Tap water talk: The continuing debate over water fluoridation.

This article is written for the wider oral healthcare team and aims to provide an international evidence-based overview of the current arguments for and against adding fluoride to the public water supply. Water fluoridation remains a hotly debated topic and, with ongoing changes to UK policy and wider access to fluoride in products such as toothpaste, it is important for all dental professionals to consider and keep updated with the latest research. The topic has long stirred public debate, for example, a high-profile attempt to introduce fluoridation in Southampton, UK, was abandoned in 2015 following strong public opposition and legal challenges.¹ In a historic decision, Utah has just become the first US state to ban fluoridated water from its public system amid safety concerns.²

In the UK, despite public opposition, the government continues to support water fluoridation as a public health measure,³ whilst only 10% of the population receives fluoridated water through public supply schemes. When accounting for naturally occurring fluoride in some water sources, overall fluoride exposure in the population is estimated to reach around 14%.³ The 2022 Health and Care Act transferred decision-making powers for fluoridation schemes from local authorities to the Secretary of State for Health and Social Care, aiming to facilitate the implementation of new programmes.⁴

Historically, water fluoridation was introduced to help with increasing levels of consumed dietary sugar and was associated with reductions in dental caries. Early studies reported that the introduction of fluoridated water led to children having 35% fewer decayed, missing, and filled primary teeth and 26% fewer decayed, missing, and filled permanent teeth.⁵ However, with the widespread availability of fluoride-containing dental products (eg toothpaste), the 2023 Cochrane review noted that while fluoridation reduces dental decay, the magnitude of the benefit is very small in populations with extensive access to fluoride toothpaste.⁶

Cost data

In the United States (population 340 million), the Centers for Disease Control and Prevention (CDC) estimates that the cost of fluoridating water ranges between US$1 and US$3 per person annually, resulting in a national expenditure of approximately US$1.2 billion.⁷ In contrast, in the United Kingdom (population 69 million), annual spending on water fluoridation is estimated at around £30 million. Given that 10% of the population consume fluoridated water, the cost per person is approximately £4 per person annually.⁵

Excessive exposure can lead to adverse health effects. Dental fluorosis, resulting from high fluoride intake during tooth development, may cause discoloration and mottling of teeth, while severe cases of skeletal fluorosis can lead to pain and damage to bones and joints. Recent epidemiological studies have raised concerns about fluoride’s potential neurotoxic effects, particularly in children, with research suggesting that high fluoride exposure may be linked to reduced intelligence measures.⁸ In addition, studies have indicated that elevated fluoride intake during pregnancy may adversely affect foetal development.⁹

Tea is recognised as a significant dietary source of fluoride. A recent study published in Scientific Reports found that black tea infusions can contain high and variable levels of fluoride depending on tea type, origin, and brewing conditions which may lead to substantial fluoride intake among heavy tea drinkers.¹⁰ Research published in the Scandinavian Journal of Public Health critically reviewed the physiological effects of ingested fluoride from beverages and raised concerns regarding increased exposure during pregnancy due to potential developmental risks.¹¹ These findings demonstrate the importance of monitoring fluoride exposure from tea and similar beverages, especially for pregnant women.

Fluoride should not be a blanket term because the chemical compounds used in water fluoridation differ from those in toothpaste, resulting in variations in toxicity profiles and manufacturing processes.

• Fluorosilicic acid (H₂SiF₆): Used in water fluoridation and derived as a by-product of phosphate fertiliser production and is highly corrosive. Once added to water and fully diluted, it dissociates into fluoride ions; however, its industrial origin raises concerns about potential contaminants
• Sodium fluoride (NaF): Commonly found in toothpaste and some water supplies, it is produced by neutralising hydrofluoric acid with sodium hydroxide. It is highly soluble, rapidly absorbed, and exhibits high acute toxicity due to its direct impact on blood calcium levels if ingested undiluted
• Sodium fluorosilicate (Na₂SiF₆): Also used in water fluoridation and sourced as a by-product from the phosphate and aluminium industries, is less corrosive than fluorosilicic acid but remains hazardous in concentrated forms, especially if not properly refined and potentially containing trace contaminants such as arsenic or lead.

