
get the lead out Informal.
[Middle English led, from Old English lēad, probably of Celtic origin.]
lead lead adj.For more information on lead, visit Britannica.com.
Background
Lead is a dense, soft, low-melting metal. It is an important component of batteries, and about 75% of the world's lead production is consumed by the battery industry. Lead is the densest common metal except for gold, and this quality makes it effective in sound barriers and as a shield against X-rays. Lead resists corrosion by water, so it has long been used in the plumbing industry. It is also added to paints, and it makes a long-lasting roofing material.
Lead is a health hazard to humans if it is inhaled or ingested, interfering with the production of red blood cells. Its use must be carefully controlled, and several formerly common uses of lead are now restricted by the U.S. government. Lead paint is found in many older buildings, but it is now mostly used on outdoor steel structures such as bridges, to improve their weatherability. A lead compound called tetraethyl lead was added to gasoline as early as 1921 because it prevented the "knocking" problem of high-compression automobile engines. However, most gasoline now contains no lead, because lead from car exhaust was a major source of air pollution.
Lead is also commonly used in glass and enamel. In television picture tubes and computer video display terminals, lead helps block radiation, and the inner, though not the outer, portion of the common light bulb is made of leaded glass. Lead also increases the strength and brilliance of crystal glassware. Lead is used to make bearings and solder, and it is important in rubber production and oil refining.
Lead production dates back at least 8,000 years. Lead was used in Egypt as early as 5,000 B.C., and in the time of the Pharaohs it was used in pottery glazes and as solder. It was also cast into ornamental objects. A white lead paint was also used in ancient Egypt, Greece, and Rome. Ancient Rome used lead pipes for its extensive water works. Some of the toxic effects of lead were also noted as early as the Roman era, though lead was also thought to have positive medical qualities. In the 15th and 16th centuries, builders used lead as a roofing material for cathedrals, and lead was also used to hold together the different panels of colored glass in stained glass windows. The first lead battery is credited to a French physicist, Gaston Plante, who invented it in 1859. By 1889, so-called lead-acid storage batteries of the modern type were being commercially produced.
Modern lead mines produce about 3 million metric tons of lead annually. This is only about half the lead used worldwide; the remainder is obtained by recycling. The top producer of lead is Australia, followed by the United States, China, and Canada. Other countries with major lead deposits are Mexico, Peru, Russia, and Kazakhstan.
Raw Materials
Lead is extracted from ores dug from under-ground mines. More than 60 minerals contain some form of lead, but only three are usually mined for lead production. The most common is called galena. The pure form of galena contains only lead and sulfur, but it is usually found with traces of other metals in it, including silver, copper, zinc, cadmium, and antimony as well as arsenic. Two other minerals commercially mined for lead are cerussite and anglesite. Over 95% of all lead mined is derived from one of these three minerals. However, most deposits of these ores are not found alone but mixed with other minerals such as pyrite, marcasite, and zinc blende. Therefore much lead ore is obtained as a byproduct of other metal mining, usually zinc or silver. Only half of all lead used yearly derives from mining, as half is recovered through recycling, mostly of automobile batteries.
Besides the ore itself, only a few raw materials are necessary for the refining of lead. The ore concentrating process requires pine oil, alum, lime, and xanthate. Limestone or iron ore is added to the lead ore during the roasting process. Coke, a coal distillate, is used to further heat the ore.
The Manufacturing
Process
Mining the ore
Concentrating the ore
Flotation
Filtering
Roasting the ore
Blasting
Refining
Costing
Byproducts/Waste
Lead refining produces several byproducts. The gangue, or waste rock, accumulates as the ore is concentrated. Most of the minerals have been removed from the rock, so this waste is not considered by the industry to be an environmental hazard. It can be pumped into a disposal pond, which resembles a natural lake. Sulfuric acid is the major byproduct of the smelting process. Sulfur dioxide gas is released when the ore is roasted at the sinter plant. To protect the atmosphere, fumes and smoke are captured, and the air released by the plant is first cleaned. The sulfur dioxide is collected at a separate acid plant, and converted to sulfuric acid. The refinery can sell this acid as well as its primary product, the lead itself.
Air pollution can result from lead processing as well. The smelter requires a "bag house," that is, a separate facility to filter and vacuum the fumes so that lead is not released into the atmosphere. Nevertheless, lead particles do reach the atmosphere, and in the United States, federal regulations attempt to control how much is allowable. Most of the solid waste product produced by the smelting process is a dense, glassy substance called slag. This contains traces of lead as well as zinc and copper. The slag is more toxic than the gangue, and it must be stored securely and monitored so that it does not escape into the environment or come in contact with populations.
The Future
New developments in the lead industry seem aimed less at improvements in the manufacturing process than towards finding new uses for the lead itself. Since a large proportion of the lead mined and recycled is sold to the automotive industry for batteries, lead producers are quite dependent on the health of the auto industry. But lead producers are interested in finding new applications for lead to give them more market stability.
One recent new application for lead is a lead-fiberglass laminate. Lead sheeting can be laminated between gypsum and fiberglass, forming a superior duct material that helps isolate noise. If this is used in an air conditioning unit, for example, it effectively dampens the din of the machine. Another prospective market for lead is in nuclear waste containment. Safely storing radioactive material is a growing concern around the world. The lead industry is researching canisters made of titanium with an inner layer of lead or lead and plastic, contending that a one-inch layer of lead could add 880 years to the life of a properly buried container. And looking to the cars of the future, researchers in the U.S. and several other countries have been studying ways of improving lead-acid battery technology in order to power electric cars.
Where To Learn More
Periodicals
Goodwin, Frank E. and Dodd S. Carr. "Brilliant Performer." Natural Science, July 1989, pp. 317-23.
King, Angela. "Producers Hunt New Lead Uses." American Metal Market. April 11, 1988, pp. 10-13.
Knights, Mikell. "Higher Auto Output Boosts Lead, Zinc Use." American Metal Market, August 6, 1993, pp. 5-12.
Schmitt, Bill. "Lead, Zinc Vie for Place in Future Electric Cars." American Metal Market, August 6, 1993, p.6.
