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.