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Lead and its inorganic compounds

DESIGNATIONS

CAS No.: 7439-92-1
Registry name: Lead
Chemical name: Lead
Synonyms, Trade names:
Plumbum
Chemical name (German):
Blei
Chemical name (French):
Plomb
Appearance:
grey metal, bluish white shine on freshly cut surfaces

BASIC CHEMICAL AND PHYSICAL DATA

Chemical Symbol: Pb
Rel. atomic mass: 207.21 g
Density: 11.34 g/cm3
Boiling point: 1,740°C
Melting point: 327.4°C
Vapour pressure: 0 hPa
Solvolysis/solubility: in water: except Pb(NO3)2 and Pb(CH3-COO)2 inorganic lead compounds are virtually insoluble in water

BASIC DATA OF SELECTED COMPOUNDS

CAS No: 1317-36-8 7758-95-4
Chemical name: Lead(II) oxide Lead(II) chloride
Synonyms, Trade names: Lead monoxide, litharge Lead chloride, lead dichloride
Chemical name (German): Blei(II)-oxid Blei(II)-chlorid
Chemical name (French): Oxyde de plomb(II) Chlorure de plomb(II)
Appearance: red crystalline powder white crystalline solid (needles)
Empirical formula: PbO PbCl2
Rel. molecular mass: 223.21 g 278.11 g
Density: 9.53 g/cm3 5.85 g/cm3
Boiling point: 1472°C 950°C
Melting point: 888°C 501°C
Solvolysis/solubility: insoluble in water;
soluble in acetic acid and dilute nitric acid
in water: 9.9 g/l
insoluble in ethanol;
slightly soluble in dilute HCl

ORIGIN AND USE

Usage:
In 1987, some 60 % of the lead produced was used to make batteries (ULLMANN, 1990). Further areas of application are lead pipes, alloys, cables, pigments and anti-knock agents in fuel. On average, 25 - 40 % of the lead used throughout the world is obtained by recycling scrap and lead waste (MERIAN, 1984).

Important lead compounds:

Oxides PbO glass making
Pb3O4 rust inhibitor for iron
PbO2 oxidising agent
Stearate Pb(C17H35COO)2 stabiliser in PVC compounds
Oleates, naphthenates   drying accelerator for oil-based paints
Tetraacetate Pb(CH3COO)4: oxidising agent
Tetraalkyls Pb(CH3)4 anti-knock agent in fuel
Pb(C2H5)4 ((r) lead compounds - organic)

Origin/derivation:
Lead is an element forming approx. 0.002 % of the Earth's crust. The most important minerals are galena (PbS), cerussite (PbCO3), crocoite (PbCrO4) and pyromorphite (Pb5(PO4)3Cl).

Production figures:
Lead production for most important lead producing and consuming countries, 1987:

Country Mine production (contained Pb), 103 t Refined production (primary and secondary), 103 t Refined consumption; 103 t
Soviet Union 510.0 780.0 775.0
Other Eastern Block 503.7 623.9 665.5
Australia, Oceania 486.2 220.7 65.0
Canada 413.4 225.8 102.9
United States 318.3 1027.9 1202.8
Peru 192.0 70.8 21.9
Mexico 177.1 185.1 99.6
Total World 3389.3 5631.4 5622.5

(figures from ULLMANN, 1990)

Toxicity

Mammals:
Rat: LD 11,000 mg/kg, oral (lead acetate) acc. DVGW, 1985
LD50 100-825 mg/kg, oral (lead arsenate) acc. DVGW, 1985
Rabbit: LD50 125 mg/kg, oral (lead arsenate) acc. DVGW, 1985
Chicken: LD50 450 mg/kg, oral (lead arsenate) acc. DVGW, 1985
Dog: LD 2,000-3,000 mg/kg, oral (lead sulphate) acc. DVGW, 1985
Aquatic organisms:
American minnow: LC50 6.7-10.5 mg/l (24h) (lead chloride) acc. WHO, 1989
LC50 4.3-8.7 mg/l (48h) (lead chloride) acc. WHO, 1989
LC50 3.9-7.9 mg/l (96h) (lead chloride) acc. WHO, 1989
LC50 10.7-63.9 mg/l (24h) (lead acetate) acc. WHO, 1989
LC50 7.2-16.7 mg/l (48h) (lead acetate) acc. WHO, 1989
LC50 4.9-11.8 mg/l (96h) (lead acetate) acc. WHO, 1989
Blue perch: LC50 22.5-30.4 mg/l (24h) (lead chloride) acc. WHO, 1989
LC50 20.9-29.1 mg/l (48h) (lead chloride) acc. WHO, 1989
LC50 20.0-28.4 mg/l (96h) (lead chloride) acc. WHO, 1989
LC50 6.3 mg/l (24h) (lead nitrate) acc. WHO, 1989
LC50 6.3 mg/l (48h) (lead nitrate) acc. WHO, 1989
Rainbow trout: LC50 1.17 mg/l (96h) (lead nitrate) acc. WHO, 1989
Cockle: LC50 > 500 mg/l (48h) (lead nitrate) acc. WHO, 1989
Mya arenaria: LC50 > 50 mg/l (48h) (lead nitrate) acc. WHO, 1989
Water flea: LC50 0.45 mg/l (48h) (lead chloride) acc. WHO, 1989
LC50 0.24-0.38 mg/l (21d) (lead chloride) acc. WHO, 1989
LC50 4.19 - 5.89 mg/l (24h) (lead acetate) acc. WHO, 1989

