Fungi in the domestic environment and community settings –
association with health problems
D. Stevens
March 2004
Summary
This report reviews the external literature on the infection potential in community and domestic settings with
particular reference to fungi (commonly referred to as mould).
The report looks at what are fungi, evidence for fungal contamination in the indoor environment, and why fungi
are a problem in community settings and the domestic environment. Infections, allergies and health effects that
fungi cause are discussed.
The evidence of where fungal contamination in community and domestic settings has been linked to health
effects and infection outbreaks is reviewed. The evidence showing that removal of mould plays a part in reducing
or eliminating such infections and allergies is also highlighted.
Finally, the evidence that removal of mould from the home improves indoor air quality and the effectiveness of
chemicals is discussed.
Contents
1. Background ........................................................................................................................... 3
2. What conditions favour fungal growth? ......................................................................................... 3
3. Evidence for occurrence of fungal contamination indoors .................................................................. 4
3.1 Surveys of fungi in community and domestic settings .............................................................. 4
3.2 Concentrations of fungi .................................................................................................... 6
4. Why are fungi a health problem? ................................................................................................ 7
4.1 Surface damage ............................................................................................................ 7
4.2 Spores ........................................................................................................................ 7
4.3 Allergens...................................................................................................................... 7
4.4 Cell wall components ...................................................................................................... 8
4.5 Mycotoxins ................................................................................................................... 8
4.6 Volatile organic compounds .............................................................................................. 8
5. Fungal infections .................................................................................................................... 9
6. Health problems associated with fungi........................................................................................ 10
6.1 Allergies .................................................................................................................... 10
6.2 Respiratory/Non-respiratory symptoms .............................................................................. 10
6.3 SBS/BRI .................................................................................................................... 11
7. Evidence linking presence of fungi in the home to health problems .................................................... 11
7.1 Respiratory Illnesses ........................................................................................................ 11
7.2 Non-respiratory illnesses ................................................................................................... 13
7.3 Asthma ......................................................................................................................... 13
7.4 Allergies ........................................................................................................................ 14
7.5 Illness associated with Stachybotrys atra ............................................................................... 14
7.6 Alveolitis ........................................................................................................................ 15
8. Evidence linking presence of fungi in community settings to health problems ....................................... 16
8.1 Hospitals ....................................................................................................................... 16
8.2 Day care centres/schools................................................................................................... 16
8.3 Other buildings................................................................................................................ 17
9. Removal of exposure to mould ................................................................................................. 17
10. Efficacy of chemicals against fungi .......................................................................................... 19
11. Conclusions ....................................................................................................................... 20
12. References ........................................................................................................................ 21
1. Background
Fungi are ubiquitous in all environments, indoors and outdoors. All fungi are eukaryotic organisms and exist in
different growth forms such as rusts, mushrooms, mould and yeasts. Yeasts grow as oval or spherical single
cells and multiply by budding and division. Filamentous fungi (more commonly known as moulds) consist of long,
branching filaments called hyphae. Fungi reproduce via formation of spores from sexual or asexual processes.
Some fungi can exhibit both growth forms and are known as dimorphic fungi. Many species of fungi live as
commensal organisms in or on the surfaces of the body e.g. Candida, Rhodoturula. Candida albicans can be
cultured from more than half of the population that has no evidence of active infection.
This report reviews the external literature on the potential health problems caused by fungi (more commonly
referred to as mould or mildew) with regard to its presence in the domestic home and community settings. It does
not address fungi associated with food spoilage/food poisoning or fungal exposure in agricultural settings.
2. What conditions favour fungal growth?
Airborne fungal spores are present in outdoor air all year round, usually in high numbers. These spores can enter
indoor environments via natural ventilation (open windows and doors) and mechanical ventilation systems such
as air conditioning. They are also brought indoors on people’s clothing and shoes and pets. Therefore, indoor
fungi can be a mixture of fungi from outdoors and fungi from indoor sources. Fungi can be present in the soil of
houseplants, in house dust or on pets, as well as on household surfaces.
Mould, or mildew as it may be referred to, likes warmth and moderate to high humidity, and so can be a problem
in developing countries where humid weather conditions are frequent. In developed countries, the high humidity
and temperatures often found in bathrooms and kitchens are conducive to mould growth. Activities such as
drying laundry indoors, on clothes driers or in tumble driers not vented to the outside, can increase humidity
levels in the home. Water damaged carpets, ceilings or walls are prime sites for new growth if they continue to
remain damp. Buildings where mould growth problems are reported have usually have water damage, e.g.
leaking roofs or plumbing. Penicillium spore counts are related to home dampness (Li and Hsu 1995). Provided
there is sufficient moisture, fungi may grow on any building material (Pasanen et al. 1991). Damp housing is a
common problem and is often associated with mould problems (see table 1). Moisture and mould are also
common in buildings used as day-care centres (DCC).
