14.10: Nuclear Radiation in Our Lives
- Page ID
- 478421
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Nuclear radiation is ever present in our lives. In this section we will look at a few areas related specifically to health effects of radiation. Radiation is largely dangerous, but there are also places in medical treatment where it can be useful.
Background Radiation
We are all exposed to a small amount of radiation in our daily lives. This background radiation comes from naturally occurring sources and from human-produced radiation. Exposure to x-rays and nuclear medicine isotopes, ground sources, and cosmic radiation account for almost half of the background exposure of the average American. Radon gas, formed from the decay of uranium and thorium isotopes, is responsible for a little over half the total amount of background radiation. See the table below for background sources.
| Table \(\PageIndex{1}\): Sources of Background Radiation | |
|---|---|
| radon | \(54\%\) |
| consumer products | \(3\%\) |
| nuclear medicine | \(4\%\) |
| cosmic radiation | \(8\%\) |
| terrestrial | \(8\%\) |
| internal | \(11\%\) |
| x-rays | \(11\%\) |
| other | \(1\%\) |
The Problem of Radon
Small amounts of uranium and thorium are found in the soil of a large number of areas in the U.S. When radioactive isotopes of these elements decay, radon is one of the products formed. Radon is a colorless, odorless gas and is chemically inert, as it is one of the noble gases.
Radon is also radioactive and can easily be inhaled into the lungs. Over time, this internal radon exposure can lead to the development of lung cancer. The incidence of lung cancer in smokers exposed to radon is much higher than in non-smokers exposed to radon, since smoking has already produced some lung damage, and the radon simply makes the damage worse. Radon exposure is highest in homes lacking good air circulation to move the gas out of the residence. There are a number of inexpensive approaches to decreasing your exposure to radon. A good start is to test your living area for radon with a radon test kit.
Effects of Radiation
In order to better understand how cellular radiation damage occurs, we need to take a quick review of how the cell functions. DNA in the nucleus is responsible for protein synthesis and for regulation of many cellular functions. In the process of protein synthesis, DNA partially unfolds to produce messenger RNA (mRNA). The mRNA leaves the nucleus and interacts with ribosomes, transfer RNA, amino acids, and other cellular constituents in the cytoplasm. Through a complex series of reactions, proteins are produced to carry out a number of specialized processes within the organism. Anything that disturbs this flow of reactions can produce damage to the cell.
The major effect of ionizing radiation on the cell is the disruption of the DNA strand. With the DNA structure damaged, the cell cannot reproduce in its normal fashion. Protein synthesis is affected, as are a number of processes necessary for proper cell function. One common effect is the generation of cancer cells. These cells have an abnormal structure due to the damaged DNA. In addition, they usually grow rapidly since the normal control processes regulating cell growth have been changed by the altered composition of the DNA. Tissue damage is also common in people with severe exposure to radiation.
Effects of Radiation on Humans
We can see two general types of effects when humans are exposed to radiation. Low-level exposure can lead to development of cancer. The regulatory processes regulating cell growth are disrupted, leading to uncontrolled growth of abnormal cells. Acute exposure can produce nausea, weakness, skin burns, and internal tissue damage. Cancer patients receiving radiation therapy experience these symptoms; the radiation is targeted to a specific site in the body so that the damage is primarily to the cancer cells, and the patient is able to recover from the exposure.
Radioisotopes in Medical Diagnosis and Treatment
Radioisotopes are widely used to diagnose disease and as effective treatment tools. For diagnosis, the isotope is administered, and then located in the body using a scanner of some sort. The decay product (often gamma emission) can be located, and the intensity measured. The amount of isotope taken up by the body can then give information as to the extent of the medical problem.
An isotope of iodine (\(\ce{I}\)-131) is used in both the diagnosis and treatment of thyroid cancer. The thyroid will normally absorb iodine to produce the iodine-containing thyroid hormones. An overactive thyroid gland will absorb the radioactive material, which can then destroy excess thyroid tissue or any cancer of the thyroid. The material is sometimes used to image cancers in other parts of the body.
Technetium-99m is perhaps the most widely used radioisotope in diagnosis and treatment (the "m" stands for metastable). This isotope decays to \(\ce{Tc}\)-99 and a gamma emission of low intensity, making the radiation damage fairly negligible. The half-life is about six hours, so it will remain in the body for some time. \(\ce{Tc}\)-99m can be used to look at cardiac damage. The isotope flows in the bloodstream; if there is less blood flow in the heart, there will be less isotope concentrated in the heart muscle. Similar information can be obtained for blood flow in the brain.
Isotopes can be very useful in scans to locate cancer cells. The patient in the above image has multiple tumors that have spread (metastasized) from the main tumor. A radioisotope has been attached to antibodies that bind to specific cancer cells. The very dark spots in the armpits, neck, and groin represent areas where tumor cells exist.
Many other examples could be presented. There are presently over 25 different isotopes in use for diagnosis and treatment. A very partial list can be seen in the table below.
| Table \(\PageIndex{1}\): Radioisotopes Employed in Diagnosis and/or Treatment | ||
|---|---|---|
| Isotope | Half-Life | Application |
| \(\ce{Cr}\)-51 | 28 days | Label red blood cells. |
| \(\ce{Fe}\)-59 | 446 days | Study iron metabolism in spleen. |
| \(\ce{Xe}\)-133 | 5 days | Study lung function. |
| \(\ce{Ho}\)-166 | 26 hours | Cancer treatment. |
Section Summary
- Background radiation is defined.
- Sources of background radiation are listed.
- Anything that affects DNA replication and protein synthesis can damage a cell.
- Effects of ionizing radiation on protein synthesis are listed.
- The impact of ionizing radiation on human health is discussed.