Fluoride content of municipal water in the United States: what percentage is fluoridated?

Recently, a study was conducted to look at the trace element content of municipal waters sampled around the United States. This was a collaborative project defined by representatives of the Nutrient Data Laboratory and the Food Composition Laboratory of the United States Department of Agriculture. As part of the study, the fluoride content of nationally representative water samples was measured since water is one of the principal sources of fluoride in the US diet. This study served as a pilot for planning a more extensive future nationwide sampling. Samples were analyzed using a separate reference electrode and ion selective electrode with TISAB II buffer. The calibration range was from 0.5 to 3.0 ppm. Accuracy of the method was validated by analyzing NIST SRM 2671a Fluoride in Freeze-Dried Urine. Results from the municipal water study clearly showed that the distribution of fluoride in US municipal waters is bi-modal. That is to say, because of the fact that ambient levels are typically extremely low, the concentration of fluoride is basically quantized. Either the water is fluoridated and contains approximately 1 ppm of fluoride or it is not fluoridated with undetectable fluoride concentration. The distribution of these data make it difficult to assign a meaningful average value useful to health professionals and consumers to assess fluoride intake. This study revealed that approximately 40% of the water samples from this nationwide sampling were fluoridated with a mean concentration of 1.01±0.15 μg/ml.