People are exposed to natural radioactive materials every day from space (cosmic rays) and the soil, water and air. There also are manmade sources of radiation, such as X-rays and CT scans.

According to the International Atomic Energy Agency(IAEA)?Safety Standards, exposure to radiation is defined in terms of:

Planned exposure situations	A planned exposure situation arises from the planned operation of a source or from a planned activity that results in an exposure from a source.?Those exposed can include workers, patients and the public.?
Emergency exposure situations	?An emergency exposure situation arises as a result of an accident, a malicious act, or any other unexpected event, and requires prompt action in order to avoid or reduce adverse consequences.
Existing exposure situations	An existing exposure situation is a situation of exposure which already exists when a decision on the need for control needs to be taken.

In a nuclear power plant accident, the general population is not likely to be exposed to doses high enough to cause such effects. Rescuers, first responders and nuclear power plant workers are more likely to be exposed to doses of radiation high enough to cause acute effects.

Long-term effects from radiation exposure:

Exposure to radiation can increase the risk of cancer. Among the Japanese atomic bomb survivors, the risk of leukaemia increased a few years after radiation exposure, whereas the risks of other cancers increased more than 10 years after the exposure.

Radioactive iodine can be released during nuclear emergencies. If breathed in or swallowed, it will concentrate in the thyroid gland and increase the risk of thyroid cancer.

Among persons exposed to radioactive iodine, the risk of thyroid cancer can be lowered by taking potassium iodide pills, which helps prevent the uptake of the radioactive iodine.

The risk of thyroid cancer following radiation exposure is higher in children and young adults.

Radiation protection:

Radiation protection, sometimes referred to as radiological protection, is a general term applied to the protection of people and the environment from the harmful effects of ionizing radiation.

Radiation protection can be divided into:

Occupational radiation protection , which is the protection of workers in situations where their exposure is directly related to or required by their work;

Medical radiation protection, which is the protection of patients exposed to radiation as part of their diagnosis or treatment; and

Public radiation protection, which is the protection of individual members of the public and of the population in general.

Then how to protect yourself from being harmed:

Time: The amount of radiation exposure increases and decreases with the time people spend near the source of radiation.

In general, we think of the exposure time as how long a person is near radioactive material. It's easy to understand how to minimize the time for external (direct) exposure. Gamma and x-rays are the primary concern for external exposure.

However, if radioactive material gets inside your body, you can't move away from it. You have to wait until it decays or until your body can eliminate it. When this happens, the biological half-life of the radionuclide controls the time of exposure. Biological half-life is the amount of time it takes the body to eliminate one half of the radionuclide initially present. Alpha and beta particles are the main concern for internal exposure.

Distance: The farther away people are from a radiation source, the less their exposure.

How close to a source of radiation can you be without getting a high exposure? It depends on the energy of the radiation and the size (or activity) of the source. Distance is a prime concern when dealing with gamma rays, because they can travel long distances. Alpha and beta particles don't have enough energy to travel very far.

As a rule, if you double the distance, you reduce the exposure by a factor of four. Halving the distance, increases the exposure by a factor of four.