MARY LOUISE KELLY, HOST:
Most people in the U.S. get fluoridated drinking water. It's been the standard for nearly 80 years to help stop cavities, and it's considered a major achievement in public health because it has prevented a lot of cavities. A government report on high levels of fluoride and children's IQ is out today, though it is contributing to debate over the practice. The analysis behind the report is out today. Here to talk about it - NPR's Pien Huang. Hi, Pien.
PIEN HUANG, BYLINE: Hey, Mary Louise.
KELLY: Hey. What does the research actually show?
HUANG: OK. So the latest research, which is out today, is this paper in the medical journal JAMA Pediatrics. And it's by government scientists at the National Toxicology Program, which is part of the National Institutes of Health. What it does is that it looks at a few dozen studies that other people have conducted, mostly researchers in China and India, and it finds a link between high levels of fluoride and a small decrease in children's IQ. This is something that they say they have moderate confidence in. Now, this conclusion is not new. This is the research behind a government report that was actually published back in August.
KELLY: OK.
HUANG: But this research has actually already been quite influential in the debate over fluoride in drinking water.
KELLY: And this is something - am I right? - that Robert F. Kennedy Jr., Trump's pick to head Health and Human Services - something he has highlighted. He wants fluoride gone. Just to be crystal clear, the data does not say that fluoride in drinking water is harmful. Is that right?
HUANG: That's right, Mary Louise, on both of those counts. So the data does not say that fluoride in drinking water is harmful, at least not at the levels that are recommended in the U.S. drinking water supply. What it does show is the possibility of harms when the fluoride levels are more than twice what's recommended, and that does happen. You know, there are places where fluoride occurs naturally in the soil and groundwater, and people can get that higher exposure. In the U.S., that affects about 2 to 3 million people. But the analysis is still fueling this debate over the low levels of fluoride that are added to drinking water at much lower levels than that. And Steven Levy, a public health dentist at the University of Iowa, says that using this data for that debate is a stretch.
STEVEN LEVY: The major problem is that the science is not as strong as it is presented by these authors.
HUANG: You know, he says that they didn't really fully consider some more recent research that casts doubt on the links between fluoride exposure and IQ, and he says that because we're so used to water fluoridation, we take the benefits of it for granted.
KELLY: And, again, among those benefits, we know that fluoridated water prevents cavities. Are there reasonable questions to ask here, though?
HUANG: Yeah, there are, and the scientific debate is raising some of them. One of the questions centers around people's total fluoride intake. So besides drinking water, people can get fluoride from toothpaste, tea, foods like spinach and seafood. And the researchers for this paper are worried that these sources combined could be exposing people to some harmful levels. Another question people is raising is on the benefit side. So there was this other recent analysis that showed that while fluoride in water reduces cavities, it's less critical now than it used to be before fluoride in toothpaste became a regular thing. So there are some people saying it's time to reweigh the risks and benefits given how society has changed.
KELLY: So where does all this leave us? What's the next step?
HUANG: Yeah. So two things - the Environmental Protection Agency has this deadline coming up in the next two weeks over whether they should be appealing this recent court decision telling them to tighten their fluoride regulations. And then there's also Robert F. Kennedy Jr., as you mentioned earlier, Trump's nominee for health secretary. He told NPR that one of his priorities is to get the country to stop fluoridating the water. So we will see what happens.
KELLY: NPR's Pien Huang. Thank you.
HUANG: Thank you.
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