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Alan J. Neumann, Ph.D.
Indoor Ecology Associates Inc.
FACTORS OF FUNGAL SPORE
DISPERSAL
AND INDOOR BIOAEROSOLS
INDOOR ENVIRONMENTAL QUALITY
ASSESSMENTS
February, 2011 IAQA CONFERENCE 2
• Investigations of indoor environments often include
collection and evaluation of indoor bioaerosols
• Bioaerosols are defined as living organisms, or remains of
organisms, that become airborne
• Collection of representative FUNGAL bioaerosol samples
are one component of the evaluation process
RELATION OF FUNGAL SPORE DISPERSAL
TO INDOOR ENVIRONMENTAL
ASSESSMENT
February, 2011 IAQA CONFERENCE 3
• Fungi are part of the natural environment
• Fungal species exist in environmental niches to which they have adapted
• They exhibit survival strategies
• They produce natural fungal bioaerosols
• Indoor fungal reservoirs
• Some fungal species have adapted to man-made/indoor environmental niches
• These fungi produce fungal bioaerosols indoors
TERMINOLOGY
February, 2011 IAQA CONFERENCE 4
• Mould (Illman 1970 Mycologia)
• Derived from a Scandinavian language and refers to something
fuzzy
• Advocated for American use for a fungus rather than ‘mold’
• Microfungus with well-defined mycelium or spore mass
• Hypha
• Filament of fungal cells, attached end-to-end, one cell in width
TERMINOLOGY
February, 2011 IAQA CONFERENCE 5
• Mycelium
• Mass of hyphae derived from single spore germination; entire colony
• Spore
• General term for a fungal reproductive structure.
• Differentiated form which may be:
• Specialized for dissemination
• Produced in response to adverse environmental conditions
• Produced by sexual or asexual reproductive processes
CELL WALL STRUCTURE
February, 2011 IAQA CONFERENCE 6
TERMINOLOGY
February, 2011 IAQA CONFERENCE 7
• Conidium (conidia)
• Specialized, non-motile, asexual spore, not developed by cytoplasmic cleavage (sporangiophore) or free-cell formation (ascus)
• Commonly refers to asexual spores
• 7 types of spores based on shape, septation, and pigmentation (e.g., amerospore, dictyospore, helicospore)
• Conidiophore
• Simple or branched hypha bearing conidiogenous cells
February, 2011 IAQA CONFERENCE 8
Scanning electron micrograph of a fungal
asexual reproductive body of a species of the
genus Aspergillus
.Image from the College of Veterinary Medicine, Mississippi
State University.
MYXOSTELIDA
• Slime moulds
• Stemonitis spp.
• Upper right – macro of
sporangia
• Lower right – micro of
reticulated interior wall of
sporangium and spores
February, 2011 IAQA CONFERENCE 9
BASIDIOMYCETES
• Mushrooms are common
basidiomycetes of lawns and
woods
• Spores borne on gill or pore
walls of cap
February, 2011 IAQA CONFERENCE 10
BASIDIOMYCETES
February, 2011 IAQA CONFERENCE 11
SEM micrograph of bolete spores
BASIDIOMYCETES
February, 2011 IAQA CONFERENCE 12
Copied from Dr. Wong U of Hawaii
DEUTEROMYCOTINA
February, 2011 IAQA CONFERENCE 13
Penicillium atramentosom
By David Spero
DEUTEROMYCOTINA
February, 2011 IAQA CONFERENCE 14
Memnoniella spp. - UNLV
DEUTEROMYCOTINA
February, 2011 IAQA CONFERENCE 15
Memnoniella echinata
Copied from Campbell, 1975
DEUTEROMYCOTINA
February, 2011 IAQA CONFERENCE 16
Memnoniella echinata and Stachybotrys chartarum
Copied from Haugland et al, 2001
DEUTEROMYCOTINA
February, 2011 IAQA CONFERENCE 17
Stachybotrys spp. – SUNY ESF
CONSIDERATIONS OF SPORE
DISPERSAL CRITERIA
February, 2011 IAQA CONFERENCE 18
• Dispersal mechanisms evolved with ‘life strategy’ for
survival
• Mechanism for detachment from parent
• Size of spore/conidium
• Most less than 10 mm in diameter
• Environmental factors
• Relative humidity
• Air currents
TERMINOLOGY
February, 2011 IAQA CONFERENCE 19
• Spore types
• Memnospores
• Spores that remain in place of origin to tide over
unfavorable environmental conditions
• Xenospores
• Spores dispersed to new geographic locations
