Frequently Asked Questions on Fluoride and Water Fluoridation

Fluoride is the free ion of the element fluorine. Fluorine is a natural part of the Earth’s crust as a naturally occurring fluoride compound found in rocks, soil, natural water sources, plants, vegetables, fruits, tea, and animals. Fluoride is found in waters in many parts of the world. Still, the amount varies depending on the region and source of water¹. In ocean water, fluoride is typically in the range of 1.2 to 1.4 ppm (mg/l)².

In Irish groundwater, the natural fluoride level is at a relatively low level and typically not more than 0.2 mg/l. Groundwater from one monitoring point in Co. Monaghan was found to have a median F concentration of 2.0 mg/l F.

Fluoride concentrations across other monitoring points (nationwide) showed a relatively narrow range, with medians ranging from 0.1 to 0.3 mg/l. Fifty eight percent of samples had concentrations below the limit of detection³.

Fluoride level in water is measured by milligram per litre (mg/l) or parts per million (ppm). The units are used interchangeably, and in this text when referencing other sources, we use the units as presented in the referenced source.

1 National Health and Medical Research Council (NHMRC) 2017, Information paper – Water fluoridation: dental and other human health outcomes, report prepared by the Clinical Trials Centre at University of Sydney, NHMRC; Canberra.

2 Edmunds, W. Mike, and Pauline L. Smedley. "Fluoride in natural waters." Essentials of medical geology. Springer, Dordrecht, 2013. 311-336.

3 Tedd, K., Coxon, C., Misstear, B., Daly, D., Craig, M., Mannix, A., & Williams, T. H. (2017). Assessing and developing Natural Background Levels for chemical parameters in Irish groundwater. Environmental Protection Agency, Wexford, 183.

Community water fluoridation is the adjustment of the natural fluoride concentration in drinking water to the recommended level¹ to prevent tooth decay (dental caries). Water is currently fluoridated by adding fluorosilicic acid or hydrofluosilicic acid to public water supplies².

1 Government of Ireland 2002. Forum on Fluoridation Report https://www.fluoridesandhealth.ie/assets/files/documents/fluoridation_forum.pdf

2 Sutton, M., Kiersey, R., Farragher L., Long J. "Health effects of water fluoridation." An Evidence Review 2015.

Fluoride plays a key role in the prevention of tooth decay. It works in two ways¹.

1) Before teeth appear in the mouth, fluoride is incorporated into the developing tooth, which reduces the tooth enamel solubility (demineralisation) making teeth more resistant to tooth decay.

2) After teeth appear in the mouth, fluoride help reverse the early stage of tooth decay formation. This is because the availability of fluoride helps to remineralise the tooth enamel and impacts the metabolic pathways of microflora in the mouth and their ability to produce sticky plaque.

1^ Buzalaf, Marília Afonso Rabelo, et al. Mechanisms of action of fluoride for caries control. Fluoride and the oral environment. Vol. 22. Karger Publishers, 2011. 97-114.

Tooth decay develops when bacteria in your mouth break down sugar-containing foods, thus releasing acid on the tooth surface. This acid removes minerals from the tooth's surface (demineralisation), which can lead to tooth decay.

Drinking fluoridated water, use of fluoride toothpaste and some mouthwashes helps to reverse the tooth mineral loss (remineralisation) in the early stages¹. Fluoride benefits people of all ages, including the young and elderly by protecting the developing teeth in the gum, and the tooth present in the mouth. It is important for baby teeth (primary dentition) and adult teeth (permanent teeth).

1 Sutton, M., Kiersey, R., Farragher L., Long J. "Health effects of water fluoridation." An Evidence Review 2015.

Hydrofluosilicic acid (HFSA) is the product used for water fluoridation in Ireland¹. HFSA has no taste or smell when it is added to water.

1 European Standard I.S.EN 12175:2013 Chemicals used for treatment of water intended for human consumption, Hydrofluorosilicic acid.

