Vapor Intrusion: Are You Ready?

Environmental Training Resource
January 14, 2013 — 1,196 views  
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Vapor intrusion (VI) is a process in which the chemicals present in the underground water or soil migrate to the air which is present above a contaminated site. At times, chemicals get spilled on the ground from an underground storage tank or from a factory leak. Some of these chemicals are capable of passing through the soil in the form of vapors. These chemical vapors pass through the sub-surface soil or preferential pathways like underground utilities, thus affecting the quality of indoor air present in the nearby buildings.

VI is not a very common phenomenon. But, the chances of its occurrence should be considered when there is a known source of groundwater or soil contamination in the nearby areas.

Chemicals Involved

Volatile organic compounds (VOCs) like diesel, gasoline, and solvents used for industrial uses and dry cleaning purposes are one group of chemicals which are easily vaporized and can pass through the soil. Household products like paints, air fresheners, moth balls, and aerosol sprays, which contain vaporizable solvents, can also be the source of VI in homes.

Health Issues

The phenomenon of VI can also lead to many health issues. Infection of the eyes and respiratory tract, nausea, and headache are some of the health problems which commonly occur. These conditions are temporary and will be resolved if the affected person is moved to fresh air. However, if exposed to vaporized solvents for a long time, one may be at a high risk of developing cancer.

EPA Guidance

In 2001, the Environmental Protection Agency (EPA) released the draft guidelines for evaluating intrusion of vapor from sources like underground water and soil to indoor pathways. This guidance contains technical and policy recommendations for evaluating sub-surface VI. A review of the draft guidelines was later released by the EPA in August 2010.

Revised EPA Guidance

The EPA is preparing its final guidance for the VI intrusion pathway, which is to be released soon. The EPA has included stakeholders and has considered extensive public comments received in 2011 and 2012, while preparing the guidance. EPA is carrying out the work on the final guidance at a fast pace, so that it can be revealed soon in the up-coming decisions.

EPA Technical Documents

The EPA has prepared several technical tools and documents to support the development of the final EPA guidance. The EPA spreadsheet for modeling subsurface VI and the VI database are two such tools which are developed. In addition to this, the research papers which are published by the Office of Research and Development will be taken into consideration, while finalizing the guidance.

Other VI Guidance

The Brownfields and Land Revitalization Technology Support Center has developed a primer titled “Vapor Intrusion Considerations for Redevelopment”. This primer is meant for stakeholders who are concerned about VI. The stakeholders include property owners, real estate developers, and municipalities. The primer gives an overview of VI and mentions how it can affect redevelopment. It also states the techniques for assessing the potential of VI in a quick and cost-effective manner. These techniques can be implemented by consulting qualified scientists and engineers.

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