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Lead

Lead is a chemical element with the symbol Pb (from the Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed 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 toxic, even in small amounts, especially to children.

Lead, 82Pb
Lead
Pronunciation/ˈlɛd/ (led)
Appearancemetallic gray
Standard atomic weight Ar°(Pb)
  • [206.14207.94]
  • 207.2±1.1 (abridged)[1]
Lead in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Sn

Pb

Fl
thalliumleadbismuth
Atomic number (Z)82
Groupgroup 14 (carbon group)
Periodperiod 6
Block  p-block
Electron configuration[Xe] 4f14 5d10 6s2 6p2
Electrons per shell2, 8, 18, 32, 18, 4
Physical properties
Phase at STPsolid
Melting point600.61 K ​(327.46 °C, ​621.43 °F)
Boiling point2022 K ​(1749 °C, ​3180 °F)
Density (near r.t.)11.34 g/cm3
when liquid (at m.p.)10.66 g/cm3
Heat of fusion4.77 kJ/mol
Heat of vaporization179.5 kJ/mol
Molar heat capacity26.650 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 978 1088 1229 1412 1660 2027
Atomic properties
Oxidation states−4, −2, −1, 0,[2] +1, +2, +3, +4 (an amphoteric oxide)
ElectronegativityPauling scale: 2.33 (in +4), 1.87 (in +2)
Ionization energies
  • 1st: 715.6 kJ/mol
  • 2nd: 1450.5 kJ/mol
  • 3rd: 3081.5 kJ/mol
Atomic radiusempirical: 175 pm
Covalent radius146±5 pm
Van der Waals radius202 pm
Spectral lines of lead
Other properties
Natural occurrenceprimordial
Crystal structureface-centered cubic (fcc)

a=495.08 pm
Speed of sound thin rod1190 m/s (at r.t.) (annealed)
Thermal expansion28.9 µm/(m⋅K) (at 25 °C)
Thermal conductivity35.3 W/(m⋅K)
Electrical resistivity208 nΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic
Molar magnetic susceptibility−23.0×10−6 cm3/mol (at 298 K)[3]
Young's modulus16 GPa
Shear modulus5.6 GPa
Bulk modulus46 GPa
Poisson ratio0.44
Mohs hardness1.5
Brinell hardness38–50 MPa
CAS Number7439-92-1
History
DiscoveryMiddle East (7000 BCE)
Symbol"Pb": from Latin plumbum
Isotopes of lead
Main isotopes[4] Decay
abun­dance half-life (t1/2) mode pro­duct
202Pb synth 5.25×104 y ε 202Tl
204Pb 1.40% stable
205Pb trace 1.73×107 y ε 205Tl
206Pb 24.1% stable
207Pb 22.1% stable
208Pb 52.4% stable
209Pb trace 3.253 h β 209Bi
210Pb trace 22.20 y β 210Bi
211Pb trace 36.1 min β 211Bi
212Pb trace 10.64 h β 212Bi
214Pb trace 26.8 min β 214Bi
Isotopic abundances vary greatly by sample[5]
 Category: Lead
| references

Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself; it can form 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.[6] 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 and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding.

Lead's toxicity became widely recognized in the late 19th century, although a number of well-educated ancient Greek and Roman writers were aware of this fact and even knew some of the symptoms of lead poisoning. Lead is a neurotoxin that accumulates in soft tissues and bones; it damages the nervous system and interferes with the function of biological enzymes, causing neurological disorders ranging from behavioral problems to brain damage, and also affects general health, cardiovascular, and renal systems.

Physical properties

Atomic

A lead atom has 82 electrons, arranged in an electron configuration of [Xe]4f145d106s26p2. The sum of lead's first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, lead's upper neighbor in the carbon group. This is unusual; ionization energies generally fall going down a group, as an element's outer electrons become more distant from the nucleus, and more shielded by smaller orbitals.

The sum of the first four ionization energies of lead exceeds that of tin,[7] contrary to what periodic trends would predict. This is explained by relativistic effects, which become significant in heavier atoms,[8] which contract s and p orbitals such that lead's 6s electrons have larger binding energies than its 5s electrons.[9] A consequence is the so-called inert pair effect: the 6s electrons of lead become reluctant to participate in bonding, stabilising the +2 oxidation state and making the distance between nearest atoms in crystalline lead unusually long.[10]

Lead's lighter carbon group congeners form stable or metastable allotropes with the tetrahedrally coordinated and covalently bonded diamond cubic structure. The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp3 orbitals. In lead, the inert pair effect increases the separation between its s- and p-orbitals, and the gap cannot be overcome by the energy that would be released by extra bonds following hybridization.[11] Rather than having a diamond cubic structure, lead forms metallic bonds in which only the p-electrons are delocalized and shared between the Pb2+ ions. Lead consequently has a face-centered cubic structure[12] like the similarly sized[13] divalent metals calcium and strontium.[14][a][b][c]

Bulk

Pure lead has a bright, shiny gray appearance with a hint of blue.[19] It tarnishes on contact with moist air and takes on a dull appearance, the hue of which depends on the prevailing conditions. Characteristic properties of lead include high density, malleability, ductility, and high resistance to corrosion due to passivation.[20]

 
A sample of lead solidified from the molten state

Lead's close-packed face-centered cubic structure and high atomic weight result in a density[21] of 11.34 g/cm3, which is greater than that of common metals such as iron (7.87 g/cm3), copper (8.93 g/cm3), and zinc (7.14 g/cm3).[22] This density is the origin of the idiom to go over like a lead balloon.[23][24][d] Some rarer metals are denser: tungsten and gold are both at 19.3 g/cm3, and osmium—the densest metal known—has a density of 22.59 g/cm3, almost twice that of lead.[25]

Lead is a very soft metal with a Mohs hardness of 1.5; it can be scratched with a fingernail.[26] It is quite malleable and somewhat ductile.[27][e] The bulk modulus of lead—a measure of its ease of compressibility—is 45.8 GPa. In comparison, that of aluminium is 75.2 GPa; copper 137.8 GPa; and mild steel 160–169 GPa.[28] Lead's tensile strength, at 12–17 MPa, is low (that of aluminium is 6 times higher, copper 10 times, and mild steel 15 times higher); it can be strengthened by adding small amounts of copper or antimony.[29]

The melting point of lead—at 327.5 °C (621.5 °F)[30]—is very low compared to most metals.[21][f] Its boiling point of 1749 °C (3180 °F)[30] is the lowest among the carbon group elements. The electrical resistivity of lead at 20 °C is 192 nanoohm-meters, almost an order of magnitude higher than those of other industrial metals (copper at 15.43 nΩ·m; gold 20.51 nΩ·m; and aluminium at 24.15 nΩ·m).[32] Lead is a superconductor at temperatures lower than 7.19 K;[33] this is the highest critical temperature of all type-I superconductors and the third highest of the elemental superconductors.[34]

Isotopes

Natural lead consists of four stable isotopes with mass numbers of 204, 206, 207, and 208,[35] and traces of five short-lived radioisotopes.[36] The high number of isotopes is consistent with lead's atomic number being even.[g] Lead has a magic number of protons (82), for which the nuclear shell model accurately predicts an especially stable nucleus.[37] Lead-208 has 126 neutrons, another magic number, which may explain why lead-208 is extraordinarily stable.[37]

With its high atomic number, lead is the heaviest element whose natural isotopes are regarded as stable; lead-208 is the heaviest stable nucleus. (This distinction formerly fell to bismuth, with an atomic number of 83, until its only primordial isotope, bismuth-209, was found in 2003 to decay very slowly.)[h] The four stable isotopes of lead could theoretically undergo alpha decay to isotopes of mercury with a release of energy, but this has not been observed for any of them; their predicted half-lives range from 1035 to 10189 years[40] (at least 1025 times the current age of the universe).

Three of the stable isotopes are found in three of the four major decay chains: lead-206, lead-207, and lead-208 are the final decay products of uranium-238, uranium-235, and thorium-232, respectively.[41] These decay chains are called the uranium chain, the actinium chain, and the thorium chain.[42] Their isotopic concentrations in a natural rock sample depends greatly on the presence of these three parent uranium and thorium isotopes. For example, the relative abundance of lead-208 can range from 52% in normal samples to 90% in thorium ores;[43] for this reason, the standard atomic weight of lead is given to only one decimal place.[44] As time passes, the ratio of lead-206 and lead-207 to lead-204 increases, since the former two are supplemented by radioactive decay of heavier elements while the latter is not; this allows for lead–lead dating. As uranium decays into lead, their relative amounts change; this is the basis for uranium–lead dating.[45] Lead-207 exhibits nuclear magnetic resonance, a property that has been used to study its compounds in solution and solid state,[46][47] including in the human body.[48]

 
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.

Apart from the stable isotopes, which make up almost all lead that exists naturally, there are trace quantities of a few radioactive isotopes. One of them is lead-210; although it has a half-life of only 22.2 years,[35] small quantities occur in nature because lead-210 is produced by a long decay series that starts with uranium-238 (that has been present for billions of years on Earth). Lead-211, −212, and −214 are present in the decay chains of uranium-235, thorium-232, and uranium-238, respectively, so traces of all three of these lead isotopes are found naturally. Minute traces of lead-209 arise from the very rare cluster decay of radium-223, one of the daughter products of natural uranium-235, and the decay chain of neptunium-237, traces of which are produced by neutron capture in uranium ores. Lead-210 is particularly useful for helping to identify the ages of samples by measuring its ratio to lead-206 (both isotopes are present in a single decay chain).[49]

In total, 43 lead isotopes have been synthesized, with mass numbers 178–220.[35] Lead-205 is the most stable radioisotope, with a half-life of around 1.73×107 years.[i] The second-most stable is lead-202, which has a half-life of about 52,500 years, longer than any of the natural trace radioisotopes.[35]

Chemistry

 
Flame test: lead colors flame pale blue

Bulk lead exposed to moist air forms a protective layer of varying composition. Lead(II) carbonate is a common constituent;[51][52][53] the sulfate or chloride may also be present in urban or maritime settings.[54] This layer makes bulk lead effectively chemically inert in the air.[54] Finely powdered lead, as with many metals, is pyrophoric,[55] and burns with a bluish-white flame.[56]

Fluorine reacts with lead at room temperature, forming lead(II) fluoride. The reaction with chlorine is similar but requires heating, as the resulting chloride layer diminishes the reactivity of the elements.[54] Molten lead reacts with the chalcogens to give lead(II) chalcogenides.[57]

Lead metal resists sulfuric and phosphoric acid but not hydrochloric or nitric acid; the outcome depends on insolubility and subsequent passivation of the product salt.[58] Organic acids, such as acetic acid, dissolve lead in the presence of oxygen.[54] Concentrated alkalis will dissolve lead and form plumbites.[59]

