Why Indoor Chemistry Matters (2022) / Chapter Skim
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2 Primary Sources and Reservoirs of Chemicals Indoors
2 Primary Sources and Reservoirs of Chemicals Indoors
Pages 19-54
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. This chapter first aims to provide an overview of the major types of continuous and episodic primary sources and reservoirs of chemicals in the indoor environment and to describe the domi nant factors that affect their emission rates.
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This chapter sets the stage for the committee's subsequent discussions of how these primary emissions are redistributed in the indoor environment (Chapter 3) and chemically transformed into secondary sources (Chapter 4)
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Emission rates can be highly variable and are driven or influenced by multiple factors, including human activities, building characteristics, physical parameters, environmental conditions, and spa tial and/or temporal factors. We define continuous sources as those constantly emitting chemicals into indoor environments at rates that may vary due to environmental conditions (e.g., temperature, humidity, and ventila tion)
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Emphasis is placed on newer sources or source categories of relevance to indoor chemical concentrations and human exposures and on emerging science within each category. Continuous Sources and Reservoirs Building materials are continuous sources of gas-phase emissions in indoor environments.
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b (°C) b Rangeb Primary Sources (ppb, mol/molvolume)
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b (°C) b Rangeb Primary Sources (ppb, mol/molvolume)
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Chemical class properties generally represent the straight chain structures of the class, with ranges shown to represent what has been historically measured in indoor environments. b Most chemical class properties are taken from EPA's CompTox Chemicals Dashboard with noted values (a)
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<10 μm (PM10) abrasion, paint chipping, Vardoulakis et al., 2020; Zwoz´ dziak skin flakes et al., 2013 ELEMENTAL COMPOSITION OF PM2.5 GROUPED BY TYPICAL SOURCE Concentration Range Chemical Component Example Primary Sources in Indoor Air References for Concentration Ranges Organic Carbon (OC)
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The migration of chemicals from buildings, materials, and consumer products into dust can mimic the pathways that lead to human exposure. This suggests that the chemical composition of dust can be representative of personal exposure to some chemicals in the indoor environment.
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. The need to quantify the diversity of microbial species that influence indoor air across a variety of indoor environments and materials remains (Bekö et al., 2020; Prussin and Marr, 2015)
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. Temporal factors influencing rates of chemicals infiltrating from outdoors into indoor environments include diurnal or weekday/weekend patterns (e.g., traffic-related nitrogen oxides [NOx]
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. A recent study in a German movie theater found that third-hand smoke is an important source of exposure in nonsmoking indoor environments, where VOCs, hazardous air pollutants (e.g., benzene and form aldehyde)
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While the personal cloud effect is well documented (Licina et al., 2017; Wallace, 2000; Weschler, 2016) , several recent studies have characterized emission rates of human activities in indoor environments, including the effects of a crawling infant on dust resuspension (Hyytiäinen et al., 2018; Wu et al., 2021a)
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. Tables 2-1 and 2-2 present a summary of several chemicals and chemical classes that have primary sources and reservoirs in the indoor environment, in the gas, dust (Table 2-1)
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, or particles with an aerodynamic diameter ≤2.5 μm, are usually emitted from primary sources like combustion and secondary formation indoors and reported in mass concentrations (μg/m3)
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Bottom-Up Inventories of Chemicals in Indoor Environments A bottom-up approach determines the chemical composition of or emission from every mate rial, item, or product found indoors, including the wide range of examples found in this chapter thus far. Two drivers currently exist for measuring emissions from building materials in a bottom-up manner.
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As a result, chemicals of concern are identified after their use, rather than prior to their use, in the United States. PCBs are an early case study demonstrating how chemicals can migrate from the original products to become widespread and persistent in the indoor environment.
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instruments to indoor environments has allowed for the analysis of chemicals overlooked with traditional techniques. For in stance, using a PTR-MS, decamethylcyclopentasiloxane (D5)
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analytical techniques. Recent advances in analytical techniques and application of outdoor measurement technologies and methods to indoor air quality have decreased detection limits of known indoor compounds, increased the number of different chemicals detected in the indoor environment, and increased the time resolution of samples.
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These factors prevent the application of these instruments to large numbers of homes or other indoor spaces in field campaigns. Since these instruments have not been used in a significant number of indoor environments, potential interference issues in high-concen tration indoor environments are unknown.
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. Due to cost and complexity, the application of AMS, TAG, and similar instruments to the indoor environment has been limited.
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. These methods provide more insight into the complex and diverse suite of chemicals that are present in indoor environments, yet they are not currently at a point where every chemical in the thousands in a mass spectrum of an indoor air or dust sample can be identified -- let alone quantified.
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Surface Sampling Traditional Techniques Surfaces in indoor environments, including windows, countertops, and walls, accumulate organic films and act as sinks, reaction sites, and reservoirs for SVOCs (Weschler and Nazaroff, 2008)
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and challenges in identifying chemical sources in the indoor environment will continue to be major obstacles to chemical management and risk evaluation. 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 understanding primary sources and reservoirs in indoor environments: • Prioritize acquisition of actionable data and research to link sources with exposures and understand impacts of mixtures on health.
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The vast majority of the information presented in this chapter refers to research conducted in residential settings and in high-income countries. However, people spend time in other indoor environments, which may have different sources and emission rates.
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2019a. Human occupant contribution to secondary aerosol mass in the indoor environment.
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2021. Real-time organic aerosol chemical speciation in the indoor environment using extractive elec trospray ionization mass spectrometry.
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2017. Comment on "Mutagenic azo dyes, rather than flame retardants, are the pre dominant brominated compounds in house dust." Environmental Science & Technology 51(6)
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2011. Climate Change, the Indoor Environment, and Health.
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2020. Human ammonia emission rates under vari ous indoor environmental conditions.
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in the indoor environment: occurrence in consumer products, indoor air and dust. Chemosphere 201:466–482.
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Microspectroscopic imaging and physicochemical characterization of indoor depositions on window glass. Environmental Science & Technology Letters 5(8)
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2018. Human exposure to ozone in school and office indoor environments.
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2008. Semivolatile organic compounds in indoor environments.
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Environmental Science & Technology Letters 7(10)
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NAS-A00426-Indoor_Chemistry.indd 54 01/10/2022 7:25 AM
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