Misinterpretation of “All-Ireland Cancer Atlas, 1995-2007”
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 by anti-fluoridation groups erroneously, and without discussion with the atlas authors, 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. 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:
- 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”
- The maps do not show a clear difference in cancer risk 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.
- 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.
- Fluoride added to drinking water is only one of many sources of dietary fluoride. A paper published jointly by the two registries in 2011 (1) has described the difficulties of comparing fluoride ingestion by populations on either side of the border. This paper has shown that there was no difference across the border in the risk of osteosarcoma in children, the only cancer for which there is any suggestion of a link with fluoridated water
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 in our All Ireland Report Section, please click link and also in our Peer Reviewed Publications Section for 2011, please click link