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DESIGNATIONS
CAS No.: 7440-43-9
Registry name: Cadmium
Chemical name: Cadmium
Synonyms, Trade names: Cadmium
Chemical name (German): Cadmium
Chemical name (French): Cadmium
Appearance: soft heavy metal with silvery white sheen
BASIC CHEMICAL AND PHYSICAL DATA
Chemical symbol: Cd
Rel. atomic mass: 112.41 g
Density: 8.642 g/cm3 at 20°C
Boiling point: 767°C
Melting point: 320.9°C
Vapour pressure: 0.013 Pa at 180°C
Solvolysis/solubility: Cd readily dissolves in nitric acid, but only slowly in hydrochloric and sulphuric acid
Basic data of selected compounds
| CAS No: | 1306-19-0 | 10108-64-2 |
| Chemical name: | Cadmium oxide | Cadmium chloride |
| Synonyms, Trade names: | Cadmium orange, Cadmium yellow, Aurora yellow | Cadmium dichloride, Caddy |
| Chemical name (German): | Cadmiumoxid | Cadmiumchlorid |
| Chemical name (French): | Oxyde de cadmium | Chlorure de cadmium |
| Appearance: | yellow to brown solid | colourless, crystalline solid |
| Empirical formula: | CdO | CdCl2 |
| Rel. molecular mass: | 128.41 g | 183.32 g |
| Density: | 6.95 g/cm3 | 4.05 g/cm3 |
| Boiling point: | 967°C | |
| Melting point: | sublimation above 700°C | 568°C |
| Solvolysis/solubility: | in water: very slightly (0.005 wt%) readily soluble in diluted acids |
in water: readily soluble (1,400 g/l) |
ORIGIN AND USE
Usage:
Metallic cadmium is used to coat iron in order to improve
corrosion resistance and in alloys in the automobile industry.
Its compounds are used as pigments (primarily as cadmium
sulphide) and as plastic stabilisers in PVC, in batteries and in
fungicides; also applied for Ni-Cd batteries as well as
moderators and control elements in nuclear reactors.
Origin/derivation:
Cadmium minerals are rare; frequently found in isomorphic form in
nearly all zinc ores (95 % of cadmium production). Cadmium
is separated from Zn by distillation or precipitation from
sulphate solution using zinc dust.
Production figures:
1980 = 18 x 103 t (worldwide); MERIAN, 1984
Toxicity
| Mammals: | ||
| Rat | LDLo 15 mg/kg, ims | acc. KOCH, 1989 |
| Rat | TDLo 70 mg/kg, ims | acc. KOCH, 1989 |
| Rat | LD50 88 mg/kg , (cadmium chloride) | acc. DVGW, 1988 |
| Rat | LD50 72 mg/kg , (cadmium oxide) | acc. DVGW, 1988 |
| Rabbit | LD50 70-150 mg/kg , (cadmium chloride) | acc. DVGW, 1988 |
| Guinea pig | LD 150 mg/kg , cadmium fluoride | acc. DVGW, 1988 |
| Aquatic organisms: | ||
| Daphnia | 0.1 mg/l (harmful) | acc. DVGW, 1988 |
| Stickleback | 0.3 mg/l (harmful) | acc. DVGW, 1988 |
| Minnow | LD 5600 mg/l (1 h) | acc. DVGW, 1988 |
| Goldfish | LD 0.017 mg/l (9-18 h) | acc. DVGW, 1988 |
| Fish (without spec. differentiation) | LC50 minimal 23 ppm (over 264 h) | acc. KOCH, 1989 |
| LC50 average 140 ppm (over 24 h) | acc. KOCH, 1989 | |
Characteristic effects:
Humans/mammals: Apart from the gastro-intestinal tract and the lungs, the organ most susceptible to chronic cadmium exposure is the kidney. Cadmium is a cumulative poison; the ready solvolyse of the element in weak acids is an important precondition for its absorption in the organism: 5 % of cadmium is resorbed via the gastro-intestinal tract and accumulated in liver and kidneys. In Asia, "Itai-Itai" disease is caused by high cadmium concentrations in rice. Damage is caused by erythrocyte destruction, proteinuria, rhinitis, emphysema and chronic bronchitis. Cadmium and its compounds are carcinogenic. A typical symptom of chronic poisoning is the excretion of ß-microglobulin in the urine due to the impairment of the kidney function. Bone deformation may also result.
