U.S. Environmental Protection Agency (EPA) released two technical guides to support assessment and mitigation activities at sites where vapor intrusion is an actual or potential concern.

The Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air applies to all sites being evaluated under federal land cleanup statutes by EPA, other federal agencies, state and tribal governments and brownfield grantees.  A companion document, the Technical Guide for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites addresses any sites where vapor intrusion related to petroleum contamination from underground storage tanks is a potential concern. Both guides are applicable to residential and non-residential settings.

“These guides will promote national consistency in assessing and addressing the vapor intrusion human exposure pathway at contaminated sites to protect human health — particularly the most vulnerable,” says Mathy Stanislaus, assistant administrator for the Office of Solid Waste and Emergency Response.  “States, tribes and localities, in particular, will find the guides to be critical resources for identifying and considering key factors related to vapor intrusion assessments, risk management decisions and mitigation actions.”

National awareness and concern about vapor intrusion has grown over the last several decades.  At the same time, knowledge of and experience with assessment and mitigation of vapor intrusion has substantially increased, leading to heightened understanding of and improved approaches for evaluating and managing vapor intrusion.  Relying upon this enhanced knowledge and more extensive experience, the guides present EPA’s current recommendations for identifying, evaluating and managing vapor intrusion while providing flexible technical approaches to accommodate site-specific conditions and circumstances.

At sites where vapor intrusion poses a potential or actual hazard to occupants’ health or safety, exposures usually can be prevented or reduced through relatively simple actions such as changing building pressure and ventilation. In most cases, costs associated with addressing vapor intrusion can be very manageable, resulting in long-term benefits including improved public health and less costly response actions. These benefits are especially likely when actions are undertaken early.

Vapor intrusion refers to the migration of hazardous vapors from contaminated subsurface sources such as groundwater through soil into overlying building and structures. Exposure to these vapors by building occupants can potentially pose both acute and chronic health risks.  Vapor intrusion is a potential concern at any building—existing or planned—located near soil or groundwater contaminated with vapor-forming toxic chemicals.