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that all airline crews be informed of risks that they
may make optimal choices concerning their health. Currently,
the most important issue for radiation exposure is
for the pregnant crew member and the theoretical effect on
the unborn child. It is recommended that these crew members
consult with their physicians and company medical
department.
The Terms
Low dose radiation can be a highly technical topic; this
article tries to keep it simple. Unfortunately, it’s very difficult
to discuss the effects of radiation on people without
using technical terms. Here are some of the terms that will
be used in the document:
􀁸􀀃 Ionizing radiation: This is one of two forms of radiation.
It is the most dangerous type of radiation because
of possible adverse biological effects when they pass
through body tissue. X-rays are an example of ionizing
radiation.
􀁸􀀃 Non-ionizing radiation: This is the second form of
radiation. This is less energetic, and causes less harm
to people. Examples of non-ionizing radiation would
be radar and microwave radiation.
􀁸􀀃 Sievert (Sv) - This is the unit of measurement for the
amount of radiation received by a person. The sievert
is the measure of the biological harm that ionizing radiation
may cause. It is most commonly expressed in
millisieverts (mSv) which is one thousandth of a
sievert, or microsievert, which is a much smaller dose,
or one millionth of a sievert (i.e., 1000 microsieverts
per millisieverts).
Ionizing Radiation
Humans cannot escape exposure to ionizing radiation as it
is a naturally occurring part of the environment. Humans
are exposed to it every day in the form of cosmic radiation
from space and terrestrial radiation from earth, which includes
such things as radioactive potassium that we norFSI
- HUMAN FACTORS 10
mally acquire in our diet. In addition, we are also exposed
to man-made sources of radiation, such as diagnostic medical
and dental X-rays and nuclear power plants, although
the overall contribution of these sources is small.
Although very small, both flight and cabin crew members
are exposed to cosmic radiation levels that are higher than
those normally encountered on the ground. At altitudes
flown by airlines, cosmic radiation is present when high
energy subatomic particles, originating for the most part
outside of the solar system, collide with and disrupt atoms
of nitrogen, oxygen, and other particles that make up the
atmosphere. Additional subatomic particles are produced
from these collisions. The particles from beyond the solar
system and particles produced in the atmosphere are referred
to collectively as galactic cosmic radiation.
Another source of in-flight ionizing radiation is solar cosmic
radiation, which comes from several sources, the most
important one from the crewmember’s standpoint being
solar flares. Solar flare particles coming from the sun are
usually too low in energy to contribute to the radiation
level at the altitudes commercial airlines fly. However, on
infrequent and unpredictable occasions, the number and
energies of ejected solar particles are high enough to substantially
increase the does rates at these altitudes.
One of the more uncommon sources of ionizing radiation
is radioactive material that is transported by commercial
air carriers. This material consists mostly of pharmaceuticals
used in medical diagnosis and treatments. Federal
regulations established y the Department of Transportation
(DOT) are specific as to packaging and storage of such
cargo in order to limit radiation levels in areas occupied by
peoples or animals. Again, the hazard radiation from this
source is very low.
Variable affecting the amount of exposure
There are a number of factors that affect the amount of
radiation exposure that a crewmember receives during a
particular flight. These include:
􀁸􀀃 the flight altitude
􀁸􀀃 the duration at that altitude
􀁸􀀃 the geographical latitude of the flight
􀁸􀀃 the stage of the solar cycle
Altitude and Duration
In general, the higher the altitude, the greater the increase
in the cosmic radiation level. For example, in the United
States at sea level, the average dose rate to the average individual
is about 0.035 microsieverts per hour, whereas at
35,000 feet, the dose rate is 4.1 microsieverts per hour over
Oklahoma City and 5.1 microsieverts over Anchorage. The
amount of time spent at altitude will therefore affect the
　
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