People use and are exposed to non-ionizing radiation sources every day. This form of radiation does not carry enough energy to ionize atoms or molecules. Microwave ovens, global positioning systems, cellular telephones, television stations, FM and AM radio, baby monitors, cordless phones, garage-door openers and ham radios all use non-ionizing radiation.
These are defined as extremely low frequency ELF waves. Electrically charged molecules and atoms are called ions. The radiation that can produce ions is called ionizing radiation. 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. Such uranium-containing glass is often referred to as canary or Vaseline glass.
In part, collectors like uranium glass for the attractive glow that is produced when the glass is exposed to a black light. Even ordinary glass can contain high-enough levels of potassium or thorium to be detectable with a survey instrument. Older camera lenses ss often employed coatings of thorium to alter the index of refraction.
Commercial fertilizers are designed to provide varying levels of potassium, phosphorous, and nitrogen. Such fertilizers can be measurably radioactive for two reasons: potassium is naturally radioactive, and the phosphorous can be derived from phosphate ore that contains elevated levels of uranium. Food contains a variety of different types and amounts of naturally occurring radioactive materials. Although the relatively small quantities of food in the home contain too little radioactivity for the latter to be readily detectable, bulk shipments of food have been known to set off the alarms of radiation monitors at border crossings.
One exception would be low-sodium salt substitutes that often contain enough potassium to double the background count rate of a radiation detector. While it is less common than it once was, some brands of gas lantern mantles incorporate thorium In fact, it is the heating of the thorium by the burning gas that is responsible for the emission of light. Such mantles are sufficiently radioactive that they are often used as a check source for radiation detectors.
In the past, primarily through , a wide range of radioactive products were sold as cure-alls, for example, radium-containing pills, pads, solutions, and devices designed to add radon to drinking water.
The states generally have regulatory authority over these devices. In some cases, a state might even require that these devices be registered or licensed. Enough radiation escapes our bodies that sleeping nightly with another person adds 1 millirem to your annual dose. Lead-lined pajamas, anyone? Register or Log In. The Magazine Shop. Login Register Stay Curious Subscribe.
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