This article provides an overview of water fluoridation in England. It discusses the impact of fluoride on dental health, an overview of dental health in England, and the importance and implications of dental health inequalities. It also provides an overview of the evidence for water fluoridation as well as the ethical considerations. It does not discuss other interventions such as improving access to dentistry, oral health education and practices in family settings. It also does not discuss water fluoridation in Northern Ireland, Scotland or Wales which is a devolved issue. None of these countries currently operate a water fluoridation scheme.

What is fluoridation?

Fluoride is a naturally occurring substance found in soil, plants and groundwater. Populations whose drinking water contains greater concentrations of fluoride have been found to have lower levels of dental caries than those living in areas where water supplies have lower fluoride concentrations.

The aim of water fluoridation is to reduce levels of dental caries by allowing for fluoride to be present in water supplies. In the UK, the Water Supply (Water Quality) Regulations 2016 allows for up to 1.5mg/l of fluoride to be present in public water supplies. In England, water companies with fluoridation schemes are requested to allow for up to 1mg/l.

Fluoride acts locally on teeth to stimulate remineralisation. When the sugars from food or drink enter the mouth the bacteria in plaque converts them into acid (demineralisation) which without intervention can lead to the formation of cavities. This explains the need for a consistent low-level of fluoride in the mouth as this makes enamel more resistant to chemical erosion once the teeth have developed.

Dental health in England

The preceding decades have seen a general trend towards improved oral health in England. Despite this progress, dental decay is a common disease that affects a significant proportion of the population. Dental health professionals have expressed concern that this situation was exacerbated by the COVID-19 pandemic which, in a survey of 600 dental practices, 88% thought was damaging to the nation’s dental health due to a lack of routine appointments and potential for worsened preventative issues.

Adult dental health

The decennial Adult Dental Health Survey, shows significant increases in the number of adults retaining a greater proportion of their original teeth. Problems are likely to arise, however, in the context of an ageing population as dental decay becomes increasingly challenging and complex to treat.

Poor dental health has an important influence on an individual’s general health and well-being, including pain and infection leading to difficulties eating, sleeping, and socialising.

Whilst very often minor, poor dental health can result in time off work due to pain or for treatment. Dental pain can also lead to impaired concentration and an inability to work productively.

Estimates suggest that poor oral health costs the economy over £105 million a year. Annually, 5% of employees need time off work because of oral ill-health, the equivalent of over 1.2 million lost days of work.

Children’s dental health

Children’s dental health has improved significantly over the preceding decades. Research indicates that there has been a significant decline in dmft in 5-year-olds in England since the early 1970s.

Public Health England reports that dental decay nevertheless remains prevalent among children with 12% of 3-year-olds and 25% of 5-year-olds having caries in their primary teeth, rising up to half of 5-year-olds in some local authorities. This is largely attributable to excessive consumption of sugary food and drinks, which are the primary contributors to the number of dmft experienced by children.

Research evidence shows that the prevalence of caries affects the broader life chances of children who experience pain and infection, which impacts on their ability to learn and develop, thereby leading to missed school days and a lack of confidence. Moreover, if remedial work or extractions are a child’s first introduction to dental care, this can lead to a lifetime of fear and anxiety.

Recent figures show that there were approximately 37,000 hospital admissions of children aged 0 to 19 because of avoidable decay. This is more than twice the number of the second most common cause for admissions – tonsillectomies.

This incurs significant costs, which the Department of Health and Social Care estimates to be in the region of £50 million per year for children aged 0 to 18. It also leads to a significant diversion of health resources including specialist anaesthetic and operating theatre time.

Dental health inequalities

Despite progress in addressing the nation’s dental health, significant inequalities exist. Regional differences in the prevalence of decay in 5 year old children are shown in Figure 1. Among upper-tier local authorities, the prevalence of dental caries among 5-year-olds ranges from 9% in East Sussex to 51% in Blackburn with Darwen, with similarly large differences between 12-year-olds living in different areas.

