Grantee Research Project Results
Final Report: Indoor Exposure to Pollutants Associated with Oxidative Chemistry: Field Studies and Window-Opening Behavior
EPA Grant Number: R835751Title: Indoor Exposure to Pollutants Associated with Oxidative Chemistry: Field Studies and Window-Opening Behavior
Investigators: Morrison, Glenn C , Williams, Brent , Ercal, Nuran
Institution: Missouri University of Science and Technology , Washington University
EPA Project Officer: Chung, Serena
Project Period: November 1, 2014 through October 31, 2017 (Extended to October 31, 2019)
Project Amount: $999,999
RFA: Indoor Air and Climate Change (2014) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air
Objective:
This research furthers scientific understanding of indoor chemistry and the associated human exposure to chemical products, as it is influenced by natural ventilation, a key adaptation associated with climate change. Specific objectives were to
- Quantify chemical precursors and chemical products associated with infiltration of photochemical oxidants from ambient air in residential settings,
- Evaluate the influence of natural ventilation on the composition of indoor pollutants and indoor chemistry, and
- Quantify contemporary window‐ and door‐opening behavior in residential settings and its relationship to region, local climate, construction type and other site‐specific phenomena.
- Integrate information derived from activities related to objectives (1) through (3), as well as existing information on buildings to provide inputs for air chemistry modeling
Summary/Accomplishments (Outputs/Outcomes):
Both Objectives (1) and (2) were met through intensive field studies of the composition of indoor and outdoor air in residential buildings. Two field studies were performed during this project.
Field study 1 Air Composition and Reactivity from Outdoor aNd Indoor Mixing (ACRONIM-1)
1) This study took place in the summer of 2016 at the site of a single-family, unoccupied home in suburban St. Louis Missouri. The field study included continuous and semi-continuous measurements of the concentration of many gas-phase chemicals as well as the composition, size and mass concentrations of particulate matter. The field study included periods in which windows were open and closed, to investigate how the pollutant composition changes as the result of ventilation dilution, changes in indoor emissions and infiltration of outdoor reactants such as ozone. This study resulted in one scientific journal article to date; this article focused on the results of particulate composition from a Thermal desorption Aerosol Gas Chromatograph (TAG), but also included measures of environmental parameters, air exchange rates, volatile organic compounds (VOCs), ozone and others. Data continues to be analyzed, especially in relationship to the second field study and other papers are in development.
Four distinct chemical and physical processes resulting from changes in indoor natural ventilation were identified by combining the results of Thermal desorption Aerosol Gas Chromatograph (TAG), air exchange rates, volatile organic compounds (VOCs) and ozone measurements. These were 1) indoor to outdoor exchange of pollutants, 2) dilution of indoor species, 3) enhanced emissions of indoor species (especially semi-volatile organic compounds) and 4) formation of indoor species by oxidation. Depletion of species by oxidation was explored, but no significant reductions were observed which could be due to competing processes of dilution and ozone removal by surfaces or low time-resolution of the measurements (4-h time intervals). Although low time resolutions for chemical measurements challenged our investigation of the rapidly- changing indoor environment, thein-situcollection and molecular-level analysis provided by the TAG improves upon techniques used to investigate indoor organic aerosol molecular composition from previous studies.
The findings presented in this work suggest that the overall indoor air quality impacts of natural ventilation depend on multiple factors, including indoor pollutant abundances (e.g., high gas-phase semi-volatile or intermediate volatility organic compound (S/IVOC) abundances due to offgassing of building materials and personal care products), outdoor pollutant abundances (e.g., outdoor particle concentrations and composition, O3 concentrations), and air exchange rates. The contributions of each process will therefore vary between buildings and their surrounding environments, necessitating future investigation across a variety of test homes in a variety of locations. Additionally, human occupancy presents additional challenges to assessing natural ventilation impacts on indoor air quality. For example, while opening windows can mitigate indoor pollutant concentrations from activities like food cooking or cleaning, infiltrating O3 can drive oxidation of these particles and gases to form secondary products, and clothing and skin can drive formation of secondary particles and gases through surface-mediated ozonation. The influence of human occupants is therefore critical to understanding natural ventilation impacts on the indoor environment and will therefore be explored in future work.
Field study 2 Air Composition and Reactivity from Outdoor aNd Indoor Mixing (ACRONIM-2)
2) This study took place in the summer of 2018 at the site of a different single-family, unoccupied home in suburban St. Louis Missouri. Like ACRONIM-1, this field study included continuous and semi- continuous measurements of the concentration of many gas-phase chemicals as well as the composition, size and mass concentrations of particulate matter. Between 2016 and 2018, measurement capacity was enhanced with an updated TAG system, updated VOC measurement techniques and a newly constructed system for continuously measuring Reactive Oxygen Species (ROS) in particles. As in 2016, the 2018 field study also included periods in which windows were open and closed, to investigate how the pollutant composition changes as the result of ventilation dilution, changes in indoor emissions and infiltration of outdoor reactants such as ozone. Data continues to be analyzed from this study and several journal articles are in preparation.
Results from our second residential field study mirror that of the first one, with some exceptions. In general, window opening increases air exchange rates and entry of outdoor photochemical oxidants. Window opening dilutes many volatile species that are the results of primary emissions indoors. Infiltration of outdoor ozone increases the apparent emission rate of some species, like aldehydes, which reduces the effectiveness of window opening as a strategy to dilute indoor concentrations. Initial analysis of TAG results show uptake of indoor sourced SVOCs onto particles of outdoor origin, but the tendency for window opening to increase apparent emission
The rates of SVOCs observed in ACRONIM-1 was not as apparent in ACRONIM-2, which may be the result of lower air exchange rates when windows were open in ACRONIM-2.
ACRONIM-2 is the first time a real-time system has been used to simultaneously measure ROS in indoor and outdoor air. The indoor concentration of particle bound ROS appears to be fairly insensitive to air exchange rate, but for unknown reasons at this time. If these observations are supported by further studies, they suggest that buildings do not attenuate exposure to ROS in PM as much as they do other pollutants such as ozone or PM 2.5 If the indoor and outdoor concentrations of particulate ROS are about the same regardless of ventilation conditions, then as much as 90% of our total exposure could occur indoors. Measurement of the toxicity potential of indoor PM of outdoor origin remains a significant need.
National survey of window opening behavior
Objective (3) was addressed through a unique, nationwide survey of window opening behavior. This survey was deployed 12 times between April 2016 and June 2018 to collect over 3800 responses from individuals living within the contiguous 48 US states. The survey collected information regarding the frequency, extent, timing and motivations associated with opening windows and doors in residences. Demographic and geolocation information allowed for metadata such as income, race, building type, weather and region to be associated with survey results.
Averaged over all regions and seasons, about 44% of people in the continental US will open a window at least once a day. A large fraction of those that do open windows, open them for several hours a day, most commonly in the afternoon and in the bedroom, living room or kitchen. Window opening is strongly dependent on climate factors. Window opening frequency peaks at a mean temperature of about 18°C (64°F) and decreases as temperature rises or falls from that value. Individuals in the US southeast, are much less likely to open windows than those in other regions, even controlling for climate. Demographic factors that significantly influence window opening are race/ethnicity, income, home type, home ownership and the presence of air conditioning. There are regional differences in the importance of demographic factors; for example, gender is not significant in the northeast but does influence window opening in all other regions. Only in the northeast are income and home ownership important. When compared with window opening, door opening has similar associations with measured factors and follows similar, but not identical trends.
Reported here are only those data that have been analyzed. There are other questions that remain to be reviewed and placed in the context of region, climate and demographics.
Objective (4) was not directly addressed during this project although all data has been collected for that purpose. A future outcome will be to combine information from field studies and the national survey to improve predictive models of personal exposure to pollutants of indoor and outdoor origin. The data can also be used to make predictions about energy use and how future changes in regional demographics or climate may influence energy use or exposure.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
Other project views: | All 15 publications | 4 publications in selected types | All 4 journal articles |
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Eftekhari A, Fortenberry CF, Williams BJ, Walker MJ, Dang A, Pfaff A, Ercal N, Morrison GC. Continuous measurement of reactive oxygen species inside and outside of a residential house during summer. Indoor Air 2021 |
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Morrison G, Cagle J, Date G. A national survey of window-opening behavior in United States homes. INDOOR AIR 2022;32(1). |
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Sheu R, Fortenberry C, Walker M, Eltekhari A, Stonner C, Bakker A, Peccia J, Williams J, Morrison G, Williams B, Gentner D. Evaluating Indoor Air Chemical Diversity, Indoor-to-Outdoor Emissions, and Surface Reservoirs using High-Resolution Mass Spectrometry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021;55(15):10255-10267. |
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Fortenberry C, Walker M, Dang A, Loka A, Date G, Cysneiros de Carvalho K, Morrison G, Williams B. Analysis of indoor particles and gases and their evolution with natural ventilation. Indoor air 2019;29(5):761-779. |
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Supplemental Keywords:
indoor air quality, epidemiology, smog, house, experimentProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
- 2018 Progress Report
- 2017 Progress Report
- 2016 Progress Report
- 2015 Progress Report
- Original Abstract
4 journal articles for this project