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estimate of airborne contamination. Under less adverse conditions, more
sophisticated instrumentation and techniques should be applied.

3.3 Radiation dose reduction
There are three primary means of reducing the radiation dose from sources
external to the body: time, distance, and shielding.
For a given source of radiation, the amount of radiation energy deposited in
the body is related to how long one is exposed. Therefore, reducing the duration of
an individual's exposure to radiation will decrease the dose.
Increasing the distance between an individual and a radiation source is an
important means of reducing radiation exposure, because the intensity of the
radiation is inversely proportional to the square of the distance from the radiation
source. When dealing with planar sources such as radioactive fallout on the
ground, the decrease in dose with distance is much less.
Shielding is useful for absorbing radiation energy. If enough interactions
occur in the shielding material, then much of the radiation is prevented from
reaching the body's tissues. Alpha radiation can be stopped by a piece of paper.
Beta radiation can be blocked by about a centimeter of plastic. Clothing and the
outer layers of skin cells provide some protection from beta radiation outside the
body. Gamma radiation, however, may require many centimeters of lead or meters
of concrete for shielding.
Once a radioactive material is taken into the body, the protective measures
of distance and shielding cannot be applied. However, the duration of internal
exposure may be reduced by increasing the rate of excretion of the radioactive
material through elimination of body fluids or solids. Increasing the rate of
elimination is very specific to the radionuclide and its chemical form. It can be

done for some radionuclides (e.g., tritium and iodine) by increasing the amount of
fluids entering the body. For other radionuclides (e.g., plutonium) potentially toxic
cheating agents can be considered.
The primary means of protection from internal radiation exposure is to
prevent radioactive materials from entering the body in the first place. Appropriate
respiratory protection can prevent the inhalation of airborne radioactive materials.
Ingestion is prevented by not eating, drinking, or smoking where radioactive
materials are present.

3.4 Effects of radiation on the human body
The risk of illness depends on the dose. Very low doses of radiation are all
around us all the time, and they do not have any effect. It also depends on the area
of the body that is exposed.
If the whole body is exposed to, say, 1,000 rads within a short time, this
could be fatal. However, far higher doses can be applied to a small area of the body
with less risk.
After a mild dose, the person may experience symptoms for just a few hours
or days. However, a repeated or even a single, relatively low dose that produces

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