Real Science, Real Safety by Effie Greathouse

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Dentaltown Magazine

If patients ask, here are the facts about fluoride levels in water

by Effie Greathouse

Hello, dentists and oral health professionals! I’m a PhD freshwater ecology researcher turned fluoride science enthusiast who, along with a colleague in public health, started a nonprofit website that explores any and all science related to fluoride and fluoridation.

For me, one of the reasons that working on the website has been so fun is that I’ve had a chance to learn so much about your science. (It has also come in handy for understanding my family dentists’ and hygienists’ recommendations better than ever.) I hope to get you into the spirit of cross-disciplinary learning, as well, because I think you’ll find it useful to have an environmental scientist’s view on true safety concerns about fluoride in water.

As you work with patients who have questions about fluoride, being up on the latest environmental health science for fluoride in water, and its relationship to fluoridation, will give you more foundation for answering those questions—particularly for patients concerned about green living, toxins and other environmental health concerns.

Much popular alarm about fluoride—whether about fluoridated water, fluoride in toothpaste or special fluoride treatments—is due at least in part to public misunderstanding of real environmental health science pertaining to fluoride in water. Understanding the true safety concerns about fluoride in water will help you address those worries.

So, here’s a mini review of the most important environmental science fundamentals on fluoride in drinking water. Let’s look at the U.S. Environmental Protection Agency’s main work on fluoride, and how the real science of protecting Americans from too much fluoride in drinking water fits in with the real science of small amounts of fluoride preventing cavities.

Role play: The CDC vs. the EPA
The Centers for Disease Control and Prevention and the EPA have complementary but distinct roles in the science of fluoride in water. While the agencies have done great work together in recent years, they still have fundamentally different responsibilities when it comes to fluoride.

The CDC and the Public Health Service are responsible for recommending and reviewing fluoridation levels. The CDC does things like advise the nation about what level of fluoride in water should be used by communities that fluoridate; collect and review data and literature on the evidence for community water fluoridation; and help to train local water operators in water fluoridation principles and science.

The CDC recommends the optimal amount of fluoride in water for oral health and community water fluoridation: 0.7 parts per million (ppm). Neither too much nor too little—the CDC and the Public Health Service say 0.7 is just right.

In contrast, the EPA is responsible for making sure that fluoride in water isn’t too high, whether from fluoride pollution or from geologic sources. The EPA develops upper safety limits for fluoride in water.

For fluoride pollution, the EPA does a great job of protecting U.S. air and water quality. Too-high levels of fluoride because of industry discharges is virtually unheard of in the U.S. nowadays, and in my view as an ecologist and environmental professional, I’m not so sure that would be the case if we didn’t have the EPA, the Clean Water Act, the Clean Air Act and other environmental laws and agencies.

Setting the limits
Before the EPA, we had events such as the 1948 Donora smog event. This pollution event involved hydrogen fluoride, sulfur dioxide and nitrogen dioxide from a big U.S. Steel plant, and the emissions were so massive that a temperature inversion resulted in the death of 20 people from acute fluoride poisoning or asphyxiation and thousands of people getting sick over the course of a few days.

For comparison, in my own state of Oregon just a few years back, computer chip manufacturer Intel was discovered to have had years of fluoride emissions violations. But the contrast between the Intel fluoride scandal and the Donora smog event illustrates how much things have changed. Intel was fined $143,000 by the Oregon Department of Environmental Quality—the highest penalty for an air quality violation in state history at the time—even though those emissions weren’t harmful. The company was not fined because it harmed human health; it was fined simply for making honest, unintentional (although egregious) mistakes in its fluoride emissions reporting. That kind of thing keeps companies in line and makes them do better. Our environmental laws and agencies, including the EPA, have made a world of difference in controlling all kinds of pollution, and that includes controlling fluoride emissions.

The second potential source of too-high fluoride in water—natural geologic sources of fluoride—is much more common, though. The EPA’s work on fluoride from natural sources is particularly important because there are several areas in the U.S. where water has high levels of fluoride because of geology.

Mother Nature is actually the biggest culprit in causing too-high fluoride. Natural sources of fluoride in water puts millions of people in countries like India, Iran, Ethiopia and China at high risk of endemic skeletal fluorosis. But the U.S. has had the EPA watching out and working with local water districts to prevent drinking water treatment plants from tapping into water sources with fluoride levels that cause this condition.

The EPA mandates that public drinking water utilities and companies not distribute any water with fluoride levels above 4ppm, and very few provide water with fluoride even close to this level. This regulation helps ensure that skeletal fluorosis is extremely rare in the United States. Cases of skeletal fluorosis in America have only occurred in a handful of patients, and in the past couple of decades, they’ve been because of behaviors unrelated to fluoride in water, such as excessive tea drinking (tea can be high in fluoride), or excessive toothpaste use/consumption over a period of decades.

EPA also recommends that 2ppm is a better upper limit for fluoride in water than 4ppm. This lower level is recommended to prevent severe dental fluorosis. While the EPA doesn’t mandate that drinking water treatment plants keep fluoride in water below 2ppm, it does mandate that those water districts notify customers every year about the risk that children could develop severe dental fluorosis at levels above 2ppm, and that kids should drink from a different water source that is less than 2ppm. Of course, the CDC, the American Dental Association and dentists like you would prefer that everyone get only the ideal recommended level of fluoride in water: 0.7ppm. But when a community’s water source is far above the ideal, the EPA is there helping make sure people know their water is a risk for serious cosmetic effects on kids’ teeth.

