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If you've heard the name Emily Oster, it's probably because you or someone you know is having a baby. Yeah, so I started writing about pregnancy when I got pregnant with my first kid, who is now 14. And when she started talking to her doctors, she immediately heard about all the things she couldn't have. You can't have hot dogs, you can't have jelly meats, you can't have sushi, you can't have coffee, you can't have alcohol. There was a lot of can't, but not a lot of why. So Emily asked her doctors what they thought about it.
What exactly was the risk she was avoiding? Like, how strong was the evidence? Like, okay, if I avoided ham, how much would that change my risk of listeria? Like, how much do we really know and how large is any given risk? Emily thought these were pretty basic questions. And she was kind of shocked when her doctors just didn't have the answers.
Emily's a health economist at Brown, so in order to get the kind of answers she was looking for, she decided to go straight to her comfort zone: the actual studies. Some of what she found lined up with conventional wisdom, like cigarettes, definitely bad. But a lot of it wasn't as black and white as she'd been told.
The data said a ham sandwich every once in a while wasn't so bad. Neither was a cup of coffee. But then some things that seemed helpful, like bed rest, way riskier than you might think. And then when her friends started getting pregnant, they started coming to her for advice. So much that she decided to write a book. It's called Expecting Better, and it was an instant bestseller. There were clearly lots of people out there who wanted something like this.
At the same time, the book was kind of controversial. It went against lots of conventional wisdom about what pregnant people should or shouldn't do. Some people thought Emily was being a little cavalier.
But Emily just saw herself as laying out the evidence. She didn't want to tell people what to do. Her point was that pregnant people shouldn't be talked down to, that they can handle the data and they can make their own decisions. You know, we can tell people a number and then we need to help them understand the number. For me, that's sort of one of my ways into a lot of these questions. Over the years, Emily's kept getting questions from parents
And recently, she's been hearing a lot about one particular concern. Tonight, growing questions about whether fluoride in drinking water is doing more harm than good. The incoming administration will advise all U.S. water systems to stop adding fluoride to their water supplies. Florida is set to become the second state in the nation to ban fluoride in water.
A couple of years ago, this started surfacing more and more frequently. And the questions people were asking me, you know, I'm hearing fluoride is dangerous. How do I understand this? And so I've sort of kept updating my writing on this as it has become obviously now a very big topic of discussion. Very exciting. Everyone is an expert on water fluoride. Worse, I just found out there's literally hydrogen in our water. Yeah, we're drinking this.
This is why I wanted to talk to Emily. Because most of what I've been hearing about fluoride has sounded pretty extreme.
On one side, you've got the fluoride haters. Fluoride science is completely made up. It's literally insane. Allowed to stand because our governments are completely corrupt. You do not need fluoride treatments. They are poison. On the other side, you've got the people that think the haters are just ridiculous. Fluoride has been subject to a public health smear campaign.
and mass hysteria. This conspiracy started in the 40s because people thought they were putting fluoride in the water to turn us all into communists. So no, water fluoridation in the U.S. does not make you dumber. On either side of this fluoride debate, you have people just yelling at each other with complete certainty. Dude, it's like, that's not helping.
And then there's Emily. I fundamentally believe that people are smart enough to work through understanding evidence. And the thing we're doing now is not working. I'm Noam Hassenfeld. And today on Unexplainable, the bitter struggle over an unassuming chemical. How can we get on the same page about fluoride? ♪
In 1901, a dentist in Colorado noticed this strange brown stain on a bunch of his patients' teeth. Over time, he realized their teeth weren't just stained. They were healthier. People with these weird stains had way less tooth decay. They even had fewer missing teeth. Eventually, scientists realized this was happening because this part of Colorado had unusually high levels of fluoride in the water. They realized that high levels of fluoride-stained teeth
But they wondered whether lower levels might still help with tooth decay. So they did an experiment. This is Grand Rapids, Michigan, a town becoming widely known to dentists and municipal authorities for its fight against tooth decay. It started in the 40s when officials added just a bit of fluoride to the water, way less than what was in the water in Colorado. Only excessive amounts of fluoride can cause mottling of teeth. And then they waited.