Inorganic compounds

Lead shows two main oxidation states: +4 and +2. The tetravalent state is common for the carbon group. The divalent state is rare for carbon and silicon, minor for germanium, important (but not prevailing) for tin, and is the more important of the two oxidation states for lead.[54] This is attributable to relativistic effects, specifically the inert pair effect, which manifests itself when there is a large difference in electronegativity between lead and oxide, halide, or nitride anions, leading to a significant partial positive charge on lead. The result is a stronger contraction of the lead 6s orbital than is the case for the 6p orbital, making it rather inert in ionic compounds. The inert pair effect is less applicable to compounds in which lead forms covalent bonds with elements of similar electronegativity, such as carbon in organolead compounds. In these, the 6s and 6p orbitals remain similarly sized and sp3 hybridization is still energetically favorable. Lead, like carbon, is predominantly tetravalent in such compounds.[60]

There is a relatively large difference in the electronegativity of lead(II) at 1.87 and lead(IV) at 2.33. This difference marks the reversal in the trend of increasing stability of the +4 oxidation state going down the carbon group; tin, by comparison, has values of 1.80 in the +2 oxidation state and 1.96 in the +4 state.[61]

Lead(II)

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.[54] Lead(II) ions are usually colorless in solution,[62] and partially hydrolyze to form Pb(OH)+ and finally [Pb4(OH)4]4+ (in which the hydroxyl ions act as bridging ligands),[63][64] 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.[65]

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.[66] There is no lead(II) hydroxide; increasing the pH of solutions of lead(II) salts leads to hydrolysis and condensation.[67] 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.[68]

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

Lead dihalides are well-characterized; this includes the diastatide[69] 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).[70] The other dihalides decompose on exposure to ultraviolet or visible light, especially the diiodide.[71] Many lead(II) pseudohalides are known, such as the cyanide, cyanate, and thiocyanate.[68][72] Lead(II) forms an extensive variety of halide coordination complexes, such as [PbCl4]2−, [PbCl6]4−, and the [Pb2Cl9]n5n chain anion.[71]

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.[73]

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.[74] 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.[75] This is because the expected PbCl4 that would be produced is unstable and spontaneously decomposes to PbCl2 and Cl2.[76] Analogously to lead monoxide, lead dioxide is capable of forming plumbate anions. Lead disulfide[77] and lead diselenide[78] 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.[79]

Other oxidation states

 
The capped square antiprismatic anion [Pb9]4− from [K(18-crown-6)]2K2Pb9·(en)1.5[80]

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.[81][82][83] The same applies for lead(I), which can be found in such radical species.[84]

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.[85]

Negative oxidation states can occur as Zintl phases, as either free lead anions, as in Ba2Pb, with lead formally being lead(−IV),[86] 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).[87] 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.[63] They may be made in liquid ammonia via the reduction of lead by sodium.[88]

Organolead

 
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.[57] With itself, lead can build metal–metal bonds of an order up to three.[89] With carbon, lead forms organolead compounds similar to, but generally less stable than, typical organic compounds[90] (due to the Pb–C bond being rather weak).[63] This makes the organometallic chemistry of lead far less wide-ranging than that of tin.[91] 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 Pb(η5-C5H5)2.[91]

The lead analog of the simplest organic compound, methane, is plumbane. Plumbane may be obtained in a reaction between metallic lead and atomic hydrogen.[92] Two simple derivatives, tetramethyllead and tetraethyllead, are the best-known organolead compounds. These compounds are relatively stable: tetraethyllead only starts to decompose if heated[93] or if exposed to sunlight or ultraviolet light.[94][j] With sodium metal, lead readily forms an equimolar alloy that reacts with alkyl halides to form organometallic compounds such as tetraethyllead.[95] The oxidizing nature of many organolead compounds is usefully exploited: lead tetraacetate is an important laboratory reagent for oxidation in organic synthesis.[96] Tetraethyllead, once added to gasoline, was produced in larger quantities than any other organometallic compound.[91] Other organolead compounds are less chemically stable.[90] For many organic compounds, a lead analog does not exist.[92]

Origin and occurrence

Solar System abundances[97]
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).[97][k] This figure is two and a half times higher than that of platinum, eight times more than mercury, and seventeen times more than gold.[97] The amount of lead in the universe is slowly increasing[98] as most heavier atoms (all of which are unstable) gradually decay to lead.[99] The abundance of lead in the Solar System since its formation 4.5 billion years ago has increased by about 0.75%.[100] 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.[97]

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.[101]

In the s-process (s is for "slow"), captures are separated by years or decades, allowing less stable nuclei to undergo beta decay.[102] 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 15 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. Bismuth-209 is also radioactive and eventually decays into thallium-205 if left unperturbed. 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 thallium-205.[103]

 
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.[104] 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.[105] The r-process does not form as much lead as the s-process.[106] It tends to stop once neutron-rich nuclei reach 126 neutrons.[107] At this point, the neutrons are arranged in complete shells in the atomic nucleus, and it becomes harder to energetically accommodate more of them.[108] When the neutron flux subsides, these nuclei beta decay into stable isotopes of osmium, iridium, and platinum.[109]

On Earth

Lead is classified as a chalcophile under the Goldschmidt classification, meaning it is generally found combined with sulfur.[110] It rarely occurs in its native, metallic form.[111] 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 38th most abundant element in the crust.[112][l]

The main lead-bearing mineral is galena (PbS), which is mostly found with zinc ores.[114] 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, and bismuth are common impurities in lead minerals.[114]

 
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, and the 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, and Russia 6.4 million.[115]

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 and 5 μg/L in freshwater and seawater.[116]

Etymology

The modern English word lead is of Germanic origin; it comes from the Middle English leed and Old English lēad (with the macron above the "e" signifying that the vowel sound of that letter is long).[117] The Old English word is derived from the hypothetical reconstructed Proto-Germanic *lauda- ('lead').[118] According to linguistic theory, this word bore descendants in multiple Germanic languages of exactly the same meaning.[118]

There is no consensus on the origin of the Proto-Germanic *lauda-. One hypothesis suggests it is derived from Proto-Indo-European *lAudh- ('lead'; capitalization of the vowel is equivalent to the macron).[119] Another hypothesis suggests it is borrowed from Proto-Celtic *ɸloud-io- ('lead'). This word is related to the Latin plumbum, which gave the element its chemical symbol Pb. The word *ɸloud-io- is thought to be the origin of Proto-Germanic *bliwa- (which also means 'lead'), from which stemmed the German Blei.[120]

The name of the chemical element is not related to the verb of the same spelling, which is derived from Proto-Germanic *laidijan- ('to lead').[121]

History

Prehistory and early history

 
World lead production peaking in the Roman period and the Industrial Revolution.[122]

Metallic lead beads dating back to 7000–6500 BCE have been found in Asia Minor and may represent the first example of metal smelting.[123] At that time lead had few (if any) applications due to its softness and dull appearance.[123] 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).[124] The Ancient Egyptians were the first to use lead minerals in cosmetics, an application that spread to Ancient Greece and beyond;[125] the Egyptians may have used lead for sinkers in fishing nets, glazes, glasses, enamels, and for ornaments.[124] Various civilizations of the Fertile Crescent used lead as a writing material, as coins,[126] and as a construction material.[124] Lead was used in the Ancient Chinese royal court as a stimulant,[124] as currency,[127] and as a contraceptive;[128] the Indus Valley civilization and the Mesoamericans[124] used it for making amulets; and the eastern and southern African peoples used lead in wire drawing.[129]

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 BCE; later, lead deposits were developed in the Aegean and Laurion.[130] These three regions collectively dominated production of mined lead until c. 1200 BCE.[131] Beginning circa 2000 BCE, the Phoenicians worked deposits in the Iberian peninsula; by 1600 BCE, lead mining existed in Cyprus, Greece, and Sardinia.[132]

 
Ancient Greek lead sling bullets with a winged thunderbolt molded on one side and the inscription "ΔΕΞΑΙ" ("take that" or "catch") on the other side.[133]

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.[122][134] Lead mining occurred in Central Europe, Britain, the Balkans, Greece, Anatolia, and Hispania, the latter accounting for 40% of world production.[122]

Lead tablets were commonly used as a material for letters.[135] Lead coffins, cast in flat sand forms, with interchangeable motifs to suit the faith of the deceased were used in ancient Judea.[136] 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.[137]

 
Roman lead pipes[m]

Lead was used for making water pipes in the Roman Empire; the Latin word for the metal, plumbum, 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 corrosion[138] ensured its widespread use in other applications, including pharmaceuticals, roofing, currency, and warfare.[139][140][141] Writers of the time, such as Cato the Elder, Columella, and Pliny the Elder, recommended lead (or 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 or bronze vessels could impart a bitter flavor through verdigris formation.[142]

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", 1992[143]

The Roman author Vitruvius reported the health dangers of lead[144][145] and modern writers have suggested that lead poisoning played a major role in the decline of the Roman Empire.[146][147][n] Other researchers have criticized such claims, pointing out, for instance, that not all abdominal pain is caused by lead poisoning.[149][150] According to archaeological research, Roman lead pipes increased lead levels in tap water but such an effect was "unlikely to have been truly harmful".[151][152] 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.[153] Its status in Roman society was low as it was readily available[154] and cheap.[155]

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 plumbum nigrum ("black lead"), and tin plumbum candidum ("bright lead"). The association of lead and tin can be seen in other languages: the word olovo in Czech translates to "lead", but in Russian, its cognate олово (olovo) means "tin".[156] 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.[157] In countries such as Turkey and India, the originally Persian name surma came to refer to either antimony sulfide or lead sulfide,[158] and in some languages, such as Russian, gave its name to antimony (сурьма).[159]

Middle Ages and the Renaissance

 
Elizabeth I of England was commonly depicted with a whitened face. Lead in face whiteners is thought to have contributed to her death.[160]

Lead mining in Western Europe declined after the fall of the Western Roman Empire, with Arabian Iberia being the only region having a significant output.[161][162] The largest production of lead occurred in South and East Asia, especially China and India, where lead mining grew rapidly.[162]

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.[163] In the European and Arabian traditions of alchemy, lead (symbol ♄ in the European tradition)[164] 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.[165] 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.[161][166] Lead was a key material in parts of the printing press, and lead dust was commonly inhaled by print workers, causing lead poisoning.[167] 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.[168] 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.[169][170] 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",[171] with lead commonly used in the whitener.[172]

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.[173] In Australia, the first mine opened by colonists on the continent was a lead mine, in 1841.[174] In Africa, lead mining and smelting were known in the Benue Trough[175] and the lower Congo Basin, where lead was used for trade with Europeans, and as a currency by the 17th century,[176] well before the scramble for Africa.