[Article by: Angela Woodward]
A chemical element, Pb, atomic number 82 and atomic weight 207.19. Lead is a heavy metal (specific gravity 11.34 at 16°C or 61°F), of bluish color, which tarnishes to dull gray. It is pliable, inelastic, easily fusible, melts at 327.4°C (621.3°F), and boils at 1740°C (3164°F). The normal chemical valences are 2 and 4. It is relatively resistant to attack by sulfuric and hydrochloric acids but dissolves slowly in nitric acid. Lead is amphoteric, forming lead salts of acids as well as metal salts of plumbic acid. Lead forms many salts, oxides, and organometallic compounds. See also Periodic table.
Industrially, the most important lead compounds are the lead oxides and tetraethyllead. Lead forms alloys with many metals and is generally employed in the form of alloys in most applications. Alloys formed with tin, copper, arsenic, antimony, bismuth, cadmium, and sodium are all of industrial importance.
Lead compounds are toxic and have resulted in poisoning of workers from misuse and overexposure. However, lead poisoning is presently rare because of the industrial application of modern hygienic and engineering controls. The greatest hazard arises from the inhalation of vapor or dust. In the case of organolead compounds, absorption through the skin may become significant. Some of the symptoms of lead poisoning are headaches, dizziness, and insomnia. In acute cases there is usually stupor, which progresses to coma and terminates in death. The medical control of employees engaged in lead usage involves precise clinical tests of lead levels in blood and urine. With such control and the proper application of engineering control, industrial lead poisoning may be entirely prevented.
Lead rarely occurs in its elemental state. The most common ore is the sulfide, galena. The other minerals of commercial importance are the carbonate, cerussite, and the sulfate, anglesite, which are much more rare. Lead also occurs in various uranium and thorium minerals, arising directly from radioactive decay. Commercial lead ores may contain as little as 3% lead, but a lead content of about 10% is most common. The ores are concentrated to 40% or greater lead content before smelting.
The largest single use of lead is for the manufacture of storage batteries. Other important applications are for the manufacture of tetraethyllead, cable covering, construction, pigments, solder, and ammunition.
Organolead compounds are being developed for applications such as catalysts for polyurethane foams, marine antifouling paint toxicants, biocidal agents against gram-positive bacteria, protection of wood against marine borers and fungal attack, preservatives for cotton against rot and mildew, molluscicidal agents, anthelmintic agents, wear-reducing agents in lubricants, and corrosion inhibitors for steel.
Because of its excellent resistance to corrosion, lead finds extensive use in construction, particularly in the chemical industry. It is resistant to attack by many acids because it forms its own protective oxide coating. Because of this advantageous characteristic, lead is used widely in the manufacture and handling of sulfuric acid.
Lead has long been used as protective shielding for x-ray machines. Because of the expanded applications of atomic energy, radiation-shielding applications of lead have become increasingly important.
Lead sheathing for telephone and television cables continues to be a sizable outlet for lead. The unique ductility of lead makes it particularly suitable for this application because it can be extruded in a continuous sheath around the internal conductors.
The use of lead in pigments has been a major outlet for lead but is decreasing in volume. White lead, 2PbCO3 · Pb(OH)2, is the most extensively used lead pigment. Other lead pigments of importance are basic lead sulfate and lead chromates.
A considerable variety of lead compounds, such as silicates, carbonates, and salts of organic acids, are used as heat and light stabilizers for polyvinyl chloride plastics. Lead silicates are used for the manufacture of glass and ceramic frits, which are useful in introducing lead into glass and ceramic finishes. Lead azide, Pb(N3)2 is the standard detonator for explosives. Lead arsenates are used in large quantities as insecticides for crop protection. Litharge (lead oxide) is widely employed to improve the magnetic properties of barium ferrite ceramic magnets. Also, a calcined mixture of lead zirconate and lead titanate, known as PZT, is finding increasing markets as a piezoelectric material.
1. In typesetting, thin metal strip used as a ruler for spacing between lines of type; pronounced led. See also slug.
2. In stage, screen, or television production, primary player or players around whom the action generally takes place; the principal role.
3. In a vocal group, main singer, who usually sings the melody.
4. In journalism, story of primary importance, particularly a news story or the introductory portion of a news story.
5. Prospective customer who has either expressed an interest in a product or service or who has been referred to the seller by a third party. It is essential that leads be followed up promptly so as to reach the prospect before interest wanes. See also bingo card; friend-of-a-friend; lead generation; lead qualification; member-get-a-member.
| Latent Defects, Late Charge, Late Fee | |
| Lead-Based Paint, Lease |
A mineral of no nutritional interest, since it is not known to have any function in the body. It is toxic and its effects are cumulative. May be present in food from traces naturally present in the soil or as contamination; from shellfish that have absorbed it from seawater; from lead glazes on cooking vessels; and in drinking water where lead pipes are used. Traces are excreted in the urine.
Lead (Pb) is a soft, corrosion-resistant gray metal that is a common environmental contaminant in air, food, paint, and water. Lead is recovered from mined sulfide ores, and has been used to fashion items such as statues and tools since at least 6500 B.C.E. The Romans used lead to fashion potable water piping. The relationship between plumbing and lead has become a permanent part of the English language—the word "plumbing" derives from the Latin word for lead, plumbum. Besides plumbing, lead has been used to manufacture items such as ceramics, cosmetics, lead batteries, leaded paint, and leaded gasoline. Common chemical species of lead used commercially include lead acetate, lead carbonate, lead chloride, and lead oxide.
The Agency for Toxic Substances and Disease Registry (ATSDR) estimates that more than one million workers in one hundred occupations are exposed to lead, such as in the lead-battery recycling and lead-smelting industries. Equally important, almost all persons are exposed to lead in residential settings from sources such as paint chips, food, water, cigarettes, and clothing that has been worn in lead-contaminated work environments.
Adverse health effects from lead exposure have been recognized since the time of the Romans. The National Research Council (NRC) traces society's more recent interest in lead poisoning to an 1839 publication by Tanquerel des Planches, who described lead colic in 1,207 occupationally exposed workers. It is now recognized that even low levels of lead exposure are associated with adverse health effects. The U.S. Centers for Disease Control and Prevention (CDC) has identified a lead concentration of ten micrograms per deciliter (µg/dL) of blood as the level of concern above which significant health risks occur. Acute exposure to lead compounds may cause brain damage, kidney damage, and gastrointestinal distress. Chronic exposure to lead results in effects on the blood, the central nervous system, blood pressure, the kidneys, the male reproductive system, and vitamin D metabolism. Children, particularly impoverished children living in homes with lead paint, are particularly at risk from the toxic effects of lead, and may exhibit slowed cognitive development and decreased intelligence after chronic exposure. Figure 1 identifies the health effects of lead at different blood level concentrations.
