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What every dental hygienist should know about fears over fluoride

Aug. 1, 2019
An environmental scientist shares the surprising (and understandable) reason your patients may be concerned.

Effie Greathouse, PhD

Much confusion and misinformation floats around out there about fluoride and fluoridation—and a significant amount of that confusion is environmentally minded. Lots of people are scared about fluoride being toxic. Memes characterizing fluoridation and fluoride products as hazardous waste and part of an industrial pollution scheme have been persistent since the discovery of fluoride’s role in caries prevention in the 1930s, 1940s, and 1950s.

In my opinion, as an environmental scientist turned fluoride science enthusiast, the confusion isn’t just because of conspiracy theorists.

My professional background is in water quality, freshwater conservation, and aquatic ecology. I have become passionate about fluoride science communication, working with colleagues in public health to develop a web-based nonprofit dedicated to exploring science using fluoride as a theme. My background has given me a unique perspective on those long-running fears and concerns about fluoride.

From my perspective, fluoride is prone to these fears in part because there are legitimate concerns and all sorts of real science about unsafe levels of fluoride. In particular, in some US communities, unsafe levels of fluoride occur naturally in water that may be the source of drinking water.

What’s more, legitimate concerns about these naturally-occurring high levels  constitute some pretty tricky science. Even if you’re only looking at the real science of fluoride in water, it can be hard to follow. Especially if you’re a nonspecialist trying to decipher jargon from one of my favorite science agencies—the US Environmental Protection Agency (EPA)—one of my favorites because I did my postdoctoral research there.

I would like to share with you how real science from EPA contributes to unfounded fears of fluoride.

Differing roles of CDC and EPA

The Centers for Disease Control and Prevention (CDC) and the Public Health Service (PHS) promote community water fluoridation. The agency mandate at CDC with respect to fluoride has a major focus on preventing cavities, reviewing the science of fluoridation and recommending the ideal level of fluoride in water.

Preventing severe forms of fluorosis is in the CDC’s purview as well, and they work hard on it—for example, by measuring fluorosis in national surveys, and providing FAQs on fluorosis. But the bulk of their communications discuss what fluoridation and other small amounts of fluoride can do for cavity prevention.

In contrast, the agency mandate at the EPA is to control high levels of fluoride that would honestly be dangerous. The EPA is not in the business of preventing cavities. This doesn’t help with all the fears and confusion, because it means that EPA talks a lot about fluoride dangers, and not so much about the low levels of fluoride that are beneficial.

Add in all the misinformation online, and you’ve got a recipe for misunderstanding about whether fluoride is safe and beneficial, or whether it is poisoning our precious bodily fluids. It can be really easy to come away with a false impression that the EPA and CDC are at odds with each other about fluoride when, in fact, they both agree that fluoride is beneficial in water at low levels and is unhealthy if it is too high.

Jargon that adds to the confusion

There is plenty of jargon and technical language in drinking water treatment science and the EPA’s web pages on drinking water safety that can add to the confusion and fears. The technical writing can simply be confusing sometimes. Other times, it sounds downright scary.

Let’s start with some of the straight up confusing stuff: water chemistry units. Both the ideal level for community water fluoridation from the CDC and PHS and the upper limits for safety from the EPA are in parts per million (ppm), which are equal to mg/L. Small units like these are hard concepts for us to really grasp. For a great resource for brushing up on chemistry units, or understandable analogies for them (e.g., 1 ppm is the equivalent 1 minute in 2 years), visit bit.ly/RDHfl.

Keeping the numbers straight adds to the mental load, too. The CDC’s ideal for community water fluoridation is 0.7 ppm,1 while the EPA recommends 2 ppm as an upper limit to protect against severe enamel fluorosis, but mandates 4 ppm as an upper safety limit to protect against skeletal fluorosis.2

Our brains can work against us to gloss over decimals and differences in numbers like these. Furthermore, scientists trying to be helpful by explaining toxicology concepts such as “the dose makes the poison” aren’t fully thinking through that all that most people hear there is “poison.” Distinctions between the ideal level and too-high levels can be tough to communicate.

