Introduction of dioxins
The full names are polychlorinated dibenzo-dioxins (PCDDs) and polychlorinated dibenzofurans (pcdfs)-two benzene rings connected by two oxygen atoms and replaced by two chlorine atoms; Polychlorinated dibenzofurans consist of 1 oxygen atom and two benzene rings substituted by chlorine atoms.
Each benzene ring can replace 1 ~ 4 chlorine atoms, thus forming a variety of isomers, including 75 isomers of PCDDs and 135 isomers of PCDFs. It is very toxic, which is 130 times that of cyanide and 900 times that of arsenic. It is called "the poison of the century".
The International Center for Research on Cancer has listed it as a human first-class carcinogen. Environmental experts say that "dioxins" often exist in the atmosphere, soil and water in the form of tiny particles, and the main pollution sources are chemical metallurgy industry, garbage incineration, paper making and pesticide production.
Plastic bags, PVC (polyvinyl chloride) soft glue and other daily necessities all contain chlorine. When these things burn, they will release dioxins and suspend them in the air. In China, dioxins have been detected in human blood, breast milk and lake sediments. Although the concentration level is low, it also shows the existence of dioxins in our environment.
The production of chlorine-containing pesticides, wood preservatives and herbicides, especially the snail control drug (sodium pentachlorophenol) used to treat schistosomiasis in China, will produce dioxin by-products, and their production and use will make dioxins enter the environment unconsciously.
Sodium pentachlorophenol, as the preferred chemical for snail control, has been used in China for decades, and the annual spraying amount is about 6000 tons, which will inevitably lead to the deposition of dioxins in the spraying area.
Therefore, China has the potential of dioxin pollution. In addition, among the 47 categories of hazardous wastes listed in the National Hazardous Waste List released on October 4th, 1998/kloc-0, at least 13 is directly related to dioxins or may be generated during the treatment.
For example, H04 pesticide waste, H05 wood preservative waste, HW 10 PCB-containing waste, HW 18 incineration residue, HW43 PCB-containing furan waste and HW44 PCB-containing dioxin waste. Therefore, it is of great significance to investigate and control dioxin pollution in the next few years or even more than ten years.