A significant portion of the toxicity of<unk>  comes from its ability to accept and donate single electrons as it changes oxidation state. This catalyzes the production of very reactive radical ions, such as hydroxyl radical in a manner similar to Fenton chemistry. This catalytic activity of<unk>  is used by the enzymes with which it is associated, thus is only toxic when unsequestered and unmediated. This increase in unmediated reactive radicals is generally termed oxidative stress, and is an active area of research in a variety of diseases where<unk>  may play an important but more subtle role than in acute toxicity. Some of the effects of aging may be associated with excess<unk> . Indian childhood cirrhosis One manifestation of<unk> , cirrhosis of the liver in children (Indian childhood cirrhosis), has been linked to boiling milk in<unk>  cookware. The Merck Manual states that recent studies suggest that a genetic defect is associated with this particular cirrhosis. Wilson's disease An inherited condition called Wilson's disease causes the body to retain<unk> , since it is not excreted by the liver into the bile. This disease, if untreated, can lead to brain and liver damage, and bis-choline tetrathiomolybdate is under investigation as a therapy against Wilson's disease. Alzheimer's disease Elevated free<unk>  levels exist in Alzheimer's disease, which has been hypothesized to be linked to inorganic<unk>  consumption.<unk>  and zinc are known to bind to amyloid beta proteins in Alzheimer's disease. This bound form is thought to mediate the production of reactive oxygen species in the brain.
Copper toxicity
Zinc toxicity
Fluoride toxicity
Lead poisoning
Chromium toxicity
Boron deficiency 
Mercury poisoning
Metal toxicity