Misinterpretation of "All-Ireland Cancer Atlas, 1995-2007" with regard to water fluoridation and cancer.

Some maps contained in an All-Ireland Cancer Atlas published recently by the N. Ireland Cancer Registry and the National Cancer Registry have been used erroneously by anti-fluoridation groups to suggest a link between water fluoridation and cancer. The atlas in which these maps were published (and some previous reports) has analysed the differences in cancer risk between the two countries. [HC1] We do not consider that water fluoridation is a plausible explanation for the patterns shown. We have reached this conclusion for a number of reasons:

1. There is no good evidence to link fluoride levels in water, whether natural or added, to cancer risk. The International Agency for Research on Cancer has concluded The relationship between cancer mortality or incidence and both natural and artificial fluoride in drinking-water has been investigated in a large number of descriptive epidemiological studies of population aggregates, carried out in Australia, Canada, New Zealand, Norway, the United Kingdom and the United States. None of the studies provided any evidence that an increased level of fluoride in water was associated with an increase in cancer mortality.

2. The maps do not show a clear difference between Northern Ireland and the Republic of Ireland, but for a small number of cancers there is a smooth gradient in cancer risk from the north-east to the south-west of Ireland, increasing right across the island. There is no evidence of a change in this gradient at the border except for prostate cancer for which differences in PSA testing rates are the obvious and accepted explanation.

3. Although the bulk of the population in the Republic of Ireland lives in cities and large towns, where the water is fluoridated, most of the area shown on the map is sparsely populated and without fluoridated water supplies, so water fluoridation cannot be suggested as an explanation for the patterns seen.

There are many possible explanations for the variety of geographical cancer patterns which we have observed, and these are discussed in detail in the atlas, which is available on line at http://www.ncri.ie/atlas/atlas_contents.shtml and http://www.qub.ac.uk/research-centres/nicr/Publications/AllIrelandReports/#Anchor1

[HC1]In fact most of the map patterns cannot be explained by any of  these factors.

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