Health Risks of Ionizing Radiation: - Clark University

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INTRODUCTION
1.1 Goals
The health risks of exposure to low levels of
ionizing radiation are disputed within the scientific
community. Risks associated with exposure to high
levels of radiation are widely accepted and well
documented based primarily on the studies of the
atomic bomb survivors in Nagasaki and Hiroshima.
Some feel that the best way to estimate risk for lowlevel
exposures is to extrapolate from higher doses,
although there is some clear evidence of low-dose
risk. In this overview we have attempted to give an
unbiased summary of the available research with
an emphasis on the lower doses. The strengths and
weaknesses of the studies are explained in order
to help assess the variety of sometimes conflicting
evidence.
Not every epidemiological study that has ever
been done on the risks of radiation is included in
this overview. The body of research is simply too
great for us to have collected and read every study.
We attempted to collect studies generally considered
to be key for the various sources of exposure and
to exhaust our own capabilities to collect as many
studies as possible. Our search methodology
included the use of the PubMed search engine
and smaller follow-up searches through the end of
2003. Another source of epidemiologic data is the
DOE Office of Environment, Safety and Health’s
“Comprehensive Epidemiologic Data Resource” 1 ,
which provides data sets and studies relating to
worker health at DOE facilities, populations residing
near DOE sites, atomic bomb survivors, and radium
1 http://cedr.lbl.gov
2 www.lowdose.org
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dial painters. In light of the ongoing generation of
relevant information we have decided to consider
our overview a work in progress and plan to release
supplements of this initial review in the future.
Our intended audience is not necessarily one that
has been scientifically trained and so scientific terms
will be discussed and defined in a glossary found at
the end of the overview. The two following terms
from our title defined the scope of our overview:
Ionizing radiation refers to radiation that has
enough energy to remove an electron from a neutral
atom or molecule, creating a free radical. Ionizing
radiation is capable of creating DNA damage that
can lead to cancer. Radiations from sources such as
power lines, cell phones, and traffic radars are all
classified as non-ionizing radiation because they
are not capable of removing an electron. There is
ongoing research concerning health effects of nonionizing
radiation but it will not be covered in this
overview.
Low dose. Although we have collected studies
of a wide range of exposures we should define a low
dose as a reference point for the reader. Generally
speaking, a dose is low relative to doses where
the evidence of a health risk is more robust. The
Department of Energy’s (DOE) Low Dose Radiation
Research Program 2 has the fuzzy definition of any
dose not documented to show significant health risks;
they generally consider a low dose to be below 10
rem or 0.1 Sieverts (Sv). The Health Physics Society
recommends that exposures below 0.1 Sv only be
evaluated qualitatively as the risks are too small to
be observed. For the purposes of our overview we
have considered doses below 0.1 Sv to be low.