What is radiation?
Radiation is energy in the form of particles or waves. The term “radiation” is commonly used to refer to what scientists call “ionizing radiation,” which is emitted from the nuclei of atoms and is harmful to humans.

Every day, people are exposed to naturally occurring ionizing radiation from elements in the soil and air, cosmic rays, and even materials in the human body itself. Man-made devices such as X-ray machines and nuclear power plants also generate radiation, although their output is tightly controlled to prevent harm.

Some forms of radiation—including alpha and beta particles—are harmful only when they are ingested or come into contact with skin, and they can be blocked by something as simple as a sheet of paper or a plate of glass. But “penetrating radiation”—including gamma rays and the neutron radiation produced in nuclear fission—can travel hundreds of yards through the air, penetrate normal walls or floors, and affect the entire human body.

How could a radiological attack expose people to harmful radiation?
Two ways.

One form of attack could spread radiation by placing concentrated, highly radioactive material in a city or by sabotaging a nuclear power plant.

A second form of radiological attack could involve spreading radioactive materials with an aerosol spray or a dirty bomb. The dust and debris thrown up by a dirty bomb explosion might land on people’s skin and then be inhaled, ingested, or absorbed through wounds. Victims might also be exposed to radiation from radioactive materials scattered nearby.

Victims near a dirty bomb attack might also absorb radioactive contaminants into their bodies. Radiation released by radioactive materials inside the body can damage tissues such as the liver, the thyroid, the kidneys, and bones, and increase a victim’s chances of getting cancer.

What would be the initial reaction to such attacks?
To stop the exposure to radiation, victims would have to be decontaminated by removing irradiated clothing, washing the skin, and purging inhaled or ingested materials from inside the body. The surrounding area would also need to be decontaminated to remove radioactive material, keep radioactive dust and debris from spreading, and protect food and water supplies.

What health conditions can result from exposure to radiation?
The exact biological effects of radiation exposure are not fully understood, scientists say. But we do know of two possible effects: the direct damage known as “radiation sickness” and an increased likelihood of developing cancer later on.

What is radiation sickness?
The illness takes different forms depending on the degree of exposure.

• Exposure to up to 20 times the annual background dose of radiation received by the average American would have no discernible effect.
• Up to 400 times the annual background dose would cause mild changes in the composition of the human blood and some temporary nausea or vomiting.
• Up to 1,000 times the annual background dose would cause nausea, vomiting, hair loss, reduced immune system function, and serious blood disease.
• Still higher doses—such as those that would hit unshielded workers inside a catastrophically sabotaged nuclear reactor—could cause severe dehydration, anemia, hemorrhaging, and infections. Such doses would kill 80 to 100 percent of the people exposed.