Dangers and Safety with Radiation

This lesson covers the hazards of ionising radiation, the difference between irradiation and contamination, safety precautions, and background radiation — as required by the Edexcel GCSE Physics specification (1PH0), Topic 6: Radioactivity. You need to understand how radiation damages living cells, how to minimise risk, and what contributes to background radiation.

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How Does Radiation Damage Living Cells?

Ionising radiation (alpha, beta and gamma) is dangerous because it can ionise atoms in living cells. When radiation passes through biological tissue, it can:

1. Knock electrons off atoms in important molecules, particularly DNA.
2. This can damage or break the DNA molecule.
3. Damaged DNA may cause cells to divide uncontrollably → this can lead to cancer.
4. Very high doses can cause radiation sickness — where cells are killed outright, leading to nausea, organ failure and potentially death.

Effects of Radiation on Cells

Dose Level	Effect
Low dose over time	Increased risk of cancer (mutations in DNA)
High dose in a short time	Radiation sickness — cell death, organ damage, potentially fatal

Exam Tip: When explaining why radiation is dangerous, always link your answer to ionisation: radiation ionises atoms in DNA → DNA is damaged → mutations occur → this can cause cancer. Simply saying "radiation is dangerous" without this chain of reasoning will not earn marks.

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Irradiation vs Contamination

This is an important distinction that is frequently tested in the exam.

Irradiation

Irradiation means being exposed to radiation from an external source — the radioactive material is outside the body (or at a distance from the object).

• The object or person is exposed to radiation but does not become radioactive themselves.
• Once the source is removed or switched off, the irradiation stops.
• Example: having a medical X-ray or being near a gamma source.

Contamination

Contamination means that radioactive material has got onto or into the body (or onto an object).

• The person or object has actual radioactive atoms on them or inside them.
• The contamination continues to emit radiation until the radioactive material is removed or decays.
• This is generally more dangerous than irradiation because the radiation source is in direct contact with or inside the body.
• Example: inhaling radioactive dust, eating contaminated food, getting radioactive material on skin.

Comparing Irradiation and Contamination

Feature	Irradiation	Contamination
Source	External — away from the body	On or inside the body
Duration	Stops when source is removed	Continues until material is removed or decays
Radioactive material on body?	No	Yes
Person becomes radioactive?	No	Effectively yes (while contaminated)
Danger level	Depends on dose	Often more dangerous — continuous exposure
Example	Standing near a sealed source	Breathing in radioactive dust

Exam Tip: A very common exam question asks you to explain the difference between irradiation and contamination, and to explain why contamination is generally more hazardous. The key point is that contamination provides continuous exposure because the radioactive material stays on or in the body, whereas irradiation stops when the source is removed.

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Safety Precautions When Handling Radioactive Sources

When working with radioactive materials (e.g., in a school lab or industry), several safety precautions must be followed:

Minimising Exposure

1. Minimise time — spend as little time as possible near the source.
2. Maximise distance — stay as far away from the source as practical (radiation intensity decreases with distance).
3. Use shielding — place appropriate absorbers between you and the source (lead, concrete).

Practical Precautions

Precaution	Reason
Use tongs or long-handled forceps to handle sources	Increases distance between source and body
Point the source away from people	Reduces exposure to the directed beam
Store sources in lead-lined containers when not in use	Lead absorbs radiation, preventing exposure
Use a Geiger-Müller counter to monitor radiation levels	Ensures exposure does not exceed safe limits
Wear gloves and wash hands after handling	Prevents contamination
Never eat or drink near radioactive sources	Prevents ingestion (internal contamination)
Keep sources in their containers for the minimum time necessary	Reduces total exposure time
Wear a film badge (dosimeter)	Monitors total radiation dose received over time

Exam Tip: In the exam, you may be asked to list safety precautions for a specific scenario. Always structure your answer around the three key principles: minimise TIME, maximise DISTANCE, use SHIELDING. Then add specific practical steps relevant to the scenario.

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Background Radiation

Background radiation is the low-level ionising radiation that is present in the environment all the time. It comes from both natural and artificial (man-made) sources.

Natural Sources (~85% of total background radiation)

Source	Detail
Radon gas	The largest single source (~42% of background radiation). A radioactive gas produced by the decay of uranium in rocks and soil. Seeps up into buildings and is inhaled. Levels vary by location (higher where there is granite rock, e.g., Cornwall and Devon).
Cosmic rays	Radiation from space (the Sun and other stars). The atmosphere absorbs most of it. Exposure increases at high altitudes (e.g., during air travel).
Rocks and soil	Some rocks (especially granite) contain radioactive isotopes such as uranium and thorium.
Food and drink	Some foods contain small amounts of radioactive isotopes (e.g., potassium-40 in bananas, nuts and meat; carbon-14 in all organic matter).

Artificial Sources (~15% of total background radiation)

Source	Detail
Medical	X-rays, CT scans, radiotherapy, nuclear medicine — this is the largest artificial source.
Nuclear industry	Nuclear power stations, nuclear weapons testing (historical fallout), nuclear waste.
Consumer products	Some smoke detectors (americium-241), old luminous watch dials.

Approximate Breakdown of Background Radiation

pie title Sources of Background Radiation (UK average)
    "Radon gas" : 42
    "Cosmic rays" : 12
    "Rocks and soil" : 12
    "Food and drink" : 12
    "Medical" : 20
    "Nuclear industry and other" : 2

Key Points About Background Radiation

• Background radiation is always present — it cannot be eliminated.
• When measuring the activity of a radioactive source, you must subtract the background count to get the true activity of the source.
• Background radiation levels vary depending on location (e.g., granite areas have more radon) and altitude (higher altitudes → more cosmic radiation).

Exam Tip: When doing an experiment with a Geiger counter, always take a background count first (with no source present) and subtract it from your readings. If you are asked about this in a practical question, state that you would measure the background count rate for at least 30 seconds and then subtract this from all subsequent readings.

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Who Is Most at Risk?

People who receive higher radiation doses include: