A guide to understanding radiation and radioactive contamination by REAC/TS physicians and health physicists

Q: What is radiation?
A: Radiation is energy, in the form of particles or electromagnetic rays, released from radioactive atoms. The three most common types of radiation are alpha particles, beta particles, and gamma rays.

Q: Where does radiation come from?
A: Radiation comes from many sources, some natural and some man-made. Naturally occurring radioactive materials, such as uranium, thorium and radon are found in the Earth’s crust. Man-made sources include radiation-generating devices such as x-ray machines and CT scanners. Some radioisotopes—the radioactive form of an element—are man-made, for example, plutonium.

Q: How is radiation measured?
A: There are two systems of measure used for radiation, the Common System used in the U.S. and the International System used by other countries. The most common units used are rad and rem in the United States and gray and sievert in all other countries.

Conversion Table

1 gray (Gy) 100 rads
1 milligray (mGy) 100 millirads (mrads)
1 sievert (Sv) 100 rem
1 millisievert (mSv) 100 millirem (mrem)
1 rad 10 milligray (mGy)
1 millirad (mrad) 10 micrograys (µGy)
1 rem 10 millisieverts (mSv)
1 millirem (mrem) 10 microsieverts (µSv)

Rad and gray are used to describe the amount or “dose” of energy absorbed by a person or animal. Rem and sievert are used when discussing how much damage that dose of radiation might do to the body. Different types of radiation affect the body differently, so the same amount, as measured in rads or grays, will have different values in rems and sieverts depending on its source.

Q: What radiation doses are considered to be safe?
A: The biological effects of radiation are influenced by a number of factors. However, radiation dose limits have been set for workers in the U.S. nuclear industry that are intended to minimize the risks associated with radiation exposures. U.S. radiation workers are allowed to receive up to 5,000 mrem (50 mSv) per year. Emergency response guidelines allow for higher doses depending on what has to be accomplished. The U.S. Environmental Protection Agency provides information that state and local authorities can use to help protect people from receiving an amount of radiation that might be dangerous to their health.

Q: What is radiation exposure?
A: Radiation exposure occurs when one is in the presence of radioactive materials. People are naturally exposed to small amounts of radiation every day. In fact, some foods and common household items, such as smoke detectors, are slightly radioactive.

Q: What is radioactive contamination?
A: A person becomes contaminated when they have radioactive material on them or in them. External contamination is on our skin or clothing. Internal contamination is when we breathe in, swallow or otherwise get radioactive materials inside the body.

Q: What is the difference between radiation exposure and radioactive contamination?
A: When a person is exposed to radiation, there is no transfer of radioactive material, for example, an X-ray. When a person is contaminated with radioactive material, they take that material with them wherever they go, until they are decontaminated.

Q: How is decontamination typically performed?
A: Removing outer clothing, washing the contaminated area with mild soap and water or showering are typical methods for decontamination.

Q: What about contamination that’s inside my body?
A: Internal contamination is treated with medications specific to the materials to which you are exposed. Potassium iodide or KI, Prussian Blue, and DTPA are a few of the most common radiation treatment drugs.

Q: How do Prussian Blue and DTPA work?
A: Watch the videos about Prussian Blue and DTPA for the answer.

Q: When do people need to be “treated” for radiation exposure or contamination?
A: If someone may have accidently been exposed to radiation, they should seek medical advice to determine what, if any, treatment is needed. Based on the type of radiation, the situation, the patient’s symptoms, how long the person was exposed and whether he or she is contaminated, a physician, often assisted by a radiation expert known as a health physicist, will provide the patient with information about what treatment may be needed.

Q: If there is a radiation accident, should I take potassium iodide, also known as KI?
A: KI is a medication that blocks the thyroid gland from absorbing radioactive iodine. It works by providing all the iodine the gland needs so that it doesn’t absorb any of the radioactive iodine. A nuclear power plant accident or nuclear bomb detonation releases radioactive iodine, but KI should only be taken if a significant amount is released. KI should be taken only when advised by emergency management officials, public health officials or your doctor. You can get KI without a prescription, but people who are allergic to iodine or have some health conditions should not take it. The U.S. Food and Drug Administration provides additional details about KI use, dose and health risks.