What are the benefits of fluoride for public health?
There's been overwhelming evidence that shows that in communities where fluoride is added to the water, the occurrence of dental caries – which is the most common disease and also preventable – is significantly less.
When you look at a U.S. map and compare the percent of people who receive water treated with fluoride compared to those without added fluoride, then overlay that map with one showing the incidence rate of dental caries or cavities, it directly overlaps.
Is it about finding the correct dosage for the proven benefits of fluoride?
When you think about overall health and risk due to exposure, you look for a dose-response. It’s about balance. For fluoride, we see that at no exposure or very low levels, you have the issue of increased risk for dental caries and oral health issues. But at low levels of fluoride similar to what is added to public water supplies, then dental caries are reduced, and oral health is improved.
What is the recommended limit for fluoride in drinking water in the U.S.?
The CDC currently recommends 0.7 parts per million (ppm). They feel that 0.7 ppm is a way to be proactive. One, because you can still get that preventive aspect for oral health, and, two, you can address any potential associations or concerns related to systemic outcomes.
Which is important for children too, right?
With children, it's two factors. One, they're being exposed, and if they're being exposed at an elevated level, then that's going to have lifelong impacts. And, two, children have larger body surface area to volume than adults and are more susceptible to absorbing more contaminants.
Recently, there has been some news around fluoride and IQ for children. The hard part about IQ is you have to do a very good job assessing all individual factors – including prenatal exposures. Alcohol or other chemicals, trauma during pregnancy or delivery – these have all been associated with pediatric IQ. That would be my concern: Before you can really dive in and say that the fluoride levels in water are heavily or strongly associated with pediatric IQ, you have to account for all of those known attributable risks.
What are the dosage limits for fluoride? And what are those adverse effects?
Dose-response extends to higher amounts as well, of course. So where do we really start seeing impacts? What research has found is that chronic exposure over 1.5 parts per million (ppm) of fluoride of water is associated with adverse health outcomes. The Environmental Protection Agency’s maximum contaminant level is 4.0 parts per million – and I think that’s where public concerns arise.
But public water treatment facilities don’t put nearly that much in. The maximum is 1.0 ppm and as I mentioned, the current CDC recommendation is 0.7 ppm.
Once you get above that research-identified point of 1.5 parts per million of fluoride in water, then there is a risk for systemic impacts, especially on the skeletal system leading to skeletal fluorosis or weakening of the bones. There’s been other studies that have looked at the impacts on the cardiovascular system and neuro cognition. But again, that’s at exposures and dosages much higher than what’s being added in public water systems.
So you're balancing two different factors with this. On one end, there’s an inherent benefit we’ve seen since this approach began 76 years ago in the U.S. for improving oral health. On the flip side, people who have well water don't have access to that, but are at risk for naturally occurring fluoride at elevated levels.
Because a large portion of the U.S. population is on well water, correct?
Yes. Nearly 15% of the U.S. population is on well water, and so they don't have added fluoride. However, there are locations across the U.S. that have fluoride that occurs naturally, sometimes at elevated levels.
What about at home here in Colorado – do our fluoride levels vary?
It does vary. The Ogallala Aquifer is one that's known to have elevated levels. So, you'll see that especially in north and western Texas, Oklahoma, eastern Colorado, northeastern part of New Mexico. There are certain areas in the San Luis Valley that have detectable levels. With my work in Colorado, I would be focusing more on heavy metals such as arsenic and uranium, which do not have benefits and are toxic. Colorado’s geography and geology is so varied across the different geological zones that exposure to various natural elements occurs in water.
In your view as someone who's been in this field for your whole career, why has fluoride become such a public health flashpoint?
One is that this is a large-scale public health intervention where people can feel like they do not have autonomy to make the decision. People can feel skepticism when the decision is being made for them, a public health challenge we have seen more of since COVID. In comparison, with the recent discussions around new evidence suggesting a correlation between cancer risk and alcohol consumption, you’re not seeing calls for it to be taken off the shelves, because people can choose to not drink or to drink and take that risk.
Second, I think people want absolute certainty when they don't have decision-making power, which is challenging, because everything is going to have some degree of uncertainty.
And third, I feel there’s a current cultural trend in questioning things. Sometimes a healthy skepticism is good, but to a degree.
I think where everything gets really convoluted is the fact that we now have social media and the internet. So, information spreads quickly and isn’t vetted. It’s hard for research and science to match that timeline and dissemination of information. The crux becomes, how do we navigate public health interventions in a way that provides people with the information while still preserving the benefits for inclusivity for all? You want to avoid having a small number of people not want it – despite the evidence and efficacy – leading to the decision of nobody getting it. It’s a balance between autonomy and improving public health.
Is there a gap in understanding risks and probabilities that allows the misinformation about fluoride to continue?
You hit it right on the head at the end. My perspective is in the difficulty in communicating risk. When we disseminate study findings, we'll say there's a 5% increase in risk for X with Y exposure, but the context can get lost quickly when you translate that population-wise. If the risk for X in a population of 100 people is 1 and you increase it by 5%, that’s 1.05 people now.
But if you hear a 5% increase in risk, people can apply that to themselves individually – instead of a 20% chance I now have a 25% chance. And it doesn’t quite operate like that. So how we as researchers communicate risk is better to not set off alarm bells but facilitates people making an informed decision.
And when things get brought to an individual level, the major factor is genetics. You can have a 95-year-old who smoked half a pack of cigarettes a day and never got lung cancer; then you have the 25-year-old who smoked for five years and gets a rare respiratory cancer.
A greater appreciation and understanding of uncertainty is really needed. As researchers, we replicate studies and improve research to bring uncertainty levels down. Think about the example with cigarettes again – we have decades of data showing risks and negative health effects. More data will help get us there with filling in the blanks on fluoride, even if fluoride’s impacts really show across the lifespan and are less immediate compared to a shorter latency period for something like smoking or asbestos.
