The safety limit of Fluoridation

For more than four decades, Heath authorities all over the world have generally held the view that the fluoridation of community water supplies is totally safe and highly effective in reducing the incidence of tooth decay, particularly in children. It was believed that only a few uneducated persons were opposed to fluoridation.

Now, however, a controversy is hotting up. According to one view expressed in the prestigious scientific journal Science, the widespread use of fluorides may have created a situation in which we are approaching a critical mass of fluoride in the environment. It is feared that some serious conditions like genetic damage, birth defects, allergy response and even cancer may arise from ‘fluoride interference’.

In the last few years, new evidence has been unearthed to indicate that individuals are now receiving fluoride from an increased number of sources and that too much fluoride can indeed be harmful. In heavily fluoridated countries like Australia, America and Britain where 70 per cent of the population drink ‘treated’ water, some scientists are of the view that, through the agency of the strong hydrogen bond, fluoride can change the chemistry of many compounds, though what it may be capable of doing in the living cell, whether for good or ill, is still not known.

There are two reasons for the present controversy over fluoridation.

First, people are now ingesting fluoride from a variety of everyday sources including water, food, dental health products such as fluoride toothpaste, medicines, pesticide and insecticide residues and even the air we breathe. Thus, the amounts received by the individual cannot be controlled.

Secondly, in the end of the last century, scientists at Sweden who found simple and reliable ways of measuring blood levels of fluoride noticed that, contrary to popular conception, even minute dosages of fluoride could cause blood levels to peak to potentially harmful ones.

Many researchers have long been intrigued by the idea of adding a known toxic substance to water supplies to reduce cavities in teeth. For, unlike chlorine which treats the water, fluoride is added to influence a physiological process—the mineralization of teeth.

Veterinary doctors, horticulturists and environmental experts have known for more than half a century that fluoride at very low concentrations can damage vegetation and livestock. Industrial and structural chemists have learnt to expect the unexpected from this unpredictable element; and biochemists, physiologists and toxicologists all recognise fluoride as a potent enzyme poison. Yet, ironically, many health experts continue to argue that artificial fluoridation and the use of a range of dental health products containing fluoride are not only safe but provide the most effective way of preventing tooth decay.

Despite more than 50 years of tests and trials, fluoridation has been adopted in only a handful of countries around the world. Authorities in Germany, France, Sweden, Denmark, Holland and Japan remain unconvinced about its safety and effectiveness, while the authorities in Australia, America and Britain are satisfied that the benefits outweigh the risks. What does one do in the face of such a disagreement?

Now evidence regarding the action of fluoride on human cells and tissues is emerging all the time. While the powerful hydrogen- bonding capacity of fluoride has been known for some time, its potential for interfering with vitally important hydrogen bonds between biomolecules has only recently begun to receive attention. About three decades ago some scientists in the United States found a new strong hydrogen bond which was formed between fluorides and amides— organic salts of ammonia. Many components within living cells contain amide groups; indeed the hydrogen bonds formed between amides are the most important weak hydrogen bonds in biological systems. That these can be disrupted by fluoride in the formation of much stronger bonds may explain how the chemically inert fluoride ion could interfere with the healthy operation of living systems.

Most scientists would probably agree that fluoride can be harmful but the question is: at what concentration does it become poisonous in the human body? One established effect is ‘fluorosis’ or permanent mottling of the teeth. Experiments conducted on rats have revealed that blood fluoride levels of 0.2 parts per million cause dental fluorosis or damage to developing tooth cells; and rats are between one- seventh to one-tenth less sensitive to fluoride than humans. Researchers have also shown that growth in rats is retarded at blood fluoride concentrations of 0.3 ppm and serious toxic effects develop at one part per million. Therefore, the vital factor does not concern the fluoride level in a community water supply, but rather whether or not fluoridation increases the risk that certain people could, for a very short time, experience blood fluoride levels which can damage human cells and systems. Can fluoridation to a level one part per million together with the regular use of fluoride containing dental health products and the ingestion of fluoride in processed food and beverages lead to a total intake, sufficient to cause normal blood fluoride levels to peak to potentially harmful ones? Some supporters of fluoridation believe this cannot happen, citing the result of an experiment conducted which showed that a mechanism exists in the body to ensure stability of blood fluoride levels no matter what the intake. But the experiment has since been proved wrong. It is now known that fluoride ingested in two ways will influence blood fluoride levels: (a) fluoride in drinking water: in this the fluoride is greatly diluted and (b) sub-milligram dosages of fluoride in foods, dental health products, medicines, insecticide residues or dusts and particulates contaminated with fluoride.

When eartificial fluoridation was first commenced, it was envisaged that all children would drink about one litre of water a day, thus their daily intake would be around 1 mg; now the child gets fluoride from water and from an increasing number of other sources. One Swedish scientist showed that when a healthy adult male weighing 60 kg swallowed 10 mg of fluoride, the blood level peaked after about an hour to just over 0.4 parts per million. As this represented a dosage level of 0.166 mg fluoride per kilogram body weight, the equivalent dosage needed to achieve similar peaks in a 10 kg infant and a 20 kg child would be 1.66 mg and 3.33 mg fluoride, respectively.

Scientists are now aware that fluoride dose levels recommended about two decades ago are too high and many other factors must be taken into account such as the natural fluoride level in the water supply, the age of the patient, the use of fluoride dentifrice and the ingestion of tea. Minute dose of fluoride can be ingested in several ways: from foodstuffs and drinks rich in fluoride such as sardines or tea. More than 90 per cent of toothpastes contain fluoride. A daily intake of excess 0.5 mg fluoride from this source alone is quite common. Many old practices like the use of fluoride tablets or drops from birth or the use of topical fluoride treatment in the form of acidulated gels in dental surgeries could result in harmful fluoride levels according to modern research.