Sampling and initial findings for a study of fluoride in drinking water in the United States

The role of fluoride in reducing the risk of dental caries, especially among children, is well recognized and is the basis for current intake recommendations. The US Department of Agriculture, Nutrient Data Laboratory conducted a comprehensive study of the fluoride content of US drinking water, as part of the US National Fluoride Database and Intake Assessment Study, a collaborative effort with the University of Minnesota, the University of Iowa College of Dentistry, and Virginia Polytechnic Institute and State University. The sampling method involved: serpentine ordering of the US population by census region, division, and county; dividing the population into 72 equal population size zones; and randomly selecting one county per zone and two residences per county. Participants were recruited by phone to provide two tap water samples, 3–4 months apart; samples (n=288n=288) were analyzed by the direct read method. Well water averaged <20 mcg fluoride/100 g, municipal water averaged 100–110 mcg fluoride/100 g, and the national average across sources was 71 mcg fluoride/100 g. These nationally representative data for drinking water will support public health research on the impact of fluoride on bones and teeth and will provide a foundation for assessment tools in the dental and medical communities.