Fundamental Research Division
From exposure to toxic effects
Random or stochastic effects do not appear after a dose threshold; the frequency of effects increase with the dose, but not the severity.
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.
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