Ionizing Radiation

Ionizing radiation is a fast moving particle with an electric charge, or very high energy electromagnetic radiation which can ionize the atoms which absorb it.

Summary of Types of Radiation

There are basically two forms of radiation: Electromagnetic Waves and high speed particles.

Electromagnetic waves are radio waves, microwaves, heat, light, UV rays, X-rays, and gamma rays. At low frequencies, radio waves and microwaves act like waves, and pass thru us. However, as the wave length shortens, they become more like particles and can do damage to living tissue.

High energy electromagnetic waves, can be absorbed by an atom inside our cells. This can knock an electron into a higher orbital, or cause it to break free from the atom itself, leaving an ion behind. (An ion inside our cells may damage them.)

High speed particles include things like beta particles (high speed electrons), alpha particles (high speed helium nucleus), neutrons, neutrinos, mesons (a heavy relative of the electron), cosmic rays, etc.

Particles that carry a charge (such as beta or alpha particles) interact strongly with the matter they travel thru. This rapidly slows them, and eventually they attach themselves to an atom (electrons) or pick up two electrons (alpha particles). Once they are slowed and neutral in charge, they are harmless.

However, while they are travelling quickly, they can tear thru living tissue and knock electrons off of atoms in the cell, leaving a trail of ions in their wake. These ions are extremely reactive, and can do damage to a cell.

Note that neutrons are neutral, and do not ionize cells they travel thru. However, they may get absorbed into some atom. If this atom is stable with an extra neutron then all is well. However, there is a good chance that the heavier atom is unstable and will beta decay. This beta particle IS ionizing radiation, which can damage cells.

How ionizing radiation damages cells

Ions will chemically combine in all sorts of ways, and may damage the cell they are in. (Or it may combine with something it a way which belongs in the cell, in which case no damage was done.) It some exotic chemical is formed, or if a large useful molecule (such as a protean or enzyme) is damaged, it may hurt the cell.

This damage may be repaired (usual), or it may kill the cell (rare). Very rarely, it can damage the genetic material of the cell causing a cancer.

Summary

Radiation which can ionize atoms can damage living tissue. For the most part, non-ionizing radiation does not. (But see the neutrons discussion above.)