1.Physical and chemical properties: Manganese (manganese, Mn) is a light gray with metallic luster, specific gravity 7.2, melting point 1260oC, soluble in dilute acids. Exposure: In addition to the trace amounts of manganese contained in food, there are mainly: manganese mining and smelting, manganese welding rod manufacturing, welding and wind cutting of manganese alloys and industrial workers who manufacture and apply manganese dioxide, permanganate and other manganese compounds. Public health emergencies: For example, this Ful River manganese mine pollution caused the tap water to exceed the manganese level. 3. Exposure and internal metabolism: It mainly enters the human body in the form of vapor and soot through the respiratory tract. The absorption through the digestive tract is slow and incomplete (the solubility of manganese in gastric juice is very low), and the absorption through the skin is very little. Manganese in the form of trivalent manganese is transferred in the plasma, and it is combined with β1-globulin in the liver and distributed to the whole body, and more than 97% of manganese in the body is excreted in the feces. 4.The role of manganese to human body: manganese exists in the body as an essential trace element in the form of ions, and the total content is only 12～20 mg. Mainly distributed in muscle, liver, kidney and brain, manganese ingested by human body is absorbed in the intestine, but the absorption rate is only 3%. After the nutrient metabolism in the body, most of the manganese is excreted through the intestine. Manganese is a component of many enzymes in the human body, and it has a very close relationship with human health, so some people call manganese a “life-enhancing element”. Recent research shows that superoxide dismutase (SOD) in the body has anti-aging effect, and this enzyme contains manganese. The main reason for the lack of manganese in human body is the insufficient intake of manganese from the diet; the excessive calcium, phosphorus, iron and phytic acid in food interfere with the absorption of manganese. 5, the distribution of manganese in the human body: manganese is more evenly distributed in all tissues and organs in the body, but it is higher in the brain, liver, pancreas, kidney, heart and other cells where the retina and mitochondria are rich. Mitochondria are the place where cells carry out manganese metabolism and energy conversion, and the energy they produce is needed for life activities. Some people call manganese “anti-aging element”. According to research, manganese is good for preventing cardiovascular disease; according to some plants rich in manganese have anti-cancer effect analysis, manganese has anti-premature aging effect. 6, the mechanism of manganese poisoning: manganese and its compounds in excessive contact can cause manganese poisoning, chronic manganese poisoning is common, the damage to the extrinsic system of the vertebral nerve disorders as the main performance, but the mechanism of toxic effects is not very clear. It is generally believed that: (1) manganese has special affinity for mitochondria and selectively accumulates and acts on mitochondria-rich nerve cells and synapses, inhibiting the activity of mitochondrial adenosine triphosphatase, causing a decrease in adenosine triphosphate (ATP) synthesis, degenerative changes in nerve cells, affecting the transmission function of nerve synapses, and leading to muscle motor coordination dysfunction; after the decrease of ATP synthesis, it can also indirectly interfere with calcium transport by the cell membrane, resulting in increased intracellular calcium, which activates calcium-dependent proteases, nucleases and phosphatases and leads to cell degeneration. (2) Manganese can inhibit the synthesis of acetylcholinesterase, leading to the accumulation of endogenous acetylcholine. (3) Manganese can cause a decrease in 5-hydroxytryptamine and dopamine content in the basal ganglia and striatum. 7, the manifestation of manganese poisoning: The main manifestation in the early stage is the class of neurological signs and autonomic dysfunction, such as memory loss, drowsiness, mental depression and lack of interest in the surrounding things. Some patients can appear more talkative, fast mood change and euphoria. Sometimes the extremities are numb, painful or gastrocnemius muscle spasms. On physical examination, enlarged eye fissures, reduced number of transient eyes, excessive sweating, and tachycardia are seen. If the disease continues to progress, the typical signs and symptoms of extrapyramidal neurological disorders appear. There is a lack of facial expression, confused speech, clumsy movements, slowed walking speed, and a tendency to fall. On examination, there is a significant increase in muscle tone of the extremities, especially when the forearm is rotated forward and backward, there is a cogwheel-like increase in muscle tone, tremor is obvious, squatting is easy to fall, the closed-eye difficult-to-stand test is positive, and the unipedal standing is unstable. In severe cases, there may be a “rooster” or panic gait, with small steps forward, not easy to stop, and not easy to turn. The abdominal wall reflex disappears, the tendon reflex is hyperactive, and the Babinski sign is positive. Fecal manganese, urinary manganese, blood manganese content can be increased, but generally only as a reference indicator. 8.Diagnosis of manganese poisoning: The diagnosis of chronic manganese poisoning is based on the detailed occupational history and on-site labor health investigation data and the clinical manifestations and signs of extravertebral system damage. Comprehensive analysis and exclusion of other causes of tremor paralysis, hepatomegaly and other diseases before diagnosis. The national standard is mainly formulated for occupational chronic manganese poisoning (GBZ-3-2002 – Diagnostic Standards for Occupational Chronic Manganese Poisoning) This standard is applicable to the diagnosis and treatment of occupational chronic manganese poisoning, and non-occupational chronic manganese poisoning can also refer to the implementation.