<unk>  is a condition in which there are elevated levels of the<unk>  ion in the body. Although<unk>  is safe for dental health at low concentrations, sustained consumption of large amounts of soluble<unk>  salts is dangerous. Referring to a common salt of<unk> , sodium<unk>  (NaF), the lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg elemental<unk> /kg body weight). Ingestion of<unk>  can produce gastrointestinal discomfort at doses at least 15 to 20 times lower (0.2–0.3 mg/kg or 10 to 15 mg for a 50 kg person) than lethal doses. Although it is helpful topically for dental health in low dosage, chronic ingestion of<unk>  in large amounts interferes with bone formation. In this way, the most widespread examples of<unk>  poisoning arise from consumption of ground water that is abnormally<unk> -rich.
Fluoride toxicity
Fluorine deficiency
Chromium toxicity
Copper toxicity
Boron deficiency 
Lead poisoning
Zinc toxicity
Chromium deficiency