After six years of fluoridation, the study shows that the six-year-old children who drank the water from birth had 65% less tooth decay. Pretty soon, other cities were getting their own experiments. Studies in Newburgh, New York, Sheboygan, Wisconsin, Marshall, Texas, and other cities show substantially the same results as those obtained at Grand Rapids.
Within a few years, the difference started to become pretty clear. "Something has happened to the teeth of young children. Something that today is almost a dental miracle. Children's teeth just don't have as many cavities anymore."
When Emily started reading and writing about fluoride, she started hearing stories like this from her family. My aunt wrote to me and was like, I know fluoride is important for teeth because my teeth are terrible and your father's teeth are even worse, but my kids' teeth are great. And so, you know, at some point between when my father was a kid and when I was a kid, they started adding fluoride to the water. Emily's family tooth stories were a couple of interesting data points, sure, but...
Obviously not enough to prove that adding fluoride to water is worth it or that it doesn't come with downsides. So she read every study she could find, all to get at this question. Has fluoride actually been good for us? And just how good? So there is a lot of evidence of the impact of fluoride on tooth decay, like fluoride treatments. So that's like a thing you can randomize.
access to. And there is also some evidence from early municipal water fluoride introduction that introducing fluoride reduced the risk of cavities in kids. There is also some evidence on the flip side. So Israel pulled fluoride out of the water, and there is a little bit of evidence from there suggesting that the rate of cavities went up over time. I think what we don't have is something where we could be like, this is exactly the size of the impact of
there would be if we pull fluoride out of water. But there's also a huge amount of evidence that like fluoride is good for teeth. So we know fluoride is good for our teeth, prevents tooth decay. What do we know about the downsides? So at high dose levels, fluoride can be problematic for developing brains for kids or for exposure during pregnancy. The studies from which we conclude that
almost exclusively come from places where there are very high levels of fluoride naturally occurring in the water. Like there are areas of China and India in particular where the groundwater supplies have very high levels of fluoride, you know, maybe five or six times as high as what you would see in a municipal water supply.
system in the U.S. And there you see that, you know, moving from like four fluoride units to five does seem like it may have some small negative impacts on development in kids. And so that's kind of the piece of evidence that makes people concerned about fluoride, that at these higher levels, it has these impacts on basically on IQ and other neurodevelopmental metrics. If I'm being honest, when I first read about Emily taking fluoride concerns seriously, I
I was a little surprised. Like, most of the things I'd read were pretty quick to just say, fluoride good. All those potential downsides are just a conspiracy.
Which is not at all what Emily was saying. Yeah. Do we have any idea of how big an impact it has on IQ? It's, you know, a half a point of IQ per like unit of fluoride at these higher levels. It's a little bit of a hard number to look at. But I guess what I would say is like small but significant impact. But still an impact. But still an impact. Absolutely. Yeah. A small but still an impact. Yeah.
So is that to say that at low levels of fluoride in the water...
we notice no harmful effects, and then at high levels, we start to see some effects? Yeah. So that's basically, if you sort of take all of these studies together, of which I want to be clear, there are many. So there are many, many studies over the relationship between fluoride and IQ, some of which are run in places with very high fluoride, some of which are run in places with very low fluoride. If you kind of aggregate those and sort of take like a meta-analysis, which takes all of those together and you organize them, it is the dose that makes...
the poison, but at lower levels, you are not seeing those negative effects while you are getting these positive effects on teeth.
When I was doing some background research for this episode, I did find a few studies that seemed to disagree with Emily that showed fluoride could have negative effects even at low levels, like the levels in American water systems. Yeah, so it's like a very tricky space because there are many, many studies. Many of them are very small. None of them are like the gold standard randomized control trial study.
Emily says there are some specific issues with these studies. Like, for one thing, a lot of them measured the fluoride levels in people's urine, which is a problem because those levels can be impacted by someone's general diet, not just how much fluoride they're getting from the water. And then on top of that, you have the issue that, you know, there's 40 studies of something and people would be like, but what about this one study? You're like, yeah, that's what statistics are. Like, there's a distribution of effects here.
