MANKATO — When Cecil Keen moved into his Mankato home, he did a radon test in the basement.

“It was off the charts,” said Keen, a professor in the geography department at Minnesota State University.

Keen hired a contractor for $1,500 to mitigate the problem by installing a pipe and fan system to vent the deadly gas from under the basement slab out through the roof.

That experience and ongoing MSU research showing a majority of Mankato homes with high radon levels led Keen and others to successfully push for a state law that requires all new homes to be built with radon mitigation.

The new regulations go into effect June 1.

Steve Meister, a Mankato contractor and president of the Minnesota River Builders Association, said builders don’t like added regulations, but he thinks the problem with radon justifies the new law.

“The Mankato area is high in radon. It’s not that much of a cost. You basically need a pipe that runs from under the basement floor to above the eave line,” Meister said.

“It’s a safety precaution. It protects builders, too, from being sued by someone for not keeping radon out,” Meister said.

The requirement will likely add from a few hundred dollars to $1,000 to the cost of a new home depending on the size of house and type of installation.

The compromise law was not as strong as Keen had hoped because it falls just short of requiring active mitigation of using a fan installed to draw the radon out of a pipe through the roof.

What the law does require is a passive system in which pipes are installed under the basement slab and piped up to the roof, allowing natural draft to pull the gas up and away from the home.

Keen believes the passive system probably is effective about 75 percent of the time while the fan system is effective virtually all the time.

To encourage builders to install an active system, the Minnesota Department of Health is starting a Minnesota Gold Standard program in which builders will get a certificate designating their house as Gold Standard if they install an active system.

“If you’re a good builder and have a conscience and a heart, you’d put in that extra $100 for the fan,” Keen said.

The World Health Organization says 15 percent of all lung cancers are caused by radon, making it the second-highest cause of lung cancer after smoking.

It is estimated it causes the premature death of as many as 1,000 Minnesotans each year.

A natural byproduct of the radioactive decay of uranium in the ground, radon can’t be seen or smelled. A simple test kit can be purchased to test for radon.

Keen and students tied with the MSU Radon Project have been conducting radon test for years in the area. To date, 67.2 percent of the 2,000 homes tested have radon above the level recommended as safe by the EPA.

The fractured limestone along the Minnesota River Valley likely leads to more radon problems here by allowing the gas to more easily seep up.

Keen says spending a few hundred dollars to build homes radon resistant makes more sense than spending much more to mitigate it in existing homes.

“It’s the best bang for the buck. Remedying it is one of the best things people can do towards public health.”