Recent changes in accepted toxicity profiles for TCE are significantly raising the level of concern for transactions at properties with potential vapor intrusion concerns. That was one of the key messages heard by those in attendance at this month’s conference of the Environmental Bankers Association in Long Beach, including GRS | Corteq’s Ross Simmons and Jeff Coyne. Underlying the heightened concerns is a recent decision by the USEPA to update toxicity values for TCE in the IRIS (Integrated Risk Information System) database.
For many years, assessment of risk associated with TCE vapors has been driven by a range of generally accepted cancer risks. Risk levels between 10-4 (1-in-10,000) and 10 -6 (1-in-a-million) have been generally understood as the maximum allowable health risks resulting from intrusion of volatile TCE vapors into the indoor air breathing spaces at commercial properties.
However, based on the recent revision of TCE toxicity levels in the IRIS database, acceptable regulatory thresholds in most states are now driven by non-cancer risks, which are more difficult to quantify. The inhalation toxicity value (known as Reference Concentration, or RfC) for TCE in indoor air has been reduced from 10 ug/m3 (micrograms per cubic meter) to 2 ug/m3. In addition to being adopted by many states, the lower toxicity value is also captured in the Final Vapor Intrusion Guidance published last summer by the USEPA.
The main non-cancer concern driving this reduction in allowable concentrations relates to recent data showing a higher risk to pregnant women for fetal cardiac malformation within the first 30-days of gestation. In practice, this means all women of child-bearing age may be at risk from TCE vapor exposure.
Despite the widespread regulatory buy-in for the new, lower toxicity value, there is not yet a consensus about a consistent approach to sampling methodology, frequency and duration, or appropriate response actions when elevated TCE vapor levels are found. In the absence of widespread policy agreement, most regulatory bodies are so far adopting a cautious stance, emphasizing accelerated and urgent responses. The US Dept. of Defense, for example, has begun to enforce the immediate evacuation of women from its facilities where TCE vapors are believed to be present.
TCE (Trichlorethylene) is one of the most commonly used industrial chemicals and among the most common contaminants found in subsurface soil and groundwater. In 2011 (the most recent year with available data), more than 270 million pounds of TCE was produced and sold within the United States.
While considerable uncertainty remains in understanding the appropriate methods to evaluate TCE vapor inhalation risks, and prudent response actions. Environmental Bankers Association conferees were told that the lower risk tolerances are unlikely to be reversed. 26 years of regulatory agency study and multiple periods of public comment led to adopting the new reduced toxicity values. So, it looks like TCE vapors will be an on-going concern for owners and occupants of commercial real estate and their lenders. What do you think?
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