Characteristic effects:

Humans/mammals: Lead can be absorbed by inhalation of dusts or by eating foods containing lead and - in the case of plants - by way of soluble lead salts in soils. Whereas inhalation is the major source of intake in workplace exposure, ingestion and resorption in the gastro-intestinal tract predominate in the population in general. It has recently become established that considerable quantities of lead enter the human body via drinking water (lead pipes).

Lead inhibits the various enzymes of the haemoglobin metabolism thus reducing the oxygen balance and the respiratory volume. Lead reduces the activity of the d -aminolaevulinic acid-dehydratase in the erythrocytes. Damage occurs with long-term intake of less than 1 mg/day. Symptoms of chronic poisoning are lead deposits along the edge of the gums as well as colic fits and spasms. Apathy, irritability, insomnia and - in some cases - behavioural irregularities in children are indications of damage to the nervous system. Lead passes through the placenta and accumulates in the foetus. In Germany, lead is listed in pregnancy group B (risk of embryonic damage is assumed).

The upper limit for the blood-lead level before it is considered to reach harmful proportions is 35 m g Pb/100 ml of blood for adults and 30 m g Pb/100 ml in children and pregnant women. The WHO applies a limit value of 100 µg Pb/100 ml of blood but is even considerably lower in most countries.

Inorganic lead compounds are resorbed in the gastro-intestinal tract. Children resorb lead more easily than adults (DVGW, 1985). Some 90 % of the resorbed lead is bonded to the erythrocytes and thus distributed throughout the entire body. It is deposited above all in the bones.

Approximately 90 % of the lead absorbed orally is excreted again; 75-80 % by elimination in the kidneys (MERIAN, 1984). A small quantity is deposited in hair and nails, exuded with sweat or stored in mother´s milk.

Plants: Plants mainly absorb lead from the soil, but only to a small extent from the atmosphere. Lead has a toxic effect on growth: application initially results in enhanced growth, but from a concentration of 5 ppm, this is counteracted by severe growth retardation, discoloration and morphological abnormalities (UBA, 1976). There is an adverse influence on photosynthesis, respiration and other metabolic processes. As a final step, lead inhibits the intake of essential nutrients from the soil. Pb++ has only a slight effect on the growth of taller plants. Generally speaking, it is the quality rather than the yield which suffers. Compared to the toxicity in humans, the phytotoxicity of lead is of minor importance.

ENVIRONMENTAL BEHAVIOUR

Water:
Surface water forms an accumulation sink for lead compounds. Insoluble lead compounds sink and are adsorbed in the sediment or accumulate on suspended matter (in particular the clay fraction). Aquatic plants likewise accumulate lead. The biochemical oxidation of organic substances is inhibited at lead concentrations above 0.1 mg/l; fauna is depleted by concentrations above 0.2 mg/l and 0.3 mg/l is the threshold for fish toxicity (trout and white fish) [DVGW, 1985].

Groundwater is adversely affected by soluble lead compounds (e.g. lead chloride, nitrate). Nevertheless, it has been established that drinking water that passes through lead pipes may contain high lead concentrations (depending on the groundwater chemism). Lead is not chemically affected by deoxygenated water. In lead pipes, carbonated water forms lead carbonate deposits on the inner pipe surface.

