Exposure to radon is the second-leading cause of lung cancer in the United States, after smoking, according to the National Cancer Institute. Radon is a naturally occurring radioactive gas released when uranium and thorium atoms decay. It's in the air everywhere, but usually at low enough levels that it doesn't cause any harm. When radon builds up underground or indoors, however, it becomes dangerous.
Origin
Most bedrock contains traces of uranium, thorium or both. Under most circumstances, the radon produced by the decay of these atoms simply seeps up to ground level and diffuses harmlessly into the atmosphere. However, if it enters underground structures such as mines or basements, it can build up.
Accumulation
Radon can enter a home through cracks in the foundation, floors or walls. Some can be released by building materials that use natural stone. Groundwater can also have some radon in it, which releases into the home simply by turning on the tap. If the radon can't escape--and many basements don't have operable windows and doors that would let it do so--the gas may build up to dangerous levels. Modern homes that are tightly sealed for energy-efficiency actually exacerbate the problem. Eliminating drafts also eliminates places where radon could get out.
Cancer
When you breathe radon-rich air, radon atoms lodge in your lungs. Radon itself is radioactive, meaning it is undergoing atomic decay, too. As it does, it tosses off "alpha particles"--clumps of neutrons and protons known to damage human tissues. With long-term exposure to elevated radon levels, you wind up with a lot of radioactive atoms in your lungs, pumping out alpha particles. The result is often lung cancer. The National Cancer Institute estimates that radon is responsible for 15,000 to 22,000 lung cancer deaths in the U.S. each year. Smokers are especially susceptible to radon-related lung cancer, but the risk is just as real for non-smokers.
Identification
Radon is colorless, odorless and flavorless, making it undetectable to the senses. It also produces no acute symptoms; you're not going to feel dizzy or sick from radon exposure. Essentially, there's no way to know whether your house has a radon problem unless you go looking for it. Radon test kits are available at hardware and home-improvement stores.
Remedies
The most effective way to deal with radon problems in your home is to prevent radon from getting inside in the first place. Sealing openings in the foundation is a start, but the Environmental Protection Agency recommends installing a system that inserts a suction pipe below the foundation to collect radon and vent it into the air. Other options include systems that pressurize the basement to make it difficult for radon to enter, and active ventilation systems that regularly exchange the air in the basement with air from outside.