Industrial Revolution

 
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.[177] 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.[178] 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.[179] A great share of the demand for lead came from plumbing and painting—lead paints were in regular use.[180] 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.[180]

Modern era

 
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.[181] Most European countries banned lead paint—commonly used because of its opacity and water resistance[182]—for interiors by 1930.[183]

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.[180]

In the 1970s, the United States and Western European countries introduced legislation to reduce lead air pollution.[184][185] 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%.[186] The main product made of lead by the end of the 20th century was the lead–acid battery.[187]

From 1960 to 1990, lead output in the Western Bloc grew by about 31%.[188] 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.[189] 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.[190] As was the case during European industrialization, lead has had a negative effect on health in China.[191]

Production

 
Primary production of lead since 1840

As of 2014, production of lead is increasing worldwide due to its use in lead–acid batteries.[192] 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 the United States.[115] The top three producers of refined lead were China, the United States, and India.[193] According to the International Resource Panel's 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).[194]

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.[195]

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.[196] During initial processing, ores typically undergo crushing, dense-medium separation, grinding, froth flotation, and drying. The resulting concentrate, which has a lead content of 30–80% by mass (regularly 50–60%),[196] 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.[197]

World's largest mining countries of lead, 2016[115]
Country Output
(thousand
tons)
  China 2,400
  Australia 500
  United States 335
  Peru 310
  Mexico 250
  Russia 225
  India 135
  Bolivia 80
  Sweden 76
  Turkey 75
  Iran 41
  Kazakhstan 41
  Poland 40
  South Africa 40
  North Korea 35
  Ireland 33
  North Macedonia 33
Other countries 170

Two-stage process

First, the sulfide concentrate is roasted in air to oxidize the lead sulfide:[198]

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.[199] This impure lead oxide is reduced in a coke-fired blast furnace to the (again, impure) metal:[200]

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, and sulfur, which oxidizes the impurities except for silver, gold, and bismuth. Oxidized contaminants float to the top of the melt and are skimmed off.[201][202] 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.[202][203] 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.[202]

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.[202][204] This is a high-cost process and thus mostly reserved for refining bullion containing high percentages of impurities.[205]

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 gas[o]) 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.[197]

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.[197] 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.[197]

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 a cathode, is a technique that may have potential, but is not currently economical except in cases where electricity is very cheap.[206]

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.[195] 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 produced semisoft lead (3–4% antimony).[207]

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.[208] 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.[208]

Of the sources of lead for recycling, lead–acid batteries are the most important; lead pipe, sheet, and cable sheathing are also significant.[195]

Applications

 
Bricks of lead (alloyed with 4% antimony) are used as radiation shielding.[209]

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, act for lead or lead mockup).[210]

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.[211]

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.[168] Concerns have been raised that lead bullets used for hunting can damage the environment.[p]

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.[213] It is used in scuba diving weight belts to counteract the diver's buoyancy.[214] In 1993, the base of the Leaning Tower of Pisa was stabilized with 600 tonnes of lead.[215] Because of its corrosion resistance, lead is used as a protective sheath for underwater cables.[216]

 
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, and on roof parapets.[217][218] Lead is still used in statues and sculptures,[q] including for armatures.[220] 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.[115]

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.[221]

Lead's high density, atomic number, and formability form the basis for use of lead as a barrier that absorbs sound, vibration, and radiation.[222] Lead has no natural resonance frequencies;[222] as a result, sheet-lead is used as a sound deadening layer in the walls, floors, and ceilings of sound studios.[223] Organ pipes are often made from a lead alloy, mixed with various amounts of tin to control the tone of each pipe.[224][225] Lead is an established shielding material from radiation in nuclear science and in X-ray rooms[226] due to its denseness and high attenuation coefficient.[227] Molten lead has been used as a coolant for lead-cooled fast reactors.[228]

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.[r] People who work in lead battery production plants may be exposed to lead dust and inhale it.[230] The reactions in the battery between lead, lead dioxide, and sulfuric acid provide a reliable source of voltage.[s] 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.[232] These batteries have lower energy density and charge-discharge efficiency than lithium-ion batteries, but are significantly cheaper.[233]

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.[234] Its use in solder for electronics is also being phased out by some countries to reduce the amount of environmentally hazardous waste.[235] Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, and acidic gases.[236][237]

Compounds

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:

Pb(s) + PbO
2
(s) + 2H
2
SO
4
(aq) → 2PbSO
4
(s) + 2H
2
O
(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.[238] While lead paints are phased out in Europe and North America, they remain in use in less developed countries such as China,[239] India,[240] or Indonesia.[241] 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.[242][243] 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.[244][245] Lead glass is composed of 12–28% lead oxide, changing its optical characteristics and reducing the transmission of ionizing radiation,[246] 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.[247]

Biological effects

Lead
Hazards
GHS labelling:
   
Danger
H302, H332, H351, H360Df, H373, H410
P201, P261, P273, P304, P308, P312, P313, P340, P391[248]
NFPA 704 (fire diamond)
2
0
0

Lead has no confirmed biological role, and there is no confirmed safe level of lead exposure.[249] 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".[250] Its prevalence in the human body—at an adult average of 120 mg[t]—is nevertheless exceeded only by zinc (2500 mg) and iron (4000 mg) among the heavy metals.[252] Lead salts are very efficiently absorbed by the body.[253] 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.[254]

Toxicity

Lead is a highly poisonous metal (whether inhaled or swallowed), affecting almost every organ and system in the human body.[255] At airborne levels of 100 mg/m3, it is immediately dangerous to life and health.[256] Most ingested lead is absorbed into the bloodstream.[257] 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,[258] or mimicking and displacing other metals which act as cofactors in many enzymatic reactions.[259] The essential metals that lead interacts with include calcium, iron, and zinc.[260] High levels of calcium and iron tend to provide some protection from lead poisoning; low levels cause increased susceptibility.[253]

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.[258] 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.[261]

 
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.[citation needed] Several studies, mostly cross-sectional, found an association between increased lead exposure and decreased heart rate variability.[262] In pregnant women, high levels of exposure to lead may cause miscarriage. Chronic, high-level exposure has been shown to reduce fertility in males.[263]

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.[264] Early childhood exposure has been linked with an increased risk of sleep disturbances and excessive daytime drowsiness in later childhood.[265] High blood levels are associated with delayed puberty in girls.[266] 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.[267]

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.[268] Seawater products can contain lead if affected by nearby industrial waters.[269] 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, and residual emissions from leaded gasoline.[270]

The use of lead for water pipes is a problem in areas with soft or acidic water.[271] Hard water forms insoluble protective layers on the inner surface of the pipes, whereas soft and acidic water dissolves the lead pipes.[272] 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 will contain, and the more the inside of the pipes will be coated with a protective layer of lead carbonate or lead sulfate.[273]

 
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. Alternatively, as the applied dry paint deteriorates, it peels, is pulverized into dust and then enters the body through hand-to-mouth contact or contaminated food, water, or alcohol. Ingesting certain home remedies may result in exposure to lead or its compounds.[274]

Inhalation is the second major exposure pathway, affecting smokers and especially workers in lead-related occupations.[257] Cigarette smoke contains, among other toxic substances, radioactive lead-210.[275] "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."[276] The concentration of lead in the air in the United States fell below the national standard of 0.15 μg/m3[277] in 2014.[278]

Skin exposure may be significant for people working with organic lead compounds. The rate of skin absorption is lower for inorganic lead.[279]

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.[280] Ingestion of lead paint and batteries is also a route of exposure for livestock, which can subsequently affect humans.[281] Milk produced by contaminated cattle can be diluted to a lower lead concentration and sold for consumption.[282]

In Bangladesh, lead compounds have been added to turmeric to make it more yellow.[283] This is believed to have started in the 1980s and continues as of 2019.[283] It is believed to be one of the main sources of high lead levels in the country.[284] In Hong Kong the maximum allowed lead parts per million is 6 in solid foods and 1 in liquid foods.[285]

In December 2022, Consumer Reports tested 28 dark chocolate brands and found that 23 of 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 to certain people, specially pregnant women.[286] Lead-containing dust can settle on drying cocoa beans when they are set outside near polluting industrial plants.[287]

Lead in plastic toys

According to the United States Center for Disease Control, the use of lead in plastics has not been banned. Lead softens the plastic and makes it more flexible so that it can go back to its original shape. It may also 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.[288]

Treatment

Treatment for lead poisoning normally involves the administration of dimercaprol and succimer.[289] 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.[290]

Environmental effects

 
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. [291]

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.[291] 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.[292] Elevated concentrations of lead persist in soils and sediments in post-industrial and urban areas; industrial emissions, including those arising from coal burning,[293] continue in many parts of the world, particularly in the developing countries.[294]

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 plants 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.[295] Fish uptake lead from both water and sediment;[296] bioaccumulation in the food chain poses a hazard to fish, birds, and sea mammals.[297]

Anthropogenic lead includes lead from shot and sinkers. These are among the most potent sources of lead contamination along with lead production sites.[298] Lead was banned for shot and sinkers in the United States in 2017,[299] although that ban was only effective for a month,[300] and a similar ban is being considered in the European Union.[301]

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).[302] An important biomarker assay for lead poisoning is δ-aminolevulinic acid levels in plasma, serum, and urine.[303]

Restriction and remediation

 
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.[304] 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.[293] In 1992, U.S. Congress required the Environmental Protection Agency to reduce the blood lead levels of the country's children.[305] Lead use was further curtailed by the European Union's 2003 Restriction of Hazardous Substances Directive.[306] 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.[307]

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.[308] Lead may still be found in harmful quantities in stoneware,[309] vinyl[310] (such as that used for tubing and the insulation of electrical cords), and Chinese brass.[u] Old houses may still contain lead paint.[310] White lead paint has been withdrawn from sale in industrialized countries, but specialized uses of other pigments such as yellow lead chromate remain.[182] Stripping old paint by sanding produces dust which can be inhaled.[312] Lead abatement programs have been mandated by some authorities in properties where young children live.[313]

Lead waste, depending on the jurisdiction and the nature of the waste, may be treated as household waste (to facilitate lead abatement activities),[314] or potentially hazardous waste requiring specialized treatment or storage.[315] Lead is released into the environment in shooting places and a number of lead management practices have been developed to counter the lead contamination.[316] 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.[317]

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.[318][319] The fungus Aspergillus versicolor is effective at absorbing lead ions from industrial waste before being released to water bodies.[320] 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.[321]

