Real estate development and environmental cleanups will take longer and be more expensive under new vapor intrusion guidance expected from California environmental agencies. “Vapor intrusion” is the movement of chemical contaminants from groundwater or soil into indoor air. The radon gas found in many homes in the United States is an example of one type of vapor intrusion, but there are many other contaminants that are capable of getting into indoor air. In 2013, US EPA began to...