Health Secretary Alan Johnson is calling for fluoride to be added to England's water supplies in the hope of reducing tooth decay among some of society's poorest and most vulnerable.
By Clare Murphy
Health reporter, BBC News
He may be ok, but apparently some children don't own a toothbrush
For a public which has grown accustomed to health interventions - from seat belts to smoking bans - it may seem curious that such a laudable aim could prove so contentious.
But fluoridation strikes a particular ethical nerve. While the smoker can still nip outside for his cigarette, no-one can escape regulations which alter the water they drink.
To its critics it is forced, mass medication, the sure benefits of which may pale in comparison to the uncertain consequences - including cancer, infertility and Down's Syndrome.
To its advocates, fluoridation is one of the most effective ways of achieving equality in dental health, and giving the poorer child's teeth a chance to sparkle like those of his middle-class counterpart.
Not for you
It may be controversial, but it isn't new.
Naturally found in tea
350m receive fluoridated water worldwide
70% of US water fluoridated
Added to water at one part per million (1 ppm)
The benefits were first suggested by US researchers in the 1930s, who compared tooth decay in areas with different levels of natural occurring fluoride in the water.
Grand Rapids, Michigan, became the first city to add the chemical to its water supply in 1945, and other areas quickly followed suit.
In 1955, pilot schemes were launched in Watford, Kilmarnock and Anglesey. The first evaluation report in 1962 was positive, and Birmingham was among the first cities to make the shift, a policy still in operation today.
It spread - today there are six million people, around 10% of the population, with fluoridated water supplies - but momentum was trailing off by the 1980s. It was last implemented in 1985.
Despite new legislation in 2003 which gave Strategic Health Authorities (SHAs) the power to ensure a supplier adds fluoride to a water supply, none of the authorities have made use of this provision.
"And it's really time they did," says Professor Mike Lennon, chairman of the British Fluoridation Society, "because the benefits of doing so are now beyond doubt.
"Of course this isn't for everyone - it won't be necessary in the wealthier home counties for instance.
"But if Manchester started doing this, they could get child tooth decay levels in line with Birmingham, where kids are twice as less likely to have fillings.
"If we get supplies up from 10% to 30%, say, we would really be getting somewhere."
Indeed, no-one seriously doubts that fluoridation does stop decay. But there is some dispute over the extent to which cavities are prevented.
The most recent, major review of the evidence was carried out at the University of York, and published in 2000.
They examined 30 studies, of which 12 had not detected a statistically significant differences between cavities in those receiving fluoridated and non-fluoridated, and where there were even examples of an increase in decay.
But other studies told a completely different story, and researchers said that on average, adding the chemical to water may lead to an additional 14.6% of children without holes in their teeth.
They did however find a increase in fluorosis - or mottled teeth - which can in severe cases have a profound psychological impact on the child concerned.
They found no link between fluoridation and other diseases such as cancer or bone fracture or to conditions such as Down's Syndromes - staple claims of many anti-fluoride campaigners. But they did stress that "not enough was known, because the quality of evidence was poor".
The report was jumped on by both sides as grist for their respective mills, and a few years later the authors made a public statement expressing their concerns about the "continuing misinterpretation of the evidence".
Choosing my water
The review did not, in any event, cast judgement on the ethics of adding fluoride to water, and whether doing so somehow violated a person's right to make choices about what they consume.
The National Pure Water Association is clear about the implications: "By presenting fluoridation as a means of preventing tooth decay, Alan Johnson confirms the practice is medication. Fluoridation is carried out by water companies in violation of their customers' human right to refuse consent to any medical intervention."
But, the pro-fluoride lobby notes, water is already extensively tampered with. Chlorine, for instance, is added to keep it free of bacteria and so prevent us from falling ill when we consume it.
True enough, say the thinkers at the Nuffield Council on Bioethics, who have recently gathered their thoughts on the subject. But, they continue, chlorine is added to make water safe, while fluoride would be added for an entirely unrelated purpose.
There are ways of boosting fluoride intake without making it effectively compulsory. Switzerland, for instance, offers fluoridated salt, which is on sale with non-affected products, so consumers have a choice. Studies suggest this has reduced cavities by as much as 30%.
But regardless of whether, in the UK, those who need the mineral most would buy the product, there would be health issues around having fluoride in your water as well as your salt, as would be the case in some areas.
In order to introduce fluoridation in any area, an SHA is required to hold a public consultation. This would involve printing details in at least one local newspaper to solicit views from those affected, as well as liaising with local authorities.
HAVE YOUR SAY
"The problem with these kind of consultations is that they very rarely spark genuine public debate, and the information people receive tends to be heavily biased one way or another," says Nick Reeves, head of the Chartered Institution for Water and Environmental Management.
If the government want to improve the state of people's teeth they should be providing free NHS dental care for everyone
"It would be far better to make sure everyone has free and equal access to dental care, before starting on something which the scientists are in case not agreed on, and which has real moral implications."
Professor Lennon agrees that the issue is an ethical one above all else.
"Because this is about asking people to look beyond themselves and ask not just what's best for my child, but what's best for my neighbour's child. It's a genuine moral debate."