Lead

Typical wastewaters

• domestic plumbing and drinking water distribution (lead service lines, solder, brass fittings) Pb²⁺ with its carbonate and hydroxide complexes dissolved from pipes, solder, fittings and service connections; generally below 5 µg/L but above 100 µg/L at the tap where lead service connections or fittings are present, varying with contact time release into the water supply, measured at the tap, not in the sewer; the WHO remedy is to remove the lead components and control corrosion meanwhile
• lead acid battery manufacture Pb²⁺ in acidic process wastewater, limited in the US per kilogram of lead used limit, not a measured concentration
• metal finishing (plating) Pb²⁺ held in solution by the complexing agents of plating baths; hydroxide precipitation to the 0.43 mg/L monthly BAT limit limit, not a measured concentration
• ore mining and milling (copper, lead, zinc, gold, silver, molybdenum) Pb²⁺ and particulate galena in mine drainage and mill water, limited at 0.3 mg/L monthly limit, not a measured concentration; raw values are in the ledger
• textile and leather wet processing Pb(II) as a ZDHC restricted metal, limited at 0.1 mg/L foundational, 0.05 progressive and 0.01 aspirational, with sludge thresholds of 5 mg/kg textile and 2 mg/kg leather a limit, not a measured occurrence

1 · Identity

Symbol, number

Pb, 82

Oxidation states in water

+2 as Pb²⁺ and its carbonate and hydroxide complexes, the state of dissolved lead and of the cerussite, hydrocerussite and pyromorphite scales; +4 as PbO₂ (plattnerite and scrutinyite), an insoluble scale that forms only under a strong free chlorine residual and dissolves back to Pb(II) when the oxidant falls; 0 as the metal of pipes, solder and brass fittings, the source of both.

Note

The element entry covers the metal, its oxides and the passivating films. This chapter is about what those films do inside a water pipe.

2 · Occurrence in water

Natural sources

Lead is rarely present in tap water from natural sources (WHO); source water lead is occasional and low.

Anthropogenic sources

Corrosion of lead service connections, lead pipes, lead solder and high lead alloy fittings, and lead compounds leached from PVC pipe (WHO background document); lead acid battery manufacture, regulated in the US per kilogram of lead used; metal finishing (0.43 mg/L monthly BAT) and ore mining and milling (0.3 mg/L monthly); smelting, pigments, ammunition and the ledger's lead chapter. Atmospheric lead from petrol has declined, which has made water the largest controllable source of lead exposure in the USA (WHO background document).

3 · Speciation

Dissolved lead in tap water is Pb²⁺ with its carbonate complexes (PbCO₃ aq, Pb(CO₃)₂²⁻) and PbOH⁺, and its concentration is set by the solubility of whatever scale coats the pipe: the divalent scales cerussite, hydrocerussite and lead hydroxide generally determine lead at the tap (WHO background document). Soft, acidic, low alkalinity water is the most plumbosolvent; raising pH to 8 to 9 and dosing orthophosphate convert the scale to less soluble hydroxypyromorphite. A high free chlorine residual oxidises the scale to PbO₂, which releases very little lead until a switch to chloramine lowers the oxidation reduction potential and dissolves it again (WHO, EPA OCCT).

Solubility

Controlled by the scale. Hydrocerussite dissolution slows with rising pH, with dissolved inorganic carbon and strongly with orthophosphate; lead(II) hydroxide and carbonate solubilities are the reason a pH of 8 to 9 and alkalinity reduce plumbosolvency (WHO background document, EPA OCCT). The solubility constants themselves are not printed in the sources read (Schock's lead solubility diagrams are the standard reference, cited by WHO as references 125 to 128).

Hydrolysis

Pb²⁺ hydrolyses to PbOH⁺ above about pH 7 and to Pb(OH)₂ and Pb(OH)₃⁻ at high pH; lead hydroxide is amphoteric, so hydroxide precipitation of industrial lead has a solubility minimum near pH 9 to 10 and rises again above it (Metcalf and Eddy chapter 6, from the chapter).

Complexation

Carbonate is the complexant that matters in tap water; natural organic matter binds lead in surface water; chloride raises lead release relative to sulfate (chloride to sulfate mass ratio above 0.5 to 0.7 is a warning sign in the EPA OCCT, though not a sure predictor).

