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Fungal Contamination as a Major Contributor to
Sick Building Syndrome
DE-WEI LI AND CHIN S. YANG
P & K Microbiology Services, Inc., 1936 Olney Ave
Cherry Hill, New Jersey 08003
I. Introduction 31
II. Effects of Indoor Fungi on Human Health 32
A. Fungal Allergies and Allergenic Respiratory Diseases 32
B. Infectious Diseases 42
C. Mycotoxins and Their Significance to Human Health 50
D. Volatile Organic Compounds (VOCs) 59
E. Glucans 62
III. Indoor Fungi 63
A. Fungal Identification 63
B. Airborne Fungi 64
C. Fungi Growing on Indoor/Building Materials 72
D. Fungal Biodiversity Indoors 74
E. Stachybotrys chartarum and Other Stachybotrys spp. 74
F. PCR and Molecular Techniques 77
IV. Ecological Factors of Fungi Indoors 78
A. Physical Factors 78
B. Building Characteristics 86
C. Succession and Changes in Indoor Fungi 91
V. Recent Studies on Limits/Exposures of Indoor Fungi 94
VI. Conclusions 96
References 97
I. Introduction
Fungi are heterotrophic eukaryotes producing exoenzymes and ab-
sorbing their nutrients by a network of hyphae and reproducing
through development of spores. They belong to Kingdom Eumycota
(Kingdom of Fungi) or Kingdom Chromista (Kendrick, 2000). However,
there is one group of organisms, which are traditionally studied by
mycologists, called pseudofungi (such as slime molds in myxomy-
cetes), that belong to Kingdom Protozoa (Kirk et al., 2001). Fungi are
a very large, diverse, and heterogeneous group of organisms found in
nearly every ecological niche (Alexopoulos et al., 1996). They play a
very important role in our ecosystem and our daily life. Fungi always
play dual roles on the earth: (a) a positive one as food, medicine, key
components in food processing, decomposers breaking down organic
matters to recycle the nutrients in the ecosystem and to form symbiotic
31
ADVANCES IN APPLIED MICROBIOLOGY, VOLUME 55
Copyright 2004, Elsevier Inc.
All rights reserved.
0065-2164/04 $35.00
relationship with other organisms; (b) a negative one as pathogens to
humans, plants, and animals; as allergens, producing secondary meta-
bolites, mycotoxins, fungal volatile organic compounds (VOCs); and as
glucans, which are detrimental to human health and building occu-
pants (Batterman, 1995; Ezeonu et al., 1994; Miller, 1992, 1993). A large
number of fungi are saprophytes or decomposers, which mainly occur
in natural environments (outdoors) such as soil and plant debris. Some
of these fungi can be found in indoor environments. One key factor that
we should keep in mind is that most indoor fungi originate from the
outdoor environment. Certain indoor fungal contaminants pose a po-
tential health risk to building occupants and may lead to sick building
syndrome (Gravesen et al., 1994; Miller, 1992, 1993; Samson et al.,
1994). Indoor fungi have attracted unprecedented attention because
of their potential health effects on humans in the last decade. Public
awareness of indoor fungi in return generates more research to eluci-
date their roles in indoor environments and human health. Indoor
fungus is not only a scientific issue but is also becoming a social issue.
Public awareness does not automatically mean a good understanding of
the indoor molds. There are still many key questions that need to be
answered to have a better understanding of the indoor mold issue.
This chapter reviews available literature on fungal contamination as
a major contributor to sick building syndrome.
II. Effects of Indoor Fungi on Human Health
A. FUNGAL ALLERGIES AND ALLERGENIC RESPIRATORY DISEASES
Allergy (Gk allos, other; ergon, work) is a disease or reaction caused
by an immunoglobin E (IgE)-mediated immune response to one or more
environmental agents, resulting in tissue inflammation and organ dys-
function, and an exaggerated and pathological variant of a normal
immune mechanism (Klein, 1990; Middleton, Jr. et al., 1988; Paul,
1989; Raven and Johnson, 1986). Fungal spores are a well known cause
of allergic diseases (Chapman, 1999; Gravesen, 1979; Horwitz and
Bush, 1997) and were identified as one of the major indoor allergens
(Burr, 1999; Pope et al., 1993; Ruotsalainen et al., 1995). Allergy is
common throughout the world. The prevalence of sensitivity to specif-
ic allergens is determined by both genetic predilection and geographic
and cultural factors responsible for exposure to the allergen (Stites and
Terr, 1991).
All fungi may be allergenic, depending on the individual, the
exposure situation, and the dose (Ruotsalainen et al., 1995). The genera
32 LI AND YANG
of fungi, which have been reported to be allergenic, are compiled in
Table I. Since the late 1870s, when Blakeley developed symptoms of
bronchial asthma and ‘‘chest tightness’’ after inhaling spores from
Penicillium cultures, it has been believed that mold sensitization is
an important cause of respiratory allergy (Barth, 1981; Karlsson-Borga
˚,
1989; Salvaggio, 1986).
Allergy is perhaps the most common human reaction to airborne
fungal spores (including conidia). About 20% of the population are
allergic individuals with a genetic predisposition to produce IgE anti-
body to allergens that are either inhaled or ingested (Kaplan et al.,
1991; Tizard, 1988). The percentages of populations allergic to molds
vary from 2% to 18%, and around 80% of asthmatic patients are
allergic to molds (Flannigan et al., 1991). About 20% of the population
are atopic and easily sensitized by concentrations usually found in the
outdoor air spora (up to 10
6
spores/m
3
). These people react immediate-
ly on exposure in the upper airways with hay-fever-like symptoms or
asthma and may become sensitive to several of the allergens to which
they are exposed. The remainder of the population requires more
intensive exposure (10
6
–10
9
spores/m
3
) for sensitization (Lacey, 1981).
The incidence and prevalence of allergic diseases is increasing
(Ruotsalainen et al., 1995). Allergies affect as many as 50 million
people in the United States, costing them up to $5 billion annually
(Jaroff, 1992), and the number is obviously much higher at present.
Asthma, rhinitis, hypersensitivity pneumonitis, and humidifier lung
are allergenic respiratory diseases that, to a certain degree, may be
related to exposure to airborne fungi.
Asthma is the most common chronic respiratory disease in all
countries. Both the severity and prevalence of persistent asthma ap-
pear to be increasing, leading to urgency in the search for its causes
(Woolcock, 1991). Four thousand people a year reportedly died from
allergic asthma attack in the United States (Jaroff, 1992). In Australia,
asthma mortality rates doubled from 1978 to 1988 (Young et al., 1991).
Immediate-type asthma symptoms were produced with both whole
spores and spore extracts of Alternaria and Penicillium (Licorish et al.,
1985; Salvaggio, 1986). Airborne fungal spores are ubiquitous (Howard,
1984) and are known in many cases to be allergenic, so it is not
surprising that mold spores are an important cause of asthma. At
present the relationship between mold spores and asthma is still poorly
understood. In Madison, Wisconsin, in a series of 100 consecutive
patients with allergic asthma, skin tests were uniformly positive to
Alternaria (Reed, 1985). Most of these patients had asthma symptoms
not only before and after the ragweed season (about August 10 to
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 33
TABLE I
FUNGAL GENERA REPORTED TO BEASSOCIATED WITH ALLERGY
Fungus Order Division
Absidia Mucorales Zygomycota
Acremonium Hyphomycetes
Acrogenospora Hyphomycetes
Acrothecium Hyphomycetes
Agaricus Agaricales Basidiomycotina
Agrocybe Agaricales Basidiomycotina
Alternaria Hyphomycetes
Amanita Agaricales Basidiomycotina
Armillaria Agaricales Basidiomycotina
Arthrinium Hyphomycetes
Aspergillus Hyphomycetes
Aureobasidium Hyphomycetes
Bispora Hyphomycetes
Boletinellus Boletales Basidiomycotina
Boletus Boletales Basidiomycotina
Botrytis Hyphomycetes
Calvatia Lycoperdales Basidiomycotina
Candida Yeast
Cantharellus Aphyllophorales Basidiomycotina
Chaetomium Sordariales Ascomycotina
Chlorophyllum Agaricales Basidiomycotina
Cladosporium Hyphomycetes
Claviceps Hypocreales Ascomycotina
Coniosporium Hyphomycetes
Coprinus Agaricales Basidiomycotina
Coriolus Aphyllophorales Basidiomycotina
Cryptococcus Hyphomycetes
Cryptostroma Hyphomycetes
Cunninghamella Mucorales Zygomycota)
Curvularia Hyphomycetes
Dacrymyces Dacrymycetales Basidiomycotina
Daldinia Xylariales Ascomycotina
Debaryomyces Saccharomycetales (Yeast) Ascomycotina
Dicoccum (Trichocladium) Hyphomycetes
(continued)
34 LI AND YANG
TABLE I (Continued )
Fungus Order Division
Didymella Dothideales Ascomycotina
Drechslera Hyphomycetes
Epicoccum Hyphomycetes
Epidermophyton Hyphomycetes
Erysiphe Erysiphales Ascomycotina
Eurotium Eurotiales Ascomycotina
Fomes Aphyllophorales Basidiomycotina
Fuligo Myxomycetes
Fusarium Hyphomycetes
Ganoderma Aphyllophorales Basidiomycotina
Geastrum Lycoperdales Basidiomycotina
Geotrichum Hyphomycetes
Gibberella Hypocreales Ascomycotina
Gliocladium Hyphomycetes
Gnomonia Diaporthales Ascomycotina
Graphium Hyphomycetes
Helminthosporium Hyphomycetes
Hypholoma Agaricales Basidiomycotina
Inonotus Aphyllophorales Basidiomycotina
Leptosphaeria Dothideales Ascomycotina
Leptosphaerulina Dothideales Ascomycotina
Lycoperdon Lycoperdales Basidiomycotina
Malassezia Hyphomycetes
Merulius (=Phlebia) Basidiomycotina
Microsphaera Erysiphales Ascomycotina
Microsporum Hyphomycetes
Monilia Hyphomycetes
Mucor Mucorales Zygomycota
Mycogone Hyphomycetes
Naematoloma Agaricales Basidiomycotina
Neurospora Sordariales Ascomycotina
Nigrospora Hyphomycetes
Oidium Hyphomycetes
Paecilomyces Hyphomycetes
Papularia Hyphomycetes
(continued)
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 35
Penicillium Hyphomycetes
Phoma Coelomycetes
Phycomyces Mucorales Zygomycota
Phytophthora Peronosporales Oomycota
Piptoporus Aphyllophorales Basidiomycotina
Pisolithus Sclerodermatales Basidiomycotina
Pleospora Dothideales Ascomycotina
Pleurotus Aphyllophorales Basidiomycotina
Podaxis Podaxales Basidiomycotina
Polyporus Aphyllophorales Basidiomycotina
Poria Aphyllophorales Basidiomycotina
Psilocybe Agaricales Basidiomycotina
Puccinia Uredinales Basidiomycotina
Rhizopus Mucorales Zygomycota
Rhodotorula Yeast Basidiomycotina
Saccharomyces Endomycetales (Yeast) Ascomycotina
Scleroderma Sclerodermatales Basidiomycotina
Scopulariopsis Hyphomycetes
Serpula Aphyllophorales Basidiomycotina
Sphaerotheca Erysiphales Ascomycotina
Spondylocladium Hyphomycetes
Sporobolomyces Yeast Basidiomycotina
Sporotrichum Hyphomycetes
Stachybotrys Hyphomycetes
Stemonitis Myxomycetes
Stemphylium Hyphomycetes
Stereum Aphyllophorales Basidiomycotina
Syncephalastrum Mucorales Zygomycota
Tetracoccosporium Hyphomycetes
Thermomyces Hyphomycetes
Tilletiopsis Hyphomycetes
Tilletia Basidiomycotina
Torula Hyphomycetes
Trichoderma Hyphomycetes
Trichophyton Hyphomycetes
(continued)
TABLE I (Continued )
Fungus Order Division
36 LI AND YANG
September 20) but also during the time of year Alternaria spore counts
are high (July through October) (Reed, 1985). Cladosporium herbarum
has been shown to be a potential cause of allergic asthma and rhinitis
(Malling, 1990).
In a recent study, the prevalence of most building-related symptoms
was between 32% and 62%. Positive basophile histamine release
(HRT), showing serum IgE specific to one or more of the molds, was
observed in 37% of the individuals (Lander et al., 2001). The highest
frequency of positive HRT was found to Penicillium chrysogenum and
then to Aspergillus species, Cladosporium sphaerospermum, and Sta-
chybotrys chartarum (Lander et al., 2001). Savilahti et al. (2000)
showed that moisture damage and exposure to molds increased the
indoor air problems of schools and affected the respiratory health of
children.
