A 50-year-old medical controversy is about to be re-ignited. The government is considering the introduction of further fluoridation schemes throughout the country. To facilitate that, the Water Act passed last November indemnified water companies from civil or criminal actions as a result of adding fluoride to public water supplies.

Fluoridation was first advanced in the United States at the end of the second world war. Proponents argued that fluoride in water and toothpaste would help to protect teeth and prevent decay. It was a time of scientific evangelism, when chemicals meant progress and the public trusted them to bring about a safer, cleaner future.

Throughout the 1950s and 60s, fluoride was added to public water supplies not just across the US but also in Britain. The areas now served by the Severn Trent, Northumbrian and Anglian water companies are fluoridated, mainly those in the West Midlands and Tyneside – about 10% of the UK population. Much of the Republic of Ireland has been fluoridated since 1964.

As dental health rapidly improved during those decades, so the benefits of fluoridation were held to be incontestable. However, with better diet and treatment, dental health was improving across the western world, irrespective of fluoridation. Recent studies of communities in Finland, Cuba, Canada and east Germany have found that rates of dental decay did not rise (and, indeed, continued to decline) after fluoridation was abandoned. Fluoridation today is largely restricted to English-speaking countries.

Many believe that the effects of fluoride on teeth, beneficial or otherwise, are irrelevant; what matters is the accumulating research evidence that fluoride may have serious adverse health effects. However, the government wanted to extend fluoridation schemes, ostensibly to benefit those in poorer areas. So, it set up the York Review to allow leading scientists to examine the issue. One of the review’s conclusions in September 2000 was that there had been “surprisingly” little research into fluoride’s harmful effects, and emphasised the need for “high-quality research”, specifically into the possible links between fluoride and “infant mortality, congenital defects and IQ”.

A subsequent inquiry into fluoridation by the Medical Research Council recommended an updated analysis of data on fluoride and cancer rates, but concluded that “there is no evidence for any significant health effects on the immune system, or reproductive and developmental (birth) defects and no specific research is recommended, although it is appropriate to keep the area under review.”

Now, a new book, The Fluoride Deception by Christopher Bryson, just published in the US, examines the background of the fluoridation debate. Bryson, who has had the advantage of access to recently declassified files, concludes that fluoridation is a triumph not of medical science but of US government spin, adding that, “The very same professionals and institutions who told us that fluoride was safe said much the same about lead, asbestos or DDT, or persuaded us to smoke more cigarettes.”

In fact, in the 1930s, the very first researcher into fluoride, a Dane called Kaj Roholm, specifically advised against exposing children to fluoride, but his work was soon buried. Bryson links the subsequent “discovery” that fluoride benefited teeth with research paid for by major US industries that needed to be able to defend “lawsuits from workers and communities poisoned by industrial fluoride emissions”.

In 1955, farmers in Oregon took Reynolds Metals to court, alleging harm from fluoride emissions. The key medical experts for the farmers were Donald Hunter, an English specialist in industrial diseases, who told the court that fluoride was particularly dangerous because it was “an enzyme poison”; and Dr Richard Capps from Chicago, who gave evidence that fluoride displaced iodine in the body, thus leading to thyroid dysfunction. The farmers won a sensational victory, and US industrialists were shaken. Dr Robert Kehoe, whose work was funded by major US companies, resolved – according to Bryson – to create a new medical orthodoxy that would be unassailable in future court cases. Kehoe set up an experiment with beagles, with the dogs breathing in fluoride. The results were alarming, and showed that fluoride travelled rapidly from the lungs into the blood stream, causing significant harm. Lawyers for major US companies received copies of the dog study; needless to say, it went no further. Until Bryson found it, no one knew of its existence.

The drive to encourage public acceptance of fluoride was handed over to Edward Bernays, known as the father of PR, or the original spin doctor, and the man who helped persuade women to take up smoking. “You can get practically any idea accepted,” Bernays explained, “if doctors are in favour. The public is willing to accept it because a doctor is an authority to most people, regardless of how much he knows or doesn’t know.”

Among the things that the doctors who endorsed fluoridation didn’t know, according to Bryson, were that research impugning fluoride’s safety was either suppressed or not conducted in the first place. When one doctor reported that fluoride supplements produced harmful side-effects in pregnant women, he received no funding to carry out further work.

So fluoride became equated with scientific progress, and those opposing it were dismissed as cranks. For 30 years, little changed, with both sides in their entrenched positions.

Yet putting fluoride into the water supply – at what the Department of Health considers to be the “safe” level of one part per million – would, according to opponents in the UK, appear to ignore some important considerations. First, they say it does not allow for individual sensitivities to fluoride. Second, those suffering dietary deficiencies, who may be low in calcium, magnesium and essential nutrients (in other words, the poor and those in ill-health), will be more vulnerable to fluoride’s toxic properties. Third, the level of fluoride in the water supply is no indication of an individual’s actual exposure. Those in certain professions – for example, labourers or athletes – will take in more water, and therefore more fluoride.

Also, there is regular exposure from other sources – fluoride toothpaste, of course, as well as pesticide residues and pharmaceuticals. In 1994, the World Health Organisation recommended that public health administrators should be aware of “the total fluoride exposure in the population”. In fact, in Britain during the past 30 years, anti-fluoridation campaigners claim that the public’s overall exposure to fluoride has become much greater, while the government’s ostensible “safe” limit has remained exactly the same.

They say that two of the major concerns in childhood development today could be explained by fluoride. If it interferes with the central nervous system, as some studies have shown, then that could help to explain the growing prevalence of Attention-Deficit Hyperactivity Disorder.

There is also concern that fluoride displaces iodine in the human body. Iodine is essential for normal functioning of the thyroid gland. If fluoride, by displacing iodine, does inhibit thyroid activity, then that would lead to weight gain and obesity.

Moreover, iodine is essential for brain development. There are now epidemiological studies from China that link fluoride exposure with lower IQ levels. After Dr Phyllis Mullinex, a leading neurotoxicologist in Boston, had carried out work on rats, she reported that fluoride was likely to lead to lower IQs. She was fired.

Bryson believes that what has made fluoride so impervious to criticism so far is not just the PR offensive, but also – paradoxically – fluoride’s overall toxicity. Unlike chemicals that have a signature effect (like the mesothelioma caused byasbestos), fluoride is, he says, “a systemic poison, likely to produce a range of health problems”, so that its effects are harder to diagnose.

“We’ve known about all this for a long time,” says Jane Jones of the National Pure Water Association, which campaigns against fluoride, “now I hope the wider public will sit up and take notice”.

There are many in the UK who support the fluoridation of our water supply, among them Ian Wylie, chief executive of the British Dental Association, who argued in this paper recently: “Scientific opinion worldwide is that low-dose fluoride has a beneficial effect on oral health. In America, almost two-thirds of the population has drunk water with fluoride, without a problem, for decades.”

The government has promised that no further fluoridation schemes will be implemented without public consultations beforehand. The debate is likely to be fierce and prolonged.

· The Fluoride Deception is available in this country through Turnaround Distributors.