State officials say radon levels are high in four out of ten Pennsylvania homes. Officials say high levels of the gas are the number two cause of lung cancer (behind smoking) in the state. Experts with Pennsylvania’s Department of Environmental Protection say radon enters homes from the soil under them, which is a particular problem because of Pennsylvania having slightly higher amounts of uranium and thorium in the ground. Those are two precursors to radon gas. The D-E-P has radon resources, including tips for testing, on its website.