Lead

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This article is about the metal. Lead_sentence_0

For other uses, see Lead (disambiguation). Lead_sentence_1

Lead is a chemical element with the symbol Pb (from the Latin plumbum) and atomic number 82. Lead_sentence_2

It is a heavy metal that is denser than most common materials. Lead_sentence_3

Lead is soft and malleable, and also has a relatively low melting point. Lead_sentence_4

When freshly cut, lead is silvery with a hint of blue; it tarnishes to a dull gray color when exposed to air. Lead_sentence_5

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_sentence_6

Lead is a relatively unreactive post-transition metal. Lead_sentence_7

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. Lead_sentence_8

Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Lead_sentence_9

Exceptions are mostly limited to organolead compounds. Lead_sentence_10

Like the lighter members of the group, lead tends to bond with itself; it can form chains and polyhedral structures. Lead_sentence_11

Lead is easily extracted from its ores; prehistoric people in Western Asia knew of it. Lead_sentence_12

Galena is a principal ore of lead which often bears silver. Lead_sentence_13

Interest in silver helped initiate widespread extraction and use of lead in ancient Rome. Lead_sentence_14

Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. Lead_sentence_15

In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead_sentence_16

Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. Lead_sentence_17

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_sentence_18

In the late 19th century, lead's toxicity was recognized, and its use has since been phased out of many applications. Lead_sentence_19

However, many countries still allow the sale of products that expose humans to lead, including some types of paints and bullets. Lead_sentence_20

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, such as brain damage and behavioral problems. Lead_sentence_21

Physical properties Lead_section_0

Atomic Lead_section_1

A lead atom has 82 electrons, arranged in an electron configuration of Xe4f5d6s6p. Lead_sentence_22

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. Lead_sentence_23

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. Lead_sentence_24

The similarity of ionization energies is caused by the lanthanide contraction—the decrease in element radii from lanthanum (atomic number 57) to lutetium (71), and the relatively small radii of the elements from hafnium (72) onwards. Lead_sentence_25

This is due to poor shielding of the nucleus by the lanthanide 4f electrons. Lead_sentence_26

The sum of the first four ionization energies of lead exceeds that of tin, contrary to what periodic trends would predict. Lead_sentence_27

Relativistic effects, which become significant in heavier atoms, contribute to this behavior. Lead_sentence_28

One such effect is the inert pair effect: the 6s electrons of lead become reluctant to participate in bonding, making the distance between nearest atoms in crystalline lead unusually long. Lead_sentence_29

Lead's lighter carbon group congeners form stable or metastable allotropes with the tetrahedrally coordinated and covalently bonded diamond cubic structure. Lead_sentence_30

The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp orbitals. Lead_sentence_31

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. Lead_sentence_32

Rather than having a diamond cubic structure, lead forms metallic bonds in which only the p-electrons are delocalized and shared between the Pb ions. Lead_sentence_33

Lead consequently has a face-centered cubic structure like the similarly sized divalent metals calcium and strontium. Lead_sentence_34

Bulk Lead_section_2

Pure lead has a bright, silvery appearance with a hint of blue. Lead_sentence_35

It tarnishes on contact with moist air and takes on a dull appearance, the hue of which depends on the prevailing conditions. Lead_sentence_36

Characteristic properties of lead include high density, malleability, ductility, and high resistance to corrosion due to passivation. Lead_sentence_37

Lead's close-packed face-centered cubic structure and high atomic weight result in a density of 11.34 g/cm, which is greater than that of common metals such as iron (7.87 g/cm), copper (8.93 g/cm), and zinc (7.14 g/cm). Lead_sentence_38

This density is the origin of the idiom to go over like a lead balloon. Lead_sentence_39

Some rarer metals are denser: tungsten and gold are both at 19.3 g/cm, and osmium—the densest metal known—has a density of 22.59 g/cm, almost twice that of lead. Lead_sentence_40

Lead is a very soft metal with a Mohs hardness of 1.5; it can be scratched with a fingernail. Lead_sentence_41

It is quite malleable and somewhat ductile. Lead_sentence_42

The bulk modulus of lead—a measure of its ease of compressibility—is 45.8 GPa. Lead_sentence_43

In comparison, that of aluminium is 75.2 GPa; copper 137.8 GPa; and mild steel 160–169 GPa. Lead_sentence_44

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. Lead_sentence_45

The melting point of lead—at 327.5 °C (621.5 °F)—is very low compared to most metals. Lead_sentence_46

Its boiling point of 1749 °C (3180 °F) is the lowest among the carbon group elements. Lead_sentence_47

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). Lead_sentence_48

Lead is a superconductor at temperatures lower than 7.19 K; this is the highest critical temperature of all type-I superconductors and the third highest of the elemental superconductors. Lead_sentence_49

Isotopes Lead_section_3

Main article: Isotopes of lead Lead_sentence_50

Natural lead consists of four stable isotopes with mass numbers of 204, 206, 207, and 208, and traces of five short-lived radioisotopes. Lead_sentence_51

The high number of isotopes is consistent with lead's atomic number being even. Lead_sentence_52

Lead has a magic number of protons (82), for which the nuclear shell model accurately predicts an especially stable nucleus. Lead_sentence_53

Lead-208 has 126 neutrons, another magic number, which may explain why lead-208 is extraordinarily stable. Lead_sentence_54

With its high atomic number, lead is the heaviest element whose natural isotopes are regarded as stable; lead-208 is the heaviest stable nucleus. Lead_sentence_55

(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.) Lead_sentence_56

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 10 to 10 years (at least 10 times the current age of the universe). Lead_sentence_57

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. Lead_sentence_58

These decay chains are called the uranium chain, the actinium chain, and the thorium chain. Lead_sentence_59

Their isotopic concentrations in a natural rock sample depends greatly on the presence of these three parent uranium and thorium isotopes. Lead_sentence_60

