FRIDAY, Jan. 7 (HealthDay News) -- U.S. government officials said Friday that the amount of fluoride in the nation's drinking water should now be set at the lowest recommended level.

Although fluoride is a significant help in preventing cavities and tooth decay, too much of it can cause unattractive spotting on children's teeth. About two out of five teens have white spots and streaks on their teeth due to too much fluoride, according to a recent government study.

To prevent this problem, the U.S. Department of Health and Human Services and the U.S. Environmental Protection Agency are recommending that the fluoride level in drinking water be set at 0.7 milligrams per liter of water, replacing the current recommended range of 0.7 to 1.2 milligrams.

"One of water fluoridation's biggest advantages is that it benefits all residents of a community -- at home, work, school, or play," HHS Assistant Secretary for Health Dr. Howard K. Koh said in a statement. "Today's announcement is part of our ongoing support of appropriate fluoridation for community water systems, and its effectiveness in preventing tooth decay throughout one's lifetime."

One reason for the new recommendation is that over the years the sources of fluoride have increased from water to include toothpastes, mouth wash, fluoride supplements and fluoride applied by dentists, EPA and HHS officials noted.

According to the agencies, this new recommendation allows the maximum prevention of tooth decay through fluoridation, while reducing the possibility of children getting too much fluoride.

Overexposure to fluoride results in a condition known as fluorosis, which can damage children's developing teeth.

In the United States fluorosis is usually mild, seen as barely visible lacy white markings or spots on the enamel. The severe form of fluorosis, which causes staining and pitting of the tooth surface, is rare here, but is more common in places like China where the water has naturally occurring levels of fluoride.

A spokesman for the American Dental Association, Dr. Matthew Messina, said these government agencies are doing their job in recommending what community water supplies are supposed to do.

"They have just refined from a range and provided a more exact direction," Messina said. "We are excited that they continue to advocate the safety and effectiveness of fluoride and its value as a public health measure in preventing dental decay."

Messina noted that fluoride occurs naturally in water and different places have different levels of fluoride. Some towns may not have to add any fluoride and others only a little to reach the recommended level, he said.

"Fluoride is one of the best returns on investment as far as the small amount of money spent on fluoridating water relative to the tremendous reduction in the cost of having cavities," Messina said.

Dr. Leo Dorado, an assistant professor of oral surgery at the University of Miami, said that each locality needs to tailor adding fluoride to water to achieve the right level.

Dorado is concerned that too much fluoride can cause fluorosis in young children. "I don't think the standard has been enforced state by state," he said. "It's not just an easy fix. It is something that has to be regulated according to government standards, but state by state," he said.

More information

For more information on fluoride, visit the American Dental Association.