Air:
Large quantities of lead are released into the atmosphere by combustion processes. There is a major difference between urban and rural areas. Lead compounds may be transported over a considerable distance depending on the speed and direction of the wind as well as precipitation and humidity. However, most of the lead in the atmosphere directly sediments or is removed by precipitation. Lead bonds to small dust particles in the air which in turn are deposited on vegetation and soil. Lead from motor-vehicle emissions accumulates in the immediate vicinity of roads.

Soil:
The absorption rate depends on the properties of the soil. There is a considerable affinity with humic substances. The pH is important for the availability of lead from its compounds. A low pH is linked to a high degree of desorption into the soil solution. However, as lead is quite immobile (e.g. more than cadmium), it remains in the topsoil and is not absorbed by plants to the same extent. Soils thus represent an important sink for lead compounds. Additional contamination results from the deposition of sewage sludge containing lead on farmland. Only extremely high contamination rates constitute a hazard to groundwater.

Half-life:
Lead remains in the atmosphere for roughly 7 - 30 days (FATHI & LORENZ, 1980). The biological half-life in blood is between 20 and 40 days; in bones up to several years (WHO, 1987).

Food chain:
Lead is found in all foodstuffs and fodders because it is ubiquitous. Vegetable foodstuffs generally contain more lead than animal products. This is the result of their special exposure: dust precipitations containing lead cling to the surface of plants and are thus consumed. In higher life forms, the maximum concentrations are found in internal organs such as the liver and kidneys. The increase in concentration is as follows in aquatic systems: water < fish prey < fish < sediment (DVGW, 1985).

Most humans absorb lead through their food (roughly 440 - 550 m g per day) and drinking water (some 20 m g per day) (DFG, 1982). At places where lead is produced or processed, atmospheric pollution is an additional problem. Approximately 30 - 50 % of the lead inhaled remains in the lungs (WHO, 1987); the rest is absorbed by the body and usually deposited in the bones.

ENVIRONMENTAL STANDARDS

Medium/ acceptor Sector Country/ organ.

Status

Value Cat. Remarks Source
Water: Drinkw AUS

(L)

0.05 mg/l   1973 acc. MERIAN, 1984
Drinkw CDN

L

0.05 mg/l   1978 acc. DVGW, 1985
Drinkw CH

(L)

0.05 mg/l     acc. MERIAN, 1984
Drinkw D

L

0.04 mg/l TVO   acc. ROTH, 1989
Drinkw EC

L

0.05 mg/l   1) acc. DVGW, 1985
Drinkw J

(L)

0.10 mg/l   1968 acc. MERIAN, 1984
Drinkw SU

(L)

0.10 mg/l   1970 acc. MERIAN, 1984
Drinkw USA

L

0.05 mg/l MCL   acc. SCHROEDER, 1985
Drinkw ZA

(L)

0.05 mg/l     acc. MERIAN, 1984
Surface CDN   0.05 mg/l   Simple treatment acc. DVGW, 1985
Surface CDN   0.25 mg/l   Refined treatment acc. DVGW, 1985
Surface D

L

0.03 mg/l   2) acc. DVGW, 1985
Surface D

L

0.05 mg/l   3) acc. DVGW, 1985
Surface EC

L

0.05 mg/l   4) acc. DVGW, 1985
Groundw NL

G

0.015 mg/l   Reference acc. TERRA TECH 6/94
Groundw NL

L

0.075 mg/l   Intervention acc. TERRA TECH 6/94
Troughw D

G

0.04 mg/l     acc. DVGW, 1985
Troughw GB   0.10 mg/l     acc. DVGW, 1985
Troughw USA   0.05 mg/l   1968 acc. DVGW, 1985
Irrigation D

G

0.5 mg/l   For field cultivation acc. DVGW, 1985
Irrigation D

G

0.05 mg/l   For cultivation under glass acc. DVGW, 1985
Irrigation GB   2 mg/l     acc. DVGW, 1985
Irrigation USA   5 mg/l   1968 acc. DVGW, 1985
Soil: Soil CH

