Fluoride occurs naturally in varying amounts in Connecticut groundwater usually at less than 2 mg/L. If there are children under the age of nine living in the house, arrange to test your drinking water for fluoride content and consult your dentist or physician concerning the results. If elevated fluoride levels are present, home treatment options include reverse osmosis, distillation, and ion exchange. Bottled water can be used as an alternate source for drinking and cooking, but check the nutritional label for fluoride content or arrange to test the bottled water for fluoride content.
The Maximum Contaminant Level (MCL) for fluoride in drinking water is 4.0 milligrams per liter (mg/L) as established by the United States Environmental Protection Agency (EPA). In addition, EPA has set a Secondary Maximum Contaminant Level (SMCL) of 2.0 milligrams per liter as a guideline in areas that have high levels of naturally occurring fluoride. In 2006 a National Academy of Sciences report found that the MCL of 4.0 mg/L is too high to adequately protect public health and young children from the adverse effects of fluoride (NAS, 2006). For those public drinking water systems that add fluoride to drinking water, the optimum concentration is 0.7 milligram per liter (mg/L). This concentration is thought to be protective of public health while limiting the potential for dental fluorosis (U.S. DHHS 2015).
Potential Health Effects
When teeth are growing (from birth to about age 8), optimal levels of fluoride (0.7 mg/L) can make teeth stronger and more resistant to lifelong tooth decay (CDC MMWR 2023). However, consuming too much fluoride (>2.0 mg/L) while teeth are growing can affect the appearance of teeth, causing white lines or spots in the outer enamel layer (dental fluorosis), an aesthetic problem without health effects. Long-term consumption of very high amounts of fluoride (10 to 15 milligrams per day for 20 years) can cause skeletal fluorosis. The possibility that early life exposure to excess fluoride may impact children’s IQ continues to be highly debated (EPA 2025). However, expert scientific panels have not found convincing scientific evidence that water fluoride levels below 1.5 mg/L impact children’s IQ (Taylor 2025; NTP 2024; CADTH 2019).
Indications of Fluoride
Fluoride does not alter the taste, color, or smell of water. A water test is the only way to determine the presence of fluoride in drinking water.
Source of Fluoride in Drinking Water
Fluoride is a naturally occurring element found in food and drinking water sources. Bedrock wells are at greater risk for high levels of fluoride. Fluoride may also be discharged as by-products from fertilizer and aluminum factories and from there it can enter groundwater.
Interpreting Test Results
For fluoride levels in drinking above 0.85 mg/L
This amount of fluoride is higher than the optimal range and may confer some health risk in some individuals. Consult your dentist or physician if there are children under the age of nine in the home and these levels are present in your drinking water. Fluoride levels exceeding the secondary MCL of 2.0 mg/L may contribute to dental fluorosis. Results above the MCL of 4.0 mg/L require corrective action, which includes either defluoridation or replacing the source of water with a source that is below the fluoride Maximum Contaminant Level of 4.0 mg/L.
For fluoride levels in drinking water between 0.55 mg/L and 0.85 mg/L
This is the optimal range for promoting dental health in children. Children consuming this level of fluoride in their drinking water do not need any fluoride supplements.
For fluoride levels in drinking water less than 0.55 mg/L
This level of fluoride is not sufficient for promoting optimum dental health in children. Consult your dentist or physician for fluoride supplementation if there are children under the age of nine in the household.
A Note Regarding Toothpaste, Fluoride and Young Children
Fluoridated toothpaste contains a large concentration of fluoride which is not normally a concern if the toothpaste is used properly. However, young children learning proper brushing techniques may swallow toothpaste and create a risk for excessive fluoride exposure. This is especially the case where fluoride is also coming from drinking water. Young children should be supervised while brushing teeth and be taught to properly spit out the used toothpaste and to apply only a pearl-sized drop of toothpaste on the brush.
Corrective Action
If a water test indicates the presence of fluoride, and there are children under the age of nine in the household, consult your dentist or physician about the test results. If fluoride levels are above 1.2 mg/l, the optimal treatment alternative may be to purchase bottled water for the children in the house. (Note: check fluoride content of the nutritional label or have the bottled water tested for fluoride content). Reverse osmosis, ion exchange, or distillation treatment units will effectively remove fluoride from your drinking water. Treatment will only be needed for drinking and cooking purposes, which could allow for a unit to be installed at the kitchen sink, also known as a point-of-use treatment. For more information on treatment options, refer to the following educational guidelines:
- Distillation Treatment of Drinking Water Systems
- Reverse Osmosis Treatment of Private Drinking Water Systems
When choosing a treatment method, consider both the initial cost and the operating costs. Operating costs include the energy needed to operate the system, additional water that may be needed for flushing, consumable supplies and filters, repair, and general maintenance.
Regardless of the quality of the equipment purchased, it will not perform satisfactorily unless maintained in accordance with the manufacturer’s recommendations for maintenance, cleaning, and part replacement.
Keep a logbook to record equipment maintenance and repairs. Maintaining equipment may include periodic cleaning and the replacement of some components. Consider any special installation requirements that may add to the equipment cost. For more information, see Questions to Ask When Purchasing Water Treatment Equipment.