Can fluoride be too much of a good thing?
The government is lowering the recommended amount of fluoride in drinking water because some kids are getting too much, causing white splotches on their teeth.
It's the first change since the government urged cities to add fluoride to water supplies to prevent tooth decay more than 50 years ago. Now, fluoride is put in toothpaste, mouthwash and other products as well.
One study found about 2 out of 5 adolescents had tooth streaking or spottiness. It's primarily a cosmetic issue, said Deputy Surgeon General Boris Lushniak.
The mineral fluoride is in water and soil. About 70 years ago, scientists discovered that people whose drinking water naturally had more fluoride also had fewer cavities.
Grand Rapids, Michigan became the world's first city to add fluoride to its drinking water in 1945. Six years later, a study found a dramatic decline in tooth decay among children there and the U.S. surgeon general endorsed water fluoridation.
Today, about 75 percent of Americans get fluoridated water.
But adding fluoride was and has remained controversial as opponents argue its health effects aren't completely understood and that adding it amounts to an unwanted medication.
Among the more recent dust-ups: Portland, Oregon voters rejected a proposal to add fluoride two years ago. This year, Sheridan, Wyoming resumed adding fluoride; the city stopped in 1953 after a referendum.
Water fluoridation has been a public health success and communities should keep adding fluoride, said Kathleen O'Loughlin, the American Dental Association's executive.
Lushniak added: "It is the best method for delivering fluoride to all members of the community."
Since 1962, the government has recommended a range of 0.7 milligrams per liter for warmer climates where people drink more water, to 1.2 milligrams in cooler areas. The new standard is 0.7 everywhere.
Recent unpublished federal research found there's no regional differences in the amount of water kids drink, so it makes sense for the same levels to be used everywhere, health officials said.
To limit fluoride for young children, the Centers for Disease Control and Prevention offers this advice: Don't use fluoride toothpaste for children under 2 unless recommended by a dentist; use only a pea-sized amount of toothpaste for children 2 through 6 and avoid fluoride mouthwash.
Critical thinking challenge: Why is fluoride added to water instead of some other food or beverage?