The federal government has lowered the recommended level of fluoride in drinking water for the first time in five decades.

The Department of Health and Human Services is now advising water supply managers to reduce levels of the mineral to 0.7 milligrams per liter (mg/l). The previous recommendation, developed in 1962, advised communities to permit fluoride concentrations between 0.7 and 1.2 mg/l.

The reduction in recommended fluoride levels was driven in part because Americans now have access to fluoride in various forms, including toothpaste and mouthwashes, which were not in widespread use half a century ago. Because of this, more people are exposed to too much fluoride and can experience fluorosis, white stains in the enamel of their teeth, from too much fluoride. Mild fluorosis appears as scattered white flecks, frosty edges or chalk-like lines on teeth, while the white spots get larger with severe fluorosis.

"Fluoride is voluntarily added to some drinking water systems as a public health measure for reducing the incidence of cavities among the treated population. The decision to fluoridate a water supply ... is not mandated by EPA or any other federal entity,"  the United States Environmental Protection Agency wrote.

Fluoride often enters public water systems naturally, but concentrations are usually far too low to help prevent tooth decay. Communities have also been adding fluoride to drinking water for 70 years, in an effort to reduce the incidence of tooth decay among residents. Today, nearly three-quarters of all Americans are served by fluoridated water in their homes. The new lower recommended level will maintain fluoride protection but reduce incidents of fluorosis.

Although federal officials state the use of fluoride is safe and effective, the practice has generated controversy since it was first adopted. Some critics claim it isn't possible to determine dosages, or that the mineral causes negative health effects. Others say fluoridation of drinking water is not a cost-effective way of reducing tooth decay.

From the late 1940s through the 1960s, these concerns developed into claims of a communistic (or socialist) plot. Some of these political opponents of fluoridation tied this practice to a drive toward socialized medicine, mental health programs and public vaccination programs. Still other critics said fluoridation of water would reduce the intelligence of American children, preparing the nation for a takeover by the Soviet military.

"While additional sources of fluoride are more widely used than they were in 1962, the need for community water fluoridation still continues. Community water fluoridation continues to reduce tooth decay in children and adults beyond that provided by using only toothpaste and other fluoride-containing products," said Boris D. Lushniak, U.S. Deputy Surgeon General Rear Admiral.

Medical researchers first noted during the 1930s that people living in areas with higher natural fluoride concentrations in their water experienced less tooth decay. The mineral, which can be stored in saliva and dental plaque, was first added to the public water system in Grand Rapids, Mich., in 1945.

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