Health Risks of Ionizing Radiation: - Clark University

2 Introduction
1.2 A brief history of radiation
The history of the relationship between science,
radiation and health goes back to the late 19 th
century. X-rays were first discovered in late 1895
and dangers associated with exposure became
apparent very quickly. In 1896 the first injuries
due to x-ray exposure were recorded and in 1904
Thomas Edison’s assistant Clarence Dally was the
first person recorded to have died as a result of x-ray
exposure. Despite the risk, the use of x-rays for a
variety of applications rapidly caught on. During the
First World War portable x-ray machines were used
on both sides to locate shrapnel and to set broken
bones.
Radium was discovered in 1898 and its use in
medicine also spread very quickly. In the 1920s,
sickness and death in watch dial painters, who
ingested small amounts of radium in their work,
taught scientists and doctors that internal exposure
to radium could be harmful. It was also during the
1920s that the cancer risks of radiology became
apparent. Some awareness was beginning to spread
that radiation exposure from the new technologies
could be harmful and in 1928 the first internationally
recognized radiation safety guidelines were
published.
There was still a popular enthusiasm about
radiation during this time. Between 1920 and 1950
patents were registered for radium toothpaste, radium
hearing aids and radium tonic water. As World War
II emerged in the 1930s plans for building a nuclear
bomb were made. Plutonium was discovered in
1940 and the Manhattan Project, with its goal to
“make the bomb”, was initiated in 1942. On July 16,
1945 the first nuclear weapon was detonated in New
Mexico. At the time of the test the type of fallout that
would result was something of a mystery. In August
of 1945 two nuclear bombs were dropped on Japan
in Nagasaki and Hiroshima. In the weeks after the
bombs, radiation exposure was not discussed in the
US press.
In the 1950s the US government began a
campaign for a more friendly attitude toward
nuclear science and promoted civil nuclear power.
There were hundreds of uranium mines across the
country serving both the nuclear power industry
and the nuclear weapons industry. In 1951 the US
established the Nevada Test Site in order to have a
domestic testing location that could ease logistical
and security concerns. Prior to this tests had been
conducted in the South Pacific. The fallout from
the test sites and the occupational hazards of the
workers in the mines and in the weapons factories
were adding to the range of radiation exposures that
we experience.
1.3 Exposure
People are exposed to ionizing radiation from many
different sources. The exact amount depends on where
they live, what their jobs are, what their lifestyles are
like and so on. Over 80% of total average exposure
comes from natural sources. Manmade sources such
as consumer products that emit radiation, fallout
from the US and global nuclear tests, diagnostic and
therapeutic medicine, radiation from nuclear plants
and occupational exposures make up the rest. The
following pie chart gives the estimated worldwide
average exposure spectrum.
It should be noted that illustrations such as the
pie chart (Figure 1-1) presented here can be used
to minimize the importance of manmade sources of
radiation. For example, one may argue that fallout
from test sites contributes a mere fraction, less than
1%, of the total exposure to ionizing radiation. On
the other hand this is an involuntary exposure that
Figure 1-1. Average worldwide exposure to radiation
sources; total exposure averages 2.8 mSv per year
(UNSCEAR 2000).