Exposure Pathways

Any release of radioactive material is a potential source of radiation exposure to the population. The type of radiation received (alpha, beta, gamma rays, or X-rays), the way a person is exposed (internally or externally), and how long a person is exposed are all important factors in estimating health effects.

The risk from exposure to a particular radioactive element depends on the following:

• The energy of the radiation it emits
• Its activity (how often it emits radiation)
• The rate at which the body metabolizes and eliminates the radionuclide following ingestion or inhalation
• Where the radionuclide concentrates in the body and how long it stays there

The risk that exposure to a radioactive element will cause a particular health effect also depends on whether exposure is internal or external.

Internal exposure is when radioactive material gets inside the body through the process of eating, drinking, breathing, or injection (from certain medical procedures). Outside the body, alpha particles are too large to pass through the skin or a thin layer of clothes. But when inhaled or ingested in significant quantities, alpha and beta particles pose a serious health threat.

External exposure (also known as direct exposure) is when the radioactive source is outside of the body. X-rays and gamma rays can pass through the body, depositing energy as they go.

To learn more about Ionizing Radiation visit our Ionizing Radiation Safety Online Training web page.