Inequalities are driven by socio-economic status, with certain groups including homeless people, prisoners, people with disabilities and refugees facing particularly extreme inequalities. Public Health England research on dental inequalities suggests that deprived groups are likely to have worse dental health. Hospital-based tooth extractions are also overwhelmingly based in the most deprived populations, with children in the most deprived quintile over three and a half times more likely to require hospital-based tooth extractions than the least deprived quintile.

This is exacerbated by the fact that access to dental care varies significantly between regions. Dental care has also been subject to a real-terms reduction in funding of 15% between 2010-17. The charges adults pay to access NHS dentistry have increased by 9% in real terms between 2014-15 and 2018-19.

Fluoridation and public health

A number of local authorities have explored the potential for fluoridating community water supplies as a public health response to health inequalities, including those in Sheffield and Hull.

Dental health can be improved through limiting consumption of sugars, regular tooth brushing with fluoridated toothpaste and regular access to dental care. Public Health England, however, suggests that for various reasons, including financial circumstances, adopting and sustaining these behaviours is problematic for those at the greatest risk of dental disease.

Alternative mechanisms for delivering fluoride include fluoridated milk and salt, the latter of which is consumed by most of the populations of Germany and Switzerland.

Fluoridated toothpaste and dental varnishes are also widely available, including in England. Concerns remain however that entrenched dental health inequalities persist despite the availability of these products.

Water fluoridation on the other hand does not require sustained behavioural change at the individual level. While it is particularly beneficial for individuals and communities from deprived backgrounds, it has the benefit of successfully reducing caries prevalence in all sectors of society irrespective of age, oral health behaviours, education, employment, or access to dental care. It can also act as an important complement to the expected benefits of regular tooth brushing, limiting consumption of sugars and access to dental care.

Evidence for the health benefits of fluoridation

The amount of fluoride added to community water supplies depends on local geology (see Figure 2). Of the 6 million people already receiving fluoridated water in England, around 300,000 consume naturally fluoridated water with the remainder adjusted by suppliers adding a fluoride compound.

Consumed within the optimal range, water fluoridation is endorsed by numerous public health bodies including Public Health England, the British Dental Association, World Health Organisation, Canadian Dental Association and US Centres for Disease Control and Prevention.

The association between water fluoridation and dental health has been widely studied. Numerous international systematic and evidence reviews have assessed the quality and quantity of research. These include studies conducted in the UK and internationally as well as, in some instances, those not published in English. Overall, these have found: strong evidence that water fluoridation is associated with fewer dental caries; an increase in the number of individuals with no caries; an increase in caries prevalence when fluoridation schemes are discontinued; and no correlation with adverse health consequences beyond the potential risk of developing dental fluorosis (mottles or flecks on the teeth). For example:

• A UK review in 2000found evidence that water fluoridation reduced caries prevalence by a median of 2.25 dmft/DMFT and also increased the number of caries-free children by 14.6%.
• A 2013 update to the UK review by the Community Preventative Services Task Forcein the US showed a median decrease of 15.2% in caries after community water fluoridation began and an increase in caries when water fluoridation schemes were terminated.
• A 2014 review undertaken by the Royal Society of New Zealand found that 12-13-year-olds from non-fluoridated areas were less likely to be caries-free than their counterparts in fluoridated areas (45.1% vs 56.2%) and more likely to have higher DMFT scores (1.7 vs 1.2).
• A 2015 Cochrane reviewfound a reduction in caries prevalence in children by a median of 1.81 dmft and DMFT 1.16 (a 35 and 26% reduction compared to the median control group mean values), and with a roughly 15% increase in the number of caries free children and adults.
• The National Health and Medical Research Council(2016) review in Australia found that water fluoridation reduces the incidence of dental caries in primary teeth by approximately 35% compared to un-fluoridated water and increases the proportion of children who have no dental caries by approximately 15%.

