An important study was reported in the July 2, 2015 issue of
Nature, a publication read by
scientists. It was written by Alison
Abbott. She discussed a report carried
out in the US, France, and the UK involving 300,000 nuclear industry employees
over a 60 year period whose radiometer badges were used to study the radiation
received and this was then matched against their health records. It showed that as claimed by H. J. Muller for
low doses of ionizing radiation (mostly x-rays) to produce mutations and by Ed
Lewis for Hiroshima and Nagasaki survivors of atomic bombs, the linearity of
dose to mutation or dose to incidence of leukemia is maintained with no threshold
at lower doses. Those in the nuclear
industry, governments engaged in making nuclear weapons, and some health
professionals using radiation for diagnosis and treatment of a variety of diseases
have sometimes claimed that below a certain low dose there are no mutations
induced or no cancers induced by exposure to low doses regardless of many times
a person is exposed. For most of the nuclear
industry workers they have an annual exposure of about 1.1 mSV (or in the older
terminology O.11 roentgen) above the natural background rate asll humans experience
which is 2 to 3 mSv (or 0.2 to 0.3 roentgens).
In this study, the total accumulated dose of each worker was calculated
and the medical history for cancers was studied. The report also supports what Muller and his colleagues
found in the 1930s and 1940s – that whether the total dose was received acutely
or spread out daily or interrupted by intervals of working with radiation and
years of not being exposed, it was the total dose that counted. The risks, of course are low, compared to
high dose exposures of 1000 mSv (100 roentgens) that accidents and nuclear
bombs inflicted on relatively few humans over the past 75 years.
The study
appeared in Lancet Haematology http://doi.org/5s4;2015 The
lead author is K. Leuraud. I have never appreciated
the logic of deniers of low dose effects of radiation. The linearity holds for experiments
with fruit flies (and many other organisms from bacteria to mice) from doses of
50 to 12,000 roentgens (500 mSv to 120 Sv).
Deniers may fear a public rejection of using radiation for diagnosis and
cancer treatment. During the Cold War,
it was the military that tried to convince the public that small doses of
radiation (such as worldwide fall out) were harmless or that contaminated soils
from nuclear testing grounds were safe to live in if the doses were low. Physicians quickly recognized the need for
safety of both patients and practitioners and they found more effective ways to
take x-ray pictures at even lower doses than in the 20th century. I
have welcomed x-rays at such low doses for my own family and myself. It is a question of weighing risks. I’d rather have x-rays to rule out an ulcer
or cancer in my intestinal tract than keep my fingers crossed that maybe I’ll
be lucky and there is no serious problem that gives me symptoms. At the same time, I celebrate those in the
health professions who seek to use the least amount of radiation needed for
diagnosis. When tens of millions of people are exposed at low dose there will
be a few losers with induced mutations or leukemias. But if no one had diagnostic x-rays there
would be hundreds of thousands of people who would die prematurely because their
diseases would not be diagnosed until they are terminally ill.
No comments:
Post a Comment