G

50 mg/kg VSBo HNO3 extract5) acc. BUB, 1987
Soil CH

G

1 mg/kg VSBo NaNO3 extract5) acc. BUB, 1987
Soil GB

G

550 mg/kg   Gardens/vegetable g. acc. SAUERBECK, 1986
Soil GB

G

1,500 mg/kg   Parks acc. SAUERBECK, 1986
Soil GB

G

2,000 mg/kg   Public land acc. SAUERBECK, 1986
Soil NL

G

85 mg/kg DS   Reference acc. TERRA TECH 6/94
Soil NL

L

530 mg/kg DS   Intervention acc. TERRA TECH 6/94
Sew. sludge D

G

100 mg/kg   6) acc. KLOKE, 1988
Sew. sludge D

L

2,000 g/(ha·a)   7) acc. KLOKE, 1988
Fertiliser D

L

200 g/ha/a   7) acc. KLOKE, 1988
Air: Emiss. D

L

5 mg/m3   mass flow > 25 g/h11) acc. TA Luft, 1986
  CH L 0.1 mg/(m2d) LRV dust depos., 1 a NN
  CH L 0.001 mg/m3 LRV 1 a NN
  D L 0.002 mg/m3 IW112)   acc. TA Luft, 1986
  D L 0.25 mg/(m2d) IW113) dust depos. acc. TA Luft, 1986
  D L 0.003 mg/m3 MIK 24 h NN
  D L 0.0015 mg/m3 MIK 1 a NN
  DDR

L

0.0003 mg/m3   Long-time value acc. HORN, 1989
  E

G

0.05 mg/m3   Short-time value acc. STERN, 1986
  EC

G

0.002 mg/m3   12 m acc. STERN, 1986
  H

G

0.0007 mg/m3   30 min acc. STERN, 1986
  IL

G

0.005 mg/m3   24 h acc. STERN, 1986
  PO

G

0.0005 mg/m3   24 h acc. STERN, 1986
  RC

G

0.007 mg/m3   24 h acc. STERN, 1986
  WHO G 0.005-0.001 mg/m3   1 a NN
  YV

G

0.005 mg/m3   12 m acc. STERN, 1986
Workp AUS

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp BG

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp CH

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp CS

(L)

0.05 mg/m3   Long-time value acc. MERIAN, 1984
Workp CS

(L)

0.2 mg/m3   Short-time value acc. MERIAN, 1984
Workp D

L

0.1 mg/m3 MAK 11) DFG, 1989
Workp DDR

(L)

0.01 mg/m3   Short-time value acc. HORN, 1989
Workp DDR

(L)

0.005 mg/m3   Long-time value acc. HORN, 1989
Workp H

(L)

0.02 mg/m3     acc. MERIAN, 1984
Workp I

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp J

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp NL

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp PL

(L)

0.05 mg/m3     acc. MERIAN, 1984
Workp RO

(L)

0.1 mg/m3   Long-time value acc. MERIAN, 1984
Workp RO

(L)

0.2 mg/m3   Short-time value acc. MERIAN, 1984
Workp S

(L)

0.1 mg/m3     acc. MERIAN, 1984
Workp SF

(L)

0.15 mg/m3     acc. MERIAN, 1984
Workp USA

(L)

0.15 mg/m3 TWA   ACGIH, 1986
Workp WHO

(L)

0.03 - 0.06 mg/m3     acc. MERIAN, 1984
Workp YU

(L)

0.15 mg/m3     acc. MERIAN, 1984
  D

L

70 mg/dl BAT Whole blood12) DFG, 1989
  D

L

30 mg/dl BAT Whole blood, women <45 y.12) DFG, 1989
  D

L

15 mg/l BAT Urine13) DFG, 1989
  D

L

6 mg/l BAT Urine,
women <45 y.13)
DFG, 1989
Foodstuffs:   WHO/FAO

G

430 mg/(pers·d)   Adults acc. DFG, 1982
  USA

G

300 mg/ (pers·d)   Infants acc. DFG, 1982
Fruit/vegetable juice   CH

L

0.3 mg/l     acc. MERIAN, 1984
Milk   CH

L

0.05 mg/l     acc. MERIAN, 1984
Milk   D

G

0.03 mg/kg     acc. GROßKLAUS, 1989
Cheese   D

G

0.25 mg/kg   Except hard cheese acc. GROßKLAUS, 1989
Meat   D

G

0.25 mg/kg   All animal species acc. GROßKLAUS, 1989
Meat   D

G

0.8 mg/kg   Liver/kidneys acc. GROßKLAUS, 1989
Fish   D

G

0.5 mg/kg   Except tins acc. GROßKLAUS, 1989
Fish   D

G

1 mg/kg   Tinned fish acc. GROßKLAUS, 1989
Mineral water   D

L

< 0.05 mg/l     acc. DVGW, 1985

Note:

