Opinions on the 2011 SCHER report on fluoridation for the Layman
About this publication on Fluoridation
1. Source for this Publication
The texts in level 3 are directly sourced from “Critical review of any new evidence on the hazard profile, health effects, and human exposure to fluoride and the fluoridating agents of drinking water”, a report produced in 2011 by the SCHER (Scientific Committee on Health and Environmental Risks) of the European Commission.
Levels 1 and 2 [included here] were written by Dr Jon Turney.
2. The Scientific Committee on Health and Environmental Risks (SCHER)
The Scientific Committee on Health and Environmental Risks (SCHER) is one of three independent non-food committees which give scientific advice on consumer safety, public health and the environment.
The SCHER was set up in 2004 to offer opinions on environmental pollutants and their health and environmental risks, sand how these may best be assessed. The Committee which produced this report had 17 members, and convened a working group of 7, assisted by advice from 4 additional external experts.
For further information on the SCHER see: http://ec.europa.eu/health/scientific_committees/environmental_risks/index_en.htm
Water fluoridation has been adopted as a public health measure in some EU countries to help prevent tooth decay. Fluoride’s costs and benefits and effects have been investigated by the European Food Safety Authority, in 2005 and 2008, and the Commission Scientific Committee on Consumer Products, in 2009.
There is recurrent controversy over the benefit of water fluoridation. The Commission asked the SCHER to review the latest evidence on fluoride’s health and environmental effects.
4. Specific questions put to the SCHER by the European Commission
In its report, the Scientific Committee was asked to answer the following:
1. Taking into consideration the SCCP opinion of 20.09.05 (SCCP2005) on the safety of fluorine compounds in oral hygiene products, the EFSA NDA opinion of 22.2.05 on the Tolerable Upper Intake Level of Fluoride, and the EFSA CONTAM panel opinion of 22.06.05.
a. Critically review any information that is available in the public domain on the hazard profile and epidemiological evidence of adverse and/or beneficial health effects of fluoride. In particular the Committee should consider evidence that has become available after 2005, but also evidence produced before which was not considered by the SCCP and EFSA panels at the time.
b. Conduct an integrated exposure assessment for fluoride covering all known possible sources (both anthropogenic and natural). In doing so, and in the case of uncertainties or lack of actual exposure data, the SCHER is requested to conduct a sensitivity analysis that includes a range of possible exposure scenarios (e.g. sources, age group), and describe using appropriate quantitative or qualitative means the weight-of-evidence behind each scenario, the uncertainties surrounding each scenario, and the probability of it occurring in real life.
c. On the basis of its answers above, the SCHER is also asked:
c1 – To evaluate the evidence of the role of fluoride in tooth decay prevention and rank the various exposure situations as to their effectiveness in offering a potential tooth decay preventive action.
c2 – To make a pronouncement as to whether there may be reasons for concern arising from the exposure of humans to fluoride and if so identify exposure scenarios that may give rise to particular concern for any population subgroup.
d. Identify any additional investigative work that needs to be done in order to fill data gaps in the hazard profile, the health effects and the exposure assessment of fluoride.
2. Assess the health and environmental risks that may be associated with the use of the most common drinking water fluoridation agents, silicofluorides (e.g. (hydro)fluorosilicic acid, sodium silicofluoride, disodium hexafluorosilicate or hexafluorosilicate or hexafluorosilicic acid), taking into account their hazard profiles, their mode of use in water fluoridation, their physical chemical behaviour when diluted in water, and the possible adverse effects they may have in exacerbating fluoride health effects as reported in some studies.
Level 2 Details
Fluoride is a naturally occurring element, abundant in the Earth’s crust. It is not essential for growth and development of humans or other organisms. Most fluorine occurs as insoluble fluorides, but there is some ionised fluoride in soil and groundwater.
There are large differences in the amount of fluoride found naturally in water supplies. Observation of large populations suggested that people drinking water high in fluoride have better dental health, and less tooth decay, than those consuming less fluoride as they drink. As a result, some countries have added fluoride to drinking water as a public health measure. This remains controversial. Some suggest that it is unnecessary, because most people receive enough fluoride from other sources. These now include fluoridated toothpastes and mouthwashes, which are widely used. In addition, there have been suggestions that adding fluoride to drinking water can produce adverse health effects, and that the environmental risks of the most common fluoridating agents have not been fully assessed.
