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There is No Safe Dose of Radiation: CADU and Collective Dose

Official radiation protection systems have long recognised that the smallest amount of ionising radiation can cause genetic damage, possibly leading to a fatal outcome. This is because ionising radiation exists in the form of highly energetic particles travelling through space or through our body tissues. Any cell in the path of the particle may be mutated. The image of a gunman firing randomly in a football stadium provides a useful analogy: if his bullets miss you, you’ll be OK; if one hits you, you’ll be injured and may die.
This is why it is conventionally said that “there is no threshold”, or “no safe dose of radiation”; the smallest amount has some chance of causing a lethal outcome, in the same way that a single lottery ticket confers some chance of winning a million pounds. And for many years the radiation risk agencies, like the International Commission on Radiological Protection (ICRP), have used the concept of “Collective Dose” to quantify that chance.

What is Collective Dose?
Collective Dose is a way of calculating the number of potential cancers that will happen in a population exposed to a known dose of radioactivity. Thus ICRP’s risk model predicts 2,350,000 extra cancer cases worldwide from testing atomic weapons in the atmosphere in the 1950s and ’60s. The effects of any kind of fallout or emissions can be calculated in the same way. The sums can be extended to the far distant (even infinite) future, but are usually cut off at 500 years. Either way (and even if for the time being we ignore the many scientists who criticise ICRP for underestimating the effects), the number of potentially dead people can be impressively large, which embarrasses apologists of nuclear power and nuclear weapons. They tend to argue that there is no certainty that any such effects will occur - in other words, the cancers are only theoretically possible - and that the epidemiological basis of such predictions is weak.

Should we abandon Collective Dose?
Professor Roger Clarke, Chairman of the ICRP and Director of the UK National Radiological Protection Board, would like to see Collective Dose abandoned in favour of a concept he calls “Controllable Dose”. According to Clarke, so long as the person most exposed to some radiation source runs a risk which can be considered “acceptable”, then all the people exposed to that source are adequately protected.
His critics point out that his logic is the same as letting a mad gunman into every football game on the grounds that no single person in the crowd has worse than a 1 in 25,000 chance of getting shot.
For those of us campaigning against the use of radioactive waste (DU) in munitions, planes and ships it is important to keep on top of how harm from radiation is measured. We campaign against the use of DU because we believe it to be harmful.
Any change in the way radiation effects are studied is of concern.”

ACTION: Write to your MP to ask what is their policy on collective dose Please forward to CADU a copy of your letter and any reply.

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From CADU News 9: Winter 2001/2002

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Page last updated: January 28, 2003