• Often thin-walled
• Easily detached from parent hypha
SPORE/CONIDIA CHARACTERISTICS
February, 2011 IAQA CONFERENCE 20
• Stachybotrys chartarum – ellipsoidal, 5-7 X 8-12mm,
gelatinous coat creating clump of spores
• Aspergillus fumigatus – globose, 2.5-3mm
• Cladosporium herbarum – ovate, 2+ cells, 3-23mm
• Epicoccum nigrum – globose to pyriform, multi-celled,
15-25mm
• Penicillium chrysogenum – globose to ellipsoidal,
2.5-4 X 2-3.5mm
AIRBORNE CONSIDERATIONS
February, 2011 IAQA CONFERENCE 21
• Air layer closest to substrate is referred to as laminar
layer
• Negligible air movement
• Can be a few millimeters in depth to centimeters in
depth
SPORE/CONIDIAL RELEASE
February, 2011 IAQA CONFERENCE 22
• Most ascomycetes and basidiomycetes on wood substrates do not release spores in low humidity
• Most ascomycetes and basidiomycetes eject spores
• Many moulds such as Cladosporium and Penicillium have no active release mechanism, but are easily detached
• Asp/Pen group will release spores in 0.5 m/sec air flow
• Cladosporium spp. release spores in 1.5 m/sec air flow
RELEASE INTO AIR
February, 2011 IAQA CONFERENCE 23
• Release must be in moving air above laminar layer
• Active ejection of spores or release from above
ground/substrate level
• Project sporangiophore or conidiophore above laminar air
layer
• Air movement as low as 0.4 m/sec can cause
spores/conidia to become airborne
DISPERSAL PATTERN
February, 2011 IAQA CONFERENCE 24
Copied from Dr. Wong,
U of Hawaii
MUSHROOM SPORES
• Studies of spores released from mushroom caps indicates
that many drop almost straight down at 0.8 to 3.6 mm/sec
while some may travel 40 meters downwind on air currents
of 1.5 m/sec (Deering et al., 2001)
February, 2011 IAQA CONFERENCE 25
COLLECTION OF FUNGAL
BIOAEROSOLS
February, 2011 IAQA CONFERENCE 26
• Spore trap and other impactor collection devices have inherent limitations
• IEQ evaluations routinely set collection device at ‘breathing height’ above the floor
• Concept of bioaerosol dispersal
• Location of bioaerosol source
• Ambient relative humidity
• Air turbulence patterns within the collection area
FALL RATE OF SPORES/CONIDIA
February, 2011 IAQA CONFERENCE 27
• Ingold suggests that most airborne spores are 10mm or
less in aerodynamic diameter with a fall rate of less than 1
cm/sec
• (about 4 hours for 6 foot fall)
• Fall rate for spherical spores in still air is governed by
Stokes’ Law
• V = 2/9 x q-P/m x gr2
STOKES’ LAW
V = 2/9 x d – P /m x gr2
• V = steady velocity in cm/sec
• d = density of spore (1.0)
• P = density of air (1.0)
• g = acceleration due to gravity
• m = viscosity of air
• r = radius of spore
February, 2011 IAQA CONFERENCE 28
Scopularia spp. –by Dave Spero
STOKES’ LAW
• Measurements of 4mm spores of Lycoperdon = 0.05
cm/sec
• Spores of Stachybotrys are calculated to settle at a rate
or 1.9 mm/sec, in still air (or 1 meter in 9 minutes)
• Spores of Aspergillus are calculated to settle at a rate of
0.3 mm/sec, in still air
February, 2011 IAQA CONFERENCE 29
COMMON NATURAL FUNGAL
BIOAEROSOLS
February, 2011 IAQA CONFERENCE 30
• Common conidia of mould taxa recovered outdoors:
• Cladosporium herbarum, Alternaria spp., Botrytis spp.,
Epicoccum spp.
• Basidiospores common in summer and autumn
• Phylloplane fungi commonly identified in analyses of total
countable fungal bioaerosol samples
• Stachybotrys spores require strong air turbulence (1.6
m/sec air flow) to release 0.1% of conidia; 99% reduction
in spore release after 5 minutes
COMMON MOULDS
February, 2011 IAQA CONFERENCE 31
• Species of Cladosporium, Penicillium, Aspergillus, and
Botrytis exhibit long conidiophore stalks that raise
conidial masses above laminar layer of air
• Spore release appears to correlate with slight vibrations or
air turbulence
• Spore release appears greatest in low relative humidity (micro niche measurements?)
