lead

1. (Symbol Pb) A soft, malleable, ductile, bluish-white, dense metallic element, extracted chiefly from galena and used in containers and pipes for corrosives, solder and type metal, bullets, radiation shielding, paints, and antiknock compounds. Atomic number 82; atomic weight 207.2; melting point 327.5°C; boiling point 1,744°C; specific gravity 11.35; valence 2, 4.
2. A lead weight suspended by a line, used to make soundings.
3. Bullets from or for firearms; shot: pumped the target full of lead.
4. leads Strips of lead used to hold the panes of a window.
5. (Abbr. ld.) Printing. A thin strip of metal used to separate lines of type.
6. leads Chiefly British. A flat roof covered with sheets of lead.
7. 1. Any of various, often graphitic compositions used as the writing substance in pencils.
   2. A thin stick of such material.

1. To cover, line, weight, or fill with lead.
2. Printing. To provide space between (lines of type) with leads.
3. To secure (window glass) with leads.
4. To treat with lead or a lead compound: leaded gasoline; leaded paint.

get the lead out Informal.

1. To start moving or move more rapidly.

[Middle English led, from Old English lēad, probably of Celtic origin.]

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

• The first step in retrieving lead-bearing ore is to mine it underground. Workers using heavy machinery drill the rock from deep tunnels with heavy machinery or blast it with dynamite, leaving the ore in pieces. Then they shovel the ore onto loaders and trucks, and haul it to a shaft. The shaft at a large mine may be a mile or more from the drill or blast site. The miners dump the ore down the shaft, and from there it is hoisted to the surface.

Concentrating the ore

• After the ore is removed from the mine, it is treated at a concentrating mill. Concentrating means to remove the waste rock from the lead. To begin, the ore must be crushed into very small pieces. The ore is ground at the mill, leaving it in particles with diameters of 0.1 millimeter or less. This means the individual granules are finer than table salt. The texture is something like granulated sugar.

Flotation

• The principal lead ore, galena, is properly known as lead sulfide, and sulfur makes up a substantial portion of the mineral. The flotation process collects the sulfur-bearing portions of the ore, which also contains the valuable metal. First, the finely crushed ore is diluted with water and then poured into a tank called a flotation cell. The ground ore and water mixture is called slurry. One percent pine oil or a similar chemical is then added to the slurry in the tank. The tank then agitates, shaking the mixture violently. The pine oil attracts the sulfide particles. Then air is bubbled through the mixture. This causes the sulfide particles to form an oily froth at the top of the tank. The waste rock, which is called gangue, sinks to the bottom. The flotation process is controlled by means of X-ray analyzers. A flotation monitor in the control room can check the metal content of the slurry using the X-ray analysis. Then, with the aid of a computer, the monitor may adjust the proportion of the chemical additive to optimize recovery of the metal. Other chemicals are also added to the flotation cell to help concentrate the minerals. Alum and lime aggregate the metal, or make the particles larger. Xanthate is also added to the slurry, in order to help the metal particles float to the surface. At the end of the flotation process, the lead has been separated from the rock, and other minerals too, such as zinc and copper, have been separated out.

Filtering

• After the ore is concentrated in the flotation cells, it flows to a filter, which removes up to 90% of the water. The concentrate at this point contains from 40-80% lead, with large amounts of other impurities, mostly sulfur and zinc. It is ready at this stage to be shipped to the smelter. The gangue, or rock that was not mineral-bearing, must be pumped out of the flotation tank. It may be dumped into a pond resembling a natural lake, and when the pond eventually fills, the land can be replanted.

Roasting the ore

• The lead concentrate fresh from the filter needs to be further refined to remove the sulfur. After the concentrate is unloaded at what is called the sinter plant, it is mixed with other lead-bearing materials and with sand and limestone. Then the mixture is spread on a moving grate. Air which has been heated to 2,550°F (1,400°C) blows through the grate. Coke is added as fuel, and the sulfur in the ore concentrate combusts to sulfur dioxide gas. This sulfur dioxide is an important byproduct of the lead refining process. It is captured at a separate acid plant and converted to sulfuric acid, which has many uses. After the ore has been roasted in this way, it fuses into a brittle material called sinter. The sinter is mostly lead oxide, but it can also contain oxides of zinc, iron, and silicon, some lime, and sulfur. As the sinter passes off the moving grate, it is broken into lumps. The lumps are then loaded into the blast furnace.

