher the accumulation of dioxins.
Natural microorganisms and hydrolysis have little impact on the molecular structure of dioxin. Therefore, it is difficult to naturally degrade and eliminate dioxins in the environment. Its toxicity is expressed as LD50, and the technical term is "half lethal dose". It is very toxic, 130 times more toxic than cyanide and 900 times more toxic than arsenic. It is known as the "poison of the century". The International Center for Research on Cancer has classified it as a first-level human carcinogen. Environmental experts say that dioxins often exist in the atmosphere, soil and water as tiny particles, and the main sources of pollution are industries such as the chemical and metallurgical industries, waste incineration, papermaking, and pesticide production. Plastic bags, PVC (polyvinyl chloride) soft glue and other items used in daily life contain chlorine. When these items are burned, dioxins will be released and suspended in the air.
Toxicity statement:
The toxicity of dioxins varies depending on the number and position of substitutions of chlorine atoms. Those containing 1-3 chlorine atoms are considered to have no obvious toxicity. ; Toxic substances containing 4-8 chlorine atoms, among which 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is known to humans so far The most toxic pollutant, the International Center for Research on Cancer has classified it as a first-level human carcinogen; if not only the 2, 3, 7, and 8 positions are replaced by 4 chlorine atoms, the other 4 substitution positions are also replaced by chlorine atoms. Atom substitution, then as the number of chlorine atom substitutions increases, its toxicity will be weakened. Since environmental dioxins mainly exist in the form of mixtures, when evaluating the toxicity of dioxin, the international community often converts each congener into an amount equivalent to 2,3,7,8-TCDD. It is called the toxic equivalent (ToxicEquivalentQuangtity, TEQ for short).
To this end, the concept of Toxic Equivalency Factor (TEF) is introduced, which is a coefficient obtained by comparing the toxicity of a certain PCDDs/PCDFs with the toxicity of 2,3,7,8-TCDD. The product of the mass concentration or mass fraction of a certain PCDDs or PCDFs in a sample and its toxic equivalent factor TEF is its toxic equivalent (TEQ) mass concentration or mass fraction. The toxicity of the sample is equal to the sum of the TEQ of all congeners in the sample.
Among the dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3 , 7,8-TCDD) is the most toxic. Just one ounce (28.35 grams) can kill 1 million people, which is equivalent to 1000 times that of potassium cyanide (KCN). This is by far the most toxic compound and contains It is one of the most toxic substances and therefore the most studied.
Structural properties:
Dioxin refers to a chlorine-containing organic compound containing two or one oxygen bond connecting two benzene rings. Its English name is "Dioxin". Due to the different substitution positions of Cl atoms in 1 to 9, 75 isomers of polychlorinated diphenyls (PCDD) and 135 isomers of polychlorinated dibenzofurans (PCDF) are commonly referred to as dioxins. The molecular weight is 321.96, it is a white crystal, m.p.: 302~305℃, it starts to decompose at 500℃, and it completely decomposes in 21s at 800℃. Among them, 17 species (those whose positions 2, 3, 7, and 8 are replaced by Cl) are considered to be the most serious hazards to humans and organisms. Its structure is shown in the figure.
Dioxin molecular structure diagram
Dioxins are stable in nature. The half-life in soil is 12a. The half-life of gaseous dioxin in photochemical decomposition in the air is 8.3d. In humans, It is degraded slowly in the body and mainly accumulates in adipose tissue. Dioxin is a highly toxic organic chemical substance containing Cl. It almost does not exist in nature and can only be produced through chemical synthesis. It is the most terrifying chemical substance currently created by humans and is known as "the most toxic substance on earth." poison".
Sources of pollution:
Environmental experts say that "dioxins" often exist in the atmosphere, soil and water as tiny particles. The main sources of pollution are the chemical and metallurgical industries and garbage incineration. , papermaking and pesticide production industries. Plastic bags, PVC (polyvinyl chloride) soft glue and other items used in daily life contain chlorine. When these items are burned, dioxins will be released and suspended in the air.