Should the EPA lower the mandate to 2ppm?
The EPA has been questioning and discussing for decades, within the agency and with other public health experts, what the upper safety limits for fluoride in water should be. Even back in the 1980s, in the early history of the agency, the EPA needed assessments of the science to inform decision-making, while the agency and scientists were questioning whether upper limits for fluoride should be higher or lower. For example, in 1982, EPA sought guidance from the Surgeon General’s Office. A historic memo from Surgeon General C. Everett Koop in response to the EPA’s request is a nice summary of many of the scientific questions and uncertainty behind the merits of an upper limit in the neighborhood of 2ppm vs. the merits of a higher limit. It also shows how much concern public health professionals like Koop had for making sure the EPA picked a science-based system that ensured people don’t get too much fluoride and kids don’t get severe dental fluorosis.

In 2003, the EPA wanted to take another serious look at the question, so it commissioned the National Academies of Sciences to assemble a panel to review new literature and report on whether the 4ppm level was protective against adverse health effects. In 2006, the panel reported back: unanimous agreement from 12 independent scientists that EPA should lower the maximum contaminant level goal (MCLG) from 4ppm to something lower.

The report made headlines and was an important scientific accomplishment (while also managing to be a source of confusion for all kinds of people looking into fluoride who don’t have the time and skills to read a 500-page scientific review). While I’m not going to describe all 500 pages here, I do want to discuss one other key result of the panel’s review: 10 of the 12 panel members agreed that the risks from severe dental fluorosis at levels close to 4ppm are not merely cosmetic. They agreed that severe dental fluorosis can be an adverse health effect because enamel can be missing when teeth are severely fluorosed. The majority on the panel viewed the pitting in severe enamel fluorosis as more than a merely cosmetic issue. The remaining two panel members disagreed that severe enamel fluorosis was a health effect, but they did think the cosmetic concerns are important enough that EPA should lower the 4ppm MCLG level.

What has the agency been doing since 2006 on this question of whether to lower the 4ppm upper limit? The EPA reviews drinking water standards every six years. To support those reviews and to consider the panel’s recommendations, the EPA has done a variety of analyses and reports, but in its most recent review, the EPA judged fluoride as a low priority for changes to the upper safety limit; other drinking water treatment safety concerns are higher priorities. One of the reasons that it may not be necessary to prioritize lowering the limit is that health care workers and dentists in communities with fluoride levels near or above 2ppm are likely already working to make sure parents know of the need for an alternative source of water for kids. Likewise, the notifications that go directly to water customers every year inform people of the need, too.

So the official national upper limits remain: Less than 4ppm is mandated, while less than 2ppm is better.

However, for the optimal level, that level has changed: 0.7ppm is best now. We no longer recommend the range from 0.7 to 1.2 depending on climate, because recent research confirms that we don’t have relevant differences nowadays in how much water we drink based on climate. EPA scientific assessments and staff played an important role in the change of the optimal level, although it was still the CDC and the Public Health Service’s charge first and foremost.

My professional opinion on prospects of lowering the mandatory upper limit from 4ppm to something around 2ppm? Given limits on staff and funding at the EPA, I think its maintenance of the levels that have served us well in keeping skeletal and severe enamel fluorosis so rare in the U.S. makes sense. If I had a magic wand, though, I’d make it so the EPA had all the funding it needs to do both its high- and low-priority work on the science of drinking water treatment and also rule making; I would grant water districts in natural high-fluoride areas with the resources they need to meet any new upper safety limits; and I’d wish into place reliable drinking water treatment for every citizen of every country on the planet.

Alas, I’m just a scientist, so my only magical power is to plug away at helping everyone I can understand more facts about fluoride—whether it’s too high, too low or just right.

But I’m happy I got the chance to share these environmental health facts about fluoride with you, because you can share them with patients who need them. Now you’ve got more background to help patients who have fears about fluoride being toxic, whether it’s a parent who has questions about her kids drinking fluoridated water and things she’s read online about fluoride toxicity; a senior who has heard claims about fluoride causing cavities and spots on teeth; or a green-minded millennial who knows something about EPA saying fluoride in water is bad.

You’ve got resources and facts to reference in-office for those who need just a few more details to understand the basics and make their prevention plan with you. With more of the real environmental health science in your back pocket, you’ll be better equipped to help them understand fluoride toxicity at levels that are too high and how that relates to the beneficial role of fluoride in preventing cavities at low levels.

Author Bio
Author Effie Greathouse earned a bachelor’s degree in wildlife, fish and conservation biology from the University of California, Davis, and a PhD in ecology from the University of Georgia, where she did research on freshwater shrimp and dams in Puerto Rico. She did postdoctoral training at the U.S. Environmental Protection Agency, focusing on water quality and stream chemistry of the Oregon Coast Range. She is currently director of Digital Resources for Community and Science, and the Fluoride Exposed project (, based in Portland, Oregon.
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