Shelly L . Miller - Profile on Academia.edu (original) (raw)
Papers by Shelly L . Miller
Buildings
Airborne transmission of SARS-CoV-2 mostly occurs indoors, and effective mitigation strategies fo... more Airborne transmission of SARS-CoV-2 mostly occurs indoors, and effective mitigation strategies for specific building types are needed. Most guidance provided during the pandemic focused on general strategies that may not be applicable for all buildings. A systematic evaluation of infection risk mitigation strategies for different public and commercial buildings would facilitate their reopening process as well as post-pandemic operation. This study evaluates engineering mitigation strategies for five selected US Department of Energy prototype commercial buildings (i.e., Medium Office, Large Office, Small Hotel, Stand-Alone Retail, and Secondary School). The evaluation applied the multizone airflow and contaminant simulation software, CONTAM, with a newly developed CONTAM-quanta approach for infection risk assessment. The zone-to-zone quanta transmission and quanta fate were analyzed. The effectiveness of mechanical ventilation, and in-duct and in-room air treatment mitigation strateg...
Time-Series PM2.5 Source Apportionment – Value of the Measurements
Some infectious diseases, including COVID-19, can be transmitted via aerosols that are emitted by... more Some infectious diseases, including COVID-19, can be transmitted via aerosols that are emitted by an infectious person and inhaled by susceptible individuals. Most airborne transmission occurs at close proximity and is effectively reduced by physical distancing, but as time indoors increases, infections occur in those sharing room air despite maintaining distancing. There have been calls for quantified models to estimate the absolute and relative contribution of these different factors to infection risk. We propose two indicators of infection risk for this situation, i.e., relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and particulate air cleaning rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend in relation to these factors that is consistent with airborne ...
Journal of Occupational and Environmental Hygiene, 2021
The various discontinuous processes by which an individual generates aerosols (e.g., exhaled brea... more The various discontinuous processes by which an individual generates aerosols (e.g., exhaled breaths, speaking, coughing) were modeled as a steady-state, continuous emission rate in the form of a lognormal distribution: 𝑎,ℎ )-ln(𝑑 𝑎,𝑙 ) √2𝜋×ln 𝐺𝑆𝐷 × 𝑒 (ln 𝑑 𝑎 -ln 𝐶𝑀𝐷) 2 2(ln 𝐺𝑆𝐷) 2 ] × Etot, aerosol × mask, exh(da) where E(da) is the aerosol emission rate for a single individual [particles s -1 ] for a given size bin, da is the aerosol aerodynamic diameter [m] (assumed to equal the midpoint of the size bin), f(da) is the lognormal size distribution function multiplied by the logarithmic size bin width (= ln(da,h)ln(da,l) = 0.8 for all bins), da,h and da,l are the upper and lower boundaries of the size bin, Etot is the total aerosol emission rate [particles s -1 ], mask(da) is the mask efficiency controlling aerosol emissions, and CMD and GSD are the count median diameter and geometric standard deviation of the lognormal distribution, respectively (Hinds 1982). Equation S1 was discretized and evaluated at 12 aerosol size bins spanning da = 0.02-120 m (Figure ) to enable more refined mask efficiency and deposition calculations and to compare to other models that use 3bin aerosol assumptions, e.g., (CDPH IAQ 2020). Nomenclature, assumed values, and uncertainties for all parameters are listed in Tables , and S2. The emission rates investigated were Etot, aerosol = 0.2-20 particles s -1 , a range spanning very quiet speaking to super-spreader, with CMD = 0.7 µm and GSD = 2.5 . The aerosol was assumed to have evaporated to this equilibrium size rapidly after exhalation
Environment International, 2020
Outbreaks from choir performances, such as the Skagit Valley Choir, showed that singing brings po... more Outbreaks from choir performances, such as the Skagit Valley Choir, showed that singing brings potential risk of COVID-19 infection. There is less known about the risks of airborne infection from other musical performances, such as playing wind instruments or performing theater. In addition, it is important to understand methods that can be used to reduce infection risk. In this study, we used a variety of methods, including flow visualization, aerosol and CO 2 measurements, and computational fluid dynamics (CFD) modeling to understand the different components that can lead to transmission risk from musical performance and risk mitigation. This study was possible because of a partnership across academic departments and institutions and collaboration with the National Federation of State High School Associations and the College Band Directors National Association. The interdisciplinary team enabled us to understand the various aspects of aerosol transmission risk from musical performance and to quickly implement strategies in music classrooms during the COVID-19 pandemic. We found that plumes from musical performance were highly directional, unsteady and varied considerably in time and space. Aerosol number concentration measured at the bell of the clarinet was comparable to that of singing. Face and bell masks attenuated plume velocities and lengths and decreased aerosol concentrations measured in front of the masks. CFD modeling showed differences between indoor and outdoor environments and that the lowest risk of airborne COVID-19 infection occurred at less than 30 min of exposure indoors and less than 60 min outdoors.
Journal of Hospital Infection, 2021
Since January 2020 Elsevier has created a COVID-19 resource centre with free information in Engli... more Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre -including this research content -immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active. Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus (SARS-CoV-2
Ventilation is of primary concern for maintaining healthy indoor air quality and reducing the spr... more Ventilation is of primary concern for maintaining healthy indoor air quality and reducing the spread of airborne infectious disease, including COVID-19. In addition to building-level guidelines, increased attention is being placed on room-level ventilation. However, for many universities and schools, ventilation data on a room-by-room basis are not available for classrooms and other key spaces. We present an overview of approaches for measuring ventilation along with their advantages and disadvantages. We also present data from recent case studies for a variety of institutions across the United States, with various building ages, types, locations, and climates, highlighting their commonalities and differences, and examples of the use of this data to support decision making.
Environmental Science & Technology, 2019
Journal of Exposure Science & Environmental Epidemiology, 2019
Previous research has found increased home ventilation, which may affect health by altering the c... more Previous research has found increased home ventilation, which may affect health by altering the composition of indoor air, is associated with improvement of respiratory health, but evidence linking home ventilation to objectively measured lung function is sparse. The Colorado Home Energy Efficiency and Respiratory health (CHEER) study, a cross-sectional study of low-income, urban, nonsmoking homes across the Northern Front Range of Colorado, USA, focused on elucidating this link. We used a multipoint depressurization blower door test to measure the air tightness of the homes and calculate the annual average infiltration rate (AAIR). Lung function tests were administered to eligible participants. We analyzed data from 253 participants in 187 homes with two or more acceptable spirometry tests. We used generalized estimating equations to model forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC), and FEV 1 /FVC z-scores as a function of AAIR. AAIRs ranged from 0.10 to 1.98 air changes per hour. Mean z-scores for FEV 1 , FVC, and FEV 1 /FVC were -0.57, 0.32, and -0.43, respectively. AAIR was positively associated with increased FEV 1 /FVC z-scores, such that a 1-unit change in AAIR corresponded to a half of a standard deviation in lung function (β = 0.51, CI: 0.02-0.99). These associations were strongest for healthy populations and weaker for those with asthma and asthma-like symptoms. AAIR was not associated with FEV 1 or FVC. Our study is the first in the United States to link home ventilation by infiltration to objectively measured lung function in low-income, urban households.
International Journal of Environmental Research and Public Health, 2019
Indoor and outdoor number concentrations of fine particulate matter (PM2.5), black carbon (BC), c... more Indoor and outdoor number concentrations of fine particulate matter (PM2.5), black carbon (BC), carbon monoxide (CO), and nitrogen dioxide (NO2) were monitored continuously for two to seven days in 28 low-income homes in Denver, Colorado, during the 2016 and 2017 wildfire seasons. In the absence of indoor sources, all outdoor pollutant concentrations were higher than indoors except for CO. Results showed that long-range wildfire plumes elevated median indoor PM2.5 concentrations by up to 4.6 times higher than outdoors. BC, CO, and NO2 mass concentrations were higher indoors in homes closer to roadways compared to those further away. Four of the homes with mechanical ventilation systems had 18% higher indoor/outdoor (I/O) ratios of PM2.5 and 4% higher I/O ratios of BC compared to other homes. Homes with exhaust stove hoods had PM2.5 I/O ratios 49% less than the homes with recirculating hoods and 55% less than the homes with no stove hoods installed. Homes with windows open for more t...
Environmental Science & Technology Letters, 2019
The lifetime of alkylperoxy radicals (RO 2 ) formed in the oxidation of volatile organic compound... more The lifetime of alkylperoxy radicals (RO 2 ) formed in the oxidation of volatile organic compounds (VOCs) is a key determinant of reaction mechanisms and products. When RO 2 • radical lifetimes are long, autoxidation reactions can form highly oxidized multifunctional compounds (HOMs) that are efficient at forming secondary organic aerosol (SOA). We measured the formation of HOMs resulting from the O 3 -initiated autoxidation of limonene emitted inside the University of Colorado Art Museum. Conditions inside the museum favored autoxidation for most of the 6-week study, indicating that autoxidation is prevalent indoors in the absence of an indoor combustion source of nitrogen oxide (NO). A box model of the museum was used with measurements of VOCs, O 3 , and NO x and air exchange to estimate HOM and SOA yields and to model the limonene oxidation rate. The HOM molar yield of 11% agrees well with the results of laboratory studies of limonene autoxidation, and the SOA mass yield of 47 ± 8% indicates that limonene autoxidation efficiently forms SOA indoors.
Sustainability, 2019
We studied 226 low-income households as a part of the Colorado Home Energy Efficiency and Respira... more We studied 226 low-income households as a part of the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study to investigate the relationship between energy-efficiency retrofits (EERs) specific to air sealing of residential building envelopes, annual average infiltration rates (AAIR), and qualitative indicators of “healthy” homes. Blower door tests quantified the leakage area in each home, which was used to estimate the AAIR. Walk-through inspections were used to record observations of air-sealing retrofits conducted as part of Colorado’s Weatherization Assistance Program and indirect indicators of poor indoor environmental quality (IEQ) in the homes, such as visible mold or stains, visible dust on hard surfaces, vapor condensation on windows, dampness, and perceived air quality. Results showed that building characteristics like age and volume affected AAIR more significantly than air-sealing EERs. Among the air-sealing EERs, homes with the air-handler ductwork sealed a...
Environmental Science & Technology, 2019
This document is 12 pages long and includes descriptions of the calibration procedures employed i... more This document is 12 pages long and includes descriptions of the calibration procedures employed in this study, descriptions of how the museum model was initialized, description of why recirculation fractions were presented in the text instead of deposition rate constants (Figure ), a table of variables and mathematical expressions used in the text (Table ), a table of reactions included in the model of the museum (Table ), tables of emission events (Tables ), and comparison of measured pollutant levels to published standards (Table ).
International Journal of Environmental Research and Public Health, 2019
Consensus is growing on the need to investigate the joint impact of neighborhood-level social fac... more Consensus is growing on the need to investigate the joint impact of neighborhood-level social factors and environmental hazards on respiratory health. This study used latent profile analysis (LPA) to empirically identify distinct neighborhood subtypes according to a clustering of social factors and environmental hazards, and to examine whether those subtypes are associated with lung function. The study included 182 low-income participants who were enrolled in the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study during the years 2015–2017. Distinct neighborhood typologies were identified based on analyses of 632 census tracts in the Denver-Metro and Front Range area of Colorado; neighborhood characteristics used to identify typologies included green space, traffic-related air pollution, violent and property crime, racial/ethnic composition, and socioeconomic status (SES). Generalized estimating equations were used to examine the association between neighborhood ty...
Building and Environment, 2018
Low-energy home design is becoming more common in new and retrofitted homes, and energy-efficient... more Low-energy home design is becoming more common in new and retrofitted homes, and energy-efficient designs often sell at a premium . Efficiency measures, like tightening the building envelope saves energy, but can impact the indoor air quality (IAQ). We monitored the IAQ of nine tightly constructed homes, one tightly constructed public library, and one conventionally constructed home, and performed a repeatable cooking activity to observe the impact of the fine particulate matter (PM2.5) emissions. We compared PM2.5 concentrations from the cooking activity while operating the mechanical ventilation systems at default rates (~0.1-0.3 h -1 ) and in a temporary boost mode (~0.3-0.8 h -1 ). We also measured the concentrations of total volatile organic compounds (TVOCs), formaldehyde, radon, and bedroom carbon dioxide (CO2) levels. Results show that PM2.5 concentrations are generally low indoors, but cooking drastically increases concentrations, which are slow to decay. No significant difference was found between operating the ventilators at standard rates and utilizing the temporary boost. Completely-mixed flow reactor models of select homes show that installing and using a directly-exhausting range hood can reduce peak PM2.5 concentrations by 75% or more. Current ventilation practices in these buildings may not be adequate for these common activities. Formaldehyde was above the California Office of Environmental Health Hazard Assessment (OEHHA) chronic limit of 9 µg/m 3 in all tight buildings with a median concentration of 30 µg/m 3 . CO2 levels in bedrooms exceeded 1000 ppm in six homes, indicating that bedroom ventilation practices are not consistent nor adequate.
Environmental science & technology, Jan 6, 2018
Diverse bacterial and fungal communities inhabit human-occupied buildings and circulate in indoor... more Diverse bacterial and fungal communities inhabit human-occupied buildings and circulate in indoor air; however, viral diversity in these man-made environments remains largely unknown. Here we investigated DNA and RNA viruses circulating in the air of 12 university dormitory rooms by analyzing dust accumulated over a one-year period on heating, ventilation, and air conditioning (HVAC) filters. A metagenomic sequencing approach was used to determine the identity and diversity of viral particles extracted from the HVAC filters. We detected a broad diversity of viruses associated with a range of hosts, including animals, arthropods, bacteria, fungi, humans, plants, and protists, suggesting that disparate organisms can contribute to indoor airborne viral communities. Viral community composition and the distribution of human-infecting papillomaviruses and polyomaviruses were distinct in the different dormitory rooms, indicating that airborne viral communities are variable in human-occupie...
Building and Environment, 2016
Cooling coil surfaces within building ventilation systems are ideal sites for biofilm formation d... more Cooling coil surfaces within building ventilation systems are ideal sites for biofilm formation due to the presence of adequate nutrients (deposited particles) and moisture (condensate). In this study, a heating, ventilation, and air-conditioning (HVAC) test apparatus was built consisting of two parallel ducts, each with its own cooling coil. One coil was exposed to ultraviolet germicidal coil cleaning (UVG-CC) while the other was the comparison control to investigate the impact of UVG-CC on surface microbial loading and bacterial attachment. Surface samples were collected by swabbing a uniform area of coil surface and airborne samples were collected isokinetically with sterile funnel filters. All samples were quantified via direct epifluorescent microscopy. Prior to irradiating, higher concentrations of surface microbial loading were found on the downstream side of both cooling coils under condensing conditions. Conversely, under dry surface conditions with downstream UV irradiance, surface concentrations were higher upstream. UVG-CC (at an average 200 uW/cm 2 on the coil surface) reduced surface microbial loading by 55% on average during condensing conditions and inhibited bacterial attachment causing clusters of bacterial matter to become airborne downstream of the cooling coil. Additionally, it was found that desiccation also inhibited surface microbial loading and yielded cluster detachment but to a lesser degree than UVG-CC treatment.
International Journal of Environmental Research and Public Health, 2017
The objectives of this study were to measure levels of particulate matter (PM) in mechanically ve... more The objectives of this study were to measure levels of particulate matter (PM) in mechanically ventilated buildings and to improve understanding of filtration requirements to reduce exposure. With the use of an Ultra High Sensitivity Aerosol Spectrometer and an Aerodyne Mass Spectrometer, ultrafine (0.055-0.1 µm) and fine (0.1-0.7 µm) indoor and outdoor PM was measured as a function of time in an office, a university building, and two elementary schools. Indoor particle levels were highly correlated with outdoor levels. Indoor and outdoor number concentrations in Denver were higher than those in Boulder, with the highest number concentrations occurring during summer and fall. The ratio of indoor-to-outdoor (I/O) PM was weakly but positively correlated with the amount of ventilation provided to the indoor environment, did not vary much with particle size (ranged between 0.48 and 0.63 for the entire size range), and was similar for each period of the week (weekend vs. weekday, night vs. day). Regression analyses showed that ultrafine indoor PM baseline concentrations were higher at night from nighttime infiltration. A lag time was observed between outdoor and indoor measurements. Weekday days had the shortest lag time of 11 min, and weekend nighttime lags when the HVAC was not in use were 50 to 148 min. Indoor-outdoor PM concentration plots showed ultrafine PM was more correlated compared to fine, and especially when the HVAC system was on. Finally, AMS data showed that most of the PM was organic, with occasional nitrate events occurring outdoors. During nitrate events, there were less indoor particles detected, indicating a loss of particulate phase nitrate. The results from this study show that improved filtration is warranted in mechanically ventilated buildings, particularly for ultrafine particles, and that nighttime infiltration is significant depending on the building design.
Building and Environment, 2016
Buildings represent habitats for microorganisms that can have direct or indirect effects on the q... more Buildings represent habitats for microorganisms that can have direct or indirect effects on the quality of our living spaces, health, and well-being. Over the last ten years, new research has employed sophisticated tools, including DNA sequencing-based approaches, to study microbes found in buildings and the overall built environment. These investigations have catalyzed new insights into and questions about the microbes that surround us in our daily lives. The emergence of the "microbiology of the built environment" field has required bridging disciplines, including microbiology, ecology, building science, architecture, and engineering. Early insights have included a fuller characterization of sources of microbes within buildings, important processes that structure the distributions and abundances of microbes, and a greater appreciation of the role that occupants can have on indoor microbiology. This ongoing work has also demonstrated that traditional culture-and microscopy-based approaches for studying microbiology vastly underestimate the types and quantity of microbes present in environmental samples. We offer ten questions that highlight important lessons learned regarding the microbiology of buildings and suggest future areas of investigation.
Buildings
Airborne transmission of SARS-CoV-2 mostly occurs indoors, and effective mitigation strategies fo... more Airborne transmission of SARS-CoV-2 mostly occurs indoors, and effective mitigation strategies for specific building types are needed. Most guidance provided during the pandemic focused on general strategies that may not be applicable for all buildings. A systematic evaluation of infection risk mitigation strategies for different public and commercial buildings would facilitate their reopening process as well as post-pandemic operation. This study evaluates engineering mitigation strategies for five selected US Department of Energy prototype commercial buildings (i.e., Medium Office, Large Office, Small Hotel, Stand-Alone Retail, and Secondary School). The evaluation applied the multizone airflow and contaminant simulation software, CONTAM, with a newly developed CONTAM-quanta approach for infection risk assessment. The zone-to-zone quanta transmission and quanta fate were analyzed. The effectiveness of mechanical ventilation, and in-duct and in-room air treatment mitigation strateg...
Time-Series PM2.5 Source Apportionment – Value of the Measurements
Some infectious diseases, including COVID-19, can be transmitted via aerosols that are emitted by... more Some infectious diseases, including COVID-19, can be transmitted via aerosols that are emitted by an infectious person and inhaled by susceptible individuals. Most airborne transmission occurs at close proximity and is effectively reduced by physical distancing, but as time indoors increases, infections occur in those sharing room air despite maintaining distancing. There have been calls for quantified models to estimate the absolute and relative contribution of these different factors to infection risk. We propose two indicators of infection risk for this situation, i.e., relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and particulate air cleaning rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend in relation to these factors that is consistent with airborne ...
Journal of Occupational and Environmental Hygiene, 2021
The various discontinuous processes by which an individual generates aerosols (e.g., exhaled brea... more The various discontinuous processes by which an individual generates aerosols (e.g., exhaled breaths, speaking, coughing) were modeled as a steady-state, continuous emission rate in the form of a lognormal distribution: 𝑎,ℎ )-ln(𝑑 𝑎,𝑙 ) √2𝜋×ln 𝐺𝑆𝐷 × 𝑒 (ln 𝑑 𝑎 -ln 𝐶𝑀𝐷) 2 2(ln 𝐺𝑆𝐷) 2 ] × Etot, aerosol × mask, exh(da) where E(da) is the aerosol emission rate for a single individual [particles s -1 ] for a given size bin, da is the aerosol aerodynamic diameter [m] (assumed to equal the midpoint of the size bin), f(da) is the lognormal size distribution function multiplied by the logarithmic size bin width (= ln(da,h)ln(da,l) = 0.8 for all bins), da,h and da,l are the upper and lower boundaries of the size bin, Etot is the total aerosol emission rate [particles s -1 ], mask(da) is the mask efficiency controlling aerosol emissions, and CMD and GSD are the count median diameter and geometric standard deviation of the lognormal distribution, respectively (Hinds 1982). Equation S1 was discretized and evaluated at 12 aerosol size bins spanning da = 0.02-120 m (Figure ) to enable more refined mask efficiency and deposition calculations and to compare to other models that use 3bin aerosol assumptions, e.g., (CDPH IAQ 2020). Nomenclature, assumed values, and uncertainties for all parameters are listed in Tables , and S2. The emission rates investigated were Etot, aerosol = 0.2-20 particles s -1 , a range spanning very quiet speaking to super-spreader, with CMD = 0.7 µm and GSD = 2.5 . The aerosol was assumed to have evaporated to this equilibrium size rapidly after exhalation
Environment International, 2020
Outbreaks from choir performances, such as the Skagit Valley Choir, showed that singing brings po... more Outbreaks from choir performances, such as the Skagit Valley Choir, showed that singing brings potential risk of COVID-19 infection. There is less known about the risks of airborne infection from other musical performances, such as playing wind instruments or performing theater. In addition, it is important to understand methods that can be used to reduce infection risk. In this study, we used a variety of methods, including flow visualization, aerosol and CO 2 measurements, and computational fluid dynamics (CFD) modeling to understand the different components that can lead to transmission risk from musical performance and risk mitigation. This study was possible because of a partnership across academic departments and institutions and collaboration with the National Federation of State High School Associations and the College Band Directors National Association. The interdisciplinary team enabled us to understand the various aspects of aerosol transmission risk from musical performance and to quickly implement strategies in music classrooms during the COVID-19 pandemic. We found that plumes from musical performance were highly directional, unsteady and varied considerably in time and space. Aerosol number concentration measured at the bell of the clarinet was comparable to that of singing. Face and bell masks attenuated plume velocities and lengths and decreased aerosol concentrations measured in front of the masks. CFD modeling showed differences between indoor and outdoor environments and that the lowest risk of airborne COVID-19 infection occurred at less than 30 min of exposure indoors and less than 60 min outdoors.
Journal of Hospital Infection, 2021
Since January 2020 Elsevier has created a COVID-19 resource centre with free information in Engli... more Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre -including this research content -immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active. Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus (SARS-CoV-2
Ventilation is of primary concern for maintaining healthy indoor air quality and reducing the spr... more Ventilation is of primary concern for maintaining healthy indoor air quality and reducing the spread of airborne infectious disease, including COVID-19. In addition to building-level guidelines, increased attention is being placed on room-level ventilation. However, for many universities and schools, ventilation data on a room-by-room basis are not available for classrooms and other key spaces. We present an overview of approaches for measuring ventilation along with their advantages and disadvantages. We also present data from recent case studies for a variety of institutions across the United States, with various building ages, types, locations, and climates, highlighting their commonalities and differences, and examples of the use of this data to support decision making.
Environmental Science & Technology, 2019
Journal of Exposure Science & Environmental Epidemiology, 2019
Previous research has found increased home ventilation, which may affect health by altering the c... more Previous research has found increased home ventilation, which may affect health by altering the composition of indoor air, is associated with improvement of respiratory health, but evidence linking home ventilation to objectively measured lung function is sparse. The Colorado Home Energy Efficiency and Respiratory health (CHEER) study, a cross-sectional study of low-income, urban, nonsmoking homes across the Northern Front Range of Colorado, USA, focused on elucidating this link. We used a multipoint depressurization blower door test to measure the air tightness of the homes and calculate the annual average infiltration rate (AAIR). Lung function tests were administered to eligible participants. We analyzed data from 253 participants in 187 homes with two or more acceptable spirometry tests. We used generalized estimating equations to model forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC), and FEV 1 /FVC z-scores as a function of AAIR. AAIRs ranged from 0.10 to 1.98 air changes per hour. Mean z-scores for FEV 1 , FVC, and FEV 1 /FVC were -0.57, 0.32, and -0.43, respectively. AAIR was positively associated with increased FEV 1 /FVC z-scores, such that a 1-unit change in AAIR corresponded to a half of a standard deviation in lung function (β = 0.51, CI: 0.02-0.99). These associations were strongest for healthy populations and weaker for those with asthma and asthma-like symptoms. AAIR was not associated with FEV 1 or FVC. Our study is the first in the United States to link home ventilation by infiltration to objectively measured lung function in low-income, urban households.
International Journal of Environmental Research and Public Health, 2019
Indoor and outdoor number concentrations of fine particulate matter (PM2.5), black carbon (BC), c... more Indoor and outdoor number concentrations of fine particulate matter (PM2.5), black carbon (BC), carbon monoxide (CO), and nitrogen dioxide (NO2) were monitored continuously for two to seven days in 28 low-income homes in Denver, Colorado, during the 2016 and 2017 wildfire seasons. In the absence of indoor sources, all outdoor pollutant concentrations were higher than indoors except for CO. Results showed that long-range wildfire plumes elevated median indoor PM2.5 concentrations by up to 4.6 times higher than outdoors. BC, CO, and NO2 mass concentrations were higher indoors in homes closer to roadways compared to those further away. Four of the homes with mechanical ventilation systems had 18% higher indoor/outdoor (I/O) ratios of PM2.5 and 4% higher I/O ratios of BC compared to other homes. Homes with exhaust stove hoods had PM2.5 I/O ratios 49% less than the homes with recirculating hoods and 55% less than the homes with no stove hoods installed. Homes with windows open for more t...
Environmental Science & Technology Letters, 2019
The lifetime of alkylperoxy radicals (RO 2 ) formed in the oxidation of volatile organic compound... more The lifetime of alkylperoxy radicals (RO 2 ) formed in the oxidation of volatile organic compounds (VOCs) is a key determinant of reaction mechanisms and products. When RO 2 • radical lifetimes are long, autoxidation reactions can form highly oxidized multifunctional compounds (HOMs) that are efficient at forming secondary organic aerosol (SOA). We measured the formation of HOMs resulting from the O 3 -initiated autoxidation of limonene emitted inside the University of Colorado Art Museum. Conditions inside the museum favored autoxidation for most of the 6-week study, indicating that autoxidation is prevalent indoors in the absence of an indoor combustion source of nitrogen oxide (NO). A box model of the museum was used with measurements of VOCs, O 3 , and NO x and air exchange to estimate HOM and SOA yields and to model the limonene oxidation rate. The HOM molar yield of 11% agrees well with the results of laboratory studies of limonene autoxidation, and the SOA mass yield of 47 ± 8% indicates that limonene autoxidation efficiently forms SOA indoors.
Sustainability, 2019
We studied 226 low-income households as a part of the Colorado Home Energy Efficiency and Respira... more We studied 226 low-income households as a part of the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study to investigate the relationship between energy-efficiency retrofits (EERs) specific to air sealing of residential building envelopes, annual average infiltration rates (AAIR), and qualitative indicators of “healthy” homes. Blower door tests quantified the leakage area in each home, which was used to estimate the AAIR. Walk-through inspections were used to record observations of air-sealing retrofits conducted as part of Colorado’s Weatherization Assistance Program and indirect indicators of poor indoor environmental quality (IEQ) in the homes, such as visible mold or stains, visible dust on hard surfaces, vapor condensation on windows, dampness, and perceived air quality. Results showed that building characteristics like age and volume affected AAIR more significantly than air-sealing EERs. Among the air-sealing EERs, homes with the air-handler ductwork sealed a...
Environmental Science & Technology, 2019
This document is 12 pages long and includes descriptions of the calibration procedures employed i... more This document is 12 pages long and includes descriptions of the calibration procedures employed in this study, descriptions of how the museum model was initialized, description of why recirculation fractions were presented in the text instead of deposition rate constants (Figure ), a table of variables and mathematical expressions used in the text (Table ), a table of reactions included in the model of the museum (Table ), tables of emission events (Tables ), and comparison of measured pollutant levels to published standards (Table ).
International Journal of Environmental Research and Public Health, 2019
Consensus is growing on the need to investigate the joint impact of neighborhood-level social fac... more Consensus is growing on the need to investigate the joint impact of neighborhood-level social factors and environmental hazards on respiratory health. This study used latent profile analysis (LPA) to empirically identify distinct neighborhood subtypes according to a clustering of social factors and environmental hazards, and to examine whether those subtypes are associated with lung function. The study included 182 low-income participants who were enrolled in the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study during the years 2015–2017. Distinct neighborhood typologies were identified based on analyses of 632 census tracts in the Denver-Metro and Front Range area of Colorado; neighborhood characteristics used to identify typologies included green space, traffic-related air pollution, violent and property crime, racial/ethnic composition, and socioeconomic status (SES). Generalized estimating equations were used to examine the association between neighborhood ty...
Building and Environment, 2018
Low-energy home design is becoming more common in new and retrofitted homes, and energy-efficient... more Low-energy home design is becoming more common in new and retrofitted homes, and energy-efficient designs often sell at a premium . Efficiency measures, like tightening the building envelope saves energy, but can impact the indoor air quality (IAQ). We monitored the IAQ of nine tightly constructed homes, one tightly constructed public library, and one conventionally constructed home, and performed a repeatable cooking activity to observe the impact of the fine particulate matter (PM2.5) emissions. We compared PM2.5 concentrations from the cooking activity while operating the mechanical ventilation systems at default rates (~0.1-0.3 h -1 ) and in a temporary boost mode (~0.3-0.8 h -1 ). We also measured the concentrations of total volatile organic compounds (TVOCs), formaldehyde, radon, and bedroom carbon dioxide (CO2) levels. Results show that PM2.5 concentrations are generally low indoors, but cooking drastically increases concentrations, which are slow to decay. No significant difference was found between operating the ventilators at standard rates and utilizing the temporary boost. Completely-mixed flow reactor models of select homes show that installing and using a directly-exhausting range hood can reduce peak PM2.5 concentrations by 75% or more. Current ventilation practices in these buildings may not be adequate for these common activities. Formaldehyde was above the California Office of Environmental Health Hazard Assessment (OEHHA) chronic limit of 9 µg/m 3 in all tight buildings with a median concentration of 30 µg/m 3 . CO2 levels in bedrooms exceeded 1000 ppm in six homes, indicating that bedroom ventilation practices are not consistent nor adequate.
Environmental science & technology, Jan 6, 2018
Diverse bacterial and fungal communities inhabit human-occupied buildings and circulate in indoor... more Diverse bacterial and fungal communities inhabit human-occupied buildings and circulate in indoor air; however, viral diversity in these man-made environments remains largely unknown. Here we investigated DNA and RNA viruses circulating in the air of 12 university dormitory rooms by analyzing dust accumulated over a one-year period on heating, ventilation, and air conditioning (HVAC) filters. A metagenomic sequencing approach was used to determine the identity and diversity of viral particles extracted from the HVAC filters. We detected a broad diversity of viruses associated with a range of hosts, including animals, arthropods, bacteria, fungi, humans, plants, and protists, suggesting that disparate organisms can contribute to indoor airborne viral communities. Viral community composition and the distribution of human-infecting papillomaviruses and polyomaviruses were distinct in the different dormitory rooms, indicating that airborne viral communities are variable in human-occupie...
Building and Environment, 2016
Cooling coil surfaces within building ventilation systems are ideal sites for biofilm formation d... more Cooling coil surfaces within building ventilation systems are ideal sites for biofilm formation due to the presence of adequate nutrients (deposited particles) and moisture (condensate). In this study, a heating, ventilation, and air-conditioning (HVAC) test apparatus was built consisting of two parallel ducts, each with its own cooling coil. One coil was exposed to ultraviolet germicidal coil cleaning (UVG-CC) while the other was the comparison control to investigate the impact of UVG-CC on surface microbial loading and bacterial attachment. Surface samples were collected by swabbing a uniform area of coil surface and airborne samples were collected isokinetically with sterile funnel filters. All samples were quantified via direct epifluorescent microscopy. Prior to irradiating, higher concentrations of surface microbial loading were found on the downstream side of both cooling coils under condensing conditions. Conversely, under dry surface conditions with downstream UV irradiance, surface concentrations were higher upstream. UVG-CC (at an average 200 uW/cm 2 on the coil surface) reduced surface microbial loading by 55% on average during condensing conditions and inhibited bacterial attachment causing clusters of bacterial matter to become airborne downstream of the cooling coil. Additionally, it was found that desiccation also inhibited surface microbial loading and yielded cluster detachment but to a lesser degree than UVG-CC treatment.
International Journal of Environmental Research and Public Health, 2017
The objectives of this study were to measure levels of particulate matter (PM) in mechanically ve... more The objectives of this study were to measure levels of particulate matter (PM) in mechanically ventilated buildings and to improve understanding of filtration requirements to reduce exposure. With the use of an Ultra High Sensitivity Aerosol Spectrometer and an Aerodyne Mass Spectrometer, ultrafine (0.055-0.1 µm) and fine (0.1-0.7 µm) indoor and outdoor PM was measured as a function of time in an office, a university building, and two elementary schools. Indoor particle levels were highly correlated with outdoor levels. Indoor and outdoor number concentrations in Denver were higher than those in Boulder, with the highest number concentrations occurring during summer and fall. The ratio of indoor-to-outdoor (I/O) PM was weakly but positively correlated with the amount of ventilation provided to the indoor environment, did not vary much with particle size (ranged between 0.48 and 0.63 for the entire size range), and was similar for each period of the week (weekend vs. weekday, night vs. day). Regression analyses showed that ultrafine indoor PM baseline concentrations were higher at night from nighttime infiltration. A lag time was observed between outdoor and indoor measurements. Weekday days had the shortest lag time of 11 min, and weekend nighttime lags when the HVAC was not in use were 50 to 148 min. Indoor-outdoor PM concentration plots showed ultrafine PM was more correlated compared to fine, and especially when the HVAC system was on. Finally, AMS data showed that most of the PM was organic, with occasional nitrate events occurring outdoors. During nitrate events, there were less indoor particles detected, indicating a loss of particulate phase nitrate. The results from this study show that improved filtration is warranted in mechanically ventilated buildings, particularly for ultrafine particles, and that nighttime infiltration is significant depending on the building design.
Building and Environment, 2016
Buildings represent habitats for microorganisms that can have direct or indirect effects on the q... more Buildings represent habitats for microorganisms that can have direct or indirect effects on the quality of our living spaces, health, and well-being. Over the last ten years, new research has employed sophisticated tools, including DNA sequencing-based approaches, to study microbes found in buildings and the overall built environment. These investigations have catalyzed new insights into and questions about the microbes that surround us in our daily lives. The emergence of the "microbiology of the built environment" field has required bridging disciplines, including microbiology, ecology, building science, architecture, and engineering. Early insights have included a fuller characterization of sources of microbes within buildings, important processes that structure the distributions and abundances of microbes, and a greater appreciation of the role that occupants can have on indoor microbiology. This ongoing work has also demonstrated that traditional culture-and microscopy-based approaches for studying microbiology vastly underestimate the types and quantity of microbes present in environmental samples. We offer ten questions that highlight important lessons learned regarding the microbiology of buildings and suggest future areas of investigation.