Among the air pollutants emitted from combustion devices, the most important are harmful substances such as organic components (such as benzoflowers), sulfur oxides, nitrogen oxides, unburned combustibles and heavy metals, especially the heavy metal emissions in the form of submicron particles, which pose the greatest threat to the environment. However, among the many pollutants produced by waste incineration, the exploration and understanding of the emission law and inhibition mechanism of heavy metals are relatively shallow, especially in China. Even at very low concentrations, heavy metals and their compounds have considerable toxicity, causing pollution to the ecological environment (water source, atmosphere, soil), and the most serious is direct harm to human body.

Heavy metal pollution will do great harm to human health and natural environment. The biggest characteristic of heavy metal pollution is that heavy metals can not be degraded in the environment and can only migrate. That is to say, once the water body or soil is polluted by heavy metals, the water body and soil cannot eliminate the pollution by their own purification. At the same time, because heavy metals are easy to accumulate in organisms, over time, when heavy metals accumulate to a certain amount in organisms, they will cause teratogenesis or mutation of organisms, and eventually lead to the death of organisms. Another harmful way of heavy metals to human body is through the food chain. Long term exposure of fish and shrimp to the environment with high content of heavy metals will lead to the accumulation of heavy metals in the body. Once these foods are ingested by the human body, after a period of accumulation, they will do great harm to human health.

Copper (Cu): metal copper has little toxicity, but copper compounds can cause poisoning. When the copper in the human body exceeds 100~150 times of the human body's requirement, it can lead to necrotizing hepatitis, hemolytic anemia and other symptoms. Clinical studies have found that many cancer patients have significantly increased serum copper and serum copper blue protein. A detailed sampling survey was conducted among plantation workers who sprayed grapes with copper sulfate as insecticide. It was found that liver damage was common in these people. However, taking a large dose of copper will immediately cause poisoning symptoms such as salivation, nausea, vomiting, hemolysis, gangrene, renal failure and central nervous system inhibition.

Lead (PB): lead can enter the human body through respiratory tract and digestive tract. Long term exposure to lead with a concentration of more than 50mg/l will lead to poisoning. Lead is toxic to all organs of the body, especially the nervous system, blood and cardiovascular system. The most common symptoms of chronic poisoning were anemia, abdominal colic and lead poisoning hepatitis. In the nervous system, the symptoms are autonomic neurasthenia and multiple neuritis, manifested as pituitary lead poisoning nerve paralysis, and lead encephalopathy can occur in severe cases.

Zinc (Zn): some experiments have shown that high zinc in the body will lead to the decrease of high-density lipoprotein in the blood and promote atherosclerosis. High zinc is also conducive to the occurrence of cancer. The soil in North Wales and other places in the United Kingdom contains high levels of zinc, and the incidence of gastric cancer and cancer in the digestive tract is also high. Industrial zinc poisoning can increase the incidence of various types of cancer. Long-term low-dose or short-term high-dose exposure to zinc can cause acute and chronic zinc poisoning.

Iron (FE): researchers have long found that heme containing iron is caused by excessive iron in the body and deposited in the internal organs. The United Kingdom, the United States and other countries have reported that the incidence of lung cancer among iron ore workers is high, and the mortality of lung cancer is 70% higher than that of the general population. Iron can promote the rapid growth of tumor cells.

Nickel (Ni): Although the toxicity of nickel is small, it has a cumulative effect and is a carcinogen. Nickel is easy to accumulate in kidney, spleen and liver. Frequent exposure to nickel salts may cause eczema and dermatitis.

Chromium (CR): among chromium compounds, hexavalent chromium is the most toxic, followed by trivalent chromium, and the toxicity of bivalent chromium and chromium itself is very small. Chromium compounds can enter the human body through the digestive tract, respiratory tract, skin and mucous membrane. Entering the human body through the digestive tract can cause nausea, vomiting, abdominal pain, and can also cause ulcers; When entering the human body through the respiratory tract, it first invades the upper respiratory tract, causing rhinitis, pharyngitis, bronchitis, etc.

Although there are great differences in the composition of heavy metals in garbage in different regions, it is an indisputable fact that garbage contains a large number of heavy metals. In the incineration system, these heavy metals will migrate and be distributed to leachate, incineration fly ash and flue gas discharged into the atmosphere, posing a great threat to human living environment and human life.

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