Cladosporium, Alternaria, Penicillium, Aspergillus, and Mucor were
reported to be the commonest allergenic fungi (Furuuchi and Baba,
1986; Malling et al., 1985). Cladosporium is believed to be the most
common one causing mold allergy (Malling et al., 1985). However, the
most prevalent airborne fungi are not necessarily the most potent
allergens, at least as determined by prick testing (Terracina and Rogers,
1982). Spores of Alternaria alternata and those of the closely related
genera Stemphylium and Ulocladium are considered to be the most
important mold allergens in the United States (Hoffman, 1984;
O’Hollaren et al., 1991; Reed, 1985). Penicillium exposure was a risk
factor for asthma, while Aspergillus exposure was a risk factor for atopy
(a genetic trait of increased allergen sensitivity) (Garrett et al., 1998).
Trichothecium Hyphomycetes
Typhula Aphyllophorales Basidiomycotina
Urocystis Basidiomycotina
Ustilago Ustilaginales Basidiomycotina
Verticillium Hyphomycetes
Wallemia Hyphomycetes
Xylaria Xylariales Ascomycotina
Xylobolus Aphyllophorales Basidiomycotina
Chapman (1986); Ibanez et al. (1988); Latge
´and Paris (1991); Santilli et al. (1990); Shen et al.
(1990); Smith (1990); Van Bronswijk et al. (1986).
TABLE I (Continued )
Fungus Order Division
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 37
Chow et al. (2000) characterized Pen n 13 as a major allergen of Peni-
cillium notatum (a synonym of P. chrysogenum).
Aspergillus restrictus was demonstrated to be a potentially important
causative agent in atopic diseases when using skin prick tests and
radioallergosorbent test (RAST) on 24 patients (Sakamoto et al., 1990).
Aspergillus species and in particular Aspergillus fumigatus appeared to
be the etiological agents in various lung diseases and allergens. Inhala-
tion of low doses of Aspergillus spores may induce sensitization and
asthma in sensitive patients, while inhalation of high doses may trigger
alveolitis and farmer’s lung (Wallenbeck et al., 1991). Martinez Ordaz
et al. (2002) of Mexico found that the association of skin reactivity and
indoor exposure was significant only for Aspergillus.
Curvularia lunata was found to be a cause of allergic bronchopul-
monary disease (Halwig et al., 1985). Epicoccum nigrum was reported
to be able to colonize nasal sinuses and cause allergic fungal sinusitis
(Noble et al., 1997). Sooty molds caused allergies ranging from rhinitis
to asthma in the eastern United States (Santilli et al., 1985).
Ascospores are important airborne allergens and present unique
antigens (Eversmeyer and Kramer, 1987). Fifteen of 18 patients report-
edly reacted to Leptosphaeria ascospores (Burge, 1986). About 40% of
atopic patients reacted to at least 1 ascomycete preparation. Chaeto-
mium species, particularly C. globosum, are important ascomycetes
commonly found growing indoors on water-damaged paper and wood
products.
Basidiospores of Agaricus campestris, Coprinus micaceus, Lycoper-
don perlatum, Scleroderma lycoperdoides, and Ustilago maydis
caused allergies ranging from rhinitis to asthma in the eastern United
States (Santilli et al., 1985). Basidiospores are antigenic and can elicit
immediate skin reactivity in sensitive patients. Mushrooms and basi-
diospores are considered most likely to be of outdoor origin, although
mycelia and conidia of wood decay fungi and, occasionally, mush-
rooms of the genus Coprinus and wood decay fungi have been identi-
fied in indoor environments with a chronic water-damage history.
In a military hospital building in Finland with severe, repeated, and
enduring water and mold damage, the most abundant species was
Sporobolomyces salmonicolor. Four new cases of asthma, confirmed
by S. salmonicolor inhalation provocation tests, were found among the
hospital personnel, one of whom was also found to have alveolitis
(Seuri et al., 2000). Seven other workers with newly diagnosed rhinitis
reacted positively in nasal S. salmonicolor provocation tests. Skin
prick tests of Sporobolomyces were negative among all 14 workers
(Seuri et al., 2000).
38 LI AND YANG
Several epidemiologic studies concerning water damage, fungal
growth, and exposure to mold spores have been conducted in a number
of countries. The occurrence of Cladosporium, Aspergillus versicolor,
and Stachybotrys showed some value as an indicator of moisture dam-
age. Presence of moisture damage in school buildings was a significant
risk factor for respiratory symptoms in school children (Meklin et al.,
2002). The association between moisture damage and respiratory
symptoms of children was significant for buildings of concrete/brick
construction but not for wooden school buildings. The highest symp-
tom prevalence was found during spring seasons, after a long exposure
period in damaged schools (Meklin et al., 2002).
Questionnaire surveys conducted in the United Kingdom,
Canada, United States, and the Netherlands showed positive correla-
tions between self-reported allergenic respiratory symptoms and
self-reported water damage and indoor fungi problems (Andrae et al.,
1988; Brunekreef, 1989; Dales et al., 1991a; Dekker et al., 1991; Melia
et al., 1982; Strachan, 1988; Strachan and Sanders, 1989; Strachan
et al., 1990; Waegemaekers et al., 1989). Most studies identified an
association between airborne fungal spore concentrations and self-
reported allergic symptoms in the United Kingdom, Sweden, and the
Netherlands (Holmberg, 1987; Platt et al., 1989; Strachan et al., 1990;
Waegemaekers et al., 1989), but there is not always a correlation be-
tween indoor spore counts and symptoms found in research (Tobin
et al., 1987).
Yang et al. (1997) showed that the prevalence of respiratory symp-
toms was consistently higher in homes with dampness than in non-
damp homes. Dampness in the home can be used as a strong predictor
of and a risk factor for respiratory symptoms and is a considerable
public health problem in Taiwan (Yang et al., 1997). A significant
relationship was found between dampness and work-related sick
building syndrome in day-care-center workers in Taiwan (Li et al.,
1997). A significant association was found between most building-
related symptoms (BRS) and positive basophil histamine release
(Lander et al., 2001). Jacob et al. (2002) found that mold spore counts
for Cladosporium and Aspergillus were associated with an increased
risk of allergic sensitization. Sensitized children exposed to high levels
of mold spores (>90th percentile) were more likely to suffer from
symptoms of rhinoconjunctivitis. Fungal allergies were more common
among children exposed to Cladosporium or Penicillium in winter or to
musty odor (Garrett et al., 1998).
In atopic children, total IgE showed a significant linear relation with
age. Prevalence of specific IgE for Cladosporium ranked first, followed
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 39
closely by Aspergillus and Alternaria (Nolles et al., 2001). Sensitization
to fungi is prevalent in childhood, with an age-dependent distribution
reaching maximum values at 7.7–7.8 years, followed by a decline for all
fungal sensitization with increasing age (Nolles et al., 2001).
Jaakkola et al. showed that the risk of asthma was related to the
presence of visible mold and/or mold odor in the workplace but not
to water damage or damp stains alone. The fraction of asthma attribut-
able to workplace mold exposure was estimated to be 35.1% among the
exposed (Jaakkola et al., 2002). Large airborne fungal spore concentra-
tions were recorded in association with musty odor, water intrusion,
high indoor humidity, limited ventilation through open windows, few
extractor fans, and failure to remove indoor mold growth in the homes
in the Latrobe Valley, Victoria, Australia (Garrett et al., 1998).
Aspergillus was associated strongly with work-related sick building
syndrome in day-care-center workers (Li et al., 1997). The diagnosis of
sick building syndrome related diseases, such as asthma, rhinitis, and
allergic alveolitis, can be very difficult. In the study of Thorn et al.
(1996) the symptoms of a school teacher, who was working in a school
that had indoor air quality problems on and off for several years, were
first interpreted as pulmonary embolism and later as atypical sarcoido-
sis. However, 6 years later the diagnosis of the illness was revised to
chronic allergic alveolitis.
It is important to understand that even correlations do not necessari-
ly mean causal relations. Most studies on indoor airborne fungi were
conducted without taking allergic symptoms into account. Several
recent epidemiological studies have shown that long-duration indoor
exposure to certain fungi can result in hypersensitivity reaction and
chronic diseases. Mold spore levels comparable to outside background
levels are usually well tolerated by most people. Normal or ‘‘typical’’
indoor molds may vary depending on diurnal and seasonal patterns of
outdoor fungi, weather conditions, climate variations, and geographical
regions (Li and Kendrick, 1995a).
There are other diseases caused by airborne fungal allergens, such as
rhinitis, hypersensitivity pneumonitis, and humidifier lung (Burge,
1990b; Salvaggio, 1986). A number of occupational hypersensitivity
diseases of the lung can be implicated by fungi (Table II). Hypersensi-
tivity pneumonitis, also called extrinsic allergic alveolitis, is a well-
recognized occupational disease. Hypersensitivity pneumonitis caused
by inhalation of spores from the edible mushroom Pholiota nameko
was documented by Nakazawa and Tochigi (1989). A diagnosis of
hypersensitivity pneumonitis caused by an Aspergillus species was
made by Jacobs et al. (1989).Pleurotus ostreatus was defined to be an
40 LI AND YANG
allergen by Horner et al. (1988). Extrinsic allergic alveolitis caused by
spores of Pleurotus ostreatus was reported by Cox et al. (1988).
In general, the adverse effects of fungal exposure by inhalation are
related to duration and intensity. Many studies have shown that ‘‘atyp-
ical’’ mold spore levels in the indoor environment increase because of
recurrent water leaks, home dampness, and high humidity, resulting in
increases of allergies and respiratory problems (Burge, 1990a,b; Dales
et al., 1991; Flannigan et al., 1991; Johanning et al., 1993; Rylander,
1994; Solomon et al., 1978; Strachan et al., 1990; Streifel and Rhame,
1993; Tripi et al., 2000). Path analysis showed that indoor total fungal
spores, indoor Aspergillus/Penicillium, and the age of the residences
had significant direct effects on allergic symptoms (Li, 1994).
There are still significant methodological problems in the prepara-
tion and production of reliable allergen extracts from fungi as
TABLE II
FUNGI-IMPLICATED OCCUPATIONAL HYPERSENSITIVITY DISEASES OF THE LUNG
Fungal agent Disease Source
Alternaria sp. Pulpmill worker’s lung Moldy pulpwood
Aspergillus clavatus Malt worker’s lung Moldy malt
Aspergillus fumigatus Wood trimmer’s disease Moldy timber
Aspergillus sp. Sawmill worker’s lung Moldy
Aspergillus sp. Woodchip handler’s disease Moldy woodchip
Aureobasidium pullulans Sauna taker’s lung Sauna steam
Aureobasidium pullulans Sequoiosis Moldy sawdust
Botrytis cinerea Vinegrower’s lung Moldy fruit
Farnai rectivirgula Potato riddler’s lung Straw
Cryptostrama corticale Maple bark disease Moldy maple bark
Graphium sp. Maple bark disease Moldy maple bark
Micropolyspora faeni Farmer’s lung Moldy hay
Micropolyspora faeni Mushroom worker’s lung Mushroom compost
Micropolyspora faeni Woodchip handler’s disease Moldy woodchip
Mucor sp. Woodchip handler’s disease Moldy woodchip
Penicillium casei Cheese worker’s lung Cheese
Penicillium spp. Suberosis, woodman’s disease Cork
Rhizopus sp. Wood trimmer’s disease Moldy timber
Rhizopus (Mucor) stolonifer Paprika worker’s lung Moldy paprika
Serpula (Merulius)lacrymans Dry rot lung Moldy building
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 41
compared with those from cats, dust mites, and other better-character-
ized allergens. Extracts that are available correspond poorly with the
fungi often found in indoor surveys (Horner and Lehrer, 1999). One of
the technical difficulties is to produce enough spores for allergen
extraction. Common practice in fungal allergen extraction is to use a
mixture of spores and mycelia, which was believed to be a contributing
factor to inconsistency in the low sensitivity of fungal allergenic tests.
Because of the low sensitivity of some of the commercially available
mold allergen extracts, false-negative results are not uncommon. Pa-
tients with an atopy are frequently allergic to multiple fungal species
and manifest type I reactions (asthma, rhinitis, eczema, and hay fever).
One of the reasons for the poor correlations is reportedly that fungal
allergens are extracted from mostly vegetative hyphae grown in liquid
cultures, not from spores. The differences in allergencity between
hyphae and spores should be studied.
B. INFECTIOUS DISEASES
Fungi are mostly known to cause not only allergies but also infec-
tious diseases to the skin and other body organs (Table III). Infections
caused by fungi are called mycoses. Mycoses are categorized into
endemic and opportunistic. Endemic mycosis is caused by the inhala-
tion of airborne fungal spores found in certain geographic regions
where there is a higher frequency of such fungi because of unique soil
and flora (Lacey, 1991; Pitt, 1979). Opportunistic fungal pathogens
have a great public health importance, especially in immune system
compromised individuals such as those with human immunodeficien-
cy virus (HIV) and organ transplants (Keller et al., 1999). These infec-
tions are not contagious, and the fungi are not obligatory pathogens.
