State the effects of ionising nuclear radiations on living things, including cell death, mutations and cancer

5.2.5 Safety Precautions – Effects of Ionising Nuclear Radiations on Living Things

Key Objectives

• Understand how ionising radiation can damage living tissue.
• Identify the biological outcomes: cell death, mutations and cancer.
• Recognise the difference between deterministic and stochastic effects.
• Apply this knowledge to safety‑precaution measures.

What is Ionising Radiation?

Ionising radiation has enough energy to remove tightly bound electrons from atoms, creating ions. The main types encountered in the laboratory are:

Biological Effects of Ionising Radiation

1. Cell Death

When radiation deposits enough energy in a cell, it can cause:

• Necrosis – uncontrolled cell rupture, often due to severe damage.
• Apoptosis – programmed cell death triggered by DNA damage that the cell cannot repair.

High doses (typically > \$5\ \text{Gy}\$) produce immediate cell death in exposed tissues.

2. Mutations

Radiation can break chemical bonds in DNA, leading to:

• Base‑pair alterations (point mutations).
• Insertions or deletions of DNA segments.
• Chromosomal rearrangements.

These changes may be repaired incorrectly, resulting in permanent genetic alterations that can be passed to daughter cells.

3. Cancer

Cancer arises when mutations affect genes that control cell growth (e.g., oncogenes, tumour‑suppressor genes). The risk is:

• Proportional to the dose received – a stochastic effect.
• Higher for tissues with rapidly dividing cells (bone marrow, gastrointestinal lining).
• Summarised by the linear‑no‑threshold (LNT) model: any non‑zero dose carries some risk.

Typical risk estimate: an additional \$5\%\$ chance of fatal cancer per \$1\ \text{Sv}\$ of whole‑body exposure.

Deterministic vs Stochastic Effects

1. Deterministic (tissue) effects – have a threshold dose; severity increases with dose. Examples: skin erythema, cataracts, radiation burns.
2. Stochastic (probabilistic) effects – no threshold; probability (not severity) increases with dose. Example: cancer induction.

Safety Precautions – Applying Knowledge of Biological Effects

To minimise the harmful effects of ionising radiation, the following principles are applied:

• Time: Reduce the duration of exposure.
• Distance: Increase the distance from the source (inverse square law).
• Shielding: Use appropriate materials (lead for gamma, plastic for beta, paper for alpha).
• ALARA principle: Keep exposures “As Low As Reasonably Achievable”.
• Use personal protective equipment (PPE) such as lead aprons, gloves, and eye protection.
• Monitor exposure with dosimeters and follow regulatory dose limits (e.g., \$20\ \text{mSv/year}\$ for occupational exposure).

Summary

Ionising radiation can cause immediate cell death, permanent genetic mutations, and increase the long‑term risk of cancer. Understanding these effects allows us to implement effective safety measures—limiting time, increasing distance, providing shielding, and adhering to the ALARA principle—to protect both laboratory personnel and the public.