Side-effects

The risks of negative health effects of fluoridation have been widely studied and summarised in these reviews, most commonly in relation to cancer, bone fractures and dental fluorosis. No correlation was found between fluoridation and an increased risk of cancer and bone fractures. These results were consistent with an evidence review conducted by the Health Research Board (2015) in Ireland which focused exclusively on the potential side-effects associated with consuming fluoridated water.

Common to all however was an observed potential for dental fluorosis, which was found to be more common in fluoridated versus non-fluoridated areas. Research has indicted that dental fluorosis that might be of aesthetic concern occurs in 10.3% of 11- to 14-year-olds receiving fluoridated water compared to 2.2% in non-fluoridated cities. However, it also noted that there was no difference in satisfaction with dental appearance reported between the two groups and that the aesthetic impact of fluorosis diminishes with age.

The cosmetic appearance of dental fluorosis can be treated. Depending on the severity, options range from tooth whitening, adding a hard resin to coat the tooth (bonding), and crowns and veneers.

Quality of evidence

On the best available evidence water fluoridation has an important role to play in reducing caries prevalence and increasing the number of people with no caries at all.

A number of concerns have nevertheless been expressed regarding the overall quality of the available evidence, with the majority of studies being conducted before 1975 and therefore prior to the widespread introduction of fluoridated toothpastes. It is therefore unclear whether the size of the reported benefits of fluoridation would be of a similar magnitude today.

Additionally, research showed that no studies that are considered to be of the highest quality are available. For example, studies that use a control group or which compare data against a baseline. Against this backdrop, numerous reviews have called for more high quality contemporary research.

Population effects

The evidence indicates that fluoridation is particularly beneficial for children. Public Health England suggests that when deprivation and ethnicity are taken into account 5-year-olds and 12-year-olds living in areas with fluoridated water are 28% and 21% less likely to have had tooth decay in their baby teeth than those living in areas without fluoridated water. Water fluoridation also has the potential to reduce hospital admissions to treat dental decay by 59% among children and young people aged 0-19 years.

Role of behavioural change

Beyond population-wide interventions a range of targeted schemes have been developed. These include school-based tooth brushing projects that ensure that children can benefit from the caries-preventive properties of fluoride toothpaste at least once per day, and have the potential benefit of encouraging long-term behavioural and attitudinal change. These include ‘Childsmile’ in Scotland which has contributed to an increase in the number of 11-12-year-olds with no obvious dental decay from 53% in 2005 to 77% in 2017, and Leicester City Council’s ‘Healthy Teeth, Happy Smiles’ programme which reduced tooth decay prevalence in 5-year-olds from 53% to 39% between 2012 and 2017.

Nevertheless, water fluoridation could contribute to the expected impact of these other more targeted measures, thereby helping to further close the dental health inequalities gap.

History of fluoridation and public attitudes

Water fluoridation was first introduced in four trial areas in 1955 against a backdrop of increasing caries prevalence and rapidly declining dentist-to-patient ratio in Britain. Research into the effectiveness of these trials provided clear evidence of the value of fluoridation and contributed to the extension of water fluoridation in England throughout the 1960s including in Birmingham, Worcestershire and Cumberland.

In 1974 decision-making responsibility for initiating water fluoridation schemes was transferred to regional health authorities. Further legislative reforms followed with the Water Fluoridation Act (1985), Water Industry Act (1991) and Health and Social Care Act (2001) which replaced regional health authorities with Strategic Health Authorities (SHAs). In 2003, as part of this reform initiative, The Water Act (2003) placed a duty on water companies to comply with SHA requests to fluoridate drinking water. This was strengthened with the Water Supply (Fluoridation Indemnities) (England) Regulations (2005), which set out the terms of an indemnity to be provided by the Secretary of State for Health to water companies operating fluoridation schemes. The Health and Social Care Act (2012) returned decision-making powers to local authorities with a new duty to take the steps they consider appropriate for improving the health of the people in their local areas, including functions around oral public health generally and water fluoridation in particular. In February 2021 however the Government announced its intention to assume responsibility for initiating, terminating or varying a water fluoridation scheme.

Controversies and public debate

Water fluoridation is controversial to some people. Successive governments have refrained from legislating for its introduction and have instead delegated decision-making powers to local authorities while providing a supporting role.

Water companies have been reluctant to fluoridate water supplies. Throughout the 1970s Bristol and Welsh Water and North-West Water (among others) rejected local authorities’ requests to fluoridate water supplies in the absence of evidence of substantial support from their customers. The thalidomide scandal also loomed large at this time with Woking and District water company rejecting requests to fluoridate water on the basis that it took more than five and a half years for the effects of thalidomide to be fully known.

Water fluoridation has also been heavily contested by a small but vocal minority of the public who contributed to the withdrawal of one of the original trial areas (Andover) after two years.

Protest groups have focused their concerns on: the level of state intervention into the private lives of individuals; the robustness of scientific evidence; possible negative health consequences; and intangible feelings about the purity of water.

Experience therefore shows that attempts to fluoridate community water supplies leads to heated public debate. Social media misinformation is an increasingly important issue in public health interventions, including water fluoridation.

In response, Public Health England has recommended that local authorities address issues authoritatively and confidently to counter untrue assertions and misinformation. It recommends developing a clear communications strategy prior to undertaking public consultations about fluoridation schemes.

Ethical perspectives

The ethical issues associated with water fluoridation are complex.

The Nuffield Council on Bioethics published a report in 2007 examining the role of the Government in helping people to live healthy lives, offering an analysis of the ethical principles that should guide the use of public health interventions. This report included a specific case study on fluoridation and set out three principles that might reasonably guide decisions to justify or reject fluoridation schemes:

• reducing health inequalities;
• reducing ill health; and
• protection of vulnerable groups. It could be argued, for example, that children are both more susceptible to dental caries and less able to make informed choices about their dental health.

The report also observed that the principles of consent, minimising interventions that affect important areas of personal life, and not coercing adults to lead healthy lives could be used to argue against water fluoridation.

The report rejected the view however that, on the basis of arguments related to interference and coercion, water fluoridation should be prohibited outright and instead noted the need to consider these in relation to the balance of risks and benefits. Regarding consent, it was suggested that requiring individual consent is not feasible.

Overall, the report stated that the decision whether (or not) to introduce water fluoridation required justification as both action and inaction are policy options. For this reason, the report called for a mechanism for considering the views of the public in providing a mandate for either option through local decision-making procedures that consider the local context including health needs, the degree of benefit anticipated and the existence of available alternatives.

Other frameworks for analysing ethical issues associated with public health interventions have been proposed, but these do not tend to offer specific analysis of water fluoridation in the UK context. For example, an academic article in 2015 suggested that decisions should be guided by evidence on the following criteria: what the expected health benefits of the intervention are for the target population; what the potential burdens and harms of the intervention are; how the intervention affects the autonomy of the individuals in the target population; impact on equity; and expected efficiency. However, this did not look specifically at water fluoridation.

PHE has published a guide to public health ethics in practice, which provides an introduction to public health ethics both as a philosophical field of enquiry and as an applied area that guides practice and policy.

Data on public attitudes

There is very little academic research on public attitudes to water fluoridation, with some data from Canada (2009) and New Zealand (2016) showing support of 62% and 42% respectively. In England, a recent study published in June 2021 assessed public attitudes in five areas in the North East of England, and found that 60% of respondents were in favour of adding fluoride to the water supply to prevent dental decay, while 16% were opposed. Other available evidence largely rests on opinion polls, a summary of which covering the period 1977 – 2007 suggested that many of these were unreliable and methodologically flawed. A more detailed 2010 report was produced by NHS West Midlands based on results of an Ipsos MORI survey of people’s attitudes to water fluoridation. This found that 18% of people strongly supported water fluoridation, compared with 6% who were strongly opposed. On why, 37% of supporters thought it could successfully reduce tooth decay, whereas of those opposed, 20% said they preferred water to be ‘natural’ and without additives.

