Frequent Questions

Are there public water systems that exceed the drinking water standard for fluoride? Why? What do they do about it?

A very small proportion of the public water systems nationwide have exceeded the drinking water standard for fluoride.  In these cases, the high level of fluoride is generally the result of natural background resulting from the geologic composition of local soils and bedrock.  When routine monitoring indicates that fluoride levels are above the MCL of 4 mg/L, the public water system must take steps to reduce the amount of fluoride so that it is below that level.
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