USA - Too much

The standard of 4 milligrams a liter is the maximum that the EPA allows. Some people who drink water with fluoride in excess of this level over many years could get bone disease, including pain and tenderness of the bones, the EPA says. The agency also set a secondary standard of 2 to protect against brown staining or pitting of teeth. It happens only in developing teeth, so the EPA warns that children younger than 9 should not drink water with more than 2 milligrams of fluoride per liter. A study due out this year examines a link between fluoride and bone cancer. EPA officials say they're waiting on that report before they decide whether standards should change. Isle of Wight resident Sandy Schlaudecker thinks that the county needs to do more to educate residents about fluoride. "I see so many kids in this county with horrible-looking teeth," Schlaudecker said. "My concern is for the children, and the parents don't understand how bad the water is," she said.
"These kids are going to have ugly teeth for the rest of their lives." Schlaudecker, who lives in Gatling Pointe South, received a high-fluoride notice from the county, but she couldn't understand it. The county plans to rewrite the notices, Rountree said.

I wonder if they use fluoride mouth washes and toothpaste as well?