Fluoride in water increases risk of thyroid illness ‘by 30 per cent’

The findings have prompted researchers to call for a rethink of public health policy to fluoridate water supplies to improve dental health.

In England, around 10 per cent of the population, including people in parts of northern Lincolnshire, live in areas with a naturally or artificially fluoridated water supply of 1mg fluoride per litre of drinking water.

Researchers from Kent University looked at fluoride levels in drinking water supplied in 2012 and compared it with the prevalence of underactive thyroid, also known as hypothyroidism, diagnosed by 8,000 GP practices over the period, carrying out a second analysis comparing levels in the West Midlands, where water is fluoridated, with cases in Greater Manchester, where it is not.

The study, published online in the Journal of Epidemiology & Community Health, said there was a link between fluoridation and rates of the condition.

In areas with fluoride levels above 0.7 mg/l, they found higher than expected rates of hypothyroidism than in areas with levels below this dilution.

High rates of hypothyroidism were at least 30 per cent more likely in practices located in areas with fluoride levels in excess of 0.3 mg/l.

Practices in the West Midlands were nearly twice as likely to report high rates of hypothyroidism as those in Greater Manchester.

Researchers said their findings echo those of previous research.

They added: “Consideration needs to be given to reducing fluoride exposure, and public dental health interventions should stop (those) reliant on ingested fluoride and switch to topical fluoride-based and non-fluoride-based interventions.”

Jenny Godson, Public Health England’s (PHE’s) consultant in dental public health for the north of England said: “The totality of evidence, accumulated over decades of research, tells us that water fluoridation is a safe and effective public health measure, and shows no association with reduced thyroid function.

“PHE’s own assessment of water fluoridation programmes in England found evidence of lower tooth decay rates in children living in fluoridated compared to non-fluoridated areas, and greater reductions among those living in the most deprived areas.”

The British Dental Association’s scientific adviser Prof Damien Walmsley said: “In any debate on this subject, we mustn’t forget that fluoridation has a proven benefit in reducing high rates of tooth decay, particularly among those living in the most deprived communities.

“Research suggests that children living in fluoridated areas, such as the West Midlands, have around half the rate of tooth decay of those living in non-fluoridated areas, such as the North West - this means every year many thousands of children are spared the pain and distress of tooth decay, or the trauma of having to be admitted to hospital to have decayed teeth removed under a general anaesthetic.”

The issue has sparked an outcry in East Yorkshire where hundreds of people have signed petitions against fluoridation following calls by council leaders in Hull to introduce the measure to tackle high rates of tooth decay in the city amid evidence around 43.4 per cent of five-year-olds suffer from it.