Air Pollution and Dioxins
90% of the dioxins in the atmospheric environment come from the incineration of municipal and industrial waste. Leaded gasoline, coal, preservative-treated wood and petroleum products, and various wastes, especially medical wastes, are prone to produce dioxins when the combustion temperature is lower than 300-400°C. Dioxins can be released into the environment from processes such as the production of polyvinyl chloride plastics, paper, chlorine, and certain pesticides, steel smelting, and high-temperature chlorine activation of catalysts. Dioxins also exist as impurities in some pesticide products such as pentachlorophenol, 2,4,5-T, etc.
The formation mechanism of dioxin during the incineration of urban industrial waste is still under study. At present, it is believed that there are three main ways: 1. During the incineration process of chlorine-containing plastics such as vinyl chloride, the incineration temperature is lower than 800°C, and chlorine-containing garbage is incompletely burned, and dioxins are easily generated. After combustion, chlorobenzene is formed, which becomes the precursor of dioxin synthesis; 2. Other chlorine- and carbon-containing substances such as paper, wood products, food residues, etc. are not generated by chlorobenzene through the catalysis of copper, cobalt and other metal ions. Dioxins. 3. Derived from the process of manufacturing chemicals including pesticides, especially chlorine-based chemicals, such as insecticides, herbicides, wood preservatives, defoliants (used by the US military in the Vietnam War), polychlorinated biphenyls and other products .
In addition, if the TV is not cleaned in time, brominated dioxins will usually be detected in the dust accumulated inside the TV. And the content is relatively high. On average, 4.1 micrograms of brominated dioxin can be detected in every gram of dust.
Distribution area:
Although dioxin originates locally, its environmental distribution is global. Dioxins have been found in almost every medium in the world. The greatest accumulation of these compounds is in soil, sediments and food, especially dairy, meat, fish and shellfish. Its levels in plants, water and air are very low.
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Sources of Dioxins
The massive storage of waste oils from the PCB industry, many of which contain high concentrations of PCDFs, is a global phenomenon. Long-term storage and improper disposal of this material can result in dioxins leaking into the environment, resulting in contamination of human and animal food. PCB waste is difficult to dispose of without polluting the environment and humans. This material needs to be treated as hazardous waste and is best disposed of by high temperature incineration.
Health effects:
Feminization
Dioxins are representatives of environmental endocrine disruptors. They can interfere with the body's endocrine system and produce widespread health effects. Dioxins can cause ovarian dysfunction in female animals, inhibit the effects of estrogen, and cause infertility, reduced fetuses, and miscarriage in female animals. Low doses of dioxins can cause cleft palate and hydronephrosis in fetal rats. Male animals given dioxin will experience a decrease in sperm cells, degeneration of mature sperm, and feminization of male animals. Epidemiological studies have found that male workers exposed to 2,3,7,8-TCDD in production have reduced serum testosterone levels and increased follicle-stimulating hormone and progesterone, suggesting that it may act as an antiandrogen and feminize men. role.
Dioxins have obvious immunotoxicity, which can cause thymus atrophy, cellular immunity and humoral immune function reduction in animals. Dioxins can also cause skin damage, and the occurrence of skin hyperkeratosis, pigmentation, and chloracne can be observed in exposed experimental animals and humans. Animals exposed to dioxin can develop liver enlargement, parenchymal cell proliferation and hypertrophy, and degeneration and necrosis in severe cases.
Carcinogenic
2,3,7,8-TCDD is extremely carcinogenic to animals. Infection with 2,3,7,8-TCDD can induce tumors in multiple locations in experimental animals. Epidemiological studies have shown that dioxin exposure can increase the risk of cancer in the population. Based on the results of animal experiments and epidemiological studies, the International Agency for Research on Cancer (IARC) identified 2,3,7,8-TCDD as a Class I human carcinogen in 1997.
