Vapor Intrusion Investigations and Decision-Making: A Critical Review

Abstract

At sites impacted by volatile organic compounds (VOCs), vapor intrusion (VI) is the pathway with the greatest potential to result in actual human exposure. Since sites with VI were first widely publicized in late 1990s, the scientific understanding of VI has evolved considerably. The VI conceptual model has been extended beyond relatively simple scenarios to include nuances, such as biological and hydrogeological factors that may limit the potential for VI and alternative pathways, such as preferential pathways and direct building contact/infiltration that may enhance VI in some cases. Regulatory guidance documents typically recommend initial concentration-or distance-based screening to evaluate whether VI may be a concern, followed by a multiple-lines-of-evidence (MLE) investigation approach for sites that do not screen out. These recommendations for detailed evaluation of VI currently focus on monitoring of VOC concentrations in groundwater, soil gas, and indoor air and can be supplemented by other lines of evidence. In this Critical Review, we summarize key elements important to VI site characterization, provide the status and current understanding, and highlight data interpretation challenges, as well as innovative tools developed to help overcome the challenges. Although there have been significant advances in the understanding of VI in the past 20 years, limitations and knowledge gaps in screening, investigation methods, and modeling approaches still exist. Potential areas for further research include improved initial screening methods that account for the site-specific role of barriers, improved understanding of preferential pathways, and systematic study of buildings and infrastructure other than single-family residences.

Observation of Conditions Preceding Peak Indoor Air Volatile Organic Compound Concentrations in Vapor Intrusion Studies

“…The migration of vapor‐forming chemicals from subsurface soil and groundwater to indoor air of overlying buildings can pose potential health risks to occupants. Assessment of the vapor intrusion (VI) pathway involves multiple‐lines‐of‐evidence to support decision‐making, including collection and analysis of soil, groundwater, soil gas, and indoor and outdoor air volatile organic compound (VOC) samples (ITRC, 2007; U.S. EPA 2015a; Eklund et al 2018; Levy et al 2019; Ma et al 2020). Indoor air samples are often heavily weighted compared to other lines of evidence.…”

How Does the Periodic Groundwater Table Fluctuation Impact on Chlorinated Vapor Intrusion?

“…Soil and groundwater contaminated by volatile organic compounds (VOCs) are suspected to have the carcinogenic risk and have caused a lot of public health issues [1,2]. The dynamic process of contaminants migrating through the unsaturated zone, entering into buildings located above, and threatening the health of human beings is called vapor intrusion (e.g., [3][4][5][6][7][8][9][10]). This process should not be neglected when evaluating the potential health risk and determining the solution to remediate contaminated sites.…”

Extinguishing Petroleum Vapor Intrusion and Methane Risks for Slab‐on‐ground Buildings: A Simple Guide

“…Johnson and Ettinger (1991) and a range of other efforts (Abreu and Johnson 2006;Yao et al 2012Yao et al , 2013 have parameterized VI models that are applicable to recalcitrant vapor compounds. While many have used the Johnson and Ettinger (1991) VI approach as a basis for PVI assessments, for aerobically degradable hydrocarbons where risks are more strongly mitigated, newer models and approaches have also been advanced (Lahvis and Baehr 1996;Trefry et al 2001;Davis et al 2005Davis et al , 2009aDavis et al , 2009bDavis et al , 2009cDeVaull 2007;Abreu et al 2009;Lahvis et al 2013;Verginelli et al 2016b;Lahvis 2018;Ma et al 2020).…”

“…While many have used the Johnson and Ettinger (1991) VI approach as a basis for PVI assessments, for aerobically degradable hydrocarbons where risks are more strongly mitigated, newer models and approaches have also been advanced (Lahvis and Baehr 1996; Trefry et al 2001; Davis et al 2005, 2009a, 2009b, 2009c; DeVaull 2007; Abreu et al 2009; Lahvis et al. 2013; Verginelli et al 2016b; Lahvis 2018; Ma et al 2020).…”