Fluoride in groundwater in Fnland
Fluoride and health
Fluoride is an important trace element for teeth and bones. A lack of fluoride will cause a loss of immunity to dental caries and make bones brittle. Too much fluoride however will damage teeth enamel. According to the European Union regulations for drinking water, the maximum fluoride content in potable water is 1.5 mg F-/litre, which is the same as that given by the World Health Organization (WHO). The optimal fluoride content for teeth is 0.8-1.2 mg F-/litre.
Occurrence of Fluoride
Fluoride is found naturally in the rapakivi granites that form the bedrock over large areas of southeast and southwest Finland and in the Åland archipelago. The rapakivi granites are characterised by high fluoride concentrations, which are much higher than in other bedrock types, and which are reflected in the chemistry of the groundwater in the areas where these granites are found. The fluoride concentrations in these areas can be 1.5- 2.5 mg F-/litre, and sometimes even 3.5-4.5 mg F-/litre.
Removal of fluoride
In small waterworks fluoride can be removed from potable water by reverse osmosis and in large water works it is done by using activated alumna. In some individual cases separation by precipitation with alumna can be considered a possible method.
Reference (in Finnish)
Liponkoski Markku, 1999. Fluori ja sen poistaminen talousvedestä. Suomen ympäristö 320, luonto ja luonnonvarat, 52 s. ISBN 952-11-0511-9. English abstract: Fluoride and its removal from potable water.