What I think really adds to the confusion is how the EPA and drinking water treatment science officially write about too-high fluoride in water. A good example is that in the science behind upper safety limits for drinking water, we use the term “contaminant.” So in the EPA’s world, if we’re talking about fluoride, we’re generally talking about it as a “contaminant.”

Well, jeez, no wonder there are members of the public who come at your recommendation to use fluoride toothpaste or drink fluoridated tap water with retorts about it being poison and toxic. The nuance that it is only really a “contaminant” if it is above a much higher level can so easily get lost.

Then there are all the abbreviations. Three important abbreviations for EPA’s upper limits are MCL, MCLG, and SMCL. Do you feel like we’re in an alphabet soup yet? Well, explaining and defining these will help, but even with explanation, they are still kind of confusing.

MCL is the maximum contaminant level. That is the mandated upper limit of 4 ppm, which I mentioned above. The EPA does not allow any public drinking water system to use and distribute water if its fluoride content is above this level.

MCLG is the maximum contaminant level goal. If you’re thinking that the MCLG must be the 2 ppm level I mentioned above, for which the EPA recommends but does not require drinking water treatment plants to be below to prevent cosmetic concerns . . . well, that would be very logical, wouldn’t it? But nope! In drinking water safety, the MCLG is an upper safety limit of a compound based solely on the health science. The MCL is what’s technologically feasible, and it’s the mandate. The mandated MCL can be higher than the ideal MCLG for health. In the case of fluoride, though, the MCL and MCLG are the same: 4 ppm.

The SMCL is, in fact, the 2 ppm number to protect against severe enamel fluorosis. SMCL stands for secondary maximum contaminant level. (That’s right, we’ve got two different maximums for fluoride. Who the heck came up with this not completely logical naming system?) Anyway, SMCLs are for the EPA to provide local water treatment plants with guidance to keep substances below levels that cause cosmetic effects in people or aesthetic concerns with the water such as smell and taste issues. SMCLs let the EPA advise on things that aren’t health problems, without requiring local water treatment plants to remove these things that aren’t health problems.

In the case of fluoride, the SMCL lets the EPA advise on the effects of severe dental fluorosis as a cosmetic issue (note that there is debate over whether severe dental fluorosis is an adverse health effect or merely cosmetic among scientists EPA has asked to assess this question3). These effects—whether viewed as a cosmetic effect or an adverse effect—can be avoided if children below the age of nine are given an alternative source of drinking water during the years that enamel is forming. The EPA requires the relatively small number of water systems that have levels between 2 ppm and 4 ppm to notify customers of this need for an alternative source for kids.

Dentists and other health-care providers in these communities also play an important role in helping families understand the need for an alternative water source or water filter.

Whew, OK, those are just some of the abbreviations involved, but I’m going to move on to the final aspect of EPA jargon that I think is especially confusing—phrases that make it sound like the EPA thinks fluoride is just the devil, at all times, in all situations, when in fact, these scary-sounding phrases are really talking about fluoride specifically when it is too high.

Here are some scary-chemical quotes from totally legitimate EPA pages online:

• “EPA acknowledges new information regarding the exposure and health effects of fluoride”4

• “Fluoride risk assessment and relative source contribution”5

• “Exposure to excessive consumption of fluoride over a lifetime may lead to increased likelihood of bone fractures in adults, and may result in effects on bone leading to pain and tenderness. Children aged 8 years and younger exposed to excessive amounts . . . have an increased chance of developing pits in the tooth enamel, along with a range of cosmetic effects to teeth.”6

These kinds of phrases really emphasize fluoride being a regulated source of exposure, health effects, and risk—and they’re super relevant to those communities with natural geologic sources of fluoride that honestly cause too high fluoride in water. But these scary phrases are not so relevant or helpful when you are recommending fluoride toothpaste or varnish to your patients in your town where water is at a safe and beneficial fluoridated level or below.

Fluoride-hesitant patients may have their own—or others’—efforts to interpret these kinds of EPA phrases adding to their thinking about fluoride. That thinking could come out as being overly worried about “risk” and “exposure” (or “toxins” and “poison”) and not sufficiently worried about caries, decay, and strong enamel.

