Cadmium has been discovered in the painted design on ‘Shrek’-themed drinking glasses being sold nationwide at McDonald’s, forcing the burger giant to recall 12 million of the cheap U.S.-made collectibles.
Cadmium is a known carcinogen and gradually accumulates in the body. Cadmium is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low melting point compared to transition metals. Cadmium and its congeners are not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. Cadmium is a relatively abundant element. Cadmium was discovered in 1817 by Friedrich Stromeyer as an impurity in zinc carbonate.
Cadmium occurs as a minor component in most zinc ores and therefore is a by-product of zinc production. Cadmium was for a long time used as pigment and for corrosion resistant plating on steel. Cadmium compounds were used to stabilize plastic. With the exception of its use in nickel-cadmium batteries and cadmium telluride solar panels, the use of cadmium is generally decreasing in all other applications. This decrease is due to the high toxicity and carcinogenicity of cadmium and the associated health and environmental concerns. Although cadmium is toxic, one enzyme, a carbonic anhydrase with cadmium as reactive center has been discovered.
Cadmium has no constructive purpose in the human body. Cadmium and its compounds are extremely toxic even in low concentrations, and will bioaccumulate in organisms and ecosystems.
Clinical Effects
Acute exposure to cadmium fumes may cause flu like symptoms including chills, fever, and muscle ache sometimes referred to as “the cadmium blues.” Symptoms may resolve after a week if there is no respiratory damage. More severe exposures can cause tracheo-bronchitis, pneumonitis, and pulmonary edema. Symptoms of inflammation may start hours after the exposure and include cough, dryness and irritation of the nose and throat, headache, dizziness, weakness, fever, chills, and chest pain.
Inhaling cadmium-laden dust quickly leads to respiratory tract and kidney problems which can be fatal (often from renal failure). Ingestion of any significant amount of cadmium causes immediate poisoning and damage to the liver and the kidneys. Compounds containing cadmium are also carcinogenic.
The bones become soft (osteomalacia), lose bone mineral density (osteoporosis) and become weaker. This causes the pain in the joints and the back, and also increases the risk of fractures. In extreme cases of cadmium poisoning, mere body weight causes a fracture.
The kidneys lose their function to remove acids from the blood in proximal renal tubular dysfunction. The kidney damage inflicted by cadmium poisoning is irreversible. The proximal renal tubular dysfunction creates low phosphate levels in the blood (hypophosphatemia), causing muscle weakness and sometimes coma. The dysfunction also causes gout, a form of arthritis due to the accumulation of uric acid crystals in the joints because of high acidity of the blood (hyperuricemia). Another side effect is increased levels of chloride in the blood (hyperchloremia). The kidneys can also shrink up to 30%.
Other patients lose their sense of smell (anosmia).
Itai-itai disease (“ouch ouch sickness”), was the documented case of mass cadmium poisoning in Toyama Prefecture, Japan. The cadmium poisoning caused softening of the bones and kidney failure. The disease is named for the severe pains caused in the joints and spine. The term itai-itai disease was coined by locals. The cadmium was released into rivers by mining companies in the mountains. The mining companies were successfully sued for the damage. Itai-itai disease is known as one of the Four Big Pollution Diseases of Japan.