Given EPA’s approval of the ASTM E1527-13 standard for conducting Phase I audits, it is clear that there will be an increased focus upon assessing vapor intrusion as a pathway for contaminants. The conditions for vapor encroachment into indoor building space depends on the presence or likely presence of vapor in the subsurface level, that may result in the release of vapors from contaminated soils or groundwater through the vadose (unsaturated soils) zone and into the targeted indoor space. Generally, this assessment focuses on volatile contaminants that can migrate in a liquid phase, but can also migrate in a vapor phase into the building.

This concern over vapor intrusion as an exposure pathway was first raised by toxicologists evaluating the correlation between indoor air quality and human health. Toxicologists reviewed the effects of human exposure to low level volatile organic compounds and carcinogens such as benzene and concluded that there is a cancer risk posed to building occupants from vapor migration into the building.

The concern over vapor intrusion include an initial assessment during the Phase I audit, to evaluate the risk for vapor intrusion. The generally accepted protocol for testing is set forth in ASTM E2600-10 entitled, “Standard Guide for Vapor Encroachment Screening on Property Involved in Real Estate Transactions.” For most consultants the focus for assessing the risk posed by vapor intrusion will be on sites where volatile chemicals are present. These typically include sites where gasoline and dry cleaning have contaminated the subsurface soils and groundwater, below or near a building. Then this contamination may accumulate so that vapors can find pathways through cracks or crevices into the indoor air. This indoor air pathway can be of particular concern in many modern airtight buildings. The focus of the analysis is defining the Vapor Encroachment Condition, which is “the presence or likely presence of vapors in the subsurface of the targeted property caused by the release of vapors from contaminated soil or groundwater either on or near the targeted property”.

Lenders in real estate transactions have also raised their concern over how to quantify the risk posed by vapor intrusion and how to meet the standard recently adopted ASTM E1527-13. Because ASTM added movement of vapors in the subsurface to the definition of “migrate”, a Phase I audit will include an assessment of the migration of vapors from soil and groundwater as a part of the evaluation of whether hazardous substances have likely migrated within the property.

Consultants have been wrestling with the issue of what changes should be made in the scope of the Phase I audit to include an assessment of vapor intrusion. But, the more complex questions are developing standards for assessing vapor intrusion in the course of a Phase I audit.

By its very nature vapor migration can move in any direction and can migrate through a myriad of routes, including utility lines making sampling difficult. Further complicating the ability to characterize vapor intrusion is the fact that such vapors are affected by soil chemistry, the presence of groundwater, site specific factors, seasonal changes, barometric pressure, the operation of any heating, ventilation and cooling systems, the use of chemicals on the property, proximity to other businesses and motor vehicles. Some within the scientific field have argued that there is a great deal of uncertainty inherent in vapor intrusion studies that fail to take into consideration the complex factors that effect this exposure pathways. Results are often inconsistent and time sensitive for the consultant making any determination that chemicals present in vapor are attributable to subsurface soil or groundwater conditions is almost impossible, given the inability to eliminate all other sources

Consultants are also evaluating the unique challenges posed by this risk pathway, and there is some lack of consensus on, how to;

1. Properly communicating what the risk is to property owners;

2. Identify which properties merit a vapor intrusion investigation;

3. Determine background level for vapors;

4. Determine how much testing is sufficient to characterize conditions;

5. Prepare a model that considers alternative factors;

6. Manage the identified risk;

7. Respond to changing thresholds, screening values and guidelines;

8. Identify all sources; and

9. Eliminate factors such as HVAC systems or operational chemicals.

Just as consultants have improved their vapor sampling methodology, better methods are being developed to manage this risk. While at first glance cleaning up of contaminated soils or groundwater may be a permanent fix for vapor intrusion, there are less expensive alternatives that may be available. Some of these potential remedial measures include;

1. Increasing the HVAC’s capacity to increase air exchanges;

2. Use of passive systems to vent conditions below the building slab;

3. Active systems and fans to blow vapors away;

4. Use of impermeable layers beneath the concrete slab so as to create a barrier that prevents the vapors from entering the building.

Consultants are debating the consequences of having not tested for vapor intrusion in conjunction with past property transactions and what that might mean in demonstrating sufficient due diligence and conducting a sufficient appropriate inquiry. Environmental attorneys and property owners may also need to explore what the risk of vapor intrusion means in the context of past purchase and their redevelopment plans.

As concern over vapor intrusion continues to pick up steam, others have raised the question of what this means in the field of toxic tort litigation. Even without adequate data to demonstrate cause and effect, plaintiffs’ attorneys have eyed this pathway as an additional count in litigation. Previously cases in which plaintiffs have not demonstrated direct exposure from hazardous waste on an abutting property, may now find they can bring a viable claim for injury from exposure to vapors migrating in crevices in the ground. All of these liability scenarios can be potential nightmares for property owners unless they follow the evolving science and are prudent in addressing historical contamination and assessing indoor air. We will continue to follow these developments.