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4. |
Which organs are the most sensitive to radiation? |
The effect of equal radiation doses on different people may be different. Individual sensitivity or resistance to radiation is established as one of the main factors determining the likelihood an individual will develop an illness as a result of the exposure. This factor defines the interrelations between the strength (dose) of irradiation and the degree of healing, adaptation, and compensation reactions in an organism. These reactions occur both in the whole body and in certain tissues and cells. The nature of these reactions depends both on the individual features (age, sex, heredity, previous illnesses, medical treatment, etc.) and on the influence of external factors (social conditions, type of nutrition, industrial activity, etc.)
It is important to note that the damaging effect of radiation on the various organs and systems depends on the spectrum of radiation (i.e., on the nature of radionucleotides which have different half-lives, from several months to tens and hundreds of years). It is characterized by selective negative impact on the one or another organ. For example, radioactive iodine affects chiefly the thyroid gland, strontium affects the blood-forming system, and cesium affects the digestive system as well as the entire body.
Fig. 7: Possible routes of entry of radioactive particles and their target organs
| Isotope |
Route of Exposure |
Target Organs |
Half-life |
| Iodine - 131 |
Ingestion |
Thyroid |
8 d |
| Ruthenium - 103 |
External, inhalation |
Whole body, lungs |
39.4 d |
| Ruthenium - 106 |
Inhalation, ingestion |
Lungs, GI tract |
368 d |
| Strontium - 90 |
Ingestion |
Bone surfaces, bone marrow |
28.8 y |
| Plutonium - 239 |
Inhalation |
Lungs, bone surfaces |
24,100 y |
| Cerium -144 |
Inhalation, ingestion |
Lungs, GI tract |
284 d |
Source: Center for Disease Prevention and Epidemiology, Oregon Health Division, "Medical Aftermath of the Hanford Project," January 9, 1996, vol. 45, no. 1.
Based on studies, it was established that the long-term influence of low ionizing radiation affects primarily the thyroid gland, immune system, central nervous and cardiovascular systems, and the blood-forming organs.
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