How ionizing radiation enters the body depends on the source of the ionizing radiation. X-rays and gamma rays can pass directly through the body when it is exposed to an irradiating source such as an x-ray machine. Alpha and beta particles do not penetrate very far into the body but radioactive materials that emit alpha, beta or gamma radiation can be taken into the body alone or with other materials which have become contaminated in the following ways:
- In the air or mixed with the dust in the air.
- Dissolved in water.
- Mixed with soil on the ground through fertilizers and absorbed by plants that we may eat.
- By consumption of plants and animals that have become contaminated.
The main entry pathways for materials contaminated with radioactive isotopes include the nose and mouth, around the eyes and any breaks or cuts in the skin. Materials contaminated with radioactive isotopes may also become trapped under the fingernails, in hair follicles and in folds and creases in the skin. If the contaminated materials remain outside the body the health risks are fairly low. However, if the contaminated material enters the body either by ingesting or inhaling, the risks become greater depending on the quantity and type of radioactive isotope absorbed.
X-rays are used extensively for medical imaging.
Once inside the body, the radioactive isotope will ionize the cells around it sometimes causing irreparable damage.
Radioactive isotopes migrate in the body in the same way as inert isotopes of the same element. For example, iodine-131 migrates to the thyroid gland which normally uses iodine and requires a steady supply to remain healthy. This is especially true in children and young adults whose thyroid glands are more active than they are in adults. Strontium-90 mimics calcium and travels to bone tissue. In large enough doses, these isotopes will cause cancer and other diseases.
The migration of radioactive isotopes within the body is of extreme benefit to patients requiring treatment in the field of nuclear medicine and diagnostic imaging. In these instances, short lived radioactive isotopes and isotopes that can easily be flushed from the body are deliberately inhaled or ingested for medical treatments and tests.