Prospect or suspect – uranium mining in AustraliA
Box 1 | The danger of ionising radiation
We are all exposed to natural ionising radiation – some of it from radioactive materials in rocks and soil, and some of it produced by cosmic rays which continually bombard us from outer space. We also expose our bodies to ionising radiation from medical or dental X-rays. Living with the effects of low-level ionising radiation is one of the normal hazards of life.
People are exposed to high doses of ionising radiation when nuclear explosions or nuclear accidents occur. High doses of ionising radiation destroy body tissues, and death occurs immediately or soon after exposure. However, the effects of lower doses may not show up for years after exposure and are due to various changes in DNA molecules and chromosomes. There are at least four ways in which low doses of ionising radiation can affect cells:
- Low doses of ionising radiation can bring about delay in the process
of cell division, but the reasons behind this phenomenon are not
known.
- Radiation-induced mutations seem to be brought about by the deletion
of small pieces of chromosomes during the process of chromosome
breakage and repair, and if such changes occur in egg-producing
or sperm-producing cells they may be inherited by the offspring.
- Ionising radiation can induce the abnormal growths of cells. Advanced
cancer cells usually have an abnormal complement of chromosomes,
but other smaller genetic changes may also play a part in carcinogenesis.
Since chromosome damage is most likely to happen in dividing cells,
ionising radiation is most likely to cause cancer in those parts
of the body where cells are actively dividing.
- Ionising radiation kills rapidly dividing cells. This specific effect of ionising radiation can be put to use. Cancer cells produced by human genetic defects or other causes divide rapidly, which is why they are dangerous. Careful application of radiation (radiation therapy) can therefore be used to kill the cancer cells while leaving normal cells relatively undamaged.
As with many public health issues, it is not the increased risk to an individual that is of greatest concern, but rather the effect on the total population. For example, while a change in risk from 0.1 to 0.2 per cent is not a big increase in risk for an individual, the number of people affected in a city of l million would rise from 1000 to 2000, with clear implications for hospital beds and other health facilities.
Related sites
Radiation and life (World Nuclear Association)
How nuclear radiation works (How Stuff Works, USA)
Page updated August 2009.