Toxicological studies indicate that sodium fluoride poses the highest acute toxicity when ingested, primarily due to its rapid absorption and effects on blood calcium levels. Although fluorosilicic acid and sodium fluorosilicate are less bioavailable until hydrolysed in water, they remain hazardous in concentrated or industrial forms.¹²

United States

Approximately 73% of the US population served by public water systems receives fluoridated water, however caries levels remain high, particularly among low-income groups. National surveys report 45.8% of children aged two to 19 have experienced dental caries in their permanent teeth.¹³

Average daily sugar consumption: Data from the National Health and Nutrition Examination Survey (NHANES) indicate that US adults on average consume approximately 82 grams of added sugar per day.¹⁴ In addition, government subsidies (from public taxation) support the domestic sugar industry at approximately US$1.4 billion annually!¹⁵ As well as supporting the sugar industry, the US government indirectly encourages people to consume sugar through the Supplemental Nutrition Assistance Programme (SNAP) which aims to reduce food insecurity among America’s most socio-economically vulnerable households by providing cash assistance to low-income families.¹⁶ The cost to the taxpayer is $112 billion per year.¹⁷ The participants in SNAP consume greater amounts of sugar and sweetened beverages compared to non-eligible individuals.¹⁸

United Kingdom

Only around 10-14% of the population receives fluoridated water. Despite this, adult dental health in the UK is slightly better than that in the US suggesting that factors such as ‘relatively’ lower sugar consumption contribute to these outcomes.¹⁹

Average daily sugar consumption: The National Diet and Nutrition Survey (NDNS) reports that the average daily total sugar intake among UK adults is approximately 60 grams.²⁰ The UK government indirectly supports the sugar industry through measures like tariff quotas. For example, UK implemented an Autonomous Tariff Rate Quota on raw cane sugar on 1 January 2021 at a level of 260,000 tonnes per year with an in-quota rate of 0%. These trade policies allow imports of specific goods up to a certain quantity to enter a country at a zero-tariff rate during a specified period.²¹

Sweden and the Netherlands

Neither country practises water fluoridation, yet their dental health outcomes are comparable to those in fluoridated nations. For example, in Sweden, the proportion of 4-year-olds with dental caries decreased from 83% in 1967 to 38% in 2007 which was largely attributed to robust education initiatives.²²

Average daily sugar consumption: The Swedish National Food Survey (Riksmaten 2010-11) suggests that the average daily sugar consumption in Sweden is approximately 50 grams.²³

While fluoride has traditionally been central to caries prevention, alternative approaches should be considered. Reducing sugar consumption is essential. The World Health Organization recommends that free sugar intake be limited to less than 10% of total energy intake, ideally below 5%, to minimise caries risk.²⁴ In addition, addressing the bacterial association of dental caries with primarily Streptococcus mutans, can further enhance preventive strategies. Regular use of xylitol-containing chewing gum or lozenges has been shown to decrease caries incidence in both children and adults,²⁵ and systematic reviews suggest that xylitol can significantly reduce salivary S. mutans levels and help prevent early childhood caries.²⁶

These data illustrate that dietary sugar intake significantly impacts oral health outcomes. In the United States, higher sugar consumption (82 g/day), combined with substantial government subsidies of approximately US$1.4 billion annually (not accounting for the $112 billion SNAP) fosters a high-sugar environment that exacerbates dental caries despite widespread fluoridation. In contrast, the United Kingdom experiences less caries with only 10% fluoridation and lower sugar consumption (60 g/day). When considering funds allocated for water fluoridation, approximately US$1.2 billion in the USA, the total annual spending amounts to roughly US$2.6 billion and £30 million, respectively. Redirecting these resources toward initiatives focused on sugar reduction and prevention could lead to substantial improvements in dental caries rates and wider health outcomes, including lower rates of diabetes, heart disease, and other inflammatory conditions.²⁷

Water fluoridation remains a widely supported public health policy despite facing public opposition.

Water fluoridation remains a widely supported public health policy despite facing public opposition. While systemic fluoridation has historically reduced dental caries, especially in communities lacking dental care access, current widespread availability of fluoride in dental products and extensive governmental sugar industry support calls for re-evaluation. Future public health strategies should prioritise dietary sugar reduction, transparency in policymaking, and community engagement. Additionally, promoting evidence-based preventive interventions, such as xylitol, offers safer alternatives for managing oral health without concerns related to mass medication. Balancing the benefits and risks of fluoride exposure and addressing sugar consumption at a community level should be central to informed policy decisions moving forward.

I encourage all dental professionals to apply their critical thinking by examining the evidence base surrounding water fluoridation, sugar policy and the democratic wishes of the public. If the stance of professional organisations does not align with your understanding of the evidence and the preferences of your patients, engage with them and advocate for change. Start a discussion.

Meaningful advocacy from the dental profession can drive policy change and improve population health.

Governments that subsidise sugar or directly/indirectly support the sugar industry while promoting fluoridation present conflicting health policies. You can make a difference by writing to your local or national representatives, urging them to redirect public health funding toward evidence-based sugar reduction programmes, comprehensive oral health education, and preventive approaches such as xylitol. Meaningful advocacy from the dental profession can drive policy change and improve population health.

Authors and Affiliations

1. Dental hygienist and clinical teacher, Rutland, UK

   Timothy Ives

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