There have been a lot of buzz around the use of Fluoride as an additive to city water or dental care products and the harm it could cause should it be ingested excessively and he final verdict has it that there is not much risk from too much fluoride. The worst thing that could happen would be whitish bands that form on the teeth as they form which is more of a cosmetic issue that a health risk.
Flourosis as it is called is a health issue associated with the ingestion of large amounts of fluoride but as it is, no severe cases have been found so far and only mild cases that tend to rectify themselves as kids grow are most prevalent.