Lead

Template:Top icon Template:Use dmy dates Template:Short descriptionTemplate:Template other Template:Redirect-distinguish Lead (Template:IPAc-en) is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal, denser than most common materials. Lead is soft, malleable, and has a relatively low melting point. When freshly cut, it appears shiny gray with a bluish tint, but tarnishes to dull gray on exposure to air. Lead has the highest atomic number of any stable element, and three of its isotopes are endpoints of major nuclear decay chains of heavier elements.

Lead is a relatively unreactive post-transition metal. Its weak metallic character is shown by its amphoteric behavior: lead and lead oxides react with both acids and bases, and it tends to form covalent bonds. Lead compounds usually occur in the +2 oxidation state rather than the +4 state common in lighter members of the carbon group, with exceptions mostly limited to organolead compounds. Like the lighter members of the group, lead can bond with itself, forming chains and polyhedral structures.

Since lead is easily extracted from its ores, prehistoric people in the Near East were aware of it. Galena is a principal ore of lead which often bears silver. Interest in silver helped initiate widespread extraction and use of lead in ancient Rome. Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. Lead played a crucial role in the development of the printing press, as movable type could be relatively easily cast from lead alloys.Template:Sfn In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, plumbing, batteries, bullets, shots (pellets), weights, solders, pewter, fusible alloys, lead paints, leaded gasoline, and radiation shielding.

Lead is a neurotoxin that accumulates in soft tissues and bones. It damages the nervous system, interferes with biological enzymes, and can cause neurological disorders ranging from behavioral problems to brain damage. It also affects cardiovascular and renal systems. Lead's toxicity was noted by ancient Greek and Roman writers, but became widely recognized in Europe in the late 19th century.

Physical properties

Atomic

A lead atom has 82 electrons, with the electron configuration [Xe]4f¹⁴5d¹⁰6s²6p². The combined first and second ionization energies—the total energy required to remove the two 6p electrons—are similar to those of tin, lead's immediate neighbor above in the carbon group. This is unusual, as ionization energies typically decrease down a group due to the outer electrons being farther from the nucleus and more shielded by inner orbitals. However, the sum of the first four ionization energies of lead is higher than that of tin,Template:Sfn contrary to periodic trends. This anomaly is explained by relativistic effects, which become significant in heavier atoms.Template:Sfn These effects contract the s and p orbitals, giving lead's 6s electrons greater binding energies than its 5s electrons.Template:Sfn This leads to the inert-pair effect, where the 6s electrons are less likely to participate in bonding. The result is stabilization of the +2 oxidation state and unusually long distances between nearest atoms in crystalline lead.Template:Sfn

Lighter carbon-group congeners of lead form stable or metastable allotropes with the tetrahedrally coordinated, covalently bonded diamond cubic structure. In these elements, the s- and p-orbital energy levels are close enough to allow mixing into four hybrid sp³ orbitals. In lead, however, the inert pair effect increases the separation between s- and p-orbitals so much that the energy gain from hybridization is insufficient to overcome this gap.Template:Sfn Instead of a diamond cubic arrangement, lead forms metallic bonds in which only the p-electrons are delocalized and shared among Pb²⁺ ions. Consequently, lead adopts a face-centered cubic structure,Template:Sfn similar to theTemplate:Sfn divalent metals calcium and strontium.Template:SfnTemplate:EfnTemplate:EfnTemplate:Efn

Bulk

Pure lead has a bright, shiny gray appearance with a faint blue tint.Template:Sfn It tarnishes when exposed to moist air, developing a dull surface whose color depends on environmental conditions. Lead is characterized by high density, malleability, ductility, and resistance to corrosion due to passivation.Template:Sfn

File:Angeln zubehoer grundblei 01.jpg

Lead fishing weights

Its close-packed face-centered cubic structure and high atomic mass give lead a densityTemplate:Sfn of 11.34 g/cm³, greater than that of common metals such as iron (7.87 g/cm³), copper (8.93 g/cm³), and zinc (7.14 g/cm³).Template:Sfn This high density is the origin of the idiom to go over like a lead balloon.Template:SfnTemplate:SfnTemplate:Efn Some rarer metals are denser: tungsten and gold are both 19.3 g/cm³, while osmium—the densest known metal—has a density of 22.59 g/cm³, nearly twice that of lead.Template:Sfn

Lead is soft, with a Mohs hardness of 1.5, and can be scratched with a fingernail.Template:Sfn It is very malleable and moderately ductile.Template:SfnTemplate:Efn Its bulk modulus—a measure of resistance to compression—is 45.8 GPa, compared with 75.2 GPa for aluminium, 137.8 GPa for copper, and 160–169 GPa for mild steel.Template:Sfn Lead's tensile strength is low, at 12–17 MPa (around six times lower than aluminium, ten times lower than copper, and fifteen times lower than mild steel). Strength can be increased by alloying with small amounts of copper or antimony.Template:Sfn

A disk of metal

A sample of lead solidified from the molten state

Lead melts at 327.5 °C (621.5 °F),Template:Sfn a relatively low melting point compared to most metals,Template:SfnTemplate:Efn and has a boiling point of 1749 °C (3180 °F),Template:Sfn the lowest among the carbon-group elements. Its electrical resistivity at 20 °C is 192 nanoohm-meters, almost an order of magnitude higher than that of good conductors (copper: ; gold: ; aluminium: ).Template:Sfn Lead becomes a superconductor below 7.19 K,Template:Sfn which is the highest critical temperature among type-I superconductors and the third highest among the elemental superconductors.Template:Sfn

Isotopes

Natural lead consists of four stable isotopes with mass numbers 204, 206, 207, and 208,Template:Sfn along with traces of six short-lived radioisotopes with mass numbers 209–214. The relatively high number of isotopes is consistent with lead's even atomic number.Template:Efn Lead has a magic number of protons (82), making its nucleus especially stable according to the nuclear shell model.Template:Sfn Lead-208 also has 126 neutrons, another magic number, which may account for its exceptional stability.Template:Sfn

With its high atomic number, lead is the heaviest element whose natural isotopes are considered stable; lead-208 is the heaviest stable nucleus known. This distinction previously belonged to bismuth (atomic number 83) until its sole primordial isotope, bismuth-209, was found in 2003 to decay extremely slowly.Template:Efn Although the four stable isotopes of lead could theoretically undergo alpha decay to mercury isotopes with an energy release, no such decay has been observed; their predicted half-lives range from 10³⁵ to 10¹⁸⁹ years,Template:Sfn at least 10²⁵ times the current age of the universe.

A piece of a gray meteorite on a pedestal

The Holsinger meteorite, the largest piece of the Canyon Diablo meteorite. Uranium–lead dating and lead–lead dating on this meteorite allowed refinement of the age of the Earth to 4.55 billion ± 70 million years.

Three of lead's stable isotopes—lead-206, lead-207, and lead-208—are the end products of the three major natural decay chains: the uranium chain (from uranium-238), the actinium chain (from uranium-235), and the thorium chain (from thorium-232), respectively.Template:SfnTemplate:Sfn The isotopic composition of a rock sample depends on the presence of these parent isotopes; for example, lead-208 abundance can vary from about 52% in ordinary samples to as much as 90% in thorium ores.Template:Sfn For this reason, the standard atomic weight of lead is reported to only one decimal place.Template:Sfn Over time, the ratios of these isotopes to lead-204 increase as they are produced by radioactive decay. These variations allow for lead–lead and uranium–lead dating.Template:Sfn Lead-207 exhibits nuclear magnetic resonance, a property used to study its compounds in both solution and solid states,Template:SfnTemplate:Sfn including in biological systems such as the human body.Template:Sfn

Chemistry

A flame with a small metal rod penetrating it; the flame near the rod is pale blue.

