NUALA AHERN, MEP,
Sir, - Professors Walton, Mitchell and McAulay (May 31st) address some of the issues raised in my article on radiation and Chernobyl in your edition of April 18th.
What a pity they did not address the central issue. This is not an academic dispute for the victims of Chernobyl. Every year on the anniversary we hear the same mantra: illness after Chernobyl is due to imagined effects. I believe this adds insult to injury, but more seriously such views have led to people being denied access to medication.
Scandalously, the Chernobyl children who suffered from thyroid cancers were not classified as victims of the accident until much later than they should have been, because data that was coming out was argued against until it became incontrovertible. It is a pity to see the same approach being taken by your correspondents, and by Sowerby and Turvey.
What they ignore is that dose may not be an important consideration for risk because delayed effects such as bystander effects and genomic instability are not related to dose . The lowest dose we can test (one alpha particle traversal of a cell population or 2.5 mGynSv gamma radiation) can induce full expression of a radiation response. This response is capable of inducing death, mutation and transformation in vitro (in cultures) and is also known to be induced in humans and mice after total body irradiation to very low doses.
I did state that the microsievert does not allow direct comparison between different types of radiation. The microsievert is a physical fudge factor designed to allow comparisons between agents which are as different as apples and bananas. The argument for the microsievert is essentially that if you are hit on the head by a kilo of bananas or a kilo of cocaine it will have the same effect. The argument against using the microsievert is that if you ingest the kilo of bananas or the kilo of cocaine the effect will be distinctly different. Using a weighting factor to try to make the effects the same is not very credible!
The effects of long-term exposure are better known than the effects of acute exposure, and most of us, with the exception, perhaps, of the physicists, evolved in high background radiation. Acute exposure is unnatural, not chronic exposure. Acute exposure is what we humans have not evolved to cope with. - Yours, etc.,
NUALA AHERN, MEP, Oaklands, Greystones, Co Wicklow.