There's still some scientific debate on this, but when Emily looks at the big picture of all the studies out there, the vast majority show that low levels of fluoride are safe. I mean, I think the basic message is that municipal water levels in the U.S. do not have fluoride at levels you would be concerned about. There are a few places in the U.S. where fluoride levels do seem to be too high.
But according to recent numbers from the CDC, that applies to just 0.01% of the population. When you look at large-scale testing data, it does not look like we are seeing a lot of places that are at higher levels. So when parents have come to Emily with questions about fluoride in the water and they're pushing for an answer, she basically just tells them... You should just consume the water and not think about this question anymore.
Other people have landed in a different place. Even if there are issues with those smaller studies, they say they're worth paying attention to. And Emily gets that not everyone is going to agree on this, even if they look at the same exact data. It's a similar place to where she lands in her book on pregnancy. She writes about friends who read the same data she did and still decided to give up coffee, even if Emily didn't think a cup of coffee was worth worrying about.
Some people might just have a really low tolerance for risk. They might think any amount of uncertainty is too much. It's not crazy to say I'm worried about levels of fluoride because at some level you should be worried.
But I try to be sort of careful in this information to sort of say, like, there's absolutely nothing that should make you concerned about neurodevelopmental effects of the water fluoride that you see. Does that mean that some people will not choose to, like, drink a lot of bottled water or drink some other alternative? No.
And really the way we need to communicate that is to help people understand, yes, you know, here's why that concern is coming up, but here's why it may not be relevant to the situation you're in. One of the things I say all the time is like no option is completely safe. You know, so I don't want you to come to me and say like, you know, I'm not going to drink the water with fluoride. So my new plan is to go to this like stream out in the mountains and get my water from there. It's like, you know, that's got paradoxes.
parasites in it. That's got like giardia. Like you're going to be very sick if you use that. And that's actually much worse. And so just making sure that, you know, people have thought about the potential downsides of the alternative also. Maybe you're going to get in a car crash on the way to the stream. Yeah. I think the stream itself is much more risky. Don't drink out of the stream. Right. OK. That's the message for the episode. Do not drink out of the stream. Animals pooped in that.
It's not just fluoride, though. It can feel hard to talk about all kinds of things in public health right now. So what can we do to get back on the same page? Emily's got some ideas in a minute. Support for the show comes from Koala.
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You need to sit down.
You do not tell me when to sit down! Rolling Stone declares adolescence is soul-shaking television. For your Emmy consideration, Outstanding Limited Series. Okay, it's time to talk about RFK Jr. I think fluoride is a poison.
This is the guy behind the renewed push to get fluoride out of the water. The guy who's now in charge of America's health and science agencies. The same guy who's promoted all kinds of conspiracy theories. Like how 5G is a sinister plot to rule the world. They're putting in 5G.
to harvest our data and control our behavior. Or how HIV doesn't cause AIDS. 100% of the people who died in the first thousand who had AIDS were people who were addicted to poppers. Or how antidepressants are the reason we have so many school shootings. There's a tremendous circumstantial evidence that SSRIs and benzos and other drugs are doing this. The fact that this is the guy raising the alarm about fluoride
It's a big reason why it can feel so easy to write it off. Why a lot of public health experts might just wave away fluoride concerns without really getting into the details. This is fringe science. So what the health secretary is doing is smoke and mirrors.
