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Lead poisoning (also known as plumbism, colica pictorum, saturnism, Devon colic, or painter's colic) is a type of metal poisoning and a medical condition in humans and other vertebrates caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems. It interferes with the development of the nervous system and is therefore particularly toxic to children, causing potentially permanent learning and behavior disorders. Symptoms include abdominal pain, confusion, headache, anemia, irritability, and in severe cases seizures, coma, and death. Routes of exposure to lead include contaminated air, water, soil, food, and consumer products. Occupational exposure is a common cause of lead poisoning in adults. According to estimates made by the National Institute of Occupational Safety and Health (NIOSH), more than 3 million workers in the United States are potentially exposed to lead in the workplace. One of the largest threats to children is lead paint that exists in many homes, especially older ones; thus children in older housing with chipping paint or lead dust from moveable window frames with lead paint are at greater risk. Prevention of lead exposure can range from individual efforts (e.g., removing lead-containing items such as piping or blinds from the home) to nationwide policies (e.g., laws that ban lead in products, reduce allowable levels in water or soil, or provide for cleanup and mitigation of contaminated soil, etc.) Elevated lead in the body can be detected by the presence of changes in blood cells visible with a microscope and dense lines in the bones of children seen on X-ray, but the main tool for diagnosis is measurement of the blood lead level. When blood lead levels are recorded, the results indicate how much lead is circulating within the blood stream, not the amount stored in the body.〔(Blood Lead Level Testing ), Department of Ecology State of Washington. 2011〕 There are two units for reporting blood lead level, either micrograms per deciliter (µg/dl), or micrograms per 100 grams (µg/100 g) of whole blood, which are numerically equivalent. The Centers for Disease Control (US) has set the standard elevated blood lead level for adults to be 10 µg/dl of the whole blood. For children the number is set much lower at 5 µg/dl of blood as of 2012 down from a previous 10 µg/dl.〔(【引用サイトリンク】url=http://www.cdc.gov/nceh/lead/ACCLPP/Final_Document_010412.pdf )〕 Children are especially prone to the health effects of lead. As a result, blood lead levels must be set lower and closely monitored if contamination is possible.〔 The major treatments are removal of the source of lead and chelation therapy (administration of agents that bind lead so it can be excreted). Humans have been mining and using this heavy metal for thousands of years, poisoning themselves in the process. Although lead poisoning is one of the oldest known work and environmental hazards, the modern understanding of the small amount of lead necessary to cause harm did not come about until the latter half of the 20th century. No safe threshold for lead exposure has been discovered—that is, there is no known sufficiently small amount of lead that will not cause harm to the body. ==Classification== Classically, "lead poisoning" or "lead intoxication" has been defined as exposure to high levels of lead typically associated with severe health effects.〔Grant (2009) p. 785〕 Poisoning is a pattern of symptoms that occur with toxic effects from mid to high levels of exposure; toxicity is a wider spectrum of effects, including subclinical ones (those that do not cause symptoms). However, professionals often use "lead poisoning" and "lead toxicity" interchangeably, and official sources do not always restrict the use of "lead poisoning" to refer only to symptomatic effects of lead.〔 The amount of lead in the blood and tissues, as well as the time course of exposure, determine toxicity.〔 Lead poisoning may be acute (from intense exposure of short duration) or chronic (from repeat low-level exposure over a prolonged period), but the latter is much more common.〔Trevor, Katzung, Masters (2007) p. 479〕 Diagnosis and treatment of lead exposure are based on blood lead level (the amount of lead in the blood), measured in micrograms of lead per deciliter of blood (μg/dL). Urine lead levels may be used as well, though less commonly. In cases of chronic exposure lead often sequesters in the highest concentrations first in the bones, then in the kidneys. If a provider is performing a provocative excretion test, or "chelation challenge", a measurement obtained from urine rather than blood is likely to provide a more accurate representation of total lead burden to a skilled interpreter.〔Lowry, Jennifer A. (2010) (ORAL CHELATION THERAPY FOR PATIENTS WITH LEAD POISONING ). ''WHO''〕 The US Centers for Disease Control and Prevention and the World Health Organization state that a blood lead level of 10 μg/dL or above is a cause for concern; however, lead may impair development and have harmful health effects even at lower levels, and there is no known safe exposure level.〔 Authorities such as the American Academy of Pediatrics define lead poisoning as blood lead levels higher than 10 μg/dL.〔 Lead forms a variety of compounds and exists in the environment in various forms.〔Grant (2009) p. 761〕 Features of poisoning differ depending on whether the agent is an organic compound (one that contains carbon), or an inorganic one.〔 Organic lead poisoning is now very rare, because countries across the world have phased out the use of organic lead compounds as gasoline additives, but such compounds are still used in industrial settings.〔 Organic lead compounds, which cross the skin and respiratory tract easily, affect the central nervous system predominantly.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lead poisoning」の詳細全文を読む スポンサード リンク
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