Immunocompromised patients may be at an increased risk for oppor-
tunistic infections if opportunistic fungal pathogens become airborne
and their concentrations are significantly elevated in indoor air. The
major fungi causing mycosis and their medical significance are listed
in Table III.
Aspergillus fumigatus,A. flavus, and A. niger are among the fungi of
significant concern. Aspergillus fumigatus is the most important air-
borne pathogenic fungus (Brakhage and Langfelder, 2003) because of
its small respirable-size spores and its thermophilic nature (Klich and
Pitt, 1988). This is the very reason why A. fumigatus could cause a
significant problem in organ transplant wards in hospitals. Water dam-
aged materials, houseplants, soil, bird and bat droppings, organic
waste, or other organic substrates in buildings may be a source of these
42 LI AND YANG
TABLE III
PATHOGENIC FUNGI
Fungus Classification Disease Affected area
Absidia sp. Opportunistic
Systemic
mycosis
Zygomycosis
(Mucormycosis,
phycomycosis)
Face, sinuses,
gastrointestinal
tract, lungs
Cunninghamelia
sp.
Mortierella sp.
Mucor sp.
Rhizopus sp.
Syncephalastrum sp.
Basidobolus ranarum
Rhizomucor sp.
Conidiobolus
coronatus
Acremonium sp. Cutaneous
mycosis
Keratomycosis Eye
Subcutaneous
mycosis
Maduromycetoma
Opportunistic
Systemic
mycosis
Systemic
opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Alternaria sp. Opportunistic
Systemic
mycosis
Systemic
opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Arthrographis sp. Subcutaneous
mycosis
Dermatomycosis Skin
Aspergillus
fumigatus
Opportunistic
Systemic
mycosis
Aspergillosis Lung, skin,
mucocutaneous
tissue, any of the
body organs
Asp. flavus
Asp. niger
Asp. terreus
Asp. ustus
Aspergillus spp.
Aspergillus sp. Cutaneous
mycosis
Outer cutaneous
mycoses
Skin
Onychomycosis Nails
Otomycosis Ear
Keratomycosis Eye
(continued)
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 43
Aureobasidium
pullulans
Opportunistic
Systemic
mycosis
Systemic
opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Basidiobolus
sp.
Rare
subcutaneous
mycosis
Entomophthora
basidiobolae
Smooth skin
Beauveria
bassiana
Opportunistic
Systemic
mycosis
Systemic
opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Blastomyces
dermatitidis
Systemic
mycosis
Blastomycosis Primary infection in
lung, may spread to
all organs, skin
lesions are common
Candida
albicans
Cutaneous
mycosis
Intertriginous
candidosis
Moist skin areas: groin,
glans penis, scrotum,
folds of buttocks,
under the breast,
axilla, interdigital
spaces
Candida diaper
rash
Diaper area
Candidal
granuloma
Hands, feet, face, and
scalp
Candida
paronychia and
onychomycosis
Nails and skin around
nail
Mucocutaneoius
candidosis
Mucocutaneous areas
Thrush Mouth and tongue
Perleche Corners of mouth
Vaginal
candidosis
Vagina
Candida balinitis Glans penis
Esophageal
candidosis
Esophagus
Perianal
candidosis
Anal ara
Chronic
mucocutaneous
candidosis
Candida albicans,
Candida spp.
Cutaneous
mycosis
Onychomycosis Nails
(continued)
TABLE III (Continued )
Fungus Classification Disease Affected area
44 LI AND YANG
Opportunistic
Systemic
mycosis
Systemic
candidosis
Blood, heart tissue, kidney,
bladder, mucocutaneous
tissue (lungs are
colonized, but rarely
invaded)
Cutaneous
mycosis
Otomycosis Ear
Candida sp. Cutaneous
mycosis
Keratomycosis Eye
Cercospora
apii
Opportunistic
Systemic
mycosis
Systemic
Opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Chaetoconidium
sp.
Opportunistic
Systemic
mycosis
Systemic
Opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Chrysosporium
parvum
Opportunistic
Systemic
mycosis
Systemic
Opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Cladosporium
carrionii
Subcutaneous
mycosis
Chromomycosis Skin surface, mostly
lower extremities
Cladosporium
trichoides
Opportunistic
Systemic
mycosis
Cerebral
chromomycosis
Brain or central
nervous system
Coccidioides
immitis
Systemic
mycosis
Coccidioido-
mycosis
Primary infection in the
lung may spread to
other organs of the body;
skin lesion may be
produced
Coprinus sp. Miscellaneous
and rare
mycosis
Basidiomycosis
Cryptococcus
neoformans
Systemic
mycosis
Cryptococcosis Lungs, central nervous
system, skin, any
organ of body
Curvularia
geniculata
Opportunistic
Systemic
mycosis
Systemic
Opportunistic
fungal disease
Lungs, deep tissue,
body organs, blood
Drechslera
hawaiiensis
Opportunistic
Systemic
mycosis
Entomophthora
(conidiobolus)
coronata
Rare
subcutaneous
mycosis
Entomophthoro-
mycosis
conididobolae
Nasal tissue and face
(continued)
TABLE III (Continued )
Fungus Classification Disease Affected area
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 45
Epidermophyton
floccosum
Cutaneous
mycosis
Tinea cruris Groin
Tinea pedis Feet, interdigital
spaces, and soles
Tinea manuum Palms and fingers
Tinea unguium Nails
Epidermophyton
spp.
Cutaneous
mycosis
Dermatomycoses Keratinized layers of
body: skin, hair,
nails
Exophiala
(Phialophora)
jeanselmei
Subcutaneous
mycosis
Phaeomycotic
Cyst
Smooth skin
Exophiala
(Phialophora)
spinifera
Subcutaneous
mycosis
Phaeomycotic
Cyst
Smooth skin
Exophiala
jeanselmei
Subcutaneous
mycosis
Maduromycetoma
Fonsecaea
compactum
Subcutaneous
mycosis
Chromomycosis Skin surface, mostly
lower extremities
Fonsecaea
pedrosoi
Opportunistic
Systemic
mycosis
Cerebral
chromomycosis
Brain or central
nervous system
Fonsecaea
pedrosoi
Subcutaneous
mycosis
Chromomycosis Skin surface, mostly
lower extremities
Fusarium sp. Opportunistic
Systemic
mycosis
Fusarium sp. Cutaneous
mycosis
Keratomycosis Eye
Geotrichum
candidum
Opportunistic
Systemic
mycosis
Helmintho-
sporium sp.
Opportunistic
Systemic
mycosis
Hendersonula
sp.
Subcutaneous
mycosis
Dermatomycosis Skin
Histoplasma
capsulatum
Systemic
mycosis
Histoplasmosis Primary infection
in lung
(continued)
TABLE III (Continued )
Fungus Classification Disease Affected area
46 LI AND YANG
(H. duboisii in
Africa)
Recticulorendothelial
system is invaded; bone
and kidney and other
organs, including the
skin, may be involved
Hortaea
(Phaeoan-
nellomyces or
Exophiala)
werneckii
Superficial
mycosis
Tinea nigra Thick stratum corneum,
palms, and feet
Loboa loboi Rare
subcutaneous
mycosis
Lobomycosis Smooth skin
Malassezia
furfur
Superficial
infections
Pityriasis
versicolor
Microsporum
audouinii
Cutaneous
mycosis
Tinea capitis Scalp
M. canis
Microsporum spp.
Microsporum
canis
Cutaneous
mycosis
Tinea corporis Smooth body skin
M. gypseum
Microsporum spp.
Microsporum
spp.
Cutaneous
mycosis
Tinea barbae Beard and coarse body
hair
Tinea favosa Scalp, skin, and nails
Microsporum
spp.
Cutaneous
mycosis
Dermatomycoses Keratinized layers of
body: skin, hair, nails
Paecilomyces sp. Opportunistic
Systemic
mycosis
Paracoccidioides
brasiliensis
Systemic
mycosis
Paracoccidioido-
mycosis
Subclinical infection
in lung, mucous
membranes, and
skin are involved
Penicillium sp. Opportunistic
Systemic
mycosis
Pseudallescheria
(Allescheria or
Petriellidium),
boydii
Subcutaneous
mycosis
Maduromycetoma
(continued)
TABLE III (Continued )
Fungus Classification Disease Affected area
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 47
Phialophora
parasitica
Opportunistic
Systemic
mycosis
Subcutaneous
mycosis
Phaeomycotic
Cyst
Smooth skin
Phialophora
repens
Subcutaneous
mycosis
Phaeomycotic
Cyst
Smooth skin
Phialophora
richardsiae
Subcutaneous
mycosis
Phaeomycotic
Cyst
Smooth skin
Phialophora
verrucosa
Subcutaneous
mycosis
Chromomycosis Skin surface, mostly
lower extremities
Phoma
hibernica
Opportunistic
Systemic
mycosis
Phoma sp. Subcutaneous
mycosis
Phaeomycotic
Cyst
Smooth skin
Piadraia hortae Superficial
mycosis
Black piedra Scalp and beard
Pityrosporum
orbiculare
Superficial
mycosis
Tinea
versicolor
Smooth body skin
Pseudallescheria
(Allescheria or
Petriellidium),
boydii
Opportunistic
Systemic
mycosis
Pythium Miscellaneous
and rare
mycosis
Pythiosis
Rhinosporidium
seeberi
Rare
subcutaneous
mycosis
Rhinosporidiosis Nasal mucosa
Schizophyllum
commune
Miscellaneous
and rare
mycosis
Basidiomycosis
Scopulariopsis
brevicaulis
Opportunistic
Systemic
mycosis
Scopulariopsis sp. Cutaneous
mycosis
Onychomycosis Nails
Scytalidium sp. Subcutaneous
mycosis
Dermatomycosis Skin
(continued)
TABLE III (Continued )
Fungus Classification Disease Affected area
48 LI AND YANG
Sporothrix
schenckii
Subcutaneous
mycosis
Sporotichosis Skin, primarily hands,
arms, and legs
Torulopsis
glabrata
Opportunistic
Systemic
mycosis
Trichophyton
concentriucum
Cutaneous
mycosis
Tinea imbricate Smooth body skin
Trichophyton
rubrum
Cutaneous
mycosis
Tinea manuum Palms and fingers
T. mentagrophyte
Trichophyton spp.
Tinea pedis Feet, interdigital
spaces, and soles
Tinea unguium Nails
Tinea cruris Groin
Tinea corporis Smooth body skin
Trichophyton
schoenleinii
Cutaneous
mycosis
Tinea favosa Scalp, skin, and nails
Trichophyton spp.
Trichophyton
spp.
Cutaneous
mycosis
Dermatomycoses Keratinized layers of
body: skin, hair, nails
Trichophyton
tonsurans
Cutaneous
mycosis
Tinea capitis Scalp
Trichophyton spp.
Trichophyton
verrucosum
Cutaneous
mycosis
Tinea barbae Beard and coarse
body hair
T. mentagrophytes
Trichophyton spp.
Trichosporon
beigelii
Superficial
mycosis
White piedra Beard, scalp,
pubic hair
Wangiella
(Phialophora)
dermatitidis
Opportunistic
Systemic
mycosis
Cerebral
chromomycosis
Brain or central nervous
system
Subcutaneous
mycosis
Chromomycosis Skin surface, mostly
lower extremities
Maduromycetoma
Wangiella
mansonii
Superficial
mycosis
Tinea nigera Thick stratum corneum,
palms, and feet
Compiled from Campbell and Stewart (1980); Henry (1984); Howard (2003); Rippon (1988).
TABLE III (Continued )
Fungus Classification Disease Affected area
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 49
fungi (Benenson, 1990; Burge 1990a; Larsen and Frisvad, 1995).
These fungi can cause aspergillosis. In a hospital where an epidemic
of aspergillosis occurred, the source of Aspergillus spores was attrib-
uted to a defective disposal conduit door and the dispersal of a
contaminated aerosol from the ward vacuum cleaner, which had the
highest measured concentrations of Aspergillus fumigatus in or around
the building (65 colony forming units/m
3
as compared with 0–6 cfu/m
3
elsewhere). No further cases were identified in the hospital in
the 2 years after relevant hygiene arrangements were incorporated
(Anderson et al., 1996).
