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, youll be OK; if one hits you, youll be injured and
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 ICRPs 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
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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