Nonstochastic effects have what characteristic?

• A. There is a threshold and severity increases with dose
• B. No threshold and probability increases with dose
• C. They occur only in radiation accidents
• D. They always occur with any exposure

Answer: (A)

Deterministic (nonstochastic) effects have a threshold dose, and once you go above that threshold, the severity of the effect increases as the dose rises. This happens because these effects come from a quantifiable level of tissue damage: below the threshold, repair processes prevent any visible harm, but once enough cells are hurt, a measurable effect appears and becomes more severe with more damage. An example in imaging is skin erythema, which only occurs after crossing a certain dose; with higher doses you can see progression to desquamation or ulceration.

This contrasts with stochastic effects, where there is no true threshold and the chance of occurrence increases with dose, not the severity. The idea that these effects always occur with any exposure or only happen during accidents doesn’t fit the deterministic behavior described above.