Because lead does not biodegrade, the approximately 300 million metric tons of lead produced to date remains in the environment. This suggests that humans will continue to be exposed to lead despite the phasing out of lead in consumer products such as gasoline and paint. In the early 1970s, the federal government recognized that steps had to be taken to reduce human exposure to lead, and banned residential leaded paint (1978), and phased out leaded gasoline between 1975 and 1995. The removal of lead from gasoline has proceeded more slowly in the rest of the world. In some countries leaded gasoline remains a significant source of exposure.
The CDC estimates that children's blood lead levels have declined over eighty percent since the mid-1970s. The Lead Contamination Act of 1988 authorized the CDC to initiate programs to eliminate childhood lead poisoning in the United States. The Lead Contamination Act of 1988 authorized the CDC to make grants to state and local agencies for comprehensive programs designed to screen infants and children for elevated blood lead levels, ensure referral for medical and environmental intervention for lead-poisoned infants and children, and provide education about childhood lead poisoning. Despite this impressive decrease in blood lead levels, more than one million children in the United States have blood lead levels above 10 µg/dL, and are at risk of permanent neurological impairment.
(SEE ALSO: Blood Lead; Environmental Determinants of Health; Heavy Metals; Occupational Disease; Occupational Safety and Health; Regulations Affecting Housing)
Bibliography
Agency for Toxic Substances and Disease Registry (ATSDR) (1993). Toxicological Profile for Lead. Washington, DC: U.S. Department of Health and Human Services.
—— (2000). Case Studies in Environmental Medicine: Lead Toxicity. Available at http://www.atsdr.cdc.gov/HEC/caselead.html.
Centers for Disease Control and Prevention (1997). "Update: Blood Lead Levels—United States 1991–1994." Morbidity and Mortality Weekly Report 46(7):141–146 and erratum in 46(26):607.
Lewis, J. (1985). "Lead Poisoning: A Historical Perspective." EPA Journal. Available at http://www.epa.gov/history/topics/perspect/lead.htm.
National Research Council, Commission on Life Sciences (1993). Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations. Available at http://stills.nap.edu/books/030904927X/html/.
President's Task Force on Environmental Health Risks and Safety Risks to Children (2000). Eliminating Childhood Lead Poisoning: A Federal Strategy Targeting Lead Paint Hazards. Available at http://www.epa.gov/children/whatwe/leadhaz.pdf.
U.S. Environmental Protection Agency (U.S. EPA) (1998). Lead in Your Home: A Parent's Reference Guide. Office of Prevention, Pesticides, and Toxic Substances. Available at http://www.epa.gov/lead/leadrev.pdf.
— MARGARET H. WHITAKER; BRUCE A. FOWLER
n. 1. a lead casting suspended on a line to determine the depth of water.
2. bullets.
See the Introduction, Abbreviations and Pronunciation for further details.
This has many sinister associations. Heavy and dull in colour, it was linked with Saturn, most ill-omened of the planets; until recent times, it often lined the coffins of the rich, to keep them watertight. Being soft enough to write on, it was widely used by the Romans for inscribing curses, which would then be placed in a temple or cemetery (Merrifield, 1987: 137-42).
Lead continued to be seen as sinister or ‘impure’ in the learned systems of alchemy, astrology, and ‘high’ magic. Lead tablets bearing curses and astrological symbols were still being made in the 16th and 17th centuries; one was found buried in Lincoln's Inn, two more in a barrow on the Yorkshire moors, and one in a cupboard at Wilton Place near Dymock (Gloucestershire). They express the wish that the victim should be ruined and/or forced to leave the district (Hole, 1973; 92-3).
1. One of the sections of a masonry wall built up at each corner; supports a line between them which serves as a guide for constructing the remainder of the wall.
2. (pl.) See leads.
3. A soft, malleable, heavy metal; has low melting point and a high coefficient of thermal expansion; very easy to cut and work.
A soft, heavy, silvery-coloured metal (Pb) with a low melting point that was alloyed with copper and tin to form lead-bronze for much of later prehistory. In classical times lead was commonly used on its own for making pipes, roofing plates, and coffins, amongst other things.
Properties and Isotopes
Lead is a dense, relatively soft, malleable metal with low tensile strength. It is a poor conductor of electricity and heat. Lead has a face-centered cubic crystalline structure. It is below tin in Group 14 of the periodic table. Although lead has a lustrous silver-blue appearance when freshly cut, it darkens upon exposure to moist air because of the rapid formation of an oxide film; the film protects the metal from further oxidation or corrosion. All lead compounds are poisonous (see lead poisoning). Lead resists reaction with cold concentrated sulfuric acid but reacts slowly with hydrochloric acid and readily with nitric acid.
The element has four naturally occurring stable isotopes, three of which result from the decay of naturally occurring radioactive elements (thorium and uranium). Since this decay takes place at a constant rate, it is possible to predict either the maximum age of a lead-containing rock or its composition at some earlier date, as long as the rock has not been chemically altered. There are 25 known radioactive isotopes of lead, some of which occur naturally in small amounts.
Natural Occurrence and Processing
Although lead is seldom found uncombined in nature, its compounds are widely distributed throughout the world, principally in the ores galena, cerussite, and anglesite. Australia, the United States, Canada, and Russia are among the chief producers of lead. In the United States galena (a lead sulfide ore) is mined in southern Missouri, with some ore coming from the western states. The ore is concentrated by the flotation process and is then refined by electrolysis or by smelting. About one third of the lead used in the United States is so-called secondary lead, i.e., lead and lead alloys reclaimed chiefly from automobile batteries.
Uses
The single most important commercial use of lead is in the manufacture of lead-acid storage batteries (see battery, electric). It is also used in alloys such as fusible metals, antifriction metals, solder, and type metal. Shot lead is an alloy of lead, antimony, and arsenic. Lead foil is made with lead alloys. Lead is used for covering cables and as a lining for laboratory sinks, tanks, and the "chambers" in the lead-chamber process for the manufacture of sulfuric acid. It is used extensively in plumbing. Because it has excellent vibration-dampening characteristics, lead is often used to support heavy machinery and was used in the foundations of the Pan Am Building built over Grand Central Station in New York City. Lead is also employed as protective shielding against X rays and radiation from nuclear reactors.