Table 1: Studies on damp/mould problems
Country
Austria
Findings
8% of homes reported by their occupants to be damp or
Reference
Hutter et al. 2002
Finland
Finland
mouldy
70% of day-care centre buildings had moisture or water
damage problems
52% of houses assessed had a moisture problem
Ruotsalainen et al. 1993
Koskinen et al. 1999a
Netherlands
visible mould or damp was reported by 15% of 10,000
students surveyed
24% of homes had dampness
Sweden
Dampness was found in 27% of homes
Norback et al. 1999
UK
2.5 million homes affected by mould or damp
Smith et al. 1992
UK
25-33% of houses affected by dampness, condensation or
mould
Williamson et al. 1997
Finland
Kipelainen et al. 2001
Brunekreef 1992
Association of health problems of the occupants with damp or mouldy homes has been studied. In some studies
information on home dampness and/or mould and problems with health was obtained through completion of
questionnaires by occupants rather than observations by researchers, so the information is on self-reported
health problems rather than clinically diagnosed health problems. It has been suggested that an awareness of an
association of living in a damp home and respiratory health problems may lead to over-reporting of symptoms by
occupants of damp homes or over-reporting of damp problems if occupants have respiratory health problems
(Strachan 1988).
The results of studies can be difficult to compare because the methods of measuring exposure and health
outcomes have not been standardised. Several studies have found an association between reported respiratory
symptoms/infections in children and reported damp/mould in the home (Fischer et al. 1988, Strachan and
Sanders 1989, Dales et al. 1991b, Jaakkola et al. 1993, Verheoff et al. 1995, Yang et al. 1997, Andriessen et al.
1998, Koskinen et al. 1999b). Studies of children’s health are the most reliable because the effects of smoking
and occupational exposures are absent. Studies of adult health have also shown that damp housing is
associated with increased prevalence of respiratory symptoms and/or asthma (Dales et al. 1991a, Pirhonen et al.
1996, Koskinen et al. 1999a, Kipelainen et al. 2001).
3. Evidence for occurrence of fungal contamination indoors
3.1 Surveys of fungi in community and domestic settings
There have been a number of studies investigating fungal species in the home. Table 2 shows the global extent
of mould problems in homes. As many as 29 different genera of fungi have been detected in both indoor and
outdoor air at a single residence (Gots et al. 2003). In one study, spores of Penicillium spp. and Cladosporium
spp. were isolated on every occasion from at least one room in all homes (Strachan et al. 1990). Aspergillus spp.
and other fungi as well as yeasts were also isolated. Total airborne mould counts varied from 0-41000 cfu/m3 but
were usually in the range 50-1500 cfu/m3.
Table 2: Results from studies on mould problems in the home
Location
Australia
Findings
Visible mould growth was present in every house at some time
during the study
Reference
Garrett et al. 1998
Berlin
63% homes had large amounts of viable fungal propagules or
visible fungal growth
Dill and Niggemann 1996
Finland
Visible mould was reported in 3.7% of homes, and 5.5% reported
mould odour
Pirhonen et al. 1996
Lithuania
86% of dwellings investigated had visible mould growth
Krikstaponis 2000
Poland
Penicillium and Aspergillus occurred in 97% and 63% respectively
of homes
Gorny and Dutkiewicz 2002
UK
Visible mould was found in 46% of households
Platt et al. 1989
In a survey in Central Scotland the main fungus isolated from indoor air was Penicillium, with Cladosporium
being the second most common (Hunter et al. 1998). They also isolated pink and cream yeasts (Rhodotorula and
Sporobolomyces) from the air of over 90% of houses. Penicillium, Cladosporium and Aspergillus were also the
predominate fungi isolated from homes surveyed in Netherlands (Beaumont et al. 1985), North America (Miller
et al. 1988), Taiwan (Su et al. 2001, Canada (Li and Kendrick 1995), Germany (Dill and Niggerman 1996),
Lithuania (Krikstaponis 2000) and Turkey (Unlu et al 2003).
Wickman et al. (1992) found that Aspergillus levels correlated with wall to wall carpets. Cole and co-workers
have also comprehensively documented fungal contamination of soft furnishings in the home. Levels of fungal
contamination in carpets and upholstery have been shown to be almost and above 100,000 cfu/g and contain
fungi such as Cladosporium, Alternaria and Penicillium (Cole et al. 2000). Other fungi recovered include
Aspergillus versicolor, Rhodotorula, Aspergillus fumigatus, Aspergillus flavus, Paecilomyces, Trichoderma,
Phialophora, Rhizopus, Ulocladium, Fusarium and Stachtbotrys (Cole et al. 1999). Klanova (2000) also found
that higher concentrations of fungi in dwellings in the Czech Republic corresponded with presence of soft
furniture and carpeting.
