Cadmium
CADMIUM is a natural element of the earth, usually found in combination with such other elements as oxygen (cadmium oxide), chlorine (cadmium chloride), or sulfur (cadmium sulfate/sulfide). It is a trace mineral in the body with concentrations mainly in the liver and kidneys. Whether it is an essential element for human health has not yet been determined, but nutritional requirements seem to be easily met within the diet. Even though it is widely distributed in seafoods, grains, air, and water, only about 6% of dietary cadmium is absorbed.
Cadmium came into industrial use during the 20th century, and is used mainly in the production of batteries, pigments, metal coatings, and plastics. This mineral accumulates in the bones and teeth and has a half-life of up to forty years, with levels increasing with age. Cadmium poisoning is mainly an industrial hazard, but chronic ingestion can lead to retarded growth, hypertension, and renal dysfunction. The first signs of toxicity include nausea and vomiting with abdominal cramping, followed by renal damage and disturbances in calcium metabolism leading to osteomalacia. This condition is characterized by skeletal brittleness and bone fracturing. It was first noted in Japanese peasants who consumed rice contaminated with cadmium. Their cries of itai-itai (ouch-ouch) as their bones broke determined the name of the disease, which is also known as adult rickets.
When industrial pollution occurs, levels can climb from a trace to more than twenty times the ordinary, as was the case in Japan. Fish caught off the coast of the United States have contained three times ordinary trace levels. Zinc nearly always contains a significant amount of cadmium, which is readily leached from zinc plating by hot acidic water. Some phosphate fertilizers are rich in cadmium, as is sewage sludge used as fertilizer on agricultural land. Cadmium is included as a possible necessary nutrient because science has suggested that it could contribute to growth factor activity since it has been found to stimulate cell growth in agar. How this relates to human nutrition is still being investigated. Toxicity, rather than a deficiency, is more of a concern with this mineral.
