ABSTRACT
Abstract Objective: To analyze the fluoride concentration in the public water supply in Manaus, Brazil. Material and Methods: Water samples were collected in 50 mL polyethylene bottles, identified, and labeled. The collection was performed from September 2016 to August 2018. For the selection of collection points, all neighborhoods of the city of Manaus, divided into four health districts (North, South, East, and West), were mapped. From each district, 30 samples were collected, totaling 120 monthly samples. Water samples were analyzed using an ion analyzer, ORION 720-A, and a specific electrode, ORION 96-09. The ion analyzer and electrode were calibrated in standard solutions. The levels were classified in intervals based on technical consensus to guide the health surveillance agencies. Results: Of the 2,874 water samples, 50.3% were within the recommended range, and 49.7% were inadequate, with 31.6% considered above the parameters and 18.1% below. Among the districts, the North had the highest percentages of unsatisfactory samples, resulting in limited action to prevent tooth decay. During the 24 months of analysis, there were large oscillations in the values in all four districts of Manaus. Conclusion: Results reinforce the importance of heterocontrol for the city to guarantee the effectiveness of this public health measure.