Blasting

• The sinter falls into the top of the blast furnace, along with coke fuel. A blast of air comes through the lower part of the furnace, combusting the coke. The burning coke generates a temperature of about 2,200°F (1,200°C) and produces carbon monoxide. The carbon monoxide reacts with the lead and other metal oxides, producing molten lead, nonmetallic waste slag, and carbon dioxide. Then the molten metal is drawn off into drossing kettles or molds.

Refining

• The molten lead as it comes from the blast furnace is from 95-99% pure. It is called at this point base bullion. It must be further refined to remove impurities, because commercial lead must be from 99-99.999% pure. To refine the bullion, it is kept in the drossing kettle at a temperature just above its melting point, about 626°F (330°C). At this temperature, any copper left in the bullion rises to the top of the kettle and forms a scum or dross which can be skimmed off. Gold and silver can be removed from the bullion by adding to it a small quantity of zinc. The gold and silver dissolves more easily in zinc than in lead, and when the bullion is cooled slightly, a zinc dross rises to the top, bringing the other metals with it.

Costing

• When the lead has been sufficiently refined, it is cooled and cast into blocks which may weigh as much as a ton. This is the finished product. Lead alloys may also be produced at the smelter plant. In this case metals are added to the molten lead in precise proportions to produce a lead material for specific industrial uses. For example the lead commonly used in car batteries, and also for pipe, sheet, cable sheathing, and ammunition, is alloyed with antimony because this increases the metal's strength.

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.

A metal once common in plumbing pipes and paint but now considered a Hazardous Substance. Home sellers must disclose any knowledge they have of the presence of Lead-Based Paint.
Example: When paint peels, the peelings may be ingested by small children. If they eat paint containing lead, it could be hazardous to their health.

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.

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.

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.

For more information on lead, visit Britannica.com.

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.

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.

A chemical element, atomic number 82, atomic weight 207.19, symbol Pb.

• l. acetate — sugar of lead, formed on lead paint surfaces after much weathering; it is palatable and attracts animals to lick the surface, causing lead poisoning.
• l. acetate paper strips — detect hydrogen sulfide gas formation and used as a test for Brucella spp.
• l. arsenate — used as an insecticidal and fungistatic spray in orchards; capable of causing arsenic poisoning.
• l. carbonate — white lead used in paints.
• l. chromate — used in paints as a hardener and coloring agent.
• l. equivalent — measurement of the protective efficiency of clothing and other materials against x-rays, in terms based on comparison with lead sheeting of specific thickness.
• l. letters — used as markers on x-ray films.
• l. poisoning — a form of poisoning caused by the presence of lead or lead salts in the body. Lead poisoning affects the brain, nervous system, blood and digestive system. It can be either chronic or acute. This is a common finding in cattle and in urban dogs because of the frequent presence of lead in the environment in lead paints, and the sweet taste of the paint when it is weathered.
— Adult animals show a subacute syndrome of severe depression, aimless walking, blindness, complete ruminal stasis and a black diarrhea in small amounts. Calves show violent convulsions and death within a few hours. — Poisoning can result from swallowing paint flakes or chewing surfaces covered with lead-based paints, golf balls, newsprint, linoleum, fishing sinkers, or numerous other household objects containing lead. Clinical signs usually include abdominal pain, vomiting, diarrhea and seizures. Basophilic stippling of red blood cells, nucleated red blood cells, and a moderate anemia are characteristic.
• l. protective clothing — aprons and gloves containing lead and worn as protection against scattered x-irradiation.
• red l. — tri-plumbic tetroxide.
• l. shot — see lead poisoning (above).
• l. sulfide — form of lead found in the ore galena.
• l. weights — made of metallic lead, used in window sashes, can cause poisoning.

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.

