Which of the following is an example of a stochastic effect?

• A. Cancer
• B. Epilation
• C. Cataracts
• D. Skin erythema

Answer: (A)

Stochastic effects are random in occurrence and have no safe dose threshold; the chance of the effect happening increases with radiation dose, but the severity is not determined by the dose. Cancer fits this pattern because exposure to ionizing radiation raises the probability of developing cancer later in life, without a simple dose-based rule for how severe the outcome will be. The other effects listed are deterministic—they require crossing a dose threshold, and their severity generally rises with higher doses. Hair loss, cataracts, and skin reddening are expected to appear after certain dose levels, and greater doses tend to produce more pronounced effects. Therefore, cancer is the example of a stochastic effect.