Fluctuation of fluoride concentrations in drinking waters: a collaborative study

The aim of this study was to describe the variations with time in the concentrations of fluoride in drinking water sources in Greenland, Kenya, Greece, Denmark and Ireland. Water samples were collected monthly and shipped to laboratories in Aarhus for electrometric analyses. In Narssaq, Greenland the fluoride concentration of a single piped water supply ranged from 0.3 to 2.8 ppm, the variations being related to climate, precipitation and temperature over the year. Water from the Athi River, Kenya had a fluoride content ranging from 0.3 to 1.2 ppm, the higher concentrations being associated with the dry seasons. The fluoride concentration in piped water from mountain rivers in Mourjes, Greece, ranged over the year between 1.3 to 2.0 ppm, the changes being apparently unrelated to rainfall. Marked variations in fluoride concentrations from 0.5 to over 3.5 ppm were observed in water from artesian wells in Assiros, Greece. In drinking waters from boreholes in Boennerup Strand, Denmark, fluoride concentrations ranged with time from 1.4 to 2.4 ppm, the variations being unrelated to climate or precipitation, while little variation in fluoride concentrations was found in water from boreholes in either Roedvig or Egens, Denmark. Water obtained from two sources of artificially fluoridated water supplies from Ireland showed considerable variations with time, although pooled samples indicated relatively constant levels over the year. The study indicates that the results of single fluoride ion measurement from any given source should not be taken as being a reliable indicator of fluoride exposure from drinking water.(ABSTRACT TRUNCATED AT 250 WORDS)