See also

Notes

  1. ^ The tetrahedral allotrope of tin is called α- or gray tin and is stable only at or below 13.2 °C (55.8 °F). The stable form of tin above this temperature is called β- or white tin and has a distorted face centered cubic (tetragonal) structure which can be derived by compressing the tetrahedra of gray tin along their cubic axes. White tin effectively has a structure intermediate between the regular tetrahedral structure of gray tin, and the regular face centered cubic structure of lead, consistent with the general trend of increasing metallic character going down any representative group.[15]
  2. ^ A quasicrystalline thin-film allotrope of lead, with pentagonal symmetry, was reported in 2013. The allotrope was obtained by depositing lead atoms on the surface of an icosahedral silver-indium-ytterbium quasicrystal. Its conductivity was not recorded.[16][17]
  3. ^ Diamond cubic structures with lattice parameters around the lattice parameter of silicon exists both in thin lead and tin films, and in massive lead and tin, freshly solidified in vacuum of ~5 x 10−6 Torr. Experimental evidence for almost identical structures of at least three oxide types is presented, demonstrating that lead and tin behave like silicon not only in the initial stages of crystallization, but also in the initial stages of oxidation.[18]
  4. ^ British English: to go down like a lead balloon.
  5. ^ Malleability describes how easily it deforms under compression, whereas ductility means its ability to stretch.
  6. ^ A (wet) finger can be dipped into molten lead without risk of a burning injury.[31]
  7. ^ An even number of either protons or neutrons generally increases the nuclear stability of isotopes, compared to isotopes with odd numbers. No elements with odd atomic numbers have more than two stable isotopes; even-numbered elements have multiple stable isotopes, with tin (element 50) having the highest number of isotopes of all elements, ten.[35] See Even and odd atomic nuclei for more details.
  8. ^ The half-life found in the experiment was 1.9×1019 years.[38] A kilogram of natural bismuth would have an activity value of approximately 0.003 becquerels (decays per second). For comparison, the activity value of natural radiation in the human body is around 65 becquerels per kilogram of body weight (4500 becquerels on average).[39]
  9. ^ Lead-205 decays solely via electron capture, which means when there are no electrons available and lead is fully ionized with all 82 electrons removed it cannot decay. Fully ionized thallium-205, the isotope lead-205 would decay to, becomes unstable and can decay into a bound state of lead-205.[50]
  10. ^ Tetraphenyllead is even more thermally stable, decomposing at 270 °C.[91]
  11. ^ Abundances in the source are listed relative to silicon rather than in per-particle notation. The sum of all elements per 106 parts of silicon is 2.6682×1010 parts; lead comprises 3.258 parts.
  12. ^ Elemental abundance figures are estimates and their details may vary from source to source.[113]
  13. ^ The inscription reads: "Made when the Emperor Vespasian was consul for the ninth term and the Emperor Titus was consul for the seventh term, when Gnaeus Iulius Agricola was imperial governor (of Britain)."
  14. ^ The fact that Julius Caesar fathered only one child, as well as the alleged sterility of his successor, Caesar Augustus, have been attributed to lead poisoning.[148]
  15. ^ Gaseous by-product of the coking process, containing carbon monoxide, hydrogen and methane; used as a fuel.
  16. ^ California began banning lead bullets for hunting on that basis in July 2015.[212]
  17. ^ For example, a firm "...producing quality [lead] garden ornament from our studio in West London for over a century".[219]
  18. ^ Potential injuries to regular users of such batteries are not related to lead's toxicity.[229]
  19. ^ See[231] for details on how a lead–acid battery works.
  20. ^ Rates vary greatly by country.[251]
  21. ^ An alloy of brass (copper and zinc) with lead, iron, tin, and sometimes antimony.[311]

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  This article was submitted to WikiJournal of Science for external academic peer review in 2017 (reviewer reports). The updated content was reintegrated into the Wikipedia page under a CC-BY-SA-3.0 license (2018). The version of record as reviewed is: Mikhail Boldyrev; et al. (3 July 2018). "Lead: properties, history, and applications" (PDF). WikiJournal of Science. 1 (2): 7. doi:10.15347/WJS/2018.007. ISSN 2470-6345. Wikidata Q56050531.