Flame test: lead colors flame pale blue

When exposed to moist air, bulk lead develops a protective surface layer of variable composition. Lead(II) carbonate is a common constituent,Template:SfnTemplate:SfnTemplate:Sfn and in urban or maritime environments, lead(II) sulfate or lead(II) chloride may also be present.Template:Sfn This layer renders bulk lead effectively inert under atmospheric conditions.Template:Sfn In contrast, finely powdered lead, like many metals, is pyrophoricTemplate:Sfn and burns with a bluish-white flame.Template:Sfn

Lead reacts with fluorine at room temperature to form lead(II) fluoride. Its reaction with chlorine is similar but requires heating, as the resulting chloride layer reduces further reactivity.Template:Sfn Molten lead combines with the chalcogens to produce lead(II) chalcogenides.Template:Sfn

The metal resists attack by sulfuric and phosphoric acids but not by hydrochloric or nitric acids; the difference arises from the insolubility and subsequent passivation of certain lead salts.Template:Sfn Organic acids, such as acetic acid, dissolve lead in the presence of oxygen.Template:Sfn Concentrated alkalis can also dissolve lead, producing plumbites.Template:Sfn

Inorganic compounds

Lead exhibits two principal oxidation states: +4 and +2. While the tetravalent state is characteristic of the carbon group, the divalent state is rare for carbon and silicon, less common for germanium, significant but not dominant for tin, and the most prevalent for lead.Template:Sfn This predominance is linked to relativistic effects—specifically the inert pair effect—which occurs when there is a large electronegativity difference between lead and anions such as oxide, halide, or nitride. In such cases, lead develops a pronounced partial positive charge, causing a stronger contraction of the 6s orbital compared to the 6p orbital and rendering it relatively unreactive in ionic compounds. The inert pair effect is less pronounced in compounds where lead forms covalent bonds with elements of similar electronegativity, such as carbon in organolead compounds. In these, the 6s and 6p orbitals remain comparable in size, and sp³ hybridization remains energetically favorable, making lead predominantly tetravalent in such cases.Template:Sfn

The electronegativity values further reflect this behavior: lead(II) has a value of 1.87, and lead(IV) has 2.33. This represents a reversal in the general trend of increasing stability of the +4 oxidation state down the carbon group; by comparison, tin has electronegativities of 1.80 (+2 state) and 1.96 (+4 state).Template:Sfn

Lead(II)

Cream powder

Lead(II) oxide

Lead(II) compounds are characteristic of the inorganic chemistry of lead. Even strong oxidizing agents like fluorine and chlorine react with lead to give only PbF₂ and PbCl₂.Template:Sfn Lead(II) ions are usually colorless in solution,Template:Sfn and partially hydrolyze to form Pb(OH)⁺ and finally [Pb₄(OH)₄]⁴⁺ (in which the hydroxyl ions act as bridging ligands),Template:SfnTemplate:Sfn but are not reducing agents as tin(II) ions are. Techniques for identifying the presence of the Pb²⁺ ion in water generally rely on the precipitation of lead(II) chloride using dilute hydrochloric acid. As the chloride salt is sparingly soluble in water, in very dilute solutions the precipitation of lead(II) sulfide is instead achieved by bubbling hydrogen sulfide through the solution.Template:Sfn

Lead monoxide exists in two polymorphs, litharge α-PbO (red) and massicot β-PbO (yellow), the latter being stable only above around 488 °C. Litharge is the most commonly used inorganic compound of lead.Template:Sfn There is no lead(II) hydroxide; increasing the pH of solutions of lead(II) salts leads to hydrolysis and condensation.Template:Sfn Lead commonly reacts with heavier chalcogens. Lead sulfide is a semiconductor, a photoconductor, and an extremely sensitive infrared radiation detector. The other two chalcogenides, lead selenide and lead telluride, are likewise photoconducting. They are unusual in that their color becomes lighter going down the group.Template:Sfn

Alternating dark gray and red balls connected by dark gray-red cylinders

Lead and oxygen in a tetragonal unit cell of lead(II,IV) oxide

Lead dihalides are well-characterized; this includes the diastatideTemplate:Sfn and mixed halides, such as PbFCl. The relative insolubility of the latter forms a useful basis for the gravimetric determination of fluorine. The difluoride was the first solid ionically conducting compound to be discovered (in 1834, by Michael Faraday).Template:Sfn The other dihalides decompose on exposure to ultraviolet or visible light, especially the diiodide.Template:Sfn Many lead(II) pseudohalides are known, such as the cyanide, cyanate, and thiocyanate.Template:SfnTemplate:Sfn Lead(II) forms an extensive variety of halide coordination complexes, such as [PbCl₄]²⁻, [PbCl₆]⁴⁻, and the [Pb₂Cl₉]_n⁵ⁿ⁻ chain anion.Template:Sfn

Lead(II) sulfate is insoluble in water, like the sulfates of other heavy divalent cations. Lead(II) nitrate and lead(II) acetate are very soluble, and this is exploited in the synthesis of other lead compounds.Template:Sfn

Lead(IV)

Few inorganic lead(IV) compounds are known. They are only formed in highly oxidizing solutions and do not normally exist under standard conditions.Template:Sfn Lead(II) oxide gives a mixed oxide on further oxidation, Pb₃O₄. It is described as lead(II,IV) oxide, or structurally 2PbO·PbO₂, and is the best-known mixed valence lead compound. Lead dioxide is a strong oxidizing agent, capable of oxidizing hydrochloric acid to chlorine gas.Template:Sfn This is because the expected PbCl₄ that would be produced is unstable and spontaneously decomposes to PbCl₂ and Cl₂.Template:Sfn Analogously to lead monoxide, lead dioxide is capable of forming plumbate anions. Lead disulfideTemplate:Sfn and lead diselenideTemplate:Sfn are only stable at high pressures. Lead tetrafluoride, a yellow crystalline powder, is stable, but less so than the difluoride. Lead tetrachloride (a yellow oil) decomposes at room temperature, lead tetrabromide is less stable still, and the existence of lead tetraiodide is questionable.Template:Sfn

Other oxidation states

Nine dark gray spheres connected by cylinders of the same color forming a convex shape

The capped square antiprismatic anion [Pb₉]⁴⁻ from [K(18-crown-6)]₂K₂Pb₉·(en)_1.5Template:Sfn

Some lead compounds exist in formal oxidation states other than +4 or +2. Lead(III) may be obtained, as an intermediate between lead(II) and lead(IV), in larger organolead complexes; this oxidation state is not stable, as both the lead(III) ion and the larger complexes containing it are radicals.Template:SfnTemplate:SfnTemplate:Sfn The same applies for lead(I), which can be found in such radical species.Template:Sfn

Numerous mixed lead(II,IV) oxides are known. When PbO₂ is heated in air, it becomes Pb₁₂O₁₉ at 293 °C, Pb₁₂O₁₇ at 351 °C, Pb₃O₄ at 374 °C, and finally PbO at 605 °C. A further sesquioxide, Pb₂O₃, can be obtained at high pressure, along with several non-stoichiometric phases. Many of them show defective fluorite structures in which some oxygen atoms are replaced by vacancies: PbO can be considered as having such a structure, with every alternate layer of oxygen atoms absent.Template:Sfn

