Fluoride in the water linked to anxiety, temper problems and headaches in children as young as three, with experts claiming exposure high levels in pregnancy could be a 'risk to the developing brain'

Pregnant women exposed to high fluoride levels doubles the odds of having a child with a neurobehavioral problem, a new study suggests.

It comes as ministers plans to controversially add fluoride into the drinking water supplies of another 1.6million Brits in a bit to improve the nation's dental health.

American experts, who examined a group of just under 230 mother and child pairs, found those with higher fluoride levels in pregnancy had increased odds of having child with a neurobehavioral issue by the time their infant turned three. 

These issues included symptoms of anxiety and emotional regulation.

Children born to women with higher levels of fluoride in their urine were also more likely to report suffering headaches and stomach pain, the authors noted. 

It isn't clear what caused some women in the study to have higher fluoride levels than others. Drinking tap water versus filtered, consumption of certain foods and use of some dental products are potential causes of increased fluoride exposure.

Lead investigator Ashley Malin, an assistant professor in epidemiology at the University of Florida College of Public Health, said their findings suggested a relationship between fluoride exposure and foetal brain development.  

'There is no known benefit of fluoride consumption to the developing foetus, but we do know that there is possibly a risk to their developing brain,' she said.

'We found that each 0.68 milligram per litre increase in fluoride levels in the pregnant women’s urine was associated with nearly double the odds of children scoring in the clinical or borderline clinical range for neurobehavioral problems at age 3, based on their mother’s reporting.'

She added the findings were concerning and hoped they would inspire policymakers to create specific recommendations for fluoride exposure in pregnancy.

'Conducting a nationwide US study on this topic would be important, but I think the findings of the current study and recent studies from Canada and Mexico suggest that there is a real concern here,' she said.    

Fluoride is added to tap water in the US, much like in the UK, in a bid to help passively protect people's teeth, a process called fluoridation. 

The mineral helps strengthen the hard outer protective layer of teeth, called the enamel, which in turn protects teeth from damage and wear and tear, helping prevent tooth decay. 

Fluoridation is a controversial topic and has become a flashpoint issue in the US. 

Presidential hopeful Robert F. Kennedy Jr has even labelled it a 'neurotoxic' and vowing to remove it from drinking supplies if elected, although major scientific reviews have found 'no convincing evidence' it is unsafe, according to the NHS.

In their study, researchers, who published their findings in the journal Jama Network Open collected urine samples from women during their third trimester of pregnancy. 

Experts said they were careful to also measure exposure to lead, which is well-established to impact the development of children, in their analysis.

These results were then compared to a questionnaire mothers were asked to complete when their child turned three to assess their offspring's behaviour and emotions.

Investigators found women with higher fluoride exposure in pregnancy tended to rate their children higher for overall neurobehavioral problems. 

Researchers didn't provide the level of fluoride in tap water the women, who lived in Los Angeles, California, were exposed to but said it was 'typical' of those living in areas with fluoridation.

Some 5.8million Britons live in areas where fluoride - also added to toothpastes and mouthwashes - is placed in tap water, about a tenth of the population. 

However, there are Government plans to expand this to another 1.6million people in the North East. 

The 5.8 million figure doesn't include areas in the UK where water supplies are naturally high in fluoride, about 300,000 people drink supplies naturally fluoridated by rocks in the ground. 

Fluoridation is much more common in the US, with about 73 per cent of the population having the mineral added to their water supply at a concentration of about 0.7 mg per litre.

This is roughly half of the maximum 1.5mg of fluoride per litre allowed in Britain a level that wasn't breached by a public water supplier in 2022 according to official data.

The study had a number of limitations, some of which the authors acknowledge.

One factor is that the children's behaviour was self-reported by their mothers which may have influenced the results.

Additionally, the study is observational, meaning that investigators cannot directly prove fluoride exposure was the cause of the observed behaviours in children. 

The authors also note their study is from a primarily Hispanic group of women in one part of the US and, therefore, their findings may not be replicated in other populations. 

The latest study isn't the first time that alarms have been raised about adding fluoride to drinking water.

Some studies have linked excessive quantities of the mineral to babies being born with Down's syndrome, as well as kidney stones and some cancers. 

However, the NHS and experts like the Government's chief medical officer Sir Chris Whitty say these claims are not backed up by evidence.

Professor Whitty has previously described them as 'exaggerated and unevidenced'. 

Health bosses have estimated that adding fluoride to more water supplies in the UK could prevent two-thirds of hospital admissions for tooth decay, an issuing costing the NHS, and by extension the taxpayer, millions. 

In 2021, Professor Whitty and colleagues said if all five-year-olds with drinking water containing less than 0.2 milligram per litre (mg/l) of fluoride started drinking water boosted to 0.7 mg/l, the number with cavities would fall by up to 28 per cent among the poorest communities.

Plans to add fluoride to more water supplies comes at a time when access to NHS dentistry is increasingly difficult.

There are frequent accounts of parents of young children, who are entitled to free NHS dental care, being unable to get their kids appointments or having them cancelled last minute. 

Fluoridation is considered to be a low cost high impact public health initiative as it is passive and not reliant on people actively changing their behaviour compared to encouraging them to stop smoking, exercise more or eat healthier food.  

But some experts have argued that since fluoride is now added to a number of toothpastes and mouthwashes adding it to tap water is not as beneficial as it once was. 

While the more serious dangers of fluoridation are a point of contention, one minor risk that is known is fluorosis.

This where a child has too much fluoride while their teeth are developing, causing very white lines to appear on the tooth when mild and discolouration of the teeth when severe.

It is partly for this reason that the World Health Organization recommends that fluoride in drinking supply should not go above 1.5 mg/l.

The risk of fluorosis in the UK is considered low due because fluoride levels in drinking water are carefully monitored in Britain. 

Outlandish conspiracy theories touting fluoride as a plot by the global elite to depopulate the world or that it is being used for mind control purposes are frequently spread online. 

However, experts have repeatedly told MailOnline the levels in water supplies in the UK are not a health concern. 

About 25 countries around the world already add fluoride to tap water, including Ireland, the majority of the US and Australia.