Vapor Intrusion: Acute Exposure Regulatory Developments and Litigation Trends

• Publication year: 2017
• Author: by J. Tom Boer and Suedy Alfaro

Vapor Intrusion: Acute Exposure Regulatory Developments and Litigation Trends1

by J. Tom Boer^* and Suedy Alfaro^**

Over the last decade, regulators have accelerated their focus on vapor intrusion risk at hazardous cleanup sites. This has led to new cleanup standards, policies and guidance to evaluate potential risks, environmental investigation requirements for brownfield redevelopments, and the reopening of previously closed remedial actions. Recently, attention has turned from chronic to acute vapor intrusion risk. Although protection of human health is paramount, this recent focus has been plagued with concerns about the validity of the underlying science and a lack of comprehensive guidance from regulators on how to respond. This article explores the evolution of vapor intrusion regulation, particularly developments addressing acute risk, as well as trends in vapor intrusion-related litigation.

Vapor intrusion occurs when vapor-forming chemicals migrate from contaminated soil or groundwater into overlying occupied spaces. Chemicals may collect under structures and infiltrate into buildings. This has been found to occur through cracks in foundations and conduits such as sewers and electric lines. Once inside a building via a completed pathway, concentrations of vapor-forming chemicals may increase and cause health risks. Regulatory attention has focused predominately on volatile organic compounds ("VOCs"), particularly trichloroethylene ("TCE") and tetrachloroethylene ("PCE"), and their degradant products (e.g., vinyl chloride), as well as petroleum-related constituents like benzene. VOCs historically have been used in a variety of industrial settings, particularly as solvents and for dry cleaning. Given this widespread use, vapor-forming chemicals have been identified at cleanup sites nationwide. Some cleanup sites have been closed by regulators, in the period before attention was focused on vapor intrusion, and in some cases, properties have been transferred or redeveloped. Now, with increased attention on vapor intrusion risk, regulators must grapple with how to address the issue at both active and previously closed cleanup sites.

Regulatory focus on vapor intrusion has evolved over the last 30 years. During the 1980s, regulators were concerned with the risks of radon from natural sources. By the 1990s, attention began to turn to potential chronic exposure risk to vapor intrusion from VOCs and other industrial chemicals. By the early 2000s, regulators increasingly were incorporating vapor intrusion remedial requirements into ongoing cleanups to mitigate potential risk from chronic exposure, while also looking at closed sites to require, in some instances, further investigation and remediation to address vapor intrusion risk not previously evaluated.

The U.S. Environmental Protection Agency's ("EPA") first formal attempt to address vapor intrusion came in November 2002, when the Office of Solid Waste and Emergency Response ("OSWER") released draft guidance. That guidance, focusing almost exclusively on chronic risk, languished in draft. In 2009, however, EPA's Inspector General issued a report critical of the delay. As a result, OSWER reopened the docket for public comment and, in June 2015, issued technical guidance.²The guidance included protocols for vapor intrusion investigations, identified conditions for complete pathways, and provided criteria for response actions where vapor intrusion is determined to pose an unacceptable human-health risk, generally as a result of chronic exposure. EPA specified that the guidance was for use at sites being addressed pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA") and the Resource Conservation and Recovery Act ("RCRA") and, under certain circumstances, by state agencies.

EPA further incorporated vapor intrusion evaluations into the site-cleanup process for existing and new cleanup sites. In 2012, EPA issued guidance recommending consideration of vapor intrusion when evaluating remedy protectiveness during the Superfund five-year review process, even if it was not originally considered as part of the selected remedial action.³ This recommendation has resulted in the identification of vapor intrusion as an issue at some National Priority List sites with long-existing remedial actions, triggering requirements for further investigation and, potentially, new response actions.

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EPA also undertook a toxicological assessment of TCE. EPA's Integrated Risk Information System (IRIS) system generally recognizes that EPA will use information from an IRIS toxicology review to inform risk management decisions and develop regulations to protect public health. The 2011 Toxicological Review of Trichloroethylene in Support of the Integrated Risk Information System, CAS No. 79-01-6 (Sept. 2011) ("IRIS Review") identified a safe level of lifetime exposure (called a "reference concentration") for TCE, based on a review of studies of chronic health risks. The IRIS Review also found evidence "suggestive of the potential" for short-term exposure to TCE resulting in hazards for women in the first trimester of pregnancy due to potential teratogenic effects, i.e., potential cardiac malformation in developing fetuses. The IRIS Review's position on potential teratogenic effects associated with short-term TCE exposure, however, was based on a single 2003 study on fetal rats conducted by Paula Johnson, a doctor of veterinary medicine.⁴

The IRIS Review's finding that short-term TCE exposures might cause teratogenic risks generated concern from industry, consultants, and other stakeholders about the underlying data used to support the conclusion. For example, in 2012, two respected toxicologists sent a white paper (the "White Paper") to EPA Headquarters questioning the IRIS Review's conclusion that TCE is a teratogen.⁵ The White Paper noted that other federal agencies reviewing the same data did not reach the same conclusion. The authors reviewed all toxicology and epidemiology studies regarding cardiac defects and TCE, and found the majority of scientific studies failed to find a link. Those studies which found a link had well-documented methodological flaws or were based on designs with limited or no value in determining causation. Moreover, the White Paper pointed out that the IRIS Review relied on studies that evaluated chronic, not short-term, exposure. In addition, the White Paper's authors noted that studies indicating a potential teratogenic effect have not been replicated, even by the same researchers or at doses similar to those in the studies subject to the IRIS Review.

Much of the criticism of the IRIS Review centers on the limitations of the Johnson Study, specifically its "methodology, reported findings, and [] scientific credibility."⁶ In fact, even the IRIS Review recognized the limitations of the study: "The evidence for an association between TCE exposures in the human population and the occurrence of congenital cardiac defects is not particularly strong."⁷ The IRIS Review further notes that the animal data is "not unequivocal" and "lack[s] a clear dose-related response."⁸ Notwithstanding these statements, EPA has rejected criticism of the IRIS Review and defended its conclusions concerning potential acute exposures risks from TCE. For example, in 2015, in response to concerns expressed by the Halogenated Solvents Industry Alliance, EPA stated its position that "information quality concerns were addressed through the IRIS assessment development process . . . [and] are not new."⁹ EPA...