Everyday Radiation

Naturally Occurring Radiation

Naturally occurring radiation can be found all around us.  Radiation can be found in soils, our air and water, and in us.  Because it occurs in our natural environment, we encounter it every day through the food we eat, the water we drink, and the air we breathe.  It is also in building materials and items we commonly use. 

There are three groupings of naturally occurring radiation, mostly based on where the radiation comes from.  First there is the radiation in the soils and rocks, called primordial or terrestrial.  Then there is radiation that comes from space, called cosmic or cosmogenic.  The third is human-made, something created by humans that wouldn’t exist otherwise or something that contains more radiation in it than normal (enhanced) because humans have done something to it. It has been estimated that individuals in the United States receive about 360 mrem (3.6 mSv) each year from all of these sources (Table source: NCRP 93, 1987).   


 Annual U.S. Estimated  Radiation Dose Per Person  

Source

Average annual effective dose (mrem)

Radon and other radionuclides we eat, drink, or breathe

240

Radiation from soils, rocks, building materials

30

Cosmic/cosmogenic  radiation

30

Human-made sources

60

Total

360

Most of the radiation dose we receive is from naturally occurring sources—most of this is from radon (discussed in the following part). The next largest dose is from medical radiation. The smallest dose we receive (<1 percent) is from nuclear power plant emissions and fallout from past atomic bomb detonations.

Individuals who frequently fly wonder about the extra radiation exposure they receive from flying. That depends on several things, including how long the flight lasts, how high up the plane flies and, of course, how often a person flies. Some of the approximate doses when flying at 36,000 feet are:

  • New York to Los Angeles round trip = 4 mrad (0.004 mSv)
  • New York to Paris round trip = 6 mrad (0.006 mSv)
  • New York to London round trip = 6 mrad (0.006 mSv)
  • Los Angeles to Paris round trip = 10 mrad (0.01 mSv)
  • Los Angeles to Chicago round trip = 2 mrad (0.002 mSv)

Radon

Radon is a colorless, odorless gas that can be found in the soils and rock beneath homes, in well water, and in building materials.  Radon is in the soil because the soil contains naturally occurring uranium that eventually decays to radon gas.  Radon can get into our homes from the soil through any cracks or holes in the foundation and from the water supply.  The radon concentration allowed in water supplies is highly regulated; therefore, it is the radon in air coming in to your home from the ground that can pose a danger. 

Radon can pose a danger if it concentrates to high levels once it gets in the house.  We build our newer homes to be very fuel efficient and well insulated, and because we do that, there is little outdoor air exchange unless we open doors or windows.  This gives radon the opportunity to build up if it is able to get into the house.  That is one of the factors determining radon activity in houses – can it get into the house?  Another factor is how much is coming out of the ground?  Certain types of soils – those high in limestone for example – appear to have a higher concentration of radon to release. 

Of course, radon is in the natural outdoor air as well, but it is diluted by all the air that is available.  The Environmental Protection Agency (EPA) did a national survey in the United States and determine that the average indoor air concentration (1.3 picocuries of radon per liter of air) is about three times higher than the average outdoor air concentration (0.4 picocuries per liter).  The average indoor concentration is three times less than the recommended limit (4.0 picocuries per liter).  Even though, on average, we could expect our house to have about 1.3 picocuries per liter of radon, the EPA estimates that nearly 1 out of every 15 homes in the United States has elevated radon levels.

Since radon is a gas, it is inhaled into our lungs as we breathe. Although much of the radon is then exhaled. the portion that stays in the lungs as radon (and then as the radioactive decay products that come from radon) irradiates the lungs. We are also getting radioactive materials into our lungs when we inhale radon’s radioactive decay products in the air we’re breathing. It has been estimated by the EPA that radon and its decay products may cause up to 21,000 lung cancers each year—second only to cigarette smoking.

If you have concerns and want more information or to find out how to monitor the level of radon in your home, visit the EPA Web site (www.epa.gov).

Products You Might Use or Own that Contain Radiation Sources

Some products you own and use regularly might contain or emit radiation. You are not exposed to radiation when you have these items in your homes, and they are an example of the many ways radiation benefits our modern society.

