Fluoride and cancer risk

This page was reviewed under our medical and editorial policy by

Carolyn Lammersfeld, MBA, MS, RD, CSO, LD, Vice President of Supportive Care Services

This page was reviewed on January 29, 2022.

It’s colorless, odorless and may have saved you a trip to the dentist. Whether you realize it or not, your water probably contains fluoride, a mineral compound known to promote healthy teeth. In many places, fluoride is added to the public water supply in an effort to improve the dental health of the general population.

But despite all the toothaches it may have prevented, concerns about the safety of fluoride have persisted over time. While research into this topic is ongoing, there’s little evidence that fluoride is harmful or causes cancer.

What is fluoride?

Fluorides are naturally occurring compounds found in rock, soil, air and, most notably, water. In the early part of the 20th century, dentists and researchers in the United States noted that in places where relatively higher levels of naturally occurring fluoride were present in the drinking water, residents had lower rates of dental caries (cavities and tooth decay). In the following decades, researchers and public health officials in cities and towns piloted programs to add fluoride to public water supplies and found improvements in the oral health of the population. By 1962, U.S. public health officials identified a recommended range of fluoride concentration for drinking water.

Since then, the percentage of the U.S. population receiving fluoridated water has steadily grown. While some communities have decided not to fluoridate their water supplies, by 2018, about 73 percent of the population’s water supply contained fluoride, either added to the supply or occurring naturally, according to the Centers for Disease Control and Prevention (CDC). The current recommended concentration is 0.7 mg of fluoride per liter of water—slightly lower than the original 1962 recommendations—but fluoridation programs continue to flourish across the country.

What does fluoride do in the body?

Fluoride enters the body through water, food or oral hygiene products such as toothpastes, mouthwashes or dental treatments. In some countries in Europe and South America, fluoride may also be found in table salt. Once absorbed in the digestive tract, some fluoride gets stored in the bones and teeth, where it stimulates new bone growth and strengthens teeth. Over time, that strength helps fight tooth decay that occurs during eating.

While fluoride has proven benefits for dental health, there is such a thing as too much fluoride—particularly for children.

  • One common problem associated with too much fluoride is fluorosis, a condition that causes a range of changes to the appearance of tooth enamel, from little white spots to brown stains or even a rough, sanded-away appearance on the tooth surface. Fluorosis results from excessive fluoride exposure as a child (while adult teeth are still forming), usually through a combination of fluoride sources such as toothpaste and drinking water.
  • More rarely, in people exposed to very high levels of the compound over a long period of time, fluoride may build up in the bones and cause skeletal fluorosis. For these reasons, the EPA regulates the quantity of fluoride allowed in drinking water.

The CDC recommends that adults make sure children don’t swallow toothpaste when they brush their teeth, and to get to know the fluoride levels in your local drinking water.

Residents of areas where the naturally occurring fluoride exceeds 2 mg/L should have an alternative source of water for children younger than 8 years old.

What to know about fluoride and cancer

The risk of cancer from fluoridated water has been a subject of controversy and debate for many years, though no conclusive evidence that it causes cancer has been established. One major area of concern is osteosarcomas, or bone tumors. This was prompted by a study with animals, not humans.

In a study from the National Toxicology Program in the early 1990s, mice and rats were fed water with high levels of fluoride over a period of two years—more fluoride than is present in drinking water. The results showed a small occurrence of osteosarcomas in the male rats.

Shortly after, the U.S. Public Health Service reviewed more than 50 population-based studies and concluded that fluoridation of drinking water at the recommended concentration doesn’t pose a detectable cancer risk to humans. Subsequent reviews by other agencies such as the CDC and the National Academy of Sciences reached similar conclusions. In 2011, a study in the Journal of Dental Research looking at bone fluoride levels in bone cancer patients found no significant association between bone fluoride levels and osteosarcoma risk.

Overall, public health agencies in the United States and abroad acknowledge that even though no conclusive links between cancer and fluoride have been established, further research is needed.

Fluoride and your community

How much fluoride you’re exposed to depends on your drinking water supply. To learn about fluoride in your community, the CDC has a tool called My Water’s Fluoride. You may also contact your local community water source, as well as the EPA’s Safe Drinking Water Hotline at 1-800-426-4791. For people with private wells, it’s important to have the water tested by a reputable agency to ensure fluoride levels are within the safe recommended range.

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