EPA legal limit
4 ppm
Maximum Contaminant Level
EWG health guideline
No guideline
Science-based, stricter target
Health effects
At the levels added for dental health (0.7 ppm), fluoride is considered safe by major health agencies including CDC, WHO, and ADA. At levels above 2 ppm, dental fluorosis (mottling of tooth enamel) can occur in children. At levels above 4 ppm (the MCL), skeletal fluorosis can develop. The safety of water fluoridation at 0.7 ppm has been debated, with a 2024 NTP systematic review finding a "moderate confidence" association between high fluoride exposure and lower IQ in children — though this primarily applied to regions with naturally high fluoride levels, not U.S. fluoridation levels.
Where it comes from
Two sources: intentional addition by utilities for dental health (0.7 ppm), and natural occurrence in groundwater from fluoride-bearing minerals. Naturally occurring fluoride can exceed the MCL in some parts of the country.
How it's regulated
EPA sets an enforceable MCL of 4 ppm and a non-enforceable secondary standard (aesthetic goal) of 2 ppm. HHS recommends 0.7 ppm for water fluoridation.
How to filter fluoride
Not all filters address fluoride. Look for independently certified filters — NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is fluoride?
Fluoride is added to most U.S. community water systems at 0.7 ppm (since 2015) to reduce tooth decay. It also occurs naturally in some groundwater supplies at higher concentrations. At very high levels, it causes adverse health effects.
What are the health effects of fluoride?
At the levels added for dental health (0.7 ppm), fluoride is considered safe by major health agencies including CDC, WHO, and ADA. At levels above 2 ppm, dental fluorosis (mottling of tooth enamel) can occur in children. At levels above 4 ppm (the MCL), skeletal fluorosis can develop. The safety of water fluoridation at 0.7 ppm has been debated, with a 2024 NTP systematic review finding a "moderate confidence" association between high fluoride exposure and lower IQ in children — though this primarily applied to regions with naturally high fluoride levels, not U.S. fluoridation levels.
Is fluoride regulated in drinking water?
EPA sets an enforceable MCL of 4 ppm and a non-enforceable secondary standard (aesthetic goal) of 2 ppm. HHS recommends 0.7 ppm for water fluoridation.
Where does fluoride come from?
Two sources: intentional addition by utilities for dental health (0.7 ppm), and natural occurrence in groundwater from fluoride-bearing minerals. Naturally occurring fluoride can exceed the MCL in some parts of the country.
How do I remove fluoride from tap water?
The most effective methods for removing fluoride are: Reverse osmosis (RO), NSF 58 certified RO system, Distillation. Look for NSF-certified systems — independent certification confirms removal claims have been verified.
Is fluoride in your water?
Enter your ZIP code to see the measured level in your specific utility.