Concentration of fluoride in groundwater in the EU is generally low, but there can be large variation in the levels in natural drinking water between and within countries. In Ireland, for example, levels vary between 0.01 parts per million (ppm), or mg/L and 5.8 ppm, in Finland between 0.1 and 3.0 mg/L and in Germany between 0.1 and 1.1 mg/L.
In Europe, Ireland and some regions in Spain and the UK currently add fluoride to drinking water, at levels ranging from 0.2 to 1.2 mg/L.
People’s exposure to fluoride varies a lot, depending on levels in water, what toothpaste they use, and other factors like use of mineral water and some kinds of tea. The existing collection of risk assessments suggests that there is quite a narrow gap between the fluoride intake recommended to safeguard teeth and the maximum recommended exposure.
In Europe, exposure assessments have been made by the European Food Safety Authority (EFSA). The Authority has set upper tolerable intake levels related to levels in natural mineral waters and other common sources of fluoride. The Commission Scientific Committee on Consumer Products has also set levels for fluoride in dental products.
As questions continue to be asked about water fluoridation in countries where it is added to the water supply, the Commission asked the Scientific Committee on Health and Environmental Risks (SCHER) for updated advice on the latest research findings.
This report reviews these findings and assesses the risks and benefits of fluoridation in the light of estimates of fluoride intake by different groups of people.
All the important intake of fluorine is by mouth. People are exposed to fluorine in several different forms. In particular, the chemicals used to add fluoride to drinking water include hexafluorosilicic acid and hexafluorosilicates. Under normal conditions, however, these release all their fluorine as fluoride ions in solution. People are also be exposed to fluoride from its natural occurrence in drinking water.
Water used for washing may also contain fluoride. There is no data on fluoride absorption through the skin, but the fluoride ion will not readily pass through the skin and this pathway is not likely to contribute to people’s fluoride intake.
There is no proved absorption in the mouth. When swallowed, fluoride is absorbed via the stomach and intestines, and passes rapidly round the body in the bloodstream. Peak blood levels appear in 30-60 minutes after swallowing. The most soluble fluoride compounds, such as sodium fluoride in water, tablets and toothpaste, are almost completely absorbed. The less soluble compounds with calcium, magnesium or aluminium are less well absorbed.
Once in the blood, fluoride is gradually removed via the kidneys, reducing to half its original level in between three and ten hours. The long-term blood level is influenced by daily exposure as well as by take-up in growing bone and release as old bone is broken down. Children clear fluoride about as rapidly as adults.
3.1 What is the evidence regarding dental fluorosis?
Absorbing too much fluoride can impair normal development of enamel in teeth before they erupt, and the effects may not be visible until 4-5 years after exposure. They include white streaks on the enamel surface and, in more severe cases, porous areas of enamel, pitting and discolouration of the tooth surface.
Development of fluorosis depends on the dose, duration and timing of fluoride exposure while tooth enamel is forming. It is not known exactly how fluoride affects mineralization of the enamel. No threshold has been detected for risk of dental fluorosis in children exposed to fluoride which enters the body. However, the EFSA panel considered that an intake of less than 0.1 mg of fluoride per kilogram of body weight, per day, led to no significant incidence of “moderate” fluorosis in permanent teeth.
Fluorosis can occur in areas with fluoridated water, and also in those without. Fluoride supplements and use of fluoridated toothpaste, in large amounts, also increase the risk.
3.2 What is the evidence regarding skeletal fluorosis?
Fluoride can be incorporated into the mineral structure of bones, and in large amounts leads to a weaker bone matrix. Skeletal fluorosis results from long-term exposure to high levels of fluoride, and can have crippling results. It has been found in some parts of India, China and Africa where fluoride intake is exceptionally high. This is due either to fluoride in drinking water reaching unusually high levels or to burning fluoride-rich coal in confined spaces.
In Europe, skeletal fluorosis has only been seen in workers in mineral processing industries. It has not been seen in the general population.
Children under a year old incorporate up to 90 per cent of ingested fluoride into bone, and the percentage slowly decreases to 50 per cent incorporation by the time they are 15. Epidemiological studies have revealed no clear association of bone fracture risk with water fluoridation. There may even be a slightly lower fracture risk at low levels of fluoridation (0.6 to 1.1 mg/L). SCHER concludes that there is not enough data to evaluate the risk of bone fracture at the fluoride levels seen in areas with fluoridated water.
