Why Indoor Chemistry Matters (2022) / Chapter Skim
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Pages 58-78
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From page 58... ...
Partition coefficients are specific to the contaminant and the material it partitions to, but they can be influenced by environmental conditions, such as relative humidity (as discussed later in this chapter)
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From page 59... ...
. An estimate of the amount of a chemical present in a specific reservoir relative to indoor air can be obtained by multiplying an area-specific partition coefficient (Karea)
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. Most importantly, recent studies have made clear that a range of behaviors on the impacts of water on surfaces and materials can be found in indoor environments as it relates to the chemical partitioning of organic compounds (Wang et al., 2020b)
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From page 61... ...
Indoor air is in direct contact with many such exposed surfaces, providing for rapid uptake and release of chemicals, including reactive species that may not otherwise penetrate below permeable material surfaces. Uptake to such indoor surfaces has been studied since it was recognized that adsorption to the surfaces of steel or glass chambers altered the dynamic air concentration of volatile organic compounds (VOCs)
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. Clear evidence has been found for the heterogeneity of glass surfaces in indoor environments using new microspectroscopic methods to analyze surface films and deposited particles on glass surfaces.
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For example, increasing ventilation by opening a window is usually expected to improve air quality by diluting chemicals that have indoor sources; however, in response to the disruption of equilibrium, near-instantaneous increased emissions of SVOCs stored in surface reservoirs will recharge the air phase, limiting the ability of a temporary increase in ventilation to decrease levels. Consistently high ventilation can eventually deplete these reservoirs, but the time required to lower indoor air concentrations can range from days to years.
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. Particle deposition rates depend on particle size and density as well as indoor air mixing (Lai and Nazaroff, 2000; Nazaroff and Cass, 1987; Thatcher et al., 2002)
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Because dust can be a major source of exposure to chemicals, especially for small children, it has been studied exten sively. As discussed in Chapter 2, thousands of chemicals, including flame retardants, pesticides, plasticizers, and chemical stabilizers, have been quantified in the dust of homes, offices, schools, and daycare centers (Lucattini et al., 2018)
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From page 66... ...
compared measurements of SVOCs in skin lipids from the Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants study to values predicted based on air concen trations and octanol-air partition coefficients. They found good agreement, implying that SVOCs in skin lipids were roughly equilibrated with indoor air, allowing partitioning to be predicted from standard thermodynamic parameters.
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From page 67... ...
In particular, such exposure models require predictions of the distribution of the chemicals across indoor spaces in order to assess different exposure mechanisms. For example, a recent model describes how Koa and Kwa are used to assess the degree of inhalation, dermal, and dietary and non-dietary ingestion exposures that arise for many organic chemicals in the indoor environment as a function of the fundamental properties of the molecules (Li et al., 2019)
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From page 68... ...
RESEARCH NEEDS Given its findings about the current state of the science, the committee has identified priority research areas to help drive future advances in chemical partitioning relevant to indoor environments: • Expand equilibrium and nonequilibrium (dynamic and steady-state) partitioning studies to include a larger variety of materials present in buildings.
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Indoor Air 30(4)
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Indoor Air 30(5)
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2019. How are humans exposed to organic chemicals released to indoor air?
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in the indoor environment: Occurrence in consumer products, indoor air and dust. Chemosphere 201:466–482.
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2020b. Surface reservoirs dominate dynamic gas-surface partitioning of many indoor air constituents.
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Indoor Air 11(4)
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Surface-adsorbed molecules may diffuse into the bulk of indoor surfaces and materials, where they may undergo chemi cal transformations. The relative rates of ventilation, gas-phase loss, and loss to surfaces are important to compare when evaluating the fate of an indoor air molecule.
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From page 76... ...
. The spatial, tem poral, and spectral variability need to be taken into account when considering the role of photochem istry in indoor environments (Kowal et al., 2017; Weschler and Carslaw, 2018; Zhou et al., 2020)
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From page 77... ...
, indoor air constituents often have been treated as well mixed and homogeneously distributed in ventilated indoor environ ments. Hence, indoor measurements are mostly conducted at a single location in a room and at a fixed height, and indoor chemistry models often employ a box model assuming homogeneous mix ing.
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From page 78... ...
Common Atmospheric Oxidants, Including Ozone Given a sizable supply arising from outdoor-to-indoor air exchange (Stephens et al., 2012) , ozone multiphase chemistry has been studied extensively with numerous recent findings.
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