Fungi such as Aspergillus niger may also form in the topsoil of houseplants. In hospitals and homes, the soil from
a wide range of potted plants was found to be a major source of A. fumigatus, as well as A. niger and A. flavus
(Staib 1984). Fungi may be also found in air conditioning equipment, humidifier reservoirs, dehumidifier drip pans
and showerheads.
In Denmark, Gravesen et al. (1999) investigated materials from 72 mould-infected public buildings. The most
frequent isolated fungi were Penicillium, Aspergillus, Chaetomium, Ulocladium, Stachybotrys and Cladosporium.
3.2 Concentrations of fungi
Indoor ambient concentrations are influenced by several factors including climate, temperature, humidity,
presence of houseplants, type of ventilation, type of furniture and carpeting present or presence of pets. Activities
such as dusting, vacuuming and dusting will also affect fungi levels detected in the air (Pieckova and Jesenska
1999).
Sampling and survey approaches report their findings in various ways. Fungal concentrations are reported as
either viable colony-forming units per cubic metre (cfu/m3) or total spore counts per cubic metre. Spore
concentrations are usually much lower in homes or community settings than in agricultural settings, but
concentrations as high as 450,000 cfu/m3 have been reported (Hunter et al. 1988, Platt et al.1990).
It is suggested that the fungal levels indoors should be related or compared to levels measured outdoors because
indoor levels of fungal spores are strongly dependent on the outdoor level of spores. However, Fischer and Dott
(2003) state that in buildings with mould problems, the incidence of Penicillium and Aspergillus is often higher
than in outdoor air. For example, on investigating fungal contamination of indoor air in homes of patients with
asthma bronchiale, Senkpiel et al. (1996) found spore counts to be 4 to 40 times higher than that measured
outdoors. Bardana (2003) suggests that the levels should also be measured in homes where occupants have not
complained of health problems as this gives a normal baseline for the geographical area and season of the year.
Hutter et al. (2002) found that classification of visible mould growth by medical doctors in flats in Austria
correlated significantly with the ratio of indoor/outdoor concentrations of fungal spores. Gots et al. (2003)
reviewed 31 studies that looked at indoor and outdoor air ambient concentrations of fungi in domestic homes and
commercial buildings in which the occupants did not have health complaints. For domestic homes, the indoor
average viable fungal concentration was 1252 cfu/m3 and ranged from 17-9100 cfu/m3, The outdoor concentration
ranged from 20-11,883 cfu/m3, with an average of 1524 cfu/m3. The total spore count indoors ranged from 682307 spores/m3, whilst the outdoor ranged from 400-80,000 spores/m3
In reviewing the many guidelines for acceptable quantitative levels of fungi in indoor environments, Rao et al.
(1996) found there is no uniform agreement among them. However, data reviewed by Gots and colleagues
(2003) suggest that current recommendations do not reflect the concentrations found in buildings in which the
occupants have no health complaints, and they do not reflect the levels that could be associated with health
problems.
As fungal concentrations are reported as either cfu/m3 or spores/m3, Klanova (2000) recommends that indoor
fungal concentrations >2000cfu/m3 should be considered a serious risk factor for health of occupants, whereas
Santilli and Rockwell (2003) state a concentration of >1000spores/m3 should be considered an unhealthy indoor
environment. In Czech Republic, Klanova (2000) found occupants of mouldy rooms where the average
concentration of fungi was 2476 cfu/m3 had health complaints such as cough, headache, rhinitis and sore throat.
4. Why are fungi a health problem?
Fungi in indoor environments are a problem for a number of reasons:

They deteriorate/damage surfaces

They cause unpleasant odours

They can cause an allergic response

They can be responsible for infections

They can cause other health problems
4.1 Surface damage
Fungi cause discolouration and deterioration of household surfaces e.g. the characteristic blackening of walls or
ceilings, wallpaper, grouting between tiles, plaster and around window frames in areas such as the bathroom.
Fungi are usually referred to as mould or mildew in this context.
Some fungi may also cause wood decay. Dry rot is a localised fungal infection of damp timber and will die when
the moisture is removed. Dry rot, which is more aggressive than wet rot, starts in wet timbers but can continue to
grow with a restricted moisture supply. The fungus can travel through brickwork and plaster in search of further
moisture spreading extensively through masonry to attack any timbers it meets.
4.2 Spores
The growth habitat of spore-forming fungi facilitates aerosol dispersal. Moulds produce millions of spores, which
are loosely attached such that even slight air currents will disturb the spores making them airborne. Due to their
small size (large spores are 10-20m, average 1-5m) spores easily stay airborne and may be respirable and
breathed deep into the airways. Spores are very tolerant to dryness, changes in temperature, UV light and some
chemicals. The spores may carry allergens and toxins, which are stable and may stay active even after the spore
has lost its viability.
