Radiation comes in two forms, Ionizing and Non-ionizing. Ionizing radiation removes electrons from atoms and molecules of materials that can include air, water, and living tissue. Examples of Ionizing radiation are X-rays, Gamma rays, and also alpha, beta, and gamma rays from radioactive decay.

Non-ionizing radiation differs from ionizing radiation in the way it acts on materials. Unlike x-rays and other forms of ionizing radiation, non-ionizing radiation does not have enough energy to remove electrons from atoms and molecules. They do have the ability to heat substances. Non-ionizing radiation can include radiofrequency, microwaves, and infrared radiation.

Radiation can interact with DNA directly and cause damage by breaking bonds in the DNA or indirectly by breaking water molecules surrounding the DNA. When these water molecules are broken, they produce free radicals, which are unstable oxygen molecules that can damage cells and organs.

Once a cell is damaged, three things can happen;

1. It repairs itself and goes back to working as normal
2. The cell damage is not repaired, or it incorrectly repairs itself, meaning the cell is now changed. This change could eventually lead to cancer
3. The cell damage is too much and it dies

Every day we are exposed to radiation in some form, from natural sources (e.g. cosmic radiation, solar radiation, terrestrial radiation) and manmade sources (e.g. X-rays, Computed Tomography (CT) scans, Positron Emission Topography (PET) scans). These sources of radiation are at very low doses and are unlikely to cause harm. It is possible for the increased likelihood of problems to develop over time in some circumstances, such as excessive Ultraviolet exposure causing skin cancer, or living in an area with high Radon levels (a natural radioactive gas) causing lung cancer.

In the CBRN context, the risk is where deliberate exposure of high levels of radiation is used with the intent to cause harm. This could be done in 2 forms:

Use of radioactive decay:

Radioactive decay is the process in which a radioactive atom spontaneously gives off radiation in the form of energy or particles to reach a more stable state. There are 4 types of radiation given off:

Alpha –

• Alpha particles are large particles that travel up to an inch in the air
• Alpha particles are very easy to block and thin materials will stop them, such as a sheet of paper
• Alpha particles don’t present an external hazard to people as they can’t get through our outer layer of dead skin cells
• Alpha particles can be very damaging to cells inside our bodies, for example, if we breathe in or eat alpha emitting radioactive material or if the radioactive material is introduced through an open wound

Beta –

• Beta particles are smaller particles that travel several feet in air
• Beta particles can be blocked effectively with a few inches of plastic
• Beta particles carry enough energy to cause burns on exposed skin and present an internal hazard if we breathe in or eat beta emitting radioactive material, or if the radioactive material is introduced through an open wound.

Gamma –

• Gamma rays can travel many yards in air
• Gamma rays pose more of an external hazard because of their ability to go through materials
• It takes a few inches of lead or other dense substances to block gamma rays
• Gamma rays can be an internal hazard if we breathe in or eat gamma-emitting radioactive materials, or if the radioactive material is introduced through an open wound, but the damage they do to cells inside our bodies is not as severe as that done by alpha and beta particles

Neutrons –

• Neutrons are neutral particles with no electrical charge that can travel great distances in the air
• As neutrons travel through matter, they crash with atoms. These atoms can become radioactive
• Neutrons are more effective at damaging cells of the body than any other forms of ionizing radiation, such as x-rays or gamma rays
• In order to block neutrons, very thick, heavy materials such as lead, concrete, rock, or dirt are required

Within a terrorism context, food and drink products could be poisoned with alpha or beta particles, causing harm to individuals who consume them. Using Gamma or Neutron emitting particles could cause harm to people within the vicinity of the radioactive material emission.