SEATTLE - Radon is a naturally occurring radioactive gas that comes from some dirt and rock. It's a problem across much of the country and people who breathe radon gas coming up from basements and crawlspaces for long periods have an elevated risk of lung cancer. Smoking compounds that risk say health experts.

While elevated radon risk has long been known around Spokane and Clark counties, the risk in Western Washington was considered moderate.

But now a Washington State Department of health study is now available online to tell people where in the state is there high, medium and low risk. And some of those risks are in the state's most populated counties of King, Snohomish and Pierce. The risk is highest in the Cascades, but a patchwork of small areas exist on the Eastside and the biggest zone, including much of the neighborhood west of Seward Park in Seattle.

Radon doesn't smell. You can't see it. Geologists say it comes from traces of decaying uranium in rocks and dirt.

The good news is that you can test for radon with in home kits for as little as $15 on up, to electronic radon monitors and professionals who can come into your home and also test.