Early radiation effects are described as which of the following combinations?

• A. Deterministic and threshold
• B. Non-threshold and stochastic
• C. Deterministic and non-threshold
• D. Stochastic and threshold

Answer: (A)

Early radiation effects are deterministic with a threshold. This means you need a minimum dose before the effect appears, and once that threshold is surpassed, the severity of the effect grows with increasing dose. For example, skin erythema or hair loss typically occur only after crossing a certain dose and become more pronounced as dose rises. In contrast, stochastic effects are probabilistic and considered non-threshold—they can occur at any dose, with the chance of occurrence increasing with dose, but without a guaranteed severity tied directly to the dose. So the combination of deterministic and threshold best describes early effects.