The chemical symbol fluorine F is very abundant in the earth's crust, representing about 300 mg/kg3 of its composition. It is the most electronegative chemical element of the periodic table and the most reactive, not being free, but always combined with calcium, sodium, aluminum, as fluoride (F-) and sometimes as part Of the composition of some silicates.

Fluorides are ubiquitous, present in the soil, forming part of the composition of many minerals, such as fluorite (CaF2), cryolite (Na3Al F6), fluorapatite Ca5(PO4)3 F; In air (particulate form) and dissolved in water.

Their existence in the environment is due in part to natural sources, including volcanic activity and marine aerosols and anthropogenic or man-made sources resulting from all man's activity, including the manufacture of steel, primary production of aluminum, copper and nickel production, pesticide production, the production and use of phosphate fertilizers, the manufacture of glass, ceramics, glue and adhesives etc.

Fluoride, which occurs in biological fluids such as fluoride ion F-. In cases of occupational exposure or food and water for human consumption, excessive levels of fluoride in the body may cause health risk. Fluoride is easily determined using the meters available from EMI LDA.