"Radiation is a very weak carcinogen. The worst case of
radiation exposure in history the bomb victims at Hiroshima and Nagasaki
gives unfortunate but instructive evidence to the case: For 65 years,
researchers have followed nearly 90,000 hibakusha, the name in Japan for atomic
bomb survivors who were within three kilometers of the Hiroshima and Nagasaki
explosions in 1945. Scientists compared them to a non-exposed Japanese
population in order to calculate the effects of the radiation to which they had
been exposed.
The current estimate is that 572 hibakusha — a little more
than 0.5 percent — have died, or will die, from various forms of
radiation-induced cancer. By comparison, the cancer rate for people who smoke
cigarettes is about 20 percent." [18,000] - - Harvard instructor David Ropeik,
author of a book on risk evaluation.
How Does Low Level Radiation Provide Beneficial
Effects?
Written on
May 3, 2011 by
Rod Adams -
http://atomicinsights.com/2011/05/how-does-low-level-radiation-provide-beneficial-effects.html
In a recent
ANS Nuclear Cafe post, I mentioned the radiation hormeis theory proposed
more than three decades ago by Dr. Don Luckey, a biochemist and nutritionist who
wrote a book in 1980 titled Hormesis With Ionizing
Radiation. According to Dr. Luckey and a number of other researchers
in the field, a small dose of radiation can provide beneficial effects.
As a former nuclear power plant operator, it was once a little
difficult for me to accept that notion. After all, I had been taught –
repeatedly – to keep radiation doses As Low As Reasonably Achievable. Early in
my nuclear career, I was involved in planning work that resulted in a great deal
of additional expenditures and manpower in order to reduce doses by a fraction
of the amount that Dr. Luckey has said will not cause harm and may actually do
some good.
About 15 years ago, I had the
pleasure of meeting people like Jim Muckerheide, Jerry Cuttler and Ted Rockwell
who introduced me to the study of the health effects of low level radiation and
opened my eyes to the massive amount of peer reviewed and published information
that is not widely shared or promoted. They have also helped me to find many
unpublished studies – like the famous nuclear shipyard workers study that was
completed but never released by the Department of Energy.
A few days ago, I asked Dr. Cuttler to help me explain just
how the beneficial effects of radiation work. Here is his boiled down
explanation – which I will follow with some links to far more detailed studies.
As Myron Pollycove and Ludwig Feinendegen have been explaining
in their papers over the past ten years (also in my article Nuclear Energy and
Health), there is a tremendous rate of endogenous DNA damage occurring in all
organisms due to normal energy production, i.e., oxydation of glucose. Reactive
oxygen species (ROS) attack the DNA continuously as we breathe, but each
organism has powerful defences that prevent (via antioxidant production), repair
and remove DNA damage. The net result is an average of one permanent mutation
per cell per day.
The contribution of normal background ionizing radiation to
this DNA damage rate is about ten million times less than the endogenous DNA
damage rate. The effect of a small increase in the background radiation level is
to produce a small increase in the DNA damage rate. This produces a low level of
stress on the activity of the defences (damage-control biosystem), which
stimulates this system to work harder, i.e., perform much better (producing a
reduction in the DNA mutation rate). A large increase in radiation level
inhibits this system (resulting in an increase in the DNA mutation rate).
Harmful effects begin to surpass beneficial effects for an acute dose above 50
rad (0.5 Gy).
To summarize, the major effect of radiation on organisms
(i.e., humans) is its effect on the damage-control biosystem, not its direct
damage to the DNA molecules. This increase in the amount of DNA damage is
relatively trivial—orders of magnitude less than the decrease in the amount of
DNA damage due to the stimulation of defences (radiation hormesis).
Based upon human data, a single whole-body dose of 150 mSv (15
rem) is safe. The high natural radiation level of 700 mSv per year (70
rem/year), corresponding to a 70-year lifetime dose of 49 Sv in Ramsar, Iran, is
also safe. Both these single and continuous doses are also beneficial (Cuttler
and Pollycove 2009). This conclusion is applicable to humans of all ages and to
sensitive, cancer-prone individuals.
Additional Reading
Observations on the Chernobyl Disaster and LNT,
Zbigniew Jaworowski, Dose-Response. 2010
NCRP Report No. 136 – How to ignore data that contradict the
LNT hypothesis, Dr. John Cameron, Radiation
Science and Health, June 14, 2006
Setting Radiation Requirements on the Basis of Sound Science:
The Role of Epidemiology, CNSC March 2011