A minor dental condition caused by fluoride in drinking water is associated with bone fractures, research has found.
Dental fluorosis, which makes teeth brittle and leads to unsightly mottling, is regarded as a cosmetic defect rather than a serious health problem. But research now suggests that it may be a marker for bone disease.
Researchers studied the teeth of children living in the Guadiana Valley of northwest Mexico where the drinking water comes from underground wells and is characterised by a high content of fluoride. They found that the children suffered from high levels of dental fluorosis but also that the levels of fluorosis corresponded with the levels of bone fractures.
The research, published in the journal Fluoride, concludes: ‘A higher risk of increased dental damage is directly related to persons living in areas with higher fluoride levels in their drinking water. A positive correlation between the index of dental fluorosis and the occurrence of bone fractures also exists.’
Campaigners against adding fluoride to tap water insist the study shows that too much fluoride can cause bone damage as well as dental fluorosis.
Paul Connett, professor of chemistry at St Lawrence University in New York and a founding member of the Fluoride Action Network, said: ‘Far from dental fluorosis being an inconvenient cosmetic problem, it may be an indicator of bone damage. What we need to know is how much fluoride is being deposited in our bones. Sadly, there is a glaring absence of such data.
‘What is striking is that bone damage is occurring in clinical studies at cumulative doses well within the current estimates for how much fluoride people living in fluoridated areas will be receiving in their lifetimes.’
The study found that in areas of the Mexican valley with fluoride concentrations higher than 12mg per litre, all children surveyed exhibited dental fluorosis and 35% of them had suffered serious damage to their teeth. But even where levels were around 1.5mg per litre, 76% of children had some degree of dental fluorosis.
According to the World Health Organisation, the fluoride level in water should be within 1.5mg per litre. But Dr Paul Harrison, acting director of the Medical Research Council (MRC) Institute for Environment and Health and chair of the MRC working group on fluoride, pointed out that the levels of fluoride occurring naturally in the Mexican wells were significantly higher than those added to domestic water supplies.
‘I don’t think we can say from this study that dental fluorosis is a marker for bone disease. We would only be able to say that if only the people with bone disease had dental fluorosis.
‘It all depends on the dose of fluoride. If you absorb enough fluoride it can become dangerous — it does cause mottled teeth and there is an issue over bone damage. The limit of fluoride in water in this country is one milligram per litre, however. It is not clear that there is any effect at that level.’
Last month the MRC group chaired by Harrison recommended further research into the health effects of water fluoridation. The research will compare how much of the element the body takes in where it occurs naturally and where it has been artificially added.
‘There’s no reason to think that water fluoridation is responsible for any adverse health effects. But there is a lack of research on some important aspects, which is why we’re highlighting the need for more research.
‘Because of the wide use of toothpastes and other dental healthcare products containing fluoride, we need a better understanding of how much fluoride we’re all absorbing,’ he said.
The Scottish Executive has launched a public consultation on adding fluoride to drinking water and insists no decision has yet been taken.
Controversy has raged for years around the issue, which is fiercely opposed by environmentalists and some consumer groups, but supported as a way of improving dental health in deprived communities by most doctors and dentists.