Precipitates

Hydrocerussite Pb₃(CO₃)₂(OH)₂, cerussite PbCO₃, lead hydroxide, hydroxypyromorphite Pb₅(PO₄)₃OH and other lead orthophosphates, plattnerite and scrutinyite PbO₂, galena PbS, anglesite PbSO₄ (battery scales).

4 · Role in treatment

5 · Removal and control

6 · Analytics

Sampling pitfalls

The protocol decides the result: first draw after stagnation gives the highest value, fully flushed the lowest, random daytime the truest but most variable (WHO). The EU compliance sample is a random daytime 1 litre sample at the consumer's tap without prior flushing (DWD Annex II Part D); to prove that no lead solder or fittings were installed, take a worst case sample after extended stagnation (WHO). Acidify after collection, not before, so that particulate lead is counted; sequential volume sampling locates the lead source along the line.

7 · Regulatory limits

Limits change, and many are set locally. Treat these as the published values to start from, not as your compliance target: check the standard in force at your site and the numbers written into your own permit.

8 · Health and environmental effects

Toxicity

Neurodevelopmental effects in children at the lowest blood lead levels, cardiovascular mortality, raised systolic blood pressure, impaired renal function, hypertension, impaired fertility and adverse pregnancy outcomes; JECFA found no threshold and withdrew the PTWI in 2010; fetuses, infants and children are the most sensitive (WHO). Inorganic lead compounds are IARC Group 2A, lead itself 2B (WHO background document).

Bioaccumulation

Lead is a cumulative poison stored in bone; absorption is higher in children and when dietary iron, calcium and phosphorus are low (WHO background document).

Ecotoxicity

US EPA aquatic life criteria: freshwater 65 µg/L acute and 2.5 µg/L chronic at 100 mg/L hardness (hardness dependent), saltwater 210 and 8.1 µg/L (1984). EU EQS: 1.2 µg/L annual average (inland, bioavailable) and 1.3 µg/L (other surface waters), 14 µg/L maximum.

Flags

• The tap water surveys quoted are 1970s to 2000s figures from the WHO 2016 background document and predate most corrosion control and replacement programmes.
• The US action level revision to 0.010 mg/L on 1 November 2027 is taken from the EPA NPDWR table; the Federal Register text of the LCRI was not reachable, and the rule may be reconsidered; check before reuse.
• The hydroxypyromorphite formula is written as Pb₅(PO₄)₃OH; the EPA OCCT prints hydroxypyromorphite as Pb₉(PO₄)₆, which is the composition of Pb₃(PO₄)₂, and both are quoted as it gives them.
• The PbO₂ formation and reduction equations are electron balances written here; WHO and EPA describe the pathway without equations.
• The hydroxide and sulfide precipitation rows are cited to Metcalf and Eddy chapter 6 from memory of the text, not re-read.
• Abu Dhabi values cover two media (marine 0.1 mg/L, sewer 5 mg/L); other GCC states were not read.
• No detection limit was read for ISO 17294-2 or Standard Methods 3113 this session.
• The PbO₂ reductive dissolution is described, not written as an equation; a two electron half reaction does not pass the checker.

Gaps

• No source read gives lead in surface water, seawater, municipal wastewater or measured industrial effluents; only limits and tap surveys are quoted.
• Lead solubility constants and Schock's solubility diagrams (WHO references 125 to 128) were not read; the scale chemistry is qualitative.
• The LCRI details (first and fifth litre sampling, trigger level removal, copper action level) were not read because the Federal Register page was blocked.
• Lead removal from industrial effluent is cited to a textbook chapter; no BAT description with percentages was read.
• Brass and galvanised pipe as lead sources, and lead in PVC stabilisers, are mentioned by WHO but not quantified.
• Other GCC discharge standards (Saudi, Oman, Qatar) were not read.
• Lead hydrolysis, carbonate complexation and amphoteric redissolution are from Stumm and Morgan chapter 6 and Metcalf and Eddy chapter 6, from the chapter, not re-read; no stability constants or solubility products were read.

