External control of fluoridation in public water supply of Canoas/RS

Abstract

The aim of this study was to evaluate the concentration of fluoride in public water supplies in Canoas/RS. Samples of drinking water were collected in duplicates for eight months on 22 different points grouped into three water treatment plants of the city. The measurement of fluoride concentration was performed using the electrometric method. The analysis of samples collected in the study period showed that there was oscillation in fluoride concentrations in accordance with the sampling months (from 0.185 to 1.605 ppm /L). Of the samples, 96 (54.5%) were inadequate (<0.6 ppm> 0.9 ppm) as the fluoride concentration. Of inadequate samples, the majority showed concentrations above the maximum acceptable concentration for drinking water standard. There was statistically significant difference among the three water treatment plants regarding the suitability of the fluoride concentration (p <0.001). The large variation in relation to fluoride concentration as well as the high percentage of inadequate samples revealed the need to implement measures of external control to ensure continuous effectiveness of water fluoridation.