Lead has many commonly used compounds. Commercially important are the lead oxides, which have many uses. Litharge is lead monoxide, PbO; red lead is lead tetroxide, Pb3O4; lead peroxide or dioxide, PbO2, is used in matches, as a mordant in dyeing, and as an oxidizing agent. White lead, 2PbCO3·Pb(OH)2 (basic lead carbonate), is an important pigment used in paints, putty, and ceramics. Chrome yellow, PbCrO4, is a bright yellow pigment. "Sublimed white lead," PbSO4·Pb(OH)2 (basic lead sulfate), is also used as a pigment. Lead acetate (sugar of lead) is used as a mordant, and lead azide, Pb(N3)2, is employed as a detonator for explosives. Lead arsenate is used as an insecticide. Tetraethyl lead, used as a antiknock compound in gasoline, is now banned for environmental reasons in the United States and other countries.
Although lead and most of its compounds are only slightly soluble in water, the use of lead pipe to carry drinking water is dangerous, since lead is a cumulative poison that is not excreted from the body (see lead poisoning). The "lead" of lead pencils does not contain lead; it is a mixture of graphite and clay.
Neurotoxin. Lowers IQ and damages the immune system. Fruits, grains, cereal products, and legumes contain the highest concentrations. Fetuses and pregnant women are most at risk.
n.
A heavy blue-gray metal much used in giving stability to light lovers -- particularly to those who love not wisely but other men's wives. Lead is also of great service as a counterpoise to an argument of such weight that it turns the scale of debate the wrong way. An interesting fact in the chemistry of international controversy is that at the point of contact of two patriotisms lead is precipitated in great quantities.
Hail, holy Lead! -- of human feuds the great
And universal arbiter; endowed
With penetration to pierce any cloud
Fogging the field of controversial hate,
And with a sift, inevitable, straight,
Searching precision find the unavowed
But vital point. Thy judgment, when allowed
By the chirurgeon, settles the debate.
O useful metal! -- were it not for thee
We'd grapple one another's ears alway:
But when we hear thee buzzing like a bee
We, like old Muhlenberg, "care not to stay."
And when the quick have run away like pellets
Jack Satan smelts the dead to make new bullets.
| leaching, lb, lb | |
| lead compound, lead screw, leader peptidase |
A chemical element, atomic number 82, atomic weight 207.19, symbol Pb.
A common soft, blue-gray, metallic element. Its atomic number is 82, and its atomic weight is 207. In its metallic form, lead is used as a protective shielding against x-rays. Lead is poisonous, a characteristic that has led to a reduction in the use of lead compound as pigments for paints and inks.

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| Metallic gray |
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| General properties | ||||||||||||||||||||||||||||||||||||||||||||||
| Name, symbol, number | lead, Pb, 82 | |||||||||||||||||||||||||||||||||||||||||||||
| Pronunciation | /ˈlɛd/ LED | |||||||||||||||||||||||||||||||||||||||||||||
| Element category | post-transition metal | |||||||||||||||||||||||||||||||||||||||||||||
| Group, period, block | 14, 6, p | |||||||||||||||||||||||||||||||||||||||||||||
| Standard atomic weight | 207.2 | |||||||||||||||||||||||||||||||||||||||||||||
| Electron configuration | [Xe] 4f14 5d10 6s2 6p2 | |||||||||||||||||||||||||||||||||||||||||||||
| Electrons per shell | 2, 8, 18, 32, 18, 4 (Image) | |||||||||||||||||||||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||||||||||||||||||||
| Phase | solid | |||||||||||||||||||||||||||||||||||||||||||||
| Density (near r.t.) | 11.34 g·cm−3 | |||||||||||||||||||||||||||||||||||||||||||||
| Liquid density at m.p. | 10.66 g·cm−3 | |||||||||||||||||||||||||||||||||||||||||||||
| Melting point | 600.61 K, 327.46 °C, 621.43 °F | |||||||||||||||||||||||||||||||||||||||||||||
| Boiling point | 2022 K, 1749 °C, 3180 °F | |||||||||||||||||||||||||||||||||||||||||||||
| Heat of fusion | 4.77 kJ·mol−1 | |||||||||||||||||||||||||||||||||||||||||||||
| Heat of vaporization | 179.5 kJ·mol−1 | |||||||||||||||||||||||||||||||||||||||||||||
| Molar heat capacity | 26.650 J·mol−1·K−1 | |||||||||||||||||||||||||||||||||||||||||||||
| Vapor pressure | ||||||||||||||||||||||||||||||||||||||||||||||
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| Atomic properties | ||||||||||||||||||||||||||||||||||||||||||||||
| Oxidation states | 4, 2 (Amphoteric oxide) | |||||||||||||||||||||||||||||||||||||||||||||
| Electronegativity | 2.33 (Pauling scale) | |||||||||||||||||||||||||||||||||||||||||||||
| Ionization energies | 1st: 715.6 kJ·mol−1 | |||||||||||||||||||||||||||||||||||||||||||||
| 2nd: 1450.5 kJ·mol−1 | ||||||||||||||||||||||||||||||||||||||||||||||
| 3rd: 3081.5 kJ·mol−1 | ||||||||||||||||||||||||||||||||||||||||||||||
| Atomic radius | 175 pm | |||||||||||||||||||||||||||||||||||||||||||||
| Covalent radius | 146±5 pm | |||||||||||||||||||||||||||||||||||||||||||||
| Van der Waals radius | 202 pm | |||||||||||||||||||||||||||||||||||||||||||||
| Miscellanea | ||||||||||||||||||||||||||||||||||||||||||||||
| Crystal structure | face-centered cubic | |||||||||||||||||||||||||||||||||||||||||||||
| Magnetic ordering | diamagnetic | |||||||||||||||||||||||||||||||||||||||||||||
| Electrical resistivity | (20 °C) 208 nΩ·m | |||||||||||||||||||||||||||||||||||||||||||||
| Thermal conductivity | 35.3 W·m−1·K−1 | |||||||||||||||||||||||||||||||||||||||||||||
| Thermal expansion | (25 °C) 28.9 µm·m−1·K−1 | |||||||||||||||||||||||||||||||||||||||||||||
| Young's modulus | 16 GPa | |||||||||||||||||||||||||||||||||||||||||||||
| Shear modulus | 5.6 GPa | |||||||||||||||||||||||||||||||||||||||||||||
| Bulk modulus | 46 GPa | |||||||||||||||||||||||||||||||||||||||||||||
| Poisson ratio | 0.44 | |||||||||||||||||||||||||||||||||||||||||||||
| Mohs hardness | 1.5 | |||||||||||||||||||||||||||||||||||||||||||||
| Brinell hardness | 38.3 MPa | |||||||||||||||||||||||||||||||||||||||||||||
| CAS registry number | 7439-92-1 | |||||||||||||||||||||||||||||||||||||||||||||
| Most stable isotopes | ||||||||||||||||||||||||||||||||||||||||||||||
| Main article: Isotopes of lead | ||||||||||||||||||||||||||||||||||||||||||||||
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Lead (
/ˈlɛd/) is a main-group element in the carbon group with the symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.