Products in your home that could include radiation, but are not hazardous to anyone’s health, include smoke detectors, food, and fertilizers.

Smoke detectors sometimes contain a small amount of a radiation source (americium-241) within a metal chamber. (The radioactivity from the source emits a constant stream of alpha particles that are sensed by a small radiation detector, causing a small current. If smoke comes between the source and the detector, the current is decreased, leaving nothing for the detector to sense, and the alarm goes off). Foods sometimes absorb naturally occurring radionuclides from surrounding soils as they grow. Fertilizers that you use for your gardens, lawns, etc., might contain potassium or uranium in small amounts.

Other items that contain radiation but are no longer manufactured—and are of interest to collectors and those who acquire antiques—are watches and clocks; glassware (canary or Vaseline glass), tile, and ceramics; gas lantern mantles; and camera lenses. Some old watches and clocks have dials that were painted with a radiation-emitting compound to make them visible in the dark. Old glassware, tile, and ceramics that contain radioactivity generally have enhanced naturally occurring radionuclides (such as uranium, thorium, or potassium) incorporated right into the glass or into the glaze. An older-style gas lantern mantle with thorium in its silk threads is often used by radiation safety offices as a source to check the operation of their radiation-detection instruments. Old camera lenses also might contain some thorium, which was believed to create a better image on the film.

It is important not to assume that all types of a certain item contain or emit radiation; for example, some smoke detectors and old watches contain radiation, but not all do. And these radiation-containing items don’t pose a radiation hazard to you unless you were to eat them—and eat a lot of them!

Radiation Devices Used for Security

There are a few common devices used for security that involve x rays and are generally regulated by federal or state agencies. (The magnetic walk-through arch where a magnetic field is used to determine if you have any metals on or in your body does NOT involve x rays.)
Cabinet x-ray systems are one of the more common devices used for security. They are found primarily at airports (the devices that carry-on bags are sent through for x-ray examination), although you might see them at the entrances to some federal and state agencies and courthouses. These units use a low-dose, continuous x-ray beam, which is also referred to as fluoroscopy. Most items receive about one-tenth of a millirem of exposure (about a tenth of a day’s worth of natural background radiation). This amount of radiation won’t harm food, vitamins, prescriptions, milk, or other items you might eat later and is usually even safe for your lower-speed camera film (<1,000). The x-ray source within the machine is completely shielded, so there is no hazard to you as you walk by the unit or to people who work by the unit 8 to 10 hours a day.

CT (computerized tomography) machines are used to scan your checked luggage at the airport and sometimes to scan cargo coming in on planes or ships. CT machines emit x rays and are as safe as the cabinet x-ray systems mentioned above. The radiation dose to your luggage is about the same, you can eat or drink anything that was in your luggage without concern, you can stand by the machine, and you can work by the machine—all with no worry.

An x-ray or electron-beam machine is used to give high doses of radiation to mail that might contain some dangerous biological substance (like anthrax). Because biological agents like anthrax are resistant to radiation and will only be killed by a high dose, the mail receives radiation doses that are a couple million times higher than we routinely receive from daily background radiation. The radiation does not harm paper mail itself (other than to possibly discolor it), and the mail does not become radioactive. If electronics or photographic film are contained within the mail, the electronic item or film may be damaged to the point where it cannot be used.

Wastes Generated from the Processing of Naturally Occurring Radioactive Materials

When we take naturally occurring radioactive materials (NORM), like those found in rock and soil, and alter the natural environment so that these materials become more accessible to human contact, the resultant radioactive materials are called TENORM—technically enhanced naturally occurring radioactive materials.

Mining is a good example of an activity resulting in exposure to TENORM. We use a variety of tools to bring rocks and soils that were previously inaccessible out of the mines, take from them the minerals we want, and treat the rest as radioactive waste. This waste is now out of the ground, is concentrated, and can come in contact with humans.  Mining is the most common source of TENORM (which most often contains radium, thorium, and uranium), but these radioactive materials are also created in mineral processing and in gas and oil production.