What is Normal Background Radiation?

Normal Background Radiation – What Causes it?

Background Radiation on Earth

Normal Background Radiation comes from one of two sources.  One type is produced naturally by decaying Atoms that are all around us in our environment.  One example is  Alpha particles  produced by the element Radium.  Radium is found  commonly in the ground and in granite rocks.   It naturally decomposes into Radon Gas, releasing   an Alpha particle.  These particles are part of normal background radiation.  Beta particles (electrons) and Gamma rays also exist in our environment and can be measured by special instruments called Geiger Counters.

Ionizing radiation is radiation that can cause other atoms to change state and can induce them to become other types of atoms. As a consequence, they  release Alpha or Beta radiation in the process.

Common Sources of Natural Background Radiation?

One of the most common sources of natural background radiation effecting  humans is Radon Gas.  This gas is formed by the decomposition of the element Radon. It is commonly found in our soil and various earth rocks like granite.  Radon gas is the source of over 50% of the human exposure to ionizing radiation on our Earth.  Other radiation sources are: X-Rays, Gamma Rays, Cosmic Rays, Beta Rays, and Alpha particles.

Normal Background Radiation Exists All Around Us


Normal background radiation types on earth  include Alpha, Beta, Gamma, X-Rays and Cosmic Rays.  All human inhabitants of our planet are exposed to  radiation throughout our lives.  A great deal of  this radiation occurs naturally, but some types are man-made:including X-Rays, used for medical purposes, and Atomic Radiation produced as the result of military weapons tests, and nuclear power plants.

Airline pilots, flight attendants, and frequent flyers are exposed to elevated levels of Cosmic Radiation during airplane flights.  Jumbo jets normally fly quite high above the earth, upwards of 40,000 feet (about 8 miles).  Cosmic radiation at these altitudes is up to fifty (50) times in contrast to the values measured at sea level.

Film Badges Measure  Normal Background Radiation

Exposure to normal background radiation can be measured over the long term by devices called film badges.  When background radiation sources penetrate the film on the badges, it exposes the film, and the degree to which the film is exposed is a measure of the incident radiation over time.  Radiation badges are typically worn by workers who are commonly exposed to ionizing radiation such as X-Ray technicians, or medical personnel working with radiation measurement instruments in laboratories.  Other workers exposed might fall into the category of defense workers or workers in nuclear power plants.

Measuring Normal Background Radiation with a Meter

Measuring Normal Background Radiation with a Meter

Film badges can be are often  used to measure radiation exposures over long periods of time, such as a week or month.  These badges, as the name implies contain a photographic film emulsion that changes form when it is exposed to radiation. They are used one-time only, and as a result  are discarded daily.

Badges must be read by special equipment after longer exposures such a a day, week or month, depending upon the situation. Film badges attach to a persons clothing (like an ID badge).

Other Types of Radiation Detection Equipment

As another precaution workers also use Geiger Detectors, which are electronic instruments measuring human doses of radiation as it happens.  These meters let you know instantly if  dangerous levels of ionizing radiation are close to you.

Many portable electronic radiation meters are available and can determine incident radiation levels by means of a detector (Geiger Meuller tube) that is sometimes provided as a “wand” device.  As this wand is brought closer and closer to the radiation source, the  meter value indicator on the  instrument increases.  As a result of this, the user  will also hear the device make more rapid  “clicks”.  Because  more clicks heard per minute, means that a  higher  the radiation dose being measured.

Normal Background Radiation Received in  One Year?

The average person receives about 300 millirems of  normal background radiation in one year.  This  radiation emanates from  Radon Gas and Cosmic Rays.  While if  you live at higher altitudes, i.e. a place like Denver Colorado, you are exposed to  about 400 millirems per year on average.

What are the Radiation Limits for Workers in Nuclear Power Plants ?

Nuclear Plant Workers Protection

Workers in nuclear and weapons manufacturing faculties are limited to annual exposure limit of 5000 millirems or 5 Rems per year. This limit is set by the U.S. Nuclear Regulatory Commission.  In contrast, this turns out to be about 10 times the rate for  non-worker exposure recommended limits!  If you are in the military services, this limit is imposed on you as well.

Common Foods That Emit Natural Background Radiation

Certain foods emit  various forms of normal background radiation.  This occurs because vegetables, fruits and grains  are grown in the soil.  Radiation occurs naturally in the soil and as a consequence the food absorbs it and takes up some  radiation.  Bananas and Kale both are slightly radioactive.  Common salt, or Sodium Chloride (NaCl)  not very radioactive, but a common salt substitute called Potassium Chloride (KCL)  is, and fixed amounts of it are used to roughly calibrate Radiation measurement devices.


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