Lead is used in building construction, lead-acid batteries, bullets and shots, weights, as part of solders, pewters, fusible alloys and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stable. Its four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei.
Lead, at certain exposure levels, is a poisonous substance to animals as well as for human beings. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.
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Lead is a bright and silvery (with a very slight shade of blue[1]) metal in a dry atmosphere; upon contact with air, it begins to tarnish. It has a few characteristic properties: high density, softness, ductility and malleability, poor electrical conductivity (compared to other metals), high resistance to corrosion, and ability to react with organic chemicals.[1]
Various traces of other metals change its properties significantly: addition of small amounts of antimony or copper increases hardness and improves the corrosion reflection from sulfuric acid for lead.[1] A few other metals also improve only hardness and fight the metal fatigue, such as cadmium, tin, or tellurium; metals like sodium or calcium also have this ability, but they weaken the chemical stability.[1] Finally, zinc and bismuth simply impair the corrosion resistance (0.1% bismuth content prevent lead from the industrial usage).[1] In return, lead impurities mostly worsen the quality of industrial materials, although there are exceptions: for example, small amounts of lead improve the ductility of steel.[1]
Lead has only one common allotrope, which is face-centered cubic, with the lead–lead distance being 349 pm.[2] At 327.5 °C (621.5 °F),[3] lead melts; the melting point is above that of tin (232 °C, 449.5 °F),[3] but significantly below that of germanium (938 °C, 1721 °F).[4] The boiling point of lead is 1749 °C (3180 °F),[5] which is below than those of both tin (2602 °C, 4716 °F)[3] and germanium (2833 °C, 5131 °F).[4] Densities get simply bigger down the group: the Ge and Sn values (5.23[6] and 7.29 g·cm−3,[7] respectively) are significantly below that of lead: 11.32 g·cm−3.[6]
A lead atom has 82 electrons, having an electronic configuration of [Xe]4f145d106s26p2. In its compounds, lead (unlike the other group 14 elements) most commonly loses its two and not four outermost electrons, becoming lead(II) ions, Pb2+. Such unusual behavior is rationalized by considering the inert pair effect, which occurs because of the stabilization of 6s-orbital due to relativistic effects, which are stronger closer to the bottom of the periodic table.[8] Tin shows a weaker such effect: tin(II) is still a reducer.[8]
The figures for electrode potential show that lead is only slightly easier to oxidize than hydrogen. Lead thus can dissolve in acids, but this is often impossible due to specific problems (such as insoluble salts formation).[9] Powdered lead burns with a bluish-white flame. As with many metals, finely divided powdered lead exhibits pyrophoricity.[10] Toxic fumes are released when lead is burned.
Lead occurs naturally on Earth exclusively in the form of four isotopes: lead-204, −206, −207, and −208.[11] All four can be radioactive as the hypothetical alpha decay of any would release energy, but the lower half-life limit has been put only for lead-204: over 1.4×1017 years.[12] This effect is, however, so weak that natural lead makes no radiation hazard. Three of them are also found in three of the four major decay chains: lead-206, −207 and −208 are final decay products of uranium-238, uranium-235, and thorium-232, respectively. Since the amounts of them in nature depend also on other elements' presence, the isotopic composition of natural lead varies by sample: in particular, the relative amount of lead-206 varies between 20.84% and 27.78%.[11]
Aside from the stable ones, thirty-four radioisotopes have been synthesized: they have the mass numbers of 178–215.[12] Lead-205 is the most stable radioisotope of lead, with a half-life of over 107 years. 47 nuclear isomers (long-lived excited nuclear states), corresponding to 24 lead isotopes, have been characterized. The most long-lived isomer is lead-204m2 (half-life of about 1.1 hours).[12]
Lead is classified as a post-transition metal, being a member of the group 14 of the periodic table. Lead only form a protective oxide layer although finely powdered highly purified lead could ignite in the air. Melted lead oxidises in air to lead monoxide. At 430 °C (810 °F). All chalcogens oxidize lead upon heating.[13]
Fluorine does not oxidize cold lead. Hot lead can be oxidized, but the formation on a protective halide layer lowers the intensity of the reaction above 100 °C (210 °F). The reaction with chlorine is similar: thanks to the chloride layer, lead persistence against chlorine surpasses those of copper or steel up to 300 °C (570 °F).[13]
Water in presence of oxygen attacks lead to start an accelerating reaction. Presence of carbonates or sulfates lead to formation of insoluble lead salts, which prevent the metal from corrosion. So does carbon dioxide, as the insoluble lead carbonate is formed; however, excess of the gas leads to the formation of the soluble bicarbonate; this dangers the usage of lead pipes.[9] Lead dissolves in organic acids (in presence of oxygen) and concentrated (≥80%) sulfuric acid thanks to complexation; however, it is only weakly affected by hydrochloric acid and is stable against hydrofluoric acid, as the corresponding halides are weakly soluble. Lead also dissolves in quite concentrated alkalis (≥10%) thanks to the amphoteric character and solubility of plumbites.[9]
Lead compounds exist mainly in two main oxidation states, +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions.[8]
Three oxides are known: PbO, Pb3O4 (sometimes called "minium"), and PbO2. The monoxide exists as two allotropes: α-PbO and β-PbO, both with layer structure and tetracoordinated lead. The alpha polymorph is red-colored and has the Pb–O distance of 230 pm; the beta polymorph is yellow-colored and has the Pb–O distance of 221 and 249 pm (due to asymmetry).[14] Both polymorphs can exist under standard conditions (beta with small (10−5 relative) impurities, such as Si, Ge, Mo, etc.). PbO reacts with acids to form salts, and with alkalies to give plumbites, [Pb(OH)3]- or [Pb(OH)4]2-.[15] The monoxide oxidizes in air to trilead tetroxide, which at 550 °C (1020 °F) degrades back into PbO.
