You can't see it, taste it or smell it. But breathing radon gas can cause lung cancer, and the city of Minneapolis wants residents to sleuth out the exact levels of this hidden risk in their homes.

The city is offering 200 free radon test kits to rally awareness about the cancer risks it poses, especially in Minnesota, where the average radon level is more than three times higher than the national average, according to the Minnesota Department of Health (MDH).

Radon gas comes from the breakdown of uranium in soil, where it can seep into homes and pose significant health risks. It is the leading cause of lung cancer in nonsmokers.

"We naturally have a lot of radon in our soil," said Dan Tranter, supervisor of the indoor air unit at MDH. "Our homes and other buildings are closed up most of the year … and that allows radon to build up."

State health officials estimate about 40 percent of Minnesota homes have dangerous radon levels, but only about 1 percent of properties are tested each year.

21,000 deaths annually

Nationally, more than 21,000 deaths each year are attributed to radon exposure.

The 200 free Minneapolis kits will be available at the City of Minneapolis Development Review, 250 S. Fourth St. Test kits also will be offered for $9 once the free kits run out.

The Minneapolis kits were purchased through a federal grant and donated by the state Health Department, which has been giving out test kits for more than a decade and expects to distribute about 11,000 to local partners this year, Tranter said.

A list of other locations offering free or discounted kits is available on the MDH website.

The radon kits are placed on the lowest "lived-in" level of a home for three to seven days and then sent to a lab for results, Tranter said.

The state Health Department recommends testing homes for radon every two to five years.

Hannah Covington • 612-673-4751