Fluorine

Fluorine is a chemical element with symbol F and atomic number 9.

Uses

Fluorine and its compounds – mostly uranium hexafluoride – are used in processing nuclear fuel.
Fluorochemicals, including many high-temperature plastics such as Teflon, are also made using fluorine.
Compounds of fluorine, including sodium fluoride, are used in toothpaste and in drinking water to prevent dental cavities.
Hydrofluoric acid can dissolve glass and is used to etch the glass in light bulbs and in other products.
Chlorofluorocarbons (CFCs) were used in as refrigerants in air conditioning units and freezers but they have now been banned because they contribute to ozone depletion.

Dental care: Population studies from the mid-20th century onwards show topical fluoride reduces dental caries. This was first attributed to the conversion of tooth enamel hydroxyapatite into the more durable fluorapatite, but studies on pre-fluoridated teeth refuted this hypothesis, and current theories involve fluoride aiding enamel growth in small caries
Pharmaceuticals: Twenty percent of modern pharmaceuticals contain fluorine. One of these, the cholesterol-reducer atorvastatin (Lipitor), made more revenue than any other drug until it became generic in 2011. The combination asthma prescription Seretide, a top-ten revenue drug in the mid-2000s, contains two active ingredients, one of which – fluticasone – is fluorinated. Many drugs are fluorinated to delay inactivation and lengthen dosage periods because the carbon–fluorine bond is very stable. Fluorination also increases lipophilicity because the bond is more hydrophobic than the carbon–hydrogen bond, and this often helps in cell membrane penetration and hence bioavailability.

Elemental fluorine is highly toxic to living organisms. Its effects in humans start at concentrations lower than hydrogen cyanide’s 50 ppm and are similar to those of chlorine: significant irritation of the eyes and respiratory system as well as liver and kidney damage occur above 25 ppm, which is the immediately dangerous to life and health value for fluorine. Eyes and noses are seriously damaged at 100 ppm, and inhalation of 1,000 ppm fluorine will cause death in minutes, compared to 270 ppm for hydrogen cyanide.

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