radon

Don Graham

Iowa has the highest average for indoor radon concentration in the nation, according to the University of Iowa. 

The U.S. Environmental Protection Agency reports the radioactive gas is the second leading cause of lung cancer after smoking. Radon is colorless, odorless and tasteless, so people may breath the gas for years before it's detected.

Megan Khines / Flickr

It's colorless, odorless, and more prevalent in Iowa than any other state. Radon gas is causing 400 deaths in Iowa every year.