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lead, this, article, about, metal, other, uses, disambiguation, chemical, element, with, symbol, from, latin, plumbum, atomic, number, heavy, metal, that, denser, than, most, common, materials, soft, malleable, also, relatively, melting, point, when, freshly, . This article is about the metal For other uses see Lead disambiguation Lead is a chemical element with the symbol Pb from the Latin plumbum and atomic number 82 It is a heavy metal that is denser than most common materials Lead is soft and malleable and also has a relatively low melting point When freshly cut lead is a shiny gray with a hint of blue It tarnishes to a dull gray color when exposed 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 toxic even in small amounts especially to children Lead 82PbLeadPronunciation ˈ l ɛ d wbr led Appearancemetallic grayStandard atomic weight Ar Pb 206 14 207 94 207 2 1 1 abridged 1 Lead in the periodic tableHydrogen HeliumLithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine NeonSodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine ArgonPotassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine KryptonRubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine XenonCaesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury element Thallium Lead Bismuth Polonium Astatine RadonFrancium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Sn Pb Flthallium lead bismuthAtomic number Z 82Groupgroup 14 carbon group Periodperiod 6Block p blockElectron configuration Xe 4f14 5d10 6s2 6p2Electrons per shell2 8 18 32 18 4Physical propertiesPhase at STPsolidMelting point600 61 K 327 46 C 621 43 F Boiling point2022 K 1749 C 3180 F Density near r t 11 34 g cm3when liquid at m p 10 66 g cm3Heat of fusion4 77 kJ molHeat of vaporization179 5 kJ molMolar heat capacity26 650 J mol K Vapor pressureP Pa 1 10 100 1 k 10 k 100 kat T K 978 1088 1229 1412 1660 2027Atomic propertiesOxidation states 4 2 1 0 2 1 2 3 4 an amphoteric oxide ElectronegativityPauling scale 2 33 in 4 1 87 in 2 Ionization energies1st 715 6 kJ mol2nd 1450 5 kJ mol3rd 3081 5 kJ molAtomic radiusempirical 175 pmCovalent radius146 5 pmVan der Waals radius202 pmSpectral lines of leadOther propertiesNatural occurrenceprimordialCrystal structure face centered cubic fcc a 495 08 pmSpeed of sound thin rod1190 m s at r t annealed Thermal expansion28 9 µm m K at 25 C Thermal conductivity35 3 W m K Electrical resistivity208 nW m at 20 C Magnetic orderingdiamagneticMolar magnetic susceptibility 23 0 10 6 cm3 mol at 298 K 3 Young s modulus16 GPaShear modulus5 6 GPaBulk modulus46 GPaPoisson ratio0 44Mohs hardness1 5Brinell hardness38 50 MPaCAS Number7439 92 1HistoryDiscoveryMiddle East 7000 BCE Symbol Pb from Latin plumbumIsotopes of leadveMain isotopes 4 Decayabun dance half life t1 2 mode pro duct202Pb synth 5 25 104 y e 202Tl204Pb 1 40 stable205Pb trace 1 73 107 y e 205Tl206Pb 24 1 stable207Pb 22 1 stable208Pb 52 4 stable209Pb trace 3 253 h b 209Bi210Pb trace 22 20 y b 210Bi211Pb trace 36 1 min b 211Bi212Pb trace 10 64 h b 212Bi214Pb trace 26 8 min b 214BiIsotopic abundances vary greatly by sample 5 Category Leadviewtalkedit referencesLead is a relatively unreactive post transition metal Its weak metallic character is illustrated by its amphoteric nature lead and lead oxides react with acids and bases and it tends to form covalent bonds Compounds of lead are usually found in the 2 oxidation state rather than the 4 state common with lighter members of the carbon group Exceptions are mostly limited to organolead compounds Like the lighter members of the group lead tends to bond with itself it can form 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 6 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 and shot weights solders pewters fusible alloys white paints leaded gasoline and radiation shielding Lead s toxicity became widely recognized in the late 19th century although a number of well educated ancient Greek and Roman writers were aware of this fact and even knew some of the symptoms of lead poisoning Lead is a neurotoxin that accumulates in soft tissues and bones it damages the nervous system and interferes with the function of biological enzymes causing neurological disorders ranging from behavioral problems to brain damage and also affects general health cardiovascular and renal systems Contents 1 Physical properties 1 1 Atomic 1 2 Bulk 1 3 Isotopes 2 Chemistry 2 1 Inorganic compounds 2 1 1 Lead II 2 1 2 Lead IV 2 1 3 Other oxidation states 2 2 Organolead 3 Origin and occurrence 3 1 In space 3 2 On Earth 4 Etymology 5 History 5 1 Prehistory and early history 5 2 Classical era 5 2 1 Confusion with tin and antimony 5 3 Middle Ages and the Renaissance 5 4 Outside Europe and Asia 5 5 Industrial Revolution 5 6 Modern era 6 Production 6 1 Primary 6 1 1 Two stage process 6 1 2 Direct process 6 1 3 Alternatives 6 2 Secondary 7 Applications 7 1 Elemental form 7 2 Batteries 7 3 Coating for cables 7 4 Compounds 8 Biological effects 8 1 Toxicity 8 2 Effects 8 3 Exposure sources 8 3 1 Lead in foods 8 3 2 Lead in plastic toys 8 4 Treatment 9 Environmental effects 10 Restriction and remediation 11 See also 12 Notes 13 References 14 Bibliography 15 Further reading 16 External linksPhysical properties EditAtomic Edit A lead atom has 82 electrons arranged in an electron configuration of Xe 4f145d106s26p2 The sum of lead s first and second ionization energies the total energy required to remove the two 6p electrons is close to that of tin lead s upper neighbor in the carbon group This is unusual ionization energies generally fall going down a group as an element s outer electrons become more distant from the nucleus and more shielded by smaller orbitals The sum of the first four ionization energies of lead exceeds that of tin 7 contrary to what periodic trends would predict This is explained by relativistic effects which become significant in heavier atoms 8 which contract s and p orbitals such that lead s 6s electrons have larger binding energies than its 5s electrons 9 A consequence is the so called inert pair effect the 6s electrons of lead become reluctant to participate in bonding stabilising the 2 oxidation state and making the distance between nearest atoms in crystalline lead unusually long 10 Lead s lighter carbon group congeners form stable or metastable allotropes with the tetrahedrally coordinated and covalently bonded diamond cubic structure The energy levels of their outer s and p orbitals are close enough to allow mixing into four hybrid sp3 orbitals In lead the inert pair effect increases the separation between its s and p orbitals and the gap cannot be overcome by the energy that would be released by extra bonds following hybridization 11 Rather than having a diamond cubic structure lead forms metallic bonds in which only the p electrons are delocalized and shared between the Pb2 ions Lead consequently has a face centered cubic structure 12 like the similarly sized 13 divalent metals calcium and strontium 14 a b c Bulk Edit Pure lead has a bright shiny gray appearance with a hint of blue 19 It tarnishes on contact with moist air and takes on a dull appearance the hue of which depends on the prevailing conditions Characteristic properties of lead include high density malleability ductility and high resistance to corrosion due to passivation 20 A sample of lead solidified from the molten state Lead s close packed face centered cubic structure and high atomic weight result in a density 21 of 11 34 g cm3 which is greater than that of common metals such as iron 7 87 g cm3 copper 8 93 g cm3 and zinc 7 14 g cm3 22 This density is the origin of the idiom to go over like a lead balloon 23 24 d Some rarer metals are denser tungsten and gold are both at 19 3 g cm3 and osmium the densest metal known has a density of 22 59 g cm3 almost twice that of lead 25 Lead is a very soft metal with a Mohs hardness of 1 5 it can be scratched with a fingernail 26 It is quite malleable and somewhat ductile 27 e The bulk modulus of lead a measure of its ease of compressibility is 45 8 GPa In comparison that of aluminium is 75 2 GPa copper 137 8 GPa and mild steel 160 169 GPa 28 Lead s tensile strength at 12 17 MPa is low that of aluminium is 6 times higher copper 10 times and mild steel 15 times higher it can be strengthened by adding small amounts of copper or antimony 29 The melting point of lead at 327 5 C 621 5 F 30 is very low compared to most metals 21 f Its boiling point of 1749 C 3180 F 30 is the lowest among the carbon group elements The electrical resistivity of lead at 20 C is 192 nanoohm meters almost an order of magnitude higher than those of other industrial metals copper at 15 43 nW m gold 20 51 nW m and aluminium at 24 15 nW m 32 Lead is a superconductor at temperatures lower than 7 19 K 33 this is the highest critical temperature of all type I superconductors and the third highest of the elemental superconductors 34 Isotopes Edit Main article Isotopes of lead Natural lead consists of four stable isotopes with mass numbers of 204 206 207 and 208 35 and traces of five short lived radioisotopes 36 The high number of isotopes is consistent with lead s atomic number being even g Lead has a magic number of protons 82 for which the nuclear shell model accurately predicts an especially stable nucleus 37 Lead 208 has 126 neutrons another magic number which may explain why lead 208 is extraordinarily stable 37 With its high atomic number lead is the heaviest element whose natural isotopes are regarded as stable lead 208 is the heaviest stable nucleus This distinction formerly fell to bismuth with an atomic number of 83 until its only primordial isotope bismuth 209 was found in 2003 to decay very slowly h The four stable isotopes of lead could theoretically undergo alpha decay to isotopes of mercury with a release of energy but this has not been observed for any of them their predicted half lives range from 1035 to 10189 years 40 at least 1025 times the current age of the universe Three of the stable isotopes are found in three of the four major decay chains lead 206 lead 207 and lead 208 are the final decay products of uranium 238 uranium 235 and thorium 232 respectively 41 These decay chains are called the uranium chain the actinium chain and the thorium chain 42 Their isotopic concentrations in a natural rock sample depends greatly on the presence of these three parent uranium and thorium isotopes For example the relative abundance of lead 208 can range from 52 in normal samples to 90 in thorium ores 43 for this reason the standard atomic weight of lead is given to only one decimal place 44 As time passes the ratio of lead 206 and lead 207 to lead 204 increases since the former two are supplemented by radioactive decay of heavier elements while the latter is not this allows for lead lead dating As uranium decays into lead their relative amounts change this is the basis for uranium lead dating 45 Lead 207 exhibits nuclear magnetic resonance a property that has been used to study its compounds in solution and solid state 46 47 including in the human body 48 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 Apart from the stable isotopes which make up almost all lead that exists naturally there are trace quantities of a few radioactive isotopes One of them is lead 210 although it has a half life of only 22 2 years 35 small quantities occur in nature because lead 210 is produced by a long decay series that starts with uranium 238 that has been present for billions of years on Earth Lead 211 212 and 214 are present in the decay chains of uranium 235 thorium 232 and uranium 238 respectively so traces of all three of these lead isotopes are found naturally Minute traces of lead 209 arise from the very rare cluster decay of radium 223 one of the daughter products of natural uranium 235 and the decay chain of neptunium 237 traces of which are produced by neutron capture in uranium ores Lead 210 is particularly useful for helping to identify the ages of samples by measuring its ratio to lead 206 both isotopes are present in a single decay chain 49 In total 43 lead isotopes have been synthesized with mass numbers 178 220 35 Lead 205 is the most stable radioisotope with a half life of around 1 73 107 years i The second most stable is lead 202 which has a half life of about 52 500 years longer than any of the natural trace radioisotopes 35 Chemistry Edit Flame test lead colors flame pale blue Bulk lead exposed to moist air forms a protective layer of varying composition Lead II carbonate is a common constituent 51 52 53 the sulfate or chloride may also be present in urban or maritime settings 54 This layer makes bulk lead effectively chemically inert in the air 54 Finely powdered lead as with many metals is pyrophoric 55 and burns with a bluish white flame 56 Fluorine reacts with lead at room temperature forming lead II fluoride The reaction with chlorine is similar but requires heating as the resulting chloride layer diminishes the reactivity of the elements 54 Molten lead reacts with the chalcogens to give lead II chalcogenides 57 Lead metal resists sulfuric and phosphoric acid but not hydrochloric or nitric acid the outcome depends on insolubility and subsequent passivation of the product salt 58 Organic acids such as acetic acid dissolve lead in the presence of oxygen 54 Concentrated alkalis will dissolve lead and form plumbites 59 Inorganic compounds Edit See also Compounds of lead Lead shows two main oxidation states 4 and 2 The tetravalent state is common for the carbon group The divalent state is rare for carbon and silicon minor for germanium important but not prevailing for tin and is the more important of the two oxidation states for lead 54 This is attributable to relativistic effects specifically the inert pair effect which manifests itself when there is a large difference in electronegativity between lead and oxide halide or nitride anions leading to a significant partial positive charge on lead The result is a stronger contraction of the lead 6s orbital than is the case for the 6p orbital making it rather inert in ionic compounds The inert pair effect is less applicable to compounds in which lead forms covalent bonds with elements of similar electronegativity such as carbon in organolead compounds In these the 6s and 6p orbitals remain similarly sized and sp3 hybridization is still energetically favorable Lead like carbon is predominantly tetravalent in such compounds 60 There is a relatively large difference in the electronegativity of lead II at 1 87 and lead IV at 2 33 This difference marks the reversal in the trend of increasing stability of the 4 oxidation state going down the carbon group tin by comparison has values of 1 80 in the 2 oxidation state and 1 96 in the 4 state 