Persistent Organic Pollutants (POPs) are organic chemicals that persist in the environment, have a long half-life, and can accumulate through food webs and adversely affect human health and the environment.

Persistent organic pollutants have environmental persistence, bioaccumulation, long-distance migration ability and high toxicity, so they can cause widespread and long-term harm to humans and wild animals, causing disorders in the body's internal secretion system and destroying the reproductive and immune systems. And induce cancer and nervous system diseases. To address the global problem of persistent pollutants, the international community adopted the Stockholm Convention on May 22, 2001.

 The nature of POPs can generally be summarized as follows:

High toxicity

POPs substances can also cause damage to organisms at low concentrations. For example, the most toxic substances in dioxin are more than 1000 times more toxic than potassium cyanide, which is claimed to be one of the most toxic compounds in the world. The daily intake of dioxin can be 1pg per kilogram of body weight, and the 2,3,7,8-TCDD of dioxins is only tens of picograms enough to kill guinea pigs. The feeding amount of several picograms can cause the abortion of the pregnant monkey. POPs substances also have a biomagnification effect, and POPs can also gradually accumulate into high concentrations through the biological chain, resulting in greater harm.

Persistence

POPs substances are resistant to photolysis, chemical decomposition and biodegradability. For example, the dioxin series has a half-life of 8 to 400 days in the gas phase and 166 days to 2119 years in the aqueous phase, in soils and sediments. About 17 to 273 years.

Accumulation

POPs are highly lipophilic and highly hydrophobic, which bioaccumulates in the adipose tissue of living organisms and can endanger human health through the food chain.

Large liquidity

POPs can travel far and wide through wind and water. POPs are generally semi-volatile and volatilize into the atmosphere at room temperature. Therefore, they can enter the atmosphere or the particles attached to the atmosphere from the water or soil in the form of vapor. Because of their persistence, they can migrate in the atmosphere for a long time without being completely degraded, but the semi-volatiles are So that they do not stay in the atmosphere for a long time, they will settle down under certain conditions, and then volatilize under certain conditions. Repeated volatilization and sedimentation can cause POPs to spread throughout the earth. Because POPs of this nature tend to migrate from warmer places to cooler places, such as the Arctic Circle, where POPs are found in places far from pollution sources.

According to the International POPs Convention, persistent organic pollutants are classified into three categories: pesticides, industrial chemicals and by-products in production.

Insecticides: (1) Aldrin (aldrin): applied to the soil to remove termites, mites, pumpkins, and other insects. Production began in 1949 and has been banned in 72 countries and restricted by 10 countries. (2) Chlordane: Controls termites and fire ants. It is used as a broad-spectrum insecticide in various crops and residential areas. It began production in 1945 and has been banned in 57 countries and restricted by 17 countries. (3) DDT: It has been used as a pesticide insecticide, but it is currently used to control mosquito-borne diseases. It began production in 1942 and has been banned in 65 countries and restricted by 26 countries. (4) Dieldrin: used to control termites, textile pests, and control tropical mosquito-borne diseases, partly used in agriculture. It was produced in 1948 and was banned in 67 countries and restricted by 9 countries. (5) Endrin: spraying insecticides such as cotton and grain, also used to control rodents. Production began in 1951 and has been banned in 67 countries and restricted by 9 countries. (6) Heptachlor: a carrier medium used to kill fire ants, termites, mites, crop pests and diseases, and mosquitoes and flies that spread diseases. Production began in 1948 and has been banned in 59 countries and restricted by 11 countries. (7) Hexachlorobenzene (HCB): First used to treat seeds, it is a fungicide for food crops, which has been banned in 59 countries and restricted by 9 countries. (8) Mirex (mirex): used to kill fire ants, termites and other ants, has been banned in 52 countries, 10 countries are restricted. (9) Toxaphene: Cotton, cereals, fruits, nuts and vegetable insecticides, produced in 1948, has been banned in 57 countries and restricted by 12 countries.

Industrial chemicals: including polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB). (1) PCBs: used as electrical communication equipment in electrical equipment such as transformers, capacitors, liquid-filled high-voltage cables and fluorescent lighting rectification, and in paints and plastics. (2) HCB: an intermediate in chemical production.

By-products in production: dioxins and furans, sources: (1) incomplete combustion and pyrolysis, including municipal waste, hospital waste, wood and waste furniture burning, automobile exhaust, non-ferrous metal production, casting and coking, power generation , cement, lime, brick, ceramics, glass and other industries and accidents that release PCBs. (2) The use of chlorine-containing compounds such as chlorophenols, PCBs, chlorinated pesticides and bacteriocin. (3) Chlor-alkali industry. (4) Pulp bleaching. (5) Food contamination, bio-enrichment of the food chain, migration of paper packaging materials and accidents cause food contamination. International control of POPs: prohibiting and restricting production, use, import and export, and anthropogenic emissions, and managing POPs waste and inventory

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