Human exposure to airborne fungal spores, hyphal fragments or
metabolites can result in a variety of adverse health effects
(Pasanen, 2001). Reactions to exposure include allergic and irritant
responses (Gravesen, 1979); infectious disease such as histoplasmosis,
blastomycosis, and aspergillosis (de Hoog et al., 2000); a variety
of respiratory diseases (Godish et al., 1996a) including asthma
(Downs et al., 2001) allergic rhinitis, hypersensitivity pneumonitis
(Samson, 1985; Stetzenbach, 1997) and bronchial hyperactivity
(Dharmage et al., 2001); acute toxicosis (Samson, 1985; Stetzenbach,
1997); SBS symptoms (Szponar & Larsson, 2000); and cancer
from exposure to mycotoxins (Levetin, 1995). Exposure to fungal
spores has been identified as statistically significant risk factors
for respiratory health in children (Garret et al., 1998a, b).
The inhalation of fungal material, which is often small enough
to penetrate deep into the lungs, may pose an even greater health
risk than ingestion or dermal contact (Johanning, 1994; Stetzenbach,
1997). However, the role of fungi in the development of disease
and illness is not clear (Szponar & Larsson, 2000).
Normally, fungal exposure is most associated with hay fever,
asthma (Levetin, 1995; Stetzenbach, 1997) and allergies (Gravesen,
2000). Spores or fragments of hyphae reach the respiratory tract
and lungs, generating allergic responses (Jennings & Lysek,
1999) and up to 15% of the general population have been measured
to be allergic to “fungi” (Miller, 1992). The components
of most fungi can be antigenic, and fungal spores are well known
carriers of aeroallergens (Levetin, 1995). This is due to the
fact that the walls of all fungi contain proteins which are potential
inducers of IgE-mediated allergy in atopic persons (Gravesen,
2000).
However, the literature on fungal allergens is confusing. Some
studies suggest no relationship between fungi and allergy despite
the general understanding to the contrary (Tarlo et al., 1988).
This may be due to the fact that exposure to fungi does not always
cause allergy, as allergy only develops in a sensitised individual
(Miller, 1992).
Fungal allergens identified to date are glycoproteins (Levetin,
1995) and a single species of fungi can produce dozens of allergens
(Drouhet, 1988). Individual species such as Alternaria species
are suggested as the major allergen source associated with the
development of childhood asthma (Downs et al., 2001).
Only a small group of fungi are considered human pathogens and
very few species are considered primary systemic human pathogens
(Levetin, 1995; Stetzenbach, 1997). Most of the fungi that infect
humans are opportunistic parasites, which grow more commonly as
saprotrophs in soils, composts, bird excreta etc., but can infect
through wounds or when airborne spores enter the lungs (Deacon,
1997). Fortunately, fungal pathogens are rarely reported to be
present in indoor air (Flannigan, 1994a).
There is also persuasive evidence that exposure to fungi at work
is responsible for many cases of illness (Rom, 1983). Mycotoxins,
unlike fungal allergens, cause a wide range of chronic systemic
effects in humans (Tuomi et al., 2000; Pieckova & Kunova,
2002) and will elicit toxic responses from virtually all individuals
who are exposed (Jarvis, 1994). Exposure to mycotoxins in the
indoor air is almost exclusively through inhalation of spores
containing the toxins and gaseous forms released during metabolism
(Tuomi et al., 2000). These toxins attack the bronchial and lung
tissues, which are particularly sensitive to chemical insult,
and the mucosa lining exhibits strong responses to fungal immuno-active
agents (Jarvis, 1994). There are over 400 known mycotoxins (Tuomi
et al., 2000) and many fungal species that are common to indoor
air produce such toxins, which could be responsible for a variety
of health effects (Levetin, 1995). However, few studies have established
a causal relationship between mycotoxin exposure and building
related illness (Tuomi et al., 2000).
Other metabolites that are volatile can cause unpleasant odours,
such as the characteristic mouldy smell in damp basements (Levetin,
1995). Some of these VOCs are short chain alcohols or aldehydes
(Samson, 1985) or organic acids (Ström et al., 1994), which
may be responsible for symptoms such as headaches, dizziness,
and eye and mucous membrane irritation resulting from exposure
to fungi in contaminated buildings (Samson, 1985; Burge, 1990;
Pasanen, 2001).