61 Lead II Edit Lead II oxideLead 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 54 Lead II ions are usually colorless in solution 62 and partially hydrolyze to form Pb OH and finally Pb4 OH 4 4 in which the hydroxyl ions act as bridging ligands 63 64 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 65 Lead monoxide exists in two polymorphs litharge a PbO red and massicot b PbO yellow the latter being stable only above around 488 C Litharge is the most commonly used inorganic compound of lead 66 There is no lead II hydroxide increasing the pH of solutions of lead II salts leads to hydrolysis and condensation 67 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 68 Lead and oxygen in a tetragonal unit cell of lead II IV oxide Lead dihalides are well characterized this includes the diastatide 69 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 70 The other dihalides decompose on exposure to ultraviolet or visible light especially the diiodide 71 Many lead II pseudohalides are known such as the cyanide cyanate and thiocyanate 68 72 Lead II forms an extensive variety of halide coordination complexes such as PbCl4 2 PbCl6 4 and the Pb2Cl9 n5n chain anion 71 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 73 Lead IV Edit Few inorganic lead IV compounds are known They are only formed in highly oxidizing solutions and do not normally exist under standard conditions 74 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 75 This is because the expected PbCl4 that would be produced is unstable and spontaneously decomposes to PbCl2 and Cl2 76 Analogously to lead monoxide lead dioxide is capable of forming plumbate anions Lead disulfide 77 and lead diselenide 78 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 79 Other oxidation states Edit See also Plumbide The capped square antiprismatic anion Pb9 4 from K 18 crown 6 2K2Pb9 en 1 5 80 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 81 82 83 The same applies for lead I which can be found in such radical species 84 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 85 Negative oxidation states can occur as Zintl phases as either free lead anions as in Ba2Pb with lead formally being lead IV 86 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 87 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 63 They may be made in liquid ammonia via the reduction of lead by sodium 88 Organolead Edit Main article Organolead compound 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 57 With itself lead can build metal metal bonds of an order up to three 89 With carbon lead forms organolead compounds similar to but generally less stable than typical organic compounds 90 due to the Pb C bond being rather weak 63 This makes the organometallic chemistry of lead far less wide ranging than that of tin 91 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 Pb h5 C5H5 2 91 The lead analog of the simplest organic compound methane is plumbane Plumbane may be obtained in a reaction between metallic lead and atomic hydrogen 92 Two simple derivatives tetramethyllead and tetraethyllead are the best known organolead compounds These compounds are relatively stable tetraethyllead only starts to decompose if heated 93 or if exposed to sunlight or ultraviolet light 94 j With sodium metal lead readily forms an equimolar alloy that reacts with alkyl halides to form organometallic compounds such as tetraethyllead 95 The oxidizing nature of many organolead compounds is usefully exploited lead tetraacetate is an important laboratory reagent for oxidation in organic synthesis 96 Tetraethyllead once added to gasoline was produced in larger quantities than any other organometallic compound 91 Other organolead compounds are less chemically stable 90 For many organic compounds a lead analog does not exist 92 Origin and occurrence EditSolar System abundances 97 Atomicnumber Element Relativeamount42 Molybdenum 0 79846 Palladium 0 44050 Tin 1 14678 Platinum 0 41780 Mercury 0 12782 Lead 190 Thorium 0 01192 Uranium 0 003In space Edit Lead s per particle abundance in the Solar System is 0 121 ppb parts per billion 97 k This figure is two and a half times higher than that of platinum eight times more than mercury and seventeen times more than gold 97 The amount of lead in the universe is slowly increasing 98 as most heavier atoms all of which are unstable gradually decay to lead 99 The abundance of lead in the Solar System since its formation 4 5 billion years ago has increased by about 0 75 100 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 97 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 101 In the s process s is for slow captures are separated by years or decades allowing less stable nuclei to undergo beta decay 102 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 15 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 Bismuth 209 is also radioactive and eventually decays into thallium 205 if left unperturbed 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 thallium 205 103 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 104 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 105 The r process does not form as much lead as the s process 106 It tends to stop once neutron rich nuclei reach 126 neutrons 107 At this point the neutrons are arranged in complete shells in the atomic nucleus and it becomes harder to energetically accommodate more of them 108 When the neutron flux subsides these nuclei beta decay into stable isotopes of osmium iridium and platinum 109 On Earth Edit Lead is classified as a chalcophile under the Goldschmidt classification meaning it is generally found combined with sulfur 110 It rarely occurs in its native metallic form 111 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 38th most abundant element in the crust 112 l The main lead bearing mineral is galena PbS which is mostly found with zinc ores 114 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 and bismuth are common impurities in lead minerals 114 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 and the 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 and Russia 6 4 million 115 Typical background concentrations of lead do not exceed 0 1 mg m3 in the atmosphere 100 mg kg in soil 4 mg kg in vegetation and 5 mg L in freshwater and seawater 116 Etymology EditThe modern English word lead is of Germanic origin it comes from the Middle English leed and Old English lead with the macron above the e signifying that the vowel sound of that letter is long 117 The Old English word is derived from the hypothetical reconstructed Proto Germanic lauda lead 118 According to linguistic theory this word bore descendants in multiple Germanic languages of exactly the same meaning 118 There is no consensus on the origin of the Proto Germanic lauda One hypothesis suggests it is derived from Proto Indo European lAudh lead capitalization of the vowel is equivalent to the macron 119 Another hypothesis suggests it is borrowed from Proto Celtic ɸloud io lead This word is related to the Latin plumbum which gave the element its chemical symbol Pb The word ɸloud io is thought to be the origin of Proto Germanic bliwa which also means lead from which stemmed the German Blei 120 The name of the chemical element is not related to the verb of the same spelling which is derived from Proto Germanic laidijan to lead 121 History EditPrehistory and early history Edit World lead production peaking in the Roman period and the Industrial Revolution 122 Metallic lead beads dating back to 7000 6500 BCE have been found in Asia Minor and may represent the first example of metal smelting 123 At that time lead had few if any applications due to its softness and dull appearance 123 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 124 The Ancient Egyptians were the first to use lead minerals in cosmetics an application that spread to Ancient Greece and beyond 125 the Egyptians may have used lead for sinkers in fishing nets glazes glasses enamels and for ornaments 124 Various civilizations of the Fertile Crescent used lead as a writing material as coins 126 and as a construction material 124 Lead was used in the Ancient Chinese royal court as a stimulant 124 as currency 127 and as a contraceptive 128 the Indus Valley civilization and the Mesoamericans 124 used it for making amulets and the eastern and southern African peoples used lead in wire drawing 129 Classical era Edit Because silver was extensively used as a decorative material and an exchange medium lead deposits came to be worked in Asia Minor from 3000 BCE later lead deposits were developed in the Aegean and Laurion 130 These three regions collectively dominated production of mined lead until c 1200 BCE 131 Beginning circa 2000 BCE the Phoenicians worked deposits in the Iberian peninsula by 1600 BCE lead mining existed in Cyprus Greece and Sardinia 132 Ancient Greek lead sling bullets with a winged thunderbolt molded on one side and the inscription DE3AI take that or catch on the other side 133 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 122 134 Lead mining occurred in Central Europe Britain the Balkans Greece Anatolia and Hispania the latter accounting for 40 of world production 122 Lead tablets were commonly used as a material for letters 135 Lead coffins cast in flat sand forms with interchangeable motifs to suit the faith of the deceased were used in ancient Judea 136 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 137 Roman lead pipes m Lead was used for making water pipes in the Roman Empire the Latin word for the metal plumbum 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 corrosion 138 ensured its widespread use in other applications including pharmaceuticals roofing currency and warfare 139 140 141 Writers of the time such as Cato the Elder Columella and Pliny the Elder recommended lead or 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 or bronze vessels could impart a bitter flavor through verdigris formation 142 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 1992 143 The Roman author Vitruvius reported the health dangers of lead 144 145 and modern writers have suggested that lead poisoning played a major role in the decline of the Roman Empire 146 147 n Other researchers have criticized such claims pointing out for instance that not all abdominal pain is caused by lead poisoning 149 150 According to archaeological research Roman lead pipes increased lead levels in tap water but such an effect was unlikely to have been truly harmful 151 152 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 153 Its status in Roman society was low as it was readily available 154 and cheap 155 Confusion with tin and antimony Edit 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 plumbum nigrum black lead and tin plumbum candidum bright lead The association of lead and tin can be seen in other languages the word olovo in Czech translates to lead but in Russian its cognate olovo olovo means tin 156 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 157 In countries such as Turkey and India the originally Persian name surma came to refer to either antimony sulfide or lead sulfide 158 and in some languages such as Russian gave its name to antimony surma 159 Middle Ages and the Renaissance Edit Elizabeth I of England was commonly depicted with a whitened face Lead in face whiteners is thought to have contributed to her death 160 Lead mining in Western Europe declined after the fall of the Western Roman Empire with Arabian Iberia being the only region having a significant output 161 162 The largest production of lead occurred in South and East Asia especially China and India where lead mining grew rapidly 162 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 163 In the European and Arabian traditions of alchemy lead symbol in the European tradition 164 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 165 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 161 166 Lead was a key material in parts of the printing press and lead dust was commonly inhaled by print workers causing lead poisoning 167 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 168 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 169 170 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 171 with lead commonly used in the whitener 172 Outside Europe and Asia Edit 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 173 In Australia the first mine opened by colonists on the continent was a lead mine in 1841 174 In Africa lead mining and smelting were known in the Benue Trough 175 and the lower Congo Basin where lead was used for trade with Europeans and as a currency by the 17th century 176 well before the scramble for Africa Industrial Revolution Edit 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 177 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 178 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 179 A great share of the demand for lead came from plumbing and painting lead paints were in regular use 180 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 180 Modern era Edit Promotional poster for Dutch Boy lead paint United States 1912Further 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 181 Most European countries banned lead paint commonly used because of its opacity and water resistance 182 for interiors by 1930 183 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 180 In the 1970s the United States and Western European countries introduced legislation to reduce lead air pollution 184 185 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 2 186 The main product made of lead by the end of the 20th century was the lead acid battery 187 From 1960 to 1990 lead output in the Western Bloc grew by about 31 188 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 189 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 190 As was the case during European industrialization lead has had a negative effect on health in China 191 Production Edit Primary production of lead since 1840 As of 2014 production of lead is increasing worldwide due to its use in lead acid batteries 192 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 the United States 115 The top three producers of refined lead were China the United States and India 193 According to the International Resource Panel s 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 194 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 195 Primary Edit Most lead ores contain a low percentage of lead rich ores have a typical content of 3 8 which must be concentrated for extraction 196 During initial processing ores typically undergo crushing dense medium separation grinding froth flotation and drying The resulting concentrate which has a lead content of 30 80 by mass regularly 50 60 196 