After hearing about a neighbor with elevated levels of radon, Jim Senden had his North Mankato home tested and found levels in his basement were nearly five times the federal standard for health.

“You don’t watch TV in the basement in the same way” when you know there is a cancer-causing gas in there with you, Senden joked.

So he spent $1,200 and had a radon-mitigation system installed.

“Anything that is a threat to my family and myself, I wanted to address,” said Senden, who has lived in the Nicollet County house for 35 years.

And chances are, if you live in Blue Earth County, your home has elevated radon levels.

The Minnesota State University Radon Project has tested 1,700 homes in the county and found 67 percent of them have levels above the Environmental Protection Agency’s health standard.

The project’s Mike Shores said the Upper Midwest’s geology, combined with the popularity of basements here, contributes to the high radon levels.

The project offers free radon testing kits to the public and has received 200 more kits in a grant from the National Association of Counties. The kits cost about $25 if you buy them at the store.

Radon is a naturally occurring, radioactive gas that you can’t see, smell or taste. It’s the second-leading cause of lung cancer, behind smoking. The Environmental Protection Agency estimates it kills more than 20,000 people per year.

Mitigation can include a number of measures, including sealing cracks, installing a venting system, membrane sheeting in crawl spaces, house/room pressurization or an air-to-air heat exchanger.

While January is National Radon Action Month, it can be an unexciting topic, a problem that doesn’t seem to generate much action.

“That’s the toughest part about this job,” Shores said. Radon is “colorless, odorless, tasteless, easily forgotten.”

Testing for radon involves putting the kit in your home. How long depends on the test.

January is a good time to test for radon because homes tend to be sealed up then, said Cathy Sandmann, community health supervisor for the county.

Cancer risks posed by radon are cumulative, so she said it’s never too late to get tested.