Lead

History, Occurrence, and Uses

Lead is one of the oldest metals known to civilization. The uses of some of its alloys and salts have been documented early in history. The element derived its symbol Pb from the Latin word plumbium. The metal is rarely found in nature in its native form; however, it is found in several minerals, such as galena (PbS), anglesite (PbSO4), minium (Pb3O4) and cerussite (PbCO3). Its concentration in the earth’s crust is 12.5 mg/kg and in sea water 0.03mg/L.
Lead has numerous applications as metal, alloys and compounds. The major applications of the metal and its alloys such as solder are as materials of construction for pipe lines, plumbing fixtures, wires, ammunition, containers for corrosive acids and shield against short-wavelength radiation. Another major application is in storage batteries in which both the metal and its dioxide are used. Several lead compounds, such as lead chromate (chrome yellow), lead sulfate (white lead), lead tetroxide (red lead), and the basic carbonate are used in paints.

Chemical Properties

Occurring naturally in the earth’s crust, lead is a heavy bluish-gray metal that is lustrous when freshly cut. It is rarely found as a pure metal but rather is complexed with other elements to form lead compounds. Found in ore with copper, zinc, and silver, lead is found in mineral form as galena (PbS), anglesite (PbSO4), and cerussite (PbCO3). It is easily malleable, smelted, and can be added to other metals to form alloys. Resistant to air and water corrosion, it does not mix easily with many solvents but will react with hot acids such as nitric and sulfuric. It has 4 naturally occurring isotopes as well as 17 that have been produced experimentally. Burning with a bluish-white flame, powdered lead displays pyrophoricity and releases toxic fumes when burned.

Lead has had a multitude of practical uses for over 8000 years and reports of poisoning exist in all ancient civilizations, including Greece, Rome, and China. By the second century in Greece, lead was known to cause colic when swallowed, and lead intoxication also produced paralysis.

Physical Properties

Silvery grey metal with bright luster; face-centered cubic crystals; very soft, malleable and ductile; easily cast, rolled and extruded; density 11.3 g/cm3; Moh’s hardness 1, Brinell hardness 4.0 (high purity metal); easily melted, melts at 327.46°C; vaporizes at 1,749°C; vapor pressure 1 torr at 970°C and 10 torr at 1160°C; poor conductor of electricity; electrical resistivity 20.65 microhm–cm at 20°C and of liquid melt 94.6 microhm–cm at its melting point; viscosity of molten metal 3.2 centipoise at its melting point and 2.32 centipoise at 400°C; surface tension 442 dynes/cm at 350°C; tensile strength 2,000 psi; thermal neutron absorption cross section 0.17 barn; standard electrode potential, Pb2+ + 2e– Pb –0.13V; very resistant to corrosion.

Production

Lead is produced commercially from its principal ore, galena (PbS). The ore is associated with sulfides of several metals including iron, copper, zinc, silver, bismuth, arsenic, antimony and tin. The ore is crushed and ground. It then is selectively separated from gangue and other valuable minerals by one or more processes that include gravity separation and flotation. Selective flotation processes are most commonly employed to remove significant quantities of most metal sulfides, silica, and other impurities. This yields relatively pure galena concentrate containing 50 to 80% lead.

Reactions

The metal is not attacked by hot water. But in the presence of free oxygen, lead(II) hydroxide is formed. The overall reaction is:
2Pb + 2H2O + O2 → 2Pb(OH)2
In hard water, however, the presence of small amounts of carbonate, sulfate, or silicate ions form a protective film on the metal surface, and prevent the occurrence of the above reaction and thus, corrosion of the metal.
Lead does not evolve hydrogen readily with acids. Nitric acid attacks the metal readily, forming lead nitrate and oxides of nitrogen:
3Pb + 8HNO3 → 3Pb(NO3)2 + 2NO + 4H2O
This reaction is faster in dilute nitric acid than strong acid. Hydrochloric acid has little effect on the metal. At ordinary temperatures, lead dissolves slowly in hydrochloric acid, forming a coating of lead(II) chloride, PbCl2 over the metal, which prevents further attack.
At ordinary temperatures, lead is not readily attacked by sulfuric acid. A coating of insoluble lead sulfate formed on the metal surface prevents any further reaction of the metal with the acid. The acid is, therefore, stored in specially designed lead containers. Also, the action of hot concentrated sulfuric acid is very low up to about 200°C. However, at temperatures near 260°C, both the concentrated sulfuric and hydrochloric acids dissolve lead completely. At ordinary temperatures, hydrofluoric acid also has little action on the metal. Formation of insoluble PbF2 prevents dissolution of lead in the acid.
Organic acids in the presence of oxygen react slowly with lead, forming their soluble salts. Thus, acetic acid in the presence of oxygen forms lead(II) acetate:
2Pb + 4CH3COOH + O2 → 2Pb(CH3COO)2 + 2H2O
Lead dissolves in alkalies forming plumbite ion, Pb(OH)42¯ with the evolution of hydrogen:
Pb + 2OH¯ + 2H2O → Pb(OH)42¯ + H2
Lead combines with fluorine, chlorine, and bromine, forming bivalent lead halides:
Pb + Cl2 → PbCl2
Fusion with sulfur at elevated temperatures yields lead sulfide, PbS.
The metal is oxidized to PbO when heated with sodium nitrate at elevated temperatures.
Pb + NaNO3 → PbO + NaNO2
Lead is widely used in storage batteries. Each cell consists of a spongy lead plate as cathode and lead dioxide as anode immersed in the electrolyte sulfuric acid. The overall chemical reaction in the cell during discharge is as follows: PbO2 + Pb + 2H2SO4 → 2PbSO4 + 2H2O

