Frequently Asked Questions on Fluoride and Water Fluoridation - Plain English

The FAQ Section is intended to be a live section and the FAQ’s are regularly reviewed and updated with new evidence as advised by the Expert body. The Expert Body continues to evaluate the current and emerging research with an emphasis on academically ‘high impact’ peer reviewed research publications or their equivalent.

This section was last updated 17th September 2020.

Fluoride comes from fluorine. Fluorine is a natural part of the Earth found in stones, soil, water, plants and animals. Fluoride is found in waters all over the world. In the sea, fluoride can be 1.2 to 1.4 ppm (mg/l). In Ireland, the natural background level of fluoride is low (0.2 mg/l.)

Fluoride level in water is measured by milligram per litre (mg/l) or parts per million (ppm), it is the same concentration. Fluoride level in water is measured by milligram per litre (mg/l) or parts per million (ppm). Both units can be used, and in this text when quoting other sources, we use the units as presented in that source, for e.g. the legislation refers to milligrams of fluoride per litre (mg/1) and the Forum on Fluoridation refers to parts per million (ppm).

Fluoride helps prevent and reverse the early signs of tooth decay. Fluoride is found in drinking water, most toothpastes and some mouthwashes.

It is adjusting the amount of fluoride in water supplies to stop tooth decay, which causes holes in the teeth.

Fluoride helps reduce tooth decay* and holes in the teeth.

*When we eat or drink something that contains sugar, acids are produced in the mouth by bacteria living in the dental plaque on the surface of the teeth. The acids start to break down the enamel surface of the tooth causing decay.

Fluoride works in two ways:

1) Before teeth appear in the mouth, fluoride helps make the tooth stronger.

2) After teeth appear in the mouth, fluoride reduces tooth decay.

Enamel covers and protects your teeth. It is the hardest substance in your body.

Sugar + Bacteria = Acid Attack on the tooth. This Acid dissolves the enamel of teeth causing tooth decay and holes in the teeth. Fluoride is a constant repair kit for teeth and help reverse tooth decay. Fluoride helps people of any age, by protecting their teeth.

Hydrofluosilicic acid (HFSA) is the product used for adding fluoride to water in Ireland. HFSA has no taste or smell when it is added to water.

No. The compounds most commonly used for fluoridating water react with water:

H2[SiF6] (HFSA) + 2H2O (water) → (gives) 6H+ (hydrogen ions) + SiO2 (sand) + 6F (fluoride)

This happens in 12 minutes, well before the water arrives at the person's tap. The hydrogen is removed, silica is already in the water and is harmless.

Thus, the person gets fluoride, not Hydrofluosilicic Acid (HFSA) or other fluorosilicates.

No.  It is sourced as a primary product; it comes from a raw material source as Calcium Fluoride.

On July 1st 2007, the level of fluoride in water supplies in Ireland was lowered to 0.6–0.8 ppm, which is the same as 0.6-0.8 milligrams fluoride/litre (mg/l), a level best for protecting the teeth of people of all ages. The EU law states that fluoride should not be any more than 1.5 milligrams fluoride /litre of drinking water. The Irish legal amount of 0.6-0.8ppm fluoride is therefore around half what the EU allows.

No, many countries have fluoride. This includes including Australia, Canada, New Zealand, Spain, the United Kingdom, and the United States. Adding fluoride to water is less common in Europe than adding fluoride to salt or milk, which is also common in parts of Asia and South America. In addition, some countries have a natural level of fluoride in water that can reduce tooth decay.

The Health Service Executive (HSE) is legally responsible for arranging the addition of fluoride to drinking water in public water supplies. However, Irish Water does this on behalf of the HSE.

The Irish Expert Body on Fluorides and Health continues to support a detailed Code of Practice on how to add fluoride to drinking water. This Code sets out how much fluoride is provided, stored.

Yes, according to the law, the amount of fluoride in drinking water is tested daily. The Health Service Executive, Environmental Health Officers also carry out testing on a monthly basis.

Irish law and European (EU) law tell us how much fluoride we can use.

Under Irish law, the level of fluoride must be between 0.6-0.8 mg/l (milligrams fluoride /litre). The EU law lays down that the level should not exceed 1.5 milligrams fluoride /litre of water. Irish law 0.6-0.8 mg/l fluoride is around half the amount that the EU allows.

The water is tested daily, if the amount of fluoride is too low or too high, the right amount of fluoride is added, and the water is tested again.

Irish Water sends a report to the Environmental Protection Agency on fluoride in drinking water and also writes an annual report on drinking water quality.

Modern diets are sugary. In Ireland, a lot of adults and children have sweets and fizzy drinks between meals, and many prepared foods have sugars added. Some ready-made meals can also be high in sugars. These sugary diets and snacking habits increase the risk of both children and adults developing tooth decay. Research suggests that the more frequently you consume sugary foods and drinks the greater your risk of developing tooth decay. Fluoride can reverse and protect the teeth from the damage done by sugar. So, to prevent tooth decay the best advice is to limit the frequency of sugar intake and protect your teeth with fluoride. Ireland adds fluoride to public drinking water supplies. This is known as community water fluoridation. Fluoride in the water helps protect the teeth from the damage done by consuming too much sugar. Water fluoridation gives everyone in society access to the amount of fluoride needed to strengthen their teeth and reduce the chances of having tooth decay.

Yes, in Ireland, having fluoride in both water and toothpaste is much better, especially for children. Children who drink fluoridated water and brush their teeth with a fluoride toothpaste have less tooth decay.

Most of the bottled waters for sale in Ireland do not contain the right amount (between 0.6 - 0.8mg/l) of fluoride for the prevention of tooth decay.

Yes, there is strong evidence to show that adding fluoride to water is effective in preventing tooth decay. The data shows that children living in fluoridated areas have fewer holes in their teeth than those who do not.

The best science to date shows that community water fluoridation with the Irish legal amount (0.6-0. 8ppm (mg/l)) of fluoride in the water does not cause ill health effects.

Many organisations including the World Health Organisation, support water fluoridation.

In 2015, the Health Research Board (HRB) found no scientific evidence that community water fluoridation was bad for health. Also, the Irish Expert Body on Fluorides and Health checks any new evidence or research and advises the Minister for Health whether there are any health problems associated with adding the fluoride to drinking water).


In 2011, the European Union reviewed all of the evidence. The main conclusions of the report are that there is no known human health concerns or risks to the planet, from adding fluoride to water at levels recommended for community water fluoridation in the EU.

Water fluoridation first began in the USA in 1945 and has been studied a lot. Studies show that water fluoridation at the recommended levels does not cause harm to health. Tooth fluorosis however may occur.

Tooth fluorosis causes white marks on the teeth or may make them look stained. At Ireland's level of fluoride, tooth fluorosis is very mild and, in most cases, can only be seen by a dentist. Also, not all white marks are caused by fluoride. In most cases, tooth fluorosis does not need treatment. If you are worried you can talk to your dentist about it.

At the fluoride levels in Ireland, there is no evidence of harm to health. Tooth fluorosis however may occur.

In 2015, The Health Research Board (HRB) looked at all water fluoridation studies published worldwide. They found no evidence of harm to health.

They advised that all new studies should continue to be reviewed. They advised that more good quality studies should be done. Likewise, a recent report from the US National Academy of Sciences have recommended that further analysis of the existing data be conducted into the effects of fluoride on human health.

All new research concerning health effects associated with CWF is kept under continual review by the Irish Expert Body on Fluorides and Health. If a serious concern is noted, the Minister for Health would be advised.

Yes, fluoridated tap water at the levels available in Ireland can be used to make up infant formula. As reported in the 2018 Food Safety Authority of Ireland (FSAI) Fluoride Total diet study [1], some infant formulas may contain very low levels of fluoride. The FSAI Scientific Committee, in agreement with a prior study regarding the fluoride content of infant formula made up with fluoridated tap water [2], decided that there was no scientific basis for concerns about the safety of children in Ireland from exposure to fluoride from foods. Fluoridated tap water in Ireland is set at between 0.6 ppm and 0.8ppm [3]. The Expert Body would like to make clear that there is no recommendation to stop using fluoridated tap water at current legal levels in Ireland. Where a person is unsure about what to do, ask a health professional such as a dentist, GP, public health nurse or paediatrician for advice.

[1] The Food Safety Authority of Ireland (2018) Total Diet Study 2014–2016: Assessment of dietary exposure to fluoride in adults and children in Ireland

[2] Anderson, W.A., Pratt, I., Ryan, M.R., Flynn, A. (2004) A probabilistic estimation of fluoride intake by infants up to the age of 4 months from infant formula reconstituted with tap water in the fluoridated regions of Ireland

[3] Fluoridation of Water Supplies Regulations 2007& (Statutory Instrument (S.I.) No. 42 of 2007)

ng fluoride to water is known to reduce tooth decay. A study called Fluoride and Caring for Children's Teeth (FACCT) carried out between 2014 and 2017 shows that children living in areas with fluoride added to water supplies have less tooth decay than those who do not. Stopping fluoride in water would lead to social costs such as pain and trauma, as well as time off from work or school and treating tooth decay would cost more money. The FACCT study recently conducted in Ireland found a benefit for community water fluoridation. One of the findings is that it is very good value for money

Water fluoridation has no impact on the acidity or pH of drinking water. It does not cause lead or copper to leach out of water pipes.

Raw and undiluted hydrofluosilicic acid is very corrosive. It is a strong acid but once added to drinking water, it dissociates, and it is no longer corrosive.

A lot of people think that water fluoridation is the right thing to do. It helps to stop you from getting holes in your teeth and does not cause problems except for slight white marks on the teeth in some people. Sometimes we need to do things to help others even if we do not agree with them ourselves. For example, during the COVID-19 pandemic wearing face masks was recommended so that we would protect others.

Fluoride in the water helps everybody especially people who get lots of holes in their teeth or who cannot afford to buy toothpaste or go to the dentist. For this reason, adding fluoride to the water is the right thing to do as it helps everybody.

The Expert body continuously considers new studies. If the balance between risks and benefits of drinking water fluoridation changed, the Minister for Health would be informed immediately.

In Ireland, around €5.0 million (2018) is spent on operating water fluoridation processes at Water Treatment Plants annually.  The cost per person is around €1.50 per year.