Negative oxidation states can occur as Zintl phases, as either free lead anions, as in Ba₂Pb, with lead formally being lead(−IV),Template:Sfn or in oxygen-sensitive ring-shaped or polyhedral cluster ions such as the trigonal bipyramidal Pb₅²⁻ ion, where two lead atoms are lead(−I) and three are lead(0).Template:Sfn In such anions, each atom is at a polyhedral vertex and contributes two electrons to each covalent bond along an edge from their sp³ hybrid orbitals, the other two being an external lone pair.Template:Sfn They may be made in liquid ammonia via the reduction of lead by sodium.Template:Sfn

Organolead

A gray-green sphere linked to four black spheres, each, in turn, linked also to three white ones

Structure of a tetraethyllead molecule:
  Carbon
  Hydrogen
  Lead

Lead can form multiply-bonded chains, a property it shares with its lighter homologs in the carbon group. Its capacity to do so is much less because the Pb–Pb bond energy is over three and a half times lower than that of the C–C bond.Template:Sfn With itself, lead can build metal–metal bonds of an order up to three.Template:Sfn With carbon, lead forms organolead compounds similar to, but generally less stable than, typical organic compoundsTemplate:Sfn (due to the Pb–C bond being rather weak).Template:Sfn This makes the organometallic chemistry of lead far less wide-ranging than that of tin.Template:Sfn Lead predominantly forms organolead(IV) compounds, even when starting with inorganic lead(II) reactants; very few organolead(II) compounds are known. The most well-characterized exceptions are Pb[CH(SiMe₃)₂]₂ and plumbocene.Template:Sfn

The lead analog of the simplest organic compound, methane, is plumbane. Plumbane may be obtained in a reaction between metallic lead and atomic hydrogen.Template:Sfn Two simple derivatives, tetramethyllead and tetraethyllead, are the best-known organolead compounds. These compounds are relatively stable: tetraethyllead only starts to decompose if heatedTemplate:Sfn or if exposed to sunlight or ultraviolet light.Template:SfnTemplate:Efn With sodium metal, lead readily forms an equimolar alloy that reacts with alkyl halides to form organometallic compounds such as tetraethyllead.Template:Sfn The oxidizing nature of many organolead compounds is usefully exploited: lead tetraacetate is an important laboratory reagent for oxidation in organic synthesis.Template:Sfn Tetraethyllead, once added to automotive gasoline, was produced in larger quantities than any other organometallic compound,Template:Sfn and is still widely used in fuel for small aircraft. Other organolead compounds are less chemically stable.Template:Sfn For many organic compounds, a lead analog does not exist.Template:Sfn

Origin and occurrence

Solar System abundancesTemplate:Sfn

Atomic number	Element	Relative amount
42	Molybdenum	0.798
46	Palladium	0.440
50	Tin	1.146
78	Platinum	0.417
80	Mercury	0.127
82	Lead	1
90	Thorium	0.011
92	Uranium	0.003

In space

Lead's per-particle abundance in the Solar System is 0.121 ppb (parts per billion).Template:SfnTemplate:Efn This figure is two and a half times higher than that of platinum, eight times more than mercury, and seventeen times more than gold.Template:Sfn The amount of lead in the universe is slowly increasingTemplate:Sfn as most heavier atoms (all of which are unstable) gradually decay to lead.Template:Sfn The abundance of lead in the Solar System since its formation 4.5 billion years ago has increased by about 0.75%.Template:Sfn The Solar System abundances table shows that lead, despite its relatively high atomic number, is more prevalent than most other elements with atomic numbers greater than 40.Template:Sfn

Primordial lead—which comprises the isotopes lead-204, lead-206, lead-207, and lead-208—was mostly created as a result of repetitive neutron capture processes occurring in stars. The two main modes of capture are the s- and r-processes.Template:Sfn

In the s-process (s is for "slow"), captures are separated by years or decades, allowing less stable nuclei to undergo beta decay.Template:Sfn A stable thallium-203 nucleus can capture a neutron and become thallium-204; this undergoes beta decay to give stable lead-204; on capturing another neutron, it becomes lead-205, which has a half-life of around 17 million years. Further captures result in lead-206, lead-207, and lead-208. On capturing another neutron, lead-208 becomes lead-209, which quickly decays into bismuth-209. On capturing another neutron, bismuth-209 becomes bismuth-210, and this beta decays to polonium-210, which alpha decays to lead-206. The cycle hence ends at lead-206, lead-207, lead-208, and bismuth-209.Template:Sfn

Uppermost part of the nuclide chart, with only practically stable isotopes and lead-205 shown, and the path of the s-process overlaid on it as well that of the cycle on lead, bismuth, and polonium

Chart of the final part of the s-process, from mercury to polonium. Red lines and circles represent neutron captures; blue arrows represent beta decays; the green arrow represents an alpha decay; cyan arrows represent electron captures.

In the r-process (r is for "rapid"), captures happen faster than nuclei can decay.Template:Sfn This occurs in environments with a high neutron density, such as a supernova or the merger of two neutron stars. The neutron flux involved may be on the order of 10²² neutrons per square centimeter per second.Template:Sfn The r-process does not form as much lead as the s-process.Template:Sfn It tends to stop once neutron-rich nuclei reach 126 neutrons.Template:Sfn At this point, the neutrons are arranged in complete shells in the atomic nucleus, and it becomes harder to energetically accommodate more of them.Template:Sfn When the neutron flux subsides, these nuclei beta decay into stable isotopes of osmium, iridium, platinum.Template:Sfn

On Earth

File:Lingot de plomb de l'époque romaine. Mines de Cartagène Espagne.jpg

Lead ingot from Roman times, Cartagena, Spain

Lead is classified as a chalcophile under the Goldschmidt classification, meaning it is generally found combined with sulfur.Template:Sfn It rarely occurs in its native, metallic form.Template:Sfn Many lead minerals are relatively light and, over the course of the Earth's history, have remained in the crust instead of sinking deeper into the Earth's interior. This accounts for lead's relatively high crustal abundance of 14 ppm; it is the 36th most abundant element in the crust.Template:SfnTemplate:Efn

The main lead-bearing mineral is galena (PbS), which is mostly found with zinc ores.Template:Sfn Most other lead minerals are related to galena in some way; boulangerite, Pb₅Sb₄S₁₁, is a mixed sulfide derived from galena; anglesite, PbSO₄, is a product of galena oxidation; and cerussite or white lead ore, PbCO₃, is a decomposition product of galena. Arsenic, tin, antimony, silver, gold, copper, bismuth are common impurities in lead minerals.Template:Sfn

A line chart generally declining towards its right

Lead is a fairly common element in the Earth's crust for its high atomic number (82). Most elements of atomic number greater than 40 are less abundant.

