Learn the ins and outs of ASTM's recently released benchmark for toxic-vapor assessment
Joe Derhake, president, Partner Engineering and Science
As published in Scotsman Guide's Commercial Edition, May 2008.
The migration of toxic vapors into structures and breathing zones has long been a significant concern associated with environmentally impacted real estate. This past March, the American Society of Testing and Materials (ASTM) published a new standard dealing with vapor intrusion -- "ASTM E2600-08 Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in a Real Estate Transaction."
The standard creates a legal duty of disclosure from sellers to buyers and from landlords to tenants. Property-owners therefore must investigate and disclose vapor intrusion if it exists on their real estate. Otherwise, they risk incurring negligent or intentional nondisclosure liability.
Given that vapor testing in commercial real estate transactions is now likely to increase significantly, you should know how the ASTM standard works. That way, you can answer questions your clients may have.
Vapor intrusion's impact
Many people are still unclear about what vapor intrusion is. Essentially, it occurs when toxic chemicals migrate through the floor of a structure or through utility conduits into breathing zones of a site's occupants. Vapor migrates in many directions. In other words, while liquid-phase contaminants generally migrate down and dissolved-phase contaminants migrate with the flow of groundwater, vapor-phase contaminants migrate in all directions -- including up.
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In the past 10 years, science has advanced to show that soil-vapor concentrations are of great concern to building occupants. As a result, more than 20 states have set specific allowable levels for vapor concentrations of toxic chemicals. They set these levels by assessing the cancer risks for building tenants and other people who are regularly exposed to the property conditions.
In January 2005, for example, the California Environmental Protection Agency published its standards for human health screening levels in the state. It set acceptable levels for indoor air and soil gas for 54 different chemicals such as those found in gasoline, dry cleaner solvents and industrial solvents. The agency analyzed what levels of chemicals can cause elevated cancer risk for above-ground site-users. According to the California standard, the threshold for elevated cancer is any exposure that produces a lifetime cancer risk of one in a million.
How the standard works
ASTM's new standard will determine if a vapor-intrusion condition (VIC) exists on a property. A VIC occurs when the subsurface contaminants produce an unacceptable health risk to occupants.
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