An Evaluation of Vapor Intrusion Into Buildings through a Study of Field Data

A systematic examination of cases on file with the Massachusetts Department of Environmental Protection was undertaken to identify a universe of sites with volatile organic compound (VOC) contamination in groundwater in close proximity to buildings. Such locations were grouped according to site variables, such as contaminants of concern and concentrations in various media; soil type; depth to groundwater; distance to building; and building construction. Indoor air, soil gas, and/or groundwater field data collected from these sites was then assembled and used to: (1) evaluate available transport models which describe the intrusion of vapors into buildings and predict indoor air contaminant concentrations resulting from the volatilization of VOC s in the subsurface; (2) examine the validity of established regulatory criteria; (3) identify specific trends and field conditions which appear to most influence vapor phase contaminant migration and intrusion processes; and (4) evaluate the possibility of vapor migration being inhibited by a "freshwater lens".     

Temporary vs. Permanent Sub-slab Ports: A Comparative Performance Study

Vapor intrusion (VI) is the migration of subsurface vapors, including radon and volatile organic compounds (VOCs), from the subsurface to indoor air. The VI exposure pathway extends from the contaminant source, which can be impacted soil or groundwater, to indoor air-exposure points. VOC contaminants of concern typically include halogenated solvents as well as petroleum hydrocarbons. Radon, a colorless radioactive gas that is released by radioactive decay of radionuclides in rock and soil, migrates into homes through VI in a similar fashion to VOCs. This project focused on the performance of permanent versus temporary sub-slab sampling ports for the determination of VI of halogenated VOCs and radon into an unoccupied house. VOC and radon concentrations measured simultaneously in soil gas using collocated temporary and permanent ports appeared to be independent of the type of port. The variability between collocated temporary and permanent ports was much less than the spatial variability between different locations within a single residential duplex. Post sampling leak test results suggested that the temporary SSP desiccation and cracking of the clay portion of the seal were not as detrimental to the port seal performance as would have been expected, this suggests that the Teflon tape portion of the seals served an important function. Pre and post sampling leak tests are advisable when temporary ports are used to collect a time-integrated sample. These results suggest that temporary sub-slab sampling ports can provide data equivalent to that collected from a permanent sub-slab sampling port.     

Chemical Vapor Intrusion from Soil or Groundwater to Indoor Air: Significance of Unsaturated Zone Biodegradation of Aromatic Hydrocarbons

The soil vapor to indoor air exposure pathway is considered in a wide number of risk-based site management programs. In screening-level assessments of this exposure pathway, models are typically used to estimate the transport of vapors from either subsurface soils or groundwater to indoor air. Published studies indicate that the simple models used to evaluate this exposure pathway often over estimate the impact for aromatic hydrocarbons (e.g., benzene, toluene, ethylbenzene, and xy-lene or BTEX), while showing reasonable agreement for estimates of chlorinated hydrocarbon impacts (e.g., PCE, TCE, DCE). Aerobic biodegradation of the petroleum hydrocarbons is most often attributed as the source of this disparity in the model/ data comparisons. This paper looks at the significance of aerobic biodegradation of aromatic hydrocarbons as part of the assessment of chemical vapor intrusion from soil or groundwater to indoor air. A review of relevant literature summarizing the available field data as well as various modeling approaches that include biodegradation is presented. This is followed by a simple modeling analysis that demonstrates the potential importance of biodegradation in the assessment of the soil vapor to indoor air exposure pathway. The paper concludes with brief discussions of other model considerations that are often not included in simple models but may have a significant impact on the intrusion of vapors into indoor air.     

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.     

A Model to Derive Soil Criteria for Benzene Migrating from Soil to Dwelling Interior in Homes with Crawl Spaces

The establishment of Australian soil criteria for volatile hydrocarbons such as benzene has been limited due to the lack of a suitable transport model to predict human exposures. In a confined environment representing worst case exposure, the inhalation of volatile hydrocarbons from sub-surface regions may be used to establish health-based soil criteria. A volatilisation model is presented for the case of a crawl space home which is a common housing design in Australia. The model is used to estimate a cumulative indoor human dose (CIHD) based on one-dimensional movement from a finite subsurface source through soil to the dwelling interior. A non-homogeneous surface boundary condition is represented where the volatile is not immediately swept away from the air/soil boundary. Time-dependent differential equations established to represent transport are solved using Laplace transforms. Australian experimental field data are used in considering mixing, dilution, ventilation and sink effects and first-order soil and air degradation of the volatile incorporated. A CIHD from the model is compared to various benzene exposure standards to determine a criterion for benzene in soil. Sensitivity analysis has revealed that the dominant influencing parameters are those relating to dwelling characteristics and not soil properties or the physico-chemical properties of the volatile. Each of the group-input parameters has been found to act virtually independently in the model presenting the potential for model refinement and establishment of a generic soil criterion for benzene.     