Other clinically important fungal infections include candidiasis
with local mucocutaneous or disseminated systemic organ manifesta-
tions and skin mycoses such as dermatophytoses, keratomycosis, tinea
nigra, piedra, and malassezia-caused dermatitis. Invasive fungal dis-
eases of the paranasal sinuses may also be associated with allergic
sinusitis in atopic patients (Fatterpekar, 1999). Aspergillus species
are frequently involved. Noninvasive forms may colonize body cavities
and may be asymptomatic as long as some degree of immunological
resistance can be maintained. Cryptococcus neoformans var. neofor-
mans was isolated from 20 (13%) dwellings out of 154 dwellings in the
metropolitan area of Rio de Janeiro, Brazil, comprising 5 (15.6%) of 32
dwellings of patients with AIDS-associated cryptococcosis (Passoni
et al., 1998).
Histoplasmosis is an intracellular mycotic infection of the reticuloen-
dothelial system caused by the inhalation of conidia from the fungus
Histoplasma capsulatum (Howard, 2003). Histoplasma capsulatum has
a worldwide distribution, but the Mississippi–Ohio River Valley in the
United States is a major endemic region, and the spore is occasionally
found in certain indoor environments there (Collier et al., 1998).
Coccidioides immitis causes coccidioiomycosis, a highly infectious
upper respiratory disease, and infection is caused by inhalation of its
airborne arthrospores (Howard, 2003). The disease is endemic in cer-
tain regions, mainly in desert soils and also in the air of endemic areas
in North America (Cox and Wathes, 1995). Exposure to dustborne
spores outdoors is the major risk factor of infection (Al-Doory and
Ramsey, 1987).
C. MYCOTOXINS AND THEIR SIGNIFICANCE TO HUMAN HEALTH
Another public health concern is mycotoxins produced by some
indoor fungi (Table IV). Fungi are capable of producing a number of
secondary metabolites (Nielsen, 2002). Most of these secondary
50 LI AND YANG
TABLE IV
COMMON MYCOTOXIGENIC INDOOR FUNGI
Fungus Mycotoxins*
Alternaria alternata Tenuazonic acid, alternatiol, alternatiol mononethyl ether,
altertoxins
Aspergillus flavus Aflatoxin B
1
Aspergillus fumigatus Gliotoxin, verrucologen, fumitremorgceusins, fumitoxins,
tryptoquivalins
Aspergillus niger Naphthopyrone, malformins, nigragillin, orlandin
Aspergillus
ochrrachceus
Ochratoxin A (a carcinogenic kidney toxin)
Aspergillus parasiticus Aflatoxin B
1
Aspergillus versicolar Sterigmatocystin and methoxysterigmatocystin
Aspergillus ustus Austaminde, austdiol, austins, austocystins, kotanins X and Y
Chaetomium globosum Chaetoglobosins, chetomin
Cladosporium
cladosporioides
Cladosporin, emodin
Emericella (Aspergillus)
nidulans
Sterigmatocystin, nudulotoxin
Fusarium culmorum T-2 toxin (immunosuppressive)
Fusarium graminearum Zealralenone
Fusarium verticillioides
(¼F. moniliforme)
Fumonisins
Memnoniella
echinata
Trichodermol, trichodermin, dechlorogrisseofulvins,
memnobotrins A and B, memenoconol, memnoconone
Paecilomyces variotii Patulin, viriditoxin
Penicillium
aurantiogriseum
Auranthine, penicillic acid, verrucosidin,
nephrotoxic glycopeptides
Mycophenolic acid
Penicillium
brevcompactum
Penicillium
chrysogenum
Roquefortine C, meleagrin, chrysogin, penicillin
Penicillium expansum Citrinin, patulin (nephrotoxic), cytotoxic metabolite
of unknown origin
Penicillium polonicum 3-methoxyviridicatin, verrucosidin, verrucofortine
Penicillium verrucosum Ochratoxin A (a carcinogenic kidney toxin)
Stachybotrys chartarum
(syn ¼S. atra).
Macrocyclic trichothecenes: satratoxins, verrucarins,
roridins, atranones, dolabellanes, stachybotrylactones,
and lactams
Trichoderma harzianum Alamethicins, emodin, suzukacillin, trichodermin
Wallemia sebi Walleminols A and B, walleminone
*Toxins in boldface are of high potency. Compiled in part from Al-Doory and Domson, 1984; Frank
et al., 1999; Macher et al., 1999; Samson, 2000; St-Germain and Summerbell, 1996.
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 51
metabolites are mainly to enhance the fitness of the fungi in nature.
However, when some of these chemical compounds cause detrimental
or toxic response in higher vertebrates at low concentrations, they are
referred to as mycotoxins (Nielsen, 2002). Mycotoxicosis is defined as
the disease resulting from exposure to a mycotoxin (CAST, 2003).
Mycotoxicosis may be acute or chronic. More occult disease may
occur when the mycotoxin interferes with the immune system and
leads to a compromised immune system so as to make patients more
susceptible to infectious diseases. Major mycotoxicoses include afla-
toxicosis, ochratoxicosis, trichothecene toxicoses, citreviridin toxico-
sis, zearalenone toxicosis, fumonisin toxicosis, gliotoxin toxicosis, and
immunomodulation.
Mycotoxins’detrimental effects on human health are at work
when they are ingested (CAST, 2003; Matossian, 1989), inhaled
(CAST, 2003; Croft et al., 1986; Johanning et al., 1993; Miller, 1993;
Smoragiewicz et al., 1993), or absorbed through skin contact (CAST,
2003; Dill et al., 1997; Singh, 1994). Historically, human exposure to
mycotoxins is mainly through ingestion of foodstuff containing or
contaminated with mycotoxins (CAST, 2003). However, because of
increases in public awareness of the health effects of indoor fungi,
inhalation of mycotoxin-containing spores of indoor fungi has become
a major public health concern in the indoor environment, and inges-
tion and dermal contact play a secondary role in indoor exposure.
There are reportedly more than 200 mycotoxins produced by various
common fungi, per the World Health Organization (WHO) Environ-
mental Health Criterion 105 on mycotoxins (Yang et al., 2002). Samson
(1992) and Smoragiewicz et al. (1993) suggested that there are more
than 400 toxic metabolites at present. The actual number of mycotoxins
is not known, but the number of fungal toxic metabolites could be
potentially in the thousands (CAST, 2003). With molecular masses
between 200 and 800 kDa (Smoragiewicz et al. 1993), mycotoxins are
not volatile at ambient temperatures (Tuomi et al. 2000). Schiefer
(1990) considered that mycotoxins generally have low volatility, and
therefore inhalation of volatile mycotoxins is not very likely. A task
group of WHO concluded that an association between trichothecene
exposure and human disease episodes is possible; however, only
limited data are available (Yang et al., 2002).
Major genera of toxigenic fungi include Aspergillus, Penicillium,
Fusarium, Stachybotrys, Memnoniella, and Claviceps (CAST, 2003).
There are other genera of mycotoxin-producing fungi. Species of 46
fungal genera have been reported to produce mycotoxins (Kendrick,
2000). Major classes of mycotoxins include aflatoxins, trichothecenes,
52 LI AND YANG
fumonisins, zearalenone, ochratoxin A, and ergot alkaloids
(CAST, 2003). Major toxigenic fungi and the mycotoxins produced,
as well as their health effects, are compiled in Tables V and VI.It
should be pointed out that some of the fungi in Table V are often found
indoors.
Mycotoxins are an integral part of the fungal spores or in association
with dust particles when released into the substrates. Water-damaged
building materials are often contaminated with fungi that produce
detectable levels of mycotoxins (Nikulin, 1999), which may be aero-
solized and contribute to pollution in indoor air. Sorenson et al. (1987)
showed that aerosolized conidia of S. chartarum (syn. S. atra)
TABLE V
FUNGI IMPLICATING SOME HUMAN DISEASES BECAUSE OF INVOLVEMENT OF THEIR MYCOTOXINS
Etiologic agent Disease Natural substrate
Fusarium spp. Akakabio-byo Wheat, barley, oats, rice
Fusarium spp. Alimentary toxic aleukia
(ATA or septic angina)
Cereal grains (toxic bread)
Penicillium Balkan nephropathy Cereal grains
Aspergillus spp.,
Penicillium spp.
Cardiac beriberi Rice
Sclerotinia Celery harvester’s
disease
Celery (pink rot)
Dendrodochium
toxicum
Dendrodochiotoxicosis Fodder (skin contact, inhaled
fodder particles)
Claviceps
purpurea
Ergotism Rye, cereal grains
Fusarium
moniliforme
Esophageal tumors Corn
Apergillus flavus,
A. parasiticus
Hepatocarcinoma
(acute aflatoxicosis)
Cereal grains, peanuts
Fusarium Kashin Beck disease,
‘‘Urov disease’’
Cereal grains
Aspergillus flavus,
A. parasiticus
Kwashiorkor Cereal grains
Phoma sorghina Onyalai Millet
Aspergillus Reye’s syndrome Cereal grains
Satchybotrys
chartarum
Stachybotryotoxicosis Hay, cereal grains, fodder (skin
contact, inhaled haydust)
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 53
TABLE VI
MYCOTOXINS AND THEIR PATHOLOGICAL EFFECTS ON HUMANS AND ANIMALS
Mycotoxin Substrates Affected species Pathological effects
Aflatoxins
(B1, B2, G1,
G2, M1, M2)
Peanuts, corn,
wheat, rice,
cottonseed,
copra, nuts,
various foods,
milk, eggs,
cheese, figs
Birds
Duckling,
turkey, poultry,
pheasant chick,
mature chicken,
quail
Mammals
Young pigs,
pregnant sows,
dog, calf,
mature cattle,
sheep, cat,
monkey, human
Hepatotoxicity
(liver damage)
Bile duct hyperplasia
Hemorrhage
Intestinal tract
Kidneys
Carcinogenesis
(liver tumors)
Fish
Laboratory
animals
Citrinin Cereal grains
(wheat, barley,
corn, rice)
Swine, dog,
laboratory
animals
Nephrotoxicity (tubular
necrosis of kidney)
porcine nephropathy
Cyclopiazonic
acid
Corn, peanuts,
cheese,
kodo millet
Chicken, turkey,
swine, rat,
guinea pig,
human
Muscle necrosis
Intestinal hemorrhage
and edema
Oral lesions
Ochratoxin A Cereal grains,
(wheat, barley,
oats, corn), dry
beans, moldy
peanuts, cheese,
grapes, dried
fruits, wine
Swine, dog,
duckling,
chicken, rat,
human
Nephrotoxicity (tubular
necrosis of kidney)
Porcine nephropathy
Mild liver damage
Enteritis
Teratogenesis
Carcinogenesis
(kidney tumors)
Urinary tract tumors
Patulin Moldy feed,
rotted apples,
apple juice,
wheat straw
residue
Birds
Chicken,
chicken embryo,
quail
Mammals
Cat, cattle,
mouse, rabbit,
rat, human
Edema
Brain
Lungs
Hemorrhage
Lungs
Capillary damage
Liver
(continued)
54 LI AND YANG
Others
Brine shrimp,
guppie, zebra
Fish larvae
Spleen
Kidney
Paralysis of
motor nerves
Convulsions
Carcinogenesis
Antibiotic
Penicillic
acid
Stored corn,
cereal grains,
dried beans,
moldy tobacco
Mouse, rat,
chicken embryo,
quail, brine
shrimp
Liver damage (fatty liver,
cell necrosis); kidney
damage; digitalis-like
action on heart dilates
blood vessels;
antidiuretic edema in
rabbit skin;
carcinogenesis;
antibiotic
Penitrem Moldy cream
cheese, English
walnuts,
hamburger
bun, beer
Dog, mouse,
human
Tremors, death,
icoordination, bloody
diarrhea
Sterigmatocystin Green coffee,
moldy wheat,
grains,
hard cheeses,
peas, cottonseed
Mouse, rat Carcinogenesis
Hepatotoxin
Trichothecenes
(T-2 toxin,
diacetoxyscirpenol,
neosolaniol,
nivalenol,
diacetylnivalenol,
deoxynicalenol,
HT-2 toxin,
fusarenon X)
Corn, wheat,
commercial
cattle feed,
mixed feed,
barley, oats
Swine, cattle,
chicken, turkey,
horse, rat, dog,
mouse, cat,
human
Digestive disorders
(emesis, diarrhea,
refusal to eat),
hemorrhage (stomach,
heart, intestines, lungs,
bladder, kidney), edema,
oral lesions, dermatitis,
blood disorders
(leucopenia)
Zearalenone Corn, moldy hay,
pelleted com-
mercial feed
Swine, dairy
cattle, chicken,
turkey, lamb,
rat, mouse,
guinea pig
Estrogenic effects
(edema of vulva,
prolapse of vagina,
enlargement of uterus)
Atrophy of testicles
Atrophy of ovaries,
enlargement of
mammary glands
Abortion
Compiled from CAST (2003).