For example, the relative abundance of lead-208 can range from 52% in normal samples to 90% in thorium ores; for this reason, the standard atomic weight of lead is given to only one decimal place. Lead_sentence_61

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. Lead_sentence_62

As uranium decays into lead, their relative amounts change; this is the basis for uranium–lead dating. Lead_sentence_63

Lead-207 exhibits nuclear magnetic resonance, a property that has been used to study its compounds in solution and solid state, including in human body. Lead_sentence_64

Apart from the stable isotopes, which make up almost all lead that exists naturally, there are trace quantities of a few radioactive isotopes. Lead_sentence_65

One of them is lead-210; although it has a half-life of only 22.3 years, 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_sentence_66

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. Lead_sentence_67

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_sentence_68

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). Lead_sentence_69

In total, 43 lead isotopes have been synthesized, with mass numbers 178–220. Lead_sentence_70

Lead-205 is the most stable radioisotope, with a half-life of around 1.73×10 years. Lead_sentence_71

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. Lead_sentence_72

Chemistry Lead_section_4

Bulk lead exposed to moist air forms a protective layer of varying composition. Lead_sentence_73

Lead(II) carbonate is a common constituent; the sulfate or chloride may also be present in urban or maritime settings. Lead_sentence_74

This layer makes bulk lead effectively chemically inert in the air. Lead_sentence_75

Finely powdered lead, as with many metals, is pyrophoric, and burns with a bluish-white flame. Lead_sentence_76

Fluorine reacts with lead at room temperature, forming lead(II) fluoride. Lead_sentence_77

The reaction with chlorine is similar but requires heating, as the resulting chloride layer diminishes the reactivity of the elements. Lead_sentence_78

Molten lead reacts with the chalcogens to give lead(II) chalcogenides. Lead_sentence_79

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. Lead_sentence_80

Organic acids, such as acetic acid, dissolve lead in the presence of oxygen. Lead_sentence_81

Concentrated alkalis will dissolve lead and form plumbites. Lead_sentence_82

Inorganic compounds Lead_section_5

See also: Compounds of lead Lead_sentence_83

Lead shows two main oxidation states: +4 and +2. Lead_sentence_84

The tetravalent state is common for the carbon group. Lead_sentence_85

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. Lead_sentence_86

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. Lead_sentence_87

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. Lead_sentence_88

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. Lead_sentence_89

In these, the 6s and 6p orbitals remain similarly sized and sp hybridization is still energetically favorable. Lead_sentence_90

Lead, like carbon, is predominantly tetravalent in such compounds. Lead_sentence_91

There is a relatively large difference in the electronegativity of lead(II) at 1.87 and lead(IV) at 2.33. Lead_sentence_92

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. Lead_sentence_93

Lead(II) Lead_section_6

Lead(II) compounds are characteristic of the inorganic chemistry of lead. Lead_sentence_94

Even strong oxidizing agents like fluorine and chlorine react with lead to give only PbF2 and PbCl2. Lead_sentence_95

Lead(II) ions are usually colorless in solution, and partially hydrolyze to form Pb(OH) and finally [Pb4(OH)4] (in which the hydroxyl ions act as bridging ligands), but are not reducing agents as tin(II) ions are. Lead_sentence_96

Techniques for identifying the presence of the Pb ion in water generally rely on the precipitation of lead(II) chloride using dilute hydrochloric acid. Lead_sentence_97

As the chloride salt is sparingly soluble in water, in very dilute solutions the precipitation of lead(II) sulfide is achieved by bubbling hydrogen sulfide through the solution. Lead_sentence_98

Lead monoxide exists in two polymorphs, litharge α-PbO (red) and massicot β-PbO (yellow), the latter being stable only above around 488 °C. Lead_sentence_99

Litharge is the most commonly used inorganic compound of lead. Lead_sentence_100

There is no lead(II) hydroxide; increasing the pH of solutions of lead(II) salts leads to hydrolysis and condensation. Lead_sentence_101

Lead commonly reacts with heavier chalcogens. Lead_sentence_102

Lead sulfide is a semiconductor, a photoconductor, and an extremely sensitive infrared radiation detector. Lead_sentence_103

The other two chalcogenides, lead selenide and lead telluride, are likewise photoconducting. Lead_sentence_104

They are unusual in that their color becomes lighter going down the group. Lead_sentence_105

Lead dihalides are well-characterized; this includes the diastatide and mixed halides, such as PbFCl. Lead_sentence_106

The relative insolubility of the latter forms a useful basis for the gravimetric determination of fluorine. Lead_sentence_107

The difluoride was the first solid ionically conducting compound to be discovered (in 1834, by Michael Faraday). Lead_sentence_108

The other dihalides decompose on exposure to ultraviolet or visible light, especially the diiodide. Lead_sentence_109

Many lead(II) pseudohalides are known, such as the cyanide, cyanate, and thiocyanate. Lead_sentence_110

Lead(II) forms an extensive variety of halide coordination complexes, such as [PbCl4], [PbCl6], and the [Pb2Cl9]n chain anion. Lead_sentence_111

Lead(II) sulfate is insoluble in water, like the sulfates of other heavy divalent cations. Lead_sentence_112

Lead(II) nitrate and lead(II) acetate are very soluble, and this is exploited in the synthesis of other lead compounds. Lead_sentence_113

Lead(IV) Lead_section_7

Few inorganic lead(IV) compounds are known. Lead_sentence_114

They are only formed in highly oxidizing solutions and do not normally exist under standard conditions. Lead_sentence_115

Lead(II) oxide gives a mixed oxide on further oxidation, Pb3O4. Lead_sentence_116

It is described as lead(II,IV) oxide, or structurally 2PbO·PbO2, and is the best-known mixed valence lead compound. Lead_sentence_117

Lead dioxide is a strong oxidizing agent, capable of oxidizing hydrochloric acid to chlorine gas. Lead_sentence_118

This is because the expected PbCl4 that would be produced is unstable and spontaneously decomposes to PbCl2 and Cl2. Lead_sentence_119

