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What is alpha radiation?
Radiation is described as a process in which energetic particles or waves travel through a medium or space. Two groups of radiation are distinguished: ionizing and non-ionizing. The difference between these two groups is that ionizing radiation has enough energy to ionize atoms, while non-ionizing radiation can only change the rotational, vibrational or electronic valence configurations of molecules and atoms.
Alpha radiation is a type of ionizing radiation. It is mostly emitted during the decay of atoms with a large nucleus. Alpha particles are formed of two protons and two neutrons (see figure 1). They are emitted to restore the ratio of neutrons to protons in the atomic nucleus. Since the particles have a relatively heavy atomic mass, they travel relatively slowly and are stopped easily by interactions with other particles or atoms.
Figure 1: Alpha decay
Some of the alpha particle emitting radioactive elements are polonium-210, radon-222, radium-226, thorium-232, uranium-238, plutonium-236 and americium-241.
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Health effects of alpha radiation
The effects of alpha radiation on humans depend on the type of exposure. Since alpha radiation is a very short-range type of radiation, it is not capable of penetrating human skin, so external exposure is not really dangerous. However, if the particles are swallowed, inhaled or absorbed through open wounds, the effects of alpha radiation on humans can indeed be quite severe.
- Cancer: the biological damage that results from swallowing, inhaling or absorbing alpha particles increases the risk of cancer. Especially lung cancer, since most alpha emitters are inhaled and thus reside in the lungs. Drinking water that contains elevated levels of radium also increases the risk of bone cancer.
- Kidney damage: when drinking water that contains high levels of uranium, the risk of developing kidney problems increases.
- DNA damage: exposure of cells to alpha radiation leads to several forms of genetic damage. For example, sister chromatid exchange (SCE) may occur. This is the exchange of genetic material between two identical sister chromatids. Elevated levels of SCE may be related to the formation of tumors. Another form of genetic damage is known as the ‘bystander effect’. This means that the cells surrounding an exposed cell also suffer from DNA damage as a consequence of extra nuclear or extracellular effects.
- Acute radiation syndrome (ARS): an acute illness caused by exposure to large doses of radiation of the entire body, or large parts of it. ARS has four stages: the prodormal stage characterized by nausea, vomiting and diarrhea occurring minutes to days after exposure; the latent stage where the patient feels and looks good, lasting up to several weeks; the manifest illness stage where the symptoms manifest, and finally recovery or death. The Russian spy Alexander Litvinenko was poisoned with polonium-210 and subsequently suffered from ARS until his death.
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Protection from alpha radiation
To protect yourself from the effects of alpha radiation on humans, three factors have to be taken in account:
- Time: reducing the time of exposure can greatly reduce the risk of health problems.
- Distance: since alpha radiation is very short-range, distancing yourself from the radiation emitter can be quite effective in reducing the risk of exposure.
- Shielding: alpha radiation does not have a high penetration capability, so devising a shield of lead, plastic or even cloth can be effective in reducing exposure.
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- Center for Disease Control and Prevention: http://www.bt.cdc.gov/radiation/arsphysicianfactsheet.asp
- Guidance for Radiation Accident Management: http://orise.orau.gov/reacts/guide/alpha.htm
- Health Physics Society: http://www.hps.org/publicinformation/ate/faqs/radiationtypes.html
- Nagasawa, H. & Little, J.B. (1992). Induction of Sister Chromatid Exchanges by Extremely Low Doses of Alpha Particles. Cancer Research 52, 6394 – 6396.
- United States Environmental Protection Agency: http://www.epa.gov/rpdweb00/understand/alpha.html
- Vermont Department of Health: http://healthvermont.gov/enviro/rad/alpha.aspx