3.3 What is the evidence regarding osteosarcoma?
Epidemiological studies have not produced any strong evidence of carcinogenic effects. Concerns about possible cancer-causing effects of fluoride have focused on bone cancer because fluoride accumulates in bone. However, bone cancer, or osteosarcoma, is rare, making epidemiological studies more difficult to do.
On reviewing the most recent studies, the SCHER concludes that epidemiological work does not indicate a clear link between fluoride in drinking water and any cancers. Nor is there evidence from animal studies to support such a link. Fluoride should therefore be classified as non-carcinogenic.
3.4 What is the evidence regarding neurological effects?
Animal studies show little or no effect of fluoride on brain or behaviour, even at very high doses, hundreds of times above those received by people drinking fluoridated water.
Human studies do not suggest adverse thyroid effects at realistic human exposures to fluoride.
Some studies of developmental effects of human fluoride consumption in China suggested that high fluoride intake was linked with lower mean IQs in schoolchildren. However, these studies were poorly controlled, and the results may be due to other factors affecting these populations, such as iodine or lead intake, diet or other social factors.
The SCHER concludes that there is no clear evidence that fluoride in drinking water at concentrations permitted in the EU may reduce children’s IQ, and that there is no biological basis for thinking that this would occur.
3.5 What is the evidence regarding effects on human reproduction?
Animal studies in this area are of limited quality, but multi-generation studies on mice show no reproductive toxicity of fluoride even at very high doses. There is no new evidence from human studies that fluoride in drinking water influences male or female reproduction. A few human studies have suggested that fluoride might affect reproductive hormones, but they are poorly designed for risk evaluation. SCHER concludes that fluoride in drinking water at concentrations permitted in the EU has no reproductive effects.
Most fluorides in rock and soil are insoluble. Some soluble fluoride is found in ground and surface water. Levels of naturally occurring fluoride in drinking water vary widely between and within EU member states.
Surveys suggest that in Europe adult consumption of tap-water and drinks containing water varies by a factor of five. Data on children’s consumption is sparse.
Bottled mineral water commonly has higher fluoride levels than artificially fluoridated drinking water, but should not exceed 5mg/L of fluoride. Consumption of mineral water also varies widely.
Fluoride intake in food is low, unless its preparation uses fluoridated water or salt. Tea-drinkers may take in more fluoride, depending on their choice of tea. There are no new EU data on fluoride in food. The EFSA used German background exposure from food based on intake of milk, meat, fish, eggs, cereals, vegetables, potatoes and fruit. This assessment gave fluoride intakes of 0.042, 0.114, and 0120 mg/day for young children, older children and adults.
The other main fluoride intake is from toothpaste, mouthwashes and dental gels, which may contain up to 1500 mg/L of fluoride. Assessing how much fluoride intake follows is difficult as it depends on assumptions about how much toothpaste is spat out again, and how much is swallowed, and whether people use the right amount when they brush. A full brush load has around three times as much toothpaste as the recommended “pea-sized” amount. Adults probably swallow around 10 per cent of what they squeeze onto their toothbrush. Most children have got their swallowing down to this level by the age of 8, but younger children tend to swallow much more, up to 48 per cent in 2-3 year-olds.
There are also contributions, in some cases, from prescribed fluoride supplements, and from dietary supplements and fluoridated salts.
The SCHER pulled all these estimates together to compile scenarios for total exposure to fluoride from all sources. These substitute for precise population measurements, and take account of what we know of concentrations in drinking water in different regions, food and drink consumption, toothpaste use, and so on. The scenarios were used to identify who might be at risk of exceeding the tolerable fluoride dose.
For example, for adults and children over 15, the scenarios plot variations in water consumption, fluoride levels in water, and toothpaste use. In most scenarios, fluoride in drinking water dominates the total. The totals calculated indicate that the upper tolerable intake limit for adults and children over 15 (7 mg/day) is only exceeded in areas with high natural levels of natural fluoride in water, and where people drink 2,800 ml of water a day. If they use normal amounts of toothpaste, they are taking in 8.85 mg/day of fluoride, and the figure rises to 9.00 mg/day if their toothpaste use is high.
The scenarios suggest that the tolerable limit is not exceeded in areas with artificially fluoridated drinking water, which has a good deal less fluoride than is found in the regions with the highest naturally occurring levels.
