Which of the following would be considered a non-stochastic effect?

Non-stochastic effects are those effects of radiation exposure that have a threshold and their severity increases with the dose. These effects are generally deterministic, meaning that above a certain dose, a particular effect will occur more frequently or with greater severity.

Cataracts are considered a non-stochastic effect because they require a certain level of radiation exposure to develop. If the radiation dose exceeds this threshold, the likelihood of developing cataracts increases. This relationship means that there is a clear correlation between the amount of radiation and the occurrence of cataracts, distinguishing them from stochastic effects, which occur randomly and do not have a threshold for incidence.

In contrast to cataracts, carcinogenesis and population genetic changes are stochastic effects, where the probability of occurrence increases with dose, but the severity is not affected by the amount of radiation exposure. Infertility can also be related to stochastic mechanisms depending on the context of exposure, but it is influenced more by the specific dose received and biological factors inherent to the individual. The deterministic nature of cataracts, clearly defined in both threshold and severity, makes them a definitive example of a non-stochastic effect.