Plants: Cadmium reduces the photosynthesis and transpiration rate whilst increasing the respiratory rate. Small cadmium concentrations in the soil are sufficient to produce marked damage such as shortening of the shoot axis and intensive yellowing of older leaves. Absorption not only takes place via the roots but also through shoots and leaves. In addition to yield shortfalls the main hazard results from the contamination of (accumulation in) crop plants since this is how cadmium as a cumulative poison enters the food chain.
ENVIRONMENTAL BEHAVIOUR
Water:
2/3 - 3/4 of the cadmium in surface water and groundwater is
adsorbed on suspended matter. It can be remobilised from sediment
by complexing agents. Fish toxicity is dependent amongst other
things on the calcium content of the water. Generally speaking, a
high calcium content in water reduces the toxic effect of cadmium
on fish.
The biological self-purification of surface water and groundwater
is impaired from 0.1 mg/l (DVGW, 1988).
Air:
Cadmium is stable in air since it forms an oxide layer.
Soil:
The cadmium retention capacity is a function of the number of
exchangeable alkalis. There is hardly any elution because of the
adsorption on organic soil components. The accumulation horizon
for cadmium is in the rhizosphere (roots). The minimum
availability is at pH 6.5. The cadmium absorption by plants
increases with a decreasing pH of the soil.
Degradation, decomposition products, half-life:
Cadmium accumulates in the organism. 50 % of the
accumulated amount is found in the liver and the kidneys. Cadmium
is primarily excreted in urine (2 m
g/d on average (0.2 - 3.1 m
g/l)). The biological half-life of cadmium in the human body is
between 15 and 25 years (measured in the kidneys; GROßKLAUS,
1989).
Food chain:
Humans consume roughly one third of the cadmium to which they
are exposed in animal foodstuffs and two thirds in vegetable
foodstuffs. Smoking significantly increases the cadmium impact.
Note: 1) The biological half-life is the time taken for a specified element concentration in the body to be reduced to half its original value by way of degradation and excretion processes.
ENVIRONMENTAL STANDARDS
| Medium/acceptor | Sector | Country/organ. | Status |
Value | Cat. | Remarks | Source |
| Water: | Drinkw | AUS | (L) |
10 µg/l | acc. MERIAN, 1984 | ||
| Drinkw | CH | (L) |
5 µg/l | acc. MERIAN, 1984 | |||
| Drinkw | D | L |
5 µg/l | Amendment, 1985 | acc. DVGW, 1988 | ||
| Drinkw | EC | G |
5 µg/l | acc. LAU-BW, 1989 | |||
| Drinkw | SU | (L) |
10 µg/l | acc. MERIAN, 1984 | |||
| Drinkw | USA | (L) |
0.01 mg/l | acc. DVGW, 1988 | |||
| Drinkw | WHO | G |
5 µg/l | acc. MERIAN, 1984 | |||
| Surface | D | L |
50 µg/m3 | Investigation | acc. LAU-BW, 1989 | ||
| Surface | D | L |
100 µg/m3 | Rehabilitation | acc. LAU-BW, 1989 | ||
| Surface | D | G |
0.005 mg/l | 1) A | acc. DVGW, 1988 | ||
| Surface | D | G |
0.01 mg/l | 2) B | acc. DVGW, 1988 | ||
| Groundw | D(HH) | G |
2.5 µg/l | Investigation | acc. LAU-BW, 1989 | ||
| Groundw | D(HH) | G |
10 µg/l | Rehabilitation | acc. LAU-BW, 1989 | ||
| Groundw | NL | G |
0.4 µg/l | Reference | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
6 µg/l | Intervention | acc. TERRA TECH 6/94 | ||
| Waste water | CH | (L) |
0.10 g/m3 | Direct/indirect introduc. | acc. LAU-BW, 1989 | ||
| Waste water | CH | G |
0.005 g/m3 | Quality aim | acc. LAU-BW, 1989 | ||
| Waste water | D(BW) | G |
1 g/m3 | acc. LAU-BW, 1989 | |||
| Trough water | D | L |
6 µg/l | acc. DVGW, 1988 | |||
| Soil: | CH | G |
0.8 mg/kg AD | acc. LAU-BW, 1989 | |||
| CH | G |
0.03 mg/kg | Sol. content | acc. LAU-BW, 1989 | |||
| D(HH) | G |
8 mg/kg DS | Investigation | acc. LAU-BW, 1989 | |||