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 197 World s largest mining countries of lead 2016 115 Country Output thousand tons China 2 400 Australia 500 United States 335 Peru 310 Mexico 250 Russia 225 India 135 Bolivia 80 Sweden 76 Turkey 75 Iran 41 Kazakhstan 41 Poland 40 South Africa 40 North Korea 35 Ireland 33 North Macedonia 33Other countries 170 Two stage process Edit First the sulfide concentrate is roasted in air to oxidize the lead sulfide 198 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 199 This impure lead oxide is reduced in a coke fired blast furnace to the again impure metal 200 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 and sulfur which oxidizes the impurities except for silver gold and bismuth Oxidized contaminants float to the top of the melt and are skimmed off 201 202 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 202 203 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 202 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 202 204 This is a high cost process and thus mostly reserved for refining bullion containing high percentages of impurities 205 Direct process Edit 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 gas o 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 197 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 197 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 197 Alternatives Edit 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 a cathode is a technique that may have potential but is not currently economical except in cases where electricity is very cheap 206 Secondary Edit Further information Battery recycling Lead acid batteries 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 195 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 produced semisoft lead 3 4 antimony 207 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 208 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 208 Of the sources of lead for recycling lead acid batteries are the most important lead pipe sheet and cable sheathing are also significant 195 Applications Edit Bricks of lead alloyed with 4 antimony are used as radiation shielding 209 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 act for lead or lead mockup 210 Elemental form Edit 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 211 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 168 Concerns have been raised that lead bullets used for hunting can damage the environment p 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 213 It is used in scuba diving weight belts to counteract the diver s buoyancy 214 In 1993 the base of the Leaning Tower of Pisa was stabilized with 600 tonnes of lead 215 Because of its corrosion resistance lead is used as a protective sheath for underwater cables 216 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 and on roof parapets 217 218 Lead is still used in statues and sculptures q including for armatures 220 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 115 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 221 Lead s high density atomic number and formability form the basis for use of lead as a barrier that absorbs sound vibration and radiation 222 Lead has no natural resonance frequencies 222 as a result sheet lead is used as a sound deadening layer in the walls floors and ceilings of sound studios 223 Organ pipes are often made from a lead alloy mixed with various amounts of tin to control the tone of each pipe 224 225 Lead is an established shielding material from radiation in nuclear science and in X ray rooms 226 due to its denseness and high attenuation coefficient 227 Molten lead has been used as a coolant for lead cooled fast reactors 228 Batteries Edit 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 r People who work in lead battery production plants may be exposed to lead dust and inhale it 230 The reactions in the battery between lead lead dioxide and sulfuric acid provide a reliable source of voltage s 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 232 These batteries have lower energy density and charge discharge efficiency than lithium ion batteries but are significantly cheaper 233 Coating for cables Edit 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 234 Its use in solder for electronics is also being phased out by some countries to reduce the amount of environmentally hazardous waste 235 Lead is one of three metals used in the Oddy test for museum materials helping detect organic acids aldehydes and acidic gases 236 237 Compounds Edit Lead glass Lead yellow and red lead 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 Pb s PbO2 s 2H2 SO4 aq 2PbSO4 s 2H2 O 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 238 While lead paints are phased out in Europe and North America they remain in use in less developed countries such as China 239 India 240 or Indonesia 241 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 242 243 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 244 245 Lead glass is composed of 12 28 lead oxide changing its optical characteristics and reducing the transmission of ionizing radiation 246 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 247 Biological effects EditMain article Lead poisoning Lead HazardsGHS labelling Pictograms Signal word DangerHazard statements H302 H332 H351 H360Df H373 H410Precautionary statements P201 P261 P273 P304 P308 P312 P313 P340 P391 248 NFPA 704 fire diamond 200 Lead has no confirmed biological role and there is no confirmed safe level of lead exposure 249 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 250 Its prevalence in the human body at an adult average of 120 mg t is nevertheless exceeded only by zinc 2500 mg and iron 4000 mg among the heavy metals 252 Lead salts are very efficiently absorbed by the body 253 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 254 Toxicity Edit Lead is a highly poisonous metal whether inhaled or swallowed affecting almost every organ and system in the human body 255 At airborne levels of 100 mg m3 it is immediately dangerous to life and health 256 Most ingested lead is absorbed into the bloodstream 257 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 258 or mimicking and displacing other metals which act as cofactors in many enzymatic reactions 259 The essential metals that lead interacts with include calcium iron and zinc 260 High levels of calcium and iron tend to provide some protection from lead poisoning low levels cause increased susceptibility 253 Effects Edit 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 258 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 261 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 citation needed Several studies mostly cross sectional found an association between increased lead exposure and decreased heart rate variability 262 In pregnant women high levels of exposure to lead may cause miscarriage Chronic high level exposure has been shown to reduce fertility in males 263 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 264 Early childhood exposure has been linked with an increased risk of sleep disturbances and excessive daytime drowsiness in later childhood 265 High blood levels are associated with delayed puberty in girls 266 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 Edit 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 267 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 268 Seawater products can contain lead if affected by nearby industrial waters 269 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 and residual emissions from leaded gasoline 270 The use of lead for water pipes is a problem in areas with soft or acidic water 271 Hard water forms insoluble protective layers on the inner surface of the pipes whereas soft and acidic water dissolves the lead pipes 272 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 will contain and the more the inside of the pipes will be coated with a protective layer of lead carbonate or lead sulfate 273 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 Alternatively as the applied dry paint deteriorates it peels is pulverized into dust and then enters the body through hand to mouth contact or contaminated food water or alcohol Ingesting certain home remedies may result in exposure to lead or its compounds 274 Inhalation is the second major exposure pathway affecting smokers and especially workers in lead related occupations 257 Cigarette smoke contains among other toxic substances radioactive lead 210 275 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 276 The concentration of lead in the air in the United States fell below the national standard of 0 15 mg m3 277 in 2014 278 Skin exposure may be significant for people working with organic lead compounds The rate of skin absorption is lower for inorganic lead 279 Lead in foods Edit 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 280 Ingestion of lead paint and batteries is also a route of exposure for livestock which can subsequently affect humans 281 Milk produced by contaminated cattle can be diluted to a lower lead concentration and sold for consumption 282 In Bangladesh lead compounds have been added to turmeric to make it more yellow 283 This is believed to have started in the 1980s and continues as of 2019 update 283 It is believed to be one of the main sources of high lead levels in the country 284 In Hong Kong the maximum allowed lead parts per million is 6 in solid foods and 1 in liquid foods 285 In December 2022 Consumer Reports tested 28 dark chocolate brands and found that 23 of 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 to certain people specially pregnant women 286 Lead containing dust can settle on drying cocoa beans when they are set outside near polluting industrial plants 287 Lead in plastic toys Edit According to the United States Center for Disease Control the use of lead in plastics has not been banned Lead softens the plastic and makes it more flexible so that it can go back to its original shape It may also 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 288 Treatment Edit See also Chelation therapy Treatment for lead poisoning normally involves the administration of dimercaprol and succimer 289 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 290 Environmental effects Edit 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 291 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 291 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 292 Elevated concentrations of lead persist in soils and sediments in post industrial and urban areas industrial emissions including those arising from coal burning 293 continue in many parts of the world particularly in the developing countries 294 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 plants 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 295 Fish uptake lead from both water and sediment 296 bioaccumulation in the food chain poses a hazard to fish birds and sea mammals 297 Anthropogenic lead includes lead from shot and sinkers These are among the most potent sources of lead contamination along with lead production sites 298 Lead was banned for shot and sinkers in the United States in 2017 299 although that ban was only effective for a month 300 and a similar ban is being considered in the European Union 301 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 302 An important biomarker assay for lead poisoning is d aminolevulinic acid levels in plasma serum and urine 303 Restriction and remediation Edit Radiography of a swan found dead in Conde 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 304 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 293 In 1992 U S Congress required the Environmental Protection Agency to reduce the blood lead levels of the country s children 305 Lead use was further curtailed by the European Union s 2003 Restriction of Hazardous Substances Directive 306 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 307 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 mg m3 over an 8 hour workday and the blood lead level limit at 5 mg per 100 g of blood in 2012 308 Lead may still be found in harmful quantities in stoneware 309 vinyl 310 such as that used for tubing and the insulation of electrical cords and Chinese brass u Old houses may still contain lead paint 310 White lead paint has been withdrawn from sale in industrialized countries but specialized uses of other pigments such as yellow lead chromate remain 182 Stripping old paint by sanding produces dust which can be inhaled 312 Lead abatement programs have been mandated by some authorities in properties where young children live 313 Lead waste depending on the jurisdiction and the nature of the waste may be treated as household waste to facilitate lead abatement activities 314 or potentially hazardous waste requiring specialized treatment or storage 315 Lead is released into the environment in shooting places and a number of lead management practices have been developed to counter the lead contamination 316 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 317 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 318 319 The fungus Aspergillus versicolor is effective at absorbing lead ions from industrial waste before being released to water bodies 320 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 321 See also EditDerek 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 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 Notes Edit The tetrahedral allotrope of tin is called a or gray tin and is stable only at or below 13 2 C 55 8 F The stable form of tin above this temperature is called b or white tin and has a distorted face centered cubic tetragonal structure which can be derived by compressing the tetrahedra of gray tin along their cubic axes White tin effectively has a structure intermediate between the regular tetrahedral structure of gray tin and the regular face centered cubic structure of lead consistent with the general trend of increasing metallic character going down any representative group 15 A quasicrystalline thin film allotrope of lead with pentagonal symmetry was reported in 2013 The allotrope was obtained by depositing lead atoms on the surface of an icosahedral silver indium ytterbium quasicrystal Its conductivity was not recorded 16 17 Diamond cubic structures with lattice parameters around the lattice parameter of silicon exists both in thin lead and tin films and in massive lead and tin freshly solidified in vacuum of 5 x 10 6 Torr Experimental evidence for almost identical structures of at least three oxide types is presented demonstrating that lead and tin behave like silicon not only in the initial stages of crystallization but also in the initial stages of oxidation 18 British English to go down like a