INDOOR BIOAEROSOL BLOOMS ASSOCIATED WITH EXTERIOR CLIMATOLOGICAL MOISTURE EVENTS

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INDOOR BIOAEROSOL BLOOMS ASSOCIATED WITH
EXTERIOR CLIMATOLOGICAL MOISTURE EVENTS
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• Timothy J. Ryan, Ph.D.
• Ohio University, 409 Tower, Athens, OH 45701, USA
• Larry Whitehead, Ph.D., Tom Connor, Ph.D.,
• Keith Burau, Ph.D.
• University of Texas- Houston, School of Public
  Health, Houston, TX 77225, USA

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BACKGROUND

• Problematic role of fungi in non-industrial IAQ
  areas widely reported for decades
• Focus on specific genera, relative ratios
  currently
• Recent studies justify examination of total
  bioaerosol concentration when investigating
  IAQ/SBS complaints

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BACKGROUND

• Meyer et al. (1998)
• SBS symptoms associated with serum Ig-E specific
  to Penicillium links one case of SBS to
  environmental exposure
• Cooley et al. (1998)
• Correlation of increased Penicillium prevalence
  and SBS in school buildings involved in indoor
  air quality (IAQ) complaints

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BACKGROUND

• Arruda et al. (1990)
• Isolated and identified Asp f 1 allergen from
  Aspergillus fumigatus in pure culture
• Noted increase in mean Asp f 1 leaf extract
  concentration following heavy rainfall episodes

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THIS STUDY...

• Role of exterior moisture on interior microbial
  bioaerosols in healthy buildings
• Examine possibility of indoor microbial blooms
  following moisture increases
• Preliminary work on detrimental microbial
  constituents in select SBS episodes

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METHODS

• Thirty (30) non-problematic buildings studied
• Paired sample locations
• Potentially moist site (wet)
• Typically dry location (dry)
• Facilities sampled twice
• Meteorologically defined Lows (rain)
• Hi (no rain) sampling periods
• Total samples 120

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METHODS-Sample Grid
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Definitions

• Hi periods--days of 0.1 inches or less of rain
• subsequent to at least a consecutive (72 hour)
  period of 0.1 inches or less of precipitation
• Low periods--at least 0.5 inches of rain
• included 60 hour period commencing 12 hours
  following rainfall
• Rainfall verified on-site confirmed with U.S.
  National Weather Service data.

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Bioaerosol Collection and Culture

• Mesophilic Fungi Bacteria
• Andersen 5 minute
• Trypticase Soy Agar
• 2-5 days
• 3 minute outdoor twice daily

• Selective Fungi
• Andersen 5 minute
• Malt Extract Agar
• 2-5 days
• 3 minute outdoor twice daily

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RESULTS

• Indoor humidity increased with exterior moisture
• Indoor bioaerosol bloom observed between extremes
• Outdoor bioaerosol levels relatively constant

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RESULTS
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RESULTS
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RESULTS
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COMMENTS

• No significant differences between outdoor and
  indoor microbial concentrations by weather
  condition or location alone
• Low replacement air used in the facilities
  (typically less than 15)
• Relatively energy efficient openings preclude
  mechanical introduction of outside contamination

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CONCLUSIONS

• Exterior rainfall events result in moisture
  loading indoors
• Interior bioaerosol concentrations relative
  humidity vary in conjunction with exterior
  climatological events
• Notion that HVAC set points are absolute is false
  (Houston, TX)

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IMPLICATIONS

• Increased indoor bioaerosol levels observed in
  these healthy buildings might be further elevated
  in facilities experiencing SBS
• IAQ investigations should review exterior
  moisture events immediately prior to, or
  occurring during, such investigations

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QUESTIONS?