WILLIAM BRANGHAM: Earlier this month, Health and Human Services Secretary Robert F. Kennedy Jr. announced plans to end the federal recommendation that municipalities add fluoride to their drinking water.

The Environmental Protection Agency also said it was reviewing -- quote -- "new scientific information" about the risks of fluoridation.

Given this renewed debate, we wanted to hear one perspective from a community that did remove fluoride from its water, the Canadian city of Calgary.

Earlier this week, I spoke to Lindsay McLaren.

She's a professor of community health sciences at the University of Calgary.

And I began by asking her why we started fluoridating water in the first place.

LINDSAY MCLAREN, Professor of Community Health Sciences, University of Calgary: In regions of the United States and elsewhere, it was observed by local dentists -- this was back in the 1940s -- that people living in certain communities had kind of a staining of their teeth, and they -- but their teeth also turned out to be quite resistant to tooth decay.

And so it was determined, it was figured out that this was because of naturally high levels of fluoride in the drinking water.

And so that gave rise to the idea that we could actually do this intentionally and in a controlled manner as a public health intervention to improve the oral health of the population.

WILLIAM BRANGHAM: We mentioned that some people have cited risks associated with this practice.

And the current HHS secretary in the United States, RFK Jr., he had a recent visit to the state of Utah.

Utah itself became the first state to ban fluoride in its water.

Here's what he said there.

ROBERT F. KENNEDY JR., U.S. Health and Human Services Secretary: In the era of fluoridated toothpaste and mouthwashes, it makes no sense to have fluoride in our water.

The evidence against fluoride is overwhelming.

In animals, in animal models, and in human models, we know that it causes I.Q.

loss.

WILLIAM BRANGHAM: So, what about those arguments, one, that in the era of heavily fluoridated toothpaste, we don't need to add it to our water?

And, two, are there studies indicating that it causes I.Q.

loss?

LINDSAY MCLAREN: So the point about being in the era of widespread fluoride toothpaste is a good one.

But research and systematic reviews of research that have been conducted in this era consistently show that there is an added benefit of fluoridated water above and beyond the widespread use of toothpaste.

WILLIAM BRANGHAM: And then what about the studies that he cited about I.Q.

loss?

LINDSAY MCLAREN: The main thing to say there is that it's really not at all clear that fluoridation is associated with those outcomes at the levels that we're talking about for community water fluoridation.

There's many examples of things that are harmful or toxic at high levels, but that are innocuous or even beneficial at lower levels.

WILLIAM BRANGHAM: So, turning to your experience, in 2011, the Calgary City Council voted to remove fluoride from its water.

You launched a study then as to what the downstream impacts of that was.

What is it that you found?

LINDSAY MCLAREN: So we designed a large-scale study where we collected data on oral health and a number of other things from several thousand kids in both Calgary, where fluoridation was stopped, and in Edmonton, which is the other large city in Alberta, which has several similarities to Calgary, with the main difference being that they had fluoridation in place and it was continuing.

About seven to eight years after the decision to stop fluoridation in Calgary, we observed quite a big difference in the prevalence of tooth decay among kids in the two cities.

So the percent of kids who had tooth decay in Calgary, where there was no fluoride, was 65 percent, whereas, in Edmonton, where fluoridation remains in place, it was about 55 percent.

WILLIAM BRANGHAM: So, a decade later, voters there voted to put fluoride back into the water.

That has not happened yet.

So does your experience there help inform how Americans ought to be thinking about this decision?

LINDSAY MCLAREN: Certainly, in the Calgary case, we were fortunate to be able to build this study and to demonstrate that there are consequences to removing fluoride from drinking water.

It's not just an innocuous policy decision.

And so that information, I think, figured importantly in the decision to reintroduce the measure, which should be happening soon.

What I think I would also want to add here is that, if you decide as a community, if you have a kind of a grown-up conversation and decide as a community to not fluoridate the water, that is one thing, but you have to accompany that by a discussion about, what are you going to do instead?

Because tooth decay is not an innocuous health problem.

It's a serious health problem.

It's very common.

And, perhaps most importantly, it's almost entirely preventable.

And so what kind of a society are we if we don't prevent an entirely preventable problem that causes harm and pain to kids and to others?

So, sometimes, the discussion is quite incomplete.

It's just about fluoridation, but it's actually a bigger question around, how are we going to build sort of the public supports and resources that allow everyone to have good oral health and good general health?

WILLIAM BRANGHAM: All, right that is Professor Lindsay McLaren at the University of Calgary.

Thank you so much for your time.

LINDSAY MCLAREN: Thanks for having me.