Analogously to lead monoxide, lead dioxide is capable of forming plumbate anions. Lead_sentence_120

Lead disulfide and lead diselenide are only stable at high pressures. Lead_sentence_121

Lead tetrafluoride, a yellow crystalline powder, is stable, but less so than the difluoride. Lead_sentence_122

Lead tetrachloride (a yellow oil) decomposes at room temperature, lead tetrabromide is less stable still, and the existence of lead tetraiodide is questionable. Lead_sentence_123

Other oxidation states Lead_section_8

See also: Plumbide Lead_sentence_124

Some lead compounds exist in formal oxidation states other than +4 or +2. Lead_sentence_125

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. Lead_sentence_126

The same applies for lead(I), which can be found in such radical species. Lead_sentence_127

Numerous mixed lead(II,IV) oxides are known. Lead_sentence_128

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. Lead_sentence_129

A further sesquioxide, Pb2O3, can be obtained at high pressure, along with several non-stoichiometric phases. Lead_sentence_130

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. Lead_sentence_131

Negative oxidation states can occur as Zintl phases, as either free lead anions, as in Ba2Pb, with lead formally being lead(−IV), or in oxygen-sensitive ring-shaped or polyhedral cluster ions such as the trigonal bipyramidal Pb5 ion, where two lead atoms are lead(−I) and three are lead(0). Lead_sentence_132

In such anions, each atom is at a polyhedral vertex and contributes two electrons to each covalent bond along an edge from their sp hybrid orbitals, the other two being an external lone pair. Lead_sentence_133

They may be made in liquid ammonia via the reduction of lead by sodium. Lead_sentence_134

Organolead Lead_section_9

Main article: Organolead compound Lead_sentence_135

Lead can form multiply-bonded chains, a property it shares with its lighter homologs in the carbon group. Lead_sentence_136

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. Lead_sentence_137

With itself, lead can build metal–metal bonds of an order up to three. Lead_sentence_138

With carbon, lead forms organolead compounds similar to, but generally less stable than, typical organic compounds (due to the Pb–C bond being rather weak). Lead_sentence_139

This makes the organometallic chemistry of lead far less wide-ranging than that of tin. Lead_sentence_140

Lead predominantly forms organolead(IV) compounds, even when starting with inorganic lead(II) reactants; very few organolead(II) compounds are known. Lead_sentence_141

The most well-characterized exceptions are Pb[CH(SiMe3)2]2 and Pb(η-C5H5)2. Lead_sentence_142

The lead analog of the simplest organic compound, methane, is plumbane. Lead_sentence_143

Plumbane may be obtained in a reaction between metallic lead and atomic hydrogen. Lead_sentence_144

Two simple derivatives, tetramethyllead and tetraethyllead, are the best-known organolead compounds. Lead_sentence_145

These compounds are relatively stable: tetraethyllead only starts to decompose if heated or if exposed to sunlight or ultraviolet light. Lead_sentence_146

With sodium metal, lead readily forms an equimolar alloy that reacts with alkyl halides to form organometallic compounds such as tetraethyllead. Lead_sentence_147

The oxidizing nature of many organolead compounds is usefully exploited: lead tetraacetate is an important laboratory reagent for oxidation in organic synthesis. Lead_sentence_148

Tetraethyllead, once added to gasoline, was produced in larger quantities than any other organometallic compound. Lead_sentence_149

Other organolead compounds are less chemically stable. Lead_sentence_150

For many organic compounds, a lead analog does not exist. Lead_sentence_151

Origin and occurrence Lead_section_10

Lead_table_general_0

Solar System abundancesLead_table_caption_0
Atomic

numberLead_header_cell_0_0_0

ElementLead_header_cell_0_0_1 Relative

amountLead_header_cell_0_0_2

42Lead_cell_0_1_0 MolybdenumLead_cell_0_1_1 0.798Lead_cell_0_1_2
46Lead_cell_0_2_0 PalladiumLead_cell_0_2_1 0.440Lead_cell_0_2_2
50Lead_cell_0_3_0 TinLead_cell_0_3_1 1.146Lead_cell_0_3_2
78Lead_cell_0_4_0 PlatinumLead_cell_0_4_1 0.417Lead_cell_0_4_2
80Lead_cell_0_5_0 MercuryLead_cell_0_5_1 0.127Lead_cell_0_5_2
82Lead_cell_0_6_0 LeadLead_cell_0_6_1 1Lead_cell_0_6_2
90Lead_cell_0_7_0 ThoriumLead_cell_0_7_1 0.011Lead_cell_0_7_2
92Lead_cell_0_8_0 UraniumLead_cell_0_8_1 0.003Lead_cell_0_8_2

In space Lead_section_11

Lead's per-particle abundance in the Solar System is 0.121 ppb (parts per billion). Lead_sentence_152

This figure is two and a half times higher than that of platinum, eight times more than mercury, and seventeen times more than gold. Lead_sentence_153

The amount of lead in the universe is slowly increasing as most heavier atoms (all of which are unstable) gradually decay to lead. Lead_sentence_154

The abundance of lead in the Solar System since its formation 4.5 billion years ago has increased by about 0.75%. Lead_sentence_155

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. Lead_sentence_156

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. Lead_sentence_157

The two main modes of capture are the s- and r-processes. Lead_sentence_158

In the s-process (s is for "slow"), captures are separated by years or decades, allowing less stable nuclei to undergo beta decay. Lead_sentence_159

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. Lead_sentence_160

Further captures result in lead-206, lead-207, and lead-208. Lead_sentence_161

On capturing another neutron, lead-208 becomes lead-209, which quickly decays into bismuth-209. Lead_sentence_162

On capturing another neutron, bismuth-209 becomes bismuth-210, and this beta decays to polonium-210, which alpha decays to lead-206. Lead_sentence_163

The cycle hence ends at lead-206, lead-207, lead-208, and bismuth-209. Lead_sentence_164

