Regional Shelter Analysis: Inhalation Exposure Application (Particles)

Dillon, Michael; Sextro, R.G.; Delp, William W.

doi:10.2172/1577234

Cited by 7 publications

(51 citation statements)

References 64 publications

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“…Overall, only a small fraction (3 × 10 −8 ) of sampled particles would be expected to reach population centers across North America and be inhaled during the first week. The actual amount of material inhaled would be smaller than predicted here since (a) most people are indoors and (b) indoor individuals have lower exposure, relative to outdoor individuals, to outdoor-origin airborne particulates 32,33 .…”

Section: Relative Abundance Proportionally Abundant Microbial Taxa Fmentioning

confidence: 59%

Sierra Nevada sweep: metagenomic measurements of bioaerosols vertically distributed across the troposphere

Jaing

Thissen

Morrison

et al. 2020

Sci Rep

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To explore how airborne microbial patterns change with height above the Earth's surface, we flew NASA's C-20A aircraft on two consecutive days in June 2018 along identical flight paths over the US Sierra Nevada mountain range at four different altitudes ranging from 10,000 ft to 40,000 ft. Bioaerosols were analyzed by metagenomic DnA sequencing and traditional culturing methods to characterize the composition and diversity of atmospheric samples compared to experimental controls. The relative abundance of taxa changed significantly at each altitude sampled, and the diversity profile shifted across the two sampling days, revealing a regional atmospheric microbiome that is dynamically changing. the most proportionally abundant microbial genera were Mycobacterium and Achromobacter at 10,000 ft; Stenotrophomonas and Achromobacter at 20,000 ft; Delftia and Pseudoperonospora at 30,000 ft; and Alcaligenes and Penicillium at 40,000 ft. Culturebased detections also identified viable Bacillus zhangzhouensis, Bacillus pumilus, and Bacillus spp. in the upper troposphere. to estimate bioaerosol dispersal, we developed a human exposure likelihood model (7-day forecast) using general aerosol characteristics and measured meteorological conditions. By coupling metagenomics to a predictive atmospheric model, we aim to set the stage for field campaigns that monitor global bioaerosol emissions and impacts. Aerosols (mostly desert dust, black carbon and ocean spray) regularly disperse across the Pacific Ocean with springtime atmospheric winds-in fact, models suggest that as much as 64 Teragrams of Asian aerosols can be transported to North America annually 1. Past studies have reported microorganisms co-transported with globally-dispersed aerosols, and that both DNA signatures and viable cells can be detected in air masses 2-4. For example, thousands of taxonomic signatures were measured in springtime Asian dust plumes delivering free tropospheric bioaerosols to an alpine research station in central Oregon 3. In a separate flight project surveying airborne microorganisms in the western region of the United States, several taxa were found to be enriched in the upper atmosphere, including bacterial families Lachnospiraceae, Ruminococcaceae and Erysipelotrichaceae 2. Despite harsh conditions in the atmosphere, viable bacterial isolates were recovered from the same study 2 , including Bacillus sp., Micrococcus sp., Arthrobacter sp. and Staphylococcus sp. Previous aerobiology campaigns using aircraft were flown at single altitudes in order to refine collection methods and demonstrate some of the first measurements of an atmospheric microbiome 2,5-7. To date, there are only a few studies that have examined microbiological changes across a vertical gradient in Earth's troposphere 8-10. More studies using advanced genomic techniques such as shotgun metagenomic sequencing will be essential to formulating predictive models of bioaerosols and how the atmospheric microbiome is influenced by meteorological

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Section: Relative Abundance Proportionally Abundant Microbial Taxa Fmentioning

confidence: 59%

Sierra Nevada sweep: metagenomic measurements of bioaerosols vertically distributed across the troposphere

Jaing

Thissen

Morrison

et al. 2020

Sci Rep

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“…For this application, exposure is defined as the time-integrated airborne particle concentration, hence the Building Transmission Factor is not simply the ratio of indoor to outdoor concentrations. [6], [7] provide more details, discussion, and alternative equations for other exposure metrics.…”

Section: Reducing Indoor Exposures To Outdoor Airborne Particles (Buimentioning

confidence: 99%

“…Our modeling is based on the building use type categories and parameters values described in our earlier report [7] and briefly summarized here. The tables that follow are adapted from that report, where additional discussion and descriptive details may be found.…”

Section: Building Parameter Valuesmentioning

confidence: 99%

“…The mapping for other HAZUS categories is less clear and for some categories there are limited published data available. For these cases, we made estimates based on best engineering judgment and adapted the available input data to conform to the HAZUS building types (as discussed below and in [7]). Single box modeling may not adequately represent the indoor airborne particle concentrations for some parking garages (COM10) and so we exclude this building use type from our analysis.…”

Section: Building Model Assignmentmentioning

confidence: 99%

“…Our modeling uses the Building Transmission Factor metric (BTF) which is the ratio of indoor to outdoor exposures, where exposures are time-integrated airborne particle concentrations. The BTF, sometimes called the Building Exposure Ratio, is the inverse of the Building Protection Factor metric used in our previous RSA work [6], [7]. In addition to the BTF, two related, but distinct, building metrics are also of interest and are analyzed here: (a) the Indoor Normalized Time and Space Integrated Air Concentration (TSIAC) which is the degree to which indoor individuals are exposed to indoor airborne particles (the indoor time and space integrated air concentration normalized to the release of a unit amount of airborne material, such as a single particle or a µg of material) and (b) the Building Exit Faction (BEF) which is the fraction of indoor airborne particulates that exit the building and enter the outdoor atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Reducing Exposures to Airborne Particles Through Improved Filtration: A High-Level Modeling Analysis

Dillon

Sextro

2020

Preprint

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Indoor airborne particulates are well-known health hazards and filtration is one common method of reducing exposures. Based on our previously developed Regional Shelter Analysis methodology and parameters that characterize the existing US building stock, we perform a high-level assessment of the potential benefits of upgrading existing filters in furnace and in heating, ventilation, and air conditioning systems using off-the-shelf filters. We use three metrics to assess the improvement: Building Transmission Factor (a measure of protection against outdoor airborne particles), Indoor Normalized Time and Space Integrated Air Concentration (a measure of indoor exposure to indoor-origin airborne particles), and Building Exit Fraction (fraction of indoor airborne particles that are released to the outdoor atmosphere). We also discuss the potential reduction in regional exposures due to particles exiting the building and exposing downwind building occupants. Our modeling indicates that while buildings provide their occupants passive protection against airborne particulate hazards, including but not limited to PM2.5, PM10, and wildfire smoke; improving particle filtration efficiency may further improve this protection. The degree of improvement varies with particle size and building type. Of the building types studied, apartments are predicted to benefit most, with greater than a factor of 2 improvement (≥50% reduction in exposures) for 1 micron particle exposures when using MERV 7 to 12 rated filters. Non-residential buildings were notably less responsive to improved filtration but had the highest Building Exit Fractions with 30% to 40% of indoor airborne particles released to the outdoor atmosphere (apartment buildings only released 6% to 9%). Improvements predicted for single family homes were intermediate between apartments and non-residential buildings. Improvements in the Regional Exposure metric are larger, ranging from a factor of 2.5x to 10x for residences (when using MERV 7 to 12 rated filters) and up to 25x for large apartments with MERV 14 or 15 rated filters. The results of our modeling analysis are broadly consistent with the limited experimental data and modeling results available in the literature.

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