Fluorine has been reported as the thirteenth most abundant element present in the earth. Fluorine being the most chemically reactive and electronegative of all the elements and forms number of compounds. Compounds containing fluorine anions are called fluorides.
Fluorine exists as fluoride bounded to both organic and inorganic cations. Fluorides exist in nature in inert form such as calcium fluoride to highly reactive forms such as sulfur tetra fluoride. The main sources of fluoride in nature are weathering of rocks, emissions from volcanoes, seawater etc. The anthropogenic sources like mining of phosphate rocks, phosphate fertilizers in agricultural fields and fluoridation of drinking-water supplies also adds fluoride in soil and water.
Fluorides are taken up by plants from soil and water.