Indoor Exposure to Fine Particulate Matter and Practical Mitigation Approaches Proceedings of a Workshop (2022) / Chapter Skim
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From page 27... ...
(2020) Figure 1.1 1 https://pubs.acs.org/doi/10.1021/acs.est.0c00740; reprinted with permission from American Chemical Society Publications.
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(2020) Figure S5.1 1 https://pubs.acs.org/doi/10.1021/acs.est.0c00740; reprinted with permission from American Chemical Society Publications.
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Surface deposition can serve as an important sink for indoor particulate matter rich in organic matter. HOMEChem experiments found that although the Thanksgiving Day experiment produced higher airborne particulate matter concentrations than during a normal cooking event, the amount of particles deposited on a piece of glass (which was set up for testing purposes)
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30 Total indoor concentration of SVOCs (gas phase + PM2.5 particle-bound) : FIGURE 3-3 Indoor residential activities enhance semivolatile organic compound (SVOC)
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(2020) Figure 4.1 1 https://pubs.acs.org/doi/10.1021/acs.est.0c00740; reprinted with permission from American Chemical Society Publications.
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For cooking, effective source control means operating a high-quality, externally vented over-the-stove hood every time cooking activities occur or using a well-positioned, properly selected portable air cleaner. SECONDARY AEROSOL FORMATION OF FINE PARTICULATE MATTER IN THE INDOOR ENVIRONMENT Organic aerosol, explained Michael Waring, comprises hundreds of thousands of types of molecules existing in a state of dynamic equilibrium between the gas and particle phases.
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Lumped product modeling has particular strengths relative to explicit product modeling in that it can account for any arbitrary type of organic aerosol source, both indoor and outdoor; is not limited to secondary organic aerosols; and allows easy computation of bulk aerosol properties such as density or hygroscopicity. After describing the parameters and equations his group uses in its models, Waring explained that this model can yield organic aerosol concentrations based on the volatility of organic mass and oxidation state.
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While secondary organic aerosols are typically the smallest component of indoor organic aerosols, they can dominate both the aerosols and particulate matter when ozone and terpene levels are high and air exchange rates are low. Research Needs In the final portion of his presentation, Waring highlighted future research needs.
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The final research need that Waring identified was to better understand the influence of ozone and hydroxyl-producing technologies, such as ultraviolet lamps and bipolar ionization found in newer ventilation systems, on secondary organic aerosol formation. THE EFFECT OF HUMIDITY ON THE CHEMISTRY AND BIOLOGY OF INDOOR AIR Humidity is not a direct source of indoor particulate matter, but it does affect the chemistry and biology of airborne substances, said Linsey Marr.
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, demonstrating that relative humidity, which dynamically controls the water content of particulate matter and hence the concentration of the chemicals, bacteria, and viruses in those particles, affects both the chemistry and biology in aerosols. 2 A solute is a component of a solution, dissolved in a separate solution (the solvent)
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Figure 3B; Copyright 2021 American Chemical Society Publications. THE INFLUENCE OF SOURCES OF INDOOR FINE PARTICULATE MATTER ON THE CHARACTERIZATION OF EXPOSURE AND EVALUATION OF HEALTH EFFECTS To start the day's final presentation, Andrea Ferro highlighted a 1996 review paper on indoor particles that summarized studies in what was then a fairly new field (Wallace, 1996)
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Indoor particulate matter also contains microbes that may originate from humans, plants, pets, plumbing systems, HVAC equipment, mold, resuspension of settled dust, and outdoor air (Prussin and Marr, 2015)
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Ferro raised the question of whether ambient air quality standards can be used to assess indoor air pollutants. In her opinion, the answer is no given that only some ambient particulate matter makes it indoors.
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A first step is to develop additional knowledge about human activity patterns, determine how personal habits differ with socioeconomic status, culture, and even region of the country, and use that information to inform better experiments to understand realistic exposures. Waring said that for secondary organic aerosols, there are three questions that if answered could start to yield a picture of disparities and secondary aerosol exposure among those who live in underserved or poorer communities: • Are there differences in outdoor concentrations for underserved communities or are they in regions of higher ozone and organic or inorganic particulate matter concentrations, which can infiltrate and potentially drive secondary chemistry?
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Marr noted that she has been collaborating with a colleague on energy savings and building in underserved communities as these two factors pertain to indoor environmental quality. The residents of those communities, she said, are not concerned about ozone, volatile organic compounds, or plasticizers, but are very concerned about mold because they experience major asthma and allergy issues, which are more prominent in underserved communities.
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Chan offered a final question, asking where resources should be spent in schools, given what is known about indoor particulate matter. Waring said that the greatest need in the Philadelphia schools he is familiar with would be adequate ventilation.
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The first was that when considering indoor fine particulate matter, it is important to account for precursors and other things that can modify PM2.5, such as the presence of vapor-phase material that can condense into particulates. He named five broad categories of influential factors: situational, building and HVAC, activity and mobility, occupant perceptions and behavior (noting that how people perceive the risks associated with particulate matter might modify their behavior, leading to changes in exposure and even how much is generated)
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• Measure unknown input parameters that go into models in order to apply the models more broadly. • Characterize the composition of indoor PM2.5 and the drivers that produce specific types of particulate matter.
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