One the most fascinating, important, but difficult-to-understand features of indoor environmental chemistry is how the human occupants of an indoor space shape the chemical processes taking place within it.  In response to this challenge, a group of European researchers led by Jonathan Williams at the Max Plank Institute for Chemistry came together in 2018 to study this issue.  Williams’s Indoor Chemical Emissions and Reactivity (ICHEAR) project designed a series of experiments set in twin stainless steel climate chambers that aimed to measure the chemicals emissions from human breath and skin across a variety of conditions.  ICHEAR set important baseline data about human emissions to the indoor environment and how those emissions vary depending on common environmental variables like room temperature, humidity, abient ozone levels, and the type of clothing being worn. This grant funds a second round of the ICHEAR experiments (known as ICHEAR2), allowing Williams and his co-investigator, Pawel Wargocki of the Technical University of Denmark, to build on their initial results.  In a new set of experiments using the same twin-climate-chamber design, Williams and Wargocki will probe how a new set of variables affect human emissions in indoor air, including exercise, hygiene (washing frequency, clothing), and deodorant and fragrance use. This experiments will inform how indoor emissions and chemistry associated with humans are altered by real-world lifestyle choices.

This grant provides three years of support to MOCCIE, the Modeling Consortium for Chemistry of Indoor Environments. Led by Nicola Carslaw of the University of York and Manabu Shiraiwa of UC Irvine, MOCCIE is a consortium of theoretical and experimental chemists, statisticians, computer scientists, and building experts devoted to creating high quality models of indoor chemical processes across various size and time scales. Over the next three years, MOCCIE researchers will use a variety of cutting edge techniques, including molecular dynamics simulations, kinetic process modeling, gas-phase chemistry and particle-phase modeling, thermodynamic modeling, and computational fluid dynamics in an attempt to develop  comprehensive, integrated physical-chemical models of indoor environmental chemical processes.  The models will include a detailed representation of gas-phase, particle-phase, and surface chemistry in indoor environments that simulates how occupants, indoor activities, and buildings influence indoor chemical processes. Model design will be driven by three fundamental questions. One, can we understand indoor chemical and physical processes well enough to predict them quantitatively with computer models? Two, what are the major uncertainties in these models? Three, what experiments or field measurements would improve those predictions or reduce those uncertainties? Findings will be shared through peer-reviewed publications and presentations at conferences and meetings, and the developed models will be made freely available through an easily accessible open access repository.

This grant funds an extended field experiment, Chemical Assessment of Surfaces and Air (CASA), that will bring together a dozen research groups from across the country to advance the state of understanding of indoor chemistry. Led by Delphine Farmer of Colorado State University and Marina Vance of UC Boulder, CASA will occur at  the Net-Zero Energy Residential Test Facility, a test house laboratory managed by the National Institute of Standards in Gaithersburg, Maryland. CASA will consist of a diverse series of experiments that revolve around disturbing a well-controlled, heavily-sensored, indoor environment in a variety of ways and observing how those disturbances affect the evolution of the chemical processes going on inside.  Questions for investigation involve how perturbations in indoor environmental conditions, such as temperature, relative humidity, and ventilation rate, affect indoor surface and air composition; how the introduction of novel molecules like ozone or volatile organic compounds influence the chemical transformations happening in the air and on surfaces; and how changes to the acidity, reactivity, or other properties of indoor surfaces like countertops and floors affect indoor chemical processes.  Grant funds will support the organization of CASA, coordination of the research teams, and associated data infrastructure and community-building activities aimed both at participating research groups and at connecting findings with the growing body of indoor chemistry research.  The project will result in at least 10 new peer-reviewed publications and 20 conference presentations, a more developed website with links to an accessible data archive, data analysis tutorials, a set of unified datasets, and a conference for study participants to discuss preliminary findings.

Polyfluoroalkyl substances (PFAS) are water-soluble organic (WSO) chemicals used industrial and consumer products, particularly those designed to be grease-resistant.  This includes non-stick cookware, stain resistant fabrics, indoor-outdoor carpeting, and longlasting cosmetics. However, several studies have show that human exposure to PSAS, may lead to a range of adverse health outcomes. Airborne exposure has not been, up to know, thought to be a primary vector for PFAS exposure, but in 2008, a study of PFAS by University of North Carolina chemist Barbara Turpin documented PFAS concentrations in both indoor and outdoor air, with preliminary results showing compounds existing in both environments, though with higher concentrations indoors. Funds from this grant support the continuation and extension of Turpin’s work, as she attempts to more rigoursly quantify the concentration, fate, and behavior of WSO compounds in indoor air with a focus on these substances.  Turpin’s workplan will pay special attention to the role surfaces play in determining PFAS concentration, including how surface composition and other factors, like its age or dampness, affect the absorption of airborn PFAS.  Research findings will be shared through peer-reviewed publications and presentations at national and international conferences, and three graduate students will be trained.

Surface-to-volume ratios are orders of magnitude larger indoors compared to outdoors. As a result, air-surface interactions play a significantly more important role in indoor chemistry than in typical atmospheric chemistry.  This grant provides ongoing support for the work of surface chemist Vikki Grassian of the University of California, San Diego to examine the fundamental chemistry of indoor surfaces. Using a variety of techniques, including X-ray photoelectron spectroscopy, vibrational spectroscopy, and atomic force microscopy, Grassian and her team will observe and analyze the interactions between gases and particles, on the one hand, and various surfaces commonly found indoors, on the other.  The team’s focus will be on better understanding the fundamental mechanisms of reaction chemistry, including oxidation reactions, surface reactions of chlorine-containing cleaning products, and nitrogen oxide chemistry that leads to the formation of nitrous acid. Grassian’s experiments have been designed with an eye toward ensuring collected data can be usefully integrated into existing models of indoor air chemistry.   This project will result in new knowledge on the fundamental chemistry that occurs on indoor surfaces and new data for input into indoor air quality models. The results will be shared through peer-reviewed publications and presentations at conferences and meetings, with at least two students and one postdoc being trained.  

This grant provides partial support to the National Academies of Sciences, Engineering, and Medicine (NASEM) for a consensus study on the research needs and implications of emerging indoor chemistry research.  NASEM will convene an ad hoc committee of scientific experts and leaders to examine the state-of-the-science regarding chemicals in indoor air. It will collect new findings about chemical reactions, sources of chemicals, and the abundance and distribution of chemical species indoors.  The committee will then examine how these new findings fit into existing scholarship about the link between chemical exposure, air quality, and human health. Based on this information, the report will contain consensus findings on the key implications of this scientific research, including potential near-term opportunities for incorporating what is known into practice, and will identify topics and issue areas where additional chemistry research will be most critical to understanding the chemical composition of indoor air and the consequences of adverse exposures. The report will also identify current methodological or technological barriers to advancing our understanding of indoor chemistry and areas where enhanced coordination or collaboration are necessary for continued progress.   Grant funds will support forming and convening the committee; at least one information-gathering workshop; and the composition, review, publication, and dissemination of the committee’s report.