Abstract  Children have been identified as a subpopulation of concern for the evaluation of potential risks from chemicals. Tiered approaches to exposure assessments have been often used in regulatory assessment of different populations' exposures to chemicals. The goal of the tiered approach for exposure assessment is to begin with less complex, default-driven, screening methods and to proceed, when necessary, to mover complex, data-driven, chemical- and scenario-specific methods that reduce the uncertainty in estimates of exposure. Currently there are a wide number of software packages available, or under development, that can assist in various tiers of a children's exposure assessment. This paper begins with a brief review of the critical issues in the evaluation of children's exposures to chemicals (Section 2.0). The paper then presents a review of the exposure software (Section 3.0) an evaluates their potential for use at various points in a tiered evaluation (Section 4.0).

Abstract  The primary mission of the ARB Indoor Program is to identify and reduce Californians' exposures to indoor pollutants. To fully consider indoor exposures in assessing risk, the ARB needs estimates of average and peak indoor exposures for the general California population as well as certain subgroups of that population such as individuals who may be highly sensitive to indoor pollutants. The model described in this document--California Population Indoor Exposure Model, Version 2 (CPIEM 2.0)--is a software product that has been designed to expedite the exposure-assessment process by providing a user interface and calculation tools for supplying and integrating all required information. It is an enhanced version of the original CPIEM 1.4F released by ARB in 1998. Enhancements include greatly improved ease of use through a Windows interface, superior graphic outputs, an updated default database, as well as enhanced and new calculation capabilities, including uncertainty analysis. The CPIEM is a software tool that combines: • Air pollutant concentration distributions for several microenvironments, including outdoors, and • Population activity patterns that specify time spent in each microenvironment in a Monte Carlo framework to predict distributions of exposure concentrations for the California population. The default databases of microenvironment concentration distributions and activity patterns are specific to California, but the model allows the user to easily add his or her own data as well. For many air pollutants, the indoor concentration data are either sparse or nonexistent. To address this limitation, and to provide a means of evaluating hypothetical exposure reduction activities, the CPIEM also includes a mass-balance algorithm so that the user can estimate indoor concentration distributions based on distributional information for parameters such as indoor source emission rates, building volumes, and air exchange rates. The Windows platform of this new version of CPIEM greatly improves the software’s efficiency and ease of use with standard, easily understood drop-down menus and dialogue boxes. The graphic outputs are presentation quality. Scenarios are easily saved and edited to facilitate sensitivity analysis. The default databases have been updated with more recent data on indoor and outdoor pollutant concentrations, mass-balance parameters, and the demographic composition of California’s population. The exposure distributions predicted by CPIEM reflect the variability of exposure concentrations across population groups, but not our uncertainty about them. A new supplementary software program, designed to be used in conjunction with the new CPIEM, facilitates the estimation of the uncertainty of these exposure distributions. The uncertainty supplement creates alternative distributions for the CPIEM input variables with Monte Carlo sampling to reflect our uncertainty about the parameters of the input distributions. The user provides each alternative to CPIEM for iterative simulations. At the conclusion of the simulations of the alternatives the uncertainty supplement combines the resulting exposure distributions to estimate uncertainty distributions for selected percentile values. Other enhancements to the CPIEM capabilities include refinement of the pollutant removal process calculation in the mass-balance algorithm, and additional output metrics.

Abstract  The interim report presents the results of Phase III of the National Bureau of Standards General Indoor Air Pollution Concentration Model Project. It describes: (a) a general element-assembly formulation of multi-zone contaminant dispersal analysis theory that provides a general framework for the development of detailed (element) models of mass transport phenomena that may affect contaminant dispersal in buildings; (b) an approach to modeling the dispersal of interactive contaminants involving contaminant mass transport phenomena; (c) an approach to modeling the details of contaminant dispersal driven by convection-diffusion processes in one-dimensional flow situations (e.g., HVAC ductwork); and (d) the features and use of CONTAM87, a program that provides a computational implementation of the theory and methods discussed. Equations governing contaminant dispersal in the whole building air flow system due to air flow and reaction or sorption mass transport phenomena are formulated by assembling element equations, that characterize a specific instance of mass transport in the building air flow system.

Abstract  The manufacturing procedures and performance of a building air infiltration kit consisting of miniature passive perfluorocarbon tracer (PFT) permeation sources and passive adsorption tube samplers are described. Having four PFT-types available, homes and buildings with up to four separate zones can be fully evaluated under steady state conditions for the air infiltration and exfiltration rates from each zone as well as the air exchange rates between zones using this inexpensive and non-obtrusive field kit. Complete details on deployment in homes and on gas chromatographic analysis of the passive samplers are presented. Examples of total air changes per hour (ACH) results in several studies showed average values between 0.25 to 0.64 h/sup -1/. A generalized correlation was used to characterize the leakiness of eleven homes in the US and Canada, showing ACH dependency only on inside-outside temperature difference, wind speed to the 1.5 power, and a subjective terrain factor; the approach has application in evaluating weatherization performance. Details of multizone measurements in four homes provided insight into the role of attics, crawl-spaces, and basements on the indoor air quality and weatherization needs for the living zone.

Abstract  The report contains extensive documentation concerning the migration of additives from polymers to the environment. The additives and monomer residues can migrate from the plastic or elastomer over time. The rate and extent of migration is dependent on many factors such as temperature, the compatibility of the migrant with the polymer, the molecular size of the migrant, the compatibility of the migrant with the phase external to the polymer, and the interactions that may occur between the external phase and the polymer. The Exposure Evaluation Division (EED) of the Office of Pollution Prevention and Toxics is frequently required to assess the potential for exposure to chemicals that are used as additives in polymeric materials or are the monomers or low molecular weight oligomers contained in polymers. The task was undertaken with the objective of developing and documenting a defensible approach to assess the potential for release of chemical additives and reaction residues from polymeric materials. A family of mathematical models was developed and/or adapted for describing the migration of additives to gases, liquids and solids in contact with polymeric materials. In all cases, the user must specify the physical situation.

Abstract  Contains analyses of ten models developed in five participating countries. These range in complexity from 'single-cell' to 'multi-cell' approaches. Also contains numerical and climatic data for fourteen dwellings compiled to produce three key datasets which were used in model validation study.

Abstract  Most dwellings in the United States are ventilated primarily through leaks in the building shell (i.e., infiltration) rather than by whole-house mechanical ventilation systems. Consequently, quantification of envelope air-tightness is critical to determining how much energy is being lost through infiltration and how much infiltration is contributing toward ventilation requirements. Envelope air tightness and air leakage can be determined from fan pressurization measurements with a blower door. Tens of thousands of unique fan pressurization measurements have been made of U.S. dwellings over the past decades. LBNL has collected the available data on residential infiltration into its Residential Diagnostics Database, with support from the U.S. Department of Energy. This report documents the envelope air leakage section of the LBNL database, with particular emphasis on new construction. The work reported here is an update of similar efforts carried out a decade ago, which used available data largely focused on the housing stock, rather than on new construction. The current effort emphasizes shell tightness measurements made on houses soon after they are built. These newer data come from over two dozen datasets, including over 73,000 measurements spread throughout a majority of the U.S. Roughly one-third of the measurements are for houses identified as energy-efficient through participation in a government or utility program. As a result, the characteristics reported here provide a quantitative estimate of the impact that energy-efficiency programs have on envelope tightness in the US, as well as on trends in construction.

Abstract  Indoor air pollution is among the top five environmental health risks. Usually the best way to address this risk is to control or eliminate the sources of pollutants and ventilate a home with clean outdoor air. But opportunities for ventilation may be limited by weather conditions or by contaminants in the outdoor air. If the usual methods of addressing indoor air pollution are insufficient, air-cleaning devices may be useful. Air filters and other air-cleaning devices are designed to remove pollutants from indoor air. Some are installed in the ductwork of a home’s central heating, ventilating, and air-conditioning (HVAC) system to clean the air in the entire house. Portable room air cleaners can be used to clean the air in a single room or in specific areas, but they are not intended to filter the air in the whole house. Air-cleaning devices are categorized by the type of pollutants—particulate and gaseous—that the device is designed to remove or destroy.

Abstract  Personal exposure to air pollutants can be substantially higher in close proximity to an active source due to non-instantaneous mixing of emissions. The research presented in this paper quantifies this proximity effect for a non-buoyant source in 2 naturally ventilated homes in Northern California (CA), assessing its spatial and temporal variation and the influence of factors such as ventilation rate on its magnitude. To quantify how proximity to residential sources of indoor air pollutants affects human exposure, we performed 16 separate monitoring experiments in the living rooms of two detached single-family homes. CO (as a tracer gas) was released from a point source in the center of the room at a controlled emission rate for 5-12 h per experiment, while an array of 30-37 real-time monitors simultaneously measured CO concentrations with 15 s time resolution at radial distances ranging from 0.25-5 m under a range of ventilation conditions. Concentrations measured in close proximity (within 1 m) to the source were highly variable, with 5 min averages that typically varied by >100-fold. This variability was due to short-duration (<1 min) pollutant concentration peaks ("microplumes") that were frequently recorded in close proximity to the source. We decomposed the random microplume component from the total concentrations by subtracting predicted concentrations that assumed uniform, instantaneous mixing within the room and found that these microplumes can be modeled using a 3-parameter lognormal distribution. Average concentrations measured within 0.25 m of the source were 6-20 times as high as the predicted well-mixed concentrations.

Abstract  Epidemiologic evidence indicates a relationship between outdoor particle exposure and adverse health effects, while most people spend 85-90% of their time indoors, thus understanding the relationship between indoor and outdoor particles is quite important. This paper aims to provide an up-to-date revision for both experiment and modeling on relationship between indoor and outdoor particles. The use of three different parameters: indoor/outdoor (I/O) ratio, infiltration factor and penetration factor, to assess the relationship between indoor and outdoor particles were reviewed. The experimental data of the three parameters measured both in real houses and laboratories were summarized and analyzed. The I/O ratios vary considerably due to the difference in size-dependent indoor particle emission rates, the geometry of the cracks in building envelopes, and the air exchange rates. Thus, it is difficult to draw uniform conclusions as detailed information, which make I/O ratio hardly helpful for understanding the indoor/outdoor relationship. Infiltration factor represents the equilibrium fraction of ambient particles that penetrates indoors and remains suspended, which avoids the mixture with indoor particle sources. Penetration factor is the most relevant parameter for the particle penetration mechanism through cracks and leaks in the building envelope. We investigate the methods used in previously published studies to both measure and model the infiltration and penetration factors. We also discuss the application of the penetration factor models and provide recommendations for improvement. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  This paper analyzes the role of soil tracking as a source of indoor particles and quantifies key parameters influencing the transport of soil-derived particles (resuspension rates for particulate matter on floors, deposition velocities of suspended particles in indoor and outdoor air). The paper begins with a brief review of studies of particle transport processes and presents a simple model for studying the transport of particles in the indoor environment. The model is used to examine data on Pb distributions in the indoor and outdoor environments of community adjacent to a secondary lead smelter (paper no. 95-MP4.02).

Abstract  The purpose of this paper is to undertake a statistical analysis to specify empirical distributions and to estimate univariate parametric probability distributions for air exchange rates for residential structures in the United States. To achieve this goal, we used data compiled by the Brookhaven National Laboratory using a method known as the perfluorocarbon tracer (PFT) technique. While these data are not fully representative of all areas of the country or all housing types, they are judged to be by far the best available. The analysis is characterized by four key points: the use of data for 2,844 households; a four-region breakdown based on heating degree days, a best available measure of climatic factors affecting air exchange rates; estimation of lognormal distributions as well as provision of empirical (frequency) distributions; and provision of these distributions for all of the data, for the data segmented by the four regions, for the data segmented by the four seasons, and for the data segmented by a 16 region by season breakdown. Except in a few cases, primarily for small sample sizes, air exchange rates were found to be well fit by lognormal distributions (adjusted R2 0.95). The empirical or lognormal distributions may be used in indoor air models or as input variables for probabilistic human health risk assessments.

Abstract  This study was carried out using various materials (carpet, gypsum board, upholstery, vinyl and wood flooring, acoustic tiles, and fruit) that were exposed to eight gaseous volatile organic compounds (VOCs) (isopropanol, MTBE, cyclohexane, toluene, ethylbenzene, tetrachioroethene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene) in electro-polished stainless-steel chambers. Dynamic responses in VOC concentrations were used to determine linear adsorption and desorption rate coefficients and equilibrium partition coefficients. A linear adsorption/desorption model was used to effectively describe the interactions between VOCs and indoor surface materials for short-term source events (10 h). Relationships between sorption parameters and chemical vapor pressure and the octanol-air partition coefficient were observed. Carpet was identified as the most significant sorptive sink for non-polar VOCs. Virgin gypsum board was observed to be a significant sink for highly polar VOCs. Sorptive interactions between non-polar VOCs and indoor materials were not affected by variations in relative humidity. However, increases in relative humidity were observed to increase the degree of sorption of isopropanol to carpet.

Abstract  Data are presented on the air leakage characteristics of approximately 250 dwellings occupied by low-income households in 14 cities, in all major climatic zones of the United States. Two types of measurements were used: a tracer-gas decay technique using air sample bags, which was developed at the National Bureau of Standards to measure natural air infiltration; and a fan depressurization test that measures induced air exchange rates. The data presented here show that for this group of dwellings natural air infiltration rates are distributed approximately lognormally. The induced air exchange rates are a measure of the tightness of building envelopes. There is little correlation between the natural air infiltration rates and the induced air exchange rates in these dwellings, unless the buildings are divided into classes of similar buildings. The use of fan depressurization as a diagnostic tool to assist weatherization crews in tightening buildings is discussed. Preliminary estimates are presented of the reduction in induced air exchange rates that may be achieved by applying building weatherization techniques.

Abstract  One hundred and eighty eight volatile organic compounds (VOCs) were identified from dust emission, dust headspace, and in air sampling in a residence by sampling on Tenax TA followed by thermal desorption and HRGC/MS. Of these, 83 compounds were found in dust headspace. Aliphatic aldehydes (C4-8) and octane were major contributors to headspace gas chromatograms while the total ion current response for desorbed VOCs (120-degrees-C) was dominated by n-alkanes (C7-16), n- and branched alkanals (C4-10) and alkanoic acids (C2-C14). Many of the identified VOCs could be products of microbial or human metabolism. Dust volatiles resulting from desorption were compared to dust headspace VOC analyses and found to be comparable considering the temperature difference. A method for determination of total VOC (TVOC-dust) emission at 120-degrees-C, was developed. Variation in desorption TVOC analyses was mainly due to sample heterogeneity.

Abstract  We present a model for the growth of organic films on impermeable indoor surfaces. The model couples transport through a gas-side boundary layer adjacent to the surface with equilibrium partitioning of semivolatile organic compounds (SVOCs) between the gas phase and the surface film. Model predictions indicate that film growth would primarily be influenced by the gas-phase concentration of SVOCs with octanol-air partitioning (Koa ) values in the approximate range 10≤log Koa ≤13. Within the relevant range, SVOCs with lower values will equilibrate with the surface film more rapidly. Over time, the film becomes relatively enriched in species with higher log Koa values, while the proportion of gas-phase SVOCs not in equilibrium with the film decreases. Given stable airborne SVOC concentrations, films grow at faster rates initially and then subsequently diminish to an almost steady growth rate. Once an SVOC is equilibrated with the film, its mass per unit film volume remains constant, while its mass per unit area increases in proportion to overall film thickness. The predictions of the conceptual model and its mathematical embodiment are generally consistent with results reported in the peer-reviewed literature.

Abstract  This project serves as a comprehensive update to WRF’s 1999 Residential End Uses of Water study. This update includes more varied site locations, hot water end use data, more detailed landscape analysis, and expanded water rates analysis. This project focused solely on single-family residences. Deliverables include an Executive Report (4309A), a full report (4309B), and an Access Database (posted below under Web Tools). This database contains all of the end use water events recorded during the 2016 study, along with the survey response data, historic billing data, and other data obtained for each study site. The database also contains summary results from other end use studies. This resource can be utilized by researchers and WRF subscribers as a jumping off point for further research.

Abstract  The Residential Energy Consumption Survey (RECS) was designed by the Energy Information Administration (EIA) to provide information about energy consumption within the residential sector. The RECS is conducted in two major parts: the Household Survey and the Energy Suppliers Survey. The Household Survey collects information about the housing unit through personal interviews with a representative national sample of households. The Rental-Agent Survey is an adjunct to the Household Survey and is used to verify information provided by renters in the Household Survey. In the Energy Suppliers Survey, data concerning actual energy consumption are obtained from household billing records maintained by the energy suppliers. The data are collected by questionnaires mailed to all the suppliers for the households in the Household Survey. This electronic report is based on the results of the Household Survey. A later report, Household Energy Consumption and Expenditures 1997, will present the results of the Energy Suppliers Survey. A subcontractor to EIA was used to collect and process the 1997 RECS. Click for copies of the data collection forms for the Household Survey and the adjunct Rental-Agent Survey. This appendix contains detailed information about the sample design, Household Survey, its adjunct Rental Agent Survey, and confidentiality of the survey information.

Abstract  Fluctuating airflow may strongly influence the real air exchange rate when using natural ventilation, resulting in a larger “effective” air exchange rate than the “mean” air exchange rate calculated by conventional methods (i.e., the network method). To study the effective air exchange rate during natural ventilation under conditions of actual use, this study proposes a simple model that accounts for fluctuating airflow. The model assumes that the airflow near a building opening fluctuates regularly and velocity is assumed to have either a square or sine wave pattern. Our analysis shows that the effective air exchange rate is larger when accounting for fluctuating airflow. This suggests that the mean air exchange rate should not be calculated without consideration of real airflow fluctuations.

Abstract  Vapor intrusion occurs when volatile organic compounds (VOCs) from contaminated soil or groundwater migrate upwards toward the ground surface and into overlying buildings through gaps and cracks in foundation slabs or basement walls. The route VOCs take from a subsurface source to the air inside a building is referred to as the vapor intrusion pathway. Since the U.S. Environmental Protection Agency (EPA) published the 2002 EPA draft vapor intrusion guidance (Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils; EPA530-D-02-004, U.S. EPA, 2002), the understanding of the vapor intrusion pathway has grown substantially. This Conceptual Model Scenarios for the Vapor Intrusion Pathway technical document expands on the understanding and conceptualizations presented in that draft guidance document and those appearing subsequently in the Interstate Technology and Regulatory Council’s 2007 practical guideline (ITRC, 2007).