| NL | G |
0.8 mg/kg AD | Reference | acc. TERRA TECH 6/94 | |||
| NL | L |
12 mg/kg AD | Intervention | acc. TERRA TECH 6/94 | |||
| Sewage sludge | CH | L |
30 mg/kg DS | Sludge | acc. LAU-BW, 1989 | ||
| Sewage sludge | D | L |
3 mg/kg AD | Soil | acc. LAU-BW, 1989 | ||
| Sewage sludge | D | L |
20 mg/kg DS | Sludge DS | acc. LAU-BW, 1989 | ||
| Sewage sludge | EC | L |
1-3 mg/kg DS | Soil DS | acc. LAU-BW, 1989 | ||
| Sewage sludge | EC | L |
20 -.40 mg/kg DS | Sludge DS | acc. LAU-BW, 1989 | ||
| Fertiliser | D | L |
4 mg/kg | 3) | acc. LAU-BW, 1989 | ||
| Fertiliser | D | L |
3 mg/kg | Soil AD | acc. LAU-BW, 1989 | ||
| Fertiliser | D | L |
20 mg/kg | Sludge | acc. LAU-BW, 1989 | ||
| Compost | A | G |
1-6 ppm | acc. LAU-BW, 1989 | |||
| Compost | CH | L |
3 mg/kg | acc. LAU-BW, 1989 | |||
| Compost | D | G |
3 mg/kg | Soil AD | acc. LAU-BW, 1989 | ||
| Compost | D | G |
33 g/ha and a | acc. LAU-BW, 1989 | |||
Air: |
CH | L |
10 ng/m3 | 7) | acc. LAU-BW, 1989 | ||
| CH | L |
2 µg/m3 and d | In dust deposition | acc. LAU-BW, 1989 | |||
| D | L |
0.04 µg/m3 | IW1 | 5) 6) | acc. TA Luft, 1986 | ||
| D | L |
5 µg/m3 and d | IW1 | 5) 7) | acc. TA Luft, 1986 | ||
| WHO | G |
1-5 ng/m3 | 8) | acc. LAU-BW, 1989 | |||
| WHO | G |
10-20 ng/m3 | 9) | acc. LAU-BW, 1989 | |||
| Emiss. | D | L | 0.2 mg/m3 | mass flow > 50 g/h10) | acc. TA Luft, 1986 | ||
| Workp | AUS | L |
0.05 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | AUS | L |
0.05 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | B | L |
0.05 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | B | L |
0.05 mg/m3 | Manufacture, Cd oxide | acc. MERIAN, 1984 | ||
| Workp | B | L |
0.05 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | BG | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | CS | L |
0.1 mg/m3 | Cd oxide, smoke, Cd 11) | acc. MERIAN, 1984 | ||
| Workp | CS | L |
0.5 mg/m3 | Cd oxide, smoke, Cd 12) | acc. MERIAN, 1984 | ||
| Workp | CH | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | CH | L |
0.2 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | D | L |
1.5 µg/dl | BAT | Whole blood | acc. DVGW, 1988 | |
| Workp | D | L |
15 µg/l | BAT | Urine | acc. DVGW, 1988 | |
| Workp | DDR | L |
0.1 mg/m3 | Dust and sol. salts 11) | acc. MERIAN, 1984 | ||
| Workp | DDR | L |
0.2 mg/m3 | Dust and sol. salts 12) | acc. MERIAN, 1984 | ||
| Workp | NL | L |
0.05 mg/m3 | Manufacture, Cd oxide | acc. MERIAN, 1984 | ||
| Workp | NL | L |
0.05 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | NL | L |
0.05 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | H | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | I | L |
0.05 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | I | L |
0.01 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | J | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | PL | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | RO | L |
0.2 mg/m3 | Cd oxide, smoke, Cd 12) | acc. MERIAN, 1984 | ||
| Workp | S | L |
0.05 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | S | L |
0.02 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | SF | L |
0.02 mg/m3 | Dust and sol. salts | acc. MERIAN, 1984 | ||
| Workp | SF | L |
0.01 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | SU | L |
0.1 mg/m3 | Cd oxide | acc. KETTNER, 1979 | ||
| Workp | SU | L |
0.3 mg/m3 | Cd hydroxide | acc. KETTNER, 1979 | ||
| Workp | SU | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Workp | USA | L |
0.1 mg/m3 | Cd oxide, smoke, Cd 11) | acc. MERIAN, 1984 | ||
| Workp | USA | L |
0.3 mg/m3 | Cd oxide, smoke, Cd 12) | acc. MERIAN, 1984 | ||
| Workp | USA | (L) |
0.05 mg/m3 | TWA | acc. DVGW, 1988 | ||