Emily can't stand this kind of almost flippant response. I think that's a mistake in the way that we communicate. And the RFK case is a good one where, you know, he makes many claims and some of those claims, I think, are more defensible than others. You know, so RFK thinks it's fine to drink raw milk.
you know, like raw milk is more likely to make you sick than pasteurized milk, but the risks of raw milk are small. And I think that we will sometimes sort of give people the impression like only a crazy conspiracy theorist would, you know, buy into this raw milk,
And if you're doing that, then, you know, you're a looney tune. I think that kind of communication, which comes up a lot, is not helpful because it doesn't meet people where they are and help them understand why you hold the views that you hold. And then I think it pushes them away on topics where we really should be communicating. Like, we are really sure that people
this is something you should do. And so in the case of fluoride, to just say, you know, concerns about fluoride are a conspiracy theory writ large is not helpful because if people look into it, they're not really going to find that that's right. Yeah, if you say the whole fluoride thing is a conspiracy and then people find a reasonable study that says there are actual downsides to fluoride at higher levels...
It really does make it seem like a conspiracy. Exactly right. And if you are so dogmatic and you never allow for the possibility any information is counter to what you're saying, then as soon as someone sees some piece of information like that, you're going to lose them. And then it's very hard to get them back. Once you have lost someone's trust, it's very hard to rebuild. So would you say that public health officials should be honest about the downsides of fluoride and then let people make their own decisions? Is that the strategy you're advocating?
I would advocate a strategy of honesty, yes. I mean, I tend to be an over-communicator, but I do think that we probably under-communicate some of the nuance in the public health messaging that we send. It's obviously a tricky question, in part because the public health community right now is RFK Jr. Yeah. So that makes it more difficult to talk about this question of what should public health say? Yeah, it is really hard because...
You see RFK really casting doubt on vaccines. And we got a measles outbreak happening right now, which is very different from... Very different. Slight levels of tooth decay. And I don't know, I can see the feeling of wanting to just...
tell people what to do, which makes me wonder, I guess, do you think we can handle uncertainty? I do. I think people are not good at risks. Nobody's good at risk, no matter how smart you are. This is like, people are not good at risks. But I fundamentally believe that people are smart enough to work through understanding some of this evidence. And I think it's disrespectful not to give them that grace to try to
Because I don't think we're helping ourselves by telling people what to do. The thing we're doing now is not working. So if you sort of said like, look, we as the public health authorities are going to decide, you know, fluoride is good. Measles vaccine is good. Raw milk is bad. And everyone's going to do exactly what we say.
I mean, like those are positions I'm aligned with. But the reality is you go and do that. And then what happens is people don't trust you. And then you've like lost their trust on the raw milk. And then you lose their trust on the measles vaccine. And then now they're not doing any of those things. And if the only solution to that is then to yell that advice louder, like, but really, it's like that's not helping. They're not listening and they're not believing you. And so I just don't think the system is working.
I find this persuasive, but I don't know. I can get distracted. People can get distracted. I often come back to this poll from like 10 years ago that said something like one in four Americans think the sun goes around the earth. Okay. And...
I don't know, maybe that might make us lean towards wanting to tell people what to do and not work through the data for themselves. Okay, that's a fair point. But let me tell you, like, I've built an entire career on the idea that, like, people can understand graphs more than we thought they did. Yeah. But I think that the difference between these questions and whether the sun goes around the earth is, like, it doesn't matter for my life which thing goes around which thing.
It's not that it wouldn't matter if it were reversed for the physics of the universe, but for my day-to-day life, it's not important. Whereas it is important, a choice I do have to make is like, do I drink this kind of water or do I get my kid vaccinated or whatever these things are? I think people are more willing to engage on things that matter to them and more willing to think about them. We always take these examples like, oh, nobody can understand anything because they don't understand this basic thing about physics. Right.
But why would they think about that? It's like saying, like, people don't know what a sine or a cosine is. It's fair. I'd be like, oh, no, didn't you go to seventh grade? Didn't you get, like, learn trigonometry? I bet you wouldn't draw them for me. But the thing is, it doesn't come up. Okay. I mean, totally fair.
On the flip side, has acknowledging uncertainty in public health ever backfired? Like they laid out the data for everyone in the public, just made some really bad decisions? Yeah, I'm sure the answer to that is yes. And, you know, I don't know if I have a specific example, but I think it's absolutely right that there are settings in which
at a minimum, I think we should lead with here is the recommendation. And maybe that's sort of a different way to say this is like, I wouldn't lead a discussion of the measles vaccine by saying, let me start by laying out every piece of information we have about that. I think we have to lead the discussion with the best way to protect your kids and your family and the rest of everybody from measles is vaccination. And we know it is safe and effective.
