Fluoride has been added to U.S. public drinking supplies since the 1940s.
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Water fluoridation is the addition of the chemical fluoride to public water supplies, for the purpose of reducing cavities. Of those served by municipal water systems, 67.1 percent of the United States' population has fluoride added to their water, according to the Centers for Disease Control and Prevention (CDC).
What is fluoridation?
Fluoride is an ionic compound containing fluorine, which is the single most reactive element; it is naturally found in many rocks. About 95 percent of the fluoride added to public water supplies is produced from phosphorite rock, according to the CDC.
Fluoride is added to public water supplies at an average concentration of about 1 part per million (1 ppm), or slightly below. Naturally occurring fluoride concentrations in surface waters depend on location but are generally low and usually do not exceed 0.3 ppm. Groundwater can contain much higher levels, however.
In 2015, the U.S. Department of Health and Human Services issued a recommendation for the optimal fluoride level that should be in drinking water to prevent tooth decay. This new recommendation is for a single level of 0.7 milligrams of fluoride per liter of water, opposed to the 0.7 to 1.2 milligrams per liter recommendation issued in 1962, which is now the standard.
The change is due to the fact that most people in the United States have a different lifestyle than when the guidelines were first put in place. "The adjustment in amount is more representative of the current needs of the population. Due to the increased use and accessibility of other fluoride sources (toothpaste, mouth rinse, etc.) and other improvements in oral health care, these new recommendations have been made," said Alice Lee, a pediatric dentist at Montefiore Medical Center in the Bronx, New York.
Using health products that contain fluoride while drinking water containing higher levels of fluoride can lead to a condition called fluorosis. This condition causes discoloration on teeth and misshapen teeth in children. "The new recommendations will maintain the caries prevention benefits of fluoride which have been proven by years of scientific research, and will simultaneously reduce the risk of dental fluorosis in younger patients," Edward H. Moody, Jr., a dentist and president of the American Academy of Pediatric Dentistry (AAPD), told Live Science.
How fluoridation works
Fluoride works by binding to tooth enamel, which is primarily made up of hydroxylapatite, a crystal composed of calcium, phosphorus, hydrogen and oxygen, according to Scientific American. By replacing the hydroxyl molecule on hydroxylapatite, fluoride makes the tooth more resistant to acid attack from bacteria. Exactly how fluoride helps protect teeth, and how much it protects them, however, isn't completely clear.
Tooth decay, when left untreated, can lead to serious health problems, such as infections that can spread into the jaw. Tooth decay has declined in the United States since fluoridation began, according to the CDC. However, it has also declined in other countries that do not fluoridate, according to the World Health Organization (WHO).
Since its introduction beginning in the 1940s, fluoridation has been the source of considerable controversy. Pro-fluoridation supporters say that the process is "safe and effective" for reducing cavities, particularly in poor children. Water fluoridation is endorsed by the American Medical Association, the American Dental Association and the CDC, which lists it as one of the top 10 most important public health measures of the 20th century.
Those on the opposite side say that it is unethical form of mass-medication, without each individual's consent or knowledge. By putting fluoride in drinking water, the dosage cannot be controlled, since some people — like laborers and people with kidney problems — drink much more water than others. Fluoride opponents cite studies showing that low levels of fluoride have been linked to a number of negative health effects like bone fractures, thyroid disorders and impaired brain development and function.
For example, study released by the National Institutes of Health (NIH) stated that children who have been exposed to fluoride have significantly lower IQ scores than those who are not. Though this study is often cited as proof by fluoride opponents, the study points to high levels of fluoride, found in such places as China near coal mines, as the cause of lower IQ, not the lower levels of fluoride found in drinking water.
The most obvious health effect of excess fluoride exposure is dental fluorosis, which when mild includes white streaks, and when severe can include brown stains, pits and broken enamel. As of 2010, 41 percent of kids ages 12 to 15 had some form of dental fluorosis, according to the CDC.
A 2009 study that tracked fluoride exposure in more than 600 children in Iowa found no significant link between fluoride exposure and tooth decay. Another 2007 review in the British Medical Journal stated that "there have been no randomized trials of water fluoridation," which is currently standard for all drugs.
It is important to note that most water supplies contain some naturally occurring fluoride, according to the Environmental Protection Agency (EPA). Fluoride can also enter drinking water supplies from discharge from fertilizer or aluminum factories.
Is fluoride bad for you?
It depends who you ask; fluoride is unquestionably toxic at certain concentrations. The CDC says that the level at which it is added to the water is safe and effective. Kerry Maguire, of the Forsyth Institute, an independent (not-for-profit) research institute in the United States specializing on oral health and its connection to overall wellness, agrees with the CDC.
"For the children I treat, fluoridated drinking water translates into fewer cavities requiring a trip to the dentist and more time in school," she said. "As a dentist and scientist – as well as a mother and grandmother – I welcome the CDC’s affirmation of the safety and effectiveness of community water fluoridation. Head to the tap and drink up!”
Water is fluoridated in 29 of the 30 largest cities. The exception is Portland, Ore. For the fourth time since 1956, voters in Portland defeated a plan in 2012 to add fluoride to the public water supply. For weeks, residents had been contentiously debating fluoridation.
Additional reporting by Alina Bradford, Live Science Contributor.
- EPA: Basic Information about Fluoride in Drinking Water
- Fluoride in Drinking Water: A Scientific Review of EPA's Standards
- Scientific American: Second Thoughts About Fluoride
- NIH: Confirmation of and explanations for elevated blood lead and other disorders in children exposed to water disinfection and fluoridation chemicals