yellow symbolThis section of the EHS website was developed to provide additional information and resources to those of you whose work involves exposure to radiation AND to those of you, including the general public, who do not work around radiation sources but would like to know a little bit about radiation. Many individuals have an interest in this topic since 9/11.

You will find the section on Radiological Emergency Response useful if you are interested in information and guidance regarding the risks and proper response associated with an emergency such as a terrorist event involving the use of radioactive material.

There is a wealth of information on radiation related topics available on the internet today. Rather than try to reproduce all of that information on this site, we have provided short discussions of various topics and then related links that will take you to sites which can provide you with all the information you are looking for (and more).

If you have any questions regarding any of this information, please feel free to contact our office at 982-4911. Enjoy!

What is Radiation?  wave

There are many different types of radiation that we are all exposed to in our daily lives. Radio waves, visible light, microwaves; these are all types of radiation that are part of what is called the electromagnetic spectrum. X-rays and gamma rays, the type of radiation that most people think of when you talk about "radiation", are part of this electromagnetic spectrum as well. To start with the basics, visit the following sites:

Radiation and Life, Uranium Information Centre, Australia
Radiation Protection, NRC, United States
Radiation: Non-Ionizing and Ionizing, EPA, United States

X-rays, gamma rays and particulate radiation such as alphas, betas and neutrons are capable of creating ionization in matter and are called ionizing radiation. Ionization is a process in which an electron is removed from its orbit around the atom's nucleus, resulting in a positively charged ion and a free negative electron. Ionization in biological material can lead to damage of cells and biological systems in the body if a large enough dose of radiation is received by the body. To understand the ionization process, you should first review the structure of the atom at

See for a discussion of ionizing vs. non-ionizing radiation.

Radiation Terms and Definitions

When we talk about radiation and radiation dose, we use special terms such as rad or rem. To understand dose and radiation measurement, you must have a basic understanding of what these words mean.

See for informationon Radiation Terms.

The biological effects from exposure to ionizing radiation depend on the amount and type of radiation you are exposed to. Not all radiation exposure is dangerous. We are all exposed to small amounts of radiation every day of our lives from naturally occurring radionuclides in the air, water, food and in the earth and building materials surrounding us. This radiation is called background radiation.

Just for fun - Go to to calculate your average dose from background radiation exposure.

Radiation Risks

The current assumption in the radiation protection community at this time is that the risk of harmful effects from radiation increases with the amount of dose received. The Nuclear Regulatory Commission has set dose limits for radiation workers and the general public. The dose limit for a member of the general public is 100 mrem per year (not including exposure to natural background radiation). The whole body dose limit for a radiation worker is 5000 mrem per year. These limits are believed to be conservative and to represent very minimal risk for harmful effects.

See or for a discussion of health effects associated with radiation exposure and associated risks.

Minimizing Your Dose

Avoiding exposure to all radiation is impossible because of natural background radiation. Avoiding exposure to large or harmful amounts of radiation is fairly simple. If you remember these three words, you can keep your doses low.

Minimize the time you spend near the source of radiation Keep as much distance between you and the source as possible and use shielding if possible to stop the radiation. For additional information on ways to minimize your radiation dose:

Go to or

Nuclear Power

Many people associate the word radiation with nuclear power. Unfortunately, since 3 Mile Island, it is a negative association. Much of the negative association is a result of lack of knowledge and factual information. Visit the following websites and decide for yourself. or

Radiological Emergency Response

Since September 11, there has been heightened concern that terrorists will use radioactive material to make a dirty bomb.

What is a "dirty bomb"?

A "dirty bomb" or radiological dispersal device (RDD) is a conventional explosive containing radioactive material. A conventional explosive can be used as a means to spread radioactive contamination. It is not a nuclear bomb and does not produce a nuclear explosion.

What would be the danger to the public if terrorists were successful in acquiring radioactive material and detonating a dirty bomb?

The radioactive material could contaminate a large area, a few city blocks or more, depending on the type and amount of radioactive material used, amount and type of explosive, weather conditions and other factors. It is unlikely that significant immediate health effects or prompt fatalities would result, other than from the explosion itself, because people would run away from the explosion and the radioactive material would disperse, reducing the potential for high radiation exposure. Over the long-term, people who were contaminated or exposed to elevated radiation levels may have an increased risk of cancer.

How would officials respond to a dirty bomb attack?

Officials would restrict public access to the contaminated area, call in experts to assess the degree of radioactive contamination and decontaminate the area. People in the vicinity of the explosion would be checked for contamination, decontaminated if necessary, and receive follow-up medical attention if needed.

What should you do in the event of a dirty bomb attack?

  • Move away from the immediate area--at least several blocks from the explosion--and go inside. This will reduce exposure to any radioactive airborne dust.
  • Turn on local radio or TV channels for advisories from emergency response and health authorities.
  • If facilities are available, remove clothes and place them in a sealed plastic bag. Saving contaminated clothing will allow testing for radiation exposure.
  • Take a shower to wash off dust and dirt. This will reduce total radiation exposure, if the explosive device contained radioactive material.

Go to for a fact sheet on Dirty Bombs and for additional response information provided by the U.S. Nuclear Regulatory Agency. This fact sheet also provides a list of other agencies that have response capabilities and responsibilities.

Go to for information on the U.S. Environmental Protection Agency'’s Response Plans.

This information on this page was compiled/created by Deborah Steva, University of Virginia, Environmental Health & Safety July 2004, updated November 2010.

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