Lithium is an alkali metal similar to magnesium and sodium in its properties. It does not occur in nature in its elemental form, primarily because it readily reacts with water to form lithium hydroxide. It is found in minerals such as spodumene, petalite, and eucryptite. Lithium is also found in natural waters (particularly mineral waters) as well as in foods. The daily dietary intake of lithium has been estimated to be about 2 mg for humans. Inorganic salts or oxides of lithium have many uses. Lithium carbonate and lithium borate are used in the ceramics industry, and lithium chloride and fluoride are used in welding and brazing fluxes. Lithium carbonate is used extensively as a therapeutic agent in the treatment of manic depressive affective disorders; it has also been used as an anti-gout medication. In the 1940s, lithium chloride was used as a salt substitute for patients on a low-salt diet; however, this use was discontinued following the occurrence of lithium intoxication and death in some patients. In addition, lithium hydride is used as a nuclear reactor coolant. Lithium is also used in alloys, and the hydroxide is used in alkaline storage batteries. Lithium forms organometallic compounds, some of which have important industrial uses: lithium stearate and other fatty acid forms are used as multipurpose greases, particularly in the automotive industry.
Soluble lithium compounds are readily absorbed through the digestive tract but not the skin. The oral toxicity of most lithium compounds is relatively low. Case histories indicate that doses of 12-60 g can result in coma, respiratory and cardiac complications, and death in humans. A single oral dose of 40 mg/kg produced toxic lithium blood levels in a patient with a history of prior lithium use. In contrast, for chronic therapeutic use, the standard dose of lithium carbonate is 1-2 g/day. Signs and symptoms of lithium toxicity include anorexia; nausea; diarrhea; alopecia; weight gain; thirst; sodium retention; polyuria; glycosuria; aplastic anemia; tremors; acne; muscle spasm; and, rarely, dysarthria, ataxia, impaired cognition, and pseudotumor cerebri. Toxic effects that may appear after prolonged therapeutic use may include neurological symptoms, changes in kidney function, hypothyroidism, and leukocytosis. Limited information is available on the inhalation toxicity of lithium compounds. Lithium hydride is a respiratory tract irritant.
Little information was found in the available literature on the carcinogenicity of lithium compounds. However, three patients on chronic lithium therapy developed leukemia, and one developed a thyroid tumor. Lithium has not been classified by EPA as to its potential carcinogenicity.