The 2006 NRC Report was commissioned by the EPA. It is required to reconsider maximum fluoridation levels every ten years.
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The 2006 NRC Report was not commissioned to address the question of water fluoridation, and the authors were told not to address it. Its purpose was to examine the 4 ppm maximum contaminant level (MCL) and the 2 ppm maximum contaminant level goal (MCLG) to determine if they provided an adequate measure of protection.
The 4 ppm MCL is the maximum amount of fluoride which may legally be allowed in drinking water, and if fluoride is present at higher than 4 ppm, the water district is to remove the excess. The 4 ppm MCL is not an authorization to add fluoridation up to the 4 ppm limit. The EPA is forbidden in the Safe Drinking Water Act from reqiring the addition to drinking water of any form of medication.