FACTORS OF FUNGAL SPORE DISPERSAL AND INDOOR BIOAEROSOLS. Alan J. Neumann, Ph.D. Indoor Ecology Associates Inc.

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1 FACTORS OF FUNGAL SPORE DISPERSAL AND INDOOR BIOAEROSOLS Alan J. Neumann, Ph.D. Indoor Ecology Associates Inc.

2 INDOOR ENVIRONMENTAL QUALITY ASSESSMENTS 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 2

3 RELATION OF FUNGAL SPORE DISPERSAL TO INDOOR ENVIRONMENTAL ASSESSMENT 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 3

4 TERMINOLOGY 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 4

5 TERMINOLOGY 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 5

6 CELL WALL STRUCTURE 6

7 TERMINOLOGY 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 7

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. 8

9 MYXOSTELIDA Slime moulds Stemonitis spp. Upper right macro of sporangia Lower right micro of reticulated interior wall of sporangium and spores 9

10 BASIDIOMYCETES Mushrooms are common basidiomycetes of lawns and woods Spores borne on gill or pore walls of cap 10

11 BASIDIOMYCETES SEM micrograph of bolete spores 11

12 BASIDIOMYCETES Copied from Dr. Wong U of Hawaii 12

13 DEUTEROMYCOTINA Penicillium atramentosom By David Spero 13

14 DEUTEROMYCOTINA Memnoniella spp. - UNLV 14

15 DEUTEROMYCOTINA Memnoniella echinata Copied from Campbell,

16 DEUTEROMYCOTINA Memnoniella echinata and Stachybotrys chartarum Copied from Haugland et al,

17 DEUTEROMYCOTINA Stachybotrys spp. SUNY ESF 17

18 CONSIDERATIONS OF SPORE DISPERSAL CRITERIA 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 18

19 TERMINOLOGY 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 19

20 SPORE/CONIDIA CHARACTERISTICS 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, X 2-3.5mm 20

21 AIRBORNE CONSIDERATIONS 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 21

22 SPORE/CONIDIAL RELEASE 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 22

23 RELEASE INTO AIR 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 23

24 DISPERSAL PATTERN Copied from Dr. Wong, U of Hawaii 24

25 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) 25

26 COLLECTION OF FUNGAL BIOAEROSOLS 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 26

27 FALL RATE OF SPORES/CONIDIA 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 gr 2 27

28 STOKES LAW 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 V = 2/9 x d P /m x gr 2 Scopularia spp. by Dave Spero 28

29 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 29

30 COMMON NATURAL FUNGAL BIOAEROSOLS 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 30

31 COMMON MOULDS 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?) 31

32 STUDY DATA 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 32

33 STUDY DATA 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 33

34 STUDY DATA 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 10 6 to 10 9 quantities Dr. Kendricks estimated 4 X 10 6 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 34

35 INDOOR CONSIDERATIONS Saprophytic fungi can and do grow in indoor environments, even without significant water damage or moisture content Horner, et al. 2004; Cooley et al 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 35

36 INDOOR BIOAEROSOLS 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 36

37 EVALUATION OF IEQ BIOAEROSOL DATA 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 37

38 EVALUATION OF IEQ BIOAEROSOL DATA 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 38

39 GENERAL REFERENCES Burnett, J. H. and A.P.J. Trinici. Eds Fungal Walls and Hyphal Growth. Cambridge Univ. Press. Gravesen, S. et al Microfungi. Munksgaard. Ingold, C. T Fungal Spores. Their liberation and dispersal. Clarendon Press. Ingold, C. T The Biology of the Fungi. 2 nd Ed. Hutchinson educational Ltd. Kendrick, B The Fifth Kingdom. 3 rd Ed. R. Pullins Co. Kirk, P. M. et. al. Eds Dictionary of the Fungi. 9 th Ed. CABI Bioscience. Medlin, M. F. Ed The Fungus Spore. Butterworth. Watanabe, T Pictorial Atlas of Soil and Seed Fungi. Lewis Publishers 39

40 QUESTIONS?? Please wake the person next to you before you leave. Contact for copy of presentation: IAQA website or 40