Vox
  • 9 hours ago
Should fluoride be in our water?
Transcript
00:00This is the New York City tap water that I drink, and for every liter of it, there is
00:060.8 milligrams of fluoride in it.
00:10Fluoride is essential for our oral health.
00:12It protects us from cavities, which is why it's also in lots of toothpaste and mouthwash
00:16and in treatments we get at the dentist.
00:19And for about 63% of Americans, it's also why it's in our drinking water.
00:26Now someone with a lot of views on public health not supported by science is being considered
00:31to lead one of the country's top public health agencies.
00:35And one thing he believes is that we should advise all U.S. water systems to remove fluoride
00:40from public water.
00:42Putting fluoride in the water has long fueled conspiracy theories.
00:46But it turns out the science is still evolving.
00:49And some of it emerged even as we made this video.
00:52And it's causing some scientists to take another look at this practice and wonder,
00:56do we still need fluoride in our water?
00:59And if so, how much is safe?
01:07Fluoride protects us from cavities by remineralizing enamel on our teeth.
01:12It acts as a protective barrier against the acid that bacteria in our mouths produce.
01:17When we drink fluoride in water, about half of it sticks around in our bodies.
01:22Some of it binds to our bones, and some reaches our teeth through our saliva.
01:27Fluoride occurs naturally in soil and air, and some regions have naturally occurring
01:31fluoride levels in their water.
01:34Almost 100 years ago, dentists figured out that high naturally occurring levels of fluoride
01:38in the water was staining children's teeth.
01:41But it was also preventing tooth decay.
01:44In 1945, Grand Rapids, Michigan and Newburgh, New York were among the first communities
01:48to start fluoridating water artificially.
01:51In Grand Rapids, researchers monitored roughly 30,000 schoolchildren over 15 years and observed
01:57that the rate of tooth decay declined by more than 60%.
02:01So other communities started adopting the practice, too.
02:05And eventually, it got added to toothpaste, which works topically.
02:10The goal of adding it to water was to make sure that everyone had access to fluoride's
02:14protection, regardless of whether they used fluoridated products or had access to dental
02:18care.
02:20One way to figure out how well the fluoride in our water is still working is to look at
02:24what happens in communities who have stopped adding it.
02:27Supporters of water fluoridation point to studies like this one, that looked at what
02:31happened in Calgary, Canada after they stopped fluoridating their water in 2011.
02:36The rate of tooth decay in children's baby teeth was already on the rise, but after they
02:40took the fluoride out of the water, that rate spiked.
02:45And this 2024 review looked across 21 studies of communities that added fluoride to their
02:51water and could only determine that it may have led to a slight reduction in tooth decay.
02:57The study authors found that prior to 1975, there was a clear and important effect on
03:01prevention of tooth decay in children due to water fluoridation.
03:05But because of the increased availability of fluoride in toothpaste since then, it is
03:09unlikely that we will see this effect in all populations today.
03:14So fluoride in the water did help us have healthier teeth in the past, and it still
03:18might in some communities.
03:20But because of how widespread topical fluoride is, the effect might not be as dramatic as
03:25it was historically.
03:27And in recent years, a handful of scientists have been looking into another question.
03:31How much fluoride is safe?
03:34Fluoride as an additive to water is usually in the form of liquid fluorosilicic acid,
03:38and the World Health Organization recommends a dosage no higher than 1.5 milligrams per
03:43liter of water.
03:45To put that in perspective, that's about one gallon for an Olympic swimming pool amount
03:49of water.
03:52The CDC recommends 0.7 milligrams per liter of water, or a little less than a half gallon
03:57per swimming pool.
03:58Municipalities set their own fluoride doses, and most set it around this amount, like my
04:03New York City tap water.
04:05This CDC recommendation is solely based on an amount that balances the protection from
04:09tooth decay while limiting the risk of dental fluorosis, the mostly harmless teeth staining
04:15first observed in communities with high natural fluoridation.
04:18But scientists studying these dosages today are looking at how fluoride affects developing
04:23brains, both in utero and as young children, primarily by measuring IQ.
04:28What we've learned about the developing brain is it's probably one of the most sensitive
04:33indicators of toxicity, and so we typically begin there.
04:38Bruce Lamphere is a professor of health sciences at Simon Fraser University in Canada, and
04:43studies environmental neurotoxins like lead, pesticides, and mercury.
04:48Some of the first studies to show a link between fluoride intake and IQ were from villages
04:52in China with high natural amounts of fluoride, starting in 1989 through the 2000s.