Toxicity

Lead is an acute and a chronic toxicant. Acute effects are ataxia, headache, vomiting, stupor, hallucination, tremors and convulsions. Chronic symptoms from occupational exposure include weight loss, anemia, kidney damage and memory loss. (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed. New York: John Wiley & Sons.) Permanent brain damage has been noted among children. Lead bioaccumulates in bones and teeth. The metal is classified as an environmental priority pollutant by the US EPA.
The action level for lead in drinking water is 15μg/L. Its content in food and house paints is regulated in the USA by the Food and Drug Administration.

Lead in Body

The main body compartments that store lead are the blood, soft tissues, and bone; the half-life of lead in these tissues is measured in weeks for blood, months for soft tissues, and years for bone. Lead in the bones, teeth, hair, and nails is bound tightly and not available to other tissues and is generally thought not to be harmful. In adults, 94% of absorbed lead is deposited in the bones and teeth, but children only store 70% in this manner, a fact which may partially account for the more serious health effects on children. The estimated half-life of lead in bone is 20 30 years, and bone can introduce lead into the bloodstream long after the initial exposure is gone. The half-life of lead in the blood in men is about 40 days, but it may be longer in children and pregnant women, whose bones are undergoing remodelling, which allows the lead to be continuously reintroduced into the bloodstream. Also, if lead exposure takes place over years, clearance is much slower, partly due to the rerelease of lead from bone. Many other tissues store lead, but those with the highest concentrations (other than blood, bone, and teeth) are the brain, spleen, kidneys, liver, and lungs. It is removed from the body very slowly, mainly through urine. Smaller amounts of lead are also eliminated through the faeces and very small amounts in hair, nails, and sweat.

Description

Lead was one of the earliest metals used by humans, with possible use extending as far back as the seventh millennium BC, and reaching its preindustrial peak usage during the reign of the Roman Empire, around the beginning of the Common Era.

Chemical Properties

grey metal granules, shot, foil, sheet or powder

Chemical Properties

Lead is a lustrous silvery metal that tarnishes in the presence of air and becomes a dull bluish gray. The chemical symbol, Pb, is derived from plumbum, the Latin word for waterworks, because of lead’s extensive use in ancient water pipes. Lead has four electrons in its valence shell, but only two ionize readily. The usual oxidation state of lead in inorganic compounds is therefore +2 rather than +4. Lead generally forms stable compounds; the most important ones are lead oxide (PbO) and lead carbonate (PbCO₃)₂. Four stable lead isotopes exist in nature (²⁰⁸Pb , ²⁰⁶Pb , ²⁰⁷Pb, and ²⁰⁴Pb , in order of abundance). Lead mined from deposits of different geologic eras has entered the environment, so that today there are wide variations and extensive mixture of isotopic ratios of lead in commerce and in the environment. These differences in isotopic ratios may sometimes be used as nonradioactive tracers in environmental and metabolism studies.

Physical properties

Lead is a bluish-white, heavy metallic element with properties that are more metal-like thanthe properties of metalloids or nonmetals. Lead can be found in its native state, meaning thatelemental metallic lead can be found in deposits in the Earth’s crust. However, most lead isfirst mined as galena ore (lead sulfide, PbS). The galena is mixed with lead sulfate, lead sulfide,and lead oxide and is then roasted at a high temperature. The air supply is reduced, followedby an increase in heat and the vaporization of the sulfates and oxides of lead, which are drawnoff as gases. The molten lead is then recovered.
Lead is only slightly soluble in water. However, it is also toxic. This is the reason lead isno longer used to pipe fresh water into homes. It does not react well with acids, with theexception of nitric acid. Lead’s melting point is 327.46°C, its boiling point is 1,740°C, andits density is 11.342 g/cm³.