1) The lead content of a sample taken from a lead pipe after draining off the water should not exceed 0.05 mg/l. If a water sample is taken directly or after the water has been allowed to flow off and if the lead content frequently or considerably exceeds 0.1 mg/l, remedial measures must be taken to reduce the risk of lead intake by consumers.
2) Limit value for natural treatment
3) Limit value for chemophysical treatment
4) Mandatory value for simple and standard physical, chemical and refined chemical treatment and sterilisation
5) Application of sewage sludge to soil used for agricultural or horticultural purposes prohibited (pollutant content of dry, mineral soils)
6) Total tolerable content in cultivated soil
7) Legally permitted additional annual loading of soil
8) Pb and its compounds, stated as Pb
9) Pb and its anorganic compounds as suspended dust, stated as Pb
10) Pb and its anorganic compounds within dust sediments, stated as Pb
11) Exposure of pregnant women to lead can damage the embryo even when in compliance with MAK and BAT value.
12) Parameter: lead
13) Parameter: delta-aminolaevulinic acid

- The lead content of fuel is limited by law in numerous countries in an attempt to reduce the emissions from motor-vehicle traffic. The maximum level in petrol in the Federal Republic of Germany and Switzerland is 0.15 mg/l. More and more EC countries are starting to prescribe the use of unleaded fuel such as has been in force in several American states for many years.

- Certain industrial lead emissions are likewise subject to legislation. Thus, for example, the German TA-Luft (1986) fixed the IW1 immission values for lead as a constituent part of suspended dust at 2 m g/m3 to guard against health hazards and at 0.25 mg/(m2d) to minimise the nuisance level. Furthermore, the amount of inorganic lead dust with a mass flow of 25 g/h may not exceed 5 mg/m3. During the production of lead batteries the dust emissions must not exceed 0.5 mg/m3 at a mass flow of 5 g/h or more.

- The German Lead - Zinc Law (1974) stipulates that eating, drinking and cooking utensils may not give off lead after being boiled for 30 minutes with 4 % acetic acid.

- The 1977 Paint Law prohibits the use of lead in paints, foodstuffs, semi-luxury goods and consumer goods.

- The 1988 Order Governing the Use of Pesticides totally prohibits the use of lead compounds for such purposes.

- Usage banned in D in line with 1985 Order on Cosmetics

Comparison/reference values

Medium/origin Country Value Source
Surface water:
Lake Constance (1982) D 0.2 µg/l acc. DVGW, 1985
Neckar, Berg (1982) D 4 µg/l acc. DVGW, 1985
Rhine, Cologne (1983) D 1.5-14 µg/l acc. DVGW, 1985
Rhine, Duisburg (1983) D 0.1-90.1 µg/l acc. DVGW, 1985
Ruhr, Witten (1983) D 2-9 µg/l acc. DVGW, 1985
Drinking water:
The Hague (1976) NL 2 µg/l acc. DVGW, 1985
Karlsruhe (1975) D 4 µg/l acc. DVGW, 1985
Drinking water D 1-22.5 µg/l (n=80) acc. DFG, 1982
Sediment:      
Rhine, Basle (1975-77) D 90 mg/kg acc. DVGW, 1985
Rhine, Mannheim (1975 77) D 370 mg/kg acc. DVGW, 1985
Rhine, Emmerich (1975-77) D 600 mg/kg acc. DVGW, 1985
Ruhr (1975-77) D 1,200 mg/kg acc. DVGW, 1985
Danube, Leipheim (1975-77) D 120 mg/kg acc. DVGW, 1985
Air:
Municipal areas   0.5-10 µg/m3 acc. MERIAN, 1986
Rural areas   0.1-1 µg/m3 acc. MERIAN, 1986
North American cities, annual average   0.1-5 µg/m3 acc. MERIAN, 1986
Plants:
"Natural lead content"   < 3 ppm (dry matter) acc. MERIAN, 1986
Foodstuffs:
Milk D 0.001-0.084 ppm (n=339) acc. MERIAN, 1986
Ox/calves liver D 0.01-3.31 ppm (n=1452) acc. MERIAN, 1986
Wine D 0.0005-3.08 ppm (n=471) acc. MERIAN, 1986

Assessment/comments

Lead is not a physiologically essential element. It is most frequently absorbed in foodstuffs and at the workplace. The persistence of lead and its compounds has caused a ubiquitous distribution. Accumulation by way of food chains can thus hardly be prevented, but nevertheless, it can be largely minimised by way of local emission restrictions. Investigations in the field of toxicity in humans should be based on the blood-lead level of children and pregnant women.


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