4.3 Allergens
Some fungi do not produce infections but can cause allergic reactions. Fungal spores are generally recognised as
important causes of respiratory allergies, in both the lower and upper respiratory tracts (WHO 1998). Allergic
reactions usually occur at the site of allergen deposition. When larger fungal spores are inhaled, they are
deposited in the nasopharynx and are associated with nasal and/or ocular symptoms usually referred to as
hayfever (also known as rhinitis). Spores of <5m can penetrate the lower airways (Burrell 1991), where allergic
reactions will usually manifest as asthma.
4.4 Cell wall components
ß(1-3)-glucans are major cell wall components of mould. In a pilot study, Douwes et al. (1998) measured ß(1-3)glucan levels in house dust from floors and mattresses in 25 German homes, and was found to range from 1823507µg/dust. ß(1-3)-glucan levels per square metre were found to be positively associated with total culturable
fungi and Alternaria in house dust. In a larger follow-up study of 395 homes, a strong positive correlation was
found between concentrations of ß(1-3)-glucan per square metre and culturable mould spores. Additionally, there
was a correlation of ß(1-3)-glucan with culturable mould spore counts of Cladosporium and Alternaria per gram
of dust (Gehring et al. 2001). A study from Beijer et al. (2002) suggests that an inhalation challenge to ß (1-3)-Dglucan has an effect on inflammatory cells and this effect may be related to a chronic exposure to moulds at
home.
4.5 Mycotoxins
Some fungi produce secondary metabolites that are of valuable clinical use such as antibiotics. Other secondary
fungal products called mycotoxins are toxic to vertebrates and other animals. There are more than 300 known
mycotoxins. Aspergillus, Stachybotrys, Fusarium and Trichoderma produce mycotoxins. Mycotoxins are nonvolatile but exposure may take place through inhalation or skin contact with toxin-carrying spores or mycelium.
Mycotoxins associated with inhaled spores may be absorbed via the respiratory epithelium and translocated to
other sites, possibly producing systemic effects (Flannigan et al. 1991).
Stachybotrys atra (also referred to as Stachybortrys chartarum) produces very potent mycotoxins referred to as
satratoxins (Sorenson et al. 1987). It can grow on material with a high cellulose and low nitrogen content, such
as fibreboard, paper, dust and lint, particularly when moisture is present. Under field conditions, several
trichothecences have been detected in building materials heavily and naturally contaminated with S. chartarum
(Gravesen et al. 1999).
The chemical make-up and structure of mycotoxins is available in a recently published extensive review (Bennett
and Klich 2003).
4.6 Volatile organic compounds
Mould can also cause unpleasant odours (due to 2-octen-1-ol and geosmin) which are difficult to disguise.
Numerous fungi e.g. Aspergillus, Penicillium and Fusarium have been found to produce volatile organic
compounds (VOC) (Lewis et al. 1993). In buildings with visible mould growth, VOC at concentrations of 10100ng/m3 of air have been found (Keller et al. 1998). The total concentrations of microbial VOC correlated to the
odour perception in homes when cases have been classified in 3 groups: (1) fungus-like odour not recognisable
(<35 ng/m3), (2) slight fungus-like odour (50-1720 ng/m3) or (3) strong fungus-like odour (160-12,300 ng/m3).
Keller et al. concluded that concentrations above 50ng/m3 of air may indicate indoor mould contamination, while
outdoor concentrations are usually <10 ng/m3 air.
5. Fungal infections
Some fungi are pathogenic to healthy humans. Fungi cause superficial infections (or mycoses), where the fungus
grows at the body surface such as the feet, skin, hair and nails, as well as the oral or vaginal mucosa. The
important causative agents are the dermatophyte fungi of the genera Epidermophyton, Microsporum and
Trichophyton. They are spread by direct contact and are highly contagious and easily spread to other individuals.
Candida albicans can also cause superficial infections such as thrush and nappy rash. Candida infections are
usually the result of antibiotic therapy that suppresses the normal resident bacterial microflora allowing Candida
to flourish.
Infections within the body (deep mycoses) involve internal organs and are usually life- threatening. They are rare
in healthy humans. However, people with impaired immune functions (e.g. cancer patients receiving
chemotherapy or people with AIDS) are at significant risk of opportunistic fungal infections. They are acquired by
inhalation of spores or by entry through wounds, whilst some exist as part of the normal body flora (e.g. Candida)
and are innocuous unless the body’s defences are compromised in some way. Other opportunist fungi include
Aspergillus, Penicillium, Cryptococcus neoformans and Histoplasma capsulatum.
The numbers of susceptible and immunocompromised individuals is increasing such as people with HIV
infection, bone marrow and organ transplant recipients, cancer patients receiving chemotherapy, critically ill
persons and very low birth weight babies (Dixon et al. 1996). The incidence of hospital-acquired fungal
infections is increasing. Aspergillosis and candidiosis are the main causes of fungal infections in transplant
recipients and neutropenic patients. Infections caused by common indoor environmental moulds, such as
Aspergillus, Penicillium, Fusarium, Rhizopus and Alternaria, are increasing in HIV-infected patients (Cook et al.
