The Use of Indoor Air Measurements To Evaluate Intrusion of Subsurface VOC Vapors into Buildings

Abstract

The implementation of a risk-based corrective action approach often requires consideration of soil vapor migration into buildings and potential inhalation exposure and risk to human health. Due to the uncertainty associated with models for this pathway, there may be a desire to analyze indoor air samples to validate model predictions, and this approach is followed on a somewhat frequent basis at sites where risks are considered potentially significant. Indoor air testing can be problematic for a number of reasons. Soil vapor intrusion into buildings is complex, highly dependent on site-specific conditions, and may vary over time, complicating the interpretation of indoor air measurements when the goal is to deduce the subsurface-derived component. An extensive survey of indoor air quality data sets highlights the variability in indoor volatile organic compound (VOC) concentrations and numerous sources that can lead to elevated VOC levels. The contribution from soil vapor is likely to be small relative to VOCs from other sources for most sites. In light of these challenges, we discuss how studies that use indoor air testing to assess subsurface risks could be improved. To provide added perspective, we conclude by comparing indoor air concentrations and risks arising from subsurface VOCs, predicted using standard model equations for soil vapor fate and intrusion into buildings, to those associated with indoor sources.

Exposure Assessment Modeling for Volatiles—Towards an Australian Indoor Vapor Intrusion Model

“…Increasing attention to the development of strategies for subsurface measurement of soil gas was also undertaken to facilitate assessment of indoor air quality (Wong et al, 2003), while indoor air measurement has been highlighted as problematic due to complex site-specific behaviors exhibiting spatial and temporal variations complicating interpretation (Hers et al, 2001). Recent research also highlighted the potential for VOC migration from the indoor environment to subsurface due to changes in pressure gradients resulting in confounding of source apportionment of measured subsurface VOCs (McHugh et al, 2006).…”

“…The uncertainties associated with modeling resulted in some investigators examining indoor air quality testing (Kurtz, 2000;Hers et al, 2001); soil vapor concentration profiling using a modeling approach for sample point selection (Kilduff & Cody, 2002); or empirical assessment of soil gas vertical profiles (Roggemans et al, 2001). Increasing attention to the development of strategies for subsurface measurement of soil gas was also undertaken to facilitate assessment of indoor air quality (Wong et al, 2003), while indoor air measurement has been highlighted as problematic due to complex site-specific behaviors exhibiting spatial and temporal variations complicating interpretation (Hers et al, 2001).…”

Estimation of Generic Subslab Attenuation Factors for Vapor Intrusion Investigations

“…Lower annual‐average IAERs are possible but should be accompanied by proportionally lower vapor entry rates, offsetting the potential VIRs. Impacts to indoor air quality by indoor sources also become increasingly likely to mask and outweigh risks posed by vapor intrusion below this exchange rate (see Hers et al ; Gilbert et al ; ASHRAE ). Lower IAERs likewise indicate inadequate ventilation that should be identified and corrected as part of a vapor intrusion investigation.…”

Rush-hour aromatic and chlorinated hydrocarbons in selected subway stations of Shanghai, China

“…For example, tetrachloroethylene, a most popular dry-cleaning agent, typically had higher levels in dryingcleaning facilities (Chiappini et al, 2009), buildings where dry cleaners using TeCE were operated (McDermott et al, 2005), or residential buildings near drying-cleaning facilities (Kwon et al, 2006). CHs like TrCE and pDCB can be released to indoor air due to the use of consumer products (Shinohara et al, 2008), or vapor intrusion from groundwater through underground walls and floors (Hers et al, 2001). The occurrence of CHs in many consumer products, as well as their multiple pathways to enter indoor air, makes them an important class of air toxics detected in various indoor environments (Pellizzari et al, 1986;Hartwell et al, 1992;Kostiainen, 1995;Lee et al, 2002;Sexton et al, 2004;Sakai et al, 2004;Tang et al, 2005).…”