I have been doing a little research on the safety of flouride and came across the article that I will paste a link to below. Certainly there are benefits — strong teeth and cavity protection — but studies show that too much flouride can be very damaging causing issues from teeth discoloration to endocrine disruption to weakened bones. Children are at the greatest risk since their bodies are much smaller and they need less.
Though there does not seem to be an agreed upon standard, it seems that 1 part per million is about the recommeded daily level (and this varies around the world). This is the amount used by the local water works system in my city. But research shows there may be no benefit in drinking flourinated water. And flouride is found in food, beverages and of course toothpaste, so is there really a need to add it to our public water systems? I personally am thinking no. I am a huge water consumer, I rarely drink anything else, so I am not of fan of having it added to the water. Now, I do think flouride has a place, but after reading a few studies, it certainly appears we are consuming too much and that is leading to potentionally serious issues.
Here is the news release: http://www.reuters.com/article/pressRelease/idUS108377+02-Jan-2008+PRN20080102