No. The compounds most commonly used to add fluoride to public water supplies are displayed in the following reaction:

H₂[SiF₆]   (HFSA, the fluoridation chemical) + 2H₂O (water)  → (gives) 6H⁺ (hydrogen ions)  + SiO₂ (silica, commonly known a sand)  +  6F (fluoride)

This reaction is essentially complete within about 12 minutes, which is well before the water arrives at the consumer's tap from the water treatment plant. The products of the reaction are hydrogen ions (which are removed through a process called buffering), silica (sand) and fluoride ions.

Silica is already present in drinking water from natural water sources and is harmless. The amount added by fluoridation is a fraction of that typically naturally present in water.

Thus, the consumer is presented at the tap with fluoride, not with HFSA or other fluorosilicates.

No. The consumer is frequently misinformed on this matter. It is sourced as a primary product; it is mined directly from a raw material source, the mineral fluorospar as calcium fluoride (CaF₂). CaF₂ goes through a purification process to conform to tightly controlled specifications under the requirements of CEN Standard to produce Hydrofluosilicic Acid (HFSA), which is then added to water¹.

HFSA is produced by a Spanish company (Derivados del Fluor). Visits have been conducted on two separate occasions (2006 and 2015) to Derivados del Fluor in Spain to ensure the Expert Body on Fluorides and Health understands how hydrofluosilicic acid is produced and to confirm there are strict systems and controls in place to ensure its consistency, purity and safety. These visits assured the Expert Body on Fluorides and Health that production complies with quality, environmental and safety systems.

1^ European Standard I.S.EN 12175:2013 Chemicals used for treatment of water intended for human consumption, Hydrofluorosilicic acid.

Since July 1^st 2007, the level of fluoride in drinking water in Ireland has been set at between 0.6–0.8 ppm¹. This level of fluoride is deemed best for protecting the oral health of all age groups and to take account for other sources of fluoride such as toothpaste. The EU Directive, COUNCIL DIRECTIVE 98/83/EC of November 3^rd 1998 on the quality of water intended for human consumption, specifies that the level should not exceed 1.5 milligrams fluoride /litre of water. Thus the Irish statutory level of between 0.6-0.8ppm fluoride is around half the maximum permitted by the EU. The Irish limit for fluoride that is naturally present in water supplies is 1.5 ppm (mg/l), (S.I. No. 122/2014 - European Union (Drinking Water) Regulations 2014)². A parametric value of 0.8mg/l is set for public water supplies where the fluoride level is adjusted upwards.

1^ Fluoridation of Water Supplies Regulations 2007, Statutory Instrument No. 42 of 2007, Irish Statute Book http://www.irishstatutebook.ie/eli/2007/si/42/made/en/print.

2^ European Union (Drinking Water) Regulations 2014 (S.I. No. 122 of 2014). Irish Statute Book http://www.irishstatutebook.ie/eli/2014/si/122/made/en/pdf

No. Many countries have water fluoridation schemes, including Australia, Canada, New Zealand, Spain, the United Kingdom, and the United States. Water fluoridation is less common in Europe, where fluoridated salt and milk are often available as an alternative, but some populations are also supplied with naturally fluoridated public water.

The Health Service Executive (HSE) is legally responsible for arranging for the fluoridation of public water supplies. However, Irish Water undertakes fluoridation on behalf of the HSE as part of overall water treatment and supply.

The Expert Body on Fluorides and Health continues to support a detailed Code of Practice on the Fluoridation of Drinking Water¹ to ensure quality assurance across the delivery of water fluoridation. This Code sets standards and governs all quality systems and practices required for fluoride provision from storage, dosage, safety, and technical aspects through to practical plans.

1^ The Irish Expert Body of Fluorides and Health. Code of Practice on the Fluoridation of Drinking Water 2016 ISBN: 978-0-9551231-4-6 https://www.fluoridesandhealth.ie/assets/files/documents/codeofpractice.pdf

Yes. The regulations require that a daily test is carried out at the water treatment plants by the Water Service Authorities personnel. Monthly fluoride testing of fluoridated supplies is carried out by the Health Service Executive in accordance with the requirements of the Fluoridation of Water Supplies Regulations 2007 (S.I. No. 42/2007)¹.