Isotopes

There are 47 isotopes of lead, four of which are stable. One of these four is Pb-204, which makes up 1.4% of the natural abundance of lead found on Earth. In reality thisisotope is not stable but has a half-life that is so long (1.4×10⁺¹⁷ years), with some of theancient deposits still existing, that it is considered stable. The other three stable isotopes oflead and their proportion to the total natural abundance are as follows: Pb-206 = 24.1%,Pb-207 = 22.1%, and Pb-208 = 52.4%. All the other isotopes are radioactive.

Origin of Name

From the Latin word alumen, or aluminis, meaning “alum,” which is a bitter tasting form of aluminum sulfate or aluminum potassium sulfate.

Occurrence

Lead is the 35th most abundant element on Earth. Although it has been found in its freeelemental metal state, it is usually obtained from a combination of the following ores: galena(PbS), anglesite (PbSO₄), cerussite (PbCO₃), and minum (Pb₃O₄). Lead ores are locatedin Europe (Germany, Rumania, and France), Africa, Australia, Mexico, Peru, Bolivia, andCanada. The largest deposits of lead in the United States are in the states of Missouri, Kansas,Oklahoma, Colorado, and Montana.
One of the most famous mining towns is the high-altitude western city of Leadville,Colorado. The boom started with the gold rush of the 1860s, followed by silver mining in the1870s and 1880s. Today, this city is the site of mining operations not only for lead, but alsofor zinc and molybdenum. At the height of its fame, Leadville had a population of almost50,000 people. Today the population is about 2,500.
Lead is commonly obtained by roasting galena (PbS) with carbon in an oxygen-rich environmentto convert sulfide ores to oxides and by then reducing the oxide to metallic lead.Sulfur dioxide gas is produced as a waste product. Large amounts of lead are also recoveredby recycling lead products, such as automobile lead-acid electric storage batteries. About onethirdof all lead used in the United States has been recycled.

History

Lead is obtained chiefly from galena (PbS) by a roasting process. Anglesite (PbSO4), cerussite (PbCO3), and minim (Pb3O4) are other common lead minerals. Lead is a bluish-white metal of bright luster, is very soft, highly malleable, ductile, and a poor conductor of electricity. It is very resistant to corrosion; lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. Lead is used in containers for corrosive liquids (such as sulfuric acid) and may be toughened by the addition of a small percentage of antimony or other metals. Natural lead is a mixture of four stable isotopes: ²⁰⁴Pb (1.4%), ²⁰⁶Pb (24.1%), ²⁰⁷Pb (22.1%), and 208Pb (52.4%). Lead isotopes are the end products of each of the three series of naturally occurring radioactive elements: ²⁰⁶Pb for the uranium series, 207Pb for the actinium series, and ²⁰⁸Pb for the thorium series. Forty-three other isotopes of lead, all of which are radioactive, are recognized. Its alloys include solder, type metal, and various antifriction metals. Great quantities of lead, both as the metal and as the dioxide, are used in storage batteries. Lead is also used for cable covering, plumbing, and ammunition. The metal is very effective as a sound absorber, is used as a radiation shield around X-ray equipment and nuclear reactors, and is used to absorb vibration. Lead, alloyed with tin, is used in making organ pipes. White lead, the basic carbonate, sublimed white lead (PbSO4), chrome yellow (PbCrO4), red lead (Pb3O4), and other lead compounds are used extensively in paints, although in recent years the use of lead in paints has been drastically curtailed to eliminate or reduce health hazards. Lead oxide is used in producing fine “crystal glass” and “flint glass” of a high index of refraction for achromatic lenses. The nitrate and the acetate are soluble salts. Lead salts such as lead arsenate have been used as insecticides, but their use in recent years has been practically eliminated in favor of less harmful organic compounds. Care must be used in handling lead as it is a cumulative poison. Environmental concern with lead poisoning led to elimination of lead tetraethyl in gasoline. The U.S. Occupational Safety and Health Administration (OSHA) has recommended that industries limit airborne lead to 50 μg/cu. meter. Lead is priced at about 90￠/kg (99.9%).

Characteristics

Although lead can be found as a metal in the Earth’s crust, it is usually mined and refinedfrom minerals and ores. Lead is one of the most common and familiar metallic elementsknown. Although it is somewhat scarce, found at proportions of 13 ppm, it is still more prevalentthan many other metals. Lead is noncombustible. and it resists corrosion.
When lead, which is very soft, is freshly cut, it has shiny blue-white sheen, which soonoxidizes into its familiar gray color. Lead is extremely malleable and ductile and can be workedinto a variety of shapes. It can be formed into sheets, pipes, buckshot, wires, and powder.Although lead is a poor conductor of electricity, its high density makes it an excellent shieldfor protection from radiation, including X-rays and gamma rays.

