Cavity-preventing water-fluoride chemicals consumed by most Americans are neither FDA approved (1) nor tested for health effects, according to the Environmental Protection Agency (EPA)(2).
Although used by over 91 percent of US fluoridating communities, silicofluorides, were nominated for study, for the first time, in October 2001, by the National Toxicology Program (3) Currently, silicofluorides are used in over 9200 U.S. water treatment systems, serving over 120 million individuals. Most Americans also consume products made in silicofluoridated communities.
The EPA was "unable to find any information on the effects of silicofluorides on health and behavior," according to a November 16, 2000 EPA letter to Roger D. Masters, Research Professor of Government, Dartmouth College, (2)
Unlike most chemical additives necessary for safer and palatable drinking water, added fluoride treats people for a disease they may never have - tooth decay. Maybe due to Dr. Masters prodding, the EPA intends to test the silicofluorides, some 50 years after they were first introduced into U.S water supplies.
According to a March 15, 2001, letter from the EPA, "Several fluoride chemistry related research needs were identified including: (1) accurate and precise values for the stability constants of mixed fluorohydroxo complexes with aluminum (III), iron (III) and other metal cations likely to be found under drinking water conditions and (2) a kinetic model for the dissociation and hydroloysis of fluosilicates and stepwise equilibrium constants for the partial hydrolysis products."
A layperson may find this unintelligible but it shows the basic level of science that wasn't undertaken by government officials before introducing silicofluorides into the US environment and population.
Recent research by Masters and Coplan show that children who drink silicofluoridated water have higher blood lead levels than children who live in sodium fluoridated or non-fluoridated communities(4).
According to Masters "... animal studies in the 1930s showed substantial differences in metabolism between sodium silicofluoride and sodium fluoride ... Other research also suggests differences in fluoride metabolism from these chemicals...Of particular importance is a German study revealing that silicofluorides have biological effects which could increase vulnerability to environmental toxins and modify behavior (Westendorf 1975).
The National Toxicology Program recommended in an October 2001 report that silicofluorides finally be studied for health effects reporting: "Sodium hexafluorosilicate and fluorosilicic acid (silicofluorides) were nominated for toxicological testing based on their widespread use in water fluoridation and concerns that if they are not completely dissociated to silica and fluoride in water that persons drinking fluoridated water may be exposed to compounds that have not been thoroughly tested for toxicity,"
National Institutes of Dental and Craniofacial Research (NIDCR) grants, up to $250,000 annually, are offered to scientists to learn how to discern when fluoride's benefits turn into risks, the overall metabolism of fluoride, and how it affects bones and teeth - something we hoped was known before adding fluorides to virtually every Americans food and water supply since 1945.(6).
(1) http://www.fluoridealert.org/f-supplements.htm 
2) http://www.dartmouth.edu/~rmasters/letter.jpg 
3a) http://ntp-server.niehs.nih.gov/htdocs/Chem_Background/ExSumPDF/Fluorosi... 
b) http://ntp-server.niehs.nih.gov/htdocs/liason/ICCECFinal02JuneFR.html 
4) "Association of Silicofluoride Treated Water with Elevated Blood Lead," NeuroToxicology, December 2000, Masters, Coplan, Hone, Dykes
5 ) Annual Review of Political Science: http://www.dartmouth.edu/~rmasters/bp.htm 
6) http://www.suite101.com/article.cfm/11749/81104