Indoor Air as a Source of VOC Contamination in Shallow Soils Below Buildings

US EPA and many state regulatory agency guidance documents recommend below-foundation vapor sampling as a key element of site investigations to determine if vapor migration from underlying soil into buildings is a completed exposure pathway (USEPA, 2002 US EPA (U.S. Environmental Protection Agency). Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance). November2002.  [Google Scholar]; WIDHFS, 2003 WIDHFS (Wisconsin Department of Health and Family Services). Chemical Vapor Intrusion and Residential Indoor Air, Guidance for Environmental Consultants and Contractors. June202004. Available at http://dhfs.wisconsin.gov/eh/Air/fs/VI_prof.htm (accessed) [Google Scholar]; San Diego County, 2004 San Diego County Department of Environmental Health. Site Assessment and Mitigation (SAM) Manual. June202004. http://www.sdcounty.ca.gov/deh/lwq/sam/vapor_risk_assessment_2000.html (accessed) [Google Scholar]; PADEP, 2004 PADEP (Pennsylvania Department of Environmental Protection). Land Recycling Program Technical Guidance Manual-Section IV.A.4. June202004. Vapor Intrusion into Buildings from Groundwater and Soil under Act 2 Statewide Health Standard. Document Number 253-0300-100. http://www.dep.state.pa.us/eps/default.asp (accessed) [Google Scholar]). If volatile organic compounds (VOCs) are detected below the building foundation, then VOC migration from the subsurface is assumed to be occurring, and further investigation is needed to determine the extent of the VOC impact. These guidance documents are predicated on the assumption that VOCs detected in below-foundation samples have originated from deeper within the subsurface. However, detection of VOCs in below-foundation vapor samples alone is not sufficient to conclude that the VOCs are migrating from the subsurface upward towards a building. VOCs detected in below-foundation vapor samples can originate from indoor sources, migrating down through the slab by diffusion or advection. Commonly referenced conceptual models for vapor intrusion address VOC migration from the subsurface into buildings but do not consider the potential for VOC migration from buildings into the subsurface (USEPA, 2002 US EPA (U.S. Environmental Protection Agency). Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance). November2002.  [Google Scholar]; Johnson and Ettinger, 1991 Johnson, P. C. and Ettinger, R. A. 1991. Heuristic model for the intrusion rate of contaminant vapors into buildings. Environ. Sci. Technol., 25(8): 1445–1452. [CSA][CROSSREF][Crossref], [Web of Science ®] [Google Scholar]; Parker, 2003 Parker, J. C. 2003. Modeling volatile chemical transport, biodecay, and emission to indoor air. Ground Water Mon. Remed., 23(1): 107–120. [CSA][Crossref], [Web of Science ®] [Google Scholar]). The advective and diffusive forces that lead to the migration of VOCs from the subsurface into buildings are equally likely to result in the migration of VOCs from buildings into the subsurface when pressure or concentration gradients support such migration. In this paper we present: i) pressure gradient measurements indicating bi-directional advective flow across building foundations, ii) simple modeling indicating that indoor sources of VOCs may cause subsurface impacts through advection across the building foundation, and iii) field data from a site where indoor sources rather than subsurface contamination were the source of VOCs detected in below-foundation vapor samples.     

Modeling Fate and Transport of Munitions Constituents on Firing Ranges

The Training Range Environmental Evaluation and Characterization System (TREECS?) computes the fate and transport of munitions constituents deposited on military firing/training ranges. TREECS^TM was developed with two levels of capability, Tiers 1 and 2, where Tier 1 is for conservative screening assessments, and Tier 2 is for more accurate predictions. The models and associated processes for Tier 2 are described. Tier 2 was applied to ranges at Fort A.P. Hill, VA, for initial demonstration purposes. Observed field data were provided after model application and are compared to model-computed results. Although the comparison was not sufficient for model validation, it does demonstrate that the model leads to the same general conclusions that the field data provided.     