In the r-process (r is for "rapid"), captures happen faster than nuclei can decay. Lead_sentence_165

This occurs in environments with a high neutron density, such as a supernova or the merger of two neutron stars. Lead_sentence_166

The neutron flux involved may be on the order of 10 neutrons per square centimeter per second. Lead_sentence_167

The r-process does not form as much lead as the s-process. Lead_sentence_168

It tends to stop once neutron-rich nuclei reach 126 neutrons. Lead_sentence_169

At this point, the neutrons are arranged in complete shells in the atomic nucleus, and it becomes harder to energetically accommodate more of them. Lead_sentence_170

When the neutron flux subsides, these nuclei beta decay into stable isotopes of osmium, iridium, and platinum. Lead_sentence_171

On Earth Lead_section_12

Lead is classified as a chalcophile under the Goldschmidt classification, meaning it is generally found combined with sulfur. Lead_sentence_172

It rarely occurs in its native, metallic form. Lead_sentence_173

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. Lead_sentence_174

This accounts for lead's relatively high crustal abundance of 14 ppm; it is the 38th most abundant element in the crust. Lead_sentence_175

The main lead-bearing mineral is galena (PbS), which is mostly found with zinc ores. Lead_sentence_176

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. Lead_sentence_177

Arsenic, tin, antimony, silver, gold, copper, and bismuth are common impurities in lead minerals. Lead_sentence_178

World lead resources exceed two billion tons. Lead_sentence_179

Significant deposits are located in Australia, China, Ireland, Mexico, Peru, Portugal, Russia, and the United States. Lead_sentence_180

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. Lead_sentence_181

Typical background concentrations of lead do not exceed 0.1 μg/m in the atmosphere; 100 mg/kg in soil; and 5 μg/L in freshwater and seawater. Lead_sentence_182

Etymology Lead_section_13

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). Lead_sentence_183

The Old English word is derived from the hypothetical reconstructed Proto-Germanic *lauda- ("lead"). Lead_sentence_184

According to linguistic theory, this word bore descendants in multiple Germanic languages of exactly the same meaning. Lead_sentence_185

There is no consensus on the origin of the Proto-Germanic *lauda-. Lead_sentence_186

One hypothesis suggests it is derived from Proto-Indo-European *lAudh- ("lead"; capitalization of the vowel is equivalent to the macron). Lead_sentence_187

Another hypothesis suggests it is borrowed from Proto-Celtic *ɸloud-io- ("lead"). Lead_sentence_188

This word is related to the Latin plumbum, which gave the element its chemical symbol Pb. Lead_sentence_189

The word *ɸloud-io- is thought to be the origin of Proto-Germanic *bliwa- (which also means "lead"), from which stemmed the German Blei. Lead_sentence_190

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"). Lead_sentence_191

History Lead_section_14

Prehistory and early history Lead_section_15

Metallic lead beads dating back to 7000–6500 BCE have been found in Asia Minor and may represent the first example of metal smelting. Lead_sentence_192

At that time lead had few (if any) applications due to its softness and dull appearance. Lead_sentence_193

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). Lead_sentence_194

The Ancient Egyptians were the first to use lead minerals in cosmetics, an application that spread to Ancient Greece and beyond; the Egyptians may have used lead for sinkers in fishing nets, glazes, glasses, enamels, and for ornaments. Lead_sentence_195

Various civilizations of the Fertile Crescent used lead as a writing material, as currency, and as a construction material. Lead_sentence_196

Lead was used in the Ancient Chinese royal court as a stimulant, as currency, and as a contraceptive; the Indus Valley civilization and the Mesoamericans used it for making amulets; and the eastern and southern African peoples used lead in wire drawing. Lead_sentence_197

Classical era Lead_section_16

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. Lead_sentence_198

These three regions collectively dominated production of mined lead until c. 1200 BCE. Lead_sentence_199

Beginning circa 2000 BCE, the Phoenicians worked deposits in the Iberian peninsula; by 1600 BCE, lead mining existed in Cyprus, Greece, and Sardinia. Lead_sentence_200

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. Lead_sentence_201

Like their predecessors, the Romans obtained lead mostly as a by-product of silver smelting. Lead_sentence_202

Lead mining occurred in Central Europe, Britain, the Balkans, Greece, Anatolia, and Hispania, the latter accounting for 40% of world production. Lead_sentence_203

Lead tablets were commonly used as a material for letters. Lead_sentence_204

Lead coffins, cast in flat sand forms, with interchangeable motifs to suit the faith of the deceased were used in ancient Judea. Lead_sentence_205

Lead was used to make sling bullets from the 5th century BC. Lead_sentence_206

In Roman times, lead sling bullets were amply used, and were effective at a distance of between 100 and 150 meters. Lead_sentence_207

The Balearic slingers, used as mercenaries in Carthaginian and Roman armies, were famous for their shooting distance and accuracy. Lead_sentence_208

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". Lead_sentence_209

Its ease of working and resistance to corrosion ensured its widespread use in other applications, including pharmaceuticals, roofing, currency, and warfare. Lead_sentence_210

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. Lead_sentence_211

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. Lead_sentence_212

The Roman author Vitruvius reported the health dangers of lead and modern writers have suggested that lead poisoning played a major role in the decline of the Roman Empire. Lead_sentence_213

Other researchers have criticized such claims, pointing out, for instance, that not all abdominal pain is caused by lead poisoning. Lead_sentence_214

According to archaeological research, Roman lead pipes increased lead levels in tap water but such an effect was "unlikely to have been truly harmful". Lead_sentence_215

When lead poisoning did occur, victims were called "saturnine", dark and cynical, after the ghoulish father of the gods, Saturn. Lead_sentence_216

By association, lead was considered the father of all metals. Lead_sentence_217

Its status in Roman society was low as it was readily available and cheap. Lead_sentence_218

