William W. Nazaroff's research while affiliated with University of California, Berkeley and other places

Publications (378)

Article
Full-text available
Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (Hr) and risk parameter (H). They combine the...
Article
Knowledge about person-to-person transmission of SARS-CoV-2 is reviewed, emphasizing three components: emission of virus-containing particles and drops from infectious persons; transport and fate of such emissions indoors; and inhalation of viral particles by susceptible persons. Emissions are usefully clustered into three groups: small particles (...
Article
Because people spend most of their time indoors, much of their exposure to ozone occurs in buildings, which are partially protective against outdoor ozone. Measurements in approximately 2000 indoor environments (residences, schools, and offices) show a central tendency for average indoor ozone concentration of 4-6 ppb and an indoor to outdoor conce...
Article
Particle emissions from cooking are a major contributor to residential indoor air pollution and could also contribute to ambient concentrations. An important constituent of these emissions is light-absorbing carbon, including black carbon (BC) and brown carbon (BrC). This work characterizes the contributions of indoor and outdoor sources of BC and...
Article
Quantifying speciated concentrations and emissions of volatile organic compounds (VOCs) is critical to understanding the processes that control indoor VOC dynamics, airborne chemistry, and human exposures. Here, we present source strength profiles from the HOMEChem study, quantifying speciated VOC emissions from scripted experiments (with multiple...
Article
Looking further than COVID-19, some of the key messages: 1. We from now on should include the risk of indoor respiratory infections in our design of buildings and its ventilation. 2. Treat the air quality in a similar way as we are used to for water and food quality. 3. ‘Visualize’ the air quality by displaying monitoring values (e.g. CO2 concentra...
Preprint
Full-text available
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 maint...
Article
Significance It has been suggested that indoor exposure to ozone oxidation products contributes materially to the apparent associations between outdoor ozone concentration and morbidity and mortality. Our current understanding of indoor ozone chemistry derives mainly from studies with test surfaces under controlled conditions. Little is known about...
Article
Full-text available
The Covid-19 pandemic has caused untold disruption and enhanced mortality rates around the world. Understanding the mechanisms for transmission of SARS-CoV-2 is key to preventing further spread but there is confusion over the meaning of “airborne” whenever transmission is discussed. Scientific ambivalence originates from evidence published many yea...
Article
Air‐change rate is an important parameter influencing residential air quality. This article critically assesses the state of knowledge regarding residential air‐change rates, emphasizing periods of normal occupancy. Cumulatively, about 40 prior studies have measured air‐change rates in approximately 10,000 homes using tracer gases, including metabo...
Article
During the 2020 COVID-19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID-19 and two died. Transmission by the aerosol r...
Article
Inhalation of particulate matter is associated with adverse health outcomes. The fluorescent portion of supermicron particulate matter has been used as a proxy for bioaerosols.The sources and emission rates of fluorescent particles in residential environments are not wellunderstood. Using an ultraviolet aerodynamic particle sizer (UVAPS), emissions...
Preprint
Full-text available
During the 2020 COVID-19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a regular weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID-19 and two died. Transmission by the a...
Article
Full-text available
During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and...
Article
Full-text available
It is important to improve our understanding of exposure to particulate matter (PM) in residences because of associated health risks. The HOMEChem campaign was conducted to investigate indoor chemistry in a manufactured test house during prescribed everyday activities, such as cooking, cleaning, and opening doors and windows. This paper focuses on...
Article
Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate die...
Article
Numerous acids and bases influence indoor air quality. The most abundant of these species are CO2 (acidic) and NH3 (basic); building occupants are important sources. Other prominent inorganic acids are HNO3, HONO, SO2, H2SO4, HCl and HOCl. Prominent organic acids include formic, acetic and lactic; nicotine is a noteworthy organic base. Sources of N...
Article
Full-text available
Human health is affected by indoor air quality. One distinctive aspect of the indoor environment is its very large surface area that acts as a poorly characterized sink and source of gas-phase chemicals. In this work, air-surface interactions of 19 common indoor air contaminants with diverse properties and sources were monitored in a house using fa...
Article
Previous work examining the condensed-phase products of squalene particle ozonolysis found that an increase in water vapor concentration led to lower concentrations of secondary ozonides, increased concentrations of carbonyls, and smaller particle diameter, suggesting that water changes the fate of the Criegee intermediate. To determine if this vol...
Article
Full-text available
The House Observations of Microbial and Environmental Chemistry (HOMEChem) study is a collaborative field investigation designed to probe how everyday activities influence the emissions, chemical transformations and removal of trace gases and particles in indoor air. Sequential and layered experiments in a research house included cooking, cleaning,...
Article
Phthalate esters, commonly used as plasticizers, can be found indoors in the gas phase, in airborne particulate matter, in dust, and on surfaces. The dynamic behavior of phthalates indoors is not fully understood. In this study, time-resolved measurements of airborne phthalate concentrations and associated gas-particle partitioning data were acquir...
Article
Full-text available
A growing body of evidence identifies clothing as an important mediator of human exposure to chemicals and particles, which may have public health significance. This paper reviews and critically assesses the state of knowledge regarding how clothing, during wear, influences exposure to molecular chemicals, abiotic particles, and biotic particles, i...
Article
We investigate source characteristics and emission dynamics of volatile organic compounds (VOCs) in a single‐family house in California utilizing time‐ and space‐resolved measurements. About 200 VOC signals, corresponding to more than 200 species, were measured during eight weeks in summer and five in winter. Spatially resolved measurements, along...
Article
Semivolatile organic compounds (SVOCs) emitted from building materials, consumer products, and occupant activities alter the composition of air in residences where people spend most of their time. Exposures to specific SVOCs potentially pose risks to human health. However, little is known about the chemical complexity, total burden, and dynamic beh...
Article
Full-text available
Although defined more broadly, exposure science has mainly focused on exposures to environmental chemicals and related stressors, such as airborne particulate matter. There is an opportunity for exposure science to contribute more substantially to improving public health by devoting more attention to microorganisms as key stressors and agents in ex...
Article
We present direct indoor measurements of nitrate (NO3) and dinitrogen pentoxide (N2O5) produced from combustion cooking emissions in a residential kitchen. When indoor ozone (O3) concentrations were low (~4 ppbv), nitric oxide (NO) emitted from gas-stove combustion suppressed NO3 formation. However, at moderate O3 levels (~40 ppbv), measured NO3 co...
Data
Sampling activity schematic diagram, α and β diversity analysis. (XLSX)
Data
DNA conservation experiments for AHU filters. (DOCX)
Data
Report on PCR inhibition check for AHU filter samples. (DOCX)
Article
Full-text available
Introduction Ventilation system filters process recirculated indoor air along with outdoor air. This function inspires the idea of using the filter as an indoor bioaerosol sampler. While promising, there remains a need to investigate several factors that could limit the accuracy of such a sampling approach. Among the important factors are the dynam...
Article
Building ventilation rates and indoor airflow conditions influence occupants’ exposure to indoor air pollutants. By making time‐ and space‐resolved measurement of three inert tracers steadily released in a single‐family house in California for eight weeks in summer and five weeks in winter, the present study quantifies the air change rate of the li...
Article
Residences represent an important site for bioaerosol exposure. We studied bioaerosol concentrations, emissions, and exposures in a single‐family residence in northern California with two occupants using real‐time instrumentation during two monitoring campaigns (eight weeks during August‐October 2016 and five weeks during January‐March 2017). Time‐...
Article
Full-text available
Strong evidence suggests that clothing serves as a reservoir of chemical pollutants and particles, including bioaerosols, which may have health significance. However, little is known about the role that clothing may play as a transport vector for inhaled airborne particles. Here we contribute toward bridging the knowledge gap by conducting experime...
Data
Indoor environment descriptions, air flow speed measurements, occupancy estimates, rarefaction curve, principal coordinate analysis and diversity indices. (XLSX)
Article
Full-text available
Introduction Biological particles deposit on air handling system filters as they process air. This study reports and interprets abundance and diversity information regarding biomass accumulation on ordinarily used filters acquired from several locations in a university environment. Methods DNA-based analysis was applied both to quantify (via DNA f...
Article
Personal care products (PCP) might be a source of ultrafine particle exposure for users owing to the reaction of ozone with terpene ingredients. The near-person emissions associated with PCP may contribute to exposures that would not be properly accounted for with indoor microenvironmental measurements. To better understand this issue, screening ex...
Article
Full-text available
Background Microorganisms influence the chemical milieu of their environment, and chemical metabolites can affect ecological processes. In built environments, where people spend the majority of their time, very little is known about how surface-borne microorganisms influence the chemistry of the indoor spaces. Here, we applied multidisciplinary app...
Article
Elevated exposure to airborne particulate matter is linked to deleterious health and well-being outcomes. Exposure assessment can be improved through enhanced understanding of source-receptor relationships, for example as expressed in the inhalation intake fraction metric. This study provides new knowledge about how inhalation intake of airborne pa...
Article
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 in...
Article
Full-text available
Draft is unwanted local convective cooling. The draft risk model of Fanger et al. (Energy and Buildings 12, 21-39, 1988) estimates the percentage of people dissatisfied with air movement due to overcooling at the neck. There is no model for predicting draft at ankles, which is more relevant to stratified air distribution systems such as underfloor...
Article
Inhalation exposure to elevated particulate matter levels is correlated with deleterious health and well-being outcomes. Despite growing evidence that identifies humans as sources of coarse airborne particles, the extent to which personal exposures are influenced by particle releases near occupants is unknown. In a controlled chamber, we monitored...
Article
Full-text available
Research on the sources of indoor airborne chemicals has traditionally focused on outdoor air, building materials, furnishings, and activities such as smoking, cooking and cleaning. Relatively little research has examined the direct role of occupant emissions, even though this source clearly contributes to indoor volatile organic compounds (VOCs) a...
Article
Indoor carbon dioxide (CO2) levels serve as an indicator of ventilation sufficiency in relation to metabolic effluents. Recent evidence suggests that elevated CO2 exposure (with or without other bioeffluents) may cause adverse cognitive effects. In shelter-in-place (SIP) facilities, indoor CO2 levels may become particularly elevated. This study eva...
Article
Utilizing the ultraviolet-light induced fluorescence (UV-LIF) measurement technique as embodied in the Waveband-Integrated Bioaerosol Sensor (WIBS-4A), we evaluated the fluorescent particle emissions associated with human shedding while walking in a chamber. The mean emission rates of supermicron (1-10 μm) fluorescent particles was in the range 6.8...
Article
Draft is defined as unwanted local convective cooling. Existing draft risk models, developed in the 1970s, focus on air movement at the neck. The purpose of the present study is to experimentally evaluate ankle draft risk for women with uncovered ankles because of current widespread use of displacement ventilation and underfloor air distribution sy...
Article
Full-text available
In a warm and humid climate, increasing the temperature setpoint offers considerable energy benefits with low first costs. Elevated air movement generated by a personally controlled fan can compensate for the negative effects caused by an increased temperature setpoint. Fifty-six tropically acclimatized persons in common Singaporean office attire (...
Article
This study is concerned with the role of a fin-and-tube heat exchanger in modifying microbial indoor air quality. Specifically, depositional losses of ambient bioaerosols and particles onto dry (not cooled) and wet (cool) coil surfaces were measured for different airspeeds passing through the test coil. Total, bacterial and fungal DNA concentration...
Article
Full-text available
Infants in neonatal intensive care units (NICUs) are vulnerable to environmental stressors. Few studies have reported on airborne particles in the NICU environment. During a four-day pilot study in a private-style NICU, we measured size-resolved particle number (PN) concentrations with 1-min resolution. The investigation included simultaneous sampl...
Data
Comparison of the real-time 1-h mean concentrations of size-resolved particles in the (a) baby room and the nurses’ station; and (b) baby room and the hallway. Time series are shown for 10 sampling days that correspond to B3. The solid line designates particle levels in the baby room, while the shaded area illustrates concentrations at the nurses’...
Data
Adjustment factors obtained from optical particle counter (OPC) side-by-side tests with a reference instrument OPC3.1 (DOCX)
Data
Time series (at 5-min resolution) of temperature, relative humidity, TPN and PM10 in a baby room, showing influence of the HVAC filtration system maintenance. These results are based on an analysis of data from 11 February, when filter change-out procedure began at 6:00 AM and lasted for 2.9 hours, as delimited by vertical dashed lines. (TIF)
Data
Particle number and CO2 data acquisition success rate in the hallway and across all baby rooms. The data yield also includes recordings from the nurses’ station and during the HVAC system maintenance that were not included in Table 1. (TIF)
Data
Coefficient of determination for the linear correlation between concentrations in two simultaneously sampled baby rooms (B10 and B11) for a nine-day period. The results include 5-min means of small (0.3–0.5 μm) and large (>10 μm) particle number concentrations, and CO2 levels. (TIF)
Data
Size-resolved particle number concentrations measured in the baby rooms and hallway. The results include data from nurses’ station (for B1, B2 and the first week of B3) and HVAC filter maintenance (no post-processing). (DOCX)
Data
Comparison of individual contributions to the total particle number concentration (TPN) in the baby rooms from three sources: Indoor (within-room) emissions, indoor (near-room) emissions, and outdoors. Individual source contributions to the total TPN were calculated in the same fashion as explained in relation to Fig 6. (TIF)
Article
Full-text available
Premature infants in neonatal intensive care units (NICUs) have underdeveloped immune systems, making them susceptible to adverse health consequences from air pollutant exposure. Little is known about the sources of indoor airborne particles that contribute to the exposure of premature infants in the NICU environment. In this study, we monitored th...
Data
Nurses’ station and HVAC filter maintenance. (DOCX)