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Radioactive substances

Hazards of radiation

Radiation and living cells

When radiation collides with molecules in living cells it can damage them. If the DNA in the nucleus of a cell is damaged, the cell may become cancerous. The cell then goes out of control, divides rapidly and causes serious health problems.

yellow circle with 3 black pie shaped segments inside

Radiation 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 that these effects are opposites and make sure you get them the right way around.

Back to Radiation and the Universe index

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