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Radiation hormesis is the conjecture that a low level of ionizing radiation (i.e., near the level of Earth's natural background radiation) helps "immunize" cells against DNA damage from other causes (such as free radicals or larger doses of ionizing radiation), and decreases the risk of cancer. The theory proposes that such low levels activate ...
The linear no-threshold model (LNT) is a dose-response model used in radiation protection to estimate stochastic health effects such as radiation-induced cancer, genetic mutations and teratogenic effects on the human body due to exposure to ionizing radiation. The model assumes a linear relationship between dose and health effects, even for ...
However as microgravity has been shown to modulate cancer progression, more research is needed into the combined effects of microgravity and radiation on carcinogenesis. [8] The effects of changes in oxygen levels or in immune dysfunction on cancer risks are largely unknown and are of great concern during space flight.
Radiation exposure such as ultraviolet radiation and radioactive material is a risk factor for cancer. [69] [70] [71] Many non-melanoma skin cancers are due to ultraviolet radiation, mostly from sunlight. [70] Sources of ionizing radiation include medical imaging and radon gas. [70] Ionizing radiation is not a particularly strong mutagen. [72]
The BEIR VII Report [2] contains an extensive review of data sets from human populations, including nuclear reactor workers and patients who were treated with radiation. The recent report from Cardis et al. [ 4 ] describes a meta-analysis for reactor workers from several countries.
Sources of ionizing radiation include medical imaging, and radon gas. Ionizing radiation is not a particularly strong mutagen. [74] Medical use of ionizing radiation is a growing source of radiation-induced cancers. Ionizing radiation may be used to treat other cancers, but this may, in some cases, induce a second form of cancer. [74]
When dried and frozen, Deinococcus radiodurans could survive 140,000 grays, or units of X-and gamma-ray radiation, which is 28,000 times greater than the amount of radiation that could kill a person.
A necessary step for improving space radiation cancer risk assessment is to perform studies on the molecular pathways that can cause cancer initiation and progression, and to extend these studies to learn how such pathways can be disrupted by HZE ions, including both genetic and epigenetic modifications that are noted as the hallmarks of cancer (Figure 4-8).