This study aimed to monitor the fluoride concentration in the public water supply in Teresina, Floriano, and Parnaíba, Piauí State, Brazil. Samples were collected monthly for one year between 2004 and 2005. Six sites in each city were randomly selected for water sampling (total n = 576), 192 in each city. Fluoride assays were performed in duplicate, using a specific electrode. Most samples were below the optimum fluoride concentration, and only 4.3% (n = 25) presented acceptable values (0.60-0.80ppm). Acceptable samples totaled 7.8% (n = 15), 4.7% (n = 9), and 0.5% (n = 1) in Teresina, Floriano, and Parnaíba, respectively. By conclusion, fluoride levels in the public water supply in the three cities were below the optimum concentration, and a permanent surveillance system is thus needed to guarantee effective water fluoridation in the State of Piauí.
Fluorine; Fluoridation; Water Supply; Surveillance