This grant supports research by atmospheric chemist Allen Goldstein and environmental engineer William Nazaroff to examine the processes controlling abundance, sources, and fates of organic chemicals indoors. The work will focus on the roles of human occupants, emissions from the building and its contents, and the intrusion of outdoor pollutants as agents influencing indoor air chemistry. In a series of experiments, Goldstein and Nazaroff will characterize organic compound composition of the air in residential spaces, cataloging the relative abundance of volatile (VOC), intermediate volatile (IVOC), and semivolatile (SVOC) organic compounds in both the gas and particle phases, and to compare this composition with outdoor air. They will then analyze how organic compound composition changes across various dimensions: by time, by location inside the residence, and by human occupancy. Their methods will enable them to apportion indoor air organics into major source categories: building fabric and contents, occupants and activities, and outdoor air, with the ultimate objective of understanding the role of emissions influencing indoor air chemistry. This work will advance the state of knowledge regarding the contributions of humans, human activities, surface interactions, and oxidation processes influencing indoor air composition in residences. This new knowledge will be shared through peer-reviewed publications and presentations at conferences and meetings. At least three students will be trained.

This grant funds research by University of Toronto chemist Jonathan Abbatt, who is trying to forge better kinetic and mechanistic understandings of multiphase chemistry occurring indoors. Abbatt’s work focuses on the oxidation kinetics in both the condensed-phase and volatile products and the effects of oxidation on the gas-aerosol-surface partitioning of semivolatile species. Grant funds will allow Abbatt to use state-of-the-art mass spectrometric techniques in the laboratory to address the multiphase chemistry of a range of indoor surface materials. Abbatt will document what gas-phase and condensed-phase products arise from ozonolysis of the components of skin and cooking oils, characterize the oxidation kinetics and mechanisms of indoor combustion materials, such as cigarette and cannabis smoke, determine the fate of HOCl, an important oxidant released by bleach washing, and investigate how surface oxidation affects the partitioning of surface-sorbed species. Abbatt and his team will generate important new insights into indoor chemistry. This new knowledge will be shared through peer-reviewed publications and presentations at conferences and meetings. At least two postdoctoral researchers and three students will be trained.

This grant funds a research project by Rachel Adams, research scientist at the University of California, Berkeley, to expand our understanding of how microorganisms shape the chemistry of indoor environments. Adams and colleagues will undertake a series of controlled chamber experiments to identify the boundaries of microbial production of chemical volatile organic compounds due to humidity on various surfaces fundamental to homes, including drywall, carpets, and wood. The team also plans to investigate the relative importance of growth substrate, including the dust matrix in which most household environmental microbes are embedded, and, by varying substrate and inoculum in a controlled manner, of microbial taxonomic identity. In addition to creating a more thorough inventory of MVOCs, these research activities will determine how changing environmental conditions underlie the microbial processes that determine chemical emissions. This project will result in new knowledge about microbially mediated processes that impact the chemistry of indoor spaces. The results will be shared through peer-reviewed publications and presentations at meetings and workshops. Two undergraduate, one master’s and one Ph.D. student will be trained.

This grant funds a research project by Jonathan Williams, research group leader, Max Planck Institute for Chemistry, in collaboration with Pawel Wargocki, associate professor at the International Centre for Indoor Environment and Energy at the Technical University of Denmark (DTU) that will investigate the impact of exhaled and dermally emitted human emissions in climate chambers under different conditions of clothing, temperature, relative humidity, and ozone. Volatile organic compound (VOCs) emissions will be characterized by Williams and his team using state-of-the-art proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS). Novel analytical techniques developed by Williams for outdoor use will be used to measure OH reactivity of the human emissions, which will account for any “missing” emissions.   Twin stainless steel climate chambers located at the DTU will be used to measure how human emissions vary between cold and dry versus hot and humid conditions, and how human emissions change with the presence of ozone and with different clothing. Williams’ experiments will allow for the isolation of exhaled versus dermally emitted bio effluents and the contribution if each to OH reactivity will be separately measured. These measurements will allow Williams to make the first ever OH reactivity–based budget of the human-influenced indoor environment and will reveal what proportion of human emissions currently can be measured and what proportion is “missing.” This new knowledge will be shared through peer-reviewed publications and conference presentations. At least one postdoctoral fellow will be trained.

This grant supports research by Andrew Ault, Assistant Professor of Environmental Health Sciences and Chemistry at the University of Michigan, to examine the pH of indoor surfaces and answer two related questions: “What are the properties of aqueous films on indoor surfaces?” and, more specifically, “What is the pH of surface water layers indoors?” To this end, Ault will determine the properties of water layers and range of pH values present on the surface of six common building materials—glass, concrete, drywall, latex painted drywall, carpet, and wood—as well as six associated proxy model systems—silicon dioxide, quicklime (cement)/limestone (aggregate), gypsum, synthetic rubber, nylon, and cellulose. Materials will be studied before and after aging for six months in a residential environment. The project will determine the water and water layer properties (including island formation, structured water, and accessible water fraction) as a function of relative humidity (RH) for different materials, model systems, and aged samples. The project also will reveal the intrinsic pH of the samples as a function of RH, as well as the differences in pH for aged samples across spatial scales ranging from nano to macro. Last, Ault and his team will determine the sensitivity of pH to gaseous acids and bases and acidic aerosols and associated kinetics.

Funds from this grant support a project by Tara S. Kahan, Associate Professor of Chemistry at the University of Saskatchewan, in collaboration with Jianshun Zhang, Professor of Mechanical Engineering, at Syracuse University to examine indoor photon fluxes and determine concentrations, sources, and sinks of indoor oxidants and oxidant precursors. The project will combine laboratory, field, and chamber studies to better understand oxidizing capacity from emerging precursors in residences. Kahan will investigate the sources and sinks of indoor oxidants by measuring oxidant precursor concentrations in three residences, measuring indoor photon fluxes under a range of conditions, and determining oxidant concentrations via chamber experiments that simulate indoor conditions. The results will be shared through peer-reviewed publications in journals such as Environmental Sciences & Technology and Indoor Air. The team also plans to make presentations at conferences and meetings, including meetings of the International Society of Indoor Air Quality and Climate and the American Association for Aerosol Research. One postdoctoral scholar, three graduate students, and one undergraduate student will be trained on this project.