Children's Indoor Leisure Activities in France: Time Budget Data for Indoor Air Risk Assessment

The objective of this study was to determine the time spent by children (0– 18 years old) in indoor places of leisure and also day-care centers. The sampling scheme was stratified by geographic region and size of town. This study was performed from September 2005 to March 2006. Families were asked to complete a diary by phone on their children's activities during the last week of school and the last week of a vacation period. The time spent in each place was then extrapolated for the winter period. We then evaluated the overall attendance and time (means and quartiles) spent by all of the children, and by those of children attending places. Information was collected on 2780 children. Gymnasiums were frequented the most (52.3% during the winter period) and were the places in which children spend the greatest amount of time (average: 19 min/day). Other places frequented the most included bars/restaurants (46.5%; average: 9 min/day), cinemas/theaters (42.2%; average: 10 min/day), and indoor pools (25.4%; average: 12 min/day). Our results should help in the prioritization of specific projects investigating exposure in children during indoor leisure activities and the evaluation of the risks associated with air pollutants in these places.     

Indoor Air Quality in Schools and Health Symptoms among Portuguese Teachers

The purpose of this study was: (i) to characterize the school indoor environment; (ii) to evaluate self-reported prevalence of disease symptoms among Portuguese teachers; and (iii) to evaluate, as far as we know for the first time in Portugal, the impact of the indoor air quality of schools on the prevalence of disease symptoms among teachers. The study was performed in the city of Oporto, starting in 2004; it included the analysis of questionnaires fulfilled by schoolteachers (n = 177), walkthrough surveys of schools grounds, buildings, and individual classrooms (n = 76), as well as indoor air monitoring. Respirable particle increase was related to chalk use and CO₂ concentrations widely exceeded reference values. Schools located near traffic lines presented higher benzene and toluene concentrations. The guideline for total viable microorganism concentration was exceeded in 35.6% of classrooms. Significant increases in disease symptoms among teachers could be related to poor indoor air quality, which was mainly due to inefficient ventilation and influence of traffic emissions. Statistically significant correlations were found between central nervous system injuries and the levels of CO₂ and total volatile organic compounds, and between upper respiratory problems and mucosal irritation and the levels of TVOC and respirable particles.     

Comparison,Validation, and Use of Models for Predicting Indoor Air Quality from Soil and Groundwater Contamination

The use of models to predict indoor air quality and health risk for the soil vapor transport to indoor air pathway is commonplace; however, there is significant uncertainty surrounding processes and factors affecting this pathway, and the accuracy of models used. Available screening models were evaluated through a review of model characteristics and sensitivity, and through comparisons to measured conditions at field sites. Model simulations and comparisons to field data indicate that the vapor attenuation ratio (α) is highly sensitive to certain processes (e.g., biodegradation and ad-vection) and input parameters. Comparisons of model predicted to measured a values indicate that models based on the Johnson and Ettinger (1991) framework in most cases result in predictions that are conservative by up to one to two orders of magnitude for field sites that were assessed, providing that appropriate input parameters are used. However, for sites where the advection potential is high, these models may not be conservative. The potential for advective transport of vapors into building may be significant for sites with shallow contamination, high permeability soil and foundation and high building underpressurization. The paper concludes with possible tiered management framework for the soil vapor pathway.     

Development of a screening relationship to describe migration of contaminant vapors into buildings

The relationship between subsurface contaminant concentrations and indoor air concentrations, arising from the migration of contaminant vapors into buildings, is affected by a number of complex processes and parameters, many of which are subject to uncertainty. A study was undertaken to develop a simplified relationship between subsurface contaminant concentrations and indoor air concentrations. This relationship is intended for use as a screening tool to determine the relative significance of vapor transport and inhalation as an exposure scenario in the establishment of soil quality guidelines. The relationship was developed using a proprietary model to analyze the infiltration of subsurface vapors into buildings. A probabilistic analysis of the relationship, using a form of Monte Carlo simulation, was undertaken to estimate the dilution of contaminant concentrations between the source (soil gas) and point of exposure (indoor air). Using standardized values for certain parameters and generic distributions for key variables, probability distributions were generated for the dilution factor as a function of contaminant depth and soil type.     

Modeling Fate of RDX at Demolition Area 2 of the Massachusetts Military Reservation

The movement of explosive RDX residue from soil to groundwater at Demolition Area 2 of the Massachusetts Military Reservation was studied with mathematical models to assess its utility and limitations and to determine requisite model improvements and data needs. The Munitions Residue Characterization and Fate model, which is based on the MEPAS source term model for soil modified for solid phase residue with dissolution, the MEPAS vadose zone model, and the MEPAS aquifer model were used in this study. All three models were applied within ARAMS? to facilitate model-to-model connectivity for computing movement of RDX from soil to vadose zone, and from vadose zone to groundwater. Model parameters and a hypothetical RDX residue loading rate were adjusted to match model results to measured RDX concentrations in surface soil and in groundwater. Through an iterative process, a loading rate of 1 kg/yr for RDX residues applied for 10 years starting in 1978 was found to fit measured conditions 20 years later. Model results were sensitive to the C4-RDX dissolution flux rate and the aqueous RDX degradation rate. Results indicate that dissolution of C4 and degradation of RDX in soil and groundwater could be quite slow, and such processes warrant further study. Mechanistic models such as those presented will be useful for estimating fate of constituent residue in soil and transport to receiving waters for evaluating range residue carrying capacity and compliance issues.     