This article is about the metal. For other uses, see Lead (disambiguation).

thallium ← lead → bismuth Sn ↑ Pb ↓ Uuq 82Pb Periodic table
Appearance
bluish gray Lead bricks being used as radiation shielding
General properties
Name, symbol, number	lead, Pb, 82
Element category	post-transition metal
Group, period, block	14, 6, p
Standard atomic weight	207.2 g·mol−1
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
Specific heat capacity	(25 °C) 26.650 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k at T/K 978 1088 1229 1412 1660 2027
Atomic properties
Oxidation states	4, 2, -4 (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	(300 K) 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
iso NA half-life DM DE (MeV) DP 204Pb 1.4% >1.4×1017 y Alpha 2.186 200Hg 205Pb syn 1.53×107 y Epsilon 0.051 205Tl 206Pb 24.1% 206Pb is stable with 124 neutrons 207Pb 22.1% 207Pb is stable with 125 neutrons 208Pb 52.4% 208Pb is stable with 126 neutrons 210Pb trace 22.3 y Alpha 3.792 206Hg Beta 0.064 210Bi
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Lead (pronounced /ˈlɛd/, led) is a main-group element with symbol Pb (Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air. It has a shiny chrome-silver luster when melted into a liquid.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, and is part of solder, pewter, fusible alloys and radiation shields. Lead has the highest atomic number of all stable elements, although the next element, bismuth, has a half-life so long (longer than the estimated age of the universe) it can be considered stable. Like mercury, another heavy metal, lead is a potent neurotoxin that accumulates in soft tissues and bone over time. Lead poisoning was documented in ancient Rome, ancient Greece, and ancient China.

Contents 1 Characteristics 2 Isotopes 3 Chemistry 3.1 Chloride complexes 3.2 Phase diagrams of solubilities 4 History 5 Occurrence 5.1 Ore processing 5.2 Production and recycling 6 Applications 6.1 Former applications 7 Health effects 7.1 Biochemistry of lead poisoning 7.2 Leaching of lead from metal surfaces 7.3 Exposure pathways 7.4 Occupational exposure 7.5 Testing 8 See also 9 References 10 Further reading 11 External links

Characteristics

This section requires expansion.

Lead is bright and silvery when freshly cut but the surface rapidly tarnishes in air to produce the more commonly observed dull luster normally associated with lead. It is a dense, ductile, very soft, highly malleable, bluish-white metal that has poor electrical conductivity. This true metal is highly resistant to corrosion, and because of this property, it is used to contain corrosive liquids (e.g., sulfuric acid). Because lead is very malleable and resistant to corrosion it is extensively used in building construction, e.g., external coverings of roofing joints. Lead can be toughened by addition of a small amount of antimony or other metals. All lead, except ²⁰⁴Pb, is the end product of a complex radioactive decay. Lead is also poisonous, as are its compounds.

Isotopes

Main article: Isotopes of lead

Lead has many isotopes but 4 stable ones. The 4 stable isotopes are²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb with ²⁰⁴Pb regarded as primordial Pb and 206, 207, 208 are formed from decay of U and Th. The one common radiogenic isotope, ²⁰²Pb, has a half-life of approximately 53,000 years.^[1]

Chemistry

Various oxidized forms of lead are easily reduced to the metal. An example is heating PbO with mild organic reducing agents such as glucose. A mixture of the oxide and the sulfide heated together without any reducing agent will also form the metal.^[2]

2 PbO + PbS → 3 Pb + SO₂

Metallic lead is attacked only superficially by air, forming a thin layer of oxide that protects it from further oxidation. The metal is not attacked by sulfuric or hydrochloric acids. It does, however, dissolve in nitric acid with the evolution of nitric oxide gas to form dissolved Pb(NO₃)₂.

3 Pb + 8 H⁺ + 8 NO−3 → 3 Pb²⁺ + 6 NO−3 + 2 NO + 4 H₂O

When heated with nitrates of alkali metals, metallic lead oxidizes to form PbO (also known as litharge), leaving the corresponding alkali nitrite. PbO is representative of lead's +2 oxidation state. It is soluble in nitric and acetic acids, from which solutions it is possible to precipitate halide, sulfate, chromate, carbonate (PbCO₃), and basic carbonate (Pb₃(OH)₂(CO₃)₂) salts of lead. The sulfide can also be precipitated from acetate solutions. These salts are all poorly soluble in water. Among the halides, the iodide is less soluble than the bromide, which, in turn, is less soluble than the chloride.^[3]

Lead(II) oxide is also soluble in alkali hydroxide solutions to form the corresponding plumbite salt.^[2]

PbO + 2 OH⁻ + H₂O → Pb(OH)2−4

Chlorination of plumbite solutions causes the formation of lead's +4 oxidation state.

