Differentiate between stochastic and deterministic radiation effects with examples.

• A. Stochastic effects have a threshold and deterministic effects have a threshold.
• B. Stochastic effects have no threshold and incidence rises with dose; deterministic effects have a threshold and severity increases with dose.
• C. Stochastic effects occur only at high doses; deterministic effects occur at any dose.
• D. Both types have a fixed threshold; severity is dose-independent.

Answer: (B)

Stochastic effects are about probability, not how bad the outcome is. With these effects, there is no definite dose at which they start; the chance of occurrence increases as the dose rises, while the severity of the event itself isn’t tied to the dose. Cancer and heritable genetic changes are classic examples. Even very small doses carry some risk, and higher doses raise the likelihood of getting cancer, for instance, even though the cancer’s severity isn’t directly set by the dose.

Deterministic effects, on the other hand, have a clear dose threshold. Below that level, the effect doesn’t occur; above it, the chance of the effect appears and the severity grows as the dose increases. Examples include skin erythema, epilation, cataracts, and acute radiation sickness—where more dose leads to more pronounced damage once the threshold is crossed.

So the key distinction is: stochastic = probability increases with dose and no threshold; deterministic = threshold exists and severity rises with dose.