Compared with rural areas, the atmosphere in cities, industrial areas or areas closer to pollution sources contains higher concentrations of dioxins. The amount of dioxins that the general population is exposed to through the respiratory route is very small, which is estimated to be about 1% of the intake through the digestive tract, which is about 0.03pgTEQ (kg?d). In some special circumstances, the amount of dioxins exposed through the respiratory route cannot be ignored. A survey showed that the dioxin content in the blood of waste incineration workers was 806pgTEQ/L, which is about 40 times the level of the normal population. Dioxins discharged into the atmospheric environment can be adsorbed on particulate matter, settle into water bodies and soil, and then enter the human body through enrichment in the food chain. Food is the main source of dioxins in the human body. Transplacental and breastfeeding exposure can result in fetal and infant dioxin exposure. People with frequent exposure are more likely to get cancer.
Autism
Defoliant is an industrially synthesized venom that kills plants or causes leaves to fall off. The active ingredient is a highly toxic substance that can cause congenital malformations and cancer. Substance Dioxins. A study by Japanese researchers shows that dioxin accumulation in the mother's body can exacerbate autism tendencies in children.
During the Vietnam War, the US military implemented the "Operation Ranch Plan" and used aircraft to spray large amounts of defoliants into the jungles of Vietnam. After the war, many deformed children appeared in Vietnam. The spontaneous abortion rate and birth defect rate of the wives of soldiers who participated in the war were higher than that of ordinary people. These are believed to be related to the use of defoliants.
The US military once stored and shipped defoliants in Da Nang, Vietnam. Researchers from Japan's Kanazawa Medical University and Toyama University collaborated with Vietnam Military Medical University to conduct the world's first study on dioxin and autism on 153 children born in Da Nang from July 2008 to January 2009. Research on the relationship between disease tendencies.
Treatment method:
Taiwan Sun Yat-sen University and Kaohsiung Chung Hsiu University of Science and Technology collaborated to find a type of bacteria that can "eat" toxic dioxin from soil samples contaminated by dioxin at the Anshun Factory in Tainan. Dioxins are eaten quickly and in large quantities. This discovery will be the most economical and effective way to remediate dioxin-contaminated land. Taiwanese media reported that although the Anshun plant of Taiwan's "China Petroleum & Chemical Industry Corporation" in Annan District, Tainan City was closed in 1982, the nearby land and rivers were severely polluted by dioxin and mercury, and it was regarded by environmental groups as the world's most dangerous plant. The most poisonous block.
High concentrations of dioxin can affect human health. The dioxin-contaminated soil at the Anshun factory has been sealed in a space package for five or six years. There is still no effective and economical method for fundamental remediation. Kaohsiung Zhengxiu University of Science and Technology has detected hundreds of bacteria from contaminated soil. In the past year, it has collaborated with the Institute of Biochemistry at Sun Yat-sen University to screen hundreds of bacterial strains in soil samples to identify bacteria that use dioxin as a food source. And found that "eat very quickly". Zhang Jianguoping, director of the Ultra-Trace Analysis Research and Technology Center of HKUST, said on the 18th that this bacteria is "the natural nemesis of dioxin." "As long as it is moved into soil contaminated by dioxin, and after a period of time, the bacteria will multiply to a sufficient number, You can "eat" the dioxin without removing the soil, which will save up to NT$10 billion to NT$20 billion in remediation costs. "
If we can use the bacteria that reproduce quickly in nature to deal with them. Self-purification of dioxin-contaminated land will be the most cost-effective remediation method. "In the past, environmental testing units and academic units focused on detecting pollutants and never connected with the microbial community." Zhang Jianguoping said that both Zhengxiu and Zhongshan were very excited about this major discovery, describing it as "a very exciting discovery." . Zhang Jianguoping did not want to disclose the name of the bacteria, saying only that "it is a difficult technology to capture this kind of bacteria from the soil." He said that last week, he had applied for a patent with Taiwan's Ministry of Economic Affairs with the Institute of Biochemistry of Sun Yat-sen University, which he collaborated with. The research team will also publish the research results in an internationally renowned scientific issue to allow the academic community to share this new discovery.