Background Radiation and Contamination

Background Radiation comes from many sources

Background radiation is the low-level radiation that’s around us all the time. You should always measure and subtract the background radiation from your results. It comes from:

• Radioactivity of naturally occuring unstable isotopes which are all around us-in the air, in food, in building materials and in the rocks under our feet

• Radiation from space, which is known as cosmic rays. These come mostly from the sun. Luckily, the earth’s atmosphere protects us from much of this radiation

• Radiation due to human activity or nuclear waste exists. But this represents a tiny proportion of the total background radiation

  The radiation doss tells you the risk of harm to body tissues due to exposure to radiation. It’s measured in sieverts. The dose from background radiation is small, so millisieverts are often used. Your radiation dose varies depending on where you live or if you have a job that involves radiation

Exposure to radiation is called irradiation

• Objects near a radioactive source are irradiated by it. This simply means they’re exposed to it
• Irradiating something does not make it radioactive
• Keeping sources in lead-in boxes, standing behind barriers or being in a different room and using remote-controlled arms are all ways of reducing the effects of irradiation

Contamination is radioactive particles getting onto objects

• If unwanted radioactive atoms get onto or into an object, the object is said to be contaminated.
• These contaminating atoms might then decay, releasing radiation which could cause you harm
• Contamination is especially dangerous because radioactive particles could get inside your body
• Gloves and tongs should be used when handling sources, to avoid particles getting stuck to your skin or under your nails. Some industrial workers wear protective suits to stop them breathing in particles

The seriousness of irradiation and contamination depends on the source

Contamination or irradiation can cause different amounts of harm

• Outside the body, beta and gamma sources are the most dangerous. This is because beta and gamma can penetrate the body and get to the delicate organs. Alpha is less dangerous because it can’t penetrate the skin and is easily blocked by a small air gap. High levels of irradiation from all sources are dangerous, but especially from ones that emit beta and gamma

• Inside the body, alpha sources are the most dangerous, because they do all their damage in a very localised area. So contamination, rather than irradiation, is the major concern when working with alpha sources. Beta sources are less damaging inside the body, as radiation is absorbed over a wider area, and some passes out of the body although. Gamma sources are the least dangerous inside the body, as they mostly pass straight out-they have the lowest ionising power

  The more we understand about how radiation affects our bodies, the better we can protect ourselves when using it.