Testing is also carried out on behalf of Irish Water to determine compliance with the Drinking Water Regulations, which also require monitoring of fluoride levels in water supplies².

1 Buzalaf, Marília Afonso Rabelo, et al. Mechanisms of action of fluoride for caries control. Fluoride and the oral environment. Vol. 22. Karger Publishers, 2011. 97-114.

2 Fluoridation of Water Supplies Regulations 2007, Statutory Instrument No. 42 of 2007, Irish Statute Book http://www.irishstatutebook.ie/eli/2007/si/42/made/en/print.

The permissible concentrations of fluoride in drinking waters are governed at both national and European Union level. Under the provisions of Statutory Instrument No 42 of 2007 Fluoridation of Water Supplies Regulations 2007, the concentrations of fluoride in fluoridated public water supplies must be in the range 0.6-0.8 mg/l. The EU Directive, COUNCIL DIRECTIVE 98/83/EC of November 3^rd 1998 on the quality of water intended for human consumption, specifies that the level should not exceed 1.5 milligrams fluoride /litre of water. The Irish statutory level of 0.6-0.8 mg/l fluoride is around half the maximum permitted by the EU.

The water is tested daily on behalf of Irish Water by appropriately trained personnel. This testing is in addition to the statutory monthly sampling carried out by the Health Service Executive, Environmental Health Service.

If a test result at a water treatment plant is outside the range specified by Statutory Instrument No 42 of 2007, prompt adjustments are made to the dosing equipment, and a new test carried out to ensure that it is within specification. There are monthly tests carried out by the Public Analyst Laboratories. The Public Analyst Laboratory (PAL) is an Official Food Control laboratory within the Health Service Executive (HSE). The laboratory provides both a chemical and microbiological analytical service. The analytical results are sent from the Public Analyst's laboratory to the HSE Environmental Health Service (EHS), which had collected the water samples. If fluoride values are either too high or too low, a notification will be sent to those responsible for the fluoridation of the supply in question, stating that adjustment of the dosage is required promptly. The EHS liaise with the HSE Dental Service.

Irish Water also reports to the Environmental Protection Agency (EPA) on a range of parameters, including fluoride. Irish water also prepares and publishes an annual report on the quality of drinking water in Ireland.

Modern diets are high in sugars. In the Republic of Ireland, 26% of children eat sweets every day, and 13% of children consume soft drinks daily¹. Nine percent of the adult population consumes sugar-sweetened drinks every day, and 33% drink them at least once a week. Also, 15% of youths (15 to 24-year-olds) have at least one sugar-sweetened drink on a daily basis ². Some ready-made meals can also be high in sugars. Fluoride can protect teeth from the damage done by sugar, however, there is overwhelming evidence that frequent consumption of sugars is associated with caries. So, to prevent tooth decay the best advice is to limit the frequency of sugar intake and protect your teeth with fluoride. Dietary advice should be aimed at limiting the frequency of sugar intake. Studies have shown that sugar consumption remains a moderate risk factor for caries even when populations have adequate exposure to fluoride³. Water fluoridation gives everyone in society access to the effective fluoride amount needed to strengthen their teeth and reduce the chances of having tooth decay.

1^ Gavin, Aoife, et al. "The Irish health behaviour in school-aged children (HBSC) study 2014." (2015).

2^ Healthy Ireland survey 2018: summary of findings. Department of Health (DoH), 2019.

3^ Oral Health in Ireland: A Handbook for Health Professionals Second Edition 2014. Dental Health Foundation & Oral Health Services Research Centre Cork, University College Cork

Yes, water fluoridation is considered one of the most cost-effective, equitable, and safe interventions to prevent tooth decay. Even though fluoridated toothpaste is widely available, studies show that children living in fluoridated areas have less tooth decay than those who do not ¹. Combining water fluoridation with fluoride toothpaste use has greater caries reduction benefits, especially for children.