The dioxide may be prepared by, for example, halogenization of lead(II) salts. Regardless the polymorph, it has a black-brown color. The alpha allotrope is rhombohedral, and the beta allotrope is tetragonal.[15] Both allotropes are black-brown in color and always contain some water, which cannot be removed, as heating also causes decomposition (to PbO and Pb3O4). The dioxide is a powerful oxidizer: it can oxidize hydrochloric and sulfuric acids. It does not reacts with alkaline solution, but reacts with solid alkalies to give hydroxyplumbates, or with basic oxides to give plumbates.[15]
Reaction of lead salts with hydrogen sulfide yields lead sulfide. The solid has the NaCl-like striucture (simple cubic), which it keeps up to the melting point, 1114 °C (2037 °F). When heated in air, it oxidised to the sulfate and then the monoxide.[16] The compounds is almost insoluble in water, weak acids, and (NH4)2S/(NH4)2S2 solution is the key for separation of lead from analythical groups I to III elements, tin, arsenic, and antimony. The compounds, however, dissolves in nitric and hydrochloric acids, to give elemental sulfur and hydrogen sulfide, respectively.[16] Heating a mixture of the monoxide and the sulfide heated together forms the metal.[17]
Heating lead carbonate with hydrogen fluoride yields the hydrofluoride, which decomposes to the difluoride when melts. This white crystalline powder is more soluble than the diiodide, but less than the dibromide and the dichloride.[18] The tetrafluoride, a yellow crystalline powder, is unstable.
Other dihalides are obtained upon heating lead(II) salts with the halides of other metals; lead dihalides precipitate to give white orthorhombic crystals (diiodide forms yellow hexagonal crystals). They can also be obtained by direct elements reaction at temperature exceeding melting points of dihalides. Their solubility increases with temperature; adding more halides first decreases the solubility, but then increases due to complexation, with the maximum coordination number being 6. The complexation depends on halide ion numbers, atomic number of the alkali metal, the halide of which is added, temperature and solution ionic strength.[19] The tetrachloride is obtained upon dissolving the dioxide in hydrochloric acid; to prevent the exothermic decomposition, it is kept under concentrated sulfuric acid. The tetrabromide may not, and the tetraiodide definitely does not exist.[20] The diastatide has also been prepared.[21]
The metal is not attacked by sulfuric or hydrochloric acids. It dissolves in nitric acid with the evolution of nitric oxide gas to form dissolved Pb(NO3)2.[18] It is a well-soluble solid in water; it is thus a key to receive the precipitates of halides, sulfate, chromate, carbonate, and basic carbonate Pb3(OH)2(CO3)2 salts of lead.[22]
The best-known compounds are the two simplest plumbane deratives: tetramethyllead (TML) and tetraethyllead (TEL). The homologs of these, as well as hexaethyldilead (HEDL), are of lesser stability. The tetralkyl deratives contain lead(IV); the Pb–C bonds are covalent. They thus resemble typical organic compounds.[23]
Lead readily forms an equimolar alloy with sodium metal that reacts with alkyl halides to form organometallic compounds of lead such as tetraethyllead.[24] The Pb–C bond energies in TML and TEL are only 167 and 145 kJ/mol; the compounds thus decompose upon heating, with first signs of TEL composition seen at 100 °C (210 °F). The pyrolisis yields of elemental lead and alkyl radicals; their interreaction causes the synthesis of HEDL.[23] TML and TEL also decompose upon sunlight or UV light.[25] In presence of chlorine, the alkyls begin to be replaced with chlorides; the R2PbCl2 in the presence of HCl (a by-product of the previous reaction) leads to the complete mineralization to give PbCl2. Reaction with bromine follows the same principle.[25]
Lead has been commonly used for thousands of years because it is widespread, easy to extract and easy to work with. It is highly malleable and ductile as well as easy to smelt. Metallic lead beads dating back to 6400 BCE have been found in Çatalhöyük in modern-day Turkey.[27] In the early Bronze Age, lead was used with antimony and arsenic.
The largest preindustrial producer of lead was the Roman economy, with an estimated output per annum of 80,000 t, which was typically won as a by-product of extensive silver smelting.[26][28][29] Roman mining activities occurred in Central Europe, Roman Britain, the Balkans, Greece, Asia Minor; Hispania alone accounted for 40% of world production.[26]
Roman lead pipes often bore the insignia of Roman emperors (see Roman lead pipe inscriptions). Lead plumbing in the Latin West may have been continued beyond the age of Theoderic the Great into the medieval period.[30] Many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centers. The Romans also used lead in molten form to secure iron pins that held together large limestone blocks in certain monumental buildings. In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Alchemists accordingly used Saturn's symbol (the scythe, ♄) to refer to lead.
Up to the 17th century, tin was often not differed from lead: lead was called plumbum nigrum (literally, "black plumbum"), while tin was called plumbum candidum (literally, "bright plumbum").[31] Their inherence through history can be seen in other languages: the word "olovo" stands for lead in Czech, but in Russian it ("олово") stands for tin. Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; the English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.
Metallic lead does occur in nature, but it is rare. Lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6 % lead by weight. Other common varieties are cerussite (PbCO3) and anglesite (PbSO4).
