PHILIP W. WALTON,
Sir, - Thanks to David Sowby and Frank Turvey (The Irish Times, April 11th) for laying out the facts about the real effects of radiation which we hope will allay some of the phobia present in this country. On the other hand Nuala Aherne, in her response of April 18th, in our opinion attempts to hype things up again and in the process makes several errors which we would like to address.
Ms Aherne states that the unit of dose, the microsievert, "does not differentiate between the different types (or quality) of radiation". It is precisely to account for different types of radiation that the microsievert unit was devised so that the unit would allow radiation effects of different types to be directly comparable.
She also implies that the effects of acute exposure, such as happened at Chernobyl, are less well understood than the effects of chronic exposures. This is not so. Much of the evidence of ill-effects has been obtained from studies of the survivors of the atomic bombs in Japan and these studies are continuing. The effects of long-term, low-dose chronic exposure are more problematic to predict. This is because we are subjected to this exposure continually, thus making experimentation very difficult; we have instead to extrapolate from known high-dose effects. Incidentally, no major hereditary effects have been found in the Japanese population.
To once again put the radiation from Sellafield into perspective, may we quote data from our own Radiological Protection Institute (RPII)? The current dose being received by the Irish public, which is largely obtained from eating fish, is 0.3 microsieverts a year, whereas the dose from naturally occurring polonium-210 in the same fish is about 100 times greater. This 0.3 miocrosieverts should also be compared with the 2,500 microsieverts per year we all get from natural sources.
It is said that Ireland gets no benefit from Sellafield and so should tolerate no radiation from it. We do, however, get some benefit in a number of ways. Our hospitals, researchers and industry use radioisotopes, some of which are produced by the British nuclear industry. Also, some of our radioactive waste (we have no nuclear repository) finds its way to Sellafield. Sellafield also services some of the world's 438 nuclear power reactors. These reactors generate close to 20 per cent of the world's electricity, thus saving enormously on oil and gas reserves and also, in the process, producing virtually no greenhouse gases - a benefit to all of us.
What is going to happen when the oil and gas runs out? Northern Ireland is completing an electrical interconnector to Scotland and we have an interconnector to the North so, who knows, we might even find ourselves using British nuclear electricity. - Yours, etc.,
PHILIP W. WALTON, Professor of Applied Physics, NUI, Galway;
PETER I. MITCHELL, Associate Professor of Radiation Physics, UCD;
IAN R. McAULAY, Associate Professor of Physics, TCD.