People are constantly exposed to small amounts of ionizing radiation from the environment as they carry out their normal daily activities; this is known as background radiation. We are also exposed through some medical treatments and through activities involving radioactive material.
Radiation has always been present and is all around us. Life has evolved in a world containing significant levels of ionizing radiation. Our bodies are adapted to it. The following section outlines sources of natural background radiation. For information on dose levels from these sources, visit the Radiation Doses page and fact sheet on natural background radiation.
The earth's outer atmosphere is continually bombarded by cosmic radiation. Usually, cosmic radiation consists of fast moving particles that exist in space and originate from a variety of sources, including the sun and other celestial events in the universe.
Cosmic rays are mostly protons, but can be other particles or wave energy. Some ionizing radiation penetrates the earth's atmosphere and becomes absorbed by humans, which results in natural radiation exposure. The doses due to natural sources of radiation vary depending on location and habits. Regions at higher altitudes receive more cosmic radiation. The following map shows how levels of cosmic radiation vary with elevations above sea level and longitude and latitude in North America.
The composition of the earth's crust is a major source of natural radiation. The main contributors are natural deposits of uranium, potassium and thorium which, in the process of natural decay, release small amounts of ionizing radiation.
Traces of these minerals are also found in building materials, so exposure to natural radiation can occur indoors as well as outdoors. Most of the variation in exposure to natural radiation results from inhalation of radioactive gases that are produced by radioactive minerals found in soil and bedrock.
Radon is an odourless and colourless radioactive gas that is produced by the decay of uranium It is an inert gas, meaning that it does not react with surrounding matter. Because radon does not react, it can readily move up through the ground and into the atmosphere.. Thoron is a radioactive gas produced by thorium. Radon and thoron levels vary considerably by location depending on the composition of soil and bedrock.
Once released into the air, these gases normally dilute to harmless levels in the atmosphere, but sometimes they become trapped and accumulate inside buildings where they are inhaled by occupants. Radon gas poses a health risk not only to uranium miners but also to homeowners if it is left to accumulate in the home. On average, it is the largest source of natural radiation exposure.
More information about radon gas and the means to control it can be found on Health Canada's website. Trace amounts of radioactive minerals are naturally found in the contents of food and drinking water. For instance, vegetables are typically cultivated in soil and ground water which contains radioactive minerals.
Once ingested, these minerals result in internal exposure to natural radiation. Naturally occurring radioactive isotopes, such as potassium and carbon, have the same chemical and biological properties as their non-radioactive isotopes.
These radioactive and non-radioactive elements are used in building and maintaining our bodies. Natural radioisotopes continually expose us to radiation. Updated April 04, Save Pin More. Trace amounts of radiation stemming from the ongoing nuclear crisis in Japan have been detected across the U. Start Slideshow. Credit: Getty Images. Credit: Corbis. Dose: 1 mrem per year The average American watches about 4.
Dose: 9 mrem per year Natural gas used for cooking, heating, and other purposes may up your exposure to radiation. Dose: 11 mrem per year Cell phones, fluorescent lamps, watches, clocks, televisions, computers, and even ceramics and glass all emit some form of radiation, but at low enough rates that they have no known effect on your health.
Dose: 10 to 1, mrem per screening Many imaging techniques to diagnose medical conditions use radiation, but the dose varies widely. Replay gallery. Pinterest Facebook. Up Next Cancel. Share the Gallery Pinterest Facebook. The higher the altitude, the higher the dose. That is why those living in Denver, Colorado altitude of 5, feet receive a higher annual radiation dose from cosmic radiation than someone living at sea level altitude of 0 feet.
Learn more about cosmic radiation in RadTown, EPA's radiation education web area for students and teachers. Estimate your yearly dose from the most common sources of ionizing radiation with this interactive online dose calculator.
Uranium and thorium naturally found in the earth are called primordial primordial Existing since the formation of the solar system, naturally occurring. Radium, Cesium, and Strontium are examples of radionuclides. Trace amounts of uranium, thorium and their decay products can be found everywhere. Learn more about radioactive decay.
Terrestrial radiation levels vary by location, but areas with higher concentrations of uranium and thorium in surface soils generally have higher dose levels. Traces of radioactive materials can be found in the body, mainly naturally occurring potassium Potassium is found in the food, soil, and water we ingest. Our bodies contain small amounts of radiation because the body metabolizes the non-radioactive and radioactive forms of potassium and other elements in the same way.
A small fraction of background radiation comes from human activities. Trace amounts of radioactive elements have dispersed in the environment from nuclear weapons tests and accidents like the one at the Chernobyl nuclear power plant in Ukraine. Nuclear reactors emit small amounts of radioactive elements. Radioactive materials used in industry and even in some consumer products are also a source of small amounts of background radiation.
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