| Workp | USA | L |
0.2 mg/m3 | Dust and sol. salts 11) | acc. MERIAN, 1984 | ||
| Workp | USA | L |
0.6 mg/m3 | Dust and sol. salts 12) | acc. MERIAN, 1984 | ||
| Workp | USA | (L) |
0.05 mg/m3 | TWA | Smoke, Cd oxide | acc. ACGIH, 1986 | |
| Workp | USA | (L) |
0.05 mg/m3 | TWA | Manufacture, Cd oxide | acc. ACGIH, 1986 | |
| Workp | WHO | L |
0.01 mg/m3 | Dust and sol. salts 13) | acc. MERIAN, 1984 | ||
| Workp | WHO | L |
0.25 mg/m3 | Dust and sol. salts 12) | acc. MERIAN, 1984 | ||
| Workp | YU | L |
0.1 mg/m3 | Cd oxide, smoke, as Cd | acc. MERIAN, 1984 | ||
| Foodstuffs: | WHO | G |
0.07 mg/d | acc. RÖMPP, 1979 | |||
| D | L |
0.005 mg/l | Mineral water | acc. DVGW, 1988 | |||
| D | G |
0.0025 mg/kg | Milk | acc. GROßKLAUS, 1989 | |||
| D | G |
0.05 mg/kg | Cheese | acc. GROßKLAUS, 1989 | |||
| D | G |
0.1 mg/kg | Beef | acc. GROßKLAUS, 1989 | |||
| D | G |
0.1 mg/kg | Sausage meat | acc. GROßKLAUS, 1989 |
Notes:
1) For drinking water treatment in each case: A = signifies pollution limits up to which water can be used as drinking water
2) For drinking water treatment in each case: B = signifies pollution limits up to which drinking water can be produced with the assistance of currently known and proven chemophysical methods
3) In organ.-mineral, mixed fertiliser
4) Annual arithmetic mean, in suspended dust
5) Annual arithmetic mean on the basis of daily mean values, protection of humans
6) Cd and its anorganic compounds as suspended dust, stated as Cd
7) Cd and its anorganic compounds within dust sediments, stated as Cd
8) Averaging period: 1 year (rural areas); protection of humans
9) Averaging period: 1 year (urban areas); protection of humans
10) dustlike Cd ist and anorganic compounds, stated as Cd
11) Mean value
12) Short-time value
13) Long-time value
14) Tolerable weekly absorption
Further regulations in: Order Governing Cosmetics, 1985: Ban on usage; Law Governing Paints, 1987. Usage prohibited in the manufacture of foodstuffs, semi-luxury goods and consumer goods; the utilisation of Cd compounds as pesticides is prohibited in Germany.
Comparison/reference values
| Medium/origin | Country | Value | Source |
| Surface water | |||
| Rhine (Cologne): | D | 0.03 - 0.2 µg/l | acc. DVGW, 1988 |
| Rhine (Duisburg): | D | 0.05 - 0.5 µg/l | acc. DVGW, 1988 |
| Ruhr (Witten): | D | 0.2 - 2.1 µg/l | acc. DVGW, 1988 |
| Ruhr (Duisburg): | D | 0.4 - 0.6 µg/l | acc. DVGW, 1988 |
| Fertiliser (in 100 kg P2O5): | USA | 1.2 - 2.4 g Cd/ha | acc. BREMER UMWELT INST., 1985 |
| Morocco | 3.5 - 7 g Cd/ha | acc. BREMER UMWELT INST., 1985 | |
| SU | 3.6 - 7.2 g Cd/ha | acc. BREMER UMWELT INST., 1985 | |
| Senegal | 11.4 - 22.8 g Cd/ha | acc. BREMER UMWELT INST., 1985 | |
| Fly ash (coal) | USA | 0.1-3.9 mg/kg | acc. HOCK, 1988 |
| Plants | 0.05-0.2 mg/kg | acc. HOCK, 1988 | |
Assessment/comments
As a trace element, cadmium is subject to constant circulation
in biological and non-biological environmental structures. The
impact on the environment which cadmium causes by natural means
(approx. 40 t/a worldwide) is slight compared to the
estimated anthropologically-induced emissions. Cadmium is
regarded as one of the most poisonous metals. There have been
documented cases of acute and chronic poisoning due to workplace
exposure. Cadmium is one of the trace elements for which there is
proof of poisoning of certain groups of people as a consequence
of chronic, environment-related exposure.
The proven accumulation of the element in sediments, the
associated possibility of remobilisation and the tendency towards
bioaccumulation are the major environmental hazards. If possible,
waste products containing cadmium should be reprocessed.