1999). Also, oral candidiosis is often the earliest infectious complication encountered. Cryptococcosis has
become a major cause of illness in AIDS patients (Warnock and Campbell 1996).
6. Health problems associated with fungi
6.1 Allergies
An audit in 2001 by The National Asthma Campaign revealed that 1 in 8 children and 1 in 13 adults in the UK are
currently living with asthma. It is estimated that the number of people in the UK who are currently being treated
for asthma has grown to over 5 million. The US Centers for Disease Control (CDC) estimates that up to 20 million
people in the US have asthma, including 6.3 million children (CDC 2003a). It is important to note that asthma can
be initiated and provoked by many allergens commonly encountered in the general environment, for example
pollens (trees, grass) or house dust mites and not just moulds.
Over 80 fungal genera have been associated with symptoms of respiratory tract allergy (Horner et al. 1995).
Almost all microbial allergens are fungal in origin, with the major ones being Penicillium, Aspergillus,
Cladosporium and Alternaria (Burrell 1991). Penicillium and Aspergillus are more closely associated with
respiratory allergic symptoms and allergic sensitisation than the common outdoor moulds Cladosporium and
Alternaria.
Allergic responses to fungi may be immunoglobulin E (IgE) or immunoglobulin G (IgG) mediated. The most
common form of hypersensitivity to mould is immediate hypersensitivity or IgE mediated allergy to fungal proteins.
This can cause allergic rhinitis (hayfever) or allergic asthma, which is triggered by inhalation of fungal spores or
fragments. Up to 10% of the US general population have allergic antibodies to common moulds (Horner et al.
1995). Among patients with respiratory allergy, 2-80% are reported to be sensitised to fungi (Gravesen 1979,
Salvaggio and Aukrust 1981, Gergen et al. 1987, Nordvall et al. 1990).
Although in general only a small number of children are likely to have allergic reactions of clinical significance,
IgE-mediated respiratory allergy to fungi found in houses does occur in some atopic individuals (Flannigan et al.
1991). Penicillium is associated with allergenic symptoms in children with asthma and rhinitis (Li and Hsu 1997).
Fungi can also cause extrinsic allergic alveolitis (also known as hypersensitivity pneumonitis, HP), which presents
as recurrent flu-lie symptoms. HP results from an exaggeration of the normal IgG immune response against
inhaled foreign proteins that could be fungal.
6.2 Respiratory/Non-respiratory symptoms
Breathing mould can cause a number of respiratory symptoms, discomfort and disease. Mould may cause
respiratory infections such as sinusitis or bronchitis in children. Recurrent respiratory infections may also be a
sign of exposure to mould. Samson (1995) suggested that fungal volatiles affect the health of the occupants in
mouldy homes causing symptoms such as headache, tiredness, fatigue, fever and nausea. These compounds
may also irritate the mucous membranes and may cause symptoms in the eyes (itchiness or ‘runny’ eyes) and
the respiratory system (such as wheezing or coughing).
6.3 SBS/BRI
Sick building syndrome (SBS) is the occurrence of specific symptoms with unspecified aetiology, and are
experienced by people while working or living in a particular building, but which disappear after they leave that
building. Symptoms include mucous membrane, skin and eye irritation, chest tightness, fatigue, headache,
malaise, lethargy, lack of concentration, odour annoyance and influenza symptoms. The designation, sick
building syndrome, means that no specific etiological factor can be identified (Bennett and Klich 2003), although a
number of factors are suspected to be involved. Volatile organic compounds (VOCs) from fungi have been
implicated in SBS (Verheoff and Burge 1997).
When causal factors of the symptoms can be identified, e.g. Legionella, the term Building Related Illness (BRI) is
the appropriate term (Bennett and Klich 2003). BRI is an illness related to indoor exposures to biological and
chemical substances (e.g. fungi, bacteria, endotoxins, mycotoxins, carbon monoxide). Some people working or
living in a particular building experience BRI and symptoms do not disappear after leaving the building. Illnesses
include respiratory tract infections and diseases, legionnaires' disease, cardiovascular diseases and lung cancer.
7. Evidence linking presence of fungi in the home to health problems
Cough and wheeze are the two main symptoms investigated in relation to the home environment. A number of
studies have noted a strong relationship between mould growth in homes and respiratory symptoms.
7.1 Respiratory Illnesses
Platt et al. (1990) found a strong relationship between reports of mould growth and wheeze among children.
Higher levels of mycelia sterilia (heterogeneous group of non-sporing fungi) were found in homes of wheezing
children than in other homes (Strachan et al. 1990). In a Canadian study of children aged 5-8 years, upper
respiratory tract symptoms were increased by 20-25% in those living in damp homes (Dales et al. 1991b).