Confusion with tin and antimony Lead_section_17

During the classical era (and even up to the 17th century), tin was often not distinguished from lead: Romans called lead plumbum nigrum ("black lead"), and tin plumbum candidum ("bright lead"). Lead_sentence_219

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". Lead_sentence_220

To add to the confusion, lead bore a close relation to antimony: both elements commonly occur as sulfides (galena and stibnite), often together. Lead_sentence_221

Pliny incorrectly wrote that stibnite would give lead on heating, instead of antimony. Lead_sentence_222

In countries such as Turkey and India, the originally Persian name surma came to refer to either antimony sulfide or lead sulfide, and in some languages, such as Russian, gave its name to antimony (сурьма). Lead_sentence_223

Middle Ages and the Renaissance Lead_section_18

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. Lead_sentence_224

The largest production of lead occurred in South and East Asia, especially China and India, where lead mining grew rapidly. Lead_sentence_225

In Europe, lead production began to increase in the 11th and 12th centuries, when it was again used for roofing and piping. Lead_sentence_226

Starting in the 13th century, lead was used to create stained glass. Lead_sentence_227

In the European and Arabian traditions of alchemy, lead (symbol in the European tradition) 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. Lead_sentence_228

During the period, lead was used increasingly for adulterating wine. Lead_sentence_229

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. Lead_sentence_230

Lead was a key material in parts of the printing press,and lead dust was commonly inhaled by print workers, causing lead poisoning. Lead_sentence_231

Despite being more expensive than iron, lead also became the chief material for making bullets for firearms. Lead_sentence_232

It was 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. Lead_sentence_233

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. Lead_sentence_234

This practice later expanded to white wigs and eyeliners, and only faded out with the French Revolution in the late 18th century. Lead_sentence_235

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. Lead_sentence_236

The white faces of women "came to represent their feminine virtue as Japanese women", with lead commonly used in the whitener. Lead_sentence_237

Outside Europe and Asia Lead_section_19

In the New World, lead production was recorded soon after the arrival of European settlers. Lead_sentence_238

The earliest record dates to 1621 in the English Colony of Virginia, fourteen years after its foundation. Lead_sentence_239

In Australia, the first mine opened by colonists on the continent was a lead mine, in 1841. Lead_sentence_240

In Africa, lead mining and smelting were known in the Benue Trough and the lower Congo Basin, where lead was used for trade with Europeans, and as a currency by the 17th century, well before the scramble for Africa. Lead_sentence_241

Industrial Revolution Lead_section_20

In the second half of the 18th century, Britain, and later continental Europe and the United States, experienced the Industrial Revolution. Lead_sentence_242

This was the first time during which lead production rates exceeded those of Rome. Lead_sentence_243

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. Lead_sentence_244

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. Lead_sentence_245

A great share of the demand for lead came from plumbing and painting—lead paints were in regular use. Lead_sentence_246

At this time, more (working class) people were exposed to the metal and lead poisoning cases escalated. Lead_sentence_247

This led to research into the effects of lead intake. Lead_sentence_248

Lead was proven to be more dangerous in its fume form than as a solid metal. Lead_sentence_249

Lead poisoning and gout were linked; British physician Alfred Baring Garrod noted a third of his gout patients were plumbers and painters. Lead_sentence_250

The effects of chronic ingestion of lead, including mental disorders, were also studied in the 19th century. Lead_sentence_251

The first laws aimed at decreasing lead poisoning in factories were enacted during the 1870s and 1880s in the United Kingdom. Lead_sentence_252

Modern era Lead_section_21

Further evidence of the threat that lead posed to humans was discovered in the late 19th and early 20th centuries. Lead_sentence_253

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. Lead_sentence_254

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. Lead_sentence_255

Most European countries banned lead paint—commonly used because of its opacity and water resistance—for interiors by 1930. Lead_sentence_256

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. Lead_sentence_257

It was phased out in the United States and the European Union by 2000. Lead_sentence_258

In the 1970s, the United States and Western European countries introduced legislation to reduce lead air pollution. Lead_sentence_259

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%. Lead_sentence_260

The main product made of lead by the end of the 20th century was the lead–acid battery. Lead_sentence_261

From 1960 to 1990, lead output in the Western Bloc grew by about 31%. Lead_sentence_262

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. Lead_sentence_263

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. Lead_sentence_264

As was the case during European industrialization, lead has had a negative effect on health in China. Lead_sentence_265

Production Lead_section_22

As of 2014, production of lead is increasing worldwide due to its use in lead–acid batteries. Lead_sentence_266

There are two major categories of production: primary from mined ores, and secondary from scrap. Lead_sentence_267

In 2014, 4.58 million metric tons came from primary production and 5.64 million from secondary production. Lead_sentence_268

The top three producers of mined lead concentrate in that year were China, Australia, and the United States. Lead_sentence_269

The top three producers of refined lead were China, the United States, and India. Lead_sentence_270

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. Lead_sentence_271

Much of this is in more developed countries (20–150 kg per capita) rather than less developed ones (1–4 kg per capita). Lead_sentence_272

The primary and secondary lead production processes are similar. Lead_sentence_273

Some primary production plants now supplement their operations with scrap lead, and this trend is likely to increase in the future. Lead_sentence_274

Given adequate techniques, lead obtained via secondary processes is indistinguishable from lead obtained via primary processes. Lead_sentence_275

Scrap lead from the building trade is usually fairly clean and is re-melted without the need for smelting, though refining is sometimes needed. Lead_sentence_276

Secondary lead production is therefore cheaper, in terms of energy requirements, than is primary production, often by 50% or more. Lead_sentence_277

Primary Lead_section_23

Most lead ores contain a low percentage of lead (rich ores have a typical content of 3–8%) which must be concentrated for extraction. Lead_sentence_278

During initial processing, ores typically undergo crushing, dense-medium separation, grinding, froth flotation, and drying. Lead_sentence_279

The resulting concentrate, which has a lead content of 30–80% by mass (regularly 50–60%), is then turned into (impure) lead metal. Lead_sentence_280

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. Lead_sentence_281

The latter has become the most common route, though the former is still significant. Lead_sentence_282

Two-stage process Lead_section_24

First, the sulfide concentrate is roasted in air to oxidize the lead sulfide: Lead_sentence_283

Lead_description_list_0

  • 2 PbS(s) + 3 O2(g) → 2 PbO(s) + 2 SO2(g)↑Lead_item_0_0

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. Lead_sentence_284

This impure lead oxide is reduced in a coke-fired blast furnace to the (again, impure) metal: Lead_sentence_285

Lead_description_list_1

  • 2 PbO(s) + C(s) → 2 Pb(s) + CO2(g)↑Lead_item_1_1

Impurities are mostly arsenic, antimony, bismuth, zinc, copper, silver, and gold. Lead_sentence_286

Typically they are removed in a series of pyrometallurgical processes. Lead_sentence_287

The melt is treated in a reverberatory furnace with air, steam, and sulfur, which oxidizes the impurities except for silver, gold, and bismuth. Lead_sentence_288

Oxidized contaminants float to the top of the melt and are skimmed off. Lead_sentence_289

Metallic silver and gold are removed and recovered economically by means of the Parkes process, in which zinc is added to lead. Lead_sentence_290

Zinc, which is immiscible in lead, dissolves the silver and gold. Lead_sentence_291

The zinc solution can be separated from the lead, and the silver and gold retrieved. Lead_sentence_292

De-silvered lead is freed of bismuth by the Betterton–Kroll process, treating it with metallic calcium and magnesium. Lead_sentence_293

The resulting bismuth dross can be skimmed off. Lead_sentence_294

Alternatively to the pyrometallurgical processes, very pure lead can be obtained by processing smelted lead electrolytically using the Betts process. Lead_sentence_295

Anodes of impure lead and cathodes of pure lead are placed in an electrolyte of lead fluorosilicate (PbSiF6). Lead_sentence_296

Once electrical potential is applied, impure lead at the anode dissolves and plates onto the cathode, leaving the majority of the impurities in solution. Lead_sentence_297

This is a high-cost process and thus mostly reserved for refining bullion containing high percentages of impurities. Lead_sentence_298

Direct process Lead_section_25

In this process, lead bullion and slag is obtained directly from lead concentrates. Lead_sentence_299

The lead sulfide concentrate is melted in a furnace and oxidized, forming lead monoxide. Lead_sentence_300

Carbon (as coke or coal gas) is added to the molten charge along with fluxing agents. Lead_sentence_301

The lead monoxide is thereby reduced to metallic lead, in the midst of a slag rich in lead monoxide. Lead_sentence_302

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. Lead_sentence_303

For a low-grade feed, all of the lead can be oxidized to a high-lead slag. Lead_sentence_304

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. Lead_sentence_305

Alternatives Lead_section_26

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. Lead_sentence_306

Hydrometallurgical extraction, in which anodes of impure lead are immersed into an electrolyte and pure lead is deposited onto a cathode, is a technique that may have potential, but is not currently economical except in cases where electricity is very cheap. Lead_sentence_307

Secondary Lead_section_27

Smelting, which is an essential part of the primary production, is often skipped during secondary production. Lead_sentence_308

It is only performed when metallic lead has undergone significant oxidation. Lead_sentence_309

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). Lead_sentence_310

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. Lead_sentence_311

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. Lead_sentence_312

Of the sources of lead for recycling, lead–acid batteries are the most important; lead pipe, sheet, and cable sheathing are also significant. Lead_sentence_313

Applications Lead_section_28

Contrary to popular belief, pencil leads in wooden pencils have never been made from lead. Lead_sentence_314

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). Lead_sentence_315

Elemental form Lead_section_29

Lead metal has several useful mechanical properties, including high density, low melting point, ductility, and relative inertness. Lead_sentence_316

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_sentence_317

Lead's toxicity has led to its phasing out for some uses. Lead_sentence_318

Lead has been used for bullets since their invention in the Middle Ages. Lead_sentence_319

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. Lead_sentence_320

It remains the main material for bullets, alloyed with other metals as hardeners. Lead_sentence_321

Concerns have been raised that lead bullets used for hunting can damage the environment. Lead_sentence_322

Lead's high density and resistance to corrosion have been exploited in a number of related applications. Lead_sentence_323

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. Lead_sentence_324

It is used in scuba diving weight belts to counteract the diver's buoyancy. Lead_sentence_325

In 1993, the base of the Leaning Tower of Pisa was stabilized with 600 tonnes of lead. Lead_sentence_326

Because of its corrosion resistance, lead is used as a protective sheath for underwater cables. Lead_sentence_327

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. Lead_sentence_328

Lead is still used in statues and sculptures, including for armatures. Lead_sentence_329

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. Lead_sentence_330

Lead is added to copper alloys, such as brass and bronze, to improve machinability and for its lubricating qualities. Lead_sentence_331

Being practically insoluble in copper the lead forms solid globules in imperfections throughout the alloy, such as grain boundaries. Lead_sentence_332

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. Lead_sentence_333

Copper alloys with larger concentrations of lead are used in bearings. Lead_sentence_334

The lead provides lubrication, and the copper provides the load-bearing support. Lead_sentence_335

Lead's high density, atomic number, and formability form the basis for use of lead as a barrier that absorbs sound, vibration, and radiation. Lead_sentence_336

Lead has no natural resonance frequencies; as a result, sheet-lead is used as a sound deadening layer in the walls, floors, and ceilings of sound studios. Lead_sentence_337

Organ pipes are often made from a lead alloy, mixed with various amounts of tin to control the tone of each pipe. Lead_sentence_338

Lead is an established shielding material from radiation in nuclear science and in X-ray rooms due to its denseness and high attenuation coefficient. Lead_sentence_339

Molten lead has been used as a coolant for lead-cooled fast reactors. Lead_sentence_340

