qiān wū rǎn
2 About LeadPb, a lead, is the silver white heavy metal with a Lead Pb is a silver-white heavy metal with blue color, soft texture and low tensile strength. When heated, lead can be quickly synthesized with oxygen, sulfur and halogens, and lead can slowly dissolve in strong alkaline solutions. Lead is mainly used in the manufacture of lead batteries, lead alloy can be used for casting lead characters, do solder; lead is also used to manufacture radioactive radiation, X-ray protection equipment; lead and its compounds on the human body has a greater degree of toxicity, and can be accumulated in the human body.
3 Sources of lead pollutionLead pollution mainly comes from gasoline combustion exhaust, lead paint, mining, smelting, casting and other industrial production activities. Lead and its compounds is a non-degradable environmental pollutants, stable nature, can be through the wastewater, waste gas, waste residue into the environment in large quantities, resulting in pollution, endangering human health. The damage of lead to the organism is multi-systemic and multi-organic, including the toxic effects on the bone marrow hematopoietic system, nervous system, digestive system and other systems. As a central nervous system poison, lead is more serious harm to children's health and intelligence.
4 Harmful effects of lead pollutionLead is a toxic metal that can especially damage the nervous system of children, and it can lead to diseases of the circulatory system and the brain. Prolonged exposure to lead and its salts (especially the soluble and strongly oxidizing PbO2) can lead to kidney disease and colic-like abdominal pain. It has been suggested that the Alzheimer's disease of many ancient Roman emperors was caused by the use of lead as plumbing at the time (as well as the use of lead salts as a sweetener added to wine). Also, lead is very difficult to get rid of on its own when it builds up in the body and can only be removed by certain medications. There are claims that seaweed and fungus have heavy-metal-removing properties, and that alternating large quantities of meat and dairy over a certain period of time (say, half a month) can help eliminate lead.
Its use was curtailed because lead was suspected of causing mental decline in children. Paint containing lead is no longer sold in developed countries. In Taiwan, medical research has shown that injecting patients with kidney disease who have high levels of lead in their bodies with a lead-eliminating agent can slow the deterioration of kidney disease and delay dialysis for at least four years; this research has a good chance of being effective in lowering Taiwan's healthcare expenditures.
Ceramic products containing lead salts have the potential to cause poisoning, especially if the solutions in the containers are acidic (e.g., fruit juices), which can dissolve lead ions in ceramics. Especially for girls and young women lead can be very harmful.
Chronic lead poisoning is one of the most important occupational diseases. Lead is absorbed very slowly, mainly through the digestive tract and respiratory tract. After absorption, most of the lead is deposited in the bone. The lead salts deposited in the bone are not harmful to the body, and the depth of poisoning is mainly determined by the amount of lead in the blood and tissues, and the lead content in the blood is more than 0.O50.1mg%, which will produce poisoning symptoms. Calcium and lead metabolism have a parallel relationship, and all factors that can affect calcium metabolism in the body can also affect lead metabolism. Lead is mainly excreted by the intestine and kidney, and the amount of intestinal excretion is generally more than that of the kidney. When the amount of lead in the urine exceeds 0.050.08mg/l, lead poisoning should be considered as a possibility. Symptoms of chronic poisoning are extremely diverse and characteristic, mainly including: gastrointestinal disorders such as loss of appetite, constipation (sometimes diarrhea), lead colic due to intestinal spasm, and gray-blue lead lines on the gingiva and buccal mucous membranes due to the deposition of lead sulphide. Headache, dizziness, fatigue, irritability and insomnia occur due to violation of the nervous system, and lead encephalopathy can be developed in the late stage, causing hallucinations, delirium, convulsions, etc.; multiple neuritis can occur in the periphery, and lead-toxic paralysis can occur. In the early stage of poisoning, a large number of naive red blood cells containing alkaliphilic substances, such as dotted red blood cells, reticulocytes, multicolored red blood cells, etc., which is generally regarded as a manifestation of the impaired growth of blood cells in the bone marrow, and in the late stage, the bone marrow can be inhibited and the destruction of red blood cells, resulting in anemia. Specialty drugs for treatment are the chelating agent, calcium sodium edetate, or penicillamine. The efficacy of dimercaprol is often unreliable.
4.1 Acute toxicity10μg/m3, rats exposed to 30 to 40 days, erythrocyte biliverdinogen synthase (ALAD) activity decreased by 80% to 90%, the blood lead concentration of up to 150-200 μg/100ml. obvious symptoms of toxicity. 10μg/m3, rats inhaled for 3 to 12 months, from the lungs to elute down the macrophage decreased by 60%, a variety of symptoms of poisoning. 0.01mg/m3, rats inhaled 3 to 12 months, eluting down the macrophages from the lungs. Multiple toxicity symptoms. 0.01 mg/m3, human occupational exposure, urinary tract inflammation, blood pressure changes, death, fetal death in women.
4.2 Chronic toxicityLong-term exposure to lead and its compounds can lead to palpitations, agitation, blood erythrocytosis. After lead invades the nervous system, insomnia, dreaminess, memory loss, fatigue, which develops into mania, blindness, confusion, coma, and finally death due to cerebrovascular hypoxia. Blood lead levels tend to be higher than 2.16 micromol/L before clinical symptoms appear, so many children have high levels of blood lead in their bodies
Although high, there is no particular discomfort, and mild intellectual or behavioral changes are difficult to be detected by parents or doctors. This is why lead poisoning in children is known as the "hidden killer" in foreign countries.