04:57Some of them looked at children who grew up in a village where the water had high levels
05:02of fluoride and compared them to villages without high levels of fluoride.
05:07They measured levels as high as 2.3 gallons per swimming pool of water.
05:12These early studies had plenty of issues, but they did raise a big red flag.
05:16And what they found is comparing the high versus the low populations, they saw about
05:20a 7 IQ point difference.
05:22When it's that large, it's hard to sort of just dismiss.
05:26For the average person, a few points difference in IQ doesn't have a huge impact, and it might
05:30not even be measurable.
05:31The former director of the National Institute of Environmental Health Sciences explained
05:36this to me using lead as an example.
05:38You know, Laura, if you'd had less blood lead, maybe you'd have three more IQ points.
05:42You can't prove that in an individual, but you look at a population.
05:47And we know that if you shift the population's IQ, you have more people needing special services,
05:54you have fewer geniuses.
05:57The results of those early studies inspired some researchers to try and find out whether
06:01the neurological risk from high fluoride levels could also occur at lower levels, like
06:06the WHO maximum of 1.5 milligrams per liter, or even at the lower levels we fluoridate
06:11our water in the U.S.
06:15Over the years, some studies have found an association between IQ and lower fluoride
06:19levels.
06:20Some haven't, leaving scientists, particularly in the dental and epidemiological communities,
06:26divided on the issue.
06:30But while we were working on this video, U.S. federal scientists published a rigorous
06:34analysis of 74 of the studies on childhood IQ and fluoride.
06:39In it, a small number of high-quality studies from outside the U.S. found an association
06:44between lower IQ and water fluoride levels below 1.5 milligrams per liter.
06:50But the small number of studies meant that they weren't able to draw conclusions about
06:54the levels that we fluoridate water in the U.S.
06:57I called Bruce Lanphier back up to make sense of the results.
07:00Hello again.
07:01Hello.
07:02The meta-analysis is really a way to synthesize and quantify the high-quality studies and
07:08the low-quality studies and try to make sense of it, right?
07:12Because otherwise, what you're left with is, well, these studies, which are my favorite
07:17studies, said this, and that confirms my belief, and these studies, which did that, don't confirm
07:24my belief, and clearly they're wrong.
07:27What this new meta-analysis was able to conclude is that urinary fluoride levels below 1.5
07:33milligrams per liter were associated with lower IQ, translating to a loss of 1.6 IQ
07:39points per one milligram per liter of fluoride in urine.
07:43Urine, which captures the totality of exposure that people have, and that's how we measure
07:49risk from total exposure, not from one isolated source.
07:54Bruce explained that the fluoride we put in our water is just the minimum amount of
07:57fluoride we all consume.
07:59Black and green tea leaves have high fluoride content.
08:02A variety of food, like potatoes and canned shellfish, has fluoride in it.
08:06The pesticides on our food can have fluoride in it, too.
08:09We consume fluoride if we accidentally swallow toothpaste or mouthwash.
08:13And the levels of fluoride we add to water also doesn't capture the roughly 3 million
08:17Americans, primarily in the Southwest, that use groundwater that has natural fluoride
08:22concentrations even higher than 1.5 milligrams per liter.
08:27Experts were particularly concerned about infants who drink formula.
08:30Almost their entire diet is fluoridated water and dry formula that can have fluoride in
08:34it, too.
08:35And about pregnant people who can pass all of this fluoride intake to a fetus.
08:39We oftentimes see exposures that exceed 1.5, and in some cases in pregnant women during
08:46the third trimester, we saw levels much higher.
08:52So what do we make of all of this information?
08:54First of all, topical fluoride is essential for keeping our teeth healthy.
08:58And for non-pregnant adults, there is no evidence that ingesting fluoride is harmful.
09:03There is some evidence that pregnant people, babies, and young children should be aware
09:07of their overall fluoride intake.
09:09Right now, we could be encouraging pregnant women to drink bottled water if their tap
09:16water is fluoridated.
09:18And we could be encouraging women who are using formula to feed their babies to make
09:23it with water that doesn't have fluoride on it.
09:26But if we're trying to figure out whether we still need to keep fluoridating our water,
09:30or whether it's safe to do so as is, the science still isn't conclusive.
09:35So it's a confusing time for understanding these risks and benefits.
09:40I am a believer in the precautionary principle, which does not say you act in the absence
09:46of evidence.
09:47It says you act in the presence of concerning evidence.
09:51And my reading of the literature is that there is enough data to say there is concern.