Microbial growth inside insulated external walls as an indoor air biocontamination source

The association between moisture-related microbial growth (mesophilic fungi and bacteria) within insulated exterior walls and microbial concentrations in the indoor air was studied. The studied apartment buildings with precast concrete external walls were situated in a subarctic zone. Actinomycetes in the insulation layer were found to have increased concentrations in the indoor air. The moisture content of the indoor air significantly affected all measurable airborne concentrations.     

Microbial Growth Inside Insulated External Walls as an Indoor Air Biocontamination Source

The association between moisture-related microbial growth (mesophilic fungi and bacteria) within insulated exterior walls and microbial concentrations in the indoor air was studied. The studied apartment buildings with precast concrete external walls were situated in a subarctic zone. Actinomycetes in the insulation layer were found to have increased concentrations in the indoor air. The moisture content of the indoor air significantly affected all measurable airborne concentrations.     

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.     

Alkaline single cell gel electrophoresis and human biomonitoring for genotoxicity: a study on subjects with residential exposure to radon.

Based on theoretical estimates and various correlation studies, it has been suggested that ingestion of radon in drinking water represents an increased risk for cancer. Such a risk has never been conclusively shown in epidemiological or experimental animal studies, however, and it has been questioned whether the radon level in the drinking water is of any significance in terms of overall radon exposure. Using primary DNA damage as a biological marker for an ongoing exposure to ionising radiation, the present study was undertaken to investigate whether people with different types of residential radon exposures differed with regard to their levels of DNA damage in circulating lymphocytes. DNA damage was measured in coded blood samples from 125 residents living in 45 households with different levels of radon-222 in the drinking water (10-2410 Bq/l) and indoor air (35-1025 Bq/m3) using alkaline single cell gel electrophoresis (the 'Comet' assay). Increased levels of radon in indoor air (>200 Bq/m3) were found to be associated with an increased level of DNA damage in peripheral lymphocytes (P相似文献   

Profiles of airborne fungi in buildings and outdoor environments in the United States

We examined 12,026 fungal air samples (9,619 indoor samples and 2,407 outdoor samples) from 1,717 buildings located across the United States; these samples were collected during indoor air quality investigations performed from 1996 to 1998. For all buildings, both indoor and outdoor air samples were collected with an Andersen N6 sampler. The culturable airborne fungal concentrations in indoor air were lower than those in outdoor air. The fungal levels were highest in the fall and summer and lowest in the winter and spring. Geographically, the highest fungal levels were found in the Southwest, Far West, and Southeast. The most common culturable airborne fungi, both indoors and outdoors and in all seasons and regions, were Cladosporium, Penicillium, nonsporulating fungi, and Aspergillus. Stachybotrys chartarum was identified in the indoor air in 6% of the buildings studied and in the outdoor air of 1% of the buildings studied. This study provides industrial hygienists, allergists, and other public health practitioners with comparative information on common culturable airborne fungi in the United States. This is the largest study of airborne indoor and outdoor fungal species and concentrations conducted with a standardized protocol to date.     

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.     

Air- and dustborne mycoflora in houses free of water damage and fungal growth

Typically, studies on indoor fungal growth in buildings focus on structures with known or suspected water damage, moisture, and/or indoor fungal growth problems. Reference information on types of culturable fungi and total fungal levels are generally not available for buildings without these problems. This study assessed 50 detached single-family homes in metropolitan Atlanta, Ga., to establish a baseline of "normal and typical" types and concentrations of airborne and dustborne fungi in urban homes which were predetermined not to have noteworthy moisture problems or indoor fungal growth. Each home was visually examined, and samples of indoor and outdoor air and of indoor settled dust were taken in winter and summer. The results showed that rankings by prevalence and abundance of the types of airborne and dustborne fungi did not differ from winter to summer, nor did these rankings differ when air samples taken indoors were compared with those taken outdoors. Water indicator fungi were essentially absent from both air and dust samples. The air and dust data sets were also examined specifically for the proportions of colonies from ecological groupings such as leaf surface fungi and soil fungi. In the analysis of dust for culturable fungal colonies, leaf surface fungi constituted a considerable portion (>20%) of the total colonies in at least 85% of the samples. Thus, replicate dust samples with less than 20% of colonies from leaf surface fungi are unlikely to be from buildings free of moisture or mold growth problems.     

Profiles of Airborne Fungi in Buildings and Outdoor Environments in the United States

We examined 12,026 fungal air samples (9,619 indoor samples and 2,407 outdoor samples) from 1,717 buildings located across the United States; these samples were collected during indoor air quality investigations performed from 1996 to 1998. For all buildings, both indoor and outdoor air samples were collected with an Andersen N6 sampler. The culturable airborne fungal concentrations in indoor air were lower than those in outdoor air. The fungal levels were highest in the fall and summer and lowest in the winter and spring. Geographically, the highest fungal levels were found in the Southwest, Far West, and Southeast. The most common culturable airborne fungi, both indoors and outdoors and in all seasons and regions, were Cladosporium, Penicillium, nonsporulating fungi, and Aspergillus. Stachybotrys chartarum was identified in the indoor air in 6% of the buildings studied and in the outdoor air of 1% of the buildings studied. This study provides industrial hygienists, allergists, and other public health practitioners with comparative information on common culturable airborne fungi in the United States. This is the largest study of airborne indoor and outdoor fungal species and concentrations conducted with a standardized protocol to date.     

Air- and Dustborne Mycoflora in Houses Free of Water Damage and Fungal Growth

Typically, studies on indoor fungal growth in buildings focus on structures with known or suspected water damage, moisture, and/or indoor fungal growth problems. Reference information on types of culturable fungi and total fungal levels are generally not available for buildings without these problems. This study assessed 50 detached single-family homes in metropolitan Atlanta, Ga., to establish a baseline of “normal and typical” types and concentrations of airborne and dustborne fungi in urban homes which were predetermined not to have noteworthy moisture problems or indoor fungal growth. Each home was visually examined, and samples of indoor and outdoor air and of indoor settled dust were taken in winter and summer. The results showed that rankings by prevalence and abundance of the types of airborne and dustborne fungi did not differ from winter to summer, nor did these rankings differ when air samples taken indoors were compared with those taken outdoors. Water indicator fungi were essentially absent from both air and dust samples. The air and dust data sets were also examined specifically for the proportions of colonies from ecological groupings such as leaf surface fungi and soil fungi. In the analysis of dust for culturable fungal colonies, leaf surface fungi constituted a considerable portion (>20%) of the total colonies in at least 85% of the samples. Thus, replicate dust samples with less than 20% of colonies from leaf surface fungi are unlikely to be from buildings free of moisture or mold growth problems.     

Design and performance of a trickling air biofilter for chlorobenzene and o-dichlorobenzene vapors.

From contaminated industrial sludge, two stable multistrain microbial enrichments (consortia) that were capable of rapidly utilizing chlorobenzene and o-dichlorobenzene, respectively, were obtained. These consortia were characterized as to their species composition, tolerance range, and activity maxima in order to establish and maintain the required operational parameters during their use in biofilters for the removal of chlorobenzene contaminants from air. The consortia were immobilized on a porous perlite support packed into filter columns. Metered airstreams containing the contaminant vapors were partially humidified and passed through these columns. The vapor concentrations prior to and after biofiltration were measured by gas chromatography. Liquid was circulated concurrently with the air, and the device was operated in the trickling air biofilter mode. The experimental arrangement allowed the independent variation of liquid flow, airflow, and solvent vapor concentrations. Bench-scale trickling air biofilters removed monochlorobenzene, o-dichlorobenzene, and their mixtures at rates of up to 300 g of solvent vapor h(-1) m(-3) filter volume. High liquid recirculation rates and automated pH control were critical for stable filtration performance. When the accumulating NaCl was periodically diluted, the trickling air biofilters continued to remove chlorobenzenes for several months with no loss of activity. The demonstrated high performance and stability of the described trickling air biofilters favor their use in industrial-scale air pollution control.     

Health Risk Assessment of Inhalation Exposure to Formaldehyde and Benzene in Newly Remodeled Buildings,Beijing

Objective

To assess health risks associated with inhalation exposure to formaldehyde and benzene mainly emitted from building and decoration materials in newly remodeled indoor spaces in Beijing.

Methods

We tested the formaldehyde and benzene concentrations in indoor air of 410 dwellings and 451 offices remodeled within the past year, in which the occupants had health concerns about indoor air quality. To assess non-carcinogenic health risks, we compared the data to the health guidelines in China and USA, respectively. To assess carcinogenic health risks, we first modeled indoor personal exposure to formaldehyde and benzene using the concentration data, and then estimated the associated cancer risks by multiplying the indoor personal exposure by the Inhalation Unit Risk values (IURs) provided by the U.S. EPA Integrated Risk Information System (U.S. EPA IRIS) and the California Office of Environmental Health Hazard Assessment (OEHHA), respectively.

Results

(1) The indoor formaldehyde concentrations of 85% dwellings and 67% offices were above the acute Reference Exposure Level (REL) recommended by the OEHHA and the concentrations of all tested buildings were above the chronic REL recommended by the OEHHA; (2) The indoor benzene concentrations of 12% dwellings and 32% offices exceeded the reference concentration (RfC) recommended by the U.S. EPA IRIS; (3) The median cancer risks from indoor exposure to formaldehyde and benzene were 1,150 and 106 per million (based on U.S. EPA IRIS IURs), 531 and 394 per million (based on OEHHA IURs).

Conclusions

In the tested buildings, formaldehyde exposure may pose acute and chronic non-carcinogenic health risks to the occupants, whereas benzene exposure may pose chronic non-carcinogenic risks to the occupants. Exposure to both compounds is associated with significant carcinogenic risks. Improvement in ventilation, establishment of volatile organic compounds (VOCs) emission labeling systems for decorating and refurbishing materials are recommended to reduce indoor VOCs exposure.     

Use of the IEUBK Model for Determination of Exposure Routes in View of Site Remediation

The Integrated Exposure Uptake Biokinetic (IEUBK) model is frequently used to estimate blood lead concentrations of children exposed to lead. Simulations with the IEUBK model were run to estimate the blood lead concentration in children living in the vicinity of a non-ferrous plant, situated in Hoboken, Belgium. Concentrations in soil ranged from 59–2425 mg Pb/kg dm, average concentrations in house dust ranged from 234–73394 mg Pb/kg dm. Measured blood lead concentrations in children aged 2–7 years were between 3 and 35 μ g/dl. Exposure sources were indoor dust in the house and the school, outdoor dust and soil in the home surrounding and at the school's playground, and suspended dust in the air. Soil ingestion values and lead exposure from food were changed to Flemish values. The model was able to predict the measured blood lead concentrations adequately except for the lowest exposure group. Predictions showed a systematic overestimation. Analysis of the data revealed that the neighbourhood's school is an important source of exposure to lead; indoor house dust dominates exposure for children going to school outside the area, because of the high concentrations of lead in indoor dust (3 to 5 times higher than in outdoor soil).     

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.     

Detection of airborne Stachybotrys chartarum macrocyclic trichothecene mycotoxins in the indoor environment

The existence of airborne mycotoxins in mold-contaminated buildings has long been hypothesized to be a potential occupant health risk. However, little work has been done to demonstrate the presence of these compounds in such environments. The presence of airborne macrocyclic trichothecene mycotoxins in indoor environments with known Stachybotrys chartarum contamination was therefore investigated. In seven buildings, air was collected using a high-volume liquid impaction bioaerosol sampler (SpinCon PAS 450-10) under static or disturbed conditions. An additional building was sampled using an Andersen GPS-1 PUF sampler modified to separate and collect particulates smaller than conidia. Four control buildings (i.e., no detectable S. chartarum growth or history of water damage) and outdoor air were also tested. Samples were analyzed using a macrocyclic trichothecene-specific enzyme-linked immunosorbent assay (ELISA). ELISA specificity was tested using phosphate-buffered saline extracts of the fungal genera Aspergillus, Chaetomium, Cladosporium, Fusarium, Memnoniella, Penicillium, Rhizopus, and Trichoderma, five Stachybotrys strains, and the indoor air allergens Can f 1, Der p 1, and Fel d 1. For test buildings, the results showed that detectable toxin concentrations increased with the sampling time and short periods of air disturbance. Trichothecene values ranged from <10 to >1,300 pg/m3 of sampled air. The control environments demonstrated statistically significantly (P < 0.001) lower levels of airborne trichothecenes. ELISA specificity experiments demonstrated a high specificity for the trichothecene-producing strain of S. chartarum. Our data indicate that airborne macrocyclic trichothecenes can exist in Stachybotrys-contaminated buildings, and this should be taken into consideration in future indoor air quality investigations.     

Indoor and outdoor pollen concentrations in private and public spaces during the <Emphasis Type="Italic">Betula</Emphasis> pollen season

Although the number of studies of pollen concentrations inside and outside buildings is increasing, little is known about the efficiency of penetration of pollen from outdoor to indoor air, and further. We studied indoor and outdoor pollen concentrations in the town of Lappeenranta and in the municipality of Rautjärvi in SE Finland from May 3–23, 2004, i.e. throughout the Betula pollen season, and assessed the risk of exposure to pollen grains. Pollen concentrations were measured inside and outside a block of flats, a detached house, and the regional central hospital, using rotorod-type samplers; in the town of Joutseno data were compared with Burkard counts. Outdoor concentrations of Betula pollen grains ranged between low and abundant (0–855 grains m^?3). The corresponding indoor concentrations near the main front doors varied from low to moderate (0–17 grains m^?3) in the central hospital and were low (<10 grains m^?3) in both residential buildings. Indoor concentrations further from the main front door were low (<10 grains m^?3) at all study sites. The concentrations of Betula pollen decreased substantially from outdoors to indoors, and further toward the centre of the building, probably indicating relatively poor penetrating properties of the pollen grains and/or the short-lived presence of pollen grains in indoor air. The concentrations of Betula pollen inside the buildings during the peak flowering period were mostly at a level barely inducing reactions even in the most sensitive persons.