Fluoride (F) can be removed from drinking water by reverse osmosis and distillation systems. However, there is no consensus about the effectiveness of activated carbon filters.
Objectives: (1) To evaluate the extent to which domestic, activated carbon water filters remove F from water and (2) to evaluate quality control of water fluoridation in Bauru, state of São Paulo, Brazil.
Methods: Samples of filtered and nonfiltered tap water were collected from 180 houses in 9 different regions in the city, each served with its own water treatment facility. Fluoride was analyzed with the electrode (Orion 96-09), previously calibrated with standards containing 0.025-1.600 ppm F, after buffering with TISAB II.
Results: Nonfiltered and filtered water F concentrations (mean±SD, unit ppm, n=20) for areas 1 to 9 were: 1) 1.05±0.17 and 1.11±0.22; 2) 0.70±0.14 and 0.59±0.22; 3) 0.60±0.09 and 0.60±0.16; 4) 0.66±0.12 and 0.65±0.11; 5) 0.06±0.02 and 0.06±0.04; 6) 1.12 ±0.13 and 1.08±0.07; 7) 0.86±0.01 and 0.87±0.10; 8) 0.61±0.02 and 0.61±0.06; 9) 0.32±0.06 and 0.31±0.01. Of the 180 filters tested, only 15 removed F from water, either totally (3) or partially (12). Water F concentrations in five regions (2, 3, 4, 7 and 8) were within the optimal range (0.6-0.8 ppm). Over-fluoridation was observed in 2 areas (1 and 6), and under-fluoridation in 2 areas (5 and 9).
Conclusions: Most domestic activated carbon filters did not remove F concentrations in water. Further investigations should be conducted to determine why some filters remove F from water and others do not. As has been shown in other studies, the quality control of water fluoridation in some regions of Bauru is not adequate.