STUDY DATA
February, 2011 IAQA CONFERENCE 32
• In general, spores of Cladosporium herbarum, Penicillium spp., and Chaetomium spp. are 2 – 60 mm in diameter
• May require ‘mist’ (e.g., morning dew or rain) to aid release
• Periodicity of spore release suggests circadian rhythm related to temperature and relative humidity
• Often mid-summer peak
• Usual mid-day peak
STUDY DATA
February, 2011 IAQA CONFERENCE 33
• Study in Oklahoma (Burch and Levitan, 1998) determined a correlation between spore release, in outdoor settings, by common moulds ambient climatic conditions such as temperature and relative humidity
• Bioaerosol concentrations of ascospores and basidiospores appear to peak in before dawn, with increase in humidity
• Bioaerosol concentrations of phylloplane moulds (e.g., species of Cladosporium) peak mid-morning in warm, dry weather
STUDY DATA
February, 2011 IAQA CONFERENCE 34
• Kansas study indicated release of Cladosporium spores peaked mid-morning in relation to increased ambient temperature, decrease in relative humidity, and ripening of conidia (i.e., maturation)
• Fungal colonies may produce spores in 106 to 109 quantities
• Dr. Kendricks estimated 4 X 106 spores released from a 1 inch diameter colony of Penicillium spp. at first air movement
• Fungal spores may be carried 1 meter to >500 km from source
INDOOR CONSIDERATIONS
February, 2011 IAQA CONFERENCE 35
• Saprophytic fungi can and do grow in indoor
environments, even without significant water damage or
moisture content
• Horner, et al. 2004; Cooley et al. 1998
• Indoor environment commonly climate controlled by
HVAC systems
• Ambient indoor temperature and RH change hourly
and daily
• Air turbulence by indoor activity and HVAC air
handler operation
INDOOR BIOAEROSOLS
February, 2011 IAQA CONFERENCE 36
• Anecdotal collection data from Dr. George Wong (U of Hawaii)
• Serial collection of fungal bioaerosols using culture plates in same location indicated fewer spores trapped after first collection (85 CFU in first plate to 20 CFU on fourth plate)
• Air eddies and turbulence in buildings with central HVAC keeps fungal conidia airborne
• Estimated fungal bioaerosol concentrations change over time and by location of sampling device
EVALUATION OF IEQ BIOAEROSOL
DATA
February, 2011 IAQA CONFERENCE 37
• Considerations:
• Limitations of collection technique
• Location of sample collection
• Number of sample locations and samples per location
• Correlation to IAQ parameters (temp and RH)
• Nature of various release mechanisms
• Time of sampling
• Number of and time of outdoor samples
EVALUATION OF IEQ BIOAEROSOL
DATA
February, 2011 IAQA CONFERENCE 38
• Considerations
• Operation of AFD in a contained remediation site
• Movement within a still air site
• Rate of fall for common conidia and spores
• Types of spores/conidia that may be airborne
• Stachybotrys spores do not readily become airborne
• Stachy spores may become airborne after desiccation
GENERAL REFERENCES
February, 2011 IAQA CONFERENCE 39
• Burnett, J. H. and A.P.J. Trinici. Eds. 1979. Fungal Walls and Hyphal Growth. Cambridge Univ. Press.
• Gravesen, S. et al. 2001. Microfungi. Munksgaard.
• Ingold, C. T. 1971. Fungal Spores. Their liberation and dispersal. Clarendon Press.
• Ingold, C. T. 1973. The Biology of the Fungi. 2nd Ed. Hutchinson educational Ltd.
• Kendrick, B. 2002. The Fifth Kingdom. 3rd Ed. R. Pullins Co.
• Kirk, P. M. et. al. Eds. 2001. Dictionary of the Fungi. 9 th Ed. CABI Bioscience.
• Medlin, M. F. Ed. 1966. The Fungus Spore. Butterworth.
• Watanabe, T. 1994. Pictorial Atlas of Soil and Seed Fungi. Lewis Publishers
QUESTIONS ??
February, 2011 IAQA CONFERENCE 40
• Please wake the person next to you before you leave.
• Contact for copy of presentation:
• IAQA website or