Sources and pathways of cadmium in the environment.

Cadmium occurs naturally in rocks and soils, usually in concentrations of less than 1 microgram/g, but soils derived from some marine black shales and from rocks containing lead-zinc minerals frequently contain much larger amounts. These may lead to increased cadmium uptake by crops and vegetables grown for human consumption. Anthropogenic sources, including smelter emissions and the application of fertilizers and sewage sludge to land, may lead to contamination of both soils and crops. Regional cadmium enrichment or contamination of the surface environment can be delineated by geochemical surveys and by the compilation of soil inventories. The factors influencing the uptake of cadmium into food crops and the role of the atmosphere and soil as sources of cadmium in the diet and water supplies are discussed. No adverse health effects related to cadmium were found in an area where the cadmium intake of the local population was double the estimated United Kingdom average.