Fluctuations in public water fluoride level in Bauru, Brazil

Objectives: The aim of this study was to monitor the quality of public water supply fluoridation in Bauru, in the state of Sao Paulo, Brazil. Methods: Water samples collected three times a week during four weeks in 20 areas of distribution of water were supplied by the City Water Department of Bauru, Sao Paulo, Brazil. Fluoride was analyzed using the ion-specific electrode (Orion model 9409) after sample buffering with an equal volume of TISAB II. Data were compared to fluoride concentration reported by City Water Department. Results: Fluoride content ranged between 0.01 ppm and 9.35 ppm (n=240). There was great variation among the different areas of distribution of water, as showed by the Levene test (P <.001). Kruskal-Wallis test showed a statistically significant difference in mean fluoride concentration among different areas (P<.001). Mean fluoride concentration was less than the optimum concentration (0.8 ppm) in 89 percent of samples. The values reported by the City Water Department were always higher than the analyzed fluoride concentrations. Conclusions: Based on the results from this study, more rigorous surveillance and monitoring of water fluoridation in Bauru is recommended.