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Also see Fluorine. Moderate amounts are protective against dental caries. This might best be delivered in some populations in the water supply and in others as supplements such as in toothpaste[1] although high risk populations are less likely to access the later[2]. There is minimal antimicrobial action but it is permissive to re-mineralisation. Excess can lead to skeletal abnormalities and may act as a developmental neurotoxin[3].

The levels of hysteria, quackery and pure rubbish generated around this ion compare with that from antivaccinationists.

We evolved around the Rift Valley in Africa, which has a high fluoride level in rocks and groundwater. Many other areas of the planet might be less suited to us, or vice versa. Low fluoride levels would be one of the easiest faults for terraforming to correct, but in the absence of this, use other means to keep human dietary intake optimal.

Also used as an enzyme inhibitor, e.g. for serum glucose measurement where it inhibits ex vivo breakdown of glucose by red blood cell enolase (via glycolysis). Similarly, in post-mortem toxicology specimens, fluoride also inhibits bacterial enzymes and is used for alcohol measurements (1-2% w/v, higher than that used in standard fluoride tubes used in blood glucose analysis). It increases lipid peroxidation.


Exposure issues

The 1994 WHO report stated that "the world optimum concentration would normally be in the range 0.5 – 1.0 mg/l" (in the water supply). The UK recommendation is 0.7-1.2mg/l for optimal prevention of dental caries. Only a few water companies in the UK add fluoride to the water.

In terms of a mild adverse effect (dental fluorosis in children), this leaves us with a relatively low therapeutic index, so it is reasonable to expect careful additive control, say to water supplies.


Natural water supplies can have excess fluoride. Also accidents have occurred. This allows fair confidence in these estimates for exposure to fluoride to be excessive:

  • ≥ 2mg/l drinking water child dental fluorosis
  • ≥ 8mg/l drinking water skeletal fluorosis
  • ≥ 50mg/l drinking water (for 12hours) gastroenteritis


  • 5-20 mg/m3 air (occupational) leads to crippling fluorosis


  • LD50 adults 2,500-10,000 mg of a fluoride salt (16 mg/kg in child)


Voriconazole an antifungal agent imposes in long term use a significant fluoride load that must be considered as it can cause fluorosis[4].

See also


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