Where the EPA really stands

Phrases about exposure and risk such as the above are what dominate EPA materials. The EPA’s main job is to deal with too-high fluoride. But it is less well-known that the EPA is another science agency that says fluoride is a cavity-fighter just like so many other health organizations who recognize the public health benefits of fluoridation. The following are quotes from EPA that are easy to miss because they aren’t the EPA’s primary focus when they deal with fluoride. But these are absolutely this public health agency’s statements in official materials on the science of fluoride:

• “Water additive which promotes strong teeth”7

• “Talk with your dentist about the best use of fluoride to prevent tooth decay.”2

• “Water fluoridation is beneficial for reducing and controlling tooth decay and promoting oral health in children and adults.”2

• “Fluoride toothpaste is effective for preventing tooth decay and does not contribute to fluorosis unless it is swallowed.”2

Your expertise on fluoride and the fact that the EPA recognizes its benefits is something you can keep in your back pocket if you have patients with environmental-based fears of fluoride.

Just for good measure

Let’s take one more look at how EPA quotes can be confusing, though. The quote above about fluoride being a water additive that promotes strong teeth comes from the EPA’s table of drinking water standards. If we add in the titles of the table and the full entry for fluoride, this is the whole thing:

• Contaminant: Fluoride

• MCLG1(mg/L): 4.0

• MCL or TT1(mg/L): 4.0

• Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term): Bone disease (pain and tenderness of the bones); Children may get mottled teeth

• Sources of Contaminant in Drinking Water: Water additive which promotes strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories

Man, that’s rough to parse. The fact that the EPA recognizes that fluoride promotes strong teeth comes under the header “Sources of Contaminant in Drinking Water.” The “contaminant” aspects only apply if fluoride is far above the level that promotes strong teeth, and the EPA recognizes fluoride strengthens enamel if at the right levels.

I have seen public misinterpretations of these EPA drinking water treatment standards on fluoride. I know that local treatment plants are required to send water quality reports that include this kind of information on fluoride to their customers every year. So lots of people go look up these details from the EPA or hear about them third-hand from friends, family, and groups on social media. I have seen people misunderstand the EPA’s jargon and mistakenly believe it says fluoridation is a contaminant.

I hope that my professional perspective on the role that the EPA and drinking water treatment jargon inadvertently has in stoking fears and misunderstandings will be useful to you as you promote oral health. The EPA’s technical language is important for ensuring that we take true risks the EPA has identified for communities with naturally too-high fluoride seriously. But if we also understand that the technical language can be confusing and scary-sounding, we can better figure out how to reduce that confusion and unnecessary worry about beneficial levels of fluoride. 

Editor’s note: This article originally appeared on DentistryIQ in April 2018, and has been edited slightly from the original.


1. Community Water Fluoridation FAQs: Public Health Service Recommendation. Centers for Disease Control and Prevention website. https://www.cdc.gov/fluoridation/faqs/public-service-recommendations.html.

2. US Environmental Protection Agency. Questions and answers on fluoride. https://www.epa.gov/sites/production/files/2015-10/documents/2011_fluoride_questionsanswers.pdf. Published January 2011.

3. National Research Council. Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. Washington, DC: The National Academies Press; 2006.

4. Review of the fluoride drinking water regulation. US Environmental Protection Agency website. https://www.epa.gov/dwsixyearreview/review-fluoride-drinking-water-regulation.

5. Fluoride risk assessment and relative source contribution. US Environmental Protection Agency website. https://www.epa.gov/dwstandardsregulations/fluoride-risk-assessment-and-relative-source-contribution.

6.   What are fluoride’s health effects? US Environmental Protection Agency website. https://safewater.zendesk.com/hc/en-us/articles/211402338-3-What-are-fluoride-s-health-effects-. 

7. National primary drinking water regulations. US Environmental Protection Agency website. https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations. 

Effie Greathouse, PhD, is a freshwater ecologist and conservation biologist with a bachelor’s in wildlife, fish, and conservation biology, a doctorate in ecology, and a postdoctorate in water quality at the U.S. EPA. Together with colleagues in public health, she explores fluoride and fluoridation at a tongue-in-cheek nonprofit, Fluoride Exposed, where they promote public and professional understanding of fluoride science across disciplines. She can be contacted at fluorideexposed.org.