Dangers of ionising radiation

Radiation and living cells

When radiation collides with molecules in living cells it can damage them. This can cause a mutation. If the DNA in the nucleus of a cell is damaged, the cell may become cancerous. In this case the cell divides rapidly and causes serious health problems.

Coloured scanning electron micrograph (SEM) of melanoma cancer cells.
Coloured scanning electron micrograph (SEM) of melanoma cancer cells
Radiation warning symbolRadiation warning symbol

The greater the dose of radiation a cell gets, the greater the chance that the cell will become cancerous. However, very high doses of radiation can kill the cell completely. We use this property of radiation to kill cancer cells, and also harmful bacteria and other micro-organisms.

The hazard symbol is shown on containers of radioactive substances to warn of the danger.

Alpha, beta and gamma radiation

The degree to which each different type of radiation is most dangerous to the body depends on whether the source is outside or inside the body.

If the radioactive source is inside the body, perhaps after being swallowed or breathed in:

  • alpha radiation is the most dangerous because it is easily absorbed by cells
  • beta and gamma radiation are not as dangerous because they are less likely to be absorbed by a cell and will usually just pass right through it

If the radioactive source is outside the body:

  • alpha radiation is not as dangerous because it is unlikely to reach living cells inside the body
  • beta and gamma radiation are the most dangerous sources because they can penetrate the skin and damage the cells inside

Notice these effects are opposites.