© 2025 American Dental Association l 43
Fluoridation Facts
be taken at that time to change the current MCL/MCLG of 4 mg/L (the maximum level of naturally
occurring fluoride allowed in drinking water).201
The EPA decided in July 2024 that the fluoride National Primary Drinking Water Regulations are
not a candidate for revision.202 In addition, the NTP has not made a final decision about the report’s
developmental neurotoxicity systematic review conclusions and has not formally released a final
report. Following publication of the final NTP report, the EPA will consider the systematic review and
meta-analysis conclusions regarding developmental neurotoxicity to inform the agency’s future
development of a health effects assessment for fluoride. The EPA has not as yet changed this
decision (as of January 25, 2025).
21. What is the Secondary Maximum Contaminant Level (SMCL) for
naturally occurring fluoride in drinking water established by
the EPA?
Answer
The SMCL for naturally occurring fluoride in water is 2 mg/L (or ppm). This is a non-enforceable
federal standard.
Fact
In addition to the MCL, the EPA has established an SMCL of 2.0 mg/L and requires consumer notification
by the water supplier if the naturally occurring fluoride level exceeds 2.0 mg/L. The SMCL, while not
federally enforceable, is intended to alert families that regular consumption of water with natural levels
of fluoride greater than 2.0 mg/L by young children could cause moderate to severe dental fluorosis
in the developing permanent teeth.204 The notice to be used by water systems that exceed the SMCL
must contain the following points:
• The notice is intended to alert families that children under 9 years of age who are exposed to
levels of fluoride greater than 2.0 mg/L may develop dental fluorosis.
• Adults are not affected because dental fluorosis occurs only when developing teeth are exposed
to elevated fluoride levels.
• The water supplier can be contacted for information on alternative water sources or treatments
that will ensure the drinking water would meet all standards (including the SMCL).204
Fluoridation Facts
be taken at that time to change the current MCL/MCLG of 4 mg/L (the maximum level of naturally
occurring fluoride allowed in drinking water).201
The EPA decided in July 2024 that the fluoride National Primary Drinking Water Regulations are
not a candidate for revision.202 In addition, the NTP has not made a final decision about the report’s
developmental neurotoxicity systematic review conclusions and has not formally released a final
report. Following publication of the final NTP report, the EPA will consider the systematic review and
meta-analysis conclusions regarding developmental neurotoxicity to inform the agency’s future
development of a health effects assessment for fluoride. The EPA has not as yet changed this
decision (as of January 25, 2025).
21. What is the Secondary Maximum Contaminant Level (SMCL) for
naturally occurring fluoride in drinking water established by
the EPA?
Answer
The SMCL for naturally occurring fluoride in water is 2 mg/L (or ppm). This is a non-enforceable
federal standard.
Fact
In addition to the MCL, the EPA has established an SMCL of 2.0 mg/L and requires consumer notification
by the water supplier if the naturally occurring fluoride level exceeds 2.0 mg/L. The SMCL, while not
federally enforceable, is intended to alert families that regular consumption of water with natural levels
of fluoride greater than 2.0 mg/L by young children could cause moderate to severe dental fluorosis
in the developing permanent teeth.204 The notice to be used by water systems that exceed the SMCL
must contain the following points:
• The notice is intended to alert families that children under 9 years of age who are exposed to
levels of fluoride greater than 2.0 mg/L may develop dental fluorosis.
• Adults are not affected because dental fluorosis occurs only when developing teeth are exposed
to elevated fluoride levels.
• The water supplier can be contacted for information on alternative water sources or treatments
that will ensure the drinking water would meet all standards (including the SMCL).204
