The simple answer is exposure to radon gas, which is the 2nd leading cause of lung cancer in the United States.
The bigger question is why. There is a variety of answers to that question so we’ll provide some background.
Radon is a naturally occurring radioactive gas that can cause lung cancer according to the EPA. Radon gas is inert, colorless and odorless. Radon is naturally in the atmosphere in trace amounts. Outdoors, radon disperses rapidly and, generally, is not a health issue. Most radon exposure occurs inside homes, schools, and workplaces.
Radon is a soil gas that is formed from the Polonium and Uranium in the soil around your home that tends to seep through the imperfections in your basement retaining wall. Imper
fections may include plumbing or electrical penetrations through below-grade walls that aren’t sealed properly, cracks in slab floor or below grade walls, and possibly an unsealed sump. It is recommended to test for radon before and after the renovation project to assess whether the radon level is higher than the EPA recommends.