Evaluation of the Variation in Calculated Human Exposure to Soil Contaminants Using Seven Different European Models

Calculations using seven European exposure models were performed for 20 different exposure scenarios. The objective of this article is to understand the variation in the resulting calculated human exposures due to soil contamination. To this purpose, the variation in calculated exposures has been compared with the variation in calculated concentrations in contact media and in the soil compartments and with the variation in the input parameters. This led to the conclusion that most of the variation in Exposure through soil ingestion is explained by differences in the input parameter average daily soil intake. When model-specific input parameters are used the variation in Exposure through crop consumption is explained by differences in the product of total consumption rate and fraction of total consumption rate that is home-grown. When standardized input parameters are used, this variation is comparable with the variation in Concentration in root vegetables and in Concentration in leafy vegetables. The variation in Exposure through indoor air inhalation is comparable with the variation in Concentration in indoor air. This suggests that the parameters that control the variation in Concentration in the indoor air, that is, surface and volume of the building and, to a lesser extent, ventilation frequency of the building, also control the variation in Exposure through indoor air inhalation.     

Indoor Air Inhalation Risk Assessment for Volatiles Emanating from Light Nonaqueous Phase Liquids

The indoor air inhalation pathway for volatile contaminants in soil and groundwater has received much attention recently. The risk of exposure may be higher when volatile organic compounds (VOCs) reside as constituents of a free product plume below residential or commercial structures than when dissolved in groundwater or adsorbed on soil. A methodology was developed for assessing the potential for vapor phase migration—and associated risk of indoor air inhalation—of volatile constituents from a light nonaqueous phase liquid (LNAPL) plume on top of the water table. The potential risk from inhalation of VOCs in indoor air emanating from a subsurface Jet Fuel 4 (JP-4) plume by hypothetical residential receptors was assessed at a site. Chemicals of concern (COCs) were identified and evaluated using data from the composition of JP-4 mixtures and published chemical, physical, and toxicological data. The method estimates the equilibrium vapor concentrations of JP-4 constituents using Raoult's Law for partial vapor pressure of mixtures based on assumptions about the mixture composition of JP-4. The maximum allowable vapor concentration at the source (immediately above the LNAPL) corresponding to an indoor air target concentration based on acceptable risk levels are calculated using the Johnson and Ettinger model. The model calculates the attenuation factor caused by the migration of the vapor phase VOCs through the soil column above the JP-4 plume and through subsurface foundation slabs. Finally, the maximum allowable soil gas concentrations above the LNAPL for individual constituents were calculated using this methodology and compared to the calculated equilibrium vapor concentrations of each COC to assess the likelihood of potential risk from the indoor air inhalation pathway.     

Airborne Fungal Colony-Forming Units in Outdoor and Indoor Environments in Yokohama,Japan

The fungal concentration and flora in indoor and outdoor air in Yokohama, Japan were analyzed with a Reuter centrifugal air sampler and dichloran 18% glycerol agar (DG18), and compared with the levels assessed with potato dextrose agar (PDA). The number of fungal colony-forming units (CFU) in outdoor air was < 13–2750/m³; Cladosporium spp. predominated, followed by Alternaria spp. and Penicillium spp. The fungal concentration in outdoor air peaked in September. The concentrations of fungi in outdoor air (n = 288) were significantly correlated with the maximum temperature of the day, minimum temperature of the day, average temperature of the day, average velocity of wind of the day, average temperature of the month, average relative humidity of the month and precipitation of the month. In indoor air, the fungal CFU was < 13–3750/m³. Cladosporium spp. predominated, followed by the xerophilic fungi such as the Aspergillus restrictus group, Wallemia sebi, the A. glaucus group, and Penicillium spp. The fungal concentration in indoor air peaked in October. The concentrations of fungi in indoor air (n = 288) were significantly correlated with the indoor temperature, indoor relative humidity and the outdoor climatic factors mentioned above, except for the average velocity of wind of the day. This revised version was published online in June 2006 with corrections to the Cover Date.     