TABLE VI (Continued )
Mycotoxin Substrates Affected species Pathological effects
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 55
contained trichothecene mycotoxins in the laboratory. The most com-
mon toxin was satratoxin H. Lesser amounts of satratoxin G and tricho-
verrols A and B were also detected, but less frequently. They also found
that most of the airborne particles were within respirable range. Similar
experiments, conducted by Pasanen et al. (1993), demonstrated that
trichothecene mycotoxins were in airborne fungal propagules of S.
chartarum (S. atra) and could be collected on membrane filters. Con-
idia of A. flavus and A. parasiticus were reported to contain aflatoxins
(Wicklow and Shotwell, 1983). Miller (1993) also reported detection of
two mycotoxins, deoxynivalenol and T-2 toxin, in conidia of Fusarium
graminearum and F. sporotrichioides, respectively. These references
suggest that inhalation exposure to conidia may also increase the
chance of exposure to mycotoxins.
Studies indicated that some secondary metabolites of indoor air-
borne fungi could be responsible for health problems of occupants
(Croft et al. 1986; Pieckova, 2002). Croft et al. (1986) identified several
cases of mycotoxicoses caused by airborne exposure to the toxigenic
fungus S. chartarum (syn. S. atra) in a residential building. Spengler
et al. (1993) reported that a higher rate of upper respiratory tract and
lung cancer occurred among workers with a high risk of inhalation of
fungi in the grain and food handling industry.
Important indoor toxigenic fungi include Stachybotrys chartarum
(syn. S. atra), Memnoniella echinata, Aspergillus species, Penicillium
species, Fusarium species, Trichoderma species, and Paecilomyces
species. These fungi are well documented to have associations with
detrimental health effects in humans and animals by ingestion. How-
ever, many toxigenic fungi—such as Stachybotrys chartarum and spe-
cies of Aspergillus,Penicillium, and Fusarium—have been found to
infest buildings with known indoor air problems and sick building
syndrome (Croft et al., 1986; Flannigan et al., 1991; Johanning et al.,
1993).
It should be pointed out that most mycotoxin studies were con-
ducted on post-harvest stored or processed food. For better indoor
environmental quality evaluation, it is important to know whether
indoor fungi are able to produce mycotoxin in building materials or
not and under what conditions. Tuomi et al. (2000) analyzed 17 myco-
toxins from 79 bulk building materials collected from water-damaged
buildings. Their results showed sterigmatocystin was present in 24%
of the samples, trichothecenes in 19% of the samples, and citrinine in 3
samples. Aspergillus versicolor was found on most sterigmatocysin-
containing samples, and Stachybotrys spp. were found on the samples
in which satratoxins were present (Tuomi et al., 2000).
56 LI AND YANG
Nielsen (2002) showed that Stachybotrys chartarum produced a
number of mycotoxins on building materials at levels significantly
higher than these products by other fungi. More importantly, he dis-
covered that only 35% of the isolates of S. chartarum produced the
extremely cytotoxic satratoxins. He opined that satratoxins might not
be responsible for idiopathic pulmonary hemosiderosis (IDPH) in in-
fants and that this disease may be caused by other mycotoxins pro-
duced by S. chartarum (Nielsen, 2002). Similar results showed that
39% of S. chartarum produced macrocyclic trichothecenes (Andersen
et al., 2002). The toxicity of the isolates producing macrocyclic tri-
chothecenes is 1000 times that of other isolates, which produce atro-
nones (Jarvis 2003, per. com.). However, a recent study in Belgium
showed that in 6 IDPH cases, the isolates of S. chartarum recovered
from patients’homes were all atronones producers (Nielsen, per. com.).
This association further raised the question whether other mycotoxins
and secondary metabolites are responsible for IDPH. To answer this
question there is no doubt that more research is necessary.
Aflatoxins are toxins discovered in 1961 from Aspergillus flavus and
A. parasiticus and considered human and animal carcinogens (CAST,
2003; International Agency for Research on Cancer, 1993). Aflatoxins
are potent liver toxins. A sublethal dose from exposure may result in
cancer (CAST, 2003). Aflatoxin-induced disease has been well docu-
mented and reviewed (Henry and Cole, 1993; International Agency for
Research on Cancer, 1993; Kurup, 1999). Aspergillus versicolor pro-
duced the mycotoxins sterigmatocystin and 5-methoxysterigmatocys-
tin, which are precursors of aflatoxins, in water-damaged materials
under field conditions and experimental conditions (Gravesen et al.,
1999; Nielsen, 2002). Trichothecene toxins inhibit protein and DNA
synthesis (CAST, 2003). The data of health effects on animals are
‘‘inadequate evidence’’ for humans (International Agency for Research
on Cancer, 1993). Macrocyclic trichothecenes, such as satratoxin H,
have not been classified. These toxins can cause alveolar macrophage
defects and may affect phagocytosis. They have been investigated for
use in cancer treatment (Goodwin et al., 1978) but also in chemical-
biological warfare.
In animal studies, all frequently isolated strains (Penicillium sp.,
Aspergillus versicolor,A. flavus,Cladosporium sphaerospermum,
and C. cladosporioides) in Slovakia produced secondary metabolites
with the strongest ciliostatic activity—their exo- and endometabolites
stopped tracheal ciliary movement in chicks for 24 h (Pieckova, 2002).
On building materials, Penicillium chrysogenum produced only few
detectable metabolites or frequently none (Nielsen, 2002).
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 57
Toxic metabolites from isolates of Trichoderma harzianum isolated
from the indoor environment of a building where the occupant was
suffering serious building-related ill-health symptoms damaged the
cell membrane barrier function of sperm cells (Peltola et al., 2001).
However, in Nielsen’s studies, Trichoderma spp. did not produce
detectable quantities of trichothecenes on building materials (Nielsen,
2002). Nielsen (2002) further showed that Chaetomium globosum pro-
duced high quantities of chaetoglobosins on building materials. Walle-
mia sebi, a common indoor xerophyllic fungus, was found to produce
the mycotoxins walleminol and walleminone (Frank et al., 1999).
However, reports on the biological effects of most secondary metabo-
lites are scarce, and very few of the studies evaluated the effects of
inhaled secondary metabolites (Nielsen, 2003).
Samson (1992) divided the adverse effects into four categories: acute,
chronic, mutagenic, and teratogenic. Symptoms related to mycotoxins
or toxin-containing spores (particularly those of S. chartarum) include
dermatitis; recurring cold and flu-like symptoms; burning sore throat;
headaches and excessive fatigue; diarrhea; and impaired or altered
immune function; as well as cough; irritation of eyes, skin, and respi-
ratory tract; or joint ache (Singh, 1994; Tuomi et al., 2000). Compro-
mised ability of the body to resist infectious diseases may lead to
opportunistic infections and possibly cancers. Certain mycotoxins,
such as zearalenone, have been found to cause infertility and stillbirths
in pigs (Matossian, 1989). Low-level, complex exposures from a mix-
ture of mycotoxins may have synergistic effects and may result in
central neuroendocrine-immune changes and consequently in com-
plex health reactions of the endocrine and nervous systems (Ammann,
1999). Residents or occupants who were exposed to toxigenic fungi in
water-damaged buildings might suffer from nonspecific symptoms
(Tuomi et al., 2000).
Although relationships were established to link inhalation exposure
to mycotoxin-containing fungal spores and symptoms of mycotoxicoses
in fungi-infested indoor environments (Croft et al., 1986; Johanning
et al., 1993), other possible exposure routes such as ingestion and
dermal contact are likely. Because fungal spores are ubiquitous in a
contaminated environment, the chance of ingesting toxin-containing
spores is likely to increase through eating, drinking, and smoking.
Concerns were raised that many of the data on exposures to toxigenic
molds were derived from animal toxicity studies, and these are based
primarily on ingestion (Assoulin-Daya et al., 2002). Whether these
results can be extrapolated to human health is questionable. In a review
article, Robbins et al. (2000) argued that although evidence was found
58 LI AND YANG
for a relationship between high levels of inhalation exposure or direct
contact to mycotoxin-containing molds or mycotoxins, and demonstra-
ble effects in animals and health effects in humans, the current litera-
ture does not provide compelling evidence that exposure at levels
expected in most mold-contaminated indoor environments is likely to
result in measurable health effects.
Novotny and Dixit (2000) reported that two fungi, Penicillium (pre-
sumptively Penicillium purpurogenum) and Trichoderma sp., were
cultured from surface samples collected in the residence where a 40-
day-old male suffered pulmonary hemorrhage following exposure to
indoor fungi and tobacco smoke. The authors thought the fungi to be
mycotoxin producers and tried to link the fungi to the pulmonary
hemorrhage. However, without properly identifying the fungi to spe-
cies, it is premature to assume the fungi were mycotoxin producers and
is difficult to establish the causal association between pulmonary hem-
orrhage, the fungi, and mycotoxins. The health effects of indoor molds
can be inconsistent; the presence of fungi was reported to be a signifi-
cant risk factor in Red Deer but not in Medicine Hat, Alberta, Canada
(Hessel et al., 2001).
Since mycotoxin production is species specific, it is crucial to inven-
tory all fungi growing in a contaminated indoor environment and
identify the fungi to species. Without knowing the fungal species that
are present, determination cannot be made whether the species are
toxigenic or not. In addition, the investigators will not be able to
ascertain whether species are able to produce mycotoxins under the
investigated conditions. Mycotoxin production can be influenced by
substrates (medium composition), temperature, water activity, and
other factors, and indoor fungi likely produce different mycotoxins
on building materials (Nielsen, 2003). Therefore it is very difficult to
evaluate the severity of indoor fungal and mycotoxin contamination.
D. VOLATILE ORGANIC COMPOUNDS (VOCS)
Actively growing fungi produce a variety of volatile organic com-
pounds (VOCs), which may produce a distinctive musty, moldy odor.
Fungal VOCs may include 3-methylbutan-1-ol, 3-methylbutan-2-ol,
fenchone, heptan-2-one, hexan-2-one, octan-3-one, octan-3-ol,
pentan-2-ol, alpha-terpineol, and thujopsene. They emit these com-
pounds into the indoor environment (Elke et al. 1999). The most preva-
lent compounds included xylene, toluene, 2-propanol, limonene, and
heptane. Formaldehyde concentrations ranging from 1.7 to 13.3 microg/
m
3
and mean acetaldehyde levels ranging from <3.0 to 7.5 microg/m
3
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 59
were reported (Reynolds et al. 2001). Larsen and Frivad (1995) studied
the in vitro production of fungal volatiles from 47 Penicillium taxa and
detected alcohols, ketones, esters, small alkenes, monterpenes, sesqui-
terpenes, and aromates. However, aldehydes were not among the VOCs
detected.
Fiedler et al. (2001) studied VOC production by Aspergillus fumiga-
tus, A. versicolor, A. niger, A. ochraceus, Trichoderma harzianum,
T. pseudokoningii, Penicillium brevicompactum, P. chrysogenum,
P. claviforme, P. expansum, Fusarium solani,andMucor sp. More than
150 volatile substances derived from the fungal cultures have been
analyzed by head-space solid-phase microextraction (HS-SPME)
(Fiedler et al., 2001). Each species had a defined VOC profile, which
may be subject to considerable modification in response to external
factors such as cultivation on different substrata. Cultivation on differ-
ent substrata changes the number and concentration of VOCs (Fiedler
et al., 2001). Wilkins et al. (2000) studied the production of VOCs by
mold species isolated from damp buildings. They were grown on sterile
building materials and some synthetic media. Patterns of the volatile
organic compounds were very media dependent, but media, which
favor terpene biosynthesis, may give patterns unique enough for identi-
fication of dominant indoor molds (Wilkins et al., 2000). It was proposed
that species-specific volatiles may serve as marker compounds for the
selective detection of fungal species in indoor environments (Fiedler
et al., 2001). Examination of VOCs from indoor air samples may become
an important method in indoor air hygiene for the detection of type and
intensity of masked contamination by molds (Fiedler et al., 2001). Ad-
ditional fungal VOCs are compiled and listed by Ammann (2) and
Batterman (8). Almost all of the published information regarding fungal
VOCs concerns species of Penicillium and Aspergillus.
Some of the fungal VOCs have an unpleasant odor (Gravesen et al.,
1994). The musty, moldy, and earthy odors are likely to come from 2-
octen-1-ol and geosmin (1, 10-dimethyl-9 decalol) (Flannigan et al.,
1991). Ezeonu et al. (1994) identified ethanol, 2-ethyl hexanol, cyclo-
hexane, and benzene from fiberglass air duct liners colonized by As-
pergillus versicolor, Acremonium obclavatum, and Cladosporium
herbarum. Acetone and 2-butanone were only detected on agar plate
samples of A. versicolor and A. obclavatum. The 2-ethyl hexanol and
cyclohexane are eye and skin irritants, and benzene is a generally
recognized hazardous chemical. Other fungal VOCs associated
with two common indoor fungi, Penicillium and Aspergillus, have
been identified. They are 2-methyl-isoborneol, 2-methyl-1-propanol,
3-methyl-1-butanol, and 3-octanone (Gravesen et al., 1994).
