The Voice
The United States Environmental Protection Agency (EPA) published a final rule, effective February 8, 2017, adding vapor intrusion as an exposure pathway for consideration under the Hazard Ranking System. 82 Fed. Reg. 9754 (Jan. 9, 2017). The Hazard Ranking System is the screening mechanism used by the EPA to determine whether to place sites on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List—the list of priority sites warranting further investigation and possible remediation under the Superfund program. The rule and its potential implications at current and future sites are addressed in this article.
Vapor Intrusion
Vapor intrusion occurs when vapor-forming chemicals from a subsurface source, such as soil or groundwater, migrate into an overlying building through cracks in the foundation or utility lines. Volatile chemicals are most susceptible to vapor intrusion because they evaporate easily. Common examples of vapor-forming chemicals include volatile organic compounds (i.e., trichloroethylene and benzene), semivolatile organic compounds (i.e., naphthalene), and pesticides.
The New Rule
Adding vapor intrusion to the Hazard Ranking System arose out of a May 2010 report of the Government Accountability Office (GAO) concluding that if vapor intrusion is not assessed, there is a concern that sites posing a serious human health risk will not be addressed. The GAO asked the EPA to consider adding vapor intrusion and the effect that it may have on the number of sites that it might add to the National Priorities List. On January 31, 2011, the EPA published a notice asking for public comments on the potential addition of vapor intrusion. In the rationale, the EPA noted that there are contaminated sites that did not qualify for listing on the National Priorities List under the current Hazard Ranking System, but they may be listed if the exposure threat from vapor intrusion is included in the ranking system. …