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 level 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.
How does radon effect me?
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 lung. 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 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.
For more information about how to reduce this "silent killer" in your home, please see the article "Do I Need To Test?"