Looking closely into the irradiated portion, radiation may directly or indirectly damage the DNA sequences of a gene. These damaged DNA sequences are repaired by a pre-existing system in the body.
Minor damage is successfully repaired and restored. However, when many parts are damaged, they cannot be fully repaired and cells themselves die. Even when some cells die, if other cells can replace them, dysfunction does not occur in organs and tissues. However, when a large number of cells die or degenerate, there is the possibility that deterministic effects (tissue reactions) will appear, such as hair loss, cataract, skin injury or other acute disorders, as well as fetal disorders (p.90 of Vol. 1, "Lapse of Time after Exposure and Effects," and p.91 of Vol. 1, "Cell Deaths and Deterministic Effects (Tissue Reactions)").
When a cell in which DNA was not completely repaired survives, the cell gene may mutate and cause a stochastic effect such as cancer or heritable effect.
DNA is damaged not only by radiation but also by carcinogens in foods, tobacco, chemical substances in the environment and reactive oxygen, etc. It is said that DNA is damaged at 10,000 to 1,000,000 locations per cell every day. Damage due to low-dose exposures is significantly rare compared with metabolic DNA damage. However, radiation provides energy locally and causes complicated damage affecting multiple parts in DNA strands. Approx. 85% of radiation effects are caused by reactive oxygen, etc. created by radiation and approx. 15% is direct damage by radiation.
- Included in this reference material on March 31, 2013
- Updated on March 31, 2021