The largest use of lead in the early 21st century is in lead–acid batteries. Lead_sentence_341

The lead in batteries undergoes no direct contact with humans, so there are fewer toxicity concerns. Lead_sentence_342

People who work in battery production plants may be exposed to lead dust and inhale it.} Lead_sentence_343

The reactions in the battery between lead, lead dioxide, and sulfuric acid provide a reliable source of voltage. Lead_sentence_344

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. Lead_sentence_345

These batteries have lower energy density and charge-discharge efficiency than lithium-ion batteries, but are significantly cheaper. Lead_sentence_346

Lead is used in high voltage power cables as sheathing material to prevent water diffusion into insulation; this use is decreasing as lead is being phased out. Lead_sentence_347

Its use in solder for electronics is also being phased out by some countries to reduce the amount of environmentally hazardous waste. Lead_sentence_348

Lead is one of three metals used in the Oddy test for museum materials, helping detect organic acids, aldehydes, and acidic gases. Lead_sentence_349

Compounds Lead_section_30

In addition to being the main application for lead metal, lead-acid batteries are also the main consumer of lead compounds. Lead_sentence_350

The energy storage/release reaction used in these devices involves lead sulfate and lead dioxide: Lead_sentence_351

Lead_description_list_2

  • Pb(s) + PbO 2(s) + 2H 2SO 4(aq) → 2PbSO 4(s) + 2H 2O(l)Lead_item_2_2

Other applications of lead compounds are very specialized and often fading. Lead_sentence_352

Lead-based coloring agents are used in ceramic glazes and glass, especially for red and yellow shades. Lead_sentence_353

While lead paints are phased out in Europe and North America, they remain in use in less developed countries such as China, India, or Indonesia. Lead_sentence_354

Lead tetraacetate and lead dioxide are used as oxidizing agents in organic chemistry. Lead_sentence_355

Lead is frequently used in the polyvinyl chloride coating of electrical cords. Lead_sentence_356

It can be used to treat candle wicks to ensure a longer, more even burn. Lead_sentence_357

Because of its toxicity, European and North American manufacturers use alternatives such as zinc. Lead_sentence_358

Lead glass is composed of 12–28% lead oxide, changing its optical characteristics and reducing the transmission of ionizing radiation. Lead_sentence_359

Lead-based semiconductors such as lead telluride and lead selenide are used in photovoltaic cells and infrared detectors. Lead_sentence_360

Biological effects Lead_section_31

Main article: Lead poisoning Lead_sentence_361

Lead_table_infobox_1

LeadLead_table_caption_1
HazardsLead_header_cell_1_0_0
GHS pictogramsLead_cell_1_1_0 Lead_cell_1_1_1
GHS Signal wordLead_cell_1_2_0 DangerLead_cell_1_2_1
GHS hazard statementsLead_cell_1_3_0 H302, H332, H351, H360Df, H373, H410Lead_cell_1_3_1
GHS precautionary statementsLead_cell_1_4_0 P201, P261, P273, P304, P340, P312, P308, P313, P391Lead_cell_1_4_1
NFPA 704 (fire diamond)Lead_cell_1_5_0 0

2 0Lead_cell_1_5_1

Lead has no confirmed biological role, and there is no confirmed safe level of lead exposure. Lead_sentence_362

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". Lead_sentence_363

Its prevalence in the human body—at an adult average of 120 mg—is nevertheless exceeded only by zinc (2500 mg) and iron (4000 mg) among the heavy metals. Lead_sentence_364

Lead salts are very efficiently absorbed by the body. Lead_sentence_365

A small amount of lead (1%) is stored in bones; the rest is excreted in urine and feces within a few weeks of exposure. Lead_sentence_366

Only about a third of lead is excreted by a child. Lead_sentence_367

Continual exposure may result in the bioaccumulation of lead. Lead_sentence_368

Toxicity Lead_section_32

Lead is a highly poisonous metal (whether inhaled or swallowed), affecting almost every organ and system in the human body. Lead_sentence_369

At airborne levels of 100 mg/m, it is immediately dangerous to life and health. Lead_sentence_370

Most ingested lead is absorbed into the bloodstream. Lead_sentence_371

The primary cause of its toxicity is its predilection for interfering with the proper functioning of enzymes. Lead_sentence_372

It does so by binding to the sulfhydryl groups found on many enzymes, or mimicking and displacing other metals which act as cofactors in many enzymatic reactions. Lead_sentence_373

Among the essential metals that lead interacts with are calcium, iron, and zinc. Lead_sentence_374

High levels of calcium and iron tend to provide some protection from lead poisoning; low levels cause increased susceptibility. Lead_sentence_375

Effects Lead_section_33

Lead can cause severe damage to the brain and kidneys and, ultimately, death. Lead_sentence_376

By mimicking calcium, lead can cross the blood–brain barrier. Lead_sentence_377

It degrades the myelin sheaths of neurons, reduces their numbers, interferes with neurotransmission routes, and decreases neuronal growth. Lead_sentence_378

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. Lead_sentence_379

This causes ineffective heme synthesis and microcytic anemia. Lead_sentence_380

Symptoms of lead poisoning include nephropathy, colic-like abdominal pains, and possibly weakness in the fingers, wrists, or ankles. Lead_sentence_381

Small blood pressure increases, particularly in middle-aged and older people, may be apparent and can cause anemia. Lead_sentence_382

Several studies, mostly cross-sectional, found an association between increased lead exposure and decreased heart rate variability. Lead_sentence_383

In pregnant women, high levels of exposure to lead may cause miscarriage. Lead_sentence_384

Chronic, high-level exposure has been shown to reduce fertility in males. Lead_sentence_385

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. Lead_sentence_386

Early childhood exposure has been linked with an increased risk of sleep disturbances and excessive daytime drowsiness in later childhood. Lead_sentence_387

High blood levels are associated with delayed puberty in girls. Lead_sentence_388

