A mild case of fluorosis. (Creative Commons)

The federal agencies have lowered their recommended levels for fluoride in water--the first time they have done so in 50 years--while the EPA researches the issue further. The public has 30 days to comment on the new proposal before it can go into effect.

Children eight and younger who get too much fluoride end up with funny streaks and spots on their teeth. The CDC says this problem, known as fluorosis, is more common than it should be in children ages 12 through 15.

Fluoride, in safe levels, prevents tooth decay. The EPA has been mulling lowering the levels since 2006.

The Associated Press has more.