Koskinen et al. (1999b) found that Finnish pre-school children exposed to mould had significantly increased risks
of nocturnal cough and eczema, and they also had significantly more episodes of common cold than the nonexposed children. In a sample of 403 Canadian school children, a 12-50% increase in respiratory symptoms was
associated with reported mould growth, even after adjusting for presence of dust mite antigens and endotoxins
(Dales and Miller 1999). In Germany, the incidence of respiratory tract infections in children was significantly
associated with exposure to Penicillium spores (Muller et al. 2002).
Klanova (2000) found that occupants of mouldy rooms had health complaints such as cough, headache, rhinitis
and sore throat. In Poland, the presence of mould and or dampness in the home was significantly related to
hayfever, wheezing or difficulty in breathing in schoolchildren (Jedrychowski and Flak 1998).
Few studies have looked at the relationship between fungal levels and development of lower respiratory tract
illnesses (LRI) during the first year of life when children are in the process of developing immuno-competence.
Stark et al. (2003) explored this concept in the US in a prospective study of 499 infants. They demonstrated a
strong relationship between high levels of fungus in the household and an increased incidence of doctordiagnosed LRI (pneumonia, croup, bronchitis or bronchiolitis) in the first year of life. Importantly, the association
was independent of parent-reported visible mould or mildew. Airborne Penicillium, and dust-borne Cladosporium,
Zygomycetes and Alternaria were significantly associated with lower respiratory infection. In a cohort of 849
infants, Belanger et al. (2003) also examined the relations of exposure to allergens with wheeze and persistent
cough in the first year of life. Reported mould was associated with wheeze and persistent cough among children
with mothers with asthma, and associated with persistent cough in children whose mothers did not have asthma.
Air sampling of mould from the home demonstrated that measured mould was associated with wheeze among
children whose mothers had asthma.
Several studies have also been carried out on adults in Finnish homes. Pirhonen et al. (1996) found an increased
prevalence of reported respiratory infections/symptoms in adults reporting damp or mouldy homes. High
concentrations of airborne fungal spores were also related to health complaints from occupants (Reponen et al.
1989, Nevalainen et al. 1991). Koskinen et al. (1999a) found exposure to mould significantly increased risks of
respiratory symptoms such as rhinitis, sore throat, cough and common cold in adults.
In a sentinel case investigation, Johanning et al. (1999) reported on a family with a long history of moisture
problems and widespread visible mould growth on surfaces within their apartment. The daughter had a history of
recurrent bouts of pneumonia, bronchitis, sinusitis and asthma. The mother and brother also reported symptoms.
The daughter’s health improved when away from the apartment, but worsened on returning. A comparison was
made between environmental conditions in the apartment with outside and a control apartment with no visible
evidence of moisture or moulds problems and had healthy occupants. Inside the apartment 70-100m2 of surface
area were covered with mould growth. Airborne fungal counts were significantly higher that the outside or control
apartment. Predominant airborne fungi were Cladosporium, Aspergillus, Penicillium and S. chartarum. Samples
taken from the home had toxic metabolites in the fungal materials. The authors concluded that indoor fungal
exposure was the probable contributing cause of the health problems of the occupants.
7.2 Non-respiratory illnesses
A significant increase in the risk of non-respiratory symptoms such as fatigue and concentration difficulties has
been demonstrated in adults exposed to mould in their homes (Pirhonen et al. 1996, Koskinen et al. 1999a).
Koskinen and colleagues (1999b) also found that if schoolchildren had been exposed to mould, this significantly
increased their risk of nausea and led to difficulties in concentration. Mould in the home was a significant risk
factor for otitis in a sample of 304 children (aged 4-5yr) in Switzerland (Rylander and Megevand 2000).
VOCs have been implicated in sudden infant death syndrome (SIDS) (Verheoff and Burge 1997). Also, a greater
incidence of fungal growth was found in cot mattresses from babies who had died from SIDS compared to
controls (Kelly et al. 1992).
7.3 Asthma
There is evidence of an association between sensitisation and exposure to moulds and asthma. In people who
reported mould in their homes there was a significantly higher prevalence of positive radio allergo-sorbent test
(RAST) responses to Penicillium (Burr et al. 1998).
Burr et al. (1988) found that indoor mould was reported twice as frequently by asthmatics than controls. The most
common moulds isolated from the houses of asthmatics were Penicillium, Cladosporium, Stemphyllium,
Cephalosporium and Aspergillus. The commonest mould antibodies in the asthmatics were against Penicillium,
occurring more frequently in asthmatics that non-asthmatics. They were also more common in asthmatics with
mould in the home that in other asthmatics.
Several studies have found an association between doctor-diagnosed asthma in adults and children and living in
damp or mouldy homes (Dales et al. 1991a, Hu et al. 1997, Williamson et al. 1997, Thorn et al. 2001). In a
survey of over 10,000 Finnish students aged 18-25 years, living with mouldy and damp walls increased the risk of
asthma, as well as a greater chance of repeated colds (Kipelainen et al. 2001).
