Vapor Intrusion: Significant Changes in Environmental Regulation and Liability

Vapor intrusion (“VI”) has become an increasingly significant issue for environmental regulatory agencies, property owners, tenants, and building occupants. While the concept of “vapor intrusion” has been a health concern for decades, the science of vapor intrusion is continually evolving and regulatory bodies are constantly updating VI policies. This has resulted in substantial uncertainty in litigation matters and enforcement actions brought by regulatory agencies with widely divergent standards.

Vapor intrusion describes the process by which volatile organic compounds (“VOCs”) migrate in the gaseous form from a source of chemical contamination into the indoor air of overlying structures. The source of these VOCs is often a chemical spill which contaminates soil and groundwater. Pressure differentiation between the soil gas and indoor air causes the vapors to migrate into the structures through foundation cracks or openings. Chlorinated solvents used for dry-cleaning, degreasers used in industrial processes, and petroleum hydrocarbons from gasoline are common VOCs. Property owners or prospective buyers near former or current drycleaners and gas stations are therefore particularly vulnerable to vapor intrusion. Building occupant exposure to VOC vapors is a potential serious health concern.

Regulatory Landscape

Recent recognition that VI must be addressed during site remediation has prompted the U.S. Environmental Protection Agency (“EPA”), as well as a majority of states, to adopt guidance or regulation necessitating VI assessment and health-protective mitigation. Several approaches to VI have been taken at the federal and state level, demonstrating differing geographical conditions and varied histories in managing VI concerns.

Federal Level – Revised VI Guidance

In 2002, the EPA published Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils.* The EPA is expected to soon release revised guidance to reflect improved approaches for assessing vapor intrusion. Specifically, the revised guidance will call for a “multiple lines of evidence” approach, whereby soil gas, groundwater, sub slab  samples, and direct indoor air samples are collected to evaluate the potential impact of VI at a given site. This approach is intended to reduce uncertainty in the decision-making process that leads to VI remediation and enforcement.

State Level

State vapor intrusion regulation varies widely in both scope and approach. Approximately half of the states have issued comprehensive guidance or have passed enforceable vapor intrusion regulation into state law. Other states have incorporated vapor intrusion assessment into existing risk-based corrective action programs with varying degrees of complexity. Eleven states effectively defer to federal guidance, having not addressed the topic in their own environmental guidance publications. In terms of approach, a few states developed vapor intrusion regulation prior to and independent of the EPA (often with more stringent standards), whereas others largely followed the EPA’s now out-of-date 2002 draft guidance.  Consequently, property owners and prospective purchasers must consult state guidance to ensure proper vapor intrusion assessment in light of the different methods and screening levels applicable in each state.

American Society for Testing and Materials (“ASTM”) Standards

ASTM standard E1527-05  provides guidelines for completing the familiar Phase 1 environmental site assessment (“ESA”) in real estate transactions.** In the past, the environmental due diligence community believed that vapor intrusion was outside the scope of the Phase 1 ESA. In most cases, a vapor intrusion assessment was conducted only if the client explicitly requested it.

In response to this perceived vapor intrusion loophole, ASTM published standard E2600  for identifying a “vapor encroachment concern,” (“VEC”).*** E2600 provides environmental professionals with a methodology to determine the potential for hazardous vapors to migrate onto the property. It is important to note that a “vapor encroachment concern” does not constitute a recognized environmental condition (“REC”) under the ASTM Phase 1 Standard. As such, the environmental professional would be required to pursue a vapor intrusion investigation according to the E1527-05 standard to determine if a VEC is also a REC. Nonetheless, it is expected that vapor intrusion assessment will become a mandatory component of Phase 1 ESAs, rendering E2600 irrelevant.

Practical Considerations

Property owners may need to reevaluate sites that were previously deemed compliant with remediation regulations. For instance, California, New Jersey, and New York have reopened formally closed sites with No Further Action letters to investigate the potential impact of the vapor intrusion pathway.  Prospective purchasers and developers should tread cautiously in light of the rapidly evolving regulatory environment and case law. Failure to investigate the potential for vapor intrusion could result in the failure to qualify for landowner liability protections. Such protections require due care, conducting all appropriate inquiry, and preventing further disposal of hazardous materials at the acquired site.

Vapor intrusion is the latest concern of the environmental regulatory community. Evaluation methodologies and assessment standards are constantly being updated or substantially altered. Landowners and developers would be wise to consult the latest state and federal guidance documents and ensure that future assessments cover vapor intrusion. If property owners and developers take the appropriate investigatory steps, there are inexpensive and health-protective mitigation options available.


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