This information is reprinted from Radon Free Press, a resource for information pertaining to radon and other sources of radiation. For more information on radon, please see www.radonfreepress.com. All content is ©2000, Radon Free Press.

Radon is an odorless, tasteless, invisible cancer-causing radioactive gas that is found in nearly every part of the world. As the uranium-238 and radium-222 contained in soil, rocks, and water naturally breaks down, radon is released into the air that you breathe. Because of its abundance in the world, radon is the source for 55% of the radiation entering your body. That's more than three times all other man-made radiation (such as nuclear power plants, nuclear waste, and medical x-rays) combined.

Radon levels are measured as "picocuries per liter of air," or pCi/L. Extremely low amounts of radon naturally occur in outside air, with a level of approximately 0.4 pCi/L. Although slightly higher, levels in buildings without radon contamination are still in the safe range at approximately 1.3 pCi/L. While the U.S. Congress has set a long-term goal of reducing indoor radon levels to be no higher than outdoor levels, currently most homes can maintain levels of 2.0 pCi/L or below. Houses with radon levels above 4.0 pCi/L are considered to have dangerous levels of radon contamination.

After radon becomes airborne, it spontaneously decays and attaches to tiny dust particles floating in the air. These now radioactive particles are then easily inhaled, where they adhere to the lining of your lungs. As the radon continues to decay, it emits Alpha radiation particles, mutating the DNA of your lung cells. It is this DNA mutation that can lead to lung cancer. Studies by the Environmental Protection Agency (EPA) and the National Cancer Institute (NCI) estimate that radon contributes to 15,000 lung cancer deaths each year, making radon second only to smoking as a cause of lung cancer deaths in the United States. However, there can be a period of many years between the initial exposure to radon and the onset of disease. During this period, you are continuing to expose your lungs to the radioactive gas.

The cancer-causing effects that radon has on your lungs increases with prolonged exposure. The EPA believes that radon exposure at any level carries some risks, and a number of other activities, such as smoking, can speed up a radon-related death. Current or past smokers who are exposed to prolonged high levels of radon greatly increase their risk of developing lung cancer. However, even if you have acceptable levels of radon in your home, quitting smoking now will reduce your chances of getting lung cancer. Additionally, the more time you spend in the house, especially on the lowest three floors, the greater the effect the radon has on your lungs.

As uranium in soil, rocks and water breaks down, the invisible radon gas seeps up through the ground. When it reaches the floor of your house, it can enter through any number of paths including cracks in solid floors, cracks in walls, gaps around service pipes, and water supply lines.

Nearly 1 out of every 15 homes in the U.S. is estimated to have elevated radon levels, and elevated levels have been found in homes in every state. The level of radon gas currently present in your house and the danger that it poses to your family is based on a number of factors, some of which are: 

• The soil and rock makeup directly below your house
• The soil and rock makeup in your region of the world
• The amount of time that you spend in your house, specifically on the first three floors
• The structure and condition of your house's foundation and pipes
• The airflow through your house
• The season of the year

Since these factors are specific to your house, the radon levels in houses in your vicinity cannot be used to determine your own radon levels. The only way to accurately determine if your house contains elevated levels of radon is to conduct a test. There are two general ways recommended by the EPA: short-term testing and long-term testing. Short-term testing - This is the quickest and easiest way to determine the current level of radon gas in your home. An activated charcoal canister or a continuous monitoring machine is placed on the lowest level of your home that is currently in use as living space and is left undisturbed for 36 to 48 hours. After this period, the canister is mailed in for laboratory analysis, or the machine prints out the results. Bear in mind, radon levels tend to vary from day to day and season to season, so a short-term test does not necessarily give you an accurate reading of your home's year-round radon level. However, a high result on short-term test can reveal that a more accurate long-term test should be performed. Long-term Testing - To obtain a more accurate reading of your year-round average radon level, a series of tests done over a 90-day period should be performed.

Since the level of radon in a room can be effected easily (such as by leaving all of the windows open during the test), it is recommended that certain guidelines are followed.

After administering a short-term test for radon, results will be sent to you by your inspector. These results will tell you the average level of radon present in the room during the duration of the test. If the radon level is within the acceptable range (below 4.0 pCi/L), no additional testing is necessary.

If the results of the short-term test determines the radon levels are significantly above 4.0 pCi/L (for example 10.0 pCi/L), this indicates that the radon gas levels in your home are dangerously high and time is of the essence. You should immediately follow-up with another short-term test to confirm the first findings. If these results confirm the results of the first test, you need to contact a radon reduction contractor at once.

If the results of the short-term test determines the radon levels are marginally above 4.0 pCi/L (for example 5.0 pCi/L), a long-term test should be performed to obtain a more accurate reading of the average radon level in your home. If this long-term test also returns results above 4.0 pCi/L, you should consider contacting a radon reduction contractor.

If your test results were not above 4.0 pCi/L, your home does not currently have average radon levels that the EPA considers high-risk. However, even though your levels are not in the danger zone, if your living patterns change and you begin occupying a lower level of your home (such as the basement), you should retest on that level. Additionally, since other radon factors can change (such as a crack developing in the basement floor), it is a good idea to periodically recheck your radon levels. A possible time frame is every one to two years.

If your test results indicate a radon level of 4.0 pCi/L or higher in your home, you should consider contacting a radon reduction contractor. A radon reduction contractor is a specialist who is trained to fix radon problems in homes, schools, and office buildings.