4.3 CarcinogenesisAnimal studies of inorganic compounds of lead have shown that it may cause cancer. It is also documented that lead is a chronic and cumulative poison, with very different sensitivities in different individuals, and that lead is a potential urological carcinogen in humans.
4.4 TeratogenicityThere is insufficient animal testing to provide evidence that lead and its compounds are teratogenic.
4.5 MutagenicityIn mice fed a diet containing 1% lead acetate, there was an increase in the number of chromosomal gap-break aberrations in leukocyte cultures, which involved individual chromosomes, suggesting that DNA replication was impaired.
4.6 Lead metabolism and degradationInorganic lead and its compounds in the environment are very stable and are not readily metabolized and degraded. The toxicity of lead to the human body is cumulative, 25% of the lead inhaled by the human body is deposited in the lungs, and some of it enters the bloodstream through the dissolution of water. If a person is continuously exposed to air containing 1 μg/m3 of lead, the level of lead in human blood is 1 to 2 μg/100 ml of blood. About 10% of the lead ingested from food and beverages is absorbed. If 10 μg of lead per day from food intake, the blood lead level is 6 to 18 μg/100 ml of blood, a small part of these lead compounds can be excreted through the digestive system, which is mainly through the urine (about 76%) and intestines (about 16%), and the rest through a variety of pathways that are not well known to people, such as through sweating, peeling and hair removal to the metabolism of the end product of the excretion of the body.
4.7 Lead Residues and AccumulationLead is an accumulative poison that humans ingest through the food chain and also from contaminated air, and Americans have higher levels of lead in their lungs than those in Africa, the Near East, and the Far East, due to higher levels of atmospheric lead contamination in the U.S. than in those regions. From the results of human anatomy proved that 70% to 90% of the lead that invades the human body ends up in the form of lead phosphate (PbHPO4) deposited and attached to the bone tissue, and the amount of lead in the bones of modern Americans is 100 times higher than that of ancient people. This fraction of lead gradually increases throughout life, and the lead accumulated in the soft tissues of the body, including the blood, reaches a certain level (early adulthood in humans) and then almost ceases to change, with the excess being excreted from the body on its own (as described above), demonstrating a significant turnover rate. Fish are highly enriched for lead.
4.8 Lead transport and transformationAccording to a 1978 study of lead transport in the world environment by the National Research Council in Ottawa ***, Canada, the world mean concentration of lead in seawater was 0.03 μg/L, and in freshwater 0.5 μg/L. The world mean of lead in the atmosphere in the countryside was 0.1 μg/m3, and the range of concentrations in the atmosphere in the city was 1-10 μg/m3. The world mean of lead in soil and rocks was 0.1 μg/m3, and the range of concentrations in urban atmospheres was 1 to 10 μg/m3. The average background value of lead in soil and rock is 13mg/kg. The environmental fate of lead in the world's soil is: 150,000 tons per year from air to soil, 250,000 tons per year from air to sea, and 416,000 tons per year from soil to sea. The annual transfer from seawater to bottom mud is 400,000 to 600,000 tons. As the lead in water, soil and air is absorbed by organisms and transferred to living organisms, it causes the average value of lead in all kinds of plant foods around the world to range from 0.1 to 1mg/kg (dry weight), and the average value of lead in food products to range from 2.5mg/kg, and the average value of lead in fish to range from 0.2 to 0.6mg/kg, and the lead content in the bodies of crustaceans and mollusks in some polluted coastal areas to be as high as 3000mg/kg or even more. up to 3000mg/kg or more.
5 Lead pollution hazards to the environmentAncient books have recorded that the use of lead pipes to transport drinking water is dangerous. There are many ways for the public to be exposed to lead. In recent years, the public is mainly concerned about lead in petroleum products. Pigments containing lead, especially some old brands of pigments containing high levels of lead, has caused many deaths, so some countries have developed environmental standards that require that the lead content of pigments should be controlled within 600 PPM. Some countries have not yet formulated the standard, but they put up labels to warn users when they sell pigments with high lead content in the market. Residues of lead have also been found in food, either in food contaminated by lead falling from the air, or in canned food contaminated by lead from canning skins. Another important source of lead is lead pipes. Lead pipes or lead-lined pipes, which were used decades ago to build homes, and lead-lined natural refrigerators in the summer, have been banned over the years in favor of plastics or other materials.
The safe limit for lead in drinking water in general is 100 micrograms per liter (μg/l), while the maximum acceptable level is 50 μg/l. Later, the maximum acceptable concentration of lead in tap water was further specified as 50 μg/L (0.05 mg/L). In addition, in order to study the effects of lead on human health, scientists set out to test the lead concentration in human blood samples as a prior indicator of lead poisoning. The data showed that if the drinking water was close to 50 micrograms/liter, the patient's blood sample had a lead concentration of about 30 micrograms/liter or more. The requirements for breastfed infants should be even more stringent, with an average blood lead concentration of no more than 1015 micrograms/liter.