Pb(OH)2−4 + Cl₂ → PbO₂ + 2 Cl⁻ + 2 H₂O

Lead dioxide is representative of the +4 oxidation state, and is a powerful oxidizing agent. The chloride of this oxidation state is formed only with difficulty and decomposes readily into lead(II) chloride and chlorine gas. The bromide and iodide of lead(IV) are not known to exist.^[3] Lead dioxide dissolves in alkali hydroxide solutions to form the corresponding plumbates.^[2]

PbO₂ + 2 OH⁻ + 2 H₂O → Pb(OH)2−6

Lead also has an oxide with mixed +2 and +4 oxidation states, red lead (Pb₃O₄), also known as minium.

Lead readily forms an equimolar alloy with sodium metal that reacts with alkyl halides to form organometallic compounds of lead such as tetraethyl lead.^[4]

Chloride complexes

Diagram showing the forms of lead in chloride media.^[5]

Lead(II) forms a series of complexes with chloride, the formation of which alters the corrosion chemistry of the lead. This will tend to limit the solubility of lead in saline media.

Equilibrium constants for aqueous lead chloride complexes at 25 °C^[6]

Pb2+ + Cl− → PbCl+	K1 = 12.59
PbCl+ + Cl− → PbCl2	K2 = 14.45
PbCl2 + Cl− → PbCl3−	K3 = 3.98 ×10−1
PbCl3− + Cl− → PbCl42−	K4 = 8.92 × 10−2

Phase diagrams of solubilities

See also: Phase diagram

Lead(II) sulfate is poorly soluble, as can be seen in the following diagram showing addition of SO₄²⁻ to a solution containing 0.1M of Pb²⁺. The pH of the solution is 4.5, as above that, Pb²⁺ concentration can never reach 0.1M due to the formation of Pb(OH)₂. Observe that Pb²⁺ solubility drops 10,000 fold as SO₄²⁻ reaches 0.1M.

Here it can be seen that the addition of chloride can lower the solubility of lead, however in chloride rich media (such as aqua regia) the lead can become soluble again as anionic chlorocomplexes.

Diagram showing the solubility of lead in chloride media. The lead concentrations are plotted as a function of the total chloride present.[5]

Pourbaix diagram for lead in chloride (0.1 M) media[5]

History

Lead ingots from Roman Britain on display at the Wells and Mendip Museum

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 B.C. have been found in Çatalhöyük in modern-day Turkey.^[7] In the early Bronze Age, lead was used with antimony and arsenic. Lead is mentioned in the Book of Exodus (15:10).

In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Lead pipes that bear the insignia of Roman emperors are still in service^{[citation needed]} and 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. Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; originally it was plumbum nigrum (literally, "black plumbum"), where plumbum candidum (literally, "bright plumbum") was tin. The English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.

Occurrence

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. Other common varieties are cerussite (PbCO₃) and anglesite (PbSO₄).

Ore processing

Lead ore

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.^[8]

Lead oxide from the roasting process is reduced in a coke-fired blast furnace.^[9] This converts most of the lead to its metallic form. Three 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.^[8]

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.^[8][10]

Most lead ores contain significant concentrations of silver, resulting in the smelted metal also containing silver as a contaminant. Metallic silver as well as gold is removed and recovered economically by means of the Parkes process.^[8][10][2]

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.^[8][10]

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.^[8][10]

Production and recycling

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.^[10] Australia, China and the United States account for more than half of primary production.^[11]

• 2008 mine production: 3,886,000 tonnes
• 2008 metal production: 8,725,000 tonnes
• 2008 metal consumption: 8,706,000 tonnes^[12]

At current use rates, the supply of lead is estimated to run out in 42 years.^[13] Environmental analyst, Lester Brown, however, has suggested lead could run out within 18 years based on an extrapolation of 2% growth per year.^[14] This may need to be reviewed to take account of renewed interest in recycling, and rapid progress in fuel cell technology.

Applications

Because of its high density and resistance against corrosion, lead is used for the ballast keel of sailboats. Its high weight-to-volume ratio 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 its 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.