Uses

Lead has been known to humankind sinceancient times. It is a major component ofmany alloys, such as bronze and solder. Itis used for tank linings, piping, and buildingconstruction; in the manufacture of pigmentsfor paints, tetraethyllead, and many organicand inorganic compounds; in storage batteries;and in ceramics. Lead levels in manysoils have been range from 5 to 25 mg/kgand in groundwaters from 1 to 50 μg/L.These concentrations may vary significantly.

Uses

Lead has many uses and is an important commercial commodity. One of the most commonuses is in the acid-lead electrical storage batteries used in automobiles. Much of the leadin these devices can be recycled and used again.
In the past, tetraethyl lead was added to gasoline to slow its burning rate in order to preventengine “knock” and increase performance. This caused serious and harmful pollution, and leadhas since been eliminated as a gasoline additive in most countries. Most exterior (and someinterior) house paints once contained high levels of lead as well. Today, the amount of lead inpaint is controlled, with not more than 0.05% allowed in the paint material.
Lead is used to make a number of important alloys. One is solder, an alloy of 1/2 lead and1/2 tin. Solder is a soft, low-melting metal that, when melted, is used to join two or moreother metals-particularly electrical components and pipes.
Babbitt metal is another alloy of lead that is used in the manufacture of wheel bearingsthat reduces friction. Lead is an ingredient in several types of glass, such as lead crystal andflint glass.
TV screens are coated with lead to absorb any radiation projected by the mechanism, andover 500,000 tons of lead is used in consumer electronics (computers, phones, games, and soon). Much of it ends up in solid waste dumps.
Many lead compounds are poisonous; thus, their uses in insecticides and house paints havebeen limited as other less toxic substances have been substituted. For example, lead arsenate[Pb₃(AsO₄], which is very poisonous, has been replaced in insecticides by less harmful substances.

Uses

In worldwide metal use, lead ranks behind only iron, copper, aluminum, and zinc (Howe 1981). Its largest use is in lead-acid storage batteries for motor vehicles and general industry. Lead metal also is commonly used for ammunition, cable covering, piping, brass and bronze, bearing metals for machinery, and sheet lead (ATSDR 1999).
All of the major soluble lead compounds have industrial uses. Lead acetate is used as a water repellent, for mildew protection, and as a mordant for cotton dyes. Lead acetate trihydrate is used in varnishes, chrome pigments, and as an analytical reagent, and lead chloride is used in asbestos clutch or brake linings, as a catalyst, and as a flame retardant. Lead nitrate is used in the manufacture of matches and explosives, as a heat stabilizer in nylon, and as a coating on paper for photothermography. Lead subacetate is used in sugar analysis and for clarifying solutions of organic substances (HSDB 2009).
The insoluble lead compounds also have a variety of uses. Lead azide and lead styphnate both are used in munitions manufacture. Lead carbonate, lead fluoride, lead fluoborate, and lead naphthenate are used as catalysts, with additional uses in the electronic and optical industries (lead fluoride), in coatings for thermographic copying (lead carbonate), as a curing agent for epoxy resins (lead fluoborate), and as a varnish drier (lead naphthenate). Lead phosphate and lead stearate both are used as stabilizers in the plastics industry. Lead iodide and lead sulfate are used in photography; lead iodide is also used in thermoelectric materials, and lead sulfate with zinc in galvanic batteries. Lead oxide and lead sulfide are used in ceramics; lead oxide is also used as a vulcanizing agent in rubber and plastics, and lead sulfide as a humidity sensor in rockets. Lead chromate is used as a pigment in paints, rubber, and plastics; lead tetraoxide is used in plasters, ointments, glazes, and varnishes; and lead thiocyanate is used in the manufacture of safety matches and cartridges. Lead arsenate formerly was used as an insecticide and herbicide, but no current uses were found.
Organic lead (including tetraethyl lead and tetramethyl lead) was widely used in the United States as an anti-knock additive in motorvehicle fuels until the U.S. Environmental Protection Agency initiated a phase-out of leaded gasoline in the early 1970s. By 1988, the total lead used in gasoline had been reduced to 1% of the 1970 level; in 1996, the use of lead in fuel for on-road motor vehicles was totally banned. Despite the legislated end to use of lead as a gasoline additive and reductions in some other uses of lead, overall U.S. lead consumption continued to grow until 1999, mainly because of increased production of lead-acid batteries (ATSDR 1999), but has since been on a general decline (USGS 2009, 2010, Guberman 2010).

Uses

Construction material for tank linings, piping, and other equipment handling corrosive gases and liqs used in the manufacture of sulfuric acid, petroleum refining, halogenation, sulfonation, extraction, condensation; for x-ray and atomic radiation protection; manufacture of tetraethyllead, pigments for paints, and other organic and inorganic lead Compounds; bearing metal and alloys; storage batteries; in ceramics, plastics, and electronic devices; in building construction; in solder and other lead alloys; in the metallurgy of steel and other metals.