World lead resources exceed two billion tons. Significant deposits are located in Australia, China, Ireland, Mexico, Peru, Portugal, Russia, United States. Global reserves—resources that are economically feasible to extract—totaled 88 million tons in 2016, of which Australia had 35 million, China 17 million, Russia 6.4 million.Template:Sfn

Typical background concentrations of lead do not exceed 0.1 μg/m³ in the atmosphere; 100 mg/kg in soil; 4 mg/kg in vegetation, 5 μg/L in fresh water and seawater.Template:Sfn

Etymology

The modern English word lead is of Germanic origin; it comes from the Middle English and Old English (with the macron above the "e" signifying that the vowel sound of that letter is long).Template:Sfn The Old English word is derived from the hypothetical reconstructed Proto-Germanic ('lead').Template:Sfn According to linguistic theory, this word bore descendants in multiple Germanic languages of exactly the same meaning.Template:Sfn

There is no consensus on the origin of the Proto-Germanic . One hypothesis suggests it is derived from Proto-Indo-European ('lead'; capitalization of the vowel is equivalent to the macron).Template:Sfn Another hypothesis suggests it is borrowed from Proto-Celtic ('lead'). This word is related to the Latin , which gave the element its chemical symbol Pb. The word is thought to be the origin of Proto-Germanic (which also means 'lead'), from which stemmed the German .Template:Sfn

The name of the chemical element is not related to the verb of the same spelling, which is derived from Proto-Germanic ('to lead').Template:Sfn

History

Prehistory and early history

A line chart generally growing to its right

World lead production peaking in the Roman period and the Industrial RevolutionTemplate:Sfn

Metallic lead beads dating back to 7000–6500 BC have been found in Asia Minor and may represent the first example of metal smelting.Template:Sfn At that time, lead had few (if any) applications due to its softness and dull appearance.Template:Sfn The major reason for the spread of lead production was its association with silver, which may be obtained by burning galena (a common lead mineral).Template:Sfn The Ancient Egyptians were the first to use lead minerals in cosmetics, an application that spread to Ancient Greece and beyond;Template:Sfn the Egyptians had used lead for sinkers in fishing nets, glazes, glasses, enamels, ornaments.Template:Sfn Various civilizations of the Fertile Crescent used lead as a writing material, as coins,Template:Sfn and as a construction material.Template:Sfn Lead was used by the ancient Chinese as a stimulant,Template:Sfn as currency,Template:Sfn as contraceptive,Template:Sfn and in chopsticks.Template:Sfn The Indus Valley civilization and the Mesoamericans used it for making amulets;Template:Sfn and the eastern and southern Africans used lead in wire drawing.Template:Sfn

Classical era

Because silver was extensively used as a decorative material and an exchange medium, lead deposits came to be worked in Asia Minor from 3000 BC; later, lead deposits were developed in the Aegean and Laurion.Template:Sfn These three regions collectively dominated production of mined lead until c. Template:Trim.Template:Sfn Beginning c. 2000 BC, the Phoenicians worked deposits in the Iberian peninsula; by 1600 BC, lead mining existed in Cyprus, Greece, and Sardinia.Template:Sfn

File:Sling bullets BM GR1842.7-28.550 GR1851.5-7.11.jpg

Ancient Greek lead sling bullets with a winged thunderbolt molded on one side and the inscription ("take that") on the other sideTemplate:Sfn

Rome's territorial expansion in Europe and across the Mediterranean, and its development of mining, led to it becoming the greatest producer of lead during the classical era, with an estimated annual output peaking at 80,000 tonnes. Like their predecessors, the Romans obtained lead mostly as a by-product of silver smelting.Template:SfnTemplate:Sfn Lead mining occurred in central Europe, Britain, Balkans, Greece, Anatolia, Hispania, the latter accounting for 40% of world production.Template:Sfn

A vaguely round plate illuminated from a side to increase the contrast. The characters curl around the contour.

The Lead Plaque of Magliano, Italy, bears an Etruscan inscription from mid-5th century BC.

Lead tablets were commonly used as a material for letters.Template:Sfn Lead coffins, cast in flat sand forms and with interchangeable motifs to suit the faith of the deceased, were used in ancient Judea.Template:Sfn Lead was used to make sling bullets from the 5th century BC. In Roman times, lead sling bullets were amply used, and were effective at a distance of between 100 and 150 meters. The Balearic slingers, used as mercenaries in Carthaginian and Roman armies, were famous for their shooting distance and accuracy.Template:Sfn

Ancient pipes in a museum case

Roman lead pipesTemplate:Efn

Lead was used for making water pipes in the Roman Empire; the Latin word for the metal, , is the origin of the English word "plumbing". Its ease of working, its low melting point enabling the easy fabrication of completely waterproof welded joints, and its resistance to corrosionTemplate:Sfn ensured its widespread use in other applications, including pharmaceuticals, roofing, currency, warfare.Template:SfnTemplate:SfnTemplate:Sfn Writers of the time, such as Cato the Elder, Columella, and Pliny the Elder, recommended lead (and lead-coated) vessels for the preparation of sweeteners and preservatives added to wine and food. The lead conferred an agreeable taste due to the formation of "sugar of lead" (lead(II) acetate), whereas copper vessels imparted a bitter flavor through verdigris formation.Template:Sfn

This metal was by far the most used material in classical antiquity, and it is appropriate to refer to the (Roman) Lead Age. Lead was to the Romans what plastic is to us.

Heinz Eschnauer and Markus Stoeppler
"Wine—An enological specimen bank", 1992Template:Sfn

The Roman author Vitruvius reported the health dangers of leadTemplate:Sfn and modern writers have suggested that lead poisoning played a major role in the decline of the Roman Empire.Template:SfnTemplate:SfnTemplate:Efn Other researchers have criticized such claims, pointing out, for instance, that not all abdominal pain is caused by lead poisoning.Template:SfnTemplate:Sfn According to archaeological research, Roman lead pipes increased lead levels in tap water but such an effect was "unlikely to have been truly harmful".Template:SfnTemplate:Sfn When lead poisoning did occur, victims were called "saturnine", dark and cynical, after the ghoulish father of the gods, Saturn. By association, lead was considered the father of all metals.Template:Sfn Its status in Roman society was low as it was readily availableTemplate:Sfn and cheap.Template:Sfn

Confusion with tin and antimony

Since the Bronze Age, metallurgists and engineers have understood the difference between rare and valuable tin, essential for alloying with copper to produce tough and corrosion resistant bronze, and 'cheap and cheerful' lead. However, the nomenclature in some languages is similar. Romans called lead ("black lead"), and tin ("bright lead"). The association of lead and tin can be seen in other languages: the word in Czech translates to "lead", but in Russian, its cognate () means "tin".Template:Sfn To add to the confusion, lead bore a close relation to antimony: both elements commonly occur as sulfides (galena and stibnite), often together. Pliny incorrectly wrote that stibnite would give lead on heating, instead of antimony.Template:Sfn In countries such as Turkey and India, the originally Persian name (Template:Langx) came to refer to either antimony sulfide or lead sulfide,Template:Sfn and in some languages, such as Russian, gave its name to antimony ().Template:Sfn

Middle Ages and the Renaissance

A white-faced woman in red clothes

Elizabeth I of England was commonly depicted with a whitened face. Lead in face whiteners is thought to have contributed to her death.Template:Sfn

Lead mining in Western Europe declined after the fall of the Western Roman Empire, with Al-Andalus being the only region having a significant output.Template:SfnTemplate:Sfn The largest production of lead occurred in South Asia and East Asia, especially China and India, where lead mining grew rapidly.Template:Sfn

