New research found ‘significant inverse associations’ between fluoride exposure and children’s IQ scores, calling the safety of water fluoridation into question.
The study estimates that for every 1mg/L increase in urinary fluoride, a child’s IQ decreases by 1.63 points. Lead author Kyla Taylor said this is a ‘statistically significant association’ between fluoride exposure and lowered IQ scores.
In August, the same researchers from the National Institute of Environmental Health Sciences helped to develop a US government report which determined ‘with moderate confidence’ that there is an association between high levels of fluoride exposure and decreased IQ.
The National Toxicology Program report focused on a fluoride concentration twice the recommended limit in water. However the new research suggests that fluoride concentrations below 1.5mg/L (currently considered to be the safe limit by the World Health Organization) may also impact childhood IQ.
It is unclear from the study whether the currently recommended fluoridation level of 0.7mg/L was associated with adverse effects.
Limitations
Several limitations of the study were identified by its authors. For example, they rated 52 of the 74 studies included in the review as ‘low quality’ with a ‘high risk of bias’.
Speaking to AFP, American Dental Association representative Steven Levy said the apparent association was likely caused by ‘confounding factors’ such as coal pollution in China. He said: ‘Almost all of the studies have been done in other settings where there are other contaminants.’
Levy also said that government policies on water fluoridation ‘should not be affected by the study findings’.
Professor Grant McIntyre, dean of the Faculty of Dental Surgery at the Royal College of Surgeons of Edinburgh, said the study ‘should not be regarded as providing any proof that fluoridation in water is harmful’. He said: ‘On the contrary, there is overwhelming evidence to show that fluoridation has huge public health benefits.’
He continued: ‘Fluoride is a naturally occurring mineral found in soil, food and drink, and also in drinking water supplies that helps restore minerals lost to acid breakdown in teeth, reduces acid production by cavity-causing bacteria, and makes it harder for these bacteria to stick to the teeth.
‘In some parts of England, local geology means the level of fluoride in public water is already at the level (1mg/l) that fluoridation schemes run at. This, one should note, is well below the World Health Organization’s safety limit of 1.5mg/l.
‘Public Health England estimate that if all five-year-olds in England drinking water with 0.2mg/l of fluoride instead received fluoridated water of at least 0.7mg/l, then the number experiencing decay would fall by 17% in the least deprived areas, rising to 28% in the most deprived areas.
‘We are confident that fluoridation is safe and has significant benefits to public health in reducing tooth decay, particularly in more deprived areas. Indeed, a further benefit of water fluoridation over other approaches is that it does not rely on behaviour change, which is particularly important for children and vulnerable groups.’
Will water fluoridation be expanded in the UK?
In February 2024, the former Conservative government’s dental recovery plan included plans for a water fluoridation programme following a consultation. The consultation paper says: ‘On balance there is strong scientific evidence that water fluoridation is an effective public health intervention for reducing the prevalence of tooth decay and improving dental health equality across the UK.’
It also says that ‘the overall weight of evidence and authoritative reviews of a large body of relevant and suitable studies indicates that fluoride, at the levels permitted in drinking water, presents no risks to health’.
The consultation concluded in July 2024. In December, Baronness Gillian Merron confirmed that the Labour government had not made a final decision based on responses.
She said: ‘We are currently considering the responses to this consultation, and a decision on whether to expand the scheme will be announced in due course.’
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