Research published today shows that a cluster of Down's syndrome births in the Dundalk area was not related to radioactive contamination from the Windscale plant in Cumbria.
Dr Geoffrey Deane, former director of the Medical Social Research Board, and international colleagues performed a follow-up study to one published in 1983, which linked the Down's syndrome cases to radioactivity from a fire at the Windscale Number 1 reactor in Sellafield in October 1957. It was also postulated that the unusual cluster of births to mothers who attended a school in Dundalk during 1956/1957 could have been linked to an outbreak of influenza which occurred in the school at that time.
The latest research, published in the Journal of Occupational and Environmental Medicine, a British specialist journal, rejects these explanations and concludes there is no common cause for the Down's syndrome incidences.
Dr Deane broadened his study to include an analysis of all live births in Co Louth. He also compared the incidence of Down's syndrome in the county with that of the neighbouring Newry and Down District in the North.
The results show that, for the period 1961 to 1980, the prevalence of Down's syndrome in Co Louth was at expected levels. The occurrence of Down's syndrome in the Newry and Mourne District during this period was also similar to that in other areas of the island.
A more detailed analysis of the eight cases of the syndrome linked to St Louis School in Dundalk found that one child did not, in fact, have Down's syndrome. In addition, Dr Deane has established that one of the mothers did not attend St Louis School. However, five of the six confirmed births were to mothers under the age of 30, which is a striking cluster of cases.
The latest research has shown that not all of the mothers of the children were at St Louis School at the same time. Two of the six mothers left the school in June 1957, four months before the outbreak of influenza and the fire in Windscale, both of which occurred in October 1957.
The new study also specifically investigated two other Dundalk schools and found no raised risk of Down's syndrome among births to mothers who were pupils at these two schools in 19561957.
Dr Deane told The Irish Times his research has shown the incidence of Down's syndrome was less than originally reported. In addition "only three out of the six mothers were at St Louis school at the time of both the Windscale fire and the influenza outbreak", he said.
He concludes his paper by saying: "We have been unable to find a plausible common cause for the cases constituting this cluster, and details of the individual cases suggest that there may not be one."
The latest research rules out any scientific link with the Windscale fire in 1957 and suggests that the health scare generated by the original report was, in fact, unfounded.
Down's syndrome is a genetic abnormality which occurs when there is an extra chromosome number 21 present. It is relatively rare in the offspring of women under 30, although the natural incidence of the condition rises sharply in children of mothers over the age of 40. The typical features include mild to moderate mental handicap, some characteristic facial features and congenital heart disease.