Air quality monitoring with regard to222Rn in buildings constructed on disused tin-mining areas

Secondary land uses have taken place on disused tin-mining areas in the form of mixed development projects consisting of housing schemes with commercial and recreational facilities. The cassiterite minerals containing tin are rich in thorium and uranium found in the xenotime and monazite minerals commonly present in the Malaysian terrains. With the upheaval of these minerals from tin-mining activities, the environment is basically exposed to the natural radioactive materials derived from the²³²Th and²³⁸U radionuclides. One of the daughter products is²²²Rn and it is known to be one of the main indoor air pollutants related to the sick-building syndrome. High concentrations of indoor²²²Rn will be hazardous to human health, which is often associated to lung cancer and other chronic diseases. The main purpose of this study is to determine the concentrations of indoor²²²Rn in residential areas constructed on former tin-mining areas with particular reference to places with high human activities such as commercial areas. Air samples were collected using the RDX-013 scintillator cell and the quantitity of²²²Rn determined by the RDA-200 radon/thoron detector. Measurements were made at different times and intervals for the purpose of looking at variations of²²²Rn levels present in the atmosphere. Results of this study showed that the concentration of indoor²²²Rn is higher in the morning (1.64 ± 0.20 pCi L) compared to the levels detected in the afternoon (1.30 ± 0.08 pCi L) for most residential areas. As expected, the concentration of²²²Rn outdoors is lower (1.08 ± 0.08 pCi L) compared to the concentration determined indoors (1.64 ± 0.20 pCi L). Recently constructed houses or buildings in commercial centers seemed to have²²²Rn concentrations relatively higher than those occupied for longer periods of time. However, the levels of²²²Rn concentrations in the study area showed that all were below the maximum permissible level of 4.0 pCi L as stipulated by the United States Environmental Protection Agency. This work also discussed the mitigation measures taken by the building management of commercial buildings to reduce the risk of²²²Rn buildup in an effort to improve public health as a result of the poor indoor air quality.     

Modeling Escherichia coli fate and transport in the Kabul River Basin using SWAT

Access to safe water is the primary goal of all development plans, yet population increase, urbanization lead to contamination of water resources. This paper focuses on microbial contamination and aims to analyze the fate and transport of Escherichia coli in the Kabul River Basin using SWAT model to evaluate the contribution of different sources. The SWAT is calibrated and validated for the monthly time step using observed E. coli concentrations for April 2013–July 2015. The model skill score; coefficients of determination (R²) equal 0.72 and 0.70, Nash–Sutcliffe efficiencies (NSE) equal 0.69 and 0.66, and percentages bias (PBIAS) equal 3.7 and 1.9 respond well for both calibration and validation, respectively. Regional measured and modeled concentrations are very high with peaks of up to 5.2 ¹⁰log cfu/100?ml in the wet season. Overall, point sources that are comprised of human feces from the big cities and livestock manure from animal sheds, contribute most (44%) to the E. coli concentrations. During peak discharge the non-point sources become the most important contributors due to wash-off from the land and diluted point sources. Allthough such studies are lacking in developing countries, they can be helpful for sanitation management by developing and accessing regional sanitation scenarios.     

Quantifying the Influence of Stack and Wind Effects on Vapor Intrusion

This article develops mathematical relationships for quantifying how the stack effect, wind effect, and effective leakage area influence the rates of subslab soil gas entry and outdoor air infiltration into residential buildings. The equations developed in the article are based on combining existing theory for air infiltration into buildings with existing vapor intrusion modeling methods. Use of the equations for estimating the subslab soil gas attenuation factor for assessing inhalation exposure via vapor intrusion into residential buildings is illustrated with example simulations using 1 year of hourly temperature and wind speed data from a Northeastern U.S. city and with several distributions of the effective leakage area from a U.S. residential air leakage database. The simulation results make clear that the soil gas entry rate and the building's ventilation rate are positively correlated, and this correlation mutes the influence of stack and wind effects on the subslab attenuation factor. The examples also suggest that the subslab attenuation factor for most residential buildings is likely to be less than 0.003 most of the time.     

