An introduction to fluoride in water

Start here if you are:

  • New to the issue of fluoride in water
  • Looking for an overview or brief summary to bring you up to speed

Here is a video to introduce fluoride in water. It is about seven minutes long.

We have also split it into a number of shorter videos, each dealing with one part of the whole: after a general introduction we look at dental decay; next, how prevention is better than cure; then on to how to prevent dental decay; what is fluoride in water; how well fluoride in water works; some comments on safety; how fluoride in water is monitored and scrutinised; how popular it is; and finally, the politics.

These videos were written by R Lowry and are presented by P Davies.

Below is a written version of the introduction which compliments the videos and provides more details.

You may have heard of fluoride in water (otherwise known as water fluoridation, fluoridation of water). It is something to do with preventing tooth decay and it sometimes stirs up debate in the media. Let’s look at what it is in detail and hopefully you’ll be able to make your own mind up about the issue.

What we’ll cover: dental decay (what it is, how to prevent it); choosing what to do; and, in some detail, the facts on fluoride in water.

Dental decay: What it is

Teeth are covered in very hard enamel

Bacteria that live in the mouth can weaken it

They feed on sugars and produce acid which eats through enamel

Once a hole forms, it soon becomes a cavity that can injure or kill the tooth

What causes dental decay

Tooth decay needs bacteria to collect on the teeth, sugars to feed on and the enamel to be as weak as possible

How dental decay is treated

No treatment can return the tooth back to health

Decay can be cleaned out and the hole filled

A badly decayed tooth may need to be extracted

There are other more complicated treatments that can restore function: crowns, fillings, root canal therapy

Prevention is better than treatment – less expensive and less discomfort

How dental decay is prevented

In theory, tooth decay can be prevented by cleaning away bacteria, starving them of sugars (eating a healthy diet) or by making the enamel tougher

The problem: how much dental decay is there?

Dental decay is less common than in the past

Healthy children who have access to good diets, home mouth care and expert prevention have very little decay

Children who are underprivileged have most

People bear the scars of decay into adulthood and old age so it’s not just a disease of children

In the United Kingdom there are areas where people have many teeth that are decayed, and other areas where they don’t

If prevention of dental decay in individuals is better than treatment, prevention in areas where decay is rife makes even more sense

Prevention of dental decay

Toothbrushing: regular, good technique, with fluoride toothpaste

Diet: healthy, plenty of fresh fruit and vegetables, plenty to chew on, low sugar

Topical fluoride: teeth are bathed with concentrated fluoride by dental health professional on a regular basis

Fluoride in water strengthens tooth enamel in two ways:

Systemic (internally, by being swallowed)

Topical (the teeth are bathed in small quantities of fluoride)

Choosing what to do: matching method to problem; ethics

With all those choices, how do we choose which prevention to use? All of them? Some of them? Selected ones on certain occasions? Ideally, we might use them all in combination, but if we are to choose, what are the guiding principles?

These are the questions we ask when deciding: what works for individuals, groups and larger populations? For example, we might prefer it that everyone brushes their teeth conscientiously, eats a healthy diet, has regular dental check-ups and so on. But what do we do in the real world, when not everyone does everything we recommend? That’s where fluoride in water comes in.

We can fluoridate the water; but should we? Although it is technically possible, is it ethical to do it? What do we have to keep in mind when deciding?

Autonomy: The duty to respect and promote individuals´ choices for themselves in achieving what they believe to be in their best interests. This can be overridden to bring the most benefit to everyone.

Beneficence: The duty always to act in other people’s the best interests.

Non-maleficence: The duty to do no harm.

Distributive justice: All people are equal.

Fluoride in drinking water passes all these tests: it doesn’t rely on individual behaviour, it benefits everyone, it does no harm and it reduces inequalities. The other methods of prevention work in harmony with fluoride in water, but that’s the best we can do to start with.

Fluoride in water: what it is

Fluoride is a mineral that dissolves in water

Fluoride is naturally present in all drinking water to some extent

The more fluoride that dissolves in water, the higher the concentration. If drinking water is pumped up from wells dug into rocks with fluoride in them, the water will contain some fluoride dissolved in it

Fluoride can also be deliberately added to water

Fluoride in water is the same whether it occurs naturally or is added deliberately

For healthy teeth, only a minute amount of fluoride is needed in drinking water

Fluoride in water has no taste

To get drinking water that prevents tooth decay, we either pump up naturally fluoridated water from wells or add it at the water treatment plant