Bottom line. But then the question is like, what do you say in response to people who are uncertain? And I think that's actually the tough thing about the communication here is it really does have to be kind of
titrated to the person that you're talking to. I mean, this is why like pediatricians are the best at this kind of stuff because they are one-on-one with a person right in front of them and they can feel, you know, somebody is just like, this is the thing. They're like, fine, you know, I don't want to hear any more about why. And then sometimes people need more of the why. And I think what's hard about the communication, I kind of err one way. I think other people would err it
Another way is, you know, how much do you lean into the assumption most people just want to be told what to do versus most people want a, like, pedantic 3,500-word explanation. Yeah. I mean, I think about what happened, I guess, five years ago now when Fauci's on the news at the beginning of the pandemic trying to tell people what to do. And...
There's a lot of stuff that we're learning. He's trying to balance this collective action problem of getting people to do things that are important while also not being sure how much uncertainty to communicate. Would it have been better, more responsible to lean into the uncertainty? I think it would have. I mean, I think one way to sort of organize this a little bit is like the value of leaning into uncertainty and communicating that to people is highest when the uncertainty is highest.
highest. When we were doing this communication in COVID, there was a lot of uncertainty and they knew there was a lot of uncertainty. And I think the mistake there was to convey so little uncertainty in a moment when there was so much. And so then what happened is every day you were learning that what they said yesterday was not right. There were sort of many stages of this where communicating uncertainty would, I think, have really benefited because
the certainty was sort of eroded almost immediately. Let's say we're three years down the line and there's a new head of the health agencies that's not a conspiracy theorist. What kind of message do you think that person should give to the American public that, I guess, deals with uncertainty responsibly and also allows us to have the trust in science that we should have? I think the main thing I would say, if that person asked me for advice, it would be,
ask people what their questions are and then try to engage those questions directly. Rather than assuming you know what their questions are or just assuming that you're going to tell them what to do, figure out what they are concerned about because it is not always the thing that you think.
and then try to directly address those questions in an honest way. Is there an example of a question that you're thinking of that someone might have a different underlying motivation? I mean, I think in the space of vaccines, the set of questions that people have, you know, do vaccines cause autism? Why are there so many vaccines? You know, why do we need this particular vaccine? Why do we need the hepatitis B vaccine at birth? I think that is one where it's actually very simple to explain the answer to that question. But
Instead of explaining the answer to that question, often we're just like, well, that's what's recommended. It's on the vaccine schedule. Like we put it on the vaccine schedule. And actually people would do better to explain why we have that and what are the potential other options if people are not comfortable with that. And then you think that would lead people to feel, I don't know, like they're having more agency, like they understand how the decisions are being made. Maybe they feel part of the decisions. That would be the hope. And it doesn't seem like you feel very hopeful. I'm not very hopeful. Sorry. Yeah.
Yeah. The truth is that, like, I was very frustrated during the pandemic with the messaging of the sort of public health officials. I'm frustrated with where we are now. I do wonder if we get a different administration in three years, whether that administration will have learned from the mistakes of the past. I don't think this is like an impossible thing to reset. And so maybe maybe we'll get to some kind of balance. OK, so that seems maybe a little maybe hopeful. OK, a little hope. I'll leave you a little hope.
This episode was produced by me, Noam Hassenfeld. We had editing from Julia Longoria, sound design from Christian Ayala, music from me, and fact-checking from Melissa Hirsch. Meredith Hodnot runs the show, Jorge Just is our editorial director, and Bird Pinkerton bent over to pick up the second note. Again, it was from Aaron Bird. High noon, the abandoned runway at JFK. Come alone.
Thanks as always to Brian Resnick for co-creating the show. And if you have thoughts about the show, send us an email. We're at unexplainable at vox.com. You can also leave us a review or a rating wherever you listen. Really helps us find new listeners.
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