In Europe, lead production began to increase in the 11th and 12th centuries, when it was again used for roofing and piping. Starting in the 13th century, lead was used to create stained glass.Template:Sfn In the European and Muslim traditions of alchemy, lead (symbol ♄ in the European tradition)Template:Sfn was considered an impure base metal which, by the separation, purification and balancing of its constituent essences, could be transformed to pure and incorruptible gold.Template:Sfn During the period, lead was used increasingly for adulterating wine. The use of such wine was forbidden for use in Christian rites by a papal bull in 1498, but it continued to be imbibed and resulted in mass poisonings up to the late 18th century.Template:SfnTemplate:Sfn Lead was a key material in parts of the printing press, and lead dust was commonly inhaled by print workers, causing lead poisoning.Template:Sfn Lead also became the chief material for making bullets for firearms: it was cheap, less damaging to iron gun barrels, had a higher density (which allowed for better retention of velocity), and its lower melting point made the production of bullets easier as they could be made using a wood fire.Template:Sfn Lead, in the form of Venetian ceruse, was extensively used in cosmetics by Western European aristocracy as whitened faces were regarded as a sign of modesty.Template:SfnTemplate:Sfn This practice later expanded to white wigs and eyeliners, and only faded out with the French Revolution in the late 18th century. A similar fashion appeared in Japan in the 18th century with the emergence of the geishas, a practice that continued long into the 20th century. The white faces of women "came to represent their feminine virtue as Japanese women",Template:Sfn with lead commonly used in the whitener.Template:Sfn

Outside Europe and Asia

In the New World, lead production was recorded soon after the arrival of European settlers. The earliest record dates to 1621 in the English Colony of Virginia, fourteen years after its foundation.Template:Sfn In Australia, the first mine opened by colonists on the continent was a lead mine, in 1841.Template:Sfn In Africa, lead mining and smelting were known in the Benue TroughTemplate:Sfn and the lower Congo Basin, where lead was used for trade with Europeans, and as a currency by the 17th century,Template:Sfn well before the scramble for Africa.

Industrial Revolution

A black-and-white drawing of men working in a mine

Lead mining in the upper Mississippi River region in the United States in 1865

In the second half of the 18th century, Britain, and later continental Europe and the United States, experienced the Industrial Revolution. This was the first time during which lead production rates exceeded those of Rome.Template:Sfn Britain was the leading producer, losing this status by the mid-19th century with the depletion of its mines and the development of lead mining in Germany, Spain, and the United States.Template:Sfn By 1900, the United States was the leader in global lead production, and other non-European nations—Canada, Mexico, and Australia—had begun significant production; production outside Europe exceeded that within.Template:Sfn A great share of the demand for lead came from plumbing and painting—lead paints were in regular use.Template:Sfn At this time, more (working class) people were exposed to the metal and lead poisoning cases escalated. This led to research into the effects of lead intake. Lead was proven to be more dangerous in its fume form than as a solid metal. Lead poisoning and gout were linked; British physician Alfred Baring Garrod noted a third of his gout patients were plumbers and painters. The effects of chronic ingestion of lead, including mental disorders, were also studied in the 19th century. The first laws aimed at decreasing lead poisoning in factories were enacted during the 1870s and 1880s in the United Kingdom.Template:Sfn

Modern era

A promotional poster for "COLLIER White Lead" (these words are highlighted) featuring a large image of a boy

Promotional poster for Dutch Boy lead paint, United States, 1912

Further evidence of the threat that lead posed to humans was discovered in the late 19th and early 20th centuries. Mechanisms of harm were better understood, lead blindness was documented, and the element was phased out of public use in the United States and Europe. The United Kingdom introduced mandatory factory inspections in 1878 and appointed the first Medical Inspector of Factories in 1898; as a result, a 25-fold decrease in lead poisoning incidents from 1900 to 1944 was reported.Template:Sfn Most European countries banned lead paint—commonly used because of its opacity and water resistanceTemplate:Sfn—for interiors by 1930.Template:Sfn

The last major human exposure to lead was the addition of tetraethyllead to gasoline as an antiknock agent, a practice that originated in the United States in 1921. It was phased out in the United States and the European Union by 2000.Template:Sfn

In the 1970s, the United States and Western European countries introduced legislation to reduce lead air pollution.Template:SfnTemplate:Sfn The impact was significant: while a study conducted by the Centers for Disease Control and Prevention in the United States in 1976–1980 showed that 77.8% of the population had elevated blood lead levels, in 1991–1994, a study by the same institute showed the share of people with such high levels dropped to 2.2%.Template:Sfn The main product made of lead by the end of the 20th century was the lead–acid battery.Template:Sfn

From 1960 to 1990, lead output in the Western Bloc grew by about 31%.Template:Sfn The share of the world's lead production by the Eastern Bloc increased from 10% to 30%, from 1950 to 1990, with the Soviet Union being the world's largest producer during the mid-1970s and the 1980s, and China starting major lead production in the late 20th century.Template:Sfn Unlike the European communist countries, China was largely unindustrialized by the mid-20th century; in 2004, China surpassed Australia as the largest producer of lead.Template:Sfn As was the case during European industrialization, lead has had a negative effect on health in China.Template:Sfn

Production

A line chart of many lines, some longer than other, most generally growing towards its right

Primary production of lead since 1840

As of 2014, production of lead is increasing worldwide due to its use in lead–acid batteries.Template:Sfn There are two major categories of production: primary from mined ores, and secondary from scrap. In 2014, 4.58 million metric tons came from primary production and 5.64 million from secondary production. The top three producers of mined lead concentrate in that year were China, Australia, and United States.Template:Sfn The top three producers of refined lead were China, United States, and India.Template:Sfn According to the Metal Stocks in Society report of 2010, the total amount of lead in use, stockpiled, discarded, or dissipated into the environment, on a global basis, is 8 kg per capita. Much of this is in more developed countries (20–150 kg per capita) rather than less developed ones (1–4 kg per capita).Template:Sfn

The primary and secondary lead production processes are similar. Some primary production plants now supplement their operations with scrap lead, and this trend is likely to increase in the future. Given adequate techniques, lead obtained via secondary processes is indistinguishable from lead obtained via primary processes. Scrap lead from the building trade is usually fairly clean and is re-melted without the need for smelting, though refining is sometimes needed. Secondary lead production is therefore cheaper, in terms of energy requirements, than is primary production, often by 50% or more.Template:Sfn

Primary

Most lead ores contain a low percentage of lead (rich ores have a typical content of 3–8%) which must be concentrated for extraction.Template:Sfn During initial processing, ores typically undergo crushing, dense-medium separation, grinding, froth flotation, drying. The resulting concentrate, which has a lead content of 30–80% by mass (regularly 50–60%),Template:Sfn is then turned into (impure) lead metal.

There are two main ways of doing this: a two-stage process involving roasting followed by blast furnace extraction, carried out in separate vessels; or a direct process in which the extraction of the concentrate occurs in a single vessel. The latter has become the most common route, though the former is still significant.Template:Sfn

Two-stage process

First, the sulfide concentrate is roasted in air to oxidize the lead sulfide:Template:Sfn

2 PbS(s) + 3 O₂(g) → 2 PbO(s) + 2 SO₂(g)↑

As the original concentrate was not pure lead sulfide, roasting yields not only the desired lead(II) oxide, but a mixture of oxides, sulfates, and silicates of lead and of the other metals contained in the ore.Template:Sfn This impure lead oxide is reduced in a coke-fired blast furnace to the (again, impure) metal:Template:Sfn

2 PbO(s) + C(s) → 2 Pb(s) + CO₂(g)↑

Impurities are mostly arsenic, antimony, bismuth, zinc, copper, silver, and gold. Typically they are removed in a series of pyrometallurgical processes. The melt is treated in a reverberatory furnace with air, steam, sulfur, which oxidizes the impurities except for silver, gold, bismuth. Oxidized contaminants float to the top of the melt and are skimmed off.Template:SfnTemplate:Sfn Metallic silver and gold are removed and recovered economically by means of the Parkes process, in which zinc is added to lead. Zinc, which is immiscible in lead, dissolves the silver and gold. The zinc solution can be separated from the lead, and the silver and gold retrieved.Template:SfnTemplate:Sfn De-silvered lead is freed of bismuth by the Betterton–Kroll process, treating it with metallic calcium and magnesium. The resulting bismuth dross can be skimmed off.Template:Sfn

Alternatively to the pyrometallurgical processes, very pure lead can be obtained by processing smelted lead electrolytically using the Betts process. Anodes of impure lead and cathodes of pure lead are placed in an electrolyte of lead fluorosilicate (PbSiF₆). Once electrical potential is applied, impure lead at the anode dissolves and plates onto the cathode, leaving the majority of the impurities in solution.Template:SfnTemplate:Sfn This is a high-cost process and thus mostly reserved for refining bullion containing high percentages of impurities.Template:Sfn

Direct process

In this process, lead bullion and slag is obtained directly from lead concentrates. The lead sulfide concentrate is melted in a furnace and oxidized, forming lead monoxide. Carbon (as coke or coal gasTemplate:Efn) is added to the molten charge along with fluxing agents. The lead monoxide is thereby reduced to metallic lead, in the midst of a slag rich in lead monoxide.Template:Sfn

If the input is rich in lead, as much as 80% of the original lead can be obtained as bullion; the remaining 20% forms a slag rich in lead monoxide. For a low-grade feed, all of the lead can be oxidized to a high-lead slag.Template:Sfn Metallic lead is further obtained from the high-lead (25–40%) slags via submerged fuel combustion or injection, reduction assisted by an electric furnace, or a combination of both.Template:Sfn

Alternatives

Research on a cleaner, less energy-intensive lead extraction process continues; a major drawback is that either too much lead is lost as waste, or the alternatives result in a high sulfur content in the resulting lead metal. Hydrometallurgical extraction, in which anodes of impure lead are immersed into an electrolyte and pure lead is deposited (electrowound) onto cathodes, is a technique that may have potential, but is not currently economical except in cases where electricity is very cheap.Template:Sfn

Secondary

Smelting, which is an essential part of the primary production, is often skipped during secondary production. It is only performed when metallic lead has undergone significant oxidation.Template:Sfn The process is similar to that of primary production in either a blast furnace or a rotary furnace, with the essential difference being the greater variability of yields: blast furnaces produce hard lead (10% antimony) while reverberatory and rotary kiln furnaces produce semisoft lead (3–4% antimony).Template:Sfn

The ISASMELT process is a more recent smelting method that may act as an extension to primary production; battery paste from spent lead–acid batteries (containing lead sulfate and lead oxides) has its sulfate removed by treating it with alkali, and is then treated in a coal-fueled furnace in the presence of oxygen, which yields impure lead, with antimony the most common impurity.Template:Sfn Refining of secondary lead is similar to that of primary lead; some refining processes may be skipped depending on the material recycled and its potential contamination.Template:Sfn

Of the sources of lead for recycling, lead–acid batteries are the most important; lead pipe, sheet, and cable sheathing are also significant.Template:Sfn

Applications

A closed structure of black bricks

Bricks of lead (alloyed with 4% antimony) are used as radiation shielding.Template:Sfn

Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. When the pencil originated as a wrapped graphite writing tool, the particular type of graphite used was named plumbago (literally, lead mockup).Template:Sfn

Elemental form

Lead metal has several useful mechanical properties, including high density, low melting point, ductility, and relative inertness. Many metals are superior to lead in some of these aspects but are generally less common and more difficult to extract from parent ores. Lead's toxicity has led to its phasing out for some uses.Template:Sfn

Lead was used to cover the ramparts protecting the ascent to the Alamut Castle in Persia, which could absorb attacks by siege engines.

Lead has been used for bullets since their invention in the Middle Ages. It is inexpensive; its low melting point means small arms ammunition and shotgun pellets can be cast with minimal technical equipment; and it is denser than other common metals, which allows for better retention of velocity. It remains the main material for bullets, alloyed with other metals as hardeners.Template:Sfn Concerns have been raised that lead bullets used for hunting can damage the environment.Template:Efn Shotgun cartridges used for waterfowl hunting must today be lead-free in the United States, Canada, and in Europe.

Lead's high density and resistance to corrosion have been exploited in a number of related applications. It is used as ballast in sailboat keels; its density allows it to take up a small volume and minimize water resistance, thus counterbalancing the heeling effect of wind on the sails.Template:Sfn It is used in scuba diving weight belts to counteract the diver's buoyancy.Template:Sfn In 1993, the base of the Leaning Tower of Pisa was stabilized with 600 tonnes of lead.Template:Sfn Because of its corrosion resistance, lead is used as a protective sheath for underwater cables.Template:Sfn

Yellow sculpture

A 17th-century gold-coated lead sculpture

Lead has many uses in the construction industry; lead sheets are used as architectural metals in roofing material, cladding, flashing, gutters and gutter joints, roof parapets.Template:SfnTemplate:Sfn Lead is still used in statues and sculptures,Template:Efn including for armatures.Template:Sfn In the past it was often used to balance the wheels of cars; for environmental reasons this use is being phased out in favor of other materials.Template:Sfn

Lead is added to copper alloys, such as brass and bronze, to improve machinability and for its lubricating qualities. Being practically insoluble in copper, the lead forms solid globules in imperfections throughout the alloy, such as grain boundaries. In low concentrations, as well as acting as a lubricant, the globules hinder the formation of swarf as the alloy is worked, thereby improving machinability. Copper alloys with larger concentrations of lead are used in bearings. The lead provides lubrication, and the copper provides the load-bearing support.Template:Sfn

Lead's high density, atomic number, and formability form the basis for use of lead as a barrier that absorbs sound, vibration, and radiation.Template:Sfn Lead has no natural resonance frequencies;Template:Sfn as a result, sheet-lead is used as a sound deadening layer in the walls, floors, and ceilings of sound studios.Template:Sfn Organ pipes are often made from a lead alloy, mixed with various amounts of tin to control the tone of each pipe.Template:SfnTemplate:Sfn Lead is an established shielding material from radiation in nuclear science and in X-ray roomsTemplate:Sfn due to its denseness and high attenuation coefficient.Template:Sfn Molten lead has been used as a coolant for lead-cooled fast reactors.Template:Sfn

Batteries

The largest use of lead in the early 21st century is in lead–acid batteries. The lead in batteries undergoes no direct contact with humans, so there are fewer toxicity concerns.Template:Efn People who work in lead battery production or recycling plants may be exposed to lead dust and inhale it.Template:Sfn The reactions in the battery between lead, lead dioxide, and sulfuric acid provide a reliable source of voltage.Template:Efn Supercapacitors incorporating lead–acid batteries have been installed in kilowatt and megawatt scale applications in Australia, Japan, and the United States in frequency regulation, solar smoothing and shifting, wind smoothing, and other applications.Template:Sfn These batteries have lower energy density and charge-discharge efficiency than lithium-ion batteries, but are significantly cheaper.Template:Sfn

Coating for cables

Lead is used in high voltage power cables as shell material to prevent water diffusion into insulation; this use is decreasing as lead is being phased out.Template:Sfn Its use in solder for electronics is also being phased out by some countries to reduce the amount of environmentally hazardous waste.Template:Sfn Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, acidic gases.Template:SfnTemplate:Sfn

Compounds

A crystal glass

Lead glass

File:PbCrO4 and PbCrO4•PbO.jpg

Lead yellow and lead red

In addition to being the main application for lead metal, lead–acid batteries are also the main consumer of lead compounds. The energy storage/release reaction used in these devices involves lead sulfate and lead dioxide:

Template:Chem/link(s) + Template:Chem/link(s) + 2Template:Chem/link(aq) → 2Template:Chem/link(s) + 2Template:Chem/link(l)

Other applications of lead compounds are very specialized and often fading. Lead-based coloring agents are used in ceramic glazes and glass, especially for red and yellow shades.Template:Sfn While lead paints are phased out in Europe and North America, they remain in use in less developed countries such as China,Template:Sfn India,Template:Sfn or Indonesia.Template:Sfn Lead tetraacetate and lead dioxide are used as oxidizing agents in organic chemistry. Lead is frequently used in the polyvinyl chloride coating of electrical cords.Template:SfnTemplate:Sfn It can be used to treat candle wicks to ensure a longer, more even burn. Because of its toxicity, European and North American manufacturers use alternatives such as zinc.Template:SfnTemplate:Sfn Lead glass is composed of 12–28% lead oxide, changing its optical characteristics and reducing the transmission of ionizing radiation,Template:Sfn a property used in old TVs and computer monitors with cathode-ray tubes. Lead-based semiconductors such as lead telluride and lead selenide are used in photovoltaic cells and infrared detectors.Template:Sfn

Biological effects

Template:Chembox HazardsTemplate:Chembox Datapage checkTemplate:Yesno

Lead

Lead has no confirmed biological role, and there is no confirmed safe level of lead exposure.Template:Sfn A 2009 Canadian–American study concluded that even at levels that are considered to pose little to no risk, lead may cause "adverse mental health outcomes".Template:Sfn Its prevalence in the human body—at an adult average of 120 mgTemplate:Efn—is nevertheless exceeded only by zinc (2500 mg) and iron (4000 mg) among the heavy metals.Template:Sfn Lead salts are very efficiently absorbed by the body.Template:Sfn A small amount of lead (1%) is stored in bones; the rest is excreted in urine and feces within a few weeks of exposure. Only about a third of lead is excreted by a child. Continual exposure may result in the bioaccumulation of lead.Template:Sfn

Toxicity

Lead is a highly poisonous metal (whether inhaled or swallowed), affecting almost every organ and system in the human body.Template:Sfn At airborne levels of 100 mg/m³, it is immediately dangerous to life and health.Template:Sfn Most ingested lead is absorbed into the bloodstream.Template:Sfn The primary cause of its toxicity is its predilection for interfering with the proper functioning of enzymes. It does so by binding to the sulfhydryl groups found on many enzymes,Template:Sfn or mimicking and displacing other metals that act as cofactors in many enzymatic reactions.Template:Sfn The essential metals that lead interacts with include calcium, iron, and zinc.Template:Sfn High levels of calcium and iron tend to provide some protection from lead poisoning; low levels cause increased susceptibility.Template:Sfn

Effects

Lead can cause severe damage to the brain and kidneys and, ultimately, death. By mimicking calcium, lead can cross the blood–brain barrier. It degrades the myelin sheaths of neurons, reduces their numbers, interferes with neurotransmission routes, and decreases neuronal growth.Template:Sfn 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 microcytic anemia.Template:Sfn

A chart of a human body with arrows pointing pieces of text to different parts of the body

Symptoms of lead poisoning

Symptoms of lead poisoning include nephropathy, colic-like abdominal pains, and possibly weakness in the fingers, wrists, or ankles. Small blood pressure increases, particularly in middle-aged and older people, may be apparent and can cause anemia. Several studies, mostly cross-sectional, found an association between increased lead exposure and decreased heart rate variability.Template:Sfn In pregnant women, high levels of exposure to lead may cause miscarriage. Chronic, high-level exposure has been shown to reduce fertility in males.Template:Sfn

In a child's developing brain, lead interferes with synapse formation in the cerebral cortex, neurochemical development (including that of neurotransmitters), and the organization of ion channels.Template:Sfn Early childhood exposure has been linked with an increased risk of sleep disturbances and excessive daytime drowsiness in later childhood.Template:Sfn High blood levels are associated with delayed puberty in girls.Template:Sfn The rise and fall in exposure to airborne lead from the combustion of tetraethyl lead in gasoline during the 20th century has been linked with historical increases and decreases in crime levels.

Exposure sources

Lead exposure is a global issue since lead mining and smelting, and battery manufacturing, disposal, and recycling, are common in many countries. Lead enters the body via inhalation, ingestion, or skin absorption. Almost all inhaled lead is absorbed into the body; for ingestion, the rate is 20–70%, with children absorbing a higher percentage than adults.Template:Sfn

Poisoning typically results from ingestion of food or water contaminated with lead, and less commonly after accidental ingestion of contaminated soil, dust, or lead-based paint.Template:Sfn Seawater products can contain lead if affected by nearby industrial waters.Template:Sfn Fruit and vegetables can be contaminated by high levels of lead in the soils they were grown in. Soil can be contaminated through particulate accumulation from lead in pipes, lead paint, residual emissions from leaded gasoline.Template:Sfn

The use of lead for water pipes is a problem in areas with soft or acidic water.Template:Sfn Hard water forms insoluble protective layers on the inner surface of the pipes, whereas soft and acidic water dissolves the lead pipes.Template:Sfn Dissolved carbon dioxide in the carried water may result in the formation of soluble lead bicarbonate; oxygenated water may similarly dissolve lead as lead(II) hydroxide. Drinking such water, over time, can cause health problems due to the toxicity of the dissolved lead. The harder the water the more calcium bicarbonate and sulfate it contains, and the more the inside of the pipes are coated with a protective layer of lead carbonate or lead sulfate.Template:Sfn

File:Kymographic recording of the effect of lead on frog heart..jpg

Kymographic recording of the effect of lead acetate on frog heart experimental set up

Ingestion of applied lead-based paint is the major source of exposure for children: a direct source is chewing on old painted window sills. Additionally, as lead paint on a surface deteriorates, it peels and is pulverized into dust. The dust then enters the body through hand-to-mouth contact or contaminated food or drink. Ingesting certain home remedies may result in exposure to lead or its compounds.Template:Sfn

Inhalation is the second major exposure pathway, affecting smokers and especially workers in lead-related occupations.Template:Sfn Cigarette smoke contains, among other toxic substances, radioactive lead-210.Template:Sfn "As a result of EPA's regulatory efforts, levels of lead in the air [in the United States] decreased by 86 percent between 2010 and 2020." The concentration of lead in the air in the United States fell below the national standard of 0.15 μg/m³ in 2014.

Skin exposure may be significant for people working with organic lead compounds. The rate of skin absorption is lower for inorganic lead.Template:Sfn

Lead in foods

Lead may be found in food when food is grown in soil that is high in lead, airborne lead contaminates the crops, animals eat lead in their diet, or lead enters the food either from what it was stored or cooked in. Ingestion of lead paint and batteries is also a route of exposure for livestock, which can subsequently affect humans. Milk produced by contaminated cattle can be diluted to a lower lead concentration and sold for consumption.

In Bangladesh, lead compounds have been added to turmeric to make it more yellow. This is believed to have started in the 1980s and continues since 2019Template:Dated maintenance category (articles). It is believed to be one of the main sources of high lead levels in the country. In Hong Kong the maximum allowed lead level in food is 6 parts per million in solids and 1 part per million in liquids.

