This was just in the news in last few days.

U.S. Officials Recommend Reduced Fluoride Levels in Water
http://www.medicinenet.com/script/main/art.asp?articlekey=124477

SOURCES: Matthew Messina, D.D.S., spokesman, American Dental Association; Leo Dorado, D.D.S., assistant professor of oral surgery, University of Miami; U.S. Department of Health and Human Services, news release, Jan. 7, 2011