Fluoride occurs naturally in ground waters through out the world, and in trace amounts is found in many foods. In many countries, including the U.S., flouride is purposely introduced into the drinking water supply in concentrations of approximately 1.0 ppm (milligrams/liter) for the purpose of reducing dental caries.
Many communities add fluoride to their drinking water to promote dental health. Each community makes its own decision about whether or not to add fluoride. EPA has set an enforceable drinking water standard for fluoride of 4 mg/L (some people who drink water containing fluoride in excess of this level over many years could get bone disease, including pain and tenderness of the bones). EPA has also set a secondary fluoride standard of 2 mg/L to protect against dental fluorosis. Dental fluorosis, in its moderate or severe forms, may result in a brown staining and/or pitting of the permanent teeth. This problem occurs only in developing teeth, before they erupt from the gums. Children under nine should not drink water that has more than 2 mg/L of fluoride.