Radiation Exposure
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Radiation Exposure

(Ionizing Radiation Exposure)


Radiation is energy that is sent out from a source. Radiation exposure occurs when a person encounters this energy.

There are different forms of radiation. Some come from nature and some are manmade. There are the ultraviolet (UV) rays from the sun. There is also the radiation used in microwaves to heat up last night’s leftovers. Radiation is divided into two categories: ionizing and nonionizing. Ionizing radiation is a high-frequency radiation that is able to damage cells. It has also been linked to cancer and other health problems. Nonionizing radiation is low in frequency and is not known to cause cancer (except for UV rays).

Ionizing RadiationNonionizing Radiation
Gamma raysVisible light
X-raysInfrared rays
UV rays (high-energy)Microwaves
Sub-atomic particlesRadio waves
UV rays (low-energy)

This fact sheet focuses on exposure from ionizing radiation.


A person can be exposed to ionizing radiation from:

  • X-rays
  • Radiation therapy used to treat certain types of cancer
  • Radioactive elements in the soil or public works systems (eg, water supply)
  • Workplace environment (eg, uranium mines)
  • Radiation from nuclear disasters

External Radiation of a Cancerous Growth

Radiation of Tumor

© 2011 Nucleus Medical Media, Inc.

Risk Factors

You are at risk for radiation exposure if you are near sources that generate it. Although ionizing radiation has been linked to health problems, not all people exposed develop problems. For example, having a chest x-ray does expose you to some radiation. But the dose is low and your risk for health problems is low. Other tests, like CT scans, expose a person to higher doses. Health effects risk from CT scans, while still small, is higher than the risk with a regular x-ray.

The greater the exposure, the more likely there will be health effects. For example, doctors treat some cancers with high radiation doses. The treatment not only kills cancer cells, but also healthy cells. Also, people exposed to large nuclear accidents can be injured by the high radiation amounts.


There is also the risk of cancer. Cancer may take years to develop after exposure. Some cancers linked with ionizing radiation exposure are:


Exposure can cause radiation sickness. Symptoms include:

  • Nausea
  • Weakness
  • Hair loss
  • Diarrhea
  • Bleeding
  • Burns
  • Loss of organ functions


The healthcare team will:

  • Ask about your symptoms and medical history
  • Do a physical exam

They may also do the following:

  • Blood, stool, and urine tests
  • Measure amount of radiation absorbed by your body using a radiation survey meter


If you have been contaminated, the healthcare team will help remove the material from you so it will stop damaging your cells. You may be bathed in lukewarm water and soap. The team will also monitor your radiation levels.

If you have radiation sickness, you will be monitored and treated closely while your body heals. Treatment depends on what parts of your body are damaged.

If your body has absorbed radioactive iodine, you may be treated with potassium iodine. Radioactive iodine can be absorbed by your thyroid gland. This can injure the gland and lead to thyroid cancer. Potassium iodine blocks the absorption.


There are policies to prevent the public from dangerous levels of radiation. Safety measures are taken when it is used for medical treatment or is part of a work environment. But the best prevention is to stay away from its sources.


Centers for Disease Control and Prevention

Radiation Emergency Medical Management United States Department of Health and Human Services


BC Centre for Disease Control

Health Canada


Brenner DJ. Should we be concerned about the rapid increase in CT usage? Rev Environ Health. 2010 Jan-Mar;25(1):63-68. Review.

Colang JE, Killion JB, Vano E. Patient dose from CT: a literature review. Radiol Technol. 2007 Sep-Oct;79(1):17-26. Review.

Frequently asked questions on potassium iodide (KI). United States Food and Drug Administration website. Available at:
http://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm072265.htm#KI%20do. Updated March 18, 2011. Accessed March 28, 2011.

Gross whole-body contamination. United States Department of Health and Human Services website. Available at: http://www.remm.nlm.gov/ext_contamination.htm#wholebody. Updated March 14, 2011. Accessed March 28, 2011.

Health effects. Radiation protection. United States Environmental Protection Agency website. Available at: http://www.epa.gov/radiation/understand/health_effects.html. Updated March 24, 2011. Accessed March 28, 2011.

How to perform a survey for radiation contamination. United States Department of Health and Human Services website. Available at: http://www.remm.nlm.gov/howtosurvey.htm. Updated March 14, 2011. Accessed March 28, 2011.

Potassium iodide (KI). Centers for Disease Control and Prevention website. Available at:
http://www.bt.cdc.gov/radiation/ki.asp. Updated March 17, 2011. Accessed March 28, 2011.

Radiation emergency medical management: choose appropriate algorithm—evaluate for contamination and/or exposure. United States Department of Health and Human Services website. Available at: http://www.remm.nlm.gov/newptinteract.htm#skip. Updated March 14, 2011. Accessed March 28, 2011.

Radiation exposure and cancer. American Cancer Society website. Available at:
http://www.cancer.org/cancer/cancercauses/othercarcinogens/medicaltreatments/radiation-exposure-and-cancer. Updated March 29, 2010. Accessed March 30, 2011.

Last reviewed April 2011 by Marcin Chwistek, MD

Last updated Updated: 4/6/2011

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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