What does a nonthreshold dose-response relationship suggest?

• A. A dose must exceed a threshold before damage occurs.
• B. Only very high doses produce any damage.
• C. No dose of radiation is completely safe from causing damage.
• D. Damage is entirely unpredictable and unrelated to dose.

Answer: (C)

Nonthreshold dose-response means there is no dose small enough to be considered completely safe. Even the tiniest amount of radiation carries some chance of causing damage, though the likelihood may be very small. This reflects stochastic effects, where risk rises with dose and can occur at any exposure level, unlike deterministic effects that have a defined threshold and increase in severity with higher doses. So the idea that no dose is entirely safe from causing damage best captures this concept.