Sources

Identity

Name and symbol

Lead, Pb

Atomic number

82 protons

Position

group 14 · period 6 · p-block · post-transition metal

CAS number

7439-92-1

Atomic structure

Atomic mass

207.2 u

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p²
[Xe] 6s²⁴f¹⁴⁵d¹⁰⁶p²

Electrons per shell

2, 8, 18, 32, 18, 4

Valence electrons

4 outer shell

Physical properties

State at room temperature

Solid

Melting point

600.61 K (327.46 °C)

Boiling point

2,022 K (1,748.85 °C)

Density

11.342 g/cm3

Appearance

metallic gray

Thermal conductivity

35.3 W/(m·K)

Electrical resistivity

208 nΩ·m at 20 °C

Electrical conductivity

4.81 MS/m

Crystal structure

face-centered cubic

Molar heat capacity

26.65 J/(mol·K)

Chemical properties

Oxidation states

+4, +2

Electronegativity

2.33 (Pauling Scale)

Ionisation energy

7.417 eV
1st 715.6, 2nd 1,450.5, 3rd 3,081.5 kJ/mol

Electron affinity

0.36 eV

Atomic radius

empirical 146, covalent 146, van der Waals 202 pm

Ionic radius

Pb²⁺ 119; Pb⁴⁺ 78 pm

Reactivity

A relatively unreactive post-transition metal of group 14 in which the inert pair effect makes +2 the normal state and +4 a strong oxidant; its weak metallic character shows in amphoteric behaviour, lead and its oxides dissolving in both acids and alkalis, and in the protective surface films that make bulk lead effectively inert.

with water

Does not react with pure water; in moist air a film of lead(II) carbonate (with sulfate or chloride in city or sea air) forms and renders the bulk metal effectively inert.

with oxygen, air

Fresh lead tarnishes to a dull grey protective film; finely powdered lead is pyrophoric and burns with a bluish-white flame to the monoxide: $\ce{2 Pb + O2 -> 2 PbO}$, litharge, which on further heating in air gives red lead Pb3O4.

with acids

Resists sulfuric and phosphoric acid because insoluble lead salts passivate it, but nitric acid dissolves it: $\ce{3 Pb + 8 HNO3 -> 3 Pb(NO3)2 + 2 NO + 4 H2O}$, hydrochloric acid attacks it slowly, acetic acid dissolves it when oxygen is present, and concentrated alkalis give plumbites.

with halogens

Fluorine reacts at room temperature to the difluoride: $\ce{Pb + F2 -> PbF2}$, and chlorine on heating gives the dichloride: $\ce{Pb + Cl2 -> PbCl2}$, the chloride layer slowing further attack.

Typical compounds

• PbO lead(II) oxide litharge, yellow, for lead crystal glass and glazes
• PbO₂ lead(IV) oxide brown oxidant, the positive plate of lead-acid batteries
• Pb₃O₄ lead(II,IV) oxide red lead, the classic rust-preventing primer
• PbS lead(II) sulfide galena, the chief ore
• PbSO₄ lead(II) sulfate insoluble, forms on both battery plates as they discharge
• Pb(NO₃)₂ lead(II) nitrate one of the few soluble lead salts

Occurrence, production and use

Crustal abundance

1.4×101 milligrams per kilogram

Oceanic abundance

3×10-5 milligrams per liter

Occurrence and sources

Lead is obtained chiefly from galena (PbS) by a roasting process. Anglesite, cerussite, and minim are other common lead minerals.

• galena (PbS), with zinc, silver and copper sulfides China, Australia, Missouri (Viburnum Trend), Peru, Russia, India, Mexico, Sweden, Turkey, Bolivia, Ireland, Portugal
• crustal and oceanic abundance about 11 ppm crust (BGS via RSC); 14 mg/kg crust and 0.00003 mg/L seawater (PubChem)

Extraction, production

Roasting and smelting of galena concentrate

RSC states lead is obtained from galena by a roasting process but names no products, and USGS gives no chemistry, so no equation is written

Secondary lead from spent lead-acid batteries

about 1 million t in the United States in 2024, 70 percent of apparent consumption; antimony is recovered with it as antimonial lead

Uses

Lead is a soft, malleable and corrosion resistant material. The ancient Romans used lead to make water pipes, some of which are still in use today. Unfortunately for the ancient Romans, lead is a cumulative poison and the decline of the Roman empire has been blamed, in part, on lead in the water supply. Lead is used to line tanks that store corrosive liquids, such as sulfuric acid (H2SO4). Lead's high density makes it useful as a shield against X-ray and gamma-ray radiation and is used in X-ray machines and nuclear reactors. Lead is also used as a covering on some wires and cables to protect them from corrosion, as a material to absorb vibrations and sounds and in the manufacture of ammunition. Most of the lead used today is used in the production on lead-acid storage batteries, such as the batteries found in automobiles.

