Effects that occur by chance, mainly radiation-induced cancer and heritable effects, where a higher dose raises the likelihood but not the seriousness of the outcome. Protection systems assume no threshold and use a nominal risk coefficient of around 5 percent per sievert for fatal cancer in a whole population. Dose limits, ALARA and the effective dose quantity all exist primarily to keep stochastic risk acceptably low.
At these doses we're only talking stochastic effects, so the argument is about risk, not symptoms.
Also heard as
- stochastic effect
Do not mix it up with
- Deterministic effects: Deterministic effects have a threshold and get worse with dose; stochastic effects have no assumed threshold and only become more likely.
Related terms
Deterministic effects
Radiation injuries that appear only above a threshold dose and become more severe as dose increases.
LNT
Linear no-threshold model: the assumption that cancer risk rises in direct proportion to dose, with no safe threshold.
Effective dose
A whole-body dose figure that adds up organ doses weighted by each tissue's sensitivity to radiation risk.
ALARA
As low as reasonably achievable: the principle of keeping doses as low as practical, not just below limits.