External control over fluoridation of the public water supply in São Luís, MA, Brazil

ABSTRACT

Objective:To tomonitor fluoride concentrations in the public water supply of São Luís, Maranhão, Brazil, from February 2008 to January 2009. Material and Method:Forty sampling points representing 39 neighborhoods of São Luís were conveniently selected. The points were selected based on the sites where the public water supply is provided by the local water supply company and also considering the proximity of elevated water reservoir tanks. The analysis of the fluoride concentration was performed in triplicate using an ion-specific electrode for fluoride connected to a previously calibrated potentiometer. After analysis, the samples were considered adequate when the fluoride concentration was within recommended limits from 0.60 up to 0.80 ppm F (criterion I) or within the stipulated range from 0.55 ppm up to 0.84 ppm F (criterion II). Results:The results showed a large variation between minimum and maximum concentrations. Considering all samples, the average values (± SD) for the municipality was 0.58 ppm F (± 0.24) and median value was 0.61 ppm F, with minimum and maximum value of 0.02 and 1.33 ppm F, respectively. Of the 480 samples, 62.9% was considered inadequate by criterion I, while using criterion II, the percentage was 48.3%. Conclusion:The fluoridation program in São Luís-MA needs improvement. Therefore, surveillance based on external control and operational control becomes essential to ensure that the method is efficient and effective