In Sweden, Norback et al. (1999) found that asthma was more prevalent among adults living in damp homes.
Immediate type allergy to moulds (Cladosporium or Alternaria) was also more prevalent in damp dwellings and
was related to current asthma in adults. Asthma was three times more common in adults with mould allergy.
Sensitisation to Alternaria allergens was more common among asthmatic schoolchildren that control subjects,
and Alternaria allergens were significantly associated with asthma in two schools (Perzanowski et al. 1998).
Results from the European Community respiratory health survey, involving a large sample of adults living in
different countries, showed that the severity of asthma was significantly associated with sensitisation to Alternaria
and Cladosporium (Zureik et al. 2002). In patients admitted to a hospital intensive care unit for asthma, 54% had
a positive result on skin testing for one or more fungal allergens, compared to 30% of patients not admitted to
intensive care (Black et al. 2000).
7.4 Allergies
T-helper (Th) cells regulate the development and maintenance of allergic disease. The balance between Th1 and
Th 2 cells plays a part in the regulation of IgE production and the induction of allergy. Muller et al. (2002) found
that T cells of children exposed to Aspergillus had a significantly lower content of Th1 cytokines producing cells.
Lehmann et al. (2003) investigated the influence of indoor mould exposure on T cell immunity during the first
years of life and the data suggests that mould reduces the number of Th1, especially interferon- producing cells,
and may be resulting in children exposed to mould being more susceptible to allergy. This is because the
reduction in Th1 cells promotes a Th2-dominated immune response, the basis for IgE mediated allergy (Lehmann
et al. 1999).
In West Germany there are higher prevalences of atopy and allergic conditions in children and adults.
Wichmann’s (1996) explanation is that there are higher concentrations of allergens (mites and moulds) due to
better home insulation and more frequent use of wall-to-wall carpeting.
In a study in Australia, Garret et al. (1998) found that asthma, atopy and respiratory symptoms in children were all
significantly associated with indoor exposure to fungal spores. Penicillium exposure was a risk factor for asthma,
while Aspergillus exposure was a risk factor for atopy. Fungal allergies were more common among children
exposed to Cladosporium or Penicillium in winter. Aspergillus exposure has also been associated with allergic
rhinitis in children in Germany (Muller et al. 2002).
In susceptible individuals, a link between respiratory allergy and mycosis and Aspergillus fumigatus isolated from
the soil of potted plants has been demonstrated (Staib 1984).
7.5 Illness associated with Stachybotrys atra
In the case of Stachybotrys, some researchers (e.g. Guhn and Ghannoum 2003) highlight that its presence does
not necessarily imply a cause and effect relationship with serious illness, and thus the causal link has not been
proven. However, in the absence of other causes there is a possible link, as demonstrated in the studies below.
The presence of the fungus S. atra in a house in Chicago was implicated in an outbreak of unexplained illness
among the occupants (Croft et al. 1986). A variety of illnesses were suffered over five years. The disease
symptoms were consistent with those of trichothecene toxicosis. During removal of the contaminated materials
and dust from the house, workers also suffered severe irritation of the respiratory system and skin. The
occupants’ illnesses ceased when the fungus was removed.
An asthmatic child living in a house with a mouldy, damp carpet experienced respiratory difficulties. The toxigenic
mould S. atra isolated from the carpet was found to be the cause. Removal of the carpet and treatment of the
floor underneath the affected area, resulted in reducing the child’s symptoms (Kozak et al. 1980).
S. atra was implicated in an outbreak of acute pulmonary haemorrhage among ten infants in Cleveland, Ohio
during 1993/4. Etzel et al. (1998) investigated the homes of infants with pulmonary haemorrhage and
hemosiclerosis, with specific attention to S. atra. Air and surface samples were collected from the room where
the infants were reported to have spent most time. The mean colony count for all fungi averaged 29227 cfu/m 3 in
homes of patients and 707 cfu/m3 in homes of controls. Mean concentrations of S. atra in the air were 43cfu/m3
in homes of patients and 4cfu/m3 in homes of controls. The results of the study suggest that infants with acute
pulmonary haemorrhage were more likely than controls to live in homes that had moulds, including S. atra, in the
air. Species of the genera Aspergillus and Penicillium were also abundant in the homes studied, which suggests
the possibility that metabolites of S. atra and other fungi may be present together.
In the bedroom of an infant found to have pulmonary haemaorrage, Stachybotrys spores (and other fungal
spores) were detected in air and surface samples. Part of the contaminated ceiling in a water-damaged closet of
the bedroom was found to contain several trichothecenes (Flappan et al. 1999).
Stachybotrys was isolated from lung fluid of a 7-year old boy who had suffered cough, fatigue and recurrent
pneumonia since the age of five. Surface cultures from his home were positive for Stachybotrys, which had
suffered extensive water damage (Elidemir et al. 1999).
