(ABC 6 News) – More than 40% of homes in Minnesota have dangerously high radon levels, according to Minnesota Department of Health officials.

According to the MDH, radon is an odorless, colorless radioactive gas and the leading cause of lung cancer in people who never smoked.

An estimated 21,000 people die of lung cancer caused by radon exposure, according to MDH.

“The only way to know if your home has high radon levels is to test, but only about 1% or 2% of Minnesota homes are tested annually,” said Dr. Brooke Cunningham, Commissioner of the MDH. “Another concern is that, although radon occurs throughout the state, there are notable disparities in where the testing and mitigation are taking place.”

According to the MDOH, Minnesota’s higher than average radon levels are credited to the state’s unique geology and cold climate. On average, Minnesota radon levels are three times higher than the U.S. average.

Radon can be produced by the decay of uranium and radium, the decayed form of uranium which turns into gas radon.

The MDH will distribute about 6,000 radon testing kits to health departments statewide for testing.

However, testing kits can also be purchased at most hardware and home improvement stores, or by directly from the state for less than $13.

According to the state, home heating system can pull more radon gas from the soil during the winter, increasing risk of exposure.