Production Methods

The geometric mean soil lead level is 38 mg/kg. Lead rarely occurs in the elemental state, but exists widely throughout the world in a number of ores, the most common of which is the sulfide, galena. The other minerals of commercial importance are the oxides, carbonate (cerussite), and the sulfate (anglesite), which are much less common.
Lead also occurs in various uranium and thorium minerals, arising directly from radioactive decay. Because certain isotopes are concentrated in lead derivatives from such sources, both the atomic weight and the density of the samples vary significantly from normal lead. Lead ores generally occur in nature in association with silver and zinc. Other metals commonly occurring with lead ores are copper, arsenic, antimony, and bismuth. Most of the world production of arsenic, antimony, and bismuth is a result of their separation from lead ores. Commercial lead ores may contain as little as 3% lead, but a lead content of 10% is most common. The ores are concentrated to ≥ 40% lead content before smelting. A variety of mechanical separation processes may be employed for the concentration of lead ores, but the sulfide ores are generally concentrated by flotation processes.

Definition

lead: Symbol Pb. A heavy dull greysoft ductile metallic element belongingto group 14 (formerly IVB) ofthe periodic table; a.n. 82; r.a.m.207.19; r.d. 11.35; m.p. 327.5°C; b.p.1740°C. The main ore is the sulphidegalena (PbS); other minor sources includeanglesite (PbSO₄), cerussite (PbCO₃), and litharge (PbO). Themetal is extracted by roasting the oreto give the oxide, followed by reductionwith carbon. Silver is also recoveredfrom the ores. Lead has a varietyof uses including building construction,lead-plate accumulators, bullets,and shot, and is a constituent of suchalloys as solder, pewter, bearing metals,type metals, and fusible alloys.Chemically, it forms compoundswith the +2 and +4 oxidation states,the lead(II) state being the more stable.

General Description

Soft silver-bluish white to gray metal.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

In the presence of carbon, the combination of chlorine trifluoride with aluminum, copper, Lead, magnesium, silver, tin, or zinc results in a violent reaction [Mellor 2, Supp. 1: 1956]. A solution of sodium azide in copper pipe with Lead joints formed copper and Lead azide, both are detonating compounds [Klotz 1973]. Sodium acetylide becomes pyrophoric when mixed with metals like Lead. Mixtures of trioxane with 60% hydrogen peroxide in contact with metallic Lead when heated detonated. Lead containing rubber ignited in a nitric acid atmosphere. Lead is incompatible with strong oxidants such as: ammonium nitrate, chlorine trifluoride, hydrogen peroxide, etc.

Hazard

Lead is probably one of the most widely distributed poisons in the world. Not only is themetal poisonous, but most lead compounds are also extremely toxic when inhaled or ingested.A few, such as lead alkalis, are toxic when absorbed through skin contact.
Workers in industries using lead are subject to testing of their blood and urine to determinethe levels of lead in their bodies’ organs. Great effort is made to keep the workers safe.
Unfortunately, many older homes (built prior to 1950) have several coats of lead-basedpaints that flake off, which then may be ingested by children, causing various degrees of leadpoisoning, including mental retardation or even death.
Young children are more susceptible to an accumulation of lead in their systems than areadults because of their smaller body size and more rapidly growing organs, such as the kidneys,nervous system, and blood-forming organs. Symptoms may include headaches, dizziness,insomnia, and stupor, leading to coma and eventually death.
Lead poisoning can also occur from drinking tap water contained in pipes that have beensoldered with lead-alloy solder. This risk can be reduced by running the tap water until it iscold, which assures a fresher supply of water.
Another hazardous source of lead is pottery that is coated with a lead glaze that is notstabilized. Acidic and hot liquids (citrus fruits, tea, and coffee) react with the lead, and eachuse adds a small amount of ingested lead that can be accumulative. Lead air pollution is stilla problem, but not as great as before, given that tetraethyl lead is no longer used in gasoline.However, lead air pollution remains a problem for those living near lead smelting operationsor in countries where leaded gasoline is still permitted.
Even though lead and many of its compounds are toxic and carcinogenic, our lives wouldbe much less satisfying without its use in our civilization.

Health Hazard

The acute toxicity of lead and inorganic lead compounds is moderate to low. Symptoms of exposure include decreased appetite, insomnia, headache, muscle and joint pain, colic, and constipation. Inorganic lead compounds are not significantly absorbed through the skin.
Chronic exposure to inorganic lead via inhalation or ingestion can result in damage to the peripheral and central nervous system, anemia, and chronic kidney disease. Lead can accumulate in the soft tissues and bones, with the highest accumulation in the liver and kidneys, and elimination is slow. Lead has shown developmental and reproductive toxicity in both male and female animals and humans. Lead is listed by IARC in Group 2B ("possible human carcinogen") and by NTP as "reasonably anticipated to be a carcinogen," but is not considered to be a "select carcinogen" under the criteria of the OSHA Laboratory Standard.

