Microbiomes of the Built Environment A Research Agenda for Indoor Microbiology, Human Health, and Buildings (2017) / Chapter Skim
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5 Interventions in the Built Environment
5 Interventions in the Built Environment
Pages 189-218
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From page 189... ...
In enabling a better understanding of the effects of different interventions, such frameworks can aid in the d esign of future intervention approaches. • Models used in studying, designing, and making decisions about built environment interventions will need to include not only aspects of the built environment and the microbiome but also occupant behavior, health impacts, and potential trade offs with energy consumption and economic factors.
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m This chapter describes existing and potential interventions for modifying human microbial exposures to improve health. The discussion identifies potential trade-offs associated with such interventions, such as increased energy consumption or building costs.
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. Increasing the rate of outdoor air ventilation is effective as an intervention only when the air contaminant concentration outdoors is lower than that indoors.
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Thus, increasing ventilation would be an effective strategy for such species only if the outdoor air were subjected to filtration or other treatment. In considering the impact of increased outdoor air ventilation on levels of indoor airborne contaminants, it is also important to consider the loss mechanisms that could be added to Equation 5.1 and the generation mechanisms embodied in the term G
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However, resuspension of microbes in densely occupied settings, such as classrooms, can dramatically increase indoor air concentrations of bacteria and fungi, even at high outdoor air ventilation rates (Hospodsky et al., 2015)
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, the importance of outdoor air ventilation is predictable. In one study, for example, installation and operation of heat recovery ventilators (ventilation systems that bring outdoor air into buildings and transfer heat from the outgoing airstream to the incoming airstream)
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Increased ventilation in Swedish homes, for example, is indirectly associated with lower concentrations of airborne dust mite allergens because dust mite activity and growth are associated with high RH. In the cold, dry candinavian climates, S increased outdoor air ventilation results in lower indoor RH levels (Sundell et al., 1995)
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From page 196... ...
Gaps in knowledge about what represents "normal" microbial ecology and how to interpret particular microbial findings are one reason that building microbial sampling often is not recommended. The issue of microbial sampling for building microbial assessment and remediation strategies is beyond the scope of this report.2 2 The American Industrial Hygiene Association, for example, has a position statement on Mold and Dampness in the Built Environment (AIHA, 2013)
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. The standard also requires MERV 6 filters in the outdoor air intake when outdoor levels of particulate matter (PM)
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UVGI, typically from low-pressure mercury vapor lamps with spectral power distribution focused at 254 nm, has been applied to disinfect indoor air and surfaces for
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While UVGI can be effective at microbial inactivation, its effect against the allergenic or toxigenic properties of microbes is not well described. UV disinfection has commonly been adapted for use within the upper levels of rooms for effective air disinfection, placed on cooling coils to reduce microbial growth on and fouling of coils, placed in airsupply ducts, and more recently applied in surface disinfection.
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. CHEMICAL INTERVENTIONS TO REDUCE EXPOSURE TO HAZARDOUS MICROBES Chemical interventions in the built environment focus on the inactivation of surface-bound microbes through the use of chemical disinfectants and, to a lesser extent, on the introduction of antimicrobial materials.
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It is also important to note that tremendous differences exist among indoor building materials, all of which have different porosities, as well as chemical compositions that affect their ability to host dirt, microbes, skin cells, hair, and other human effluents in and on which microbes survive. Specialty practices exist for introducing aerosols containing oxidants and surfactants inside built environments for the express purpose of indoor disinfection.
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. Activating antimicrobial surfaces with such metals as copper or silver and applying liquid compounds, including biocidal paints, that confer on surfaces persistent antimicrobial activity are additional strategies that require validation and further investigation for built environment application.4 INTERVENTIONS TO ENCOURAGE EXPOSURE TO BENEFICIAL MICROBES Although the focus of a variety of microbially motivated building interventions has been on reducing exposure to harmful microbes, a more recent emphasis is on encouraging exposure to potentially beneficial microbes (an idea also known as "environmental probiotics")
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For example, accumulating evidence suggests that perinatal exposures to microorganisms are important in establishing the human microbiome in early life, but the effects of microbial exposures in adulthood are much less well understood. 6 Environmental probiotics would require registration under FIFRA if claims of pesticidal effect were made; however, if there were no claims of pesticidal effect, the product might not need to be registered.
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Evidence suggests that human well-being in urban areas is linked to neighborhood greenness, and recent research, discussed below, suggests that this link may be driven in part by indoor exposure to the diverse microbial communities associated with plants. Questions remain, however, as to how outdoor landscape features and the presence of indoor plants influence indoor micro iome quality.
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Material Balance Modeling Central to assessment of built environment interventions is understanding the fate and transport of and human exposure to microbes in indoor air. All buildings are unique, but the dynamics of microbes and microbial communities within the built environment are controlled by a narrower regime of mostly physical processes (reviewed by Nazaroff [2016]
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The application of models specific to microbes is limited largely by the lack of microbial information with which to run dispersion models for assessing exposure, limited dose-response information for microbial agents, and poor understanding of the variety of responses to microbes within a human population. Because particle size drives many of the important physical processes detailed in Figure 5-1, more information on the size distributions of indoor air microbes of importance is necessary.
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Nazaroff (2004) Indoor Air, 14, page 175 representing ventilation sources and losses.
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Depending on outdoor climate and conditions and the use of strategies that include economizers, increased building envelope tightness, heat recovery ventilation, and demand-controlled ventilation, increasing outdoor ventilation rates to a level that improves indoor air quality in general and reduces exposure to indoor-generated microbial contaminants does not necessarily come at significantly increased energy or capital costs (Persily and mmerich, 2012)
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, chemicals, and particulate matter into the built environment. Filtration of incoming outdoor air may reduce the influence of hazardous outdoor particles, but it will not remove gases and may also eliminate potentially beneficial outdoor microbes associated with an outdoor biodiverse environment.
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. Expanding Models to Include Health Outcomes, Economics, and Energy The output of the dispersion models described earlier in this chapter includes indoor air concentrations and human exposures.
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The onus for improved indoor environmental quality cannot reside solely with building operations, particularly because air and water from outside sources are important inputs to indoor environments. Instead of reliance on the building envelope to control all exposures, researchers will need to consider the broader perspectives for meeting the diverse goals of improving microbial indoor air quality, recognizing which goals cannot be achieved absent good outdoor air quality.
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3. Obtain additional data necessary to support the use of a variety of quantitative frameworks for understanding and assessing built environment interventions.
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2013. Dispersal in microbes: Fungi in indoor air are dominated by outdoor air and show dispersal limitation at short distances.
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Indoor Air 10(1)
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Indoor Air 2(6)
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2014. Indoor airborne bacterial communities are influenced by ventilation, occupancy, and outdoor air source.
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Indoor Air 4(2)
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Indoor Air 21(3)
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