Vapor Intrusion Investigations and Decision-Making: A Critical Review (original) (raw)
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The Science of the total environment, 2016
USEPA recommends a multiple lines of evidence approach to make informed decisions at vapor intrusion sites because the vapor intrusion pathway is notoriously difficult to characterize. Our study uses this approach by incorporating groundwater, soil gas, indoor air field measurements and numerical models to evaluate vapor intrusion exposure risks in a Metro-Boston neighborhood known to exhibit lower than anticipated indoor air concentrations based on groundwater concentrations. We collected and evaluated five rounds of field sampling data over the period of one year. Field data results show a steep gradient in soil gas concentrations near the groundwater surface; however as the depth decreases, soil gas concentration gradients also decrease. Together, the field data and the numerical model results suggest that a subsurface feature is limiting vapor transport into indoor air spaces at the study site and that groundwater concentrations are not appropriate indicators of vapor intrusion ...
The Use of Indoor Air Measurements To Evaluate Intrusion of Subsurface VOC Vapors into Buildings
Journal of The Air & Waste Management Association, 2001
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.
Remediation Journal, 2018
Vapor intrusion (VI) assessment is complicated by spatial and temporal variability, largely due to compounded interactions among the many individual factors that influence the vapor migration pathway from subsurface sources to indoor air. Past research on highly variable indoor air datasets demonstrates that conventional sampling schemes can result in false negative determinations of potential risk corresponding to reasonable maximum exposures (RME). While high‐frequency chemical analysis of individual chlorinated volatile organic compounds (CVOCs) in indoor air is conceptually appealing, it remains largely impractical when numerous buildings are involved and particularly for long‐term monitoring. As more is learned about the challenges with indoor air sampling for VI assessment, it has become clear that alternative approaches are needed to help guide discrete sampling efforts and reduce sampling requirements while maintaining acceptable confidence in exposure characterization. Indi...
Exposure assessment modeling for volatilestowards an Australian indoor vapor intrusion model
Journal of Toxicology and …, 2007
Human health risk assessment of sites contaminated by volatile hydrocarbons involves site-specific evaluations of soil or groundwater contaminants and development of Australian soil healthbased investigation levels (HILs). Exposure assessment of vapors arising from subsurface sources includes the use of overseasderived commercial models to predict indoor air concentrations. These indoor vapor intrusion models commonly consider steadystate assumptions, infinite sources, limited soil biodegradation, negligible free phase, and equilibrium partitioning into air and water phases to represent advective and diffusive processes. Regional model construct influences and input parameters affect model predictions while steady-state assumptions introduce conservatism and jointly highlight the need for Australian-specific indoor vapor intrusion assessment. An Australian non-steadystate indoor vapor intrusion model has been developed to determine cumulative indoor human doses (CIHDs) and to address these concerns by incorporating Australian experimental field data to consider mixing, dilution, ventilation, sink effects and first-order soil and air degradation. It was used to develop provisional HILs for benzene, toluene, ethylbenzene, and xylene (BTEX), naphthalene, and volatile aliphatic and aromatic total petroleum hydrocarbons (TPH) £ EC16 fractions for crawl space dwellings. This article summarizes current state of knowledge and discusses proposed research for differing exposure scenarios based on Australian dwelling and subsurface influences, concurrent with sensitivity analyses of input parameters and in-field model validation.
2014
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2013
Simona Berardi, Elisabetta Bemporad, Eleonora Beccaloni, Federica Scaini, Maria Gregio, Gianni Formenton Italian Workers' Compensation Authority (INAIL), Research and Technical-Scientific Sector, Department of Production Plants and Anthropic Settlements, Via Alessandria 220/E, 00198, Rome, Italy; Italian Institute of Health (ISS), Department of the Environment and Primary Prevention, Viale Regina Elena 299, 00161, Rome, Italy; AULSS 12 Veneziana, Department of Public Health, Environmental Hygiene Division, P.le Giustiniani 11e/2, I-30174 Venice-Mestre, Italy ; Environmental Regional Agency of Veneto (ARPAV), Laboratories Department, Padua, Italy
Remediation Journal, 2008
standard 24-hour sample collection methods may not adequately account for temporal variability and detect contamination best represented by long-term sampling periods. Henry Schuver of the U.S. Environmental Protection Agency Office of Solid Waste stated at the September 2007 Air & Waste Management Association vapor-intrusion conference that the US EPA may consider recommending longer-term vapor sampling to achieve more accurate time-weighted-average detections. In November 2007, indoor air at four residences was sampled to measure trichloroethene (TCE) concentrations over short-and long-duration intervals. A carefully designed investigation was conducted consisting of triplicate samplers for three different investigatory methods: dedicated 6-liter Summa canisters (US EPA Method TO-15), pump/sorbent tubes (US EPA Method TO-17), and passive diffusion samplers (MDHS 80). The first two methods collected samples simultaneously for a 24-hour period, and the third method collected samples for two weeks.
Use of CSIA to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs
Indoor sources of volatile organic compounds (VOCs) are ubiquitous, resulting in detectable concentrations in indoor air, often at concentrations above regulatory screening levels. Because of these indoor sources, the detection of a site-related VOC in a potentially affected building at a concentration above the regulatory screening level does not necessarily indicate a vapor intrusion impact. At sites where the subsurface and indoor sources of VOCs exhibit different isotope signatures, compound-specific isotope analysis (CSIA) may be used to distinguish between vapor intrusion and indoor sources of the same VOCs. Although CSIA has been validated and accepted as an effective tool for distinguishing between different sources of VOCs in groundwater, we are not aware of prior application of CSIA to identify the source of VOCs in indoor air. In order to evaluate the utility of CSIA to distinguish between vapor intrusion and indoor sources of VOCs, we have conducted a preliminary study at Hill AFB. The results indicate that there are measurable differences in δ 13 C values between TCE in the subsurface at Hill AFB and indoor sources of TCE. The δ 13 C values for the three source area soil gas samples ranged from-25.3‰ to-24.4‰, δ 13 C values for four groundwater samples collected from the off-site plume ranged from-23.8‰ to-20.6‰, δ 13 C values for seven soil gas samples collected from above the off-site plume ranged from-23.7‰ to-5.2‰. These results show a pattern of 13 C enrichment away from the source area. In contrast, the δ 13 C values for the four indoor source samples ranged from-26.6‰ to-25.5‰, lower values than any of the subsurface samples. These preliminary results support the hypothesis that CSIA of indoor air samples can be used to distinguish between vapor intrusion and indoor sources of the same VOC.