Health Hazard

Toxic routes of exposure to lead are food,water, and air. It is an acute as well as achronic toxicant. The toxic effects depend onthe dose and the nature of the lead salt. Ingestionof lead paint chips is a common causeof lead poisoning among children. Chronictoxic effects may arise from occupationalexposure.
Acute toxic symptoms include ataxia,repeated vomiting, headache, stupor, hallucinations,tremors, convulsions, and coma.Such symptoms are manifested by the encephalopathicsyndrome. Chronic exposure can effects, anemia, and damage to the kidney.Lead can severely affect the nervous system.Chronic lead poisoning adversely affectsthe central and peripheral nervous systems,causing restlessness, irritability, and memoryloss. At lead concentrations of >80μg/dL,encephalopathy can occur. Cerebral edemaneuronal degenerationa and glial proliferationcan occur. The clinical symptoms areataxia, stupor, convulsion, and coma. Epidemiologicstudies in recent years have primarilyfocussed on the neurotoxic effectsof lead on children, especially in terms ofimpaired brain ability and behavioral problems.Permanent brain damage has beennoted among children from lead poisoning.Kidney damage arising from shorttermingestion of lead is reversible: whilea longer-term effect may develop to generaldegradation of the kidney, causing glomularatrophy, interstitial fibrosis, and sclerosisof vessels (Manahan 1989). Inhalation oflead justs can cause gastritis and changes inthe liver. Lead is significantly bioaccumulatedin bones and teeth, where it is storedand released. It binds to a number of cellularligands, interfering with some calciumregulatedfunctions. Lead has an affinity forsulfhydryl groups (-SH), which are presentin many enzymes. Thus it inhibits enzymaticactivity. One such effect is the inhibitionof δ-amino-levulinic acid dehydrates(ALAD) an enzyme required for the biosynthesisof heme, an iron(II)–porphyrin complexin hemoglobin and cytochrome. Anotherenzyme which is also highly susceptible tothe inhibitory effect of lead is heme synthetase.The impaired heme synthesis maycause anemia. The clinical anemia is perceptibleat a blood-lead level of 50 μg/dL. Concentrationsof lead in the blood at levels of10 μg/dL can cause ALAD inhibition. Carcinogenicityof lead has not been observedin humans; the evidence in animals is inadequate.
Suwalsky et al. (2003) studied the effectsof lead on the human erythrocyte membranes using isolated unsealed membranes andmolecular models consisting of bilayers ofdimyristoylphosphatidylcholine and dimyristoylphosphatidylethanolaminerepresentingphospholipids in the outer and inner monolayersof human erithrocyte membrane. Resultsof this study indicated that lead particlesadhered to the external and internal surfacesof human erithrocyte membrane and lead ionsinduced considerable molecular disorder inboth lipid multilayers.
Cremin et al. (1999) investigated the efficacyof chelation of lead with meso-2,3-dimercaptosuccinic acid in reducing the leadlevels in the brain and its neurotoxicity fromchronic oral exposure of the metal in adultrhesus monkeys. Their data, however, indicatedthat under the conditions of their studysuccimer treatment did not reduce brain leadlevels in the primate model and also the limitationsin the use of blood-lead level as anindicator of treatment efficacy.

Fire Hazard

Flash point data for Lead are not available, however, Lead is probably non-combustible.

Flammability and Explosibility

Lead powder is combustible when exposed to heat or flame.

Industrial uses

Not only is lead the most impervious of all common metals to x-rays and gamma radiation, it also resists attack by many corrosive chemicals, most types of soil, and marine and industrial environments. Although lead is one of the heaviest metals, only a few applications are based primarily on its high density. The main reasons for using lead often include low melting temperature, ease of casting and forming, good sound and vibration absorption, and ease of salvaging from scrap.
With its high internal damping characteristics, lead is one of the most efficient sound attenuators for industrial, commercial, and residential applications. Sheet lead, lead-loaded vinyls, lead composites, and lead-containing laminates are used to reduce machinery noise. Lead sheet with asbestos or rubber sandwich pads are commonly used in vibration control.

Industrial uses

lead has been under investigation for use as anticancer and antimicrobial agent, but so far with limited success.
Lead is obtained from its sulfide (PbS, galena), which is first roasted in the presence of oxygen and then reduced with carbon to give elemental Pb.
Lead is a greymetal and most lead is used in batteries.Other major uses, such as in plumbing or as antiknock agent in petrol (tetraethyl lead, Pb(C₂H₅)₄), have declined over recent years because of the high toxicity of lead. Pb is a neurotoxin when ingested and many lead compounds are water soluble. Therefore, water lines have been replaced by specialised plastic material, and in most industrialised countries only unleaded petrol is sold.