60 LI AND YANG
Ahearn et al. (1997) found that lower concentrations of volatile
organics were released from air filter medium colonized by fungi than
noncolonized filter medium in a water-damaged office building. How-
ever, the volatiles from the colonized filter medium included fungal
metabolites such as acetone and a carbonyl sulfide-like compound that
were not present and released from noncolonized filter medium. They
suggested that the growth of fungi in air distribution systems may affect
the content of volatile organics in indoor air (Ahearn et al., 1997).
Fungal VOC levels indoors are normally low. Indoor concentrations
of total volatile organic compounds (TVOCs) were reported ranging
from 73 to 235 microg/m
3
(Reynolds et al., 2001). However, microbial
volatile organic compounds (MVOCs) and metabolites of fungi de-
tected in indoor molds are considered to be a potential health hazard
(Kreja and Seidel, 2002). Their toxicological relevance and health ef-
fect, however, is largely unknown, and data are rare (Kreja and Seidel,
2002).
Although VOCs produced by Aspergillus, Penicillium, and other
fungi have been investigated extensively, little information exists on
what VOCs can be produced by S. chartarum (Gao and Martin, 2002).
Four unique VOCs—1-butanol, 3-methyl-1-butanol, 3-methyl-2-buta-
nol, and thujopsene—were detected on rice cultures of S. chartarum,
and only one of them (1-butanol) was detected on gypsum board
cultures (Gao and Martin, 2002). For a given strain, VOCs were consid-
erably different with different cultivation media (Gao and Martin,
2002). Concentration profiles of the volatile compounds varied among
compounds; however, each compound exhibited corresponding con-
centration trends between the strains (Gao and Martin, 2002). In com-
parison with their previous studies of five Aspergillus species on
gypsum board under the same experimental conditions, fewer unique
VOCs were produced by S. chartarum, and they were significantly
different. Gao and Martin (2002) indicated that VOCs produced by S.
chartarum may represent a relatively small portion of the total volatiles
present in problematic buildings where Aspergillus spp., Penicillium
spp., and other fungi frequently coexist (Gao and Martin, 2002).
Elke et al. (1999) described a new, analytically valid procedure to
assess the exposure of humans to the so-called microbial volatile or-
ganic compounds (MVOCs). The method can be used routinely for
large sample numbers and is especially valuable as a basis for further
research on the correlation between single MVOCs and indoor mold
growth (Elke et al., 1999). With the exception of 3-methylbutan-2-ol,
fenchone, nonan-2-one, octan-2-one, and thujopsene, indoor air con-
centrations of all MVOCs under investigation were significantly higher
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 61
inside damp and moldy dwellings. It was found that 3-methylbutan-1-
ol, hexan-2-one, heptan-2-one, and octan-3-ol were found to be most
reliable indicators for mold growth (Elke et al., 1999).
A correlation was also found between selected VOCs and the occur-
rence of mold species in mattress dust (Elke et al., 1999). Aspergillus
sp. correlated with heptan-2-one, hexan-2-one, octan-3-ol, octan-3-one,
and alpha-terpineol, while the occurrence of Eurotium sp. was
correlated with higher indoor air concentrations of 3-methylbutan-1-
ol, 3-methylbutan-2-ol, heptan-2-one, hexan-2-one, octan-3-ol, and
thujopsene (Elke et al., 1999). However, the correlation raised the
question whether mold species in mattress dust were spores or active
growth. Spores are metabolically slow or inactive and are less likely to
produce VOCs.
Indoor fungal VOCs have been suggested as possible contributors to
adverse health effects. Symptoms related to exposure to fungal VOCs
include nasal irritation and feelings of stuffiness (Flannigan and Miller,
1994). Possibly related mucous membrane and olfactory irritations
may trigger an ‘‘unpleasant odor reaction’’ and annoyance (Yang and
Johanning, 2002). Although exposure to molds can produce significant
mucosal irritation, there are very few data to suggest long-term ill
effects. More importantly, there is no evidence in humans that mold
exposure leads to nonmucosal pathology (Assoulin-Daya et al., 2002).
In a recent study, MVOC-induced DNA damage was observed under
conditions in which cytotoxic effects were observed but clastogenic
and mutagenic effects could not be detected (Kreja and Seidel, 2002).
E. GLUCANS
The polyglucose (1 !3)--D-glucan is a component of cell walls of
fungi, some bacteria, and plants (Rylander and Lin, 2000). (1 !3)--D-
Glucan has been recognized as a potential proinflammatory agent re-
sponsible for bioaerosol-induced respiratory symptoms observed in
both indoor and occupational environments (Gehring et al., 2001;
Milton et al., 2001; Rylander and Lin, 2000). Relationships between
the amount of (1 !3)--D-glucan and the extent of symptoms, lung
function changes, and inflammatory markers have been described. In
addition, (1 !3)--D-glucan can be used as a surrogate for measuring
mold biomass in field studies (Rylander and Lin, 2000).
Milton et al. (2001) developed a specific enzyme immunoassay to
quantify (1 !6) branched, (1 !3)--D-glucans in environmental
samples. The assay was highly specific for (1 !6) branched, (1 !3)-
-D-glucans and did not show any response at 200 ng/ml to curdlan,
62 LI AND YANG
laminarin, pustulan, dextran, mannan, carboxymethyl cellulose, and
endotoxins (Milton et al., 2001). The detection level was 0.8 ng/ml for
baker’s yeast glucan and Betafectin. A coefficient of variation of 7.8%
was obtained for (1 !3)--D-glucans in house dust samples. It will be
useful for the investigation of health effects from exposure to this class
of biologically active molecules (Milton et al., 2001).
Concentrations ranged from below the limit of detection to
19,013 microg/m
2
(22,588 /g dust) from living room floors of 395
homes of two German cities, Erfurt and Hamburg (Gehring et al.,
2001). Associations between (1 !3)--D-glucan, housing characteris-
tics, and occupant behavior were found for concentrations per square
meter but not for concentrations per gram of dust (Gehring et al., 2001).
The following characteristics were associated with a significant in-
crease in beta (1 !3)--D-glucan levels: carpets in the living room,
keeping a dog inside, use of the home by four or more persons, use of
the living room for >180 hr/week, lower frequency of vacuum cleaning
and dust cleaning, and presence of mold spots during the past 12
months (Gehring et al., 2001).
III. Indoor Fungi
A. FUNGAL IDENTIFICATION
The modern concept of the Kingdom Fungi consists of four phyla,
Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota. In
addition, many fungi are conveniently placed in the form group deu-
teromycetes. Deuteromycetes include fungi that grow vegetatively and
may reproduce by producing asexual spores. Species of Zygomycotina,
Ascomycotina, Basidiomycotina, deuteromycetes, and myxomycetes
have all been reported from the indoor environment or identified from
indoor samples by the authors. Many important fungal traits, such as
ecological preferences, the production of mycotoxins, secondary meta-
bolites, VOCs, and the associated health effects, are species-specific. It
is therefore extremely important that fungi be accurately identified to
species. Miller (1991) stressed the importance of reliable fungal identi-
fication no matter what the identifications are used for.
Fungal classification and identification are based on morphological,
biological, molecular, genetic, and physiological characteristics.
Morphological characteristics, both macroscopic and microscopic, are
conventionally the most important in fungal classification and identi-
fication. However, there are situations in which morphological char-
acteristics cannot differentiate similar or closely related species in
large fungal genera such as Penicillium or Aspergillus.Pitt (1979) and
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 63
Klich and Pitt (1988) incorporated physiological and other characters
to facilitate speciation of Penicillium and Aspergillus. With the ad-
vances in molecular and genetic studies, different approaches have
been tried. However, their practical uses have been limited and the
current fungal identification is still morphology-based.
B. AIRBORNE FUNGI
Airborne fungal spores can originate from outdoor as well as indoor
sources. Many studies have been conducted for indoor and outdoor
airborne fungal spores in various parts of the world. In a well-built and
properly maintained building without a history of water damage, its
airborne fungal spores are likely from outdoor sources and should
reflect outdoor spora qualitatively and quantitatively. Only if a build-
ing experiences a significant water damage problem and subsequent
fungal growth do its airborne spores become a significant factor. The
main health concern of indoor fungal growth is the exposure of occu-
pants to airborne fungal spores and other byproducts of fungal growth
from indoors.
A number of air samplers are available for airborne fungi analysis.
However, two types of them are widely used: (a) spore trap type for
total spore count; (b) sieve to agar type (cultural method) for examina-
tion of colonies. The first involves collecting fungal spores and frag-
ments on sticky surfaces applied to a glass slide for direct fungal spore
identification under microscopes. Results are expressed as fungal
spores/m
3
. This yields information of total airborne fungal structures
including both viable and inviable. Such information is important for
any allergen-related health concerns, since all fungal spores and frag-
ments can be allergenic no matter whether they are viable or inviable
(including some non-sporulated ones on cultural media, such as most
basidiomycetes, obligate phytoplane fungi). However, most fungal
spores can be identified to only genus level. The second method in-
volves collecting fungal spores on growing media. After a 7-day incu-
bation, fungi are identified from colonies developed on the media and
enumerated as colony forming units (CFU)/m
3
. The latter one, the
culturable method, produces information very useful for assessment
of pathogenic or mycotoxingenic fungi and their health effects. This
method may not be able to quantify and characterize nonviable and
non-sporulated fungi accurately, but the fungi developed on media can
be identified to species level. The information of fungal species is
essential for assessing the health effects of fungal infestation indoors,
since pathogenicity and mycotoxingenicity are species-specific.
64 LI AND YANG
Molds growing indoors have been understood for some time as a
source of aeroallergens (Pope et al., 1993; Reed, 1985). Some fungi
may cause infection or allergy, depending primarily on the susceptibil-
ity of the hosts (Morey and Feeley, 1990). Outdoor sources of spores are
generally considered to be the major contributor to the indoor air spora
(Flannigan et al., 1991; Li and Kendrick, 1995a). Most of the fungi that
contribute significantly to indoor airborne spores reproduce primarily
by asexual spores (Burge, 1990a), although Chaetomium globosum,
which produces ascospores, is a common contaminant of water-
damaged paper and wood products. The indoor air environment may
be considered a walled-in portion of the outdoor. It differs in patterns
of air movement, humidity, temperature, and possibly also in gas
composition. Air movement results from ventilation, convection, heat-
ing system, cleaning activities, and movement by occupants, but air
does not move as continually—or as rapidly—over a surface as it does
outdoors. Outside air movement influences movement indoors by forc-
ing air through cracks on the windward side and sucking it out on the
leeward, with the direction of airflow changing as the wind direction
changes (Lacey, 1981). Artificial ventilation can rapidly circulate
spores through a building, but convection can also be very effective,
carrying spores from first- to fourth-floor halls within 5 min and into
rooms within 20 min (Christensen, 1950).
During summer in North America, counts of airborne spores out-
doors and indoors may roughly correspond when windows are open
(Snelly and Roby, 1979). It has also been well known for many years
that fungi readily invade and propagate in the interior of homes, and
that perennial allergic symptoms can be attributed to high concentra-
tions of such spores (Salvaggio, 1986).
Species of Cladosporium, Alternaria, Mucor, Aspergillus, and Peni-
cillium, among others, are common and are capable of reproducing
indoors when appropriate substrates and moisture are available
(Morring et al., 1983). Ten Cladosporium species, some of which are
potentially allergenic, have been isolated inside houses in Co
´rdoba,
Spain. Only small differences were recorded among the spora in the
different rooms (Infante-Garcia-Pantaleton and Dominguez-Vilches,
1988). The genus Rhizopus was isolated mostly indoors in Barcelona,
Spain (Calvo et al., 1980). Cooley et al. (1998) reported their studies in
48 schools in the United States that the fungal genera comprised over
95% of the outdoor fungi: Cladosporium (81.5%), Penicillium (5.2%),
Chrysosporium (4.9%), Alternaria (2.8%), and Aspergillus (1.1%). At
20 schools, significantly higher concentrations of Penicillium species
were found in the air samples from complaint areas than from
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 65
noncomplaint areas in the schools. Ren et al. (1999) found that in the
United States, Cladosporium spp. was dominant in both indoor and
outdoor air in summer, while Penicillium and Aspergillus were domi-
nant in indoor air in winter. The dominant airborne fungal spores
indoors in Southern Ontario, Canada, were Cladosporium (38.8%),
Aspergillus/Penicillium (19.8%), Leptosphaeria (7.9%), unidentified
basidiospores (6.5%), unidentified ascospores (2.8%), Ganoderma
(2.6%), Alternaria (1.9%), Coprinus (1.8%), and Epicoccum (3.3%)
(Li and Kendrick, 1995a).
