Fluoride
F⁻·Affects bones, brain
Added to most US municipal water for dental-health benefits, and naturally present in many well-water sources. Whole-house carbon reduces fluoride only partially; reverse osmosis removes it fully.
F⁻
EPA limit
4.0 mg/L (MCL); 2.0 mg/L (secondary); CDC recommends 0.7 mg/L for fluoridation
Most at risk
Well-water households in high-fluoride geology, infants on formula
Found in
City water · Well water
AquaOx filters
Pair with ROPair with under-sink RO
What it does to you
Health effects
Fluoride at the level recommended by the CDC for community fluoridation (0.7 mg/L) is supported by decades of dental research showing reduced tooth decay across populations. The American Dental Association, the WHO, and the CDC all maintain that fluoridation at this concentration is safe and effective.
The EPA's enforceable limit of 4.0 mg/L exists because at higher concentrations fluoride causes skeletal fluorosis: a condition where fluoride accumulates in bone and causes pain, stiffness, and increased fracture risk. The secondary limit of 2.0 mg/L addresses dental fluorosis, a cosmetic mottling of tooth enamel that can occur in children exposed to elevated levels during tooth development.
Some recent research has examined possible links between high prenatal fluoride exposure and neurodevelopmental outcomes. The evidence is debated and ongoing. People who prefer to minimize fluoride intake for personal reasons can effectively remove it from drinking water with reverse osmosis at the kitchen tap.
Where it comes from
How it gets into your water
Roughly 73% of US community water systems add fluoride intentionally as part of public-health fluoridation programs. The dose is controlled to approximately 0.7 mg/L. Utilities use one of three compounds: hydrofluorosilicic acid, sodium fluorosilicate, or sodium fluoride.
Fluoride also occurs naturally in groundwater where it dissolves out of fluoride-bearing rocks like fluorite, fluorapatite, and certain granites. Parts of the US Southwest, including portions of Arizona, New Mexico, Texas, and Colorado, have natural well-water fluoride above the EPA limit. The CDC maintains maps of high-fluoride geology.
Municipal fluoridation
Intentional addition at ~0.7 mg/L
Natural geology
Dissolves from fluoride-bearing rock
Industrial discharge
Aluminum + fertilizer manufacturing
Some bottled waters
Spring waters from high-F aquifers
Find out for yourself
Is it in your water?
If your home is on a municipal supply, your utility's Consumer Confidence Report lists the fluoride concentration and whether the system is fluoridated. You can also check the CDC's "My Water's Fluoride" tool for community-level data.
Well-water households should request a fluoride test, particularly if the well is in known high-fluoride geology. Natural fluoride in wells does not show up on a standard taste or smell test: it requires lab analysis.
The fix
How AquaOx filters it
The AquaOx whole-house filter reduces fluoride — up to about 40% in independent lab testing — but it is not designed to take it all the way down. Activated carbon excels at chlorine, disinfection byproducts, VOCs, and most industrial chemicals; fluoride it only partially reduces, because the fluoride ion is small and highly charged.
For fully fluoride-free water at the drinking tap, pair The AquaOx with our [under-sink RO Kitchen Sink](https://www.aquaoxwaterfilters.com/) system. Reverse osmosis membranes reject 85 to 95% of fluoride. This is the standard, effective home-treatment approach. If well-water fluoride exceeds the EPA limit, RO at the point of use is the right answer for drinking and cooking water, and ion-exchange systems are an alternative whole-house option for severe cases.
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