lead balloon Malleability describes how easily it deforms under compression whereas ductility means its ability to stretch A wet finger can be dipped into molten lead without risk of a burning injury 31 An even number of either protons or neutrons generally increases the nuclear stability of isotopes compared to isotopes with odd numbers No elements with odd atomic numbers have more than two stable isotopes even numbered elements have multiple stable isotopes with tin element 50 having the highest number of isotopes of all elements ten 35 See Even and odd atomic nuclei for more details The half life found in the experiment was 1 9 1019 years 38 A kilogram of natural bismuth would have an activity value of approximately 0 003 becquerels decays per second For comparison the activity value of natural radiation in the human body is around 65 becquerels per kilogram of body weight 4500 becquerels on average 39 Lead 205 decays solely via electron capture which means when there are no electrons available and lead is fully ionized with all 82 electrons removed it cannot decay Fully ionized thallium 205 the isotope lead 205 would decay to becomes unstable and can decay into a bound state of lead 205 50 Tetraphenyllead is even more thermally stable decomposing at 270 C 91 Abundances in the source are listed relative to silicon rather than in per particle notation The sum of all elements per 106 parts of silicon is 2 6682 1010 parts lead comprises 3 258 parts Elemental abundance figures are estimates and their details may vary from source to source 113 The inscription reads Made when the Emperor Vespasian was consul for the ninth term and the Emperor Titus was consul for the seventh term when Gnaeus Iulius Agricola was imperial governor of Britain The fact that Julius Caesar fathered only one child as well as the alleged sterility of his successor Caesar Augustus have been attributed to lead poisoning 148 Gaseous by product of the coking process containing carbon monoxide hydrogen and methane used as a fuel California began banning lead bullets for hunting on that basis in July 2015 212 For example a firm producing quality lead garden ornament from our studio in West London for over a century 219 Potential injuries to regular users of such batteries are not related to lead s toxicity 229 See 231 for details on how a lead acid battery works Rates vary greatly by country 251 An alloy of brass copper and zinc with lead iron tin and sometimes antimony 311 References Edit Standard Atomic Weights Lead CIAAW 2020 Pb 0 carbonyls have been observered in reaction between lead atoms and carbon monoxide see Ling Jiang Qiang Xu 2005 Observation of the lead carbonyls PbnCO n 1 4 Reactions of lead atoms and small clusters with carbon monoxide in solid argon The Journal of Chemical Physics 122 3 034505 122 3 34505 Bibcode 2005JChPh 122c4505J doi 10 1063 1 1834915 ISSN 0021 9606 PMID 15740207 Weast Astle amp Beyer 1983 p E110 Kondev F G Wang M Huang W J Naimi S Audi G 2021 The NUBASE2020 evaluation of nuclear properties PDF Chinese Physics C 45 3 030001 doi 10 1088 1674 1137 abddae Meija et al 2016 sfn error no target CITEREFMeijaCoplenBerglundBrand2016 help Theodore Low De Vinne 1899 The Practice of Typography A Treatise on the Processes of Type making the Point System the Names Sizes Styles and Prices of Plain Printing Types Century Company pp 9 36 Lide 2005 p 10 179 Pyykko 1988 pp 563 594 Claudio Godwin amp Magyar 2002 pp 1 144 Norman 1996 p 36 Greenwood amp Earnshaw 1998 pp 226 227 374 Christensen 2002 p 867 Slater 1964 Considine amp Considine 2013 pp 501 2970 Parthe 1964 p 13 Sharma et al 2013 Sharma et al 2014 p 174710 Peneva Djuneva amp Tsukeva 1981 Greenwood amp Earnshaw 1998 p 372 Greenwood amp Earnshaw 1998 pp 372 373 a b Thornton Rautiu amp Brush 2001 p 6 Lide 2005 pp 12 35 12 40 Brenner 2003 p 396 Jones 2014 p 42 Lide 2005 pp 4 13 4 21 4 33 Vogel amp Achilles 2013 p 8 Anderson 1869 pp 341 343 Gale amp Totemeier 2003 pp 15 2 15 3 Thornton Rautiu amp Brush 2001 p 8 a b Lide 2005 p 12 219 Willey 1999 Lide 2005 p 12 45 Blakemore 1985 p 272 Webb Marsiglio amp Hirsch 2015 a b c d e IAEA Nuclear Data Section 2017 University of California Nuclear Forensic Search Project a b Stone 1997 de Marcillac et al 2003 pp 876 78 World Nuclear Association 2015 Beeman et al 2013 Radioactive Decay Series 2012 Committee on Evaluation of EPA Guidelines for Exposure to Naturally Occurring Radioactive Materials et al 1999 Smirnov Borisevich amp Sulaberidze 2012 Greenwood amp Earnshaw 1998 p 368 Levin 2009 pp 40 41 Webb 2000 p 115 Wrackmeyer amp Horchler 1990 Cangelosi amp Pecoraro 2015 Fiorini 2010 pp 7 8 Takahashi et al 1987 Thurmer Williams amp Reutt Robey 2002 pp 2033 2035 Tetreault Sirois amp Stamatopoulou 1998 pp 17 32 Thornton Rautiu amp Brush 2001 pp 10 11 a b c d e f Greenwood amp Earnshaw 1998 p 373 Bretherick 2016 p 1442 Harbison Bourgeois amp Johnson 2015 p 132 a b Greenwood amp Earnshaw 1998 p 374 Thornton Rautiu amp Brush 2001 pp 11 12 Polyanskiy 1986 p 20 Kaupp 2014 pp 9 10 Dieter amp Watson 2009 p 509 Hunt 2014 p 215 a b c King 1995 pp 43 63 Bunker amp Casey 2016 p 89 Whitten Gailey amp David 1996 pp 904 905 Greenwood amp Earnshaw 1998 p 384 Greenwood amp Earnshaw 1998 p 387 a b Greenwood amp Earnshaw 1998 p 389 Zuckerman amp Hagen 1989 p 426 Funke 2013 a b Greenwood amp Earnshaw 1998 p 382 Bharara amp Atwood 2006 p 4 Greenwood amp Earnshaw 1998 p 388 Toxicological Profile for Lead 2007 p 277 Downs amp Adams 2017 p 1128 Brescia 2012 p 234 Macintyre 1992 p 3775 Silverman 1966 pp 2067 2069 Greenwood amp Earnshaw 1998 p 381 Yong Hoffmann amp Fassler 2006 pp 4774 4778 Becker et al 2008 pp 9965 9978 Mosseri Henglein amp Janata 1990 pp 2722 2726 Konu amp Chivers 2011 pp 391 392 Hadlington 2017 p 59 Greenwood amp Earnshaw 1998 pp 384 386 Rohr 2017 Alsfasser 2007 pp 261 263 Greenwood amp Earnshaw 1998 p 393 Stabenow Saak amp Weidenbruch 2003 a b Polyanskiy 1986 p 43 a b c d Greenwood amp Earnshaw 1998 p 404 a b Wiberg Wiberg amp Holleman 2001 p 918 Toxicological Profile for Lead 2007 p 287 Polyanskiy 1986 p 44 Windholz 1976 Zyka 1966 p 569 a b c d Lodders 2003 pp 1222 1223 Roederer et al 2009 pp 1963 1980 Lochner Rohrbach amp Cochrane 2005 p 12 Lodders 2003 p 1224 Burbidge et al 1957 pp 608 615 Burbidge et al 1957 p 551 Burbidge et al 1957 pp 608 609 Burbidge et al 1957 p 553 Frebel 2015 pp 114 115 Burbidge et al 1957 pp 608 610 Burbidge et al 1957 p 595 Burbidge et al 1957 p 596 Burbidge et al 1957 pp 582 609 615 Langmuir amp Broecker 2012 pp 183 184 Davidson et al 2014 pp 4 5 Emsley 2011 pp 286 passim Cox 1997 p 182 a b Davidson et al 2014 p 4 a b c d United States Geological Survey 2017 p 97 Rieuwerts 2015 p 225 Merriam Webster a b Kroonen 2013 lauda Nikolayev 2012 Kroonen 2013 bliwa 2 Kroonen 2013 laidijan a b c Hong et al 1994 pp 1841 1843 a b Rich 1994 p 4 a b c d e Winder 1993b History of Cosmetics Chapurukha Kusimba June 20 2017 Making Cents of Currency s Ancient Rise Smithsonian Magazine Retrieved 5 November 2021 Yu amp Yu 2004 p 26 Toronto museum explores 2003 Bisson amp Vogel 2000 p 105 Wood Hsu amp Bell 2021 Rich 1994 p 5 United States Geological Survey 1973 Lead sling bullet de Callatay 2005 pp 361 372 Ceccarelli 2013 p 35 Ossuaries and Sarcophagi Calvo Rebollar 2019 p 45 Rich 1994 p 6 Thornton Rautiu amp Brush 2001 pp 179 184 Bisel amp Bisel 2002 pp 459 460 Retief amp Cilliers 2006 pp 149 151 Grout 2017 Eschnauer amp Stoeppler 1992 p 58 Hodge 1981 pp 486 491 Marcus Vitruvius Pollio 1914 c 15 BC De architectura Book 8 10 11 fulltext Gilfillan 1965 pp 53 60 Nriagu 1983 pp 660 663 Frankenburg 2014 p 16 Scarborough 1984 Waldron 1985 pp 107 108 Reddy amp Braun 2010 p 1052 Delile et al 2014 pp 6594 6599 Finger 2006 p 184 Lewis 1985 p 15 Thornton Rautiu amp Brush 2001 p 183 Polyanskiy 1986 p 8 Thomson 1830 p 74 Oxford English Dictionary surma Vasmer 1986 1987 surma Kellett 2012 pp 106 107 a b Winder 1993a a b Rich 1994 p 7 Rich 1994 p 8 Ede amp Cormack 2016 p 54 Cotnoir 2006 p 35 Samson 1885 p 388 Sinha et al 1993 a b Ramage 1980 p 8 Tungate 2011 p 14 Donnelly 2014 pp 171 172 Ashikari 2003 p 65 Nakashima et al 1998 p 59 Rabinowitz 1995 p 66 Gill amp Libraries Board of South Australia 1974 p 69 Bisson amp Vogel 2000 p 85 Bisson amp Vogel 2000 pp 131 132 Hong et al 1994 pp 1841 43 Lead mining Rich 1994 p 11 a b c Riva et al 2012 pp 11 16 Hernberg 2000 p 246 a b Crow 2007 Markowitz amp Rosner 2000 p 37 More et al 2017 American Geophysical Union 2017 Centers for Disease Control and Prevention 1997 Rich 1994 p 117 Rich 1994 p 17 Rich 1994 pp 91 92 United States Geological Survey 2005 Zhang et al 2012 pp 2261 2273 Tolliday 2014 Guberman 2016 pp 42 14 15 Graedel 2010 a b c Thornton Rautiu amp Brush 2001 p 56 a b Davidson et al 2014 p 6 a b c d Davidson et al 2014 p 17 Thornton Rautiu amp Brush 2001 p 51 Davidson et al 2014 pp 11 12 Thornton Rautiu amp Brush 2001 pp 51 52 Davidson et al 2014 p 25 a b c d Primary Lead Refining Pauling 1947 Davidson et al 2014 p 34 Davidson et al 2014 p 23 Thornton Rautiu amp Brush 2001 pp 52 53 United States Environmental Protection Agency 2010 p 1 a b Thornton Rautiu amp Brush 2001 p 57 Street amp Alexander 1998 p 181 Evans 1908 pp 133 179 Baird amp Cann 2012 pp 537 538 543 547 California Department of Fish and Wildlife Parker 2005 pp 194 195 Krestovnikoff amp Halls 2006 p 70 Street amp Alexander 1998 p 182 Jensen 2013 p 136 Think Lead research Weatherings to Parapets Lead garden ornaments 2016 Putnam 2003 p 216 Copper Development Association a b Rich 1994 p 101 Guruswamy 2000 p 31 Audsley 1965 pp 250 251 Palmieri 2006 pp 412 413 National Council on Radiation Protection and Measurements 2004 p 16 Thornton Rautiu amp Brush 2001 p 7 Tucek Carlsson amp Wider 2006 p 1590 Concordia University 2016 Toxicological Profile for Lead 2007 pp 5 6 Progressive Dynamics Inc Olinsky Paul 2013 Gulbinska 2014 Rich 1994 pp 133 134 Zhao 2008 p 440 Beiner et al 2015 Szczepanowska 2013 pp 84 85 Burleson 2001 p 23 Insight Explorer amp IPEN 2016 Singh 2017 Ismawati et al 2013 p 2 Zweifel 2009 p 438 Wilkes et al 2005 p 106 Randerson 2002 Nriagu amp Kim 2000 pp 37 41 Amstock 1997 pp 116 119 Rogalski 2010 pp 485 541 Lead 695912 World Health Organization 2018 Bouchard et al 2009 World Health Organization 2000 pp 149 153 Emsley 2011 pp 280 621 255 a b Luckey amp Venugopal 1979 pp 177 178 Toxic Substances Portal United States Food and Drug Administration 2015 p 42 National Institute for Occupational Safety and Health a b Occupational Safety and Health Administration a b Rudolph et al 2003 p 369 Dart Hurlbut amp Boyer Hassen 2004 p 1426 Kosnett 2006 p 238 Cohen Trotzky amp Pincus 1981 pp 904 906 Navas Acien 2007 Sokol 2005 p 133 passim Mycyk Hryhorczuk amp Amitai 2005 p 462 Liu et al 2015 pp 1869 1874 Schoeters et al 2008 pp 168 175 Tarrago 2012 p 16 Toxicological Profile for Lead 2007 p 4 Bremner 2002 p 101 Agency for Toxic Substances and Disease Registry Thornton Rautiu amp Brush 2001 p 17 Moore 1977 pp 109 115 Wiberg Wiberg amp Holleman 2001 p 914 Tarrago 2012 p 11 Centers for Disease Control and Prevention 2015 Lead Pb Air Pollution epa gov United States Environmental Protection Agency 8 July 2022 Retrieved 22 July 2022 As a result of EPA s regulatory efforts levels of lead in the air nationally decreased by 86 percent between 2010 and 2020 NAAQS Table epa gov United States Environmental Protection Agency 5 April 2022 Retrieved 22 July 2022 National Ambient Air Quality Standards 40 CFR part 50 for six principal pollutants Lead Trends epa gov United States Environmental Protection Agency 1 June 2022 Wani Ara amp Usman 2015 pp 57 58 Castellino N Sannolo N Castellino P 1994 Inorganic Lead Exposure and Intoxications CRC Press p 86 ISBN 9780873719971 Archived from the original on 5 November 2017 Hesami Reza Salimi Azam Ghaderian Seyed Majid 10 January 2018 Lead zinc and cadmium uptake accumulation and phytoremediation by plants growing around Tang e Douzan lead zinc mine Iran Environmental Science and Pollution Research 25 9 8701 8714 doi 10 1007 s11356 017 1156 y ISSN 0944 1344 PMID 29322395 S2CID 3938066 Mielke Howard W Reagan Patrick L February 1998 Soil Is an Important Pathway of Human Lead Exposure Environmental Health Perspectives 106 Suppl 1 217 229 doi 10 2307 3433922 ISSN 0091 6765 JSTOR 3433922 PMC 1533263 PMID 9539015 a b University Stanford 24 September 2019 Lead found in turmeric Stanford News Retrieved 25 September 2019 Researchers find lead in turmeric phys org Retrieved 25 September 2019 Maximum Permitted Concentration of Certain Metals Present in Specified Foods www elegislation gov hk Retrieved 15 April 2020 Consumer Reports urges dark chocolate makers to reduce lead cadmium levels www yahoo com Retrieved 28 January 2023 Dark chocolate is high in cadmium and lead How much is safe to eat Lead in Consumer Products Sources of Lead CDC www cdc gov 1 February 2022 Retrieved 16 June 2022 Prasad 2010 pp 651 652 Masters Trevor amp Katzung 2008 pp 481 483 a b United Nations Environment Programme 2010 p 4 Renfrew Daniel 2019 Life without lead contamination crisis and hope in Uruguay Oakland California p 8 ISBN 978 0 520 96824 0 OCLC 1102765674 a b Trace element emission 2012 United Nations Environment Programme 2010 p 6 Assi et al 2016 World Health Organization 1995 UK Marine SACs Project 1999 United Nations Environment Programme 2010 p 9 McCoy 2017 Cama 2017 Layton 2017 Hauser 2017 pp 49 60 Lauwerys amp Hoet 2001 pp 115 116 117 Lead Poisoning A Historical Perspective Auer et al 2016 p 4 Petzel Juuti amp Sugimoto 2004 pp 122 124 Deltares amp Netherlands Organisation for Applied Scientific Research 2016 Agency for Toxic Substances and Disease Registry 2017 Grandjean 1978 pp 303 321 a b Levin et al 2008 p 1288 Duda 1996 p 242 Marino et al 1990 pp 1183 1185 Schoch 1996 p 111 United States Environmental Protection Agency 2000 Lead in Waste 2016 United States Environmental Protection Agency 2005 p I 1 United States Environmental Protection Agency 2005 p III 5 III 6 Freeman 2012 pp a20 a21 Young 2012 Acton 2013 pp 94 95 Park et al 2011 pp 162 174 Bibliography Edit This article was submitted to WikiJournal of Science for external academic peer review in 2017 reviewer reports The updated content was reintegrated into the Wikipedia page under a CC BY SA 3 0 license 2018 The version of record as reviewed is Mikhail Boldyrev et al 3 July 2018 Lead properties history and applications PDF WikiJournal of Science 1 2 7 doi 10 15347 WJS 2018 007 ISSN 2470 6345 Wikidata Q56050531 Acton Q A ed 2013 Issues in Global Environment Pollution and Waste Management 2012 Edition ScholarlyEditions ISBN 978 1 4816 4665 9 Agency for Toxic Substances and Disease Registry Information for the Community Lead Toxicity MP4 webcast 82 MB Retrieved 11 February 2017 Agency for Toxic Substances and 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