Dealing with an indoor environmental threat

Vapor intrusion into homes and other buildings will be added to the list of criteria the Environmental Protection Agency uses to decide what areas are national priorities for environmental cleanup.

Such intrusion can bring volatile chemicals from contaminated soil, groundwater or other subsurface matter into indoor environments.

Paul Johnson, a chemical engineer and dean of the Ira A. Fulton Schools of Engineering at Arizona State University, is a pioneer in the study of vapor intrusion.

He explains why assessing the degree of risk from such vapor movement is a complex task, and why determining a reasonable level of regulation could get complicated.