Tightly sealed energy-efficient homes are good for the environment but are also proficient at trapping deadly gases such as radon indoors.

That troubling fact is of special concern to residents of Iowa, which has the highest concentration of radon in the nation,reports a local television station in Cedar Rapids. As many as 30,000 cases of lung cancer each year are caused by radon, according to the EPA, including about 400 in Iowa. Radon is a naturally occurring radioactive gas formed by the decay of uranium.

Currently, the U.S. Environmental Protection Agency does not recommend air filtration to reduce the health risks associated with radon. Instead, the agency recommends source-control technologies to prevent radon from entering the household in the first place. The best approach, says the EPA, is “soil depressurization,” which draws air out from under the slab of a house and vents it outside. This is work best left to professionals, nearly all agree.

That doesn’t mean air filtration shouldn’t be a part of your home radon-management strategy. Activated carbon filters, such as the IQAir Granular Activated Carbon Adsorption filter, will capture radon along with Volatile Organic Compounds (VOCs).

But it is important to keep in mind that with radon in particular adsorption may be limited.

Whatisa safe level of radon in the home? None.

Says the EPA: “A safe level of radon gas is no radon gas … Any radon exposure has some risk of causing lung cancer. The lower the radon level in your home, the lower your family’s risk of lung cancer.”

There is, however, what the EPA considers an “acceptable” level of radon in the home: 4 picocuries per liter, the natural outdoor level of radon gas. The problem is that two-thirds of all homes exceed the acceptable level.

Elevated radon is especially a problem when a family spends time in the basement, because this is generally where radon enters the home through dirt floors or cracks in the walls and masonry.

Meanwhile, it can’t hurt to begin by testing the levels of radon in your home to assess your family’s risk to this odorless killer. Check out the EPA’s advicehere.