22.5 - Why Radiation Is Harmful

How ionising radiation damages living cells

• Ionising radiation enters living cells and ionises the atoms and molecules inside them.
• Removing electrons damages or destroys these molecules, which damages the cell.
• The amount of harm depends on the radiation dose.

Lower dose - Mutation and cancer

• A lower dose tends to cause minor damage without killing the cell.
• This damage can mutate the cell's DNA.
• A mutated cell may divide uncontrollably, leading to cancer.

Higher dose - Radiation sickness

• A higher dose kills cells outright.
• Killing a large number of cells at once causes radiation sickness, with symptoms such as vomiting, tiredness and hair loss.
• Very high doses can be fatal.

Ionising power

• The more ionising the radiation, the more damage it causes to cells.
• Most to least ionising: alpha → beta → gamma.

Irradiation

• Irradiation is the process of exposing an object to radiation.
• Irradiating an object does not make it radioactive.
• Irradiation stops as soon as the source is removed or shielded.

Reducing the risk of irradiation

• Store sources in lead-lined boxes.
• Stand behind barriers or work from a different room.
• Use long-handled tools to stay as far from the source as possible.
• Limit the time spent near the source.
• Wear photographic film badges (dosimeters) so total exposure can be monitored and kept within safe limits.

Contamination

• Contamination occurs when unwanted radioactive atoms get onto or into an object or person.
• The contaminating atoms decay, emitting radiation directly on or inside the body.
• Contamination poses a high risk because the radioactive material stays in place, exposing tissues to radiation until it is removed or decays away.

Precautions against contamination

• Wear gloves and protective clothing so radioactive material can't touch the skin.
• Use tongs to avoid touching sources.
• Wear masks or protective suits to avoid breathing in radioactive dust or gas.