For more information on radon, click here. Medical diagnostic exams are the main manmade source of ionizing radiation exposure in the U. The goal of medical diagnostic imaging is for the benefits to far outweigh the risks. You can track the number and type of these medical diagnostic exams that you receive on a regular basis so that you can know your history and share this with your medical provider.
Consult with your health care professional on matters of how an exam will help and whether another test that does not contain ionizing radiation may provide the same benefit. Magnetic Resonance Imaging MRIs and ultrasound technology are examples of diagnostic exams that do not involve exposure to ionizing radiation. For more information on ionizing radiation and diagnostic examinations that use ionizing radiation, click here.
Image Gently external icon. NRC: Ionizing Radiation external icon. Skip directly to site content Skip directly to page options Skip directly to A-Z link. Radiation and Your Health. Section Navigation. Facebook Twitter LinkedIn Syndicate. The Electromagnetic Spectrum: Ionizing Radiation. Minus Related Pages. On This Page. What is ionizing radiation? How much ionizing radiation am I exposed to? What is the risk from exposure to ionizing radiation? More information. We are exposed to low levels of ionizing radiation every day.
Ionizing radiation can fall into two categories: natural and manmade Ionizing Radiation from Natural Sources Ionizing radiation that comes from natural sources is typically at low levels. For more information on possible health effects from radiation and radiation dose, click here These low levels of exposure vary with location, altitude and type of building materials used in home construction.
In nature, sources of ionizing radiation include: Radiation from space cosmic and solar radiation Radiation from the earth terrestrial radiation Radon Radiation from building materials Ionizing Radiation from Manmade Sources Every day, we use Ionizing radiation to help us live healthy lives. Natural Sources Natural sources of ionizing radiation usually release ionizing radiation at low levels, which also means the amounts of radiation absorbed by our bodies doses is usually small.
For more information on radon, click here Manmade Sources Medical diagnostic exams are the main manmade source of ionizing radiation exposure in the U. To receive email updates about this page, enter your email address: Email Address. What's this. Related Pages. Contact Us Calendar Employment. Links with this icon indicate that you are leaving the CDC website. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
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The rate of radioactive decay for each radioactive element is described by its half-life, or the amount of time it takes for around half of the radioactive atoms present to decay to a more stable form. Half-lives for different radioactive elements vary from fractions of seconds to billions of years. Unstable radioactive atoms can go through a series of decays, or disintegrations, before reaching a stable form. Th has a half-life of 24 days and decays by beta particle emission to protactiniumm Pam , which has a half-life of only 1.
As shown in the aturally-occurring U decay series, the final product of the decay series is lead Pb , which is stable. Of note in this series is radon Rn , a radioactive gas that poses an inhalation hazard to workers and the public see the Hazard Recognition page. Source: U. Geological Survey. Uranium decay series naturally-occurring , which produces alpha, beta, and gamma radiation not shown.
Radioactivity is the number of energized particles or photons emitted by a source of radioactive material per unit of time. Another way to describe radioactivity is the number of decays also described as disintegrations occurring per unit of time. Units of measurement for radioactivity are the Curie Ci, traditional U.
What Happens to the Radiation Emitted? Ionizing radiation particles e. As shown in the graphic and table below, while alpha and beta particles are not very penetrating through other materials, gamma and X-rays are quite penetrating, as are neutrons.
The illustration shows the penetrating power of different types of ionizing radiation, ranging from the least penetrating alpha particles to the most penetrating neutrons. When ionizing radiation interacts with humans, it is capable of damaging living cells in the human body. Humans can be exposed: 1 to external radiation from a radiation source outside of the body, such as an X-ray from an X-ray machine; or 2 through internal exposure following inhalation breathing in , ingestion swallowing , or wound uptake i.
In addition, the skin can become contaminated with radioactive materials when proper controls are not in place to prevent contamination or following an emergency. More information about the health effects of ionizing radiation is provided on the Health Effects page. Units of measurement for radiation exposure are the Roentgen R, traditional U. The Hazard Recognition page provides information about external exposure and internal exposure.
Absorbed dose is the amount of radiation energy absorbed per unit mass i. Units of measurement for absorbed dose are the rad traditional U. Equivalent dose is the amount of radiation absorbed by an individual i. Units of measurement for equivalent dose are the rem traditional U. Relevant equivalencies include:. Effective dose is the dose to the whole body that carries with it the same risk as a higher dose to a portion of the body.
The effective dose is the sum of the tissue-weighted equivalent doses. For example, suppose the lungs received an equivalent dose of 8 rem 0. Using the weighting factor of 0. Therefore, in this example, an equivalent dose of 8 rem 0. Units for effective dose are also the rem traditional U. The National Council on Radiation Protection and Measurements NCRP estimated in that the annual average radiation dose per person in the United States from natural background radiation and medical exposures is about mrem 6.
About half of the dose comes from natural sources and the other half from medical exposures. Sources of ionizing radiation for estimated annual average radiation dose per person in the U.
According to NCRP, the annual average radiation dose per person in the United States from natural background radiation and medical exposures is about mrem 6. Adapted from: Report No. Radiation dose can be grouped into two categories based on the duration length of time period of exposure to the radiation source:. All workers should know how to recognize radiation caution or warning symbols, which are posted to alert people about the health hazards of radiation sources.
The international, three-cornered symbol trefoil of radiation can be magenta, purple, or black, on a yellow background. Another international radiation warning symbol with radiating waves, a skull and crossbones, and a running person, can be used as a supplemental symbol for dangerous i.
Some higher hazard industrial radiography equipment containing shielding also features the trefoil symbol on the outside. The inside of such equipment features the supplemental dangerous radiation warning symbol to provide an additional warning about the dangers of the much greater radiation exposure possible from the unshielded radioactive material inside that equipment. This additional symbol warns workers not to disassemble the equipment or otherwise disrupt the shielding in place.
Safety and Health Topics Ionizing Radiation. Ionizing Radiation. Background What is Ionizing Radiation? What are the Sources of Ionizing Radiation? Sources of ionizing radiation include radioactive materials and radiation-generating machines. What are the Types of Ionizing Radiation?
Unstable atoms with a low neutron-to-proton ratio may emit alpha particles. Neutron particles Neutral i. Some radionuclides that emit gamma rays include: Iodine I Cesium Cs Cobalt Co , cobalt Co Gallium G Technetiumm Tcm Iridium Ir Gamma rays are often emitted along with alpha or beta particles during radioactive decay e. X-rays High-energy electromagnetic photons emitted from outside the nucleus.
Geological Survey Uranium decay series naturally-occurring , which produces alpha, beta, and gamma radiation not shown. Source: OpenClipArt The illustration shows the penetrating power of different types of ionizing radiation, ranging from the least penetrating alpha particles to the most penetrating neutrons.
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