[Peace-discuss] Off subject--radiation

[Morton K. Brussel]

Some ought to be interested:

Op-ed from the New Scientist

Who's afraid of radiation?
03 August 2010
by Wade Allison

Our attitude to ionizing radiation is irrational,
and easing safety limits would do far more good
than harm, says Wade Allison

THE word "radiation" frightens people, and little
wonder. Ever since the cold war, the prevailing
view has been that ionizing radiation can do real
harm to us without being seen or felt - and should
be avoided at all costs. In fact radiation is much
less harmful than we feared. Given the
availability of carbon-free nuclear power, this
makes a sea change in our view of radiation rather
urgent.

    Fear of radiation grew alongside descriptions
of what might happen in the event of a nuclear
war. In earlier decades there was genuine
scientific uncertainty about radiation's long-term
health effects, and scientists were unable to be
reassuring. So, driven by universal popular
concern, tight regulation was imposed to minimize
public exposure.

    Since 1950, public dose limits have been
tightened by a factor of 150. Currently, the
internationally recommended limit is 1
millisievert per year above the natural background
level of about 2.5 millisieverts per year. For
comparison, a typical CT scan might give you a
dose of 5 millisieverts and a simple dental or
limb-fracture X-ray 1/100th of that.

    Much has been learned over the past half
century from clinical medicine, radiobiology and
accidents like Chernobyl. There is no doubt that a
very high single dose is fatal, as the fate of the
initial 237 firefighters at Chernobyl illustrates.
Within a few weeks, 28 died, and 27 of those had
received doses in excess of 4 sieverts.

    However, many people receive much higher
doses than this, albeit under very different
circumstances. When a cancer patient is treated
with radiation in a radiotherapy clinic, the
tumour dies after absorbing a dose of more than 40
sieverts. During the treatment, healthy tissue and
organs near the tumour get an incidental dose of
some 20 sieverts, which is 20,000 times the
recommended annual limit and at least five times
the dose that proved fatal at Chernobyl.

    How can tissue survive this friendly fire? A
radiation dose is the same in principle, whether
received in a hospital or elsewhere. But the
critical point is that the therapeutic dose is
spread over four to six weeks, giving cells time
to repair the damage. Each day the healthy cells
receive about 1 sievert, and just manage to repair
themselves. The tumour cells receive a higher
dose, and just fail to do so.

    So much for acute effects, but what about
longer-term ones? Very rarely, the damage is
misrepaired, and the resulting error may
eventually lead to cancer. To find out how often
this happens, we need to compare the lifelong
health data of a large number of people, some of
whom have received a significant radiation dose
and some who have not.

    The nuclear bombs dropped on the Japanese
cities of Hiroshima and Nagasaki in August 1945
provide us with the data we need. About 66 per
cent of the original inhabitants of the two cities
survived to 1950, since when their individual
health records have been extensively studied.

    By 2000, 7.9 per cent of them had died of
cancer, compared with 7.5 per cent expected from
rates found in similar Japanese cities over the
same period (Radiation Research, vol 162, p 377).
This shows that the extra risk caused by radiation
is very small compared with the background cancer
risk, and less than the 0.6 per cent chance of an
American citizen dying in a road traffic accident
in 50 years.

    Not surprisingly, those who received higher
doses developed more cancers. But those subjected
to doses less than 0.1 sievert showed no
significant increase in solid cancers or
leukaemias. Nor did they suffer an increase in the
incidence of deformities, heart disease or
pregnancy abnormalities. So there is a practical
threshold of 0.1 sievert for any measurable effect
due to a single acute dose.

    Given what we now know, from radiotherapy to
the legacy of the attacks on Hiroshima and
Nagasaki, it is clear that radiation safety limits
are far too conservative. Evidently, our bodies
have learned through evolution to repair or
eliminate damaged cells, with a low failure rate.
I suggest the upper limit might be reset at a
lifetime total of 5 sieverts, at no more than 0.1
sievert per month. That would be a fraction of a
radiotherapy dose, spread over a lifetime.

    Such a revision would relax current
regulations by a factor of 1000. This may seem
excessively radical to some, especially those in
the safety industry who have spent 60 years trying
to reassure the public by regulating against all
avoidable sources of radiation - which, after all,
is what society asked them to do.

    But common sense says that extra precautions
are most needed when we know least, and in a
reasoned approach to any new technology we should
start with a cautious limit which may be relaxed
later, as instrumentation improves and our
appreciation of it grows. The regulation of
ionising radiation has resolutely gone in the
opposite direction, driven by fear.

    Changing the limits would bring practical
benefits. Radiation safety is a major contributor
to the cost of nuclear power, so any relaxation
should lead to big cost reductions. Given that we
urgently need to develop carbon-free energy
sources, that is hugely beneficial.

    It should also lead to a more sensible
attitude to nuclear waste. If treated properly,
the quantities are small, it become harmless after
a few centuries, and it may be buried at moderate
cost. In any event, the effect of radioactive
waste is a small matter compared with the global
influence of carbon dioxide and leaked
hydrocarbons. We should re-examine the
environmental risks of radiation with the same
radical attitude that is required for our own
health.

    Wade Allison is a nuclear and medical
physicist at the University of Oxford and the
author of Radiation and Reason (YPD Books).
He has no ties to the nuclear industry

<http://www.newscientist.com/article/mg20727715.800-whos-afraid-of-radiation.html?full=true>

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