Private Well Water and Fluoride - Engineering Fact Sheet- Community Water Fluoridation

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Centers for Disease Control and Prevention

Private Well Water and Fluoride

This fact sheet addresses questions that consumers may have on fluoride levels in groundwater from private wells.

How do I know if my water is from a public water system or a private well?
The U.S. Environmental Protection Agency defines a Public Water System as a system that serves 25 or more people per day. If you have water service from a well that has a limited delivery, such as to your house but not to your neighbor’s house, then you likely have a private well.

What are the governmental regulations for private wells?
Although most U.S. households are connected to a public water system, the U.S. Geological Survey report “Estimated Use of Water in the United States in 2005” estimates that 14% of United States residents rely on private wells that are not regulated by the EPA Safe Drinking Water Act. In most states, private wells are not regulated by governmental regulatory entities. Therefore, it is the responsibility of the homeowner to know and understand the quality of the water from their well. The U.S. Environmental Protection Agency suggests that all wells be tested for quality once every three years since influences to well water quality can change over time. Contact your public health office for their advice on testing of private wells in your state or area. Additional information on testing well water quality in private wells serving homes can be found on the U.S. Environmental Protection Agency Web site.

My home gets its water from a private well. What do I need to know about fluoride and groundwater from a well?
Fluoride is present in virtually all waters at some level, and it is important to know the fluoride content of your water, particularly if you have children. A 2008 U.S. Geological Survey study found that 4% of sampled wells had natural fluoride levels above the EPA Secondary Maximum Contaminant Level (SMCL) of 2 mg/L. A smaller set of 1.2% of all wells exceeded the Maximum Contaminant Level (MCL) of 4 mg/L. If you have a home well, the EPA recommends having a sample of your water analyzed by a laboratory at least once every three years. Check with your dentist, physician, or public health department to learn how to have your home well water tested.

What should I do if the water from my well has less fluoride than the recommended level of 0.7 mg/L? Can I add fluoride?
The recommended fluoride level in drinking water for good oral health is 0.7 mg/L (milligrams per liter). If fluoride levels in your drinking water are lower than 0.7 mg/L, your child's dentist or pediatrician should evaluate whether your child could benefit from daily fluoride supplements. (The prescription dosage of fluoride supplements should be consistent with the schedule*

(PDF–431K) established by the American Dental Association (ADA) Council on Scientific Affairs.) Their recommendation will depend on your child's risk of developing tooth decay, as well as exposure to other sources of fluoride, such as drinking water at school or daycare, and fluoride toothpaste. It is not feasible to add fluoride to an individual residence’s well.

What should I do if the water from my well has fluoride levels that are higher than the recommended level of 0.7 mg/L?
In some regions in the United States, community drinking water and private wells can contain levels of naturally occurring fluoride that are greater than the level recommended by the CDC for preventing tooth decay. Consuming water with fluoride between 0.6 and 2.0 mg/L results in reduced tooth decay, but consumption of water with fluoride exceeding 2.0 mg/L may increase the potential for dental fluorosis.

The U.S. Environmental Protection Agency (EPA) currently has a non-enforceable recommended guideline for fluoride of 2.0 mg/L to protect against dental fluorosis. If your home is served by a private well that has fluoride levels exceeding this recommended guideline, but lower than 4.0 mg/L, then it is best to provide children under 8 years of age with an alternative water source, such as bottled water with a low fluoride content.

Continue to test your well water’s quality every three years as recommended by EPA.

What should I do if my well water was measured as having too much fluoride (level greater than 4 mg/L)?
It is unusual to have the fluoride content of water exceed 4 mg/L. If a laboratory report indicates that you have such excessive fluoride content, it is recommended that the water be retested. At least four samples should be collected, a minimum of one week apart, and the results compared. If one sample is above 4 mg/L and the other samples are less than 4 mg/L, then the high value may have been an erroneous measurement. If all samples register excessive levels greater than 4 mg/L, then you may want to consider investigating alternate sources of water for drinking and cooking, or installing a device to remove the fluoride from your home water source. Physical contact with high fluoride content water, such as bathing or dishwashing, is safe since fluoride does not pass through the skin.

What are the health risks of consuming water with fluoride levels greater than 4 mg/L?
Children aged 8 years and younger have an increased chance of developing severe tooth dental fluorosis. Consumption over a lifetime may increase the likelihood of bone fractures, and may result in skeletal fluorosis, a painful or even crippling disease. The U.S. Environmental Protection Agency has determined that safe exposure of fluoride is below 4 mg/L in drinking water to avoid those effects.

Will using a home water filtration system take the fluoride out of my home’s water?
Removal of fluoride from water is difficult. Most home point-of-use treatment systems that are installed at single faucets use activated carbon filtration, which does not remove the fluoride. Reverse osmosis point-of-use devices can effectively remove fluoride, although the amount may vary given individual circumstances. For a home point-of-use device to claim a reduction in fluoride, it must meet National Sanitation Foundation (NSF) Standard 58 criteria for fluoride removal. Standard 58 requires that a device must achieve a 1.5 milligrams per liter (mg/L) concentration in the product water if the original concentration was 8.0 mg/L, or approximately 80 percent removal. This percentage removal may not be consistent at lower concentrations of fluoride. Check with the manufacturer of the individual product for specific product information.

Fluoride is not released from water when it is boiled or frozen. One exception would be a water distillation system. These systems heat water to the boiling point and then collect water vapor as it evaporates. Water distillation systems are typically used in laboratories. For home use, these systems can be expensive and may present safety and maintenance concerns.

Can I use water with fluoride for preparing infant formula?
Yes, you can use well water for preparing infant formula. It is important, however, to ensure that the well water has been recently tested to verify safety. EPA suggests that well water should be tested a minimum of once every three years for micro-organisms and other substances. In addition, parents of young children should also have their well water tested for fluoride content.

For more information on private well testing, contact your local health department or visit the EPA Web site. Parents and caregivers should speak with their pediatrician to review the results of the private well testing and to determine if the well water should be boiled prior to mixing the formula. If you are advised to boil the water, be sure to boil the water only one time so that you don’t concentrate substances by the boiling process itself.

If your child is exclusively consuming infant formula reconstituted with well water, and if that water contains fluoride, there is an increased chance for dental fluorosis. To lessen this chance, parents can use low-fluoride bottled water some of the time to mix infant formula; these bottled water are labeled as de-ionized, purified, demineralized, or distilled. For more information, see Overview: Infant Formula and Fluorosis.

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