Radon gas in the house: How to test, what to do
By Fiona Wagner • Bankrate.com

In 1984, a nuclear engineer named Stanley Watras set off the radiation alarms at his office at the Limerick Nuclear Power Plant in Pennsylvania. The source of his contamination was not his workplace, but his home, which was built on a vein of uranium. Readings revealed the level of poisonous radon gas in his home was almost 700 times that of the federal standard -- a health-risk equivalent to smoking 135 packs of cigarettes a day.

Concerns about radon-gas exposure are decades-old. The Environmental Protection Agency says about 20,000 Americans die of radon-related lung cancer annually. Exposure to the radioactive gas is the second-leading cause of lung cancer, after cigarette smoking and the No. 1 cause of lung cancer in nonsmokers. That means radon-gas exposure kills more people than secondhand smoke.

The risk depends on the concentration of radon gas in your home and the length of time you are exposed. So read on to find out how you can check for this invisible poison and what steps you can take to protect yourself.

What is radon?
Radon is an odorless, tasteless and invisible radioactive gas that is released during the natural radioactive decay of radium. While some radon is present everywhere in soil, rocks and water, particularly high levels occur in regions rich in uranium, granite, shale and phosphate.

The danger occurs when radon gas breaks down, or decays, to form radioactive particles called "progeny." When you breathe these particles into your lungs, they break down again and emit tiny bursts of energy that cause cellular damage.

Radon is measured in picoCuries per liter, or pCi/L, -- the higher the number, the more concentrated and dangerous the gas. Experts say you should fix your house if it has an average concentration of 4 pCi/L or higher.

Studies suggest that about 7 in 1,000 nonsmokers will develop lung cancer after a lifetime of exposure to radon gas at 4 pCi/L. At 2 pCi/L, that risk drops to 4 in 1,000. Smokers are at much greater risk, because radon and cigarette smoke reinforce each other -- in other words, the radon makes the smoke more dangerous, and the smoke makes the radon more dangerous. A smoker has about a 6.2 percent chance of developing lung cancer at a 4 pCi/L concentration and a 3.2 percent chance at a 2 pCi/L concentration.

The risk is much worse in the rare house with a sky-high radon level. At a lifetime exposure to 20 pCi/L of radon, a smoker has a 26 percent chance of getting lung cancer and a nonsmoker has 3.6 percent chance.

How does radon gas enter your home?
Negative indoor pressure, created when air is removed from the home through chimneys, exhaust fans and clothes dryers, can pull soil gases such as radon into your house. These gases seep in through any openings, such as cracks in your basement floor or foundation, improperly sealed floor drains or exposed crawl spaces. Radon levels are usually highest in the basement, due to its proximity to the source and poor ventilation.

All homes, new or old, are at risk for radon poisoning, as many factors determine exposure levels. The soil beneath the house, the condition of the foundation and the weather can affect the rate of radon-gas contamination. Radon levels vary throughout the year (highest levels are usually experienced during the winter) and can fluctuate wildly within a day: the longer the test period, the more accurate the exposure results.