2.3.3 Nuclear Fission
In a nuclear reactor during nuclear fission, neutrons are liberated that leads to chain
reaction. Cadmium acts as a very effective neutron poison and is used in the form of
control rods to control neutron flux in nuclear fission (Scoullos et al. 2001).
2.3.4 Cadmium Compounds
Cadmium compounds have various industrial applications. Cadmium oxide is used
in Ni–Cd batteries, as a catalyst, in resistant enamels, in heat-resistant plastics, in the
blue and green phosphors of color television cathode ray tubes, and in the
manufacture of plastics (such as Teflon). Cadmium chloride is used in electroplating,
photocopying, calico printing, dyeing, mirrors, analytical chemistry, vacuum tubes,
and lubricants. Cadmium nitrate is used in photographic emulsions to color glass and
porcelain, in nuclear reactors, and to produce cadmium hydroxide for use in alkaline
batteries. Cadmium sulfate is used in electroplating, fluorescent screens, vacuum
tubes, and analytical chemistry and as a chemical intermediate to produce pigments,
stabilizers, and other cadmium compounds. Cadmium sulfide (CdS) and cadmium
selenide (CdSe) are used to color paints and plastics as these cadmium compounds
can withstand high temperatures and disperse well in polymers producing strong
colors with high opacity and good tinting strength (Herron 2001; ATSDR 2008).
2.3.5 PVC Stabilizers
Cadmium is an important stabilizer for polyvinyl chloride (PVC) that helps retard
degradation when these products are exposed to either (or both) ultraviolet light or
heat. Cadmium-containing stabilizers are found in everyday PVC items as door and
window frames, hoses, drain and water pipes, and electrical insulation (Herron 2001;
UNEP 2008).
3 Sources of Cadmium Contamination in Environment
Two major sources of cadmium emission in the environment are natural and
anthropogenic activities.
3.1 Natural Sources
In nature cadmium occurs both in the earth’s crust and in ocean water. In the earth’s
crust, concentration of cadmium is very meager (0.1–0.5 mg/kg), but its accumulation in sedimentary rocks, marine phosphate, and phosphorites may be much, as high
as 500 mg/kg (WHO 1992). From these two reservoirs, cadmium is released by
15 Cadmium as an Environmental Pollutant: Ecotoxicological Effects, Health. . .
361
In a nuclear reactor during nuclear fission, neutrons are liberated that leads to chain
reaction. Cadmium acts as a very effective neutron poison and is used in the form of
control rods to control neutron flux in nuclear fission (Scoullos et al. 2001).
2.3.4 Cadmium Compounds
Cadmium compounds have various industrial applications. Cadmium oxide is used
in Ni–Cd batteries, as a catalyst, in resistant enamels, in heat-resistant plastics, in the
blue and green phosphors of color television cathode ray tubes, and in the
manufacture of plastics (such as Teflon). Cadmium chloride is used in electroplating,
photocopying, calico printing, dyeing, mirrors, analytical chemistry, vacuum tubes,
and lubricants. Cadmium nitrate is used in photographic emulsions to color glass and
porcelain, in nuclear reactors, and to produce cadmium hydroxide for use in alkaline
batteries. Cadmium sulfate is used in electroplating, fluorescent screens, vacuum
tubes, and analytical chemistry and as a chemical intermediate to produce pigments,
stabilizers, and other cadmium compounds. Cadmium sulfide (CdS) and cadmium
selenide (CdSe) are used to color paints and plastics as these cadmium compounds
can withstand high temperatures and disperse well in polymers producing strong
colors with high opacity and good tinting strength (Herron 2001; ATSDR 2008).
2.3.5 PVC Stabilizers
Cadmium is an important stabilizer for polyvinyl chloride (PVC) that helps retard
degradation when these products are exposed to either (or both) ultraviolet light or
heat. Cadmium-containing stabilizers are found in everyday PVC items as door and
window frames, hoses, drain and water pipes, and electrical insulation (Herron 2001;
UNEP 2008).
3 Sources of Cadmium Contamination in Environment
Two major sources of cadmium emission in the environment are natural and
anthropogenic activities.
3.1 Natural Sources
In nature cadmium occurs both in the earth’s crust and in ocean water. In the earth’s
crust, concentration of cadmium is very meager (0.1–0.5 mg/kg), but its accumulation in sedimentary rocks, marine phosphate, and phosphorites may be much, as high
as 500 mg/kg (WHO 1992). From these two reservoirs, cadmium is released by
15 Cadmium as an Environmental Pollutant: Ecotoxicological Effects, Health. . .
361