Some maps contained in an all-Ireland cancer atlas published recently by the National Cancer Registry of Ireland (NCRI) and the Northern Ireland Cancer Registry (NICR) have been used erroneously by anti-fluoridation groups to suggest a link between water fluoridation and cancer, according to the two registries.
The All-Ireland Cancer Atlas 1995-2007, in which these maps were published (and some previous reports), has analysed the differences in cancer risk between the two countries. “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,” the cancer registries stated.
Firstly, the NCRI and the NICR said, there is no “good” evidence to link fluoride levels in water, whether natural or added, to cancer risk, citing the International Agency for Research on Cancer (IARC).
The Agency 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.”
Both registries said the maps did not show a clear difference between Northern Ireland and Ireland, but for a small number of cancers there was a smooth gradient in cancer risk from the North-East to the South-West of Ireland, increasing right across the island. There was no evidence of a change in this gradient at the border except for prostate cancer, for which differences in PSA testing rates were the obvious and accepted explanation, both registries said.
Although the bulk of the population in the Republic 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 it cannot be suggested as an explanation for the patterns seen, they submitted.
“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 online at www.ncri.ie/atlas/atlas_contents.shtml and www.qub.ac.uk/research-centres/nicr/Publications/AllIrelandReports/#Anchor1.
“In fact, most of the map patterns cannot be explained by any of these factors,” they said.
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