If this system were absent, we all would die of cancer in the first few months of life, or be crippled by hereditary changes. There is epidemiological evidence that radiation hormesis decreases cancer incidence and mortality, and also hereditary effects. This evidence comes from studies of A-bomb survivors in Hiroshima and Nagasaki, of inhabitants of regions with high natural radiation, of effects of residential radon, of medical patients, of nuclear workers, and of inhabitants of region near Techa river, in Urals, contaminated by Soviet atomic weapon industry. These findings are similar to the earlier ones in the United States, where in regions with high natural radiation dose, mortality due to all malignancies was lower than in regions where radiation is lower by a factor of 2. Similar effect was found there for congenital malformations.
Similar observations comes from Germany, China, Japan and other countries.
Several studies of nuclear industry workers exposed to low radiation doses, were carried out in the United Kingdom, the United States, Canada, and Russia. Most of them show a decreased mortality for all causes, and for malignant neoplasms. I wish to mention a study from Atomic Energy Establishment of Canada. Numerous studies on patients irradiated during radiodiagnostic or radiotherapeutic operations show a decrease in lung cancer risk in those irradiated up to about 1500 mSv. Two Canadian studies of female tuberculosis patients subject to multiple x-ray diagnostics, demonstrated decreased breast cancer risk at the dose range between 10 and 1000 mSv.