New Guidance for Vapor Intrusion Investigations and Response Actions

The quality of outdoor air frequently comes to mind as an important public health concern and rightly so. What sometimes gets lost in the shuffle, though, is the role indoor air quality plays in public health. With the average American spending nearly 90 percent of his or her time indoors, the quality of air in our homes, schools, offices and other buildings is also critical to people’s health.

Vapor intrusion is a type of indoor air pollution that occurs when hazardous vapors from underground contaminated sources, like ground water, seep into buildings through openings such as cracks in basements. The vapors can build up to the point where the health or safety of residents or workers in an affected building could be at risk. Sensitive and vulnerable segments of the population, like pregnant women and the elderly, can be especially susceptible to indoor vapors. Vapor intrusion is a potential concern at any building—existing or planned—located near soil or groundwater that contains toxic chemicals that form vapors.   Early identification and remediation is critical to protect communities.

To support vapor intrusion investigations and cleanup activities across the country, we recently released two technical guides. One guide, 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 brownfields grantees. A companion document, the Technical Guide for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites addresses any site where vapor intrusion related to petroleum contamination from underground storage tanks is a potential concern. Relying on a large body of peer-reviewed science, the guides allow for flexible and effective approaches for a variety of situations. We believe that states, tribes and localities will find them helpful for 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, our knowledge of and experience with vapor intrusion has increased substantially, leading to better approaches for evaluating and managing it. The guides harness this knowledge and present our current recommendations for identifying, evaluating and mitigating vapor intrusion in both residential and non-residential settings.

While vapor intrusion can pose a serious threat to people’s health in certain circumstances if it goes unaddressed, the good news is that 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 savings down the road, especially when issues are addressed early.

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