In the 1940s, the United States became the first country to add controlled amounts of fluoride to the public water supply. Over the years, this decision to dose everyone in America with controlled amounts of a calcifying mineral has made people increasingly skeptical. In fact, some folks are downright terrified.

If you’ve dipped a toe into the debate around water fluoridation, it might be tempting to dismiss the controversy as another flare of pseudo-scientist opposition to incontrovertibly safe public health practice. Much like the folks that fight vaccination and fortified foods, the anti-flourdators are easily dismissed as a bunch of crazies riding the hot mess express. And surely, the loudest voices against putting fluoride in public water spout more outrage than reputable evidence. But a deeper dive into the question of whether water fluoridation should be allowed as a matter of public health reveals a more nuanced debate than simple conspiracy.

What’s Up with Fluoridated Water?

Fluoride is a naturally occurring mineral existing in many water sources. Like all substances, in extreme excess, it can be toxic. But, at the right concentration, consistent exposure to fluoride is an effective way to prevent dental cavities. This occurs because the mineral is particularly effective at reducing demineralization and increasing remineralization in tooth enamel. Since the U.S. started dosing kids with fluoride from public water supplies, we’ve seen an astounding 68% decline in cavity-related decayed or missing teeth between 1966 and 1994. The CDC named community water fluoridation as one of the ten great public health achievements of the 20th century, and today more than 75% of Americans drink publicly fluoridated water.

The success of America’s water fluoridation campaign has inspired followers, and many other countries now fluoridate their water supplies. About 372 million people in 24 countries receive artificially fluoridated water, including in the United States, Canada, Australia, Ireland, Brazil, and Vietnam. These governments advocate for water fluoridation as the best way to promote oral health for all.

But despite its demonstrated dental health benefits, water fluoridation is not universally accepted. Nearly 98% of European countries have refused to fluoridate drinking water, relying instead on fluoridated salt and milk. Likewise, less than 1% of Japan practices water fluoridation, as the practice is unnecessary given that most children perform fluoride mouth-rinsing in school. This raises the question of whether water fluoridation is necessary at all — and a careful analysis of the risks raises questions about whether the practice is really as safe as it seems.

Is Water Fluoridation Safe?

Beyond some public hysteria, there is no evidence indicating that fluoride is a neurotoxin. Likewise, claims of cancer and lower IQs associated with fluoride ingestion are largely unsubstantiated. In fact, the scientifically-backed hazards of too much fluoride are pretty limited.

Too much fluoride can cause fluorosis, which results in faint white lines or patches on the surface of the teeth. However, although these cases are extreme and rare, advanced stages of excessive fluoride ingestion can cause dental and skeletal fluorosis that makes teeth and bones brittle, causing pain and weakness. Physical pain from over-fluoridation is rare, but not unheard of. At least 20 states in India have been forced to deal with widespread outbreaks of both skeletal and dental fluorosis, requiring installation of fluoride removal plants. However, when measured against the potential agony of chronic dental pain for those with fluoride deficiencies, it’s hard to say which is worse.

Universal Water Fluoridation is Bad Policy

Despite clear benefits in certain areas where dental healthcare is lacking, clearly community water fluoridation is not a smart option in every place. First of all, whether fluoride is needed to prevent cavities varies based on the natural mineral content of water supplies and public healthcare realities. These natural variations, combined with the forces of public outrage fueled by social media, cause vast diversity in global water fluoridation. And frankly, the jury is still out on which perspective is the most accurate.

The World Health Organization recently stated that fluoridation at the correct level is hugely important, particularly for high-risk communities, while the European Commission sees no advantage to water fluoridation compared with other sources. These entities are looking at different data sets around water content, community oral health standards, and the availability of universal dental care, so clearly they will come to different conclusions. But the singular conclusion that can be drawn from this great diversity of data is that universal water fluoridation is at best unnecessary, and at worse potentially hazardous to public health.

How Much Fluoride is Too Much Fluoride?

Although medical consensus deems fluoride safe and effective for promoting oral health at the right levels, there are some gaps in the available data that opponents have latched onto. Those who fight fluoridation argue governments shouldn’t be making choices regarding the contents of a public resource that is both free and necessary for human life. Individual rights and informed consent for our own healthcare decisions weigh heavily in this debate, play heavy across the board, but some opposition arguments are more farfetched than others. Conspiracy theories involving communist plotting, forced sedation, and Nazism lack any real merit, but fluorosis is nevertheless a real consequence of over-fluoridation.

As with any good debate, there are zealots on both sides. But the true risks associated with public water fluoridation are perhaps less dire than many imagine. On one end of the spectrum, we have dental health and cavity-prevention. On the other side, we have the aesthetic risk of fluorosis and privacy rights. In the middle lie the many variables that influence whether water fluoridation is actually a good idea in a given place. Regardless, whether and how much to fluoridate public water sources is a highly fact-specific inquiry that requires decision-makers to consider the natural makeup of existing water supplies, the oral healthcare realities for their particular constituents, and the way that interest in individual rights balances against an imperative for government dental intervention. Given this highly circumstantial scenario, it’s hard to convince people that universal water fluoridation is really a good idea.