Chronic Geographical areas associated with groundwater having over 1.5 mg/L of naturally occurring<unk> , which is above recommended levels. In India an estimated 60 million people have been poisoned by well water contaminated by excessive<unk> , which is dissolved from the granite rocks. The effects are particularly evident in the bone deformities of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia. Acute Historically, most cases of acute<unk>  have followed accidental ingestion of sodium<unk>  based insecticides or rodenticides. Currently, in advanced countries, most cases of<unk>  exposure are due to the ingestion of dental<unk>  products. Other sources include glass-etching or chrome-cleaning agents like ammonium bifluoride or hydrofluoric acid, industrial exposure to fluxes used to promote the flow of a molten metal on a solid surface, volcanic ejecta (for example, in cattle grazing after an 1845–1846 eruption of Hekla and the 1783–1784 flood basalt eruption of Laki), and metal cleaners. Malfunction of water<unk> tion equipment has happened several times, including a notable incident in Alaska.
Fluoride toxicity
Fluorine deficiency
Chromium toxicity
Copper toxicity
Boron deficiency 
Lead poisoning
Zinc toxicity
Chromium deficiency