Cadmium as an environmental hazard

Cadmium occurs in nature at low concentrations, but human activities have caused cadmium contamination in all continents with the exception of Antarctica. In some areas, environmentally exposed humans have suffered kidney damage which has sometimes progressed to severe kidney failure and skeletal disease. In mammals and birds, cadmium accumulates in livers and kidneys at concentrations of 0.1-2 mg/kg and 1-10 mg/kg wet weight, respectively. Animals with a long life span such as horses have very high concentrations of cadmium in their organs: in renal cortex samples obtained from old horses, concentrations of nearly 200 mg/kg have been found. Histopathological examination of kidneys from environmentally exposed horses and certain species of sea birds have revealed morphological changes indicative of chronic interstitial nephritis. Remarkably high concentrations of cadmium (5-160 mg/kg) have recently been found in kidneys obtained from penguins living in Antarctica. The cadmium accumulation observed in animals living in Antarctica is unlikely to be the result of anthropogenic pollution. It shows how little we know and understand about the natural flow and behaviour of this elusive element in the ecosystems of the planet.