High fluoride contents in the water supply of the city of Ponta Delgada, located in the volcanic island of São
Miguel (Azores, Portugal) have been reported. Dental fluorosis in São Miguel has been identified and described
in several medical surveys. The water supply in Ponta Delgada consists entirely of groundwater. A
study was carried out in order to characterize the natural F-pollution of a group of springs (30) and wells
(3), that are associated to active central volcanoes of a trachytic nature. Two springs known for their high
content in fluoride were sampled, both located in the central volcano of Furnas