Fluoride:


Source: Occurs naturally or as an additive to municipal water supplies; widely used in industry. Decreases incidence of tooth decay but high levels can stain or mottle teeth. Causes crippling bone disorder (calcification of the bones and joints) at very high levels.



State regulations require that fluoride, which occurs naturally in some water supplies, not exceed a concentration of 4.0 mg/L in drinking water. Exposure to drinking water levels above 4.0 mg/L for many years may result in some cases of crippling skeletal fluorosis, which is a serious bone disorder. State regulations also require a water system to notify the public when monitoring indicates that the fluoride in drinking water exceeds 2.0 mg/L This is intended to alert families about dental problems that might affect children under nine years of age.
Fluoride in children's drinking water at levels of approximately 1 mg/L reduces the number of dental cavities. However, some children exposed to levels of fluoride greater than about 2.0 mg/L may develop dental fluorosis. Dental fluorosis, in its moderate and severe forms, is a brown staining and/or pitting of the permanent teeth. Because dental fluorosis occurs only when developing teeth (before they erupt from the gums) are exposed to elevated fluoride levels, households without children are not expected to be affected by this level of fluoride. Families with children under the age of nine are encouraged to seek other sources of drinking water for their children to avoid the possibility of staining and pitting.
Your water supplier can lower the concentration of fluoride in your water so that you will still receive the benefits of cavity prevention while the possibility of stained and pitted teeth is minimized. Removal of fluoride may increase your water costs. Treatment systems are also commercially available for home use. Low fluoride bottled drinking water that would meet all standards is also commercially available.

References
http://www.dep.state.fl.us/water/drinkingwater/inorg_con.htm
http://water.usgs.gov/edu/groundwater-contaminants.html