1^ The Fluoride and Caring For Children’s Teeth Study (FACCT) (2016) https://www.ucc.ie/en/ohsrc/research/facct/ accessed 27^th August 2020

Yes, the majority of bottled waters for sale in Ireland do not contain optimal levels (0.6 - 0.8ppm) of fluoride for the prevention of tooth decay.

Yes, there is a substantial body of evidence to show that water fluoridation is effective in the prevention and control of tooth decay^{1 2}. Figures show, including those in the Fluoride And Caring For Children’s Teeth (FAACT) Study that there have been lower levels of tooth decay in Ireland for children living in areas supplied by fluoridated drinking water compared to those living in non-fluoridated areas^{3 4}. Combining water fluoridation with fluoride toothpaste use has greater caries reduction benefits,⁵ especially for children.

1^ Spencer, A.J., Do^, L.G.,  Ha, D.H. (2018) Contemporary Evidence on the Effectiveness of Water Fluoridation in the Prevention of Childhood Caries https://pubmed.ncbi.nlm.nih.gov/29869803/

2^ Do, L., et al. (2017) Effectiveness of Water Fluoridation in the Prevention of Dental Caries Across Adult Age Groups

3^ FACCT Website: Presentations and Publications available at https://www.ucc.ie/en/ohsrc/research/facct/publicationspresentations/ [Accessed June 9^th 2020]

4^ Whelton, H., et al. Dental caries and enamel fluorosis among the fluoridated and non-fluoridated populations in the Republic of Ireland in 2002. Community Dental Health 21.1 (2004): 37-44.

5^ Toumba, K.J., Twetman, S., Splieth, C. et al. Guidelines on the use of fluoride for caries prevention in children: an updated EAPD policy document. Eur Arch Paediatr Dent 20, 507–516 (2019). https://doi.org/10.1007/s40368-019-00464-2

The evidence to date suggests that drinking fluoridated water within the optimal range (0.6-0.8ppm) of fluoride in the water does not cause ill health effects^{1 2}.

Waters with high levels of naturally occurring fluoride present are mostly found at the foot of high mountains and in areas where the sea has made geological deposits. Known fluoride belts on land include one that stretches from Syria through Jordan, Egypt, Libya, Algeria, Sudan and Kenya, and another that stretches from Turkey through Iraq, Iran, Afghanistan, India, northern Thailand and China. There are similar belts in the Americas and Japan. In these areas, fluoride levels in water of up to a concentration of 20 ppm have been reported. At these high levels, severe dental fluorosis and skeletal fluorosis are common³. High levels of naturally occurring fluoride are not found in public water supplies in Ireland. The Environmental Protection Agency produces annual drinking reports which examine compliance with monitored parameters, these reports are accessible to the public on the EPA website www.epa.ie.

Many organisations around the world, including the World Health Organisation (WHO), support water fluoridation. The WHO recommends for those countries without access to optimal levels of fluoride, and which have not yet established systematic fluoridation programmes, to consider the development and implementation of fluoridation programmes, giving priority to equitable strategies such as the automatic administration of fluoride, for example, in drinking-water, salt or milk, and to the provision of affordable fluoride toothpaste².

At the 2007 WHO World Health Assembly, a resolution was passed that universal access to fluoride for caries prevention was to be part of the basic right to human health (Petersen, 2008). There are three basic fluoride delivery methods for caries prevention; community-based (fluoridated water, salt and milk), professionally administered (fluoride gels, varnishes) and self-administered (toothpaste and mouth rinses). In 1999 the US Centers for Disease Control and Prevention rated community water fluoridation one of the ten most important public health achievements of the twentieth century.

In 2015, the Health Research Board (HRB) on behalf of the Department of Health (Ireland) reviewed the evidence on the impact of water fluoridation at its current level on the health of the population. They found no definitive evidence that community water fluoridation is associated with adverse health effects. Also, the Expert Body on Fluorides and Health, appointed by the Minister for Health, continually reviews new and emerging literature to ensure that it is safe to consume water to which fluoride is added within the statutory limits.

Water fluoridation is one of the longest and most widely studied public health policies in the world. The balance of international evidence suggests that optimal water fluoridation does not cause any health side effects at the concentrations used for CWF other than dental fluorosis ^{1 4 5}.

Dental fluorosis a cosmetic or aesthetic condition which can affect the appearance of the teeth, is identified more frequently in areas with community water fluoridation. At the current level of fluoride in Ireland's water supplies (0.6 - 0.8ppm), the dental fluorosis that is identified is described as ‘very mild’ or’ mild’ when compared to standardised photographs and descriptions (Dean, 1942)⁶. ‘Very mild’ or’ mild’ can be described as small, opaque, paper white areas scattered irregularly over the tooth, affecting less than 50% of the tooth. Not all white marks are caused by fluoride. In the majority of cases, dental fluorosis at the levels seen with community water fluoridation, does not require treatment⁷. Anyone with concerns in this regard should consult their dentist.

1 Government of Ireland 2002. Forum on Fluoridation Report https://www.fluoridesandhealth.ie/assets/files/documents/fluoridation_forum.pdf

2 ^World Health Organization (2019) Preventing Disease Through Healthy Environments, Inadequate or Excess Fluoride: A Major Public Health Concern

3 Sutton, M., Kiersey, R., Farragher L., Long J. "Health effects of water fluoridation." An Evidence Review 2015.

4^ National Health and Medical Research Council (NHMRC). "Information paper-Water fluoridation: dental and other human health outcomes, report prepared by the Clinical Trials Centre at University of Sydney." (2017).

5 National Academies of Science, Engineering and Medicine, 2020. Review of the Draft NTP Monograph: Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects. Washington, DC: The National Academies Press https://doi.org/10.17226/25715

6 Dean HT. 1942. The investigation of physiological effects by the epidemiological method. In: Moulton, FR (ed) Fluorine and Dental Health American Association for the Advancement of Science. 19:23-31.

7 Whelton, H., et al. Dental caries and enamel fluorosis among the fluoridated and non-fluoridated populations in the Republic of Ireland in 2002. Community Dental Health 21.1 (2004): 37-44.

The most authoritative statement on the issue in this jurisdiction is the Health Research Board’s report Health Effects of Water Fluoridation: An Evidence Review 2015 which was commissioned by the Department of Health to examine the impact, either positive or negative, on the systemic health of the population for those exposed to artificially fluoridated water between 0.4 and 1.5ppm.

Other than dental fluorosis, the scientific literature supports the fact that there are no adverse health effects associated with community water fluoridation (CWF) at the levels permissible in the Republic of Ireland.

The evidence review found no strong evidence that CWF was definitively associated with adverse health effectsand recommended the need for further studies designed to overcome shortcomings.

The report concluded that further research is required, especially in relation to bone health (osteosarcoma and bone density) and thyroid disease (hypothyroidism). The report also indicated that outcomes in areas with community water fluoridation and high levels of naturally occurring fluoride may be different. For a more detailed discussion, see the HRB report, which is available at: https://www.hrb.ie/fileadmin/publications_files/Health_Effects_of_Water_Fluoridation.pdf The Expert Body on Fluorides and Health continues to review all relevant new and emerging research in the area of neurocognition and IQ. This includes the 2019 draft report published by the US National Toxicology Programme (NTP) and the subsequent assessment of this report published by the US National Academy of Sciences (NAS) in 2020^{1 2}. The NAS recommended that further research be conducted in this area in order to validate and confirm the conclusions of the NTP report. The Irish Expert Body on Fluorides and Health continues to monitor this and all emerging research in this area very closely and has recommended that additional research be commissioned into this area in Ireland. All new research concerning health effects associated with CWF is kept under continual review by the Expert Body on Fluorides and Health. If a serious concern were noted, the Minister for Health would be advised.

1 National Academies of Science, Engineering and Medicine, 2020. Review of the Draft NTP Monograph: Systematic Review of Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects. Washington, DC: The National Academies Press https://doi.org/10.17226/25715

2 NTP 2019. Systematic review of fluoride exposure and neurodevelopmental and cognitive health effects. National Toxicology Programme, USA

Yes, fluoridated tap water 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 trace amounts and/or low levels of fluoride. The FSAI Scientific Committee, in agreement with a prior 2004 study regarding the fluoride content of infant formula reconstituted with Irish fluoridated tap water ^[2], concluded that  there was no scientific basis for concerns about the safety of children in Ireland from exposure to fluoride from foods and no significant  evidence of adverse effects to the health of infants consuming infant formula that is made up with fluoridated tap water at current statutory levels for Ireland (0.6 – 0.8 ppm).  The Expert Body emphasises that there is no recommendation to discontinue using fluoridated tap water at current statutory levels in Ireland. Where an individual is uncertain the advice of a health professional such as a dentist, public health nurse or paediatrician should be sought.

[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

From extensive literature fluoridation is known to substantially decrease tooth decay. The Fluoride and Caring for Children's Teeth (FACCT) survey was a University College Cork-led research project undertaken between 2014 and 2017 https://www.ucc.ie/en/ohsrc/research/facct/publicationspresentations/. FACCT shows that the presence and severity of tooth decay is less in children living in areas with community water fluoridation. Ceasing water fluoridation would lead not only to social costs such as pain and trauma, as well as work or school absenteeism, but also to the additional financial burden of treating tooth decay. The FACCT study investigated the societal net benefit of community water fluoridation for 5, 8 and 12-year-old-children and estimated it at €2.6 million in 2017 and as a policy compares favourably to its cost (in publication). https://www.ucc.ie/en/ohsrc/research/facct/publicationspresentations/

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 at the appropriate levels, it dissociates, and it is no longer corrosive.

It is widely accepted that community water fluoridation (CWF) is ethical. (seehttps://www.nuffieldbioethics.org/assets/pdfs/Public-health-ethical-issues.pdf). A number of ethical principles are engaged, namely autonomy, beneficence, non-maleficence and justice. While autonomy must generally be respected, there are situations where over-riding individual autonomy is justified for the greater good, e.g. we are required to wear safety belts when driving to prevent injury to ourselves or others and we are prevented from smoking in public places to help avoid smoking-associated illnesses in others. Similarly, in the COVID-19 pandemic we were advised to limit our movements and to wear facemasks to protect both ourselves and others. CWF is an effective means of preventing dental decay, particularly in vulnerable groups such as those who cannot afford other sources of fluoride such as fluoridated toothpaste. A greater societal benefit in general is considered justifiable. For healthcare interventions to be considered ethical, they must satisfy the principles of beneficence and non-maleficence. Beneficence means that the intervention must confer a benefit, and the evidence shows that CWF remains an effective means of preventing dental decay. Non-maleficence implies that the intervention must do no harm, and the evidence indicates that CWF causes no adverse health effects other than dental fluorosis (discussed above). Finally, CWF satisfies the principle of justice as it is effective in improving dental health for those with higher levels of dental decay. CWF helps to address the imbalance between those with lower and higher levels of decay. The Irish Expert Body on Fluorides and Health continuously considers new studies. If the balance between risks and benefits of drinking water fluoridation changed, the Minister for Health would be informed immediately. For further information on the ethics of CWF, see Chapter 7 of the Nuffield Council on Bioethics' report Public Health: Ethical Issues, available at https://www.nuffieldbioethics.org/assets/pdfs/Public-health-ethical-issues.pdf.

In Ireland, around €5.0 million (2018) is spent on operating water fluoridation processes at Water Treatment Plants annually. 

The lifetime cost per person is around €1.50 per annum¹. The recent FACCT study identified, the societal net benefit of CWF for 5, 8 and 12-year-old-children was estimated at €2.6 million in 2017 or an average saving of €17.68 per child, of which 71% was attributed to direct treatment savings. The benefits of CWF as an oral health policy compares favourably to its cost with a benefit cost ratio estimated at 9.2:1 for these groups of children (In publication). https://www.ucc.ie/en/ohsrc/research/facct/publicationspresentations/

1^ "Water Fluoridation Cost €5.1M Last Year — Doh". Medical Independent, 2019, https://www.medicalindependent.ie/water-fluoridation-cost-e5-1m-last-year-doh/.