What are stochastic and nonstochastic effects of radiation exposure?
There are two types of adverse effects from radiation exposure: nonstochastic (also known as deterministic) and stochastic (also known as probabilistic). Nonstochastic effects are nonprobabilistic. They have a known minimum threshold of radiation exposure. If this threshold is not exceeded, it is extremely rare for deterministic effects to occur. However, if the threshold is exceeded, the severity of the deterministic effect will depend on the dose of radiation to which the individual has been exposed. This is commonly described as a dose-related response. Examples of deterministic effects include erythema, epilation (hair loss), cataracts, and, at sufficiently high doses, death. By comparison, stochastic effects are probabilistic. The probability of the occurrence of a stochastic effect is greater at higher doses of radiation exposure, but the severity of the effect is similar whether it occurs from exposure to more or less radiation. The two categories of stochastic effects include cancer induction and genetic mutation. Stochastic effects are not presently believed to have a specific exposure threshold, although this is a subject of debate.