Concentrations and compositions of airborne fungal spores are de-
termined by many factors and variations. There are regional, yearly,
seasonal, and diurnal variations of airborne fungal spore populations
(Li and Kendrick, 1994). Chao et al. (2002b) showed that fungal spore
concentrations in large office buildings varied significantly with sea-
son, with a summer peak, and that concentrations of airborne fungi
were positively correlated with RH and negatively with CO
2
concen-
trations. The seasonal patterns of indoor fungi are closely correlated
with outdoor fungi in residential buildings (Li and Kendrick, 1995a).
Vegetation, landscape, land usage, meteorological factors, and other
environmental factors, as well as biological characters of fungi, deter-
mine the concentration and composition of airborne fungal spores (Li
and Kendrick, 1994). These factors ultimately influence the airborne
fungi indoors. Better understanding of these variations or patterns and
other important factors is crucial for proper sampling strategies and
sample collection.
At present there are insufficient research data of dose/exposure level
and response relationship to establish practical thresholds for making
public health decisions. Although such thresholds are very important
for indoor environmental quality evaluation and investigation, it is
highly unlikely that a dose-response relationship can easily be estab-
lished because of the complexity of fungal compositions and related
allergens and secondary metabolites.
In 7 homes of patients with asthma bronchiale, the concentrations of
mesophilic fungal spores of the indoor air ranged from 100 to 1000
CFU/m
3
, and this was much higher than the mold counts simulta-
neously collected outdoors (Senkpiel, 1996). The major fungal species
found indoors by the investigator were Penicillium sp. >Aspergillus
sp. >Cladosporium sp., Mucor sp., Chrysonilia sp., Verticillium sp. >
Geotrichum sp., Trichoderma sp. (Senkpiel, 1996). The main cause of
fungal contamination was moist building materials on/in room walls,
insufficient air ventilation, poor maintenance of the circulating air
machines, and insufficient room hygiene (e.g., biological garbage in
66 LI AND YANG
the kitchen) (Senkpiel, 1996). However, the reliability of the fungal
identifications is questionable. All fungi were identified to genera. In
addition, some unusual indoor fungi, such as Chrysonilia sp. and
Geotrichum sp., were reported. Although Chrysonilia sp. has been
reportedly isolated from indoors (Samson et al., 2000), it is highly
uncommon. Geotrichum sp. typically produces slimy colonies. In fact,
it is so unusual in the air that Haugland and Vesper (2001) used G.
candidum to spike samples for quality control purposes for their Quan-
titative Polymerase Chain Reaction (Q-PCR) studies. Their detection
and identification of such fungi in the air are highly unusual unless the
fungi were misidentified. The primary characters for the identification
of Geotrichum species are their production of arthrospores. Many air-
borne fungi produce arthrospores in culture and are likely mis-identi-
fied as Geotrichum species.
The fungal spore concentrations and compositions in indoor and
outdoor air in Yokohama, Japan, were sampled and analyzed with a
Reuter centrifugal sampler (RCS) and dichloran 18% glycerol agar
(DG18) and compared with the levels assessed with potato dextrose
agar (PDA) (Takahashi, 1997). In indoor air, the fungal concentrations
were <13 to 3750 CFU/m
3
.Cladosporium spp. predominated, followed
by the xerophilic fungi such as the Aspergillus restrictus group,
Wallemia sebi, the A. glaucus group, and Penicillium spp. The fungal
concentrations in indoor air peaked in October. The concentrations of
fungi were significantly correlated with the indoor temperature, indoor
relative humidity, and the outdoor climatic factors, except for the
average velocity of wind (Takahashi, 1997).
Studies of airborne fungi employed several different media and sam-
plers. However, there are insufficient comparative studies to determine
their efficiencies and differences. A number of studies were conducted
within a short period of time (less than 1 year). Since airborne fungal
spores have distinct seasonality and year-to-year variations, studies for
less than 1 year may not be able to yield meaningful information for the
studied area.
Khan et al. (1999) collected air samples on rose-bengal medium for
20 minutes by using a six-stage Andersen sampler. Aspergillus spp.
were the predominant component (27.7%) of the outdoor aerospora of
Kuwait, and A. fumigatus alone accounted for 21.3% of the total
aspergilli (Khan et al., 1999). Cladosporium spp. were the major com-
ponent of airborne fungal spores indoors (22.8%), followed by Asper-
gillus (20.9%), Penicillium spp. (14.6%), and Bipolaris spp. (10.6%)
(Khan et al., 1999). Ismail et al. (1999) used the settle plate method
with Czapek-Dox agar in Uganda from March through June 1998. The
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 67
most prevalent fungi outdoors and indoors were Mycosphaerella,
yeasts, Penicillium, Fusarium, Aspergillus, Cochliobolus, and Alternar-
ia (Ismail et al., 1999). In Poland the concentrations of airborne fungi in
dwellings without mold problems were between 0 and 1997 CFU/m
3
,
while in moldy homes they were 49 and 16,968 CFU/m
3
, respectively.
Dominant fungi were Penicillium spp., Aspergillus spp., and yeasts.
There were as many as 167 microbial species isolated from the air of
examined dwellings by Gorny and Dutkiewicz (2002). A study of air-
borne fungi in bedrooms in 485 houses was performed over 1 year in
Melbourne, Australia. Fifty-five percent of the houses had viable fungal
propagules exceeding 500 CFU/m
3
,andCladosporium and Penicillium
were identified as the most prevalent and abundant fungal genera in
indoor air (Dharmage et al., 1999). Klanova (2000) reported the total
concentrations of airborne fungi were much higher in moldy rooms than
in the reference rooms, but health complaints did not correlate with the
total concentrations of airborne fungi. All occupants of rooms where the
average concentration was 2476 CFU/m
3
reported health complaints.
Sometimes samplings of airborne fungal spores may not reflect the
fungal problems indoors. Hyvarinen et al. (2001) found that some
fungal genera detected in moist building materials such as Ulocladium
and Chaetophoma were not found in indoor air. This result showed
that bulk samples of building materials provide additional mycota
information in the building (Hyvarinen et al., 2001).
Vujanovic et al. (2001) proposed that airborne fungi could be classi-
fied on the basis of the relationship between the two environmental
factors and their combinations (i.e., temperature and water require-
ments [water activity, a
w
]). Three different groups are proposed: (i),
represented by Emericella (Aspergillus)nidulans, A. niger, and A.
ochraceus, and characterized by sporulation that was more dependent
on temperature than on water activity; (ii), represented by A. flavus and
A. versicolor, in which sporulation was approximately equal and de-
pended on both the temperature changes and a
w
alterations; and (iii),
represented by Cladosporium sp., Penicillium cyclopium,andP. citri-
num, in which sporulation depended more on alteration of the a
w
conditions than on temperature changes. Temperature and a
w
for each
of the three phases of fungal growth (i.e., germination, growth, and
sporulation) could be important for the determination of the funda-
mental niche of each fungus and its ability to form or accumulate
mycotoxins (Vujanovic et al., 2001).
Recently Gorny et al. (2002b) reported their findings of the study of
airborne fungal fragments. The study found that small fungal fragments
of Aspergillus versicolor, Penicillium melinii, and Cladosporium
68 LI AND YANG
cladosporioides were released into the air simultaneously with conidia
from agar and ceiling tile surfaces (Gorny et al., 2002b). However, the
results clearly showed that the release mechanisms for fungal frag-
ments and conidia are different. The release of fungal propagules
depended on the fungal species, the air velocity above the contami-
nated surface, and the texture and vibration of the substrates (Gorny
et al., 2002b). Gorny et al. (2002b) showed that fragments and conidia
of Aspergillus versicolor and Penicillium melinii shared common anti-
gens by using enzyme-linked immunosorbent assays with monoclonal
antibodies. This study clearly showed the potential biological rele-
vance of airborne fungal fragments. The presence of airborne fungal
fragments at the clearance stage of any remediation in mold-infested
buildings should not be overlooked or underestimated.
Shelton et al. (2002) evaluated 12,026 fungal air samples (9619 in-
door samples and 2407 outdoor samples) collected from 1717 buildings
located across the United States by using Andersen N6 single stage
samplers. The culturable airborne fungal concentrations in indoor air
were lower than those in outdoor air. However, Stachybotrys chartar-
um was identified in the air in 6% of the buildings studied and in 1%
of the outdoor samples. The fungal levels were highest in the fall and
summer and lowest in the winter and spring. Geographically, the high-
est fungal levels were found in the Southwest, Far West, and Southeast
(Shelton et al., 2002). However, the reliability of fungal identification
and sampling quality control of such a large project must be scrutinized
before the results and conclusions are accepted.
Viability and culturability of airborne fungi are influenced by many
factors. Environmental factors are the predominant ones. However
sampling methods, devices, and time may have significant effects on
the viability of airborne fungi. The duration of air sampling when using
Andersen, SAS, and RCS samplers varies from 1 to 10 min. Since most
airborne fungi have well defined diurnal patterns (Li and Kendrick,
1995b) and such a short sampling time or ‘‘snap shot’’ for airborne
fungi, an investigation may miss the peak periods of airborne fungi.
This kind of air sampling does not fully reflect the exposure of occu-
pants or workers to airborne fungi. This is the reason why filtration at
composting facilities is a preferred method for a long duration of
sampling for air fungal spores. In a recent study Durand et al. (2002)
showed that increased sampling time (up to 6 h) did not affect the
viability of airborne fungi collected on polycarbonate filters at 2 l/min.
At present there are a number of samplers available on the market for
collecting culturable spores (Andersen, Burkard, SAS, RCS, AGI-30,
Biosampler, etc.) and for trapping spores and hyphal fragments
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 69
(Burkard, Andersen, Air-O-Cell, Micro-5, Cyclex-D, Allergenco, Biosys-
tem, AGI-30, BioSampler impingers, etc.) as well as ones used for both
culturable and total spore collection purposes (bi-cassette, Button
Sampler, polycarbonate filter, etc.). Several of these are new products.
Further evaluation and validation of the new products are necessary.
Comparative interpretation of the results collected with different sam-
plers is impossible, since there is no standard sampling and analytical
protocol, and different samplers have different collection characteris-
tics. This is one more reason why determination of the exposure limits
or thresholds of airborne fungi is difficult to impossible.
Gorny et al. (2002a) found that vibration of 1Hz/14W releases the
highest number of fungal progagules of Aspergillus versicolor, Penicilli-
um melinii, and Cladosporium cladosporioides into the air. Kildesøet al.
(2002) found that release of conidia of P. chrysogenum and Trichoderma
harzianum from wet gypsum board was not significantly influenced by
repeated air disturbance on fungal growth. Penicillium chrysogenum
reached maximal sporulation at 18 to 23 days on wet gypsum board,
while T. harzianum, around 20 days (Kildesøet al., 2002).
Several published studies have dealt with the adverse effects of
airborne fungal spores indoors as related to residential characteristics
such as presence of basement, stove, carpets, humidifier, and heating
systems (Agrawak et al., 1988; Su et al., 1992). Specific indoor envir-
onments may have unique conditions that allow fungal growth to
occur. Fungal species seem to develop preferentially in kitchens, fol-
lowed by bathrooms. They occur less frequently in bedrooms, probably
as a result of the lower humidity prevailing in these rooms (Infante-
Garcia-Pantaleton and Dominguez-Vilches, 1988). Recorded spore con-
centrations in the air of some mold-affected houses during winter were
equal to or greater than those expected outside in summer (Flannigan
et al., 1991). The predominance of these fungi in the indoor atmo-
sphere has been attributed to their ability to grow on many household
items such as foods, damp leather goods, paper and cotton fabrics, and
almost any chronically damp surfaces (Vittal and Glory, 1985). Among
indoor microhabitats known to favor mold growth are garbage contain-
ers, food storage areas, upholstery, wallpaper, house plants, books,
papers, and areas of moisture such as damp basements, walls, ceilings,
shower curtains, window moldings, air conditioners, humidifiers, and
vaporizers (Morring et al., 1983; Salvaggio and Aukrust, 1981).
Observations in one climate do not necessarily apply to other cli-
mates. Indoor molds may be more important in humid climates. Occa-
sionally, in bathrooms or basements, a persistent damp area may
support enough mold growth in otherwise dry houses to liberate
70 LI AND YANG
sufficient spores to cause disease (Reed, 1985). Li and Kendrick (1995a,c,
1996) used CANOCO and path analysis to show that most indoor fungi
originated from outdoor sources, and both diurnal and seasonal patterns
clearly showed the close correlations of airborne fungi indoors and
outdoors. Different fungi possess different diurnal and seasonal pat-
terns, and the diurnal patterns of ascomycetes and basidiomycetes are
very different from hyphomycetes (Li and Kendrick, 1995a,b).
