How is cadmium released in the environment?

Atmospheric deposition

In most industrialized countries atmospheric deposition results from town waste incineration, non-ferrous metal production, iron and steel production and fossil fuel combustion. Although airborne cadmium has been declining since the mid-1960s as a result of emission reductions, there is still a significant input from this source.

Animal manure

It contains cadmium because the metal is present in grazed herbage, imported and domestically produced animal feed and cadmium impurities in phosphate feed-additives (the cadmium content in feed phosphate is, however, low). Over 90% of the cadmium ingested by animals passes into manure. If large quantities of manure are applied to limited areas of land in order to dispose of them, the pollution risk is considerable. This problem occurs in regions with intensive livestock enterprises, in Europe particularly in the Netherlands, Belgium, Denmark, North Germany and Brittany in France. However, these regions together represent less than 0.5% of the world's arable and permanent crop area and remedies applicable to them may not be suitable models for other regions.

Crops

Crops grown on soil contaminated with cadmium or irrigated with water polluted with cadmium may absorb the metal. Tobacco and food crops such as rice are the main sources of cadmium intake for non-occupationally exposed people.

Soils

Cadmium can also be naturally occurring in the soil. There is in fact a wide range of cadmium in the natural soil content, depending on the mother rock.

Phosphate fertilizers

Manure and sludge remain notable sources of cadmium addition to the soil. Phosphate rock deposits of sedimentary origin contain higher levels of cadmium than those of igneous origin. Most phosphate rock deposits are of sedimentary origin and, therefore, contain cadmium.