How does ionizing radiation affect our body?
The radiation affects human body in highly complicated processes. Various degrees of biological effects, from damage to death of living tissues, involve a number of pathological changes in human cells.
When exposed to ionizing radiation, large molecules such as nucleic acid and proteins in the cells will be ionized or excited. This may cause changes in the molecular structures which then affect the function and metabolism of the cells. Laboratory experiments have demonstrated that ionizing radiation can cause breakage of the DNA chain or can deter cell replications. In addition, the production of harmful free radicals (e.g. OH-1, H+ etc.) by the ionization of water molecules due to radiation may lead to changes in OH molecules that are biologically important for the functioning of cells.
Although radiation can cause damage to living tissues, human cells however can repair the damage through natural metabolic processes if the absorbed dose is not high. Recovery of cells depends on the degree of initial damage and may be different for different individuals.
Understanding the effects of radiation on human bodies provide useful information for the development of radiation protection measures.
Risk factor
Risk factor is a quantitative measure of radiation hazards. It is an essential factor which should be considered in assessing the deleterious effects of radiation and setting up dose limits. The following table shows the probability of getting fatal diseases due to exposure to radiation.
This risk factor table roughly shows the relationship between radiation doses and its effects on human body. It should be note that experimental data for dose-effect relationship are still scanty, especially for low doses and low dose rates. They should be used carefully mindful of their limitations.
| Tissue or organ | Nominal Risk Coefficient (cases per 10,000 persons per Sv) 1 | Lethality fraction2 | Probability of fatal cancer (10-4 Sv-1) 3 |
|---|---|---|---|
| Oesophagus | 15 | 0.93 | 14.0 |
| Stomach | 79 | 0.83 | 65.6 |
| Colon | 65 | 0.48 | 31.2 |
| Liver | 30 | 0.95 | 28.5 |
| Lung | 114 | 0.89 | 101.5 |
| Bone | 7 | 0.45 | 3.2 |
| Skin | 1000 | 0.002 | 2.0 |
| Breast | 112 | 0.29 | 32.5 |
| Ovary | 11 | 0.57 | 6.3 |
| Bladder | 43 | 0.29 | 12.5 |
| Thyroid | 33 | 0.07 | 2.3 |
| Bone Marrow | 42 | 0.67 | 28.1 |
| Other Solid | 144 | 0.49 | 70.6 |
| Total | 1695 | - | 398.1 |
1, 2 Source : 2007 Recommendations of the International Commission on Radiological Protection (ICRP Publication No. 103)
3 Estimated by multiplying column 2 and 3