The significance of the diurnal and seasonal patterns in the evalua-
tion of indoor airborne fungal spores has long been overlooked. Better
understanding of the seasonal and diurnal patterns can help indivi-
duals who are doing mold exposure investigation to better understand
population dynamics of airborne fungi at a specific time, location, and
season and can assist individuals to determine the specific sampling
strategy accordingly.
Compared with outdoor air, much less research has been done on
indoor airborne fungal spores. It is partially due to the difficulty of
obtaining access to suitable residences and patients to carry out a long-
term study. In addition, there are many variables involved, such as the
structure of the houses, the furniture, upholstery, ventilation and heat-
ing systems, and the cultural background and activities of residents.
All these variables make it very difficult to design an experiment that
accounts for all important factors and the interactions among them.
Furthermore, the indoor niche is suitable for certain fungi to grow year
around, which could blur the exposure/symptom relationship.
Four recent impactor air samplers were selected for study: Samplair
(AES, Combourg, France); Air Test Omega (LCB, France); Air Samplair
Mas-100 (Merck, France); and BioImpactor 100–08 (AES) (Nesa et al.,
2001). They were compared with one another at three different hospital
sites with varying levels of air contamination. No significant difference
in the efficiency of spore recovery was found between Air Test Omega,
Mas-100, and BioImpactor, whereas Samplair was significantly less
efficient (Nesa et al., 2001). BioImpactor was then selected to represent
the three superior impactors and was compared with the single-stage
Andersen disposable sampler, the Collectron MD8 air sampler (Sarto-
rius, France), and the High Flow Air Sample (BioTest, France), which
are based on filtration and centrifugation methods, respectively. No
significant difference was observed in terms of spore recovery (Nesa
et al., 2001). On the basis of their performance, unit sampling cost,
autonomy, and simplicity of use, the authors concluded that Air Test
Omega, Air Samplair Mas-100, and BioImpactor 100–08 are suitable for
routine indoor evaluation of fungal contamination of air in hospitals
(Nesa et al., 2001).
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 71
Most research so far has been conducted with viable and culturable
methods (which enumerate and identify fungal colonies) and with a
variety of samplers because no standard method and instrument have
been established. It is therefore very difficult to compare the results
obtained with different protocols in a meaningful way. Research with
sampling for culturable propagules tends to seriously underestimate
actual spore levels. Airborne fungal spores may be viable, dormant,
moribound, or dead. Burge (1986) believed that viable spores are highly
selective in their cultural requirements. However, most fungi and fun-
gal spores identified in various studies mentioned in the text are ready
to grow on common fungal media unless they are dead or dormant.
Some fungi, such as certain ascomycetes and basidiomycetes, are diffi-
cult to culture on the media normally employed. In any case, spores do
not need to be viable to cause allergies. Some very important allergenic
species would, therefore, have been ignored by most studies based on
culturable methods. In the last several years several new spore-
trapping samplers were developed in addition to Burkard, Allergenco,
and Rotorod. The Burkard sampler, Allergenco, Air-O-Cell, Laro, and
Cyclex-D samplers, etc., overcome the shortcomings of the culturable
methods by permitting visual counting and identification of spores
trapped on adhesive slides or tapes. However, there is a deficiency
with these spore-trapping samplers—namely, that some fungal spores
can only be identified to the generic or group level unless they are
cultured from the spores. This problem points out the difficulty of
identifying many similar-looking spores to the generic or species level
even by highly experienced mycologists and the need to develop broad
spectrum culture techniques or media. To a large extent, both problems
remain unsolved.
C. FUNGI GROWING ON INDOOR/BUILDING MATERIALS
The detection of airborne fungi does not necessarily indicate growth
or amplification of fungi indoors. However, it is generally believed that
actively growing fungi indoors are the principal cause of the adverse
health effects because of constant exposure to indoor sources of fungal
allergens, mycotoxins, glucan, and fungal VOCs. Needless to say, it is
important to characterize indoor fungi and at the same time to identify
growth sites of fungi indoors.
Many common indoor fungi are strong deteriorating agents and have
been reported from various building materials and systems. Many
species of the genus Penicillium, commonly detected in indoor air
sampling, have frequently been referred to as food spoilage and
72 LI AND YANG
bio-deteriorating agents (Gravesen et al., 1994; Pitt, 1979). Pasanen et al.
(1992) demonstrated that Penicillium was the most common mesophi-
lic fungal genus in all the building materials studied (wallpaper, wood,
plywood, gypsum board, and acoustical fiber board), comprising 70%
of identified fungi. Raper and Fennell (1977) reported Aspergillus spp.
from building materials such as textiles, jute, insulation materials,
wallpaper, and other paper products. Gravensen et al. (1994) included
a list of 13 fungal species as important molds in damp buildings.
Samson et al. (1992) described 23 common fungal species in indoor
environments.
In water-damaged building materials in Denmark, the fungal genera
most frequently encountered indoors were Penicillium (68%), Asper-
gillus (56%), Chaetomium (22%), Ulocladium (21%), Stachybotrys
(19%), and Cladosporium (15%) (Gravesen et al., 1999). Penicillium
chrysogenum, Aspergillus versicolor, and Stachybotrys chartarum
were the most common species in water-damaged materials (Gravesen
et al., 1999). Stachybotrys atra was isolated with swab samples of
visible growth under wet carpets, on wet walls, or behind vinyl wall
coverings in 11 schools in the United States (Cooley et al., 1998).
Morgan-Jones and Jacobsen (1988) studied moldy carpets, plaster-
board, and wallpaper from three hotels in Florida and Georgia. The
genera of fungi identified were species of the ascomycete genus
Chaetomium; of the dematiaceous hyphomycete genera Alternaria,
Cladosporium, Stachybotrys, and Ulocladium; of the moniliaceous
hyphomycete genera Acremonium, Aspergillus,andPenicillium;and
of the pycnidial genus Phoma. In the study, 14 species, including 2 new
species of Cladosporium, in 11 genera were isolated and identified. In a
study of toxicity of moldy building materials, Johanning et al. (1998)
identified several groups of fungi from gypsum wallboard and other
building materials. The fungi identified included those described by
Morgan-Jones and Jacobsen (1988) and additional species of Aspergil-
lus, Paecilomyces, and Trichoderma.Ka
¨pyla
¨(1985) found that pre-
dominant fungus growing on wooden frames of insulated windows
in Finland was Aureobasidium pullulans. In subartic areas, Pessi
et al. (2002) found that indoor fungi occurred infrequently in the
insulation inside insulated precast external concrete walls and that
fungal infestation in the insulation was not found to influence indoor
air in the region.
In Brazil in unusual situations, growth of Cryptococcus neoformans
var. neoformans indoors was due to the presence of avians in the
domestic environment or nearby the home. Higher incidences of cryp-
tococcosis was reported among AIDS patients residing in the dwellings
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 73
from which C. neoformans var. neoformans was isolated than among
AIDS patients from whose domestic environment the fungus was not
detected (Passoni et al., 1998).
In the United States, Histoplasma capsulatum and cases of histoplas-
mosis have been reported from indoor environments such as old hous-
es, church attics, chicken houses, and barns (Collier et al. 1998;
Lenhart, 1994). A primary source of H. capsulatum is soil, especially
in regions of bird or bat habitats. While wind is probably the most
important means of disseminating H. capsulatum, the fungus can sur-
vive and be transmitted from one location to another on the feet of both
birds and bats (Rippon, 1988).
D. FUNGAL BIODIVERSITY INDOORS
One hundred sixty-seven microbial species were discovered from the
air of dwellings in Central and Eastern Europe (Gorny and Dutkiecicz,
2002). Yang et al. (1993) reported that Cladosporium, Penicillium,
Aspergillus, basidiomycetes, and Alternaria were identified, by fre-
quency, as the top five fungal taxa both indoors and outdoors in the
United States. An additional 50 fungal taxa were also identified. How-
ever, Penicillium, Cladosporium, Aspergillus, basidiomycetes, and Al-
ternaria were the top five indoor fungal taxa by concentrations in a
descending order, while Cladosporium, Penicillium, basidiomycetes,
and Aspergillus were the top five outdoor taxa. Womble et al. (1999) of
the US Environmental Protection Agency (USEPA) reported that non-
sporulating fungi, Cladosporium, Penicillium, yeasts, and Aspergillus
were the five most commonly found fungal taxa indoors and outdoors,
based on the frequency of detection. The most common culturable
airborne fungi indoors and outdoors in all seasons and geographic
areas in the United States were Cladosporium, Penicillium, nonspor-
ulating fungi, and Aspergillus in a descending order (Shelton et al.,
2002). In Taiwan the predominant genera of airborne fungi are Clados-
porium, Aspergillus, Penicillium, Alternaria, and yeast (Su et al.,
2001b). Stachybotrys chartarum was identified in the indoor air in
6% of the buildings studied and in 1% of the outdoor air around the
buildings studied in the United States (Shelton et al., 2002).
E. STACHYBOTRYS CHARTARUM AND OTHER STACHYBOTRYS SPP.
Stachybotrys chartarum is one of the major species occurring on
cellulose-based building materials in indoor environments. This spe-
cies has attracted the most attention because of its ability to produce
74 LI AND YANG
some of the most potent mycotoxins known and its association with
infant pulmonary hemorrhage and hemosiderosis and adult nasal and
tracheal bleeding (Dearborn, 1997; Vesper and Vesper, 2002; Vesper
et al., 2001).
Stachybotrys chartarum was isolated for the first time from the lung
of a child diagnosed with pulmonary hemosiderosis in Texas (Elidemir
et al., 1999). Flappan et al. (1999) reported another case of infant
pulmonary hemorrhage associated with the presence of Stachybotrys
atra (¼S. chartarum), and mycotoxin analysis demonstrated that the
isolate was highly toxigenic. Vesper et al. (2001) characterized a hemo-
lysin, later called stachylysin, from S. chartarum and analyzed its
hemolytic activity and siderophore production. It was hypothesized
that stachylysin could be a contributing factor to infant pulmonary
hemorrhage and hemosiderosis (Vesper and Vesper, 2002).
Under field conditions, several trichothecenes were detected in each
of three commonly used building materials heavily contaminated with
S. chartarum (Gravesen et al., 1999). Under experimental conditions,
four out of five isolates of S. chartarum produced satratoxin H and G
when growing on new and old, very damp gypsum boards (Gravesen
et al., 1999). In a preliminary study conducted in a Dynamic Microbial
Test Chamber, Foarde and Memetrez (2002) showed that conidia of
Stachybotrys chartarum released from gypsum boards at low air flow
rate were positively related to air flow rate, but negatively related to
relative humidity.
Enzyme immunoassay indicated 65 of 132 (49.2%) sera tested con-
tained IgG against S. chartarum and 13 of 139 (9.4%) sera tested
contained IgE against S. chartarum (Barnes et al., 2002). Sensitivity to
S. chartarum is potentially much more widespread than previously
appreciated (Barnes et al., 2002). This fungus may affect the asthmatic
and the allergic population through both immunologic and toxic me-
chanisms (Barnes et al., 2002).
Rao et al. (2000), using an animal model, showed that methanol
extraction dramatically reduced the toxicity of S. chartarum spores,
and a single, intense exposure to toxin-containing S. chartarum spores
resulted in pulmonary inflammation and injury in a dose-dependent
manner.
Initial spore concentrations were between 0.1 and 9.3 spores/m
3
of
air, and the toxicity of air particulates was correspondingly low. How-
ever, the dust in the house contained between 0.4 and 2.1 10
3
spores/
mg (as determined by hemocytometer counts) (Vesper et al., 2000). Air
samples taken postremediation showed no detectable levels of S. char-
tarum or related toxicity. Nine isolates of S. chartarum obtained from a
FUNGAL CONTAMINATION AS A MAJOR CONTRIBUTOR 75
home were analyzed for spore toxicity, hemolytic activity, and random
amplified polymorphic DNA banding patterns (Vesper et al., 2000).
None of the isolates produced highly toxic spores (>90 g T2 toxin
equivalents per gram wet spores) after growth for 10 and 30 days on wet
wallboard, but three isolates were consistently hemolytic (Vesper et al.,
2000).
In addition to S. chartarum, several species of Stachybotrys have
been isolated and identified from the indoor environment. S. yunanen-
sis, S. nephrospora, S. microspora, S. elegans, and S. chlorohalonata
were identified and present in samples from indoor environments (Li
and Yang, 2003; Nielsen