Long-term radon testing revealed that the radon level near our countertops is very low but the level in the basement is 3.6 picocuries per liter. Should I do anything to remediate the problem?

Radon is the second leading cause of lung cancer in this country, according to the U.S. Environmental Protection Agency, and your risk of lung cancer is especially high if you smoke and your the radon level in your home is elevated.

The EPA recommends remediating radon when the indoor-air level of radon is 4 picocuries per liter (pCi/L) or higher. The EPA also says that radon levels below that can still pose a health risk and recommends that you consider remediation when the level is above 2 and under 4 pCi/L. The average indoor radon level is about 1.3 pCi/L, and for outside air its about 0.4 pCi/L.

Radon, a radioactive gas, results from the natural decay of uranium that's present in most soils and can enter the home through cracks and holes in the foundation. The radon level of your neighbors' homes isn't an indicator of the level in your home since levels can vary widely property by property. Read our report on radon test kits, which includes buying advice and ratings of short-term and long-term kits.

You can temporarily reduce radon levels by increasing ventilation—opening windows, doors, and vents in your basement. But once they're closed, the radon level usually returns to its previous level within about 12 hours. The EPA suggests hiring a qualified radon contractor to fix the problem. We advise against taking on this work on your own since you might increase the radon level or stir up other problems.

To find a certified radon-remediation contractor, consult the EPA's list of radon contact information for each state or the National Environmental Health Association or the National Radon Safety Board. Remediation will cost $800 to $2,500, depending on the radon-reduction system used and the characteristics of your home.

For advice on selecting a contractor, use this information from the EPA. Be sure to get several bids and check references.—Kimberly Janeway | e-mail | Twitter | Forums | Facebook

Essential reading: Learn more about the issue of radon and granite countertops in our latest report on countertops and in this blog entry.