The US government on Friday recommended that the level of fluoride in the public drinking supply be lowered to avoid dental problems due to overexposure.
Once ranked among the greatest public health achievements of the last century, fluoridation of water is less needed now because many Americans get plenty from toothpaste and mouthwash, said the Department of Health and Human Services and the Environmental Protection Agency in a joint statement.
"Today both HHS and EPA are making announcements on fluoride based on the most up to date scientific data," said EPA Assistant Administrator for the Office of Water Peter Silva.
"EPA's new analysis will help us make sure that people benefit from tooth decay prevention while at the same time avoiding the unwanted health effects from too much fluoride."
The agencies noted that adding fluoride to water and toothpaste has resulted in a "significant decline in tooth decay in the US over the past several decades."
However, "Americans have access to more sources of fluoride than they did when water fluoridation was first introduced in the United States in the 1940s."
The new recommendations will call for adding just 0.7 milligrams of fluoride per liter of water to water supplies, the lower end of the current range of 0.7 to 1.2 milligrams per liter.