It increases deposition of calcium, thereby strengthening bones. Fluorine can destroy the enzyme phosphotase, which is vital to many body processes including the metabolism of vitamins. Also a problem for brain tissues. Aluminum salts of fluorine and insoluble calcium interfere with fluorine absorption. Calcium is an antidote to poisoning.
Fluorine is a highly reactive pale yellow gas, and found in igneous and sedimentary rock.
Soluble F is absorbed in gastrointestinal tract, and digestion depends upon solubility. High F can be in water from deep wells, or geothermal sources. 2 ppm F is the upper limit. Fluoride deposits can be on food from containment. Excessive F causes mottled teeth enamel.