Most ores contain less than 10% lead, and ores containing as little as 3% lead can be economically exploited. Ores are crushed and concentrated by froth flotation typically to 70% or more. Sulfide ores are roasted, producing primarily lead oxide and a mixture of sulfates and silicates of lead and other metals contained in the ore.[32]
Lead oxide from the roasting process is reduced in a coke-fired blast furnace to the metal.[33] Additional layers separate in the process and float to the top of the metallic lead. These are slag (silicates containing 1.5% lead), matte (sulfides containing 15% lead), and speiss (arsenides of iron and copper). These wastes contain concentrations of copper, zinc, cadmium, and bismuth that can be recovered economically, as can their content of unreduced lead.[32]
Metallic lead that results from the roasting and blast furnace processes still contains significant contaminants of arsenic, antimony, bismuth, zinc, copper, silver, and gold. The melt is treated in a reverberatory furnace with air, steam, and sulfur, which oxidizes the contaminants except silver, gold, and bismuth. The oxidized contaminants are removed by drossing, where they float to the top and are skimmed off.[32][34]
Since lead ores contain significant concentrations of silver, the smelted metal also is commonly contaminated with silver. Metallic silver as well as gold is removed and recovered economically by means of the Parkes process.[17][32][34]
Desilvered lead is freed of bismuth according to the Betterton-Kroll process by treating it with metallic calcium and magnesium, which forms a bismuth dross that can be skimmed off.[32][34]
Very pure lead can be obtained by processing smelted lead electrolytically by means of the Betts process. The process uses anodes of impure lead and cathodes of pure lead in an electrolyte of silica fluoride.[32][34]
Production and consumption of lead is increasing worldwide. Total annual production is about 8 million tonnes; about half is produced from recycled scrap. The top lead producing countries, as of 2008, are Australia, China, USA, Peru, Canada, Mexico, Sweden, Morocco, South Africa and North Korea.[35] Australia, China and the United States account for more than half of primary production.[36]
In 2010[update], 9.6 million tonnes of lead were produced, of which 4.1 million tonnes came from mining.[37]
At current use rates, the supply of lead is estimated to run out in 42 years.[38] Environmental analyst Lester Brown has suggested lead could run out within 18 years based on an extrapolation of 2% growth per year.[39] This may need to be reviewed to take account of renewed interest in recycling, and rapid progress in fuel cell technology. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of lead in use in society is 8 kg. Much of this is in more-developed countries (20–150 kg per capita) rather than less-developed countries (1–4 kg per capita).
Because of its high density and resistance from corrosion, lead is used for the ballast keel of sailboats. Its high density allows it to counterbalance the heeling effect of wind on the sails while at the same time occupying a small volume and thus offering the least underwater resistance. For the same reason it is used in scuba diving weight belts to counteract the diver's natural buoyancy and that of his equipment. It does not have the weight-to-volume ratio of many heavy metals, but its low cost increases its use in these and other applications.
Lead is used in applications where its low melting point, ductility and high density is an advantage. The low melting point makes casting of lead easy, and therefore small arms ammunition and shotgun pellets can be cast with minimal technical equipment. It is also inexpensive and denser than other common metals.[40] The hot metal typesetting uses a lead based alloy to produce the types for printing directly before printing.
Its corrosion resistance makes it suitable for outdoor applications when in contact with water.
More than half of the worldwide lead production (at least 1.15 million metric tons) is used for automobiles, mostly as electrodes in the lead–acid battery, used extensively as a car battery.[41]
Lead is used as electrodes in the process of electrolysis. Lead is used in solder for electronics, although this usage is being phased out by some countries to reduce the amount of environmentally hazardous waste. Lead is used in high voltage power cables as sheathing material to prevent water diffusion into insulation.
Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, and acidic gases.
Lead is used as shielding from radiation (e.g., in X-ray rooms).[44] Molten lead is used as a coolant (e.g., for lead cooled fast reactors).[45]
Lead is added to brass to reduce machine tool wear. Lead, in the form of strips, or tape, is used for the customization of tennis rackets. Tennis rackets of the past sometimes had lead added to them by the manufacturer to increase weight.[46]
Lead is used to form glazing bars for stained glass or other multi-lit windows. The practice has become less common, not for danger but for stylistic reasons. Lead, or sheet-lead, is used as a sound deadening layer in some areas in wall, floor and ceiling design in sound studios where levels of airborne and mechanically produced sound are targeted for reduction or virtual elimination.[47][48]
Lead is the traditional base metal of organ pipes, mixed with varying amounts of tin to control the tone of the pipe.[49][50]
Lead has many uses in the construction industry (e.g., lead sheets are used as architectural metals in roofing material, cladding, flashing, gutters and gutter joints, and on roof parapets). Detailed lead moldings are used as decorative motifs used to fix lead sheet. Lead is still widely used in statues and sculptures. Lead is often used to balance the wheels of a car; this use is being phased out in favor of other materials for environmental reasons.
Due to its half-life of 22.2 years, the radioactive isotope 210Pb is used for dating material from marine sediment cores by radiometric methods.[citation needed]
Lead compounds are used as a coloring element in ceramic glazes, notably in the colors red and yellow.[51] Lead is frequently used in polyvinyl chloride (PVC) plastic, which coats electrical cords.[52][53]
Lead is used in some candles to treat the wick to ensure a longer, more even burn. Because of the dangers, European and North American manufacturers use more expensive alternatives such as zinc.[54][55] Lead glass is composed of 12–28% lead oxide. It changes the optical characteristics of the glass and reduces the transmission of radiation.[56]
Some artists using oil-based paints continue to use lead carbonate white, citing its properties in comparison with the alternatives. Tetra-ethyl lead is used as an anti-knock additive for aviation fuel in piston-driven aircraft. Lead-based semiconductors, such as lead telluride, lead selenide and lead antimonide are finding applications in photovoltaic (solar energy) cells and infrared detectors.[57]
Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most uses have been discontinued due of the dangers of lead poisoning. Beginning April 22, 2010, US federal law requires that contractors performing renovation, repair, and painting projects that disturb more than six square feet of paint in homes, child care facilities, and schools built before 1978 must be certified and trained to follow specific work practices to prevent lead contamination. Lead chromate is still in industrial use. Lead carbonate (white) is the traditional pigment for the priming medium for oil painting, but it has been largely displaced by the zinc and titanium oxide pigments. It was also quickly replaced in water-based painting mediums. Lead carbonate white was used by the Japanese geisha and in the West for face-whitening make-up, which was detrimental to health.[58][59][60]
Lead is the hot metal that was used in hot metal typesetting. It was used for plumbing (hence the name) as well as a preservative for food and drink in Ancient Rome. Until the early 1970s, lead was used for joining cast iron water pipes and used as a material for small diameter water pipes.[61]
Tetraethyllead was used in leaded fuels to reduce engine knocking, but this practice has been phased out across many countries of the world in efforts to reduce toxic pollution that affected humans and the environment.[62][63][64][65]
Lead was used to make bullets for slings. Lead was used for shotgun pellets in the US until about 1992 when it was outlawed (for waterfowl hunting only) and replaced by non-toxic shot, primarily steel pellets. In the Netherlands, the use of lead shot for hunting and sport shooting was banned in 1993, which caused a large drop in lead emission, from 230 ton in 1990 to 47.5 ton in 1995, two years after the ban.[66]
Lead was a component of the paint used on children's toys – now restricted in the United States and across Europe (ROHS Directive). Lead was used in car body filler, which was used in many custom cars in the 1940s–60s. Hence the term Leadsled. Lead is a superconductor at 7.2 K and IBM tried to make a Josephson effect computer out of lead-alloy.[67]
Lead was also used in pesticides before the 1950s, when fruit orchards were treated (ATSDR). A lead cylinder attached to a long line was used by sailors for the vital navigational task of determining water depth by heaving the lead at regular internals. A soft tallow insert at its base allowed the nature of the sea bed to be determined, further aiding position finding. Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. The term comes from the Roman stylus, called the penicillus, which was made of lead without a wooden holder.[68] When the pencil originated as a wrapped graphite writing tool, the particular type of graphite being used was named plumbago (lit. act for lead, or lead mockup).
