水道水フッ化物添加
Water fluoridation is the controlled addition of fluoride to a public water supply in order to reduce tooth decay. Its use in the U.S. began in the 1940s, following studies of children in a region where water is naturally fluoridated. In 1945, Grand Rapids, Michigan became the first city in the world to fluoridate its drinking water. The Grand Rapids water fluoridation study was originally sponsored by the U.S. Surgeon General, but was taken over by the NIDR shortly after the institute's inception in 1948. It is now used for about two-thirds of the U.S. population on public water systems and for about 5.7% of people worldwide. Although the best available evidence shows no association with adverse effects other than fluorosis, most of which is mild, water fluoridation has been contentious and opposition to water fluoridation exists despite its support by public health organizations. Water fluoridation is the most cost-effective way to induce fluoride, with an estimated cost between US$0.50 and $3.00 per person per year, depending on the size of the community involved. A dollar spent on fluoridating water is estimated to save $7–$42 on dental treatment.