A neighborhood kid once caught hand, foot, and mouth disease from my daughter before we had any signs that she had it. Her mother scolded me and asked me to please alert them next time my daughter was sick.


I don’t blame her for being protective. That illness is a doozy, as many of you likely know from experience. But being reprimanded by another parent when both our toddlers were so sick just made the whole thing worse.

This in-person interaction made me feel awful and I quickly turned to my virtual support network to share my thoughts and for reassurance. And I’m not unique.

As anxious parents, we persistently echo our worries and stories through blogs, videos, and other social media outlets. Connecting with other parents through social media provides us with important support, and even desperately needed humor! Being a parent can be isolating, so seeing our own beliefs and experiences reflected back on social media can be reassuring. This can be helpful when we feel vulnerable like I did when another mother chided me, but it can also be harmful.

As a professor of Oral Health and Epidemiology at the Harvard School of Dental Medicine, my research demonstrates that what is shared across the Internet often contradicts scientific consensus and current knowledge on a variety of health topics. It can be comforting to hear our own beliefs reflected back to us, but it’s harmful when those beliefs aren’t accurate.

Nearly 80% of us search for health information online. The internet is a rich network of information, but also of misinformation. A lot of this misinformation has shaken parents’ confidence in some of public health’s greatest achievements, including fluoridated water. One of my favorite quotes, from Thomas Patterson, Bradlee Professor of Government and the Press at the Harvard Kennedy School, states, “The internet is at once a gold mine of solid content and a hellhole of misinformation.”

Last year, we celebrated 70 years of community water fluoridation in the United States. Over 120 of the world’s leading health, dental, and medical organizations praise the success and benefits of fluoridation. As a dentist, water fluoridation is a topic I am very familiar with and it’s one that there’s a lot of misinformation about on the internet. Often parents ask me the same five questions about water fluoridation, but most of us don’t have easy access to a dental epidemiologist, so I’ll answer them for you here, from one parent to another:

1) Is fluoridated water safe to drink? Yes.
From time to time, you will see a scary-sounding study float fluoride-infographic-how-it-worksacross your Facebook page. But it’s important to
remember that expert consensus and an enormous body of sound, scientific evidence continue to find that fluoridated water is safe and does not contribute to or cause illness or disease.

The Facts:

  • A U.S. Public Health Service review of data and research concluded, “Expert panels which reviewed the international body of literature agree that there is no credible evidence of an association between either natural fluoride or adjusted fluoride in drinking water and human cancer.”
  • The consumption of fluoridated water has not been shown to cause or worsen conditions of the thyroid, kidney, heart, or other glands/organs. The only proven risk associated with excess fluoride is a cosmetic condition known as dental fluorosis. (See below.)
  • For more information, see Common Questions about Fluoride.

2) If Fluoride is a chemical, why is it safe to have in our drinking water? 

When we use the word ‘chemical’ we sometimes take it to mean dangerous, but the truth is that everything that occurs naturally (and man-made) has a chemical structure, even water and oxygen.

Fluoride is a naturally occurring element in all water sources; some fluoride levels are too low for any dental benefit and some sources are very high. Fluoridation is the process of adjusting these levels for optimal dental benefit while minimizing risk for fluorosis.

3) Is fluoridated water safe for children, babies, and formula-fed infants? Yes.

Parents often ask me if fluoridated tap water is safe to mix formula for their infants or if they need to purchase distilled or bottled water. If you’re on a municipal water supply and there aren’t unrelated issues with the safety of your tap water (as in the case in Flint, Michigan), fluoridated tap water is safe for children, babies and formula-fed infants.

 The Facts:

  • The American Academy of Pediatrics (AAP), the American Dental Association (ADA) and the Centers for Disease Control and Prevention (CDC) are among many who agree that water fluoridation is a safe and effective way to prevent tooth decay in children.
  • According to the ADA, it is safe to use fluoridated water to mix infant formula. The risk if mixing infant formula with fluoridated water is mild fluorosis. (See below.) If you have concerns, talk with your pediatrician and dentist.
  • For more information, see Fluoride and Children.

 4) Does fluoridated water negatively affect IQ or children’s developing brains? No.

Between the 1940s and the 1990s, the average IQ scores of Americans improved 15 points – at the same time that fluoridation expanded to serve millions more people. To be clear, this is a case of correlation, not causation. There is nothing in the peer-reviewed literature to suggest fluoridated water has caused the increase in IQ scores. Some have claimed that fluoridated water has decreased IQ scores in the US, and we know that’s just not true as American’s IQ scores have risen alongside the use of water fluoridation.

The Facts:

  • Many point out a study known as the ‘Harvard study’ (ironic, I know), which postulated an inverse relationship between fluoridated water and IQ. It’s important to note that this study looked at the IQ scores of children in China, Mongolia and Iran and in many of these areas, the water had exceedingly high levels of naturally occurring fluoride – as much as 10 times higher than levels used to fluoridate public water systems in the U.S.
  • The study did not test cause and effect or conduct research designed to explain a possible relationship between fluoride and IQ. Numerous experts have debunked this claim, myself included.
  • For more information, see Does Fluoride Lower IQ Scores?

 5) What exactly is dental fluorosis? Should I be concerned about fluorosis from drinking fluoridated water?

Dental fluorosis is a change in the appearance of the teeth, typically in the form of very faint white markings. It does not affect the function or health of the teeth. In fact, teeth with mild fluorosis are more resistant to cavities.

Fluorosis is the result of consuming too much fluoride while teeth are forming, before the age of 8, particularly if children swallow fluoridated toothpaste. The American Dental Association recommends specific quantities of toothpaste according to age, in order to minimize the risk of fluorosis. For optimal dental health, provide water fluoridated at the recommended levels and supervise brushing so that children learn to spit, not swallow.

 6) How much fluoride do children need? What are the recommended levels?

The fluoride that is added to public water supplies conforms to stringent safety standards and results in water that complies with the Safe Drinking Water Act. The quality and safety of fluoride additives are ensured by Standard 60, a program that was commissioned by the U.S. Environmental Protection Agency (EPA). This program is monitored by an independent committee of experts, including the Association of State Health Officials and other key organizations.

In 2015, the Department of Health and Human Services recommended that the level of fluoride in drinking water be set to a uniform level (0.7 mg/liter) across the nation. This resulted from research showing no difference in water consumption in warmer climates and responded to the increased availability of fluoride from a variety of sources by reducing the amount contained in water. 

Take home message: Fluoridated water is safe. Children and adults who consume a typical diet, drink optimally fluoridated water, and use fluoridated dental products as recommended will not exceed the maximum levels for fluoride. And they’ll have healthier teeth!

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Categories: Policy, Politics, + Pop Health, Science 101 + Mythbusting