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, a hypothesis which is not universally accepted. Lead_sentence_389

Exposure sources Lead_section_34

Lead exposure is a global issue since lead mining and smelting, and battery manufacturing/disposal/recycling, are common in many countries. Lead_sentence_390

Lead enters the body via inhalation, ingestion, or skin absorption. Lead_sentence_391

Almost all inhaled lead is absorbed into the body; for ingestion, the rate is 20–70%, with children absorbing a higher percentage than adults. Lead_sentence_392

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. Lead_sentence_393

Seawater products can contain lead if affected by nearby industrial waters. Lead_sentence_394

Fruit and vegetables can be contaminated by high levels of lead in the soils they were grown in. Lead_sentence_395

Soil can be contaminated through particulate accumulation from lead in pipes, lead paint, and residual emissions from leaded gasoline. Lead_sentence_396

The use of lead for water pipes is a problem in areas with soft or acidic water. Lead_sentence_397

Hard water forms insoluble layers in the pipes whereas soft and acidic water dissolves the lead pipes. Lead_sentence_398

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. Lead_sentence_399

Drinking such water, over time, can cause health problems due to the toxicity of the dissolved lead. Lead_sentence_400

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. Lead_sentence_401

Ingestion of applied lead-based paint is the major source of exposure for children: a direct source is chewing on old painted window sills. Lead_sentence_402

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. Lead_sentence_403

Ingesting certain home remedies may result in exposure to lead or its compounds. Lead_sentence_404

Inhalation is the second major exposure pathway, affecting smokers and especially workers in lead-related occupations. Lead_sentence_405

Cigarette smoke contains, among other toxic substances, radioactive lead-210. Lead_sentence_406

Skin exposure may be significant for people working with organic lead compounds. Lead_sentence_407

The rate of skin absorption is lower for inorganic lead. Lead_sentence_408

Treatment Lead_section_35

See also: Chelation therapy Lead_sentence_409

Treatment for lead poisoning normally involves the administration of dimercaprol and succimer. Lead_sentence_410

Acute cases may require the use of disodium calcium edetate, the calcium chelate, and the disodium salt of ethylenediaminetetraacetic acid (EDTA). Lead_sentence_411

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. Lead_sentence_412

Environmental effects Lead_section_36

The extraction, production, use, and disposal of lead and its products have caused significant contamination of the Earth's soils and waters. Lead_sentence_413

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. Lead_sentence_414

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. Lead_sentence_415

Elevated concentrations of lead persist in soils and sediments in post-industrial and urban areas; industrial emissions, including those arising from coal burning, continue in many parts of the world, particularly in the developing countries. Lead_sentence_416

Lead can accumulate in soils, especially those with a high organic content, where it remains for hundreds to thousands of years. Lead_sentence_417

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. Lead_sentence_418

Contamination of soils and plants can allow lead to ascend the food chain affecting microorganisms and animals. Lead_sentence_419

In animals, lead exhibits toxicity in many organs, damaging the nervous, renal, reproductive, hematopoietic, and cardiovascular systems after ingestion, inhalation, or skin absorption. Lead_sentence_420

Fish uptake lead from both water and sediment; bioaccumulation in the food chain poses a hazard to fish, birds, and sea mammals. Lead_sentence_421

Anthropogenic lead includes lead from shot and sinkers. Lead_sentence_422

These are among the most potent sources of lead contamination along with lead production sites. Lead_sentence_423

Lead was banned for shot and sinkers in the United States in 2017, although that ban was only effective for a month, and a similar ban is being considered in the European Union. Lead_sentence_424

Analytical methods for the determination of lead in the environment include spectrophotometry, X-ray fluorescence, atomic spectroscopy and electrochemical methods. Lead_sentence_425

A specific ion-selective electrode has been developed based on the ionophore S,S'-methylenebis (N,N-diisobutyldithiocarbamate). Lead_sentence_426

An important biomarker assay for lead poisoning is δ-aminolevulinic acid levels in plasma, serum, and urine. Lead_sentence_427

Restriction and remediation Lead_section_37

By the mid-1980s, there was significant decline in the use of lead in industry. Lead_sentence_428

In the United States, environmental regulations reduced or eliminated the use of lead in non-battery products, including gasoline, paints, solders, and water systems. Lead_sentence_429

Particulate control devices were installed in coal-fired power plants to capture lead emissions. Lead_sentence_430

In 1992, U.S. Congress required the Environmental Protection Agency to reduce the blood lead levels of the country's children. Lead_sentence_431

Lead use was further curtailed by the European Union's 2003 Restriction of Hazardous Substances Directive. Lead_sentence_432

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. Lead_sentence_433

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/m over an 8-hour workday, and the blood lead level limit at 5 μg per 100 g of blood in 2012. Lead_sentence_434

Lead may still be found in harmful quantities in stoneware, vinyl (such as that used for tubing and the insulation of electrical cords), and Chinese brass. Lead_sentence_435

Old houses may still contain lead paint. Lead_sentence_436

White lead paint has been withdrawn from sale in industrialized countries, but specialized uses of other pigments such as yellow lead chromate remain. Lead_sentence_437

Stripping old paint by sanding produces dust which can be inhaled. Lead_sentence_438

Lead abatement programs have been mandated by some authorities in properties where young children live. Lead_sentence_439

Lead waste, depending on the jurisdiction and the nature of the waste, may be treated as household waste (in order to facilitate lead abatement activities), or potentially hazardous waste requiring specialized treatment or storage. Lead_sentence_440

Lead is released to the wildlife in shooting places and a number of lead management practices, such as stewardship of the environment and reduced public scrutiny, have been developed to counter the lead contamination. Lead_sentence_441

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. Lead_sentence_442

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. Lead_sentence_443

The fungus Aspergillus versicolor is effective at absorbing lead ions from industrial waste before being released to water bodies. Lead_sentence_444

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. Lead_sentence_445

See also Lead_section_38

Lead_unordered_list_3


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Lead.