Roman lead water pipes with taps

Lead pipe in Roman baths

This article is in a list format that may be better presented using prose. You can help by converting this article to prose, if appropriate. Editing help is available. (January 2009)

• Lead is a major constituent of the lead-acid battery used extensively as a car battery.^[15]
• Lead is used as a coloring element in ceramic glazes, notably in the colors red and yellow.^[16]
• 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 is frequently used in polyvinyl chloride (PVC) plastic, which coats electrical cords.^[17][18]
• Lead is used as projectiles for firearms and fishing sinkers because of its density, low cost compared to alternative products and ease of use due to relatively low melting point.^[19]
• Lead, or sheet-lead, is used as a sound deadening layer in such areas as wall, floor and ceiling design in sound studios where levels of airborne and mechanically produced sound are targeted for reduction or virtual elimination.^[20][21]
• 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.^[22][23]
• Lead is used as shielding from radiation (e.g., in X-ray rooms).^[24]
• Molten lead is used as a coolant (e.g., for lead cooled fast reactors).^[25]
• Lead glass is composed of 12-28% lead oxide. It changes the optical characteristics of the glass and reduces the transmission of radiation.^[26]
• Lead is the traditional base metal of organ pipes, mixed with varying amounts of tin to control the tone of the pipe.^[27][28]
• 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 unfriendly waste.
• Lead is used in high voltage power cables as sheathing material to prevent water diffusion into insulation.
• Lead is added to brass to reduce machine tool wear.
• Some artists using oil-based paints continue to use lead carbonate white, citing its properties in comparison with the alternatives.
• 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.^[29]
• Lead has many uses in the construction industry (e.g., lead sheets are used as architectural metals in roofing material, cladding, flashings, 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.
• 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.^[30]
• 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.

Former applications

• Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most have been discontinued due of the dangers of lead poisoning. However, 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 for health.
• Lead was the hot metal used in hot metal typesetting.
• Lead was used for plumbing in Ancient Rome.
• Lead was used as a preservative for food and drink in Ancient Rome.
• Lead was used for joining cast iron water pipes and used as a material for small diameter water pipes until the early 1970s.
• Tetraethyl lead was used in leaded fuels to reduce engine knocking; however, this is no longer common practice in the Western world due to its incompatibility with catalytic converters.
  • The EPA banned the use of lead gasoline for highway transportation, beginning January 1, 1996.^[31]
• Lead has been used to make clubs or bats more lethal by melting it into a hole drilled into the top.
• 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.
• Lead was used as a component of toys. Due to toy safety regulations, this use has been stopped in the United States.
• 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.^[32]
• 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 it's base allowed the nature of the sea bed to be determined, further aiding position finding.

Contrary to popular belief, pencil leads have never been made from lead. The term comes from the Roman stylus, called the penicillus, which was made of lead.^[33] 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).

Health effects

Main article: Lead poisoning

Lead is a poisonous metal that can damage 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.^[34] Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO₂) can cause nephropathy, and colic-like abdominal pains. The effects of lead are the same whether it enters the body through breathing or swallowing. Lead can affect 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. 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 in men can damage the organs responsible for sperm production.^{[citation needed]} The antidote/treatment for lead poisoning consists of dimercaprol and succimer.

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 learning disabilities^[35]). Most cases of adult elevated blood lead levels are workplace-related.^[36] High blood levels are associated with delayed puberty in girls.^[37] Lead has been shown many times to permanently reduce the cognitive capacity of children at extremely low levels of exposure.^[38] There appears to be no detectable lower limit, below which lead has no effect on cognition.

During the 20th century, the use of lead in paint pigments was sharply reduced because of the danger of lead poisoning, especially to children.^[39][40][41] 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 brass manufactured in China. Between 2006 and 2007 many children's toys made in China were recalled, primarily due to lead in paint used to color the product.

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; for example, Holland Colours Holcolan Yellow. 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.^[42] 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. For that reason, many universities do not hand out lead-containing samples to women for instructional laboratory analyses.^{[citation needed]} 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.^[43]

Lead as a soil contaminant is a widespread issue, since lead is present in natural deposits and may also enter soil through (leaded) gasoline leaks from underground storage tanks or through a wastestream of lead paint or lead grindings from certain industrial operations.

