Modeling the resiliency of energy‐efficient retrofits in low‐income multifamily housing

Residential energy efficiency and ventilation retrofits (eg, building weatherization, local exhaust ventilation, HVAC filtration) can influence indoor air quality (IAQ) and occupant health, but these measures’ impact varies by occupant activity. In this study, we used the multizone airflow and IAQ analysis program CONTAM to simulate the impacts of energy retrofits on indoor concentrations of PM_2.5 and NO₂ in a low‐income multifamily housing complex in Boston, Massachusetts (USA). We evaluated the differential impact of residential activities, such as low‐ and high‐emission cooking, cigarette smoking, and window opening, on IAQ across two seasons. We found that a comprehensive package of energy and ventilation retrofits was resilient to a range of occupant activities, while less holistic approaches without ventilation improvements led to increases in indoor PM_2.5 or NO₂ for some populations. In general, homes with simulated concentration increases included those with heavy cooking and no local exhaust ventilation, and smoking homes without HVAC filtration. Our analytical framework can be used to identify energy‐efficient home interventions with indoor retrofit resiliency (ie, those that provide IAQ benefits regardless of occupant activity), as well as less resilient retrofits that can be coupled with behavioral interventions (eg, smoking cessation) to provide cost‐effective, widespread benefits.     

Ventilation in public housing: implications for indoor nitrogen dioxide concentrations

Although elevated nitrogen dioxide (NO2) exposures may exacerbate asthma, few studies have examined indoor NO2 levels in low-income, urban neighborhoods, where asthma prevalence is high. As part of the Healthy Public Housing Initiative, NO2 was measured in 77 homes within three Boston public housing developments, using Palmes tubes placed in the kitchen, living room, and outdoors. Air exchange rates (AERs) were assessed using a perfluorocarbon tracer technique. Overall NO2 levels were [mean (ppb)+/-s.d.]: kitchen (43+/-20, n=100), living room (36+/-17, n=102), outdoor (19+/-6, n=91). Indoor NO2 levels were significantly higher in the heating season (living room: 43 ppb vs. 26 ppb, kitchen: 50 ppb vs. 33 ppb), while AERs were significantly lower in the heating season (medians 0.49/h vs. 0.85/h). Significant univariate predictors of indoor concentrations include: outdoor NO2 levels, AERs, and occupancy. AERs and outdoor NO2 remained significant in multivariate models (P<0.05). A dummy variable for supplemental heating with gas stove was not significant (P=0.14), but had a large, positive coefficient. Indoor NO2 levels in this cohort are higher than those generally reported in residential US settings, associated in part with increased gas stove usage and decreased AERs during the heating season. PRACTICAL IMPLICATIONS: Indoor air quality is mainly a function of outdoor concentrations, indoor sources, ventilation, and residential behavior. Indoor exposures to nitrogen dioxide and other combustion pollutants may be elevated within low-income housing developments due to the presence of multiple sources, poor ventilation, small apartment size, and behavioral responses to apartment conditions (e.g. supplemental heating with gas stove). This information may be used by housing authorities and other landlords to decrease potential environmental stressors, through interventions such as source substitution and improved ventilation, particularly for sensitive sub-populations such as asthmatics.     

Indoor air quality investigation at air-conditioned and non-air-conditioned markets in Hong Kong

To characterize indoor air quality at the markets in Hong Kong, three non-air-conditioned and two air-conditioned markets were selected for this study. The indoor air pollutants measured included PM(10) (particulate matters with aerodynamic diameter less than 10 microm), total bacteria count (TBC), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO(2)) and sulfur dioxide (SO(2)). The indoor and outdoor concentrations of these target air pollutants at these markets were measured and compared. The effects of air conditioning, temperature/relative humidity variation and different stalls on the indoor air quality were also investigated. The results indicated that all of the average indoor concentrations of PM(10), TBC, CO and NO(2) at the markets were below the Hong Kong Indoor Air Quality Objectives (HKIAQO) standards with a few exceptions for PM(10) and TBC. The elevated PM(10) concentrations at Hung Hom, Ngau Tau Kok and Wan Chai markets were probably due to the air filtration of outdoor airborne particulates emitted from vehicular exhaust, whereas high concentrations of airborne bacteria at Sai Ying Pun and Tin Shing markets were linked to the use of air conditioning. Correlation analysis demonstrated that indoor bacteria concentrations were correlated with temperature and relative humidity. The operation of air conditioning did not significantly reduce the levels of air pollutants at the markets. However, the higher indoor/outdoor ratios demonstrated that the operation of air conditioning had influence on the levels of bacteria at the markets. It was found that average PM(10) concentration at poultry stalls was higher than the HKIAQO standard of 180 microg/m(3), and was over two times that measured at vegetable, fish and meat stalls. Furthermore, the concentration of airborne bacteria at the poultry stalls was as high as 1031 CFU/m(3), which was above the HKIAQO standard of 1000 CFU/m(3). The bacteria levels at other three stalls were all below the HKIAQO standard. Statistical analysis indicated that there were no significant differences among the four stalls for CO, NO(x) and SO(2).     

Airborne particulate matter and gaseous air pollutants in residential structures in Lodi province, Italy

The province of Lodi is located in northern Italy on the Po River plain, where high background levels of air pollutants are prevalent. Lodi province is characterized by intensive agriculture, notably animal husbandry. This paper assesses indoor levels of selected airborne pollutants in 60 homes in the province, with special attention to size-fractionated particulate matter (PM). Indoor PM?.? concentrations are frequently higher than current guidelines. PM?? and nitrogen dioxide also exceed the respective guideline recommendations in some cases, noting that 24-h nitrogen dioxide levels were compared with an annual limit value. All other studied pollutant levels are below current international guidelines. Among indoor PM size fractions, PM?.? is predominant in terms of mass concentrations corresponding to 57% of PM?? in summer and 71% in winter. A strong seasonal trend is observed for all studied pollutants, with higher levels in winter corresponding to changes in ambient concentrations. The seasonal variation in PM?? is largely due to PM?.? increase from summer to winter. Summer indoor PM levels are mainly from indoor-generated particles, while particles of outdoor origin represent the main contribution to winter indoor PM levels. On average, indoor concentrations of coarse PM are mostly constituted by indoor-generated particles. PRACTICAL IMPLICATIONS: This study presents a comparison between measured indoor concentrations in the study area and indoor air quality guideline criteria. Accordingly, particulate matter (PM) and NO? are identified as key pollutants that may pose health concerns. It is also found that indoor PM in residential units is mainly constituted by particles with aerodynamic diameters <0.5 μm, especially in winter. Risk mitigation strategies should be focused on the reduction in indoor levels of NO? and ultrafine and fine particles, both infiltrated from outdoors and generated by indoor sources.     

Sources and concentrations of indoor nitrogen dioxide in Hamburg (west Germany) and Erfurt (east Germany)

Here we report indoor and outdoor concentrations of NO2 for Erfurt and Hamburg and assess the contribution of the most important indoor sources (e.g. the presence of gas cooking ranges, smoking) and outdoor sources (traffic exhaust emissions). We examined the relative contribution of the different sources of NO2 to the total indoor NO2 levels in Erfurt and Hamburg. NO2 indoor concentrations in Hamburg were slightly higher than those in Erfurt (i.e. living room: 15 microg m(-3) for Erfurt and 17 microg m(-3) for Hamburg). A linear regression model including the variables, place of residence, season and outdoor NO2 levels, location of the home within the city, housing and occupant characteristics accounted for 38% of the NO2 variance. The most important predictors of indoor NO2 concentrations were gas in cooking followed by other characteristics, such as ventilation or outdoor NO2 level. Residences in which gas was used for cooking, or in which occupants smoked, had substantially higher indoor NO2 concentrations (41 or 18% increase, respectively). An increase in the outdoor NO2 concentration from the 25th to the 75th-percentile (17 microg m(-3)) was associated with a 33% increase in the living room NO2 concentration. Multiple regression analysis for both cities separately illustrated that use of gas for cooking was the major indoor source of NO2. This variable caused a similar increase in the indoor NO2 levels in each city (43% in Erfurt and 47% in Hamburg). However, outdoor sources of NO2 (motor vehicle traffic) contributed more to indoor NO2 levels in Hamburg than in Erfurt.     

Modeled infiltration rate distributions for U.S. housing

A set of 209 dwellings that represent 80% of U.S. housing stock is used to generate frequency distributions of residential infiltration rates. The set of homes is based on an analysis of the 1997 U.S. Department of Energy's Residential Energy Consumption Survey, which documents numerous housing characteristics including type, floor area, number of rooms, type of heating system, foundation type, and year of construction. The infiltration rate distributions are developed using the multizone network airflow model, CONTAM (CONTAMW 2.4 User Guide and Program Documentation, NISTIR 7251. National Institute of Standards and Technology.). In this work, 19 cities are selected to represent U.S. climatic conditions, and CONTAM simulations are performed for each of the 209 houses in these cities to calculate building air change rates for each hour over a year. Frequency distributions are then developed and presented nationally as well as based on house type and region. PRACTICAL IMPLICATIONS: These distributions will support indoor air quality, exposure, and energy analyses based on a truly representative collection of U.S. homes, which has previously not been possible. In addition, the methodology employed can be extended to other countries and other collections of buildings. For U.S.-specific analyses, these homes and their models, can be extended to include occupants, contaminant sources, and other building features to allow a wide range of studies to address other ventilation and indoor air quality issues.     

Structural Disparities of Urban Traffic in Southern California: Implications for Vehicle‐Related Air Pollution Exposure in Minority and High‐Poverty Neighborhoods

Abstract: Structural inequalities provide an important context for understanding and responding to the impact of high traffic densities on disadvantaged neighborhoods. Emerging atmospheric science and epidemiological research indicates hazardous vehicle‐related pollutants (e.g., diesel exhaust) are highly concentrated near major roadways, and the prevalence of respiratory ailments and mortality are heightened in these high‐traffic corridors. This article builds on recent findings that low‐income and minority children in California disproportionately reside in high‐traffic areas by demonstrating how the urban structure provides a critical framework for evaluating the causes, characteristics, and magnitude of traffic, particularly for disadvantaged neighborhoods. We find minority and high‐poverty neighborhoods bear over two times the level of traffic density compared to the rest of the Southern California region, which may associate them with a higher risk of exposure to vehicle‐related pollutants. Furthermore, these areas have older and more multifamily housing, which is associated with higher rates of indoor exposure to outdoor pollutants, including intrusion of motor vehicle exhaust. We discuss the implications of these patterns on future planning and policy strategies for mitigating the serious health consequences of exposure to vehicle‐related air pollutants.     

Reduction in personal exposures to particulate matter and carbon monoxide as a result of the installation of a Patsari improved cook stove in Michoacan Mexico

The impact of an improved wood burning stove (Patsari) in reducing personal exposures and indoor concentrations of particulate matter (PM(2.5)) and carbon monoxide (CO) was evaluated in 60 homes in a rural community of Michoacan, Mexico. Average PM(2.5) 24-h personal exposure was 0.29 mg/m(3) and mean 48-h kitchen concentration was 1.269 mg/m(3) for participating women using the traditional open fire (fogon). If these concentrations are typical of rural conditions in Mexico, a large fraction of the population is chronically exposed to levels of pollution far higher than ambient concentrations found by the Mexican government to be harmful to human health. Installation of an improved Patsari stove in these homes resulted in 74% reduction in median 48-h PM(2.5) concentrations in kitchens and 35% reduction in median 24-h PM(2.5) personal exposures. Corresponding reductions in CO were 77% and 78% for median 48-h kitchen concentrations and median 24-h personal exposures, respectively. The relationship between reductions in median kitchen concentrations and reductions in median personal exposures not only changed for different pollutants, but also differed between traditional and improved stove type, and by stove adoption category. If these reductions are typical, significant bias in the relationship between reductions in particle concentrations and reductions in health impacts may result, if reductions in kitchen concentrations are used as a proxy for personal exposure reductions when evaluating stove interventions. In addition, personal exposure reductions for CO may not reflect similar reductions for PM(2.5). This implies that PM(2.5) personal exposure measurements should be collected or indoor measurements should be combined with better time-activity estimates, which would more accurately reflect the contributions of indoor concentrations to personal exposures. PRACTICAL IMPLICATIONS: Installation of improved cookstoves may result in significant reductions in indoor concentrations of carbon monoxide and fine particulate matter (PM(2.5)), with concurrent but lower reductions in personal exposures. Significant errors may result if reductions in kitchen concentrations are used as a proxy for personal exposure reductions when evaluating stove interventions in epidemiological investigations. Similarly, time microenvironment activity models in these rural homes do not provide robust estimates of individual exposures due to the large spatial heterogeneity in pollutant concentrations and the lack of resolution of time activity diaries to capture movement through these microenvironments.     

Coupling the multizone airflow and contaminant transport software CONTAM with EnergyPlus using co-simulation

Building modelers need simulation tools capable of simultaneously considering building energy use, airflow and indoor air quality (IAQ) to design and evaluate the ability of buildings and their systems to meet today’s demanding energy efficiency and IAQ performance requirements. CONTAM is a widely-used multizone building airflow and contaminant transport simulation tool that requires indoor temperatures as input values. EnergyPlus is a prominent whole-building energy simulation program capable of performing heat transfer calculations that require interzone and infiltration airflows as input values. On their own, each tool is limited in its ability to account for thermal processes upon which building airflow may be significantly dependent and vice versa. This paper describes the initial phase of coupling of CONTAM with EnergyPlus to capture the interdependencies between airflow and heat transfer using co-simulation that allows for sharing of data between independently executing simulation tools. The coupling is accomplished based on the Functional Mock-up Interface (FMI) for Co-simulation specification that provides for integration between independently developed tools. A three-zone combined heat transfer/airflow analytical BESTEST case was simulated to verify the co-simulation is functioning as expected, and an investigation of a two-zone, natural ventilation case designed to challenge the coupled thermal/airflow solution methods was performed.     

Concentrations and determinants of NO2 in homes of Ashford, UK and Barcelona and Menorca, Spain

This study examined indoor nitrogen dioxide (NO2) concentrations in Ashford, Kent (UK), Menorca Island and Barcelona city (Spain) and the contribution of their most important indoor determinants (e.g. gas combustion appliances and cigarette smoking). The homes examined (n = 1421) were those from infants recruited for the Asthma Multicentre Infants Cohort Study, which aimed to assess, using a standard protocol, the effects of pre- and post-natal environmental exposures in the inception of atopy and asthma. Indoor NO2 was measured using passive filter badges placed on a living room wall of the homes for between 7 and 15 days. Homes in the three centers had significantly different concentrations of indoor NO2, with those in Barcelona showing the highest levels (median NO2 levels: 5.79, 6.06 and 23.87 p.p.b. in Ashford, Menorca and Barcelona, respectively). Multiple regression analysis showed that the principal indoor determinants of NO2 concentrations in the three cohorts were the heating/cooking fuel used in the house (gas fire increased average NO2 concentrations by 1.27-fold and gas cooker by 2.13 times), parental cigarette smoking and season of measurement. Those variables significantly related to indoor NO(2) accounted for 23, 14 and 39% of the variation in indoor NO2 concentration in Ashford, Barcelona and Menorca, respectively. In all the cohorts combined, 52% of the variation could be explained in this way. Although outdoor NO2 was not measured concurrently, its additional contribution was estimated. In conclusion, despite differences in indoor NO2 mean concentrations probably reflecting different outdoor NO2 level, home factors affecting indoor NO2 values and their specific contributions were constant across the three cohorts. PRACTICAL IMPLICATIONS: This study found that principal determinants associated to indoor NO2 in three different sites of Europe: Ashford (UK), Barcelona and Menorca (Spain) were the energy source present in the home and cigarette smoking, despite these areas presented different climates, levels of outdoor contamination, housing characteristics and ventilation behavior. It is suggested that interventions in homes of these three centers will need to address principally cigarette smoking and gas combustion appliances. These latter factors require institutional intervention, while cigarette smoking mainly require personal changes.     

Hazard assessment of chemical air contaminants measured in residences

Identifying air pollutants that pose a potential hazard indoors can facilitate exposure mitigation. In this study, we compiled summary results from 77 published studies reporting measurements of chemical pollutants in residences in the United States and in countries with similar lifestyles. These data were used to calculate representative mid-range and upper-bound concentrations relevant to chronic exposures for 267 pollutants and representative peak concentrations relevant to acute exposures for five activity-associated pollutants. Representative concentrations are compared to available chronic and acute health standards for 97 pollutants. Fifteen pollutants appear to exceed chronic health standards in a large fraction of homes. Nine other pollutants are identified as potential chronic health hazards in a substantial minority of homes, and an additional nine are identified as potential hazards in a very small percentage of homes. Nine pollutants are identified as priority hazards based on the robustness of measured concentration data and the fraction of residences that appear to be impacted: acetaldehyde; acrolein; benzene; 1,3-butadiene; 1,4-dichlorobenzene; formaldehyde; naphthalene; nitrogen dioxide; and PM(2.5). Activity-based emissions are shown to pose potential acute health hazards for PM(2.5), formaldehyde, CO, chloroform, and NO(2). PRACTICAL IMPLICATIONS: This analysis identifies key chemical contaminants of concern in residential indoor air using a comprehensive and consistent hazard-evaluation protocol. The identification of a succinct group of chemical hazards in indoor air will allow for successful risk ranking and mitigation prioritization for the indoor residential environment. This work also indicates some common household activities that may lead to the acute levels of pollutant exposure and identifies hazardous chemicals for priority removal from consumer products and home furnishings.     

Indoor and outdoor concentrations of RSP, NO2 and selected volatile organic compounds at 32 shoe stalls located near busy roadways in Seoul, Korea

It is suspected that persons who work in indoor environments near busy roadways are exposed to elevated levels of air pollutants during working hours. This study evaluated the potential exposure and source contribution associated with traffic-related air pollution for workers (polishers and repairmen) in shoe stalls from each of 32 districts during working hours in Seoul, Korea. The shoe stalls have been located at very close distances to the busy roadways. In this study, shoe stall workers could be exposed to high levels of respirable suspended particulate (RSP), nitrogen dioxide (NO(2)) and volatile organic compounds (VOCs) from outdoor sources such as traffic exhaust, as well as indoor sources in the shoe stalls such as dust on the shoes, portable gas ranges, organic solvents, adhesives and shoe polish. Compounds of particular note included indoor mean concentrations of benzene, toluene, m/p-xylene and o-xylene were 0.732, 6.777, 4.080 and 1.302 mg/m(3), respectively, in all shoe stalls. Mean indoor/outdoor ratios for toluene and m/p-xylene concentrations were 54.52 and 20.84, respectively. The contribution of vehicle exhaust emissions to indoor air quality of shoe stalls was identified by means of correlating the relationships between simultaneously measured air pollutant concentrations indoors and outdoors. Unlike RSP and NO(2), indoor VOCs concentrations of shoe stalls mainly originated from indoor sources vs. outdoor sources.     

Numerical investigation of airflow pattern and particulate matter transport in naturally ventilated multi-room buildings

This study reports on a numerical investigation of transport behavior of indoor airflow and size-dependent particulate matter (PM) in multi-room buildings. An indoor size-dependent PM transport approach, combining the Eulerian large-eddy simulation of turbulent flow with the Lagrangian particle trajectory tracking, was developed to investigate indoor airflow pattern and PM1/PM2.5/PM10 removal efficiency in naturally ventilated multi-room buildings. A displacement ventilation with a measured indoor PM10 profile in Taipei Metropolis as the initial condition was carried out to characterize spatial and temporal variations of indoor PM1/PM2.5/PM10 removal behavior. The effects of indoor airflow pattern on particle transport mechanisms, e.g., deposition, suspension, migration and escape, were analyzed. Two comparison scenarios, which considered the effects of no indoor partition and different air change rate, respectively, were also conducted. In comparison with the effectiveness of PM1/PM2.5/PM10 removal, the simulated results showed that coarse particles were easier to be removed out of the building than fine particles. Natural ventilation was not an effective way to remove fine particles such as PM1 and PM2.5 in a multi-room building. Indoor partitions can impede 12% of the mean streamwise velocities and significantly increase 30-50% turbulence intensities. However, indoor partitions increased particle deposition and decreased particle escape. As a result of the two opposite particle removal mechanisms, i.e., deposition and escape, the impact of indoor partitions on PM1/PM2.5/PM10 removal behavior was not as significant as the results of airflow velocities. PRACTICAL IMPLICATIONS: This work developed a computational fluid dynamics technique to investigate indoor airflow patterns and PM1/PM2.5/PM10 removal ability in ventilated multi-room buildings. The results of this paper can help to identify adequate PM1/PM2.5/PM10 cleaning procedure and provide useful size-dependent PM control strategy in multi-room buildings.     

Measurements of children's exposures to particles and nitrogen dioxide in Santiago, Chile

An exposure study of children (aged 10-12 years) living in Santiago, Chile, was conducted. Personal, indoor and outdoor fine and inhalable particulate matter (< 2.5 .m in diameter, PM2.5 and < 10 microm in diameter, PM10, respectively), and nitrogen dioxide (NO2) were measured during pilot (N = 8) and main (N = 20) studies, which were conducted during the winters of 1998 and 1999, respectively. For the main study, personal, indoor and outdoor 24-h samples were collected for five consecutive days. Similar mean personal, indoor and outdoor PM2.5 concentrations (69.5, 68.5 and 68.1 microg/m3, respectively) were found. However, for coarse particles (calculated as the difference between measured PM10 and PM2.5, PM2.5-10), indoor and outdoor levels (35.4 and 47.4 microg/m3) were lower than their corresponding personal exposures (76.3 microg/m3). Indoor and outdoor NO2 concentrations were comparable (35.8 and 36.9 ppb) and higher than personal exposures (25.9 ppb). Very low ambient indoor and personal O3 levels were found, which were mostly below the method's limit of detection (LOD). Outdoor particles contributed significantly to indoor concentrations, with effective penetration efficiencies of 0.61 and 0.30 for PM2.5 and PM2.5-10, respectively. Personal exposures were strongly associated with indoor and outdoor concentrations for PM2.5, but weakly associated for PM2.5-10. For NO2, weak associations were obtained for indoor-outdoor and personal-outdoor relationships. This is probably a result of the presence of gas cooking stoves in all the homes. Median I/O, P/I and P/O ratios for PM2.5 were close to unity, and for NO2 they ranged between 0.64 and 0.95. These ratios were probably due to high ambient PM2.5 and NO2 levels in Santiago, which diminished the relative contribution of indoor sources and subjects' activities to indoor and personal PM2.5 and NO2 levels.     

Development and application of an updated whole-building coupled thermal,airflow and contaminant transport simulation program (TRNSYS/CONTAM)

The TRNSYS energy analysis tool has been capable of simulating whole-building coupled heat transfer and building airflow for about 10 years. The most recent implementation was based on two TRNSYS modules, Type 56 and Type 97. Type 97 is based on a subset of the airflow calculation capabilities of the CONTAM multizone airflow and contaminant transport program developed by the National Institute of Standards and Technology. This paper describes the development of new CONTAM capabilities in support of an updated combined, multizone building heat transfer, airflow and contaminant transport simulation approach using TRNSYS. It presents an illustrative case that highlights the new coupling capability and also presents the application of this coupled simulation approach to a practical design problem of the energy use related to airflow through entry doors in non-residential buildings.     

Characterization of indoor air quality in primary schools in Antwerp, Belgium

The indoor air quality of 27 primary schools located in the city centre and suburbs of Antwerp, Belgium, was assessed. The primary aim was to obtain correlations between the various pollutant levels. Indoor:outdoor ratios and the building and classroom characteristics of each school were investigated. This paper presents results on indoor and local outdoor PM2.5 mass concentrations, its elemental composition in terms of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb, Al, Si, S, and Cl, and its black smoke content. In addition, indoor and local outdoor levels of the gases NO2, SO2, O3, and BTEX (benzene, toluene, ethyl benzene, and xylene isomers) were determined. Black smoke, NO2, SO2 and O3, occurred at indoor:outdoor ratios below unity, indicating their significant outdoor sources. No linear correlation was established between indoor and outdoor levels for PM2.5 mass concentrations and BTEX; their indoor:outdoor ratios exceeded unity except for benzene. Classroom PM2.5 occurred with a different elemental composition than local outdoor PM2.5. The re-suspension of dust because of room occupation is probably the main contributor for the I/O ratios higher than 1 reported for elements typically constituting dust particles. Finally, increased benzene concentrations were reported for classrooms located at the lower levels. PRACTICAL IMPLICATIONS: The elevated indoor PM2.5, and BTEX concentrations in primary school classrooms, exceeding the ambient concentrations, raise concerns about possible adverse health effects on susceptible children. This is aggravated by the presence of carpets and in the case of classrooms at lower levels. Analysis of PM2.5's elemental composition indicated a considerable contribution of soil dust to indoor PM2.5 mass. In order to set adequate threshold values and guidelines, detailed information on the health impact of specific PM2.5 composites is needed. The results suggest that local outdoor air concentrations measurements do not provide an accurate estimation of children's personal exposures to the identified air pollutants inside classrooms.     

Model validation study of carbon monoxide transport due to portable electric generator operation in an attached garage

A series of tests was conducted to characterize the indoor carbon monoxide (CO) concentrations resulting from portable electric generators operating in the attached garage of a test house under various use and environmental conditions. An extensive model validation effort using the multizone airflow and indoor air quality (IAQ) model CONTAM was carried out using the data from seven tests with a generator operating in the attached garage to compare predicted CO concentrations with measured values. The agreement between the measurements and predictions of the O₂ concentrations in the garage and the average CO concentration for the house zones was excellent for the data set as a whole. The agreement was somewhat worse for the garage CO concentrations. Overall, the house zone average and garage CO concentration predictions and measurements were within about 20% and 30%, respectively, when averaged over all cases.     

Comparison of multiple environmental factors for asthmatic children in public housing

Nine families of a public housing development in Boston were enrolled in a pilot asthma intervention program designed to gather dense environmental data and generate hypotheses about the relative importance of different contaminants and the viability of interventions. Despite formidable challenges working with this inner-city population, the project team succeeded in gaining active support for the project by forming a partnership with a community-based organization and by building positive relationships between the field team and the residents. Families were provided with physical interventions such as air filters, industrial cleaning and mattress covers to each apartment. Indoor temperature was high and relative humidity low during winter. Insulation of exposed steam pipes did not lower temperature. Cockroach, mouse and pet antigen levels were variable and frequently high in settled dust. Viable fungal spore levels were variable and high in some apartments. Dust-mite allergen levels were below the level of concern. Industrial cleaning led to transient reduction in mouse and cockroach antigen burden. Mattress and pillow covers lowered dust-mite antigen in bedrooms, but not living rooms. Nitrogen dioxide (NO2) levels exceeded ambient concentrations due to use of gas stoves and concentrations of particulate matter with aerodynamic diameter <2.5 microm (PM2.5) were above ambient levels because of smoking. Air filtering systems did not reduce PM levels. Several volatile organic compounds (VOCs) were above adverse risk concentrations. We hypothesize that our findings are consistent with a multifactorial model for exacerbation of asthma in this population and that no single problem dominates.     

Relationships Between Indoor and Outdoor Contaminants in Mechanically Ventilated Buildings

Abstract It is shown that comparing measured indoor and outdoor contaminant concentrations can be misleading if the concentrations vary with time and if the averaging periods are too short. In this article an alternative methodology aimed at estimating the internal source and sink effects in mechanically ventilated buildings is described. The methodology is based on both the results from continuous measurements, and calculations under transient conditions. The relative importance of indoor sources and outdoor sources is established by a comparison of the measured indoor concentration and a calculated indoor concentration of a compound. Furthermore, dynamic calculations are used to investigate how the indoor concentrations of contaminants originating outdoors and contaminants emitted from indoor sources are influenced by temporal reductions of the airflow rate. Reducing the outdoor airflow rate during periods with high outdoor concentrations can significantly reduce the indoor levels of pollutants for situations in which the outdoor sources are more important than the indoor sources.     

Changing Water and Sewer Finance: Distributional Impacts and Effects on the Viability of Affordable Housing

Usage-based charges finance an increasing share of water and sewer costs in the U.S. The shift has been especially sharp in New York City, where residential users traditionally did not pay usage-based charges. In this article, we examine the impact that a transition to universal metered billing would have on multifamily housing. We find that universal metering would result in large increases in water and sewer bills for many multifamily buildings in low-income neighborhoods. Comparing the predicted increases with the net operating income of landlords in low-income neighborhoods indicates that universal metering might pose a threat to the viability of much affordable housing.