Several lead alloys are widely used. Solder, an alloy that is nearly half lead and half tin, is a material with a relatively low melting point that is used to join electrical components, pipes and other metallic items. Type metal, an alloy of lead, tin and antimony, is a material used to make the type used in printing presses and plates. Babbit metal, another lead alloy, is used to reduce friction in bearings.

Lead forms many useful compounds. Lead monoxide (PbO), also known as litharge, is a yellow solid that is used to make some types of glass, such as lead crystal and flint glass, in the vulcanizing of rubber and as a paint pigment. Lead dioxide (PbO2) is a brown material that is used in lead-acid storage batteries. Trilead tetraoxide (Pb3O4), also known as red lead, is used to make a reddish-brown paint that prevents rust on outdoor steel structures. Lead arsenate (Pb3(AsO4)2) has been used as an insecticide although other, less harmful, substances have now largely replaced it. Lead carbonate (PbCO3), also known as cerussite, is a white, poisonous substance that was once widely used as a pigment for white paint. Use of lead carbonate in paints has largely been stopped in favor of titanium oxide (TiO2). Lead sulfate (PbSO4), also known as anglesite, is used in a paint pigment known as sublimed white lead. Lead chromate (PbCrO4), also known as crocoite, is used to produce chrome yellow paint. Lead nitrate (Pb(NO3)2) is used to make fireworks and other pyrotechnics. Lead silicate (PbSiO3) is used to make some types of glass and in the production of rubber and paints.

The metal is very effective as a sound absorber, is used as a radiation shield around X-ray equipment and nuclear reactors, and is used to absorb vibration. White lead, the basic carbonate, sublimed white lead, chrome yellow, and other lead compounds are used extensively in paints, although in recent years the use of lead in paints has been drastically curtailed to eliminate or reduce health hazards.

Lead oxide is used in producing fine "crystal glass" and "flint glass" of a high index of refraction for achromatic lenses. The nitrate and the acetate are soluble salts. Lead salts such as lead arsenate have been used as insecticides, but their use in recent years has been practically eliminated in favor of less harmful organic compounds.

• Batteries: lead-acid batteries for vehicle starting, standby power for computer and telecom networks, and motive power about 86 percent of US lead consumption in 2024 (usgs-mcs2025-lead)
• Chemicals (explosives and pigments): lead azide, lead trinitroresorcinate and lead picrate primary explosives; lead chromate pigments, whose effluent is pretreated for lead and antimony by precipitation; legacy white lead and red lead pigments
• Construction, glass and shielding: roofing, flashing, stained-glass cames; lead crystal glass; radiation shielding; cable sheathing (declining), weights, diving belts
• Ammunition and alloys: ammunition; antimonial lead, solders (non-potable), bearing metals, pewter
• Mining: lead-zinc and lead-silver mining and concentrate export; lead in extractive-waste water

Safety, toxicity

Care must be used in handling lead as it is a cumulative poison. Environmental concerns with lead poisoning has resulted in a national program to eliminate the lead in gasoline.

GHS classification, signal word Danger

• H360FD May damage fertility; May damage the unborn child Reproductive toxicity
• H362 May cause harm to breast-fed children toxicity, effects on or via lactation
• H400 Very toxic to aquatic life Hazardous to the aquatic environment, acute hazard
• H410 Very toxic to aquatic life with long lasting effects Hazardous to the aquatic environment, long-term hazard
• H302 Harmful if swallowed Acute toxicity, oral
• H332 Harmful if inhaled Acute toxicity, inhalation
• H360 May damage fertility or the unborn child Reproductive toxicity
• H372 Causes damage to organs through prolonged or repeated exposure Specific target organ toxicity, repeated exposure
• H373 May causes damage to organs through prolonged or repeated exposure Specific target organ toxicity, repeated exposure
• H351 Suspected of causing cancer Carcinogenicity
• H370 Causes damage to organs Specific target organ toxicity, single exposure
• H341 Suspected of causing genetic defects Germ cell mutagenicity
• H360Df May damage the unborn child; Suspected of damaging fertility Reproductive toxicity

Discovery and name

Discovered by

Middle East

Discovered

7000 BCE

First isolated

not in sources

Named by

not in sources

Origin of the name

possibly from a PIE root meaning “to flow”, for its low melting point

Lead is a bluish-white metal of bright luster. It is very soft, highly malleable, ductile, and a poor conductor of electricity. It is very resistant to corrosion; lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. It is used in containers for corrosive liquids (such as sulfuric acid) and may be toughened by the addition of a small percentage of antimony or other metals.