What is radon and why is it dangerous? Ways Radon Can Enter the Home. The image shows the inside of a home — bathroom, living room, kitchen, and basement. Red arrows show radon entry pathways. Radon sources include radon gas from soil and radon in well water. Radon can enter a home through a sump pump pit, floor-wall joints, floor cracks, and exposed soil in a crawlspace. Radon gas entering at the lowest level of the home can move to other areas. Radon from well water can enter a home through water taps, showers, dishwashers, and washers. Reducing the Risk from Radon Radon is a radioactive gas that comes naturally from soil and rocks. Radon can move from the ground into your home through cracks and holes in the foundation. It can also enter a home through private well water. Radon can build up inside your house and cause lung cancer if you breathe it in over many years. Radon is the #1 cause of lung cancer among people who don’t smoke. Lung cancer risk is much higher for peop