How fluoride gets in the water

Most drinking water is treated before it is sent out to the tap. At the treatment plant the water is filtered, purified, has chemicals added to remove solids and prevent bacterial growth, and may have fluoride added to help prevent tooth decay (see below for details of water treatment)

How fluoride works

Fluoride alters the structure of the developing enamel of young children so that it is resistant to dissolving with acid

Low levels of fluoride increase the ability of a tooth to repair the enamel (remineralisation)

Fluoride reduces the ability of mouth bacteria to form acid

How we monitor it

For many years the government has monitored the health aspects of fluoride in water. Scientists and health care professionals test drinking water throughout the system and the health of people drinking it


When fluoride in water was first discovered, decay was so common that it cut it by half for many people

Now decay is less common in most people/ only really bad in a few groups; the benefits are less noticeable unless you look closely at where decay is still a problem – there, dentists can still see how much fluoride in water works so big is the improvement.


The safety of fluoride in water is a top priority

We take extra care as it is not a cure (it is a preventive measure) and cannot be avoided

Fluoride in water is one of the most researched preventive measures we can take


Fluoride in water is so popular most people think it has been in all drinking water  at the right level for many years when it has not

Because it is obligatory (it works because it is unavoidable), we have regularly checked it is popular

Most people approve of fluoride in the water (we know this using top quality research methods); the small number of people who don’t like it has remained constant over the years.

Who gets fluoride in water at beneficial levels

Only 10% of the UK population has adequately-fluoridated water (2022)

The US Center for Disease Control have published their latest fluoridation statistics for 2018: 207.4 million residents were receiving fluoridated water or 73% of those on community water systems.

Worldwide coverage is now in excess of 400 million people.

The US Center for Disease Control names water fluoridation in its top ten of public health achievements of the 20th century

The legal side

Fluoridating the whole water supply doesn’t rely on individual action (for example to use fluoridated toothpaste or for a dentist to apply fluoride personally to individual teeth).

But the widespread nature of the intervention and its overriding of personal, individual civil liberties is, like similar interventions (for example the compulsory wearing of seat belts in cars), subject to the democratic process. Most fair-minded people accept this.

The democratic oversight of water fluoridation and the associated legal framework covers a number of issues:

The decision to fluoridate


The monitoring of safety and efficacy

The public health benefits

How the system is operated (for example, technical issues at the water treatment plants, levels of fluoride in the water and so on).

The politics

All shades of political opinion tend to have a view of fluoridation:

The political Left approves of it because it is egalitarian and benefits the most deprived preferentially; but can be against it because it treats the results of poverty, but doesn’t treat the causes (political). It is also paternalistic.

The political Right can be against it because it overrides personal choice (The Nanny State); but for it as it reduces dental bills.

A video that sums it all up

Talking fluoride in water: a short video in which enthusiasts discuss it.

Here is a short video produced by our American colleagues which is a comprehensive summary of fluoride in water

The chief medical officers of the United Kingdom recently released a supportive statement which contains a lot of useful information

There are many benefits of fluoridation; the general health aspects have been reassured through  extensive scrutiny and monitoring; it is popular and well supported both professionally and publicly; and it is above reproach ethically. The Americal Dental Association’s “Fluoridation Facts” offers additional information as a supplement to this website. Podcasts and ebooks are also available.

Please explore the website: our frequently asked questions section is useful if you have any queries. Our Key Issues section contains much of the evidence base for fluoridation with key references.


Drinking water comes from a source full of fish and filth, but ends up pure enough to beat bottled water in taste tests.

The water purification process starts with water that has accumulated in a reservoir, so when it arrives at the treatment plant, they first filter it. But The cloudy water contains microorganisms, trace chemicals and tiny particles of dirt that can’t be filtered out.

So next the water flows to the chemical treatment channels. Here it’s mixed with a cocktail of chemicals, the exact volume of which is determined by scientists who add aluminum sulphate, known as alum, which cleans the water using the principles of electrical attraction. The alum dissolves, breaking down into positive and negatively charged particles. Oppositely charged specs of dirt are attracted to the alum particles, causing the dirt to form clumps known as flocs. And when the flocs are heavy enough, they sink. Next are added chlorine to kill germs, and fluoride for our teeth. As they do, the flocs get bigger and bigger. The flock sediment sinks to the bottom and can be scraped out as muddy sludge, except for 0.1%. that last drop is removed in filter beds. The beds consist of 62 centimeters of finally graded sand, sitting on 30 centimeters of graded gravel. As the water passes through the sand and gravel that last 0.1% of impurities is filtered away.

That leaves the clean water to be pumped out to the consumer.