Which statement best describes a linear, non-threshold dose-response model?

• A. There is a threshold below which no damage occurs
• B. Only high doses cause damage
• C. The dose-effect relationship is not related to dose
• D. Any nonzero dose carries some risk

Answer: (D)

In a linear, non-threshold dose-response model, the risk of harm increases in direct proportion to the amount of exposure, and there is no dose at which damage is guaranteed not to occur. This means even the smallest nonzero dose carries some risk, and that risk grows linearly as dose rises. That’s why the statement any nonzero dose carries some risk is the best fit: it captures the idea that there is no safe minimum—risk exists at all levels of exposure.

Think of it in terms of radiologic protection: even tiny amounts of ionizing radiation contribute to overall risk, which is why practices aim to minimize exposure (ALARA). The alternative ideas—having a threshold below which nothing happens, damage only at high doses, or a dose-effect unrelated to dose—don’t align with the linear non-threshold concept, which ties risk directly to the amount of dose, with no safe cutoff.