You are here : Home > Health effects > From exposure to toxic effects


From exposure to toxic effects

Random or stochastic effects

​Random or stochastic effects do not appear after a dose threshold; the frequency of effects increase with the dose, but not the severity. 

Published on 18 March 2015

Stochastic effects appear several years after exposure by irradiation or internal contamination. The health effects are mainly cancers and hereditary effects. These effects are associated with the appearance of DNA mutations in cells, while other factors are necessary for their development. These effects are irreversible without treatment.


To date, nothing is available to clinically or biologically distinguish a radiation-induced cancer from cancer of another origin. Epidemiological studies can be used to identify an excess of cancer cases in irradiated subjects. This is a matter of comparing the frequency of cancer in an irradiated population to a non-irradiated comparable control population (with the same distribution in age and sex, and the same living conditions). These studies have made it possible to identify significant increases in the incidence of cancer in general, and certain types in particular, for certain populations exposed to artificial radioactivity. An excess of cancer has been observed in almost all organs and tissues following irradiation with a high dose and/or dose rate. There is no apparent clinical specificity for radiation-induced cancer. In case of internal contamination, the tissues and organs at risk are those where radionuclides have been deposited and retained for a long period of time.

Several examples

  • Lung cancer among uranium miners, or those exposed to radon
  • Bone cancer among workers exposed to radium by moistening with their lips the brushes used to paint watch faces
  • Cancer and leukemia among survivors of the Hiroshima and Nagasaki bombings
  • Thyroid cancer in young children exposed to iodine-131 and short-lived iodines during the Chernobyl accident

Hereditary effects
Radiation-induced hereditary effects are anomalies transmitted to the offspring of an irradiated individual. The hereditary effect corresponds to the transmission of a radiation-induced mutation to the child by one of the two parents. On the biological level, this means that the mutation has affected a male or female gamete (sperm or egg) involved in forming the fertilized egg.
While studies in animals have demonstrated the occurrence of hereditary effects in the offspring of parents exposed to ionizing radiation, no epidemiological study (such as the survivors of the Hiroshima and Nagasaki bombings) has yet revealed any heritable effects in humans.