Lead can also be found listed as a criteria pollutant in the United States Clean Air Act section 108. Lead that is emitted into the atmosphere can be inhaled, or it can be ingested after it settles out of the air. 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.^[44]

Biochemistry of lead poisoning

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.^{[citation needed]} 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.^[45]

Leaching of lead from metal surfaces

It is clear from the Pourbaix diagram below that lead is more likely to corrode in a citrate medium than it is in a non-complexing medium. The central part of the diagram shows that lead metal oxidizes more easily in the citrate medium than in normal water.

The Pourbaix diagram for lead in a non-complexing aqueous medium (e.g., perchloric acid / sodium hydroxide)[5]

The Pourbaix diagram for lead in citric acid/citrate[5]

In a Pourbaix diagram, the acidity is plotted on the x axis using the pH scale, while how oxidizing/reducing nature of the system is plotted on the y axis in terms of volts relative to the standard hydrogen electrode. The diagram shows the form of the element which is most chemically stable at each point, it only comments on thermodynamics and it says nothing about the rate of change (kinetics).

Exposure pathways

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.^[46]

Lead exposure mostly occurs through ingestion. Lead paint is the major source of lead exposure for children. As lead paint deteriorates, it peels, pulverizes and then enters the body through hand-to-mouth contacts or through contaminated food, water or alcohol. Ingesting certain home remedy medicines may also expose people to lead or lead compounds.^[46] Lead can be ingested through fruits and vegetables contaminated by the high levels of lead in the soils. Soil is contaminated due to the lead in pipes, lead dust from old paints and residual lead from gasoline with lead that was used before the Environment Protection Agency issue the regulation around 1980.^[47]

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.^[46]

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.^[46]

Lead remains in the body for long periods in mineralizing tissue (i.e., teeth and bones). The stored lead may be released into the bloodstream, especially in times of calcium stress (e.g., pregnancy, lactation, osteoporosis), or calcium deficiency, and is of particular risk to the developing fetus.^[46]

Occupational exposure

It is widely used in the production of batteries, metal products (solder and pipes), ammunition and devices to shield X-rays leading to its exposure to the people working in these industries. Use of lead in gasoline, paints and ceramic products, caulking, and pipe solder has been dramatically reduced in recent years because of health concerns. Ingestion of contaminated food and drinking water is the most common source of lead exposure in humans. Exposure can also occur via inadvertent ingestion of contaminated soil/dust or lead-based paint.

Testing

Water contamination can be tested with commercially available kits. Analysis of lead in whole blood is the most common and accurate method of assessing lead exposure in human. Erythrocyte protoporphyrin (EP) tests can also be used to measure lead exposure, but are not as sensitive at low blood lead levels (<0.2 mg/L). Lead in blood reflects recent exposure. Bone lead measurements are an indicator of cumulative exposure. While measurements of urinary lead levels and hair have been used to assess lead exposure, they are not reliable.

See also

• Adult Blood Lead Epidemiology and Surveillance
• Lead-Free Toys Act
• Medical geology
• Plumbosolvency
• RoHS directive

References

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Further reading

• Keisch, B., Feller, R. L., Levine, A. S., and Edwards, R. R.: "Dating and Authenticating Works of Art by Measurement of Natural Alpha Emitters". In: Science, 155, No. 3767, p. 1238–1242, 1967.
• Keisch, B: "Dating Works of Art Through their Natural Radioactivity: Improvements and Applications". In: Science, 160, p. 413–415, 1968.
• Keisch, B: "Discriminating Radioactivity Measurements of Lead: New Tool for Authentication". In: Curator, 11, No. 1., p. 41–52, 1968.
• Jose S. Casas and Jose Sordo. Lead Chemistry, Analytical Aspects. Environmental Impacts and Health Effects, 2006, First Edition, ELSEVIER B.V
• R.M. Harrison and D.P.H. Laxen, Lead Pollution Causes and Control, 1981, First Publish, British Library Cataloguing in Publication Data

External links

Wikimedia Commons has media related to: Lead

Look up lead or plumbum in Wiktionary, the free dictionary.

• ATSDR Case Studies in Environmental Medicine: Lead Toxicity U.S. Department of Health and Human Services
• Lead at the Open Directory Project
• Chemistry in its element podcast (MP3) from the Royal Society of Chemistry's Chemistry World: Lead

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