Current research on the health impacts of water fluoridation

Water fluoridation research in England is ongoing. For example, an 8-year NIHR-funded ‘CATFISH’ study is in progress, responding to a key challenge from a Medical Research Council report of the need ‘to provide an estimate of the effects of water fluoridation on children aged 3-15 years’. This research draws on the introduction of a recent water fluoridation scheme in Cumbria that although operational since the 1960s, had been off-line for a number of years prior to its re-introduction in 2013. Two prospective groups (cohorts) of participants will be followed up over 6 years. The first of these will be children born one year after fluoridation began with the systemic effect of water fluoridation on their teeth tested at ages 3 and 5. The second group comprises those aged 5 years at the start of the fluoridation scheme and their teeth will be examined at ages 7 and 11 in order to test the topical effect of fluoride. It is due to report findings later in 2021.

This is supplemented with a two-year research project, also funded by the NIHR, assessing the effectiveness and cost-effectiveness of 10-year exposure to water fluoridation in preventing dental treatment and improving oral health in a contemporary adult population. This retrospective cohort study using NHS dental treatment data acquired during 2009-2019 is due to report its findings in January 2022.

Government position on water fluoridation

Water fluoridation in England is permitted by Parliament under the Water Industry Act 1991 (as amended), which outlines the circumstances in which a water company can be required to operate a fluoridation scheme. Decision-making responsibility has resided with local authorities since 2013. In February 2021 however, in a statement about future health and care policy, the Secretary of State for Health and Social Care highlighted the importance of fluoridation in preventing ill-health. They suggested that taking steps such as fluoridation ‘will improve the health of the nation’. The related White Paper proposes to give the Secretary of State for Health and Social Care the power to directly introduce, vary or terminate water fluoridation schemes. The provisions for doing so are outlined in the Health and Care Bill 2021-2022. The intention is for changes to be in place by April 2022. The DHSC published a policy paper on water fluoridation on 19 July 2021, setting out the evidence for the benefits and harm from fluoridation, what the Bill intends to do and how it will improve public health.

The stated intention is to remove the burden from local authorities and allow the Department of Health and Social Care to streamline processes and assume responsibility for new fluoridation schemes. It will also assume responsibility for public consultations which will continue to be a key requirement of the decision-making process (as has historically been the case).

Central government will also become responsible for the associated work, such as the cost of consultations, feasibility studies, and the capital and revenue costs associated with any new and existing schemes. This legislative change, once enacted, marks a radical departure, allowing the government to drive forward and implement new water fluoridation schemes while covering the costs of doing so.

Water quality monitoring

Public water supplies are delivered through a system of water supply zones (WSZs) with each defined by either a single (or multiple) point(s) of water supply to populations of 100,000 or fewer.

Water companies operating schemes must comply with the requirements of the Code of Practice published by the Drinking Water Inspectorate (DWI), the water quality regulator for England and Wales. This includes systems to monitor and control equipment used to add fluoride to water supplies.

Public Health England monitors the effects of water fluoridation schemes on the health of people covered by these arrangements, producing reports at no greater than four-yearly intervals. The next of these is due in 2022.

Acknowledgements

POST is grateful to Dr Gary Lowery (Department of Politics and International Relations, University of Sheffield) for researching this briefing. For further information on this subject, please contact the co-author Dr Sarah Bunn.

POST would like to thank Dr Michaela Goodwin (Division of Dentistry, University of Manchester) and Deborah Moore (Division of Dentistry, University of Manchester) who acted as external peer reviewers in preparation of this article.