The situation for children is rather different. The assessment covered three age groups – 12-15 years, 6-12 years and 1-6 years, and had to make more assumptions because of lack of data. In the SCHER scenarios, it was difficult for children 12-15 years old to exceed their maximum tolerable intake of fluoride unless they drank 1.5 litres of water containing 3.0 mg/L and used more than the recommended amount of a high fluoride toothpaste. A few might also exceed the dose by using fluoridated salt on their meals or drinking high fluoride mineral water.
For the under 12s, the risks were greater. For 6-12 year-olds, the SCHER used a tolerable intake of 2.5 mg/day, based on a figure estimated to give a prevalence of below 5 per cent of moderate fluorosis in 4-8 year-olds. This could be exceeded if they drank 1.5 litres of water containing 1.5 mg/L of fluoride, no matter how careful they were about swallowing toothpaste.
Still younger children, 1-6 years old, swallow more toothpaste, and can exceed a maximum tolerable dose set at 1.5 mg/day of fluoride at fluoride levels in drinking water as low as 0.8 mg/L. If they drink enough, they may even exceed this level without using toothpaste at all.
Both water fluoridation and application of fluoride directly to the teeth and gums, for example using fluoridated toothpaste or varnish, can prevent tooth decay. Fluoride is incorporated into the tooth enamel while teeth are growing, and this reduces decay later on when teeth have erupted. The preventive effect is most important for the permanent, adult teeth. There is no clear advantage of water fluoridation over direct application for prevention, and systemic exposure via drinking water is unlikely to benefit people whose teeth have already grown. Europe-wide trends show a reduction in tooth decay in 12 year-olds regardless of whether water is fluoridated or not.
In children, there is a very narrow margin between the beneficial effects of reducing decay and exceeding the dose which causes dental fluorosis.
There is some evidence to support the idea that population-wide administration of fluoride, by adding it to drinking water, milk or salt, can reduce social inequalities in dental health. At the moment, children from lower socio-economic groups tends to have more tooth decay, and to benefit more from water fluoridation. However, the overall weight of evidence is not enough to substantiate the idea that water fluoridation is the best way to tackle social inequalities in dental health.
6. What further investigations are needed to improve assessment of exposure and of the health effects of fluoride?
Exposure assessment is the most important element of additional research. In particular, information about health effects of fluoride beyond fluorosis, such as bone cancer and neurological and reproductive effects, is poor quality, with inaccurate exposure measurements and observed effects only at very high exposure levels.
Improving risk assessment requires:
1. Development and validation of new biomarkers for direct measurement of long-term fluoride exposure.
2. Development of standardized methods for exposure assessment, integrating all routes of exposure.
3. Better information on fluoride in food.
4. Epidemiological studies to refine data on fluoride, dental fluorosis and dental health.
The committee considered environmental exposures from use of fluoridated water as drinking water, And other domestic uses. This will pass into the environment via drainage and sewage treatment. Most fluoride remains in solution, so the solid component of sewage sludge passes little fluoride onto land, or into the atmosphere when it is incinerated. The properties of the fluoride ion also mean that little of the fluoride which passes into waterways and lakes enters sediment. This means its effects are largely confined to water-dwelling organisms in aquatic ecosystems.
As the question posed relates specifically to artificial fluoridation, it is assumed this will not entail raising any water levels above those defined as legal limits for fluoridation – 1.5 mg/L in the EU and 0.8 mg/L in Ireland.
Reviews of studies on effects of fluoride on aquatic organisms suggest that the most sensitive organisms, marine invertebrates, may feel some adverse effect at 2.9 mg/L fluoride or above. This leads to setting a Predicted No Effect Concentration (PNEC), with a factor of ten as a safety margin, pf 0.29 mg/L.
The question the is whether a typical artificial fluoridation level, taken as 1.0 mg/L, will be diluted enough in water treatment to fall below this threshold. This is extremely plausible in most circumstances.
On the basis of this, and other calculations and modelling, the SCHER is of the opinion that adding fluoride to drinking water does not result in unacceptable risk to water-dwelling life.
The 2011 SCHER report on fluoridation is online at http://fluoridealert.org/wp-content/uploads/eu.scher-report.fluoridation.2011.pdf
Level 2 details online at https://ec.europa.eu/health/scientific_committees/opinions_layman/fluoridation/en/l-2/1.htm#0