I. Overview: Lead is a non-degradable environmental pollutant and a toxic heavy metal element, it is not an essential element for human body, and the ideal blood lead concentration should be zero. However, due to the prevalence of lead in the environment, a certain amount of lead exists in most individuals to a greater or lesser extent, and its content in the human body above a certain level will be hazardous to health. Children are particularly sensitive to lead toxicity due to their metabolic and developmental characteristics, and often cause damage to the body before clinical symptoms appear. Studies have confirmed that blood lead levels around 100μg/L, although not enough to produce specific clinical manifestations, can adversely affect children’s intellectual development, physical growth, learning ability and hearing. At present, about one-third of urban children in China have excessive blood lead levels (>100μg/L), and more than 85% in some areas with serious industrial pollution. Significantly more than American children, the average blood lead level is about 70-90μg/L higher than American children. II. Causes of lead poisoning. 1.Environmental pollution: leaded gasoline – tetraethyl lead (gasoline riot control agent), industrial pollution – lead dust, lead smoke. 2.Home-pollution: home decoration materials, home decoration project construction, lead dust brought home by lead operation workers, home coal burning, passive smoking, cosmetics, hair dyes. 3, diet: food – popcorn, puffed eggs, fruit, etc. Drinking water – early morning overnight first tap water. 4.School supplies and toys. 3.The way of lead entering human body. 1.Digestive tract: Most of the lead poisoning in children is caused by ingestion through the digestive tract, and 5mg/kg of lead taken orally can cause acute poisoning. Infants are often caused by licking the powder containing lead on mother’s face, sucking the ointment containing lead which is decorated with mother’s nipple and the milk of mother suffering from lead poisoning. When the baby’s milk teeth erupt, it often likes to gnaw on things and can be poisoned by gnawing on the lead-containing paint layer of bed frames and toys. Children with heterophilia may suffer from acute poisoning by swallowing large amounts of paint off the floor or walls. Lead poisoning can also occur from eating acidic food cooked or placed in lead-containing utensils or from drinking or eating lead-contaminated water and food. Leaving leftover canned food in tin cans and storing it in the refrigerator is also a cause of lead poisoning. Overdose of lead-containing drugs by mistake. 2. Respiratory tract: Inhalation of lead-containing fumes and dust. Mechanism of poisoning. Lead enters the human body and circulates mainly in the form of lead dibasic phosphate, lead glycerophosphate, protein complex and lead ions, etc. 95% of lead is stored in bone tissue in the form of lead trisodium phosphate (insoluble), and a small amount remains in liver, kidney, spleen, lung, heart, brain, muscle, bone marrow and blood. The majority of lead in blood is found in red blood cells. When lead is stored in bones, no poisoning symptoms occur, but when the body environment is changed for various reasons (infection, trauma, exertion, alcohol consumption, acidic drugs, etc.), lead trisodium phosphate can be transformed into soluble lead dibasic phosphate and moved to the blood, causing lead poisoning symptoms. Lead poisoning mainly inhibits intracellular enzymes containing sulfhydryl groups and causes biochemical and physiological dysfunction in human body, causes small artery spasm, damages capillary endothelial cells, affects energy metabolism, leads to disorders of porphyrin metabolism, hinders the synthesis of high iron hemoglobin, and changes the normal performance of red blood cells and basement membrane. Inhibit the resynthesis of phosphocreatine in muscle, etc., so that a series of pathological changes occur, among which the changes in the nervous system, kidney, hematopoietic system and blood vessels are particularly significant. V. Clinical manifestations. 1. Acute poisoning: The child has metallic taste in the mouth, salivation, nausea, vomiting, vomit is often in the form of white milk lumps (lead produces white lead oxide in the stomach), abdominal pain, sweating, irritability, refusal to eat, etc. When acute lead poisoning encephalopathy occurs, there is sudden and persistent vomiting (may be jet), accompanied by increased respiration and pulse rate, ataxia, strabismus, convulsions, coma, etc.; at this time, there may be increased blood pressure and optic nerve papillary edema. In small infants, the fontanelle is full, and even the cranial suture is widened and the head circumference is enlarged. In severe lead poisoning, there are often paroxysmal abdominal colic, and liver enlargement, jaundice, oliguria or anuria, and circulatory failure may occur. A few of them have gastrointestinal bleeding and paralytic intestinal obstruction; most of the children do not have fever or have only slight fever. Longer-term cases have “lead appearance” and “lead lines” on teeth and nails (rare in young children). 2.Chronic poisoning: Mostly seen after 2-3 years old, generally from the ingestion of poison to the appearance of symptoms about 3-6 months. The main manifestations are severe toxic neurological lesions, such as seizures, hyperkinesia, aggressive behavior, delayed development of language function, and even loss; however, there are no signs of acute intracranial pressure increase. Such chronic encephalopathies can be sequelae of acute encephalopathies or associated with frequent excessive intake of lead; mental deficits persist. Blindness and hemiparesis may be present in severe cases. Retinal spotting often precedes abnormal urinary lead excretion and is an early sign of lead poisoning, although false positives and false negatives have been reported. long bone x-ray changes are not evident in children before 2 years of age.