-Caveat Lector-
>From the New Australian
http://www.newaus.com.au/news136aaron2.html
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Exploding Nuclear Myths Part 1 — "No safe level of radiation"
By *Dr Aaron Oakley
No. 136, 4 -10 October 1999
Dr Aaron Oakley
An important characteristic of activists is that they are prepared to use any
argument — true, half-true or false — to support their ideological agenda.
Hence truth plays second fiddle to expediency. This article examines a canard
popular with anti-nuclear activists — that there is no level of radiation which
is safe. This myth will be exposed along with certain activists who have
repeated it. since 1959, the International Commission on Radiological
Protection (ICRP) has dictated that regulations be based on the assumption that
the effects of low doses of radiation may be derived by linear extrapolation
from the effects of high doses (this is called the linear hypothesis). For
example, 10,000 mSv of radiation (a very high dose!) would be expected to kill
those exposed within hours, and by assuming a linear relationship, we would
expect that a dose of 1 mSv would kill 1 in 10,000 people. The fact that we are
not dropping like flies (background radiation averages about 2.4 mSv/year
globally) immediately brings the hypothesis into question.
Since high doses of radiation have a deleterious effect on health, authorities
have assumed that there is no safe dose, and regulations required the
minimisation of all radiation exposure. This policy position does not reflect
the scientific knowledge of the biological effects of low-dose radiation. As
radiation science has advanced, it became apparent that the situation of health
and radiation was not so clear-cut. Furthermore, the evidence that low dose
radiation may be beneficial for health has been accumulating for over half a
century. This effect is called hormesis. Even in the early days of the
Manhattan project, there was evidence to suggest that certain doses of
radiation could be beneficial to health: Experiments conducted in 1943 involved
the exposure by inhalation of animals to uranium dust in the expectation that
it would be deadly. Surprisingly, the exposed animals appeared healthier, lived
longer, and produced more offspring than their non-exposed counterparts. These
results were confirmed by subsequent research.
The graph on the right {{@ site}} shows the effects expected from the two main
models of the effect of radiation exposure. The linear hypothesis predicts
negative effects of radiation at high and low doses, with toxic effects
increasing with increased dose. With hormesis, beneficial effects are expected
at low dose, but with toxic effects at higher dose. Since the Manhattan
project, numerous research papers have produced convincing evidence for
radiation hormesis. In 1994 the United Nations Scientific Committee on the
Effects of Atomic Radiation (UNSCEAR) published a report on the stimulating and
adaptive effects of low-dose radiation. It reported that in mammals, radiation
hormesis manifests itself as enhanced defence reactions against infectious
disease, increased longevity and improved fertility. Yet despite the growing
evidence for hormesis, the ICRP continued to lower the limits for acceptable
radiation exposure.
We should also consider the effects of living with radiation: Different regions
of the world have different levels of background radiation. The global average
background radiation level is 2.4 mSv/year, but can be as high as 240 mSv/year.
Epidemiological studies involving large cohorts show that higher levels of
background radiation provide further evidence for radiation hormesis. The graph
shows the effects expected from the two main models of the effect of radiation
exposure. The linear hypothesis predicts negative effects of radiation at high
and low doses, with toxic effects increasing with increased dose. With
hormesis, beneficial effects are expected at low dose, but with toxic effects
at higher dose.
Between 1970 and 1986, people living in Yangjiang county in china (background
radiation 5.5 mSv/year) were compared with people living in two adjacent low-
background counties, Enping and Taishan (background radiation 2.1 mSv/year).
(The cohorts were large: 74,000 people from Yangjiang and 77,000 from Enping
and Taishan.) The data show that in an age group of 10 to 79 years, the general
cancer mortality was 14.6 per cent less in Yangjiang compared with Enping and
Taishan. Furthermore, the leukemia mortality was 16 per cent lower in men and
60 per cent lower in women from Yangjiang.