Effect of Precipitation Variability on Pollutant Concentrations in Soil: Implications for Exposure and Risk Assessments

Concentrations of toxic pollutants in surface soils must be predicted in order to assess exposures and risks that may arise from emissions at incinerators and other air pollution sources. At present, concentrations are predicted using deterministic models and time-averaged values of input parameters. This steady-state equilibrium approach does not address variability in the underlying transport and fate processes. This paper explores the variability of pollutant concentrations in surface soils that arises from precipitation, an intermittent process that governs wet deposition and leaching processes. Using long-term (45 to 50 years) historical records at 6 climato-logically diverse sites, concentrations predicted using the steady-state approach are compared to those predicted using a dynamic numerical model that simulates dry and wet deposition, leaching, and pollutant accumulation in the surface layer of soil using a daily time step. The models are compared for pollutants of low, medium, and high water solubility. Both models show that predictions depend strongly on the pollutant solubility and the precipitation pattern at the location. Average concentrations differed between locations by a factor of up to 4 due to precipitation patterns; the solubility of the pollutant had a much more pronounced effect. Both models produced similar long-term trends, for example, the duration of the period needed to achieve a quasi-steady-state pollutant concentration. However, for soluble pollutants, the dynamic model produced maximum 24-hr average concentrations that exceeded long-term averages by 4 to 8 times, and long-term predictions of the dynamic model exceeded predictions of the steady-state model by 1.9 to 3.6 times (depending on the site). These differences are caused by the steady-state assumption that deposition and leaching occur continuously. While the steady-state model can be used to estimate long-term trends of moderately to highly insoluble pollutants, the dynamic model should be used to predict short-term, maximum concentrations and both short- and long-term averages of soluble pollutants. Site-specific exposure and risk assessments should consider temporal variation and the use of a dynamic model if concentrations of soluble pollutants approach risk-based target levels.     

Fate and Transport of Naproxen in a Sandy Aquifer Material: Saturated Column Studies and Model Evaluation

Naproxen-C₁₄H₁₄O₃ is a nonsteroidal anti-inflammatory drug which has been found at detectable concentrations in wastewater, surface water, and groundwater. Naproxen is relatively hydrophilic and is in anionic form at pH between 6 and 8. In this study, column experiments were performed using an unconsolidated aquifer material from an area near Barcelona (Spain) to assess transport and reaction mechanisms of Naproxen in the aquifer matrix under different pore water fluxes. Results were evaluated using HYDRUS-1D, which was used to estimate transport parameters. Batch sorption isotherms for Naproxen conformed with the linear model with a sorption coefficient of 0.42 (cm³ g^?1), suggesting a low sorption affinity. Naproxen breakthrough curves (BTCs) measured in soil columns under steady-state, saturated water flow conditions displayed similar behavior, with no apparent hysteresis in sorption or dependence of retardation (R, 3.85-4.24) on pore water velocities. Soil sorption did not show any significant decrease for increasing flow rates, as observed from Naproxen recovery in the effluent. Sorption parameters estimated by the model suggest that Naproxen has a low sorption affinity to aquifer matrix. Most sorption of Naproxen occurred on the instantaneous sorption sites, with the kinetic sorption sites representing only about 10 to 40% of total sorption.     

Adsorption of PAHs on the Sediments from the Yellow River Delta as a Function of Particle Size and Salinity

In a seawater environment, the particle size of sediment and salinity play an important role in the adsorption behaviors of polycyclic aromatic hydrocarbons (PAHs) on sediment. In this study, batch adsorption experiments were carried out with the sediments from the Yellow River Delta (YRD) to explore the effect of particle size and salinity on the adsorption behaviors of phenanthrene (Phe), fluoranthene (Fla), and pyrene (Pyr). Adsorption isotherms of PAHs on different-sized sediments can be described by a Freundlich model with the correlation coefficients ranging from 0.96 to 0.99. The adsorption capacity of PAHs was in reverse proportion to the particle size of the sediments and in direct proportion to salinity. The sediments with smaller particle size possessed higher content of aromatic and fat components, which had strong adsorption capacity toward PAHs. Salinity influenced the adsorption behaviors of PAHs by changing the solubility of PAHs and the physicochemical properties of the sediments. The salting-out constants of Phe, Fla, and Pyr were in the range of 0.292 to 0.296, 0.230 to 0.289, and 0.293 to 0.307 l/mol, respectively. These research findings are of importance to an assessment of the fate and transport of PAHs in seawater-sediment systems.