Debate
Continued »
ingested fluoride accumulates in the skeleton, especially at sites of bone formation. Advanced (clinical Stage 3) skeletal fluorosis occurs in parts of India and elsewhere where fluoride is naturally present in the water at 5ppm or more – a devastating condition fortunately very rare in the west. The question mark for us hangs over the earlier clinical Stages 1 and 2, which manifest as aches and pains and later arthritis. The extent to which this may contribute to the spectrum of arthritic conditions in western countries is unknown18,19.
Carcinogenesis Related to its localisation in bone, fluori- dated water consumption specifically between the ages of five and eight has been implicated in the development of osteosarcoma in young men20. This was a carefully conducted case-control study that confirmed tentative suggestions from some earlier cross-sectional studies. Although ecological studies have mostly
failed to detect an association between osteosarcoma and fluoridation, that may well be due to the rarity of the disease and the relative weakness of cross-sectional investigations. So far there have not been any attempts to repeat Bassin’s work, or any convincing evidence to suggest that its conclusions were wrong, so it remains both biologically plausible and unrefuted. Fluoride has also been claimed to be a
more general carcinogen, but the evidence remains unconvincing. However, the silicofluorides commonly used for fluori- dation are contaminated with arsenic. A typical (USA) concentration of 30mg
As per kg of silicofluoride would be expected, assuming a linear carcinogenic dose-response relationship, to result in 2.7 extra cases of lung and bladder cancers per million people drinking the fluori- dated water21.
Thyroid and other organs Fluoride interferes with the activity of a large number of enzymes in vitro. Animal studies have indicated low-dose toxicity of fluoride to several organs and systems
“There are animal studies documenting damage to the brain,
especially during development”
including the kidneys and particularly the thyroid18. It is considered to be an endocrine disruptor18. There is as yet no compelling evidence that dietary fluoride intake can affect these organs in humans, but the possibility has received scant research attention and urgently requires more.
Brain and IQ One topic that is receiving considerable attention at present is the developing
brain and IQ. There are numerous animal studies documenting damage to the brain, especially during development. One important mechanism is interference with enzymes such as superoxide dismutase and catalase that protect metabolically active cells and tissues against oxida- tive damage22. Reductions in children’s IQ have come
to prominence as a result of more than 30 studies conducted in regions of China and elsewhere that have naturally high concen- trations of fluoride in the drinking water. A systematic review and meta-analysis from Harvard of 27 studies23 concluded that, although most had shortcomings and dealt with higher fluoride concentrations (most in the range 1-5ppm) than used for fluoridation (0.7-1.0ppm), there was almost universal agreement that higher fluoride led to lower IQ. The average reduction over the series
was seven IQ points. At best, this implies a margin of safety that is extremely low by normal toxicological standards. Proponents of fluoridation have been
quick to denigrate and downplay these studies, but despite some weaknesses in the individual studies – some inherent in the type of epidemiological design used – the consistency of the results demands attention. While they do not directly implicate artificially fluoridated water at 0.7-1.0 mg/l, the risk is clearly there and, as the review authors say, requires further research.
Is it ethical? Our right as individuals to refuse medica- tion is enshrined in law though whether that right is absolute or conditional – on, for example, an estimate of a public good such as the care of poor children (2, 15) – is disputed. Proponents argue that fluoride is not a medicine, but a natural mineral nutrient, like calcium, that is simply supple- mented to an ‘optimal’ concentration. The fact that it is ‘natural’ carries no
weight: arsenic is natural too. Nor is it in any way comparable to calcium, an essen-
Continued » Scottish Dental magazine 43
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