7.6 Alveolitis
In damp areas of Japanese homes Trichosporon cutaneum may be present and is recognised as the major cause
of an alveolitis that occurs during summer (Yoshida et al. 1989).
Jacobs et al. (1986) reported a case in the US where the growth of Cladosporium on the wooden ceiling of an
unventilated hot-tub room was implicated in the alveolitis of a woman.
In Switzerland, the cause of allergic alveolitis in a woman was traced to a patch of mould in a bedroom wall
(Torokl et al. 1981).
8. Evidence linking presence of fungi in community settings to health problems
8.1 Hospitals
A cluster of 3 cases of cutaneous aspergillosis due to A. niger in one hospital led to a search for the source of
infection (Loudon et al. 1996). The infections occurred in neutropenic patients in a bone marrow transplant unit.
Environmental contamination was found in a ward kitchen adjacent to the bone marrow transplant unit. A. niger
was isolated from the top of two fridges, the vent of ice-making machine, microwave door and tea caddy.
Rhizopus was also isolated from the environment and was also isolated from a necrotic ulcer of one patient.
Aspergillus may have been carried from the ward kitchen to patients via contaminated food or fomites. No further
cases occurred in the unit after the ward kitchen was thoroughly cleaned.
Increased spore counts have been found in the air of haematological and transplant units that had building work
nearby or defective air filtration. This was associated with an increase in the rate of infection in patients (Walsh
and Dixon 1989).
8.2 Day care centres/schools
Among children attending a day-care centre (DCC), prolonged or frequent respiratory infections were found to be
associated with a serious mould problem of the building, whilst irritative symptoms were associated with milder
exposure (Koskinen et al. 1995). When exposure to moulds was reduced in the day care centres, there was a
lower frequency of respiratory infections amongst the children.
In a follow-up study, Koskinen and colleagues (1997) compared two DCC with mould problems to two control
DCC without mould problems. There were 229 children aged 3-7 years over two study periods. During the first
period, the children in the mouldy DCC had a significantly increased risk of sore throat, purulent and non-purulent
nasal discharge, nasal congestion, hoarseness and common cold. During the second period, a significantly
increased risk of purulent nasal discharge, nasal congestion, hoarseness and cough was observed. Upper
respiratory tract symptoms (sore throat, nasal congestion) were more prevalent among the children attending a
mouldy DCC. The mould-exposed children had such symptoms repeatedly or the symptoms were prolonged.
Savilahti et al. (2000) showed that exposure to moulds in a school building was associated with an increased
occurrence of respiratory symptoms and infections among the exposed children. More recently, Savilahti and
colleagues (2001) also found elevated IgE levels were significantly more common among the children exposed to
mould at school compared to a school with no mould problems. The school had visible water damage and mould
and the children had complained of respiratory and skin symptoms.
8.3 Other buildings
ß(1-3)-glucans have been implicated in sick building syndrome (SBS) contributing to eye and throat irritation, dry
couch and itching skin of office workers (Rylander et al. 1992). In a review of field studies, Rylander (1999)
concluded that there was a relation between exposure to (1-3)-ß-D-glucan as a marker of mould biomass and the
extent of symptoms of airway inflammation, fatigue and headache.
Hodgson et al. (1998) reported an outbreak of illnesses within a newly built courthouse and constitutional office in
the US. Within weeks after moving in, occupants described mucous membrane irritation, fatigue, headaches and
chest tightness. Some individuals were suspected of having interstitial lung disease. Moisture problems (window
and roof leaks and envelope seepage) began in 1987 and persisted through 1992. Inspection of the buildings
revealed the presence of approx. 100m2 of mouldy wallboard. More than 100 ceiling tiles were water-stained and
visually mouldy. Average concentration of cultural fungi indoors was 368cfu/m3 (considerably less than outdoors
which was 700cfu/m3). However, the type of fungi isolated from indoors was different to that outdoors. Indoors,
Aspergillus versicolour was present but was not detected outdoors. S. chartarum visually covered several ceiling
tiles in the library. Moisture-damaged interior surfaces in both buildings were also contaminated with Penicillium
species. This outbreak represents a likely human response to inhaled fungal toxins in indoor environments.
Johanning et al. (1996) evaluated the health status of office workers after exposure to fungal bio-aerosols,
especially S. chartarum and its toxigenic metabolites. There was widespread fungal contamination primarily in
offices, library and storage area, walls, stored books, catalogues, and of floor carpeting on the lowest floor level
where repeated water flooding had occurred. Widespread fungal contamination of water damaged material with
S. chartarum was found.
Other predominant indoor species – A. versicolour, A. niger, Pencillium and
Cladosporium and S. chartarum were found in ventilation ducts. On comparison to a control group of workers
with no exposure to the mould problem, it was concluded that prolonged and intense exposure to toxