Grantee Research Project Results
2022 Progress Report: Household Atmospheric Dynamics under Elevated Smoke (HADES): Holistic Evaluation of Interventions for Reducing Indoor Levels of Wildland Fire Emissions
EPA Grant Number: R840238Title: Household Atmospheric Dynamics under Elevated Smoke (HADES): Holistic Evaluation of Interventions for Reducing Indoor Levels of Wildland Fire Emissions
Investigators: Gall, Elliott T
Institution: Portland State University
EPA Project Officer: Chung, Serena
Project Period: September 1, 2021 through August 31, 2024
Project Period Covered by this Report: September 1, 2021 through August 31,2022
Project Amount: $547,899
RFA: Interventions and Communication Strategies to Reduce Health Risks of Wildland Fire Smoke Exposures (2021) RFA Text | Recipients Lists
Research Category: Early Career Awards , Air Quality and Air Toxics , Wildfires
Objective:
The Household Atmospheric Dynamics under Elevated Smoke (HADES) project consists of three research objectives that aim to inform our understanding of the transport, removal, and persistence of air pollution generated from wildland fires in indoor spaces. An overarching goal of the project is to enable critical evaluation of interventions that may reduce exposures to smoke indoors.
The first objective consists of a field study in Portland, OR, USA. Here, we will conduct experiments in real buildings to evaluate how changes to building envelopes and mechanical systems affect infiltration and persistence of smoke indoors. Next, in controlled laboratory studies, we will evaluate a wide variety of air cleaning systems. In this study, we will quantify clean air delivery rates (CADRs) under a variety of operating and environmental conditions for particles generated by a wildfire smoke proxy. In addition, we are evaluating if air cleaners can meaningfully remove gaseous organic compounds that are also elevated in smoke and potentially harmful to human health. Finally, we will develop a method to measure the accumulation of persistent organic pollutants on indoor surfaces due to indoor smoke. This study will focus on quantifying the magnitude and retention of polycyclic aromatic hydrocarbons on common indoor materials. Across these interconnected efforts, we aim to inform more accurate modeling of indoor spaces by providing parameterizations of transport and removal processes that are presently not well known. Improved modeling of indoor spaces during fire smoke events will lead to better exposure assessment and epidemiological studies that can account for the protective impact of effective interventions in indoor spaces.
Progress Summary:
Low-cost sensor networks enable measurement of infiltration factors during wildfire smoke periods across building stock. During an extreme wildfire smoke event that affected much of the western U.S. in September 2020, we measured infiltration factors ranging 0.01 – 0.8 in fourteen homes in Portland, OR, USA by making use of publicly available low-cost sensor data. Our study shows that 1) infiltration factors can be obtained from low-cost sensor networks deployed by citizen-scientists, 2) the range of infiltration factors observed imply that a portion of the households in the study deployed highly effective interventions (infiltration factors are typically 0.2 – 0.8), and 3) that time-series data from low-cost sensor networks might be used to improve estimates of infiltration factors during extreme events by isolating the analysis over periods where indoor sources of air pollution are likely to be minimized.
Commercial and DIY air cleaners can be effective in removing some air pollutants relevant to a regional smoke event. Clean air delivery rates (CADRs) for particulate air pollutants appear generally consistent with estimates by manufacturers, when available, for air cleaners with new filter media. We report, to our knowledge for the first time, CADRs for brown carbon and black carbon, which are specific particle-phase constituents that are generated as a result of combustion processes. We also report, again for the first time, CADRs for gas-phase air pollutants relevant to a smoke event. Our preliminary results show wide variability in benzene, toluene, ethylbenzene, and xylenes (BTEX) CADR across air cleaners tested to date. Some air cleaners show no effect while several air cleaners with substantial activated carbon media show meaningful BTEX removal. For example, one air cleaner with a honeycomb style carbon filter showed a BTEX CADR of 210 m3/h. This BTEX CADR is sufficient to meaningfully reduce BTEX concentrations in, e.g., a bedroom of an average U.S. home.
Surface-associated polycyclic aromatic hydrocarbons (PAHs) accumulate during a smoke event, persist for weeks, and can be removed using typical household cleaning processes. Concentrations of PAHs on glass, cotton fabric, and air cleaner filter media were elevated after exposure to a simulated smoke event in the laboratory. We spiked samples of the same materials with known masses PAHs and allowed them to age in an occupied office environment to estimate PAH bulk decay rates. Cotton has the highest decay rate (k = 0.069 d-1) while spiked air filters tend to retain PAHs for a longer period (k = 0.013 d-1). Decay rates on spiked glass stored in a dark location (12 lum/ft2) and on spiked glass stored in a light location (215 lum/ft2) were similar, 0.029 d-1 vs. 0.033 d-1, respectively. We also evaluated cleaning of materials, e.g., washing cotton spiked with PAHs using commercial laundry detergent at high temperature (130°F) followed by a high temperature (135°F) drying program resulted in an overall PAH removal efficiency of 86%.
Future Activities:
Objective 1: We anticipate that the field study will be conducted over the summers of 2023 and 2024. We will focus on method development and deployment in one household in the Spring of 2023 to prepare for a small (3-4 households) deployment of the field study in Summer 2023. We will analyze data and review outcomes in preparation for a larger cohort of households in the Summer of 2024. In parallel, we continue to analyze low-cost sensor data that is available in increasing numbers of homes that allow direct observation of exposure concentrations during periods of elevated wildfire smoke.
Objective 2: We are testing particle and gas-phase air pollution removal of more than fifteen commercial and do-it-yourself air cleaners and air cleaning approaches. These tests are being conducted using a “pull-down” method in a large environmental chamber; our method will report particle clean air delivery rates and develop a method for measuring gas-phase clean air delivery rates using real-time mass spectrometry. After completing this initial characterization, we will conduct experiments to understand how air cleaner effectiveness might change with long duration exposure to smoke, with variable environmental conditions (e.g., humidity level during the test), and the impact of smoke age.
Objective 3: Experimental efforts under Aim 3 are nearing completion, with a final sample and GC-MS run planned for the end of November 2022. We are focusing on analysis of data, interpretation, and writing of papers. We have completed a draft of a paper describing our method for measuring PAHs associated with indoor surfaces which will be submitted by the end of the 2022. Two other papers are in draft form. The first describes the experiments to characterize retention of PAHs on surfaces. The second describes the results of experiments to characterize the cleaning efficiency of accessible approaches to removing PAHs for glass and cotton. We expect these two papers to be complete and submitted to journals for review by April 2023.
Journal Articles:
No journal articles submitted with this report: View all 5 publications for this projectSupplemental Keywords:
Indoor air cleaning, filtration, gas-phase air cleaning, PAHs, persistent organic pollutants, exposure, building mechanical systems, building envelopeRelevant Websites:
Portland State University Healthy Buildings Exit
Progress 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.