Potential Exposure

Tumorigen,Mutagen，Organometallic; Reproductive Effector; HumanData. Metallic lead is used for lining tanks, piping, andother equipment where pliability and corrosion resistance are required, such as in the chemical industry in handlingcorrosive gases and liquids used in the manufacture of sul-furic acid; in petroleum refining; and in halogenation, sulfo-nation，extraction， and condensation processes; and inbuilding industry. It is also used as an ingredient in solder,a body filler in the automobile industry, and a shieldingmaterial for X-rays and atomic radiation, in manufacture oftetraethyl lead and organic and inorganic lead compounds,pigments for paints and varnishes, storage batteries, flingglass, vitreous enameling, ceramics as a glaze, litharge rub-ber, plastics, and electronic devices. Lead is utilized in met-allurgy and may be added to bronze, brass, steel, and otheralloys to improve their characteristics. It forms alloys withantimony, tin, copper, etc. It is also used in metallizing toprov ide protective coatings and as a heat treatment bath inwire drawing. Exposures to lead dust may occur duringmining, smelting, refining, and to fume, during high tem-perature (> 500℃) operations, such as welding or spraycoating of metals with molten lead. There are numerousapplications for lead compounds, some of the more com-mon being in the plates of electric batteries and accumula-tors; as compounding agents irrubber manufacture; asingredients in paints, glazes, enamels, glass, pigments; andin the chemical industry. In addition, to these usual levelsof exposure from environmental media, there exist miscella-neous sources which are hazardous. The level of exposureresulting from contact is highly variable. Children with picafor paint chips or for soil may experience elevation in bloodlead, ranging from marginal to sufficiently great to causeclinical illness. Certain adults may also be exposed to haz-ardous concentrations of lead in the workplace, notably inlead smelters and storage battery manufacturing plants.Again, the range of exposure is highly variable. Women inthe workplace are more likely to ex perience adverse effectsfrom lead exposure than men due to the fact that theirhematopoietic system is more lead-sensitive than men.Because of health concerns, lead from gasoline, paints, andceramic products, caulking, and pipe solder, has been dra-matically reduced in recent years.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irri gate immediately for at least15 min, occasionally lifting upper and lower lids. Seek med-ical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. When this chemical has been swal-lowed, get medical attention.Antidotes and special procedures: Persons with si gnificantlead poisoning are sometimes treated with Ca EDTA whilehospitalized. This “chelating” drug causes a rush of leadfrom the body organs into the blood and kidneys, and thushas its own hazards, and must be administered only byhighly experienced medical personnel under controlled con-ditions and careful observation. Ca EDTA or similar drugsshould never be used to prevent poisoning while exposurecontinues or without strict exposure control, as severe kid-ney damage can result.Note to physician: For severe poisoning BAL [British Anti-Lewisite, dimercaprol, dithiopropanol (C3HgOS2)] has beenused to treat toxic symptoms of certain heavy metals poi-soning. In the case of lead poisoning it may have SOMEvalue. Although BAL is reported to have a large margin ofsafety, caution must be exercised, because toxic effects maybe caused by excessive dosage. Most can be prevented bypremedication with 1-ephedrine sulfate (CAS: 134-72-5).

Carcinogenicity

Lead and lead compounds are reasonably anticipated to be human carcinogens based on limited evidence of carcinogenicity from studies in humans and sufficient evidence of carcinogenicity from studiesin experimental animals.

