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Biological effects of ionizing radiation

Broken chromosomes

When an organism is exposed to radiation, the amount of damage it suffers will depend on the energy carried by the radiation. Ionizing radiation carries sufficient energy to be dangerous to living cells.

Several things can happen when ionizing radiation hits a living cell: 

  • the cell is not damaged as the radiation passes through it
  • the cell is damaged, but is able to repair itself
  • the cell is killed
  • The cell’s Glossary Link: DNA is damaged but remains able to reproduce itself, in its modified form. This cell could become malignant and turn into a cancer.

If the cell is a sex cell, the radiation may cause a mutation in a gene.
What actually happens to a cell will depend on depending on the absorbed dose of radiation, the type of radiation and the cell type.


Massive cell death can sometimes be beneficial. In a radiotherapy treatment, for example, a tumour may be eradicated by submitting it to intense X-rays.

Lower energy radiation such as UV Light can still cause painful sunburn and has been linked to skin cancer.

Measuring radiation and risk

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Text equivalent:

Avoid harm

We should take all possible precautions when working with high energy EM radiation such as X and gamma rays.
Precautionary prinicpleText equivalent:

Precautionary principle

If we are not yet certain whether a substance is damaging or safe to handle, we should err on the side of safety.


In 1898 Pierre and Marie Curie discovered the element Radium. For years, people who worked with Radium did not use protection. Millions of people bought medicines made with Radium, which promised to cure many diseases. Only after a large number of people got ill or died due to exposure to Radium, people understood its lethal power.

Do you believe that we might be using products today which will in the future be discovered to be lethal?  Which ones?