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Pages 7-26

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From page 7...
... However, the top five sources of PM2.5 emissions identified in that community are paved road dust, mineral processes,5 and off-road equipment -- three source categories that reflect the community's concerns -- as well as 1  "Secondary" particles are those formed from chemical reactions in the atmosphere. 2  The South Coast Air Basin includes the western portions of Riverside and San Bernardino Counties, the southern two-thirds of Los Angeles County, and all of Orange County.
From page 8...
... As a result, indoor particulate matter includes more particles that tend to linger in the air longer. Overall, estimates of the infiltration factor6 for PM2.5 range between 0.3 and 0.8.
From page 9...
... 60 56 54 2017 2024 2029 51 50 47 45 46 40 36 34 30 30 26 26 26 Tons/year 20 12 12 12 10 9 6 5 0 Paved Road Dust Mineral Processes Cooking Residential Fuel Light Duty Passenger Off-Road Equipment Combustion Auto (LDA) FIGURE 2-2  Top five sources of PM2.5 emissions in the San Bernardino and Muscoy, California, community, actual and projected.
From page 10...
... We will probably have to consider these approaches through a historical lens where we consider the inequities that may confound our approaches, and we can do this by classifying these exposure disparities as either intentional or unintentional." By unintentional exposure disparity, she meant exposure that is not affected directly by humans, such as the wildfires that are emerging as an important source of air pollution as the climate changes. In this case, mitigation could involve increasing the air tightness of the building envelope and installing portable air cleaners, a subject discussed in the third session of the workshop.
From page 11...
... Outdoor particulate matter infiltrates the indoor environment through open windows and other larger openings, as well as through cracks and gaps in the building envelope and mechanical ventilation (Figure 2-5)
From page 12...
... The metrics researchers have used to measure particulate matter infiltration factors fall into two main categories, said Stephens. The most common method uses a chemical surrogate of the samples collected on a filter and weighed.
From page 13...
... . In comparison, the median infiltration factor for PM10 and ultrafine particulate matter (PM0.1)
From page 14...
... Reprinted from Atmospheric Environment 45(2) , Chen C, Zhao B, Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor, pp.
From page 15...
... Together, the studies confirm that ultrafine and large particles do not penetrate and persist for long time periods in buildings. New Directions in Assessing Infiltration and Penetration Factors An exciting piece of research Stephens has seen recently used a low-cost sensor network to estimate infiltration factors at the scale of the building stock (Bi et al., 2021)
From page 16...
... • Improve the direct measurement of penetration factors by increas ing sample sizes and incorporating PM2.5 chemical composition, standardizing approaches, and exploring influencing factors. OUTDOOR PARTICULATE MATTER SOURCES AND THE CHEMICAL TRANSFORMATIONS THAT TAKE PLACE WHEN THEY INTERACT WITH THE INDOOR ENVIRONMENT Building on the foundations laid by Ivey and Stephens, Delphine Farmer focused on sources of particulate matter in the outdoor environment and what happens to those particles after they infiltrate the indoor environment.
From page 17...
... This increase in organic aerosol from biomass burning, said Farmer, is influencing both outdoor and indoor air quality. Several years ago, Farmer and her collaborators put an aerosol mass spectrometer on an airplane, flew it into wildfire plumes, and then traced the smoke plume as it diluted to study the chemistry occurring in the FIGURE 2-6  Output from a NASA model showing the different sources of particulate matter.
From page 18...
... These sources are not evenly distributed across the planet -- there is more sea spray aerosol along the coasts than in the Rocky Mountains, to cite an obvious example -- so there is spatial heterogeneity in the composition of outdoor particulate matter. One recent study found that particle concentration is driven by crustal material, secondary inorganic aerosols, and biogenic secondary organic aerosol, and that anthropogenic aerosol from sources such as wood burning and vehicle wear drives the oxidative potential in that aerosol (Daellenbach et al., 2020)
From page 19...
... . She noted that the fraction of particulate matter produced was small, which she believes is driven by the short timescales over which chemistry can occur in indoor environments.
From page 20...
... 3. How do particle composition and phase affect indoor particulate matter chemistry?
From page 21...
... "They are not individualized causes, and to fix a systemic issue, you need systemic solutions." Farmer added that the nation needs to think about the different sources of outdoor particulate matter, which are out of an individual's control, and understand what those sources are and what they contribute to the health burden in disadvantaged communities. In terms of the many opportunities that exist to decrease particulate matter exposure and improve indoor air quality, she noted that while this is a socioeconomic issue, there is a need for the scientific community to do a better job explaining to all communities which approaches are the best for producing the desired results in a cost-effective manner.
From page 22...
... Stephens said the literature shows that both are being studied. The most robust associations to build on regarding health outcomes are those on long-term exposures to particulate matter, with few studies on the daily exposure component.
From page 23...
... The data show that reducing particulate matter exposure by even small amounts has very substantial beneficial health effects, which is why the Clean Air Act is viewed as one of the strongest pieces of legislation in terms of extending life years of people in this country.
From page 25...
... discussed the role of cooking in generating fine particulate matter (PM2.5)
From page 26...
... In addition, the volatile fraction of cooking emissions can undergo reactions indoors that may produce particles, and a large fraction of indoor particulate matter from cooking is likely to deposit on indoor surfaces. Some of these emissions may find their way outdoors, where they may undergo atmospheric processing, and the volatile components in particular could form secondary organic aerosols outdoors and impact ambient air quality as well.


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