Lead is highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can cause nephropathy, and colic-like abdominal pains. It may also cause weakness in fingers, wrists, or ankles. Lead exposure also causes small increases in blood pressure, particularly in middle-aged and older people and can cause anemia. Exposure to high lead levels can severely damage the brain and kidneys in adults or children and ultimately cause death. In pregnant women, high levels of exposure to lead may cause miscarriage. Chronic, high-level exposure have shown to reduce fertility in males.[69] Lead also damages nervous connections (especially in young children) and cause blood and brain disorders. Lead poisoning typically results from ingestion of food or water contaminated with lead; but may also occur after accidental ingestion of contaminated soil, dust, or lead-based paint.[70] It is rapidly absorbed into the bloodstream and is believed to have adverse effects on the central nervous system, the cardiovascular system, kidneys, and the immune system.[71] The component limit of lead (1.0 μg/g) is a test benchmark for pharmaceuticals, representing the maximum daily intake an individual should have. However, even at this low level, a prolonged intake can be hazardous to human beings.[72][73] The treatment for lead poisoning consists of dimercaprol and succimer.[74]
| NFPA 704 |
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| Fire diamond for lead granules |
The concern about lead's role in cognitive deficits in children has brought about widespread reduction in its use (lead exposure has been linked to
During the 20th century, the use of lead in paint pigments was sharply reduced because of the danger of lead poisoning, especially to children.[79][80] By the mid-1980s, a significant shift in lead end-use patterns had taken place. Much of this shift was a result of the U.S. lead consumers' compliance with environmental regulations that significantly reduced or eliminated the use of lead in non-battery products, including gasoline, paints, solders, and water systems. Lead use is being further curtailed by the European Union's RoHS directive. Lead may still be found in harmful quantities in stoneware, vinyl (such as that used for tubing and the insulation of electrical cords), and Chinese brass. Older houses may still contain substantial amounts of lead paint. White lead paint has been withdrawn from sale in industrialized countries, but the yellow lead chromate is still in use. Old paint should not be stripped by sanding, as this produces inhalable dust.
Lead salts used in pottery glazes have on occasion caused poisoning, when acidic drinks, such as fruit juices, have leached lead ions out of the glaze.[81] It has been suggested that what was known as "Devon colic" arose from the use of lead-lined presses to extract apple juice in the manufacture of cider. Lead is considered to be particularly harmful for women's ability to reproduce. Lead(II) acetate (also known as sugar of lead) was used by the Roman Empire as a sweetener for wine, and some consider this to be the cause of the dementia that affected many of the Roman Emperors and even be a partial reason for the Roman Empire's fall (see Decline of the Roman Empire#Lead poisoning).[82]
In the human body, lead inhibits porphobilinogen synthase and ferrochelatase, preventing both porphobilinogen formation and the incorporation of iron into protoporphyrin IX, the final step in heme synthesis. This causes ineffective heme synthesis and subsequent microcytic anemia.[83] At lower levels, it acts as a calcium analog, interfering with ion channels during nerve conduction. This is one of the mechanisms by which it interferes with cognition. Acute lead poisoning is treated using disodium calcium edetate: the calcium chelate of the disodium salt of ethylene-diamine-tetracetic acid (EDTA). This chelating agent has a greater affinity for lead than for calcium and so the lead chelate is formed by exchange. This is then excreted in the urine leaving behind harmless calcium.[84]
Exposure to lead and lead chemicals can occur through inhalation, ingestion and dermal contact. Most exposure occurs through ingestion or inhalation; in the U.S. the skin exposure is unlikely as leaded gasoline additives are no longer used. Lead exposure is a global issue as lead mining and lead smelting are common in many countries. Most countries have stopped using lead-containing gasoline by 2007.[85]
Lead exposure mostly occurs through ingestion. Lead paint is the major source of lead exposure for children. As lead paint deteriorates, it peels, is pulverized into dust and then enters the body through hand-to-mouth contact or through contaminated food, water or alcohol. Ingesting certain home remedy medicines may also expose people to lead or lead compounds.[85] Lead can be ingested through fruits and vegetables contaminated by high levels of lead in the soils they were grown in. Soil is contaminated through particulate accumulation from lead in pipes, lead paint and residual emissions from leaded gasoline that was used before the Environment Protection Agency issue the regulation around 1980.[86]
Inhalation is the second major pathway of exposure, especially for workers in lead-related occupations. Almost all inhaled lead is absorbed into the body, the rate is 20–70% for ingested lead; children absorb more than adults.[85]
Dermal exposure may be significant for a narrow category of people working with organic lead compounds, but is of little concern for general population. The rate of skin absorption is also low for inorganic lead.[85]
According to Agency for Toxic Substance and Disease Registry, a small amount of lead (1%) will store itself in bones and the rest will be excreted through urine and feces within a few weeks of exposure. Children have a harder time excreting lead. Only about 32% of lead will be excreted by a child.[87]
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| Li | Be | B | C | N | O | F | Ne | |||||||||||||||||||||||||||||||||||
| Na | Mg | Al | Si | P | S | Cl | Ar | |||||||||||||||||||||||||||||||||||
| K | Ca | Sc | Ti | V | Cr | Mn | Fe | Co | Ni | Cu | Zn | Ga | Ge | As | Se | Br | Kr | |||||||||||||||||||||||||
| Rb | Sr | Y | Zr | Nb | Mo | Tc | Ru | Rh | Pd | Ag | Cd | In | Sn | Sb | Te | I | Xe | |||||||||||||||||||||||||
| Cs | Ba | La | Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg | Tl | Pb | Bi | Po | At | Rn | |||||||||||
| Fr | Ra | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | Uuq | Uup | Uuh | Uus | Uuo | |||||||||||
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