December 15, 2002, Sunday
Sunday Times (London)
EXPOSURE to radon, the naturally occurring radioactive gas, may be a factor in developing multiple sclerosis (MS), a study in Sligo has found.
Areas around Ireland which have high levels of radon emissions coincide with higher prevalence of the illness, according to the research.
"The north-west of Ireland appears to have one of the highest prevalence rates of MS in Ireland though there is as yet no reliable national database," said the report. "The area is one of the highest radon-emitting areas in Ireland, with Donegal, in particular, containing some of the most highly uranium-enriched granites in the country." Multiple sclerosis is a chronic neurological condition which has no cure. Its cause is unknown although it is likely to be genetic, as well as triggered by environmental factors.
Exposure to some environmental agent during childhood, before the age of 15, by those susceptible to the disease appears to be a factor in its subsequent development.
Margaret Gilmore and Eamonn Grennan, two lecturers at Sligo Institute of Technology, believe radon may be a trigger for the disease.
Gilmore, a medical doctor who lectures in social studies, and Grennan, an environmental scientist, examined the membership of the MS Society in Ireland to see where the disease occurs most.
Then they looked at data from the Radiological Protection Institute of Ireland on radon levels around the country. They discovered that regions with higher levels of MS were broadly those which had greater radon emissions.
Sligo, which had one of the highest prevalence rates of MS, also had the highest levels of radon, according to data from the institute, with 20% of homes over the danger limit.
Previous research has shown that the disease is more common in Europe, North America and Australia. Gilmore and Grennan point out that while they have wide differences in natural and built environments "these areas are underlain by rocks of the same age and similar in mineral composition", uranium-rich granites which release radon.
The study also points out that there is a low incidence of MS among Eskimos, American Indians and other nomads who live mainly outdoors and over areas of much older rocks. Radon is not dangerous in the open air where it dissipates; but when trapped in buildings it quickly decays to produce radioactive particles.
"Our theory is fairly innovative," said Gilmore "in that it would also explain why (MS) is common in Australia, North America and Europe and not common in central Africa. It would seem to be an added link - we're not trying to say it is the whole story, but it would be another piece of the jigsaw."
Once they had established a trend between MS and radon, Gilmore and Grennan surveyed patients at the Northwest MS Therapy Centre in Sligo town.
They asked about patients'childhood homes and found that they were likely to have lived in older one-storey houses with a private water supply and open fires, all of which could increase exposure to radon.
Although they found some evidence to support their theory, the researchers were stymied by a lack of information on the levels of MS in Ireland, where there are more than 6,000 sufferers, according to the MS Society of Ireland.
"There isn't a proper census of people with MS in Ireland as yet," said Gilmore. "That's one of the things we would hope to do in a further study."
Radon, already linked to lung cancer, is a colourless, odourless, naturally occurring radioactive gas which is formed in the ground by the radioactive decay of uranium present in small quantities in rocks and soils. It moves through soil and seeps through cracks in floors and walls. As the gas is nine times heavier than air it is more concentrated at ground level.
Gilmore said if the hypothesis was proven it would be imperative to prevent further cases by equipping homes and other buildings to combat radon. "The financial and human cost savings would be immeasurable," concluded the report.
Remedying the problem usually costs a few hundred euros and involves extracting air from below the floor and ventilating it outside.
MS is caused by scarring of the nerves in the brain and spinal cord. Many symptoms can be treated or managed. It is the most common neurological condition affecting young adults in Ireland today.
"In Europe the prevalence rate is 1 in 800 but in some parts of Ireland
it is as high as 1 in 400," said Maura McKeon of the MS Society of Ireland.
"The north west of Ireland seems to have one of the highest rates in the
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