Health Risks of Indoor Exposure to Particulate Matter Workshop Summary (2016) / Chapter Skim
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3 Particle Dynamics and Chemistry
3 Particle Dynamics and Chemistry
Pages 25-40
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From page 25... ...
He noted that mitigation strategies can have a huge effect on particle dynamics -- an idea relevant to the presentation of the first speaker, Jeffrey Siegel of the University of Toronto, who provided a building-science perspective on the dynamics of particle size and concentration indoors. After Siegel's presentation, Glenn Morrison of the Missouri University of Science and Technology discussed indoor chemistry and aerosols, and then Charles Weschler of Rutgers University described the composition of indoor PM and the influence of SVOC partitioning on that composition.
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From page 26... ...
Improvements in modeling and measurements offer great promise for characterizing particulate matter accumulation on surfaces and its influence on resuspension. As Brandon Boor noted in the previous sessions, researchers have made progress in understanding the role that resuspension plays in determining indoor PM concentrations (Boor et al., 2013; Kassab et al., 2013; Mukai et al., 2009; Qian and Ferro, 2008)
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From page 27... ...
"If we really want to understand indoor particles, we have to understand HVAC systems," Siegel said, "yet we are far behind in this area." To illustrate how little is known about key fundamental parameters of HVAC systems, Siegel said that HVAC runtimes have been measured in only 213 homes, all from the southeastern United States and only over a few days to 1 week (Cetin and Novoselac, 2015; Stephens et al., 2011; Thornburg et al., 2004)
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From page 28... ...
28 HEALTH RISKS OF INDOOR EXPOSURE TO PARTICULATE MATTER FIGURE 3-1 The location and effectiveness of portable air cleaners in removing indoor PM. NOTE: CADR = clean air delivery rate.
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From page 29... ...
As one step toward filling these knowledge gaps, Siegel suggested that the field conduct what he called a "long-form building census" which would address the key building science parameters needed to understand and mitigate exposures to particles in buildings. Conducting such a census
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From page 30... ...
One well-studied atmospheric chemical reaction involves volatile organic compounds reacting with an oxidant, such as ozone, nitrate, or hydroxyl radical, to generate a variety of molecular products. The resulting sticky, polar molecules can serve as nuclei around which particles form, or else the polar molecules can condense onto existing particles.
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From page 31... ...
Room occupancy is an important factor in aerosol chemistry because skin contains chemicals that react readily with ozone. Human and animal bodies constantly shed skin in the indoor environment, and these skin cells and the skin oils can adhere to indoor surfaces.
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From page 32... ...
These instruments include highresolution aerosol mass spectrometry for analyzing PM composition, fluorescence assay by gas expansion for detecting hydroxyl radicals, cavity ring-down spectroscopy for measuring nitrogen oxides, and direct analysis in real-time mass spectrometry for the real-time characterization of surface films. "Almost none of these instruments have been used indoors until very recently," Morrison said.
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From page 33... ...
Weschler said that comparing the chemicals present in indoor and outdoor PM2.5 shows indoor PM2.5 that are rich in chemicals additives used in products that are part of the indoor environment, such as phthalate plasticizers, organophosphates, brominated flame retardants, and fluorinated surfactants. By weight, indoor PM2.5 is approximately 50 percent organic carbon, with elemental carbon accounting for only 3 percent of the total particle mass.
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From page 34... ...
The partitioning of SVOCs and various inorganic compounds between the gas phase and the surface of airborne particles plays an important role in determining the chemical composition of particles, Weschler said. In one of the first applications of aerosol mass spectrometry to the study of indoor PM, Michael Waring and his colleagues (Johnson et al., 2016)
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From page 35... ...
. Increasing the level of SOAs affects SVOC partitioning in indoor environments by increasing both the concentration of airborne particles and the fraction of organic matter in the airborne particles, Weschler said.
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From page 36... ...
to the iron in these particles. Another question Weschler said he would like to see addressed concerns the timescale over which SVOCs desorb from inhaled PM and the residence time of particles in the respiratory tract, which are important factors for the potential health effects of breathing PM.
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From page 37... ...
"We are fairly certain that some SVOCs in some particle size ranges make it to the alveoli, while for other SVOCs and in other size ranges, the SVOCs desorb fairly high in the respiratory tract." Experimental studies, he added, have proved to be even more challenging than the modeling efforts. Weschler also questioned the role that reactive oxygen species associated with PM might play in triggering oxidative stress.
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From page 38... ...
Siegel also said that there are many inexpensive and easy steps that could be taken today to protect people in buildings from PM exposure without having to wait for better characterized buildings and particles. Offering one specific example of such a step, he said, "It is a no-brainer for certain people in certain indoor environments to be using better filtration or activated carbon filtration." Morrison agreed with Siegel that the presumption from a chemistry perspective is that indoor exposure to SOA is not good.
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From page 39... ...
Siegel added that UV lights also contribute to the degradation of certain components and insulating materials in HVAC systems. Corsi said that he has found UV light systems in many animal shelters and has measured high ozone levels in kennels in those shelters.
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