Results similar to the Yangjiang study have been obtained in France, Japan and
elsewhere. Yet radiation regulatory authorities continue to assume that no
level of radiation is safe...as have anti-nuclear activists. As we have seen,
there is much evidence to show that low-does radiation is not only not harmful
but may be beneficial. But still the myth that there is no safe dose of
radiation is trotted out mindlessly. The myth has been repeated by the
Australian Konservation Foundation, as previously documented. This non-fact has
also been repeated by green politicians such as Western Australian MP Giz
Watson. A further example is Gavin Mudd, who in the September issue of
Australasian Science claimed that "New scientific evidence suggests that
exposure to low levels of ionising nuclear radiation increases cancer risk". It
is a pity that no reference was given to support that claim, given the large
body of contradictory evidence. Mudd also claimed that increases in background
radiation have been linked to increases in cancer rates in areas such as
Chernobyl in the Ukraine, Sellafield in the UK and Three Mile Island in the
USA. Let us examine the facts.
In the case of Chernobyl, 31 people were killed in the immediate aftermath (29
were fire-fighters). Most of the deaths were due to burns, but a few were (not
surprisingly) due to extreme radiation doses. Workers and others exposed to
high radiation doses of radiation have also died since. A conference of experts
sponsored by the World Health Organisation after the accident speculated that
some 1,600 additional deaths by cancer induced by increases in background
radiation might occur in Europe over the three decades following the accident
(higher figures have also been bandied about). However, in making these
estimates, the conference used the already suspect linear hypothesis. Even if
we consider this estimate to be accurate, it is important to put it in
perspective by noting that the expected cancer deaths (from other causes) in
the population now alive in Europe is 120 million over that time-frame.
In what is probably the largest and most systematic study of the health effects
of Chernobyl accident, the International Atomic Energy Agency, studying people
living beyond the 18 mile "prohibition zone" around the accident site found "no
health disorders that could be attributed directly to radiation exposure".
Earlier speculations of increased numbers of leukaemia and other cancers did
not eventuate. They further concluded that "any increases over the natural rate
incidence of cancer or hereditary effects would be difficult to discern, even
with larger and well designed long-term epidemiological studies". The agency
did acknowledge the possibility of a statistically detectable increase in the
number of thyroid cancers. (This is because the thyroid gland concentrates a
radioisotope of iodine released in the accident). There have been about 800
cases of thyroid cancer in children, most of which were curable, though about
ten have been fatal. It is note worth that the risk of thyroid cancer could
have been avoided if simple prophylactic measures such as the distribution of
potassium iodide tablets had been taken.
In the case of the British Nuclear Fuels plant in Sellafield UK, it is indeed
mischievous to claim that increases in background radiation have lead to an
increase in cancer rates. Studies of all 14,282 workers in the plant revealed
that cancer rates were 4 per cent less than that of England and Wales, and was
the same as that of the district of Cumbria where the plant is located. Many
scare stories about Sellafield derive from epidemiological data suggesting that
there was an increased risk of childhood leukaemia in the children of the
Sellafield workforce. However, follow-up investigation revealed that this risk
is inconsistent with other epidemiological data and experimental data. Thus, it
is unlikely that the association observed in the children of the Sellafield
workforce represents a causal relationship and that other factors may be to
blame.
With regard to the Three Mile Island (TMI) accident, the death-toll currently
stands at zero and is not expected to rise dramatically any time soon. There is
no evidence of an increase in cancer rates in areas affected by the accident.
To put things in perspective, health physicists have calculated that the number
of premature deaths due to cancer within a 50-mile radius of the TMI plant to
be about one. And this estimate is based on the questionable linear hypothesis!
This is in comparison to the approximately 30,000 premature deaths to be
expected in the same area over the same time-frame due to non-radiation induced
cancer. Indeed, many of the journalists who flew to TMI after the accident
would have received a higher dose of radiation — due to their flight — than the
TMI residents received from the accident!
When we look at the facts about radiation, Chernobyl, Sellafield, and Three
Mile Island it allows us to put the scaremongering of anti-nuclear
propagandists in perspective. It is a great pity that journalists and those in
the nuclear industry never bother to do this. Truth is usually the first
casualty in an ideological war.
If any readers have observed other activists repeating the "no safe radiation"
shibboleth, let me know and I will update this article to include them.
(c)1999 By Oakley Environmental Research. The right to reproduce this page is
granted providing that attribution to the author is given and that this notice
is reproduced.
Feel free to email Dr Oakley mailto:[EMAIL PROTECTED]
Return to The New Australian
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