Lead-containing dust can settle on drying cocoa beans when they are set outside near polluting industrial plants. In December 2022, Consumer Reports tested 28 dark chocolate brands and found that 23 of them contained potentially harmful levels of lead, cadmium or both. They have urged the chocolate makers to reduce the level of lead which could be harmful, especially to a developing fetus.

In March 2024, the US Food and Drug Administration recommended a voluntary recall on 6 brands of cinnamon due to contamination with lead, after 500 reports of child lead poisoning. The FDA determined that cinnamon was adulterated with lead chromate.

Lead in plastic toys

According to the United States Center for Disease Control, the use of lead in plastics has not been banned as of 2024. Lead softens the plastic and makes it more flexible so that it can go back to its original shape. Habitual chewing on colored plastic insulation from stripped electrical wires was found to cause elevated lead levels in a 46-year-old man. Lead may be used in plastic toys to stabilize molecules from heat. Lead dust can be formed when plastic is exposed to sunlight, air, and detergents that break down the chemical bond between the lead and plastics.

Treatment

Treatment for lead poisoning normally involves the administration of dimercaprol and succimer.Template:Sfn Acute cases may require the use of disodium calcium edetate, the calcium chelate, and the disodium salt of ethylenediaminetetraacetic acid (EDTA). It has a greater affinity for lead than calcium, with the result that lead chelate is formed by exchange and excreted in the urine, leaving behind harmless calcium.Template:Sfn

Environmental effects

A dusty dump

Battery collection site in Dakar, Senegal, where at least 18 children died of lead poisoning in 2008

The extraction, production, use, and disposal of lead and its products have caused significant contamination of the Earth's soils and waters. Atmospheric emissions of lead were at their peak during the Industrial Revolution, and the leaded gasoline period in the second half of the twentieth century.Template:Sfn

Lead releases originate from natural sources (i.e., concentration of the naturally occurring lead), industrial production, incineration and recycling, and mobilization of previously buried lead.Template:Sfn In particular, as lead has been phased out from other uses, in the Global South, lead recycling operations designed to extract cheap lead used for global manufacturing have become a well documented source of exposure.Template:Sfn Elevated concentrations of lead persist in soils and sediments in post-industrial and urban areas; industrial emissions, including those arising from coal burning,Template:Sfn continue in many parts of the world, particularly in the developing countries.Template:Sfn

Lead can accumulate in soils, especially those with a high organic content, where it remains for hundreds to thousands of years. Environmental lead can compete with other metals found in and on plant surfaces potentially inhibiting photosynthesis and at high enough concentrations, negatively affecting plant growth and survival. Contamination of soils and plants can allow lead to ascend the food chain affecting microorganisms and animals. In animals, lead exhibits toxicity in many organs, damaging the nervous, renal, reproductive, hematopoietic, and cardiovascular systems after ingestion, inhalation, or skin absorption.Template:Sfn Fish uptake lead from both water and sediment;Template:Sfn bioaccumulation in the food chain poses a hazard to fish, birds, and sea mammals.Template:Sfn

Anthropogenic lead includes lead from shot and sinkers. These are among the most potent sources of lead contamination along with lead production sites.Template:Sfn Lead was banned for shot and sinkers in the United States in 2017,Template:Sfn although that ban was only effective for a month,Template:Sfn and a similar ban is being considered in the European Union.Template:Sfn

Analytical methods for the determination of lead in the environment include spectrophotometry, X-ray fluorescence, atomic spectroscopy, and electrochemical methods. A specific ion-selective electrode has been developed based on the ionophore S,S'-methylenebis(N,N-diisobutyldithiocarbamate).Template:Sfn An important biomarker assay for lead poisoning is δ-aminolevulinic acid levels in plasma, serum, and urine.Template:Sfn

Restriction and remediation

An X-ray picture with numerous small pellets highlighted in white

Radiography of a swan found dead in Condé-sur-l'Escaut (northern France), highlighting lead shot. There are hundreds of lead pellets (a dozen is enough to kill an adult swan within a few days). Such bodies are sources of environmental contamination by lead.

By the mid-1980s, there was significant decline in the use of lead in industry. In the United States, environmental regulations reduced or eliminated the use of lead in non-battery products, including gasoline, paints, solders, and water systems. Particulate control devices were installed in coal-fired power plants to capture lead emissions.Template:Sfn In 1992, U.S. Congress required the Environmental Protection Agency to reduce the blood lead levels of the country's children.Template:Sfn Lead use was further curtailed by the European Union's 2003 Restriction of Hazardous Substances Directive.Template:Sfn A large drop in lead deposition occurred in the Netherlands after the 1993 national ban on use of lead shot for hunting and sport shooting: from 230 tonnes in 1990 to 47.5 tonnes in 1995.Template:Sfn The usage of lead in Avgas 100LL for general aviation is allowed in the EU as of 2022.

In the United States, the permissible exposure limit for lead in the workplace, comprising metallic lead, inorganic lead compounds, and lead soaps, was set at 50 μg/m³ over an 8-hour workday, and the blood lead level limit at 5 μg per 100 g of blood in 2012.Template:Sfn Lead may still be found in harmful quantities in stoneware,Template:Sfn vinylTemplate:Sfn (such as that used for tubing and the insulation of electrical cords), and Chinese brass.Template:Efn Old houses may still contain lead paint.Template:Sfn White lead paint has been withdrawn from sale in industrialized countries, but specialized uses of other pigments such as yellow lead chromate remain,Template:Sfn especially in road pavement marking paint. Stripping old paint by sanding produces dust which can be inhaled.Template:Sfn Lead abatement programs have been mandated by some authorities in properties where young children live.Template:Sfn The usage of lead in Avgas 100LL for general aviation is generally allowed in United States as of 2023.

Lead waste, depending on the jurisdiction and the nature of the waste, may be treated as household waste (to facilitate lead abatement activities),Template:Sfn or potentially hazardous waste requiring specialized treatment or storage.Template:Sfn Lead is released into the environment in shooting places and a number of lead management practices have been developed to counter the lead contamination.Template:Sfn Lead migration can be enhanced in acidic soils; to counter that, it is advised soils be treated with lime to neutralize the soils and prevent leaching of lead.Template:Sfn

Research has been conducted on how to remove lead from biosystems by biological means: Fish bones are being researched for their ability to bioremediate lead in contaminated soil.Template:SfnTemplate:Sfn The fungus Aspergillus versicolor is effective at absorbing lead ions from industrial waste before being released to water bodies.Template:Sfn Several bacteria have been researched for their ability to remove lead from the environment, including the sulfate-reducing bacteria Desulfovibrio and Desulfotomaculum, both of which are highly effective in aqueous solutions.Template:Sfn Millet grass Urochloa ramosa has the ability to accumulate significant amounts of metals such as lead and zinc in its shoot and root tissues making it an important plant for remediation of contaminated soils.

See also

• Derek Bryce-Smith – one of the earliest campaigners against lead in petrol in the UK
• Thomas Midgley Jr. – discovered that the addition of tetraethyllead to gasoline prevented "knocking" in internal combustion engines
• Clair Cameron Patterson – instrumental in the banning of tetraethyllead in gasoline in the US and lead solder in food cans.
• Robert A. Kehoe – foremost medical advocate for the use of tetraethyllead as an additive in gasoline.

Bibliography

• Template:CIAAW2016

Further reading

• Table of contents
• Ingalls, Walter Renton (1865-), Lead Smelting and Refining, With Some Notes on Lead Mining

External links

• The Toxicology of Heavy Metals: Getting the Lead Out, American Society for Clinical Pathology
• usgs.gov: Lead (Mineral Commodity Summaries 2025)