Environmental Fate

Lead in the earth’s crust is about 15–20 mg kg1. Lead occurs naturally in the environment. However, most of the lead dispersed throughout the environment comes from human activities. Before the use of leaded gasoline was limited, most of the lead released into the US environment came from car exhaust. Because the EPA has limited the use of leaded gasoline, the amount of lead released into the air has decreased. Other sources of lead released into the air include burning fuel, such as coal or oil, industrial processes, and burning solid waste.
The release of lead to air is now less than the release of lead to soil. Most of the lead in inner city soils comes from landfills and leaded paint. Landfills contain waste from lead ore mining, ammunition manufacturing, and other industrial activities such as battery production. Very little lead goes directly into water. Higher levels of lead from car exhausts can be measured near roadways. Very low levels of lead from car exhausts are found at distances of 25m (82 ft) from the road edge. However, once lead goes into the atmosphere, it may travel thousands of miles if the lead particles are small or if the lead compounds are volatile. Lead is removed from the air by rain as well as by particles falling to the ground or into surface water. Once lead deposits on soil, it usually sticks to soil particles. Small amounts of lead may enter rivers, lakes, and streams when soil particles are displaced by rainwater. Lead may remain stuck to soil particles in water for many years. Movement of lead from soil particles into underground water or drinking water is unlikely unless the water is acidic or ‘soft.’ Some of the chemicals that contain lead are broken down by sunlight, air, and water to other forms of lead. Lead compounds in water may combine with different chemicals depending on the acidity and temperature of the water. The lead atom cannot be broken down.
The levels of lead may build up in plants and animals from areas in which air, water, or soil are contaminated with lead. If animals eat contaminated plants or animals, most of the lead they eat will pass through their bodies. The small amount absorbed can cause harmful effects. The amount of lead in paints sold for consumer use may not exceed 0.06%. Releases from lead-based paints are frequently confined to the area in the immediate vicinity of painted surfaces, and deterioration or removal of the paint can result in high localized concentrations of lead in indoor air and on exposed surfaces. Sandblasting procedures to remove paint may disperse lead into the local environment.
The largest volume of organolead vapors released to the atmosphere results from industrial processes such as primary and secondary nonferrous metal smelting, and from the use of leaded gasoline, which contains tetraethyl lead as an antiknock additive. These vapors are photoreactive, and their presence in the local atmosphere is transitory. Halogenated lead compounds are also formed and, ultimately, oxides and carbonates. Tetra-alkyl lead compounds have been found to contribute 5–10% of the total particulate lead present in the atmosphere. Organolead vapors are most likely to occur in occupational settings (e.g., gasoline transport and handling operations, gas stations, and parking garages) and high traffic areas.
Although aquatic releases from industrial facilities are expected to be small, lead may be present in significant levels in drinking water. In areas receiving acid rain (e.g., northeastern United States) the acidity of drinking water may increase, thus increasing the corrosivity of the water, which may, in turn, result in the leaching of lead from water systems, particularly from older systems during the first flush of water through the pipes. Fish in more acidic waters accumulate more lead than fish in a more alkaline environment.
The grounding of household electrical systems to the plumbing can increase corrosion rates and the subsequent leaching of lead from the lead solder used for copper pipes. Areas in which the pH of the water is <8.0 may have higher lead drinking water levels as well.
Canning foods in lead-soldered cans may increase levels of lead 8- to 10-fold; however, the impact of canning appears to be decreasing as a result of a decrease in the use of leadsoldered cans. Additional exposure to lead through dietary intake by people living in an urban environment is estimated to be ～ 28 mg day^-1 for adults and 91mg day^-1 for children, all of which can be attributed to atmospheric lead (dust). Atmospheric lead may be added to food crops in the field or garden (through uptake from soil and from direct deposition onto crop surfaces), during transport to market, processing, and kitchen preparation.
Lead may leach from lead crystal decanters and glasses into the liquids they contain. Flaking paint, paint chips, and weathered powdered paint, which are most commonly associated with deteriorated housing stock in urban areas, are major sources of lead exposure for young children residing in these houses, particularly for children with pica (i.e., the compulsive, habitual consumption of nonfood items). Lead concentrations of 1000–5000 mg cm^-2 have been found in chips of lead-based paint, suggesting that consumption of a single chip of paint would provide greater short-term exposure than any other source of lead.

storage

work with lead dust, molten lead, and lead salts capable of forming dusts should be conducted in a fume hood to prevent exposure by inhalation.

Shipping

For Metal powder, flammable, n.o.s. the requiredlabel is“SPONTANEOUSLY COMBUSTIBLE." They fallinto Hazard Class 4.2 and Packing Group I

Toxicity evaluation

Lead can affect most organs and systems in the body. It can interfere with certain cellular signaling processes, the generation of action potentials in certain nerve cells, and the function of a number of enzymes. Lead interferes with the sodium– potassium ATPase pump on cell membranes, the metabolism of vitamin D, heme synthesis, certain enzymes involved in oxidative phosphorylation (cytochromes), and calcium uptake and metabolism. In addition, lead can interfere with signal transmissions in nerve cells, including dopaminergic transmissions and signaling processes at the postsynaptic and presynaptic junctions. Lead can depress the function of the adrenal glands and the thyroid.
Lead binds certain active groups on protein (e.g., sulfhydryl groups) and therefore may change the structure and function of certain proteins and enzymes. Lead interferes with the biosynthesis of heme in at least two steps in the multi-step process. Heme proteins are important to the structure and function of hemoglobin in red blood cells. Lead binds with 8-aminolevulinic acid dehydratase and depresses its activity. This biochemical block explains the occurrence of anemia found in chronic lead poisoning. Measurement of the blood levels of this enzyme is used as a test for lead intoxication. Lead also interferes with the incorporation of ferrous iron into the porphyrin ring. If iron is not attached to heme, then zinc will occupy the iron-binding site. The concentration of zinc protoporphyrin also can be used as a diagnostic tool for lead poisoning.

Incompatibilities

Violent reactions of lead with sodium azide, zirconium, sodium acetylide, and chlorine trifluoride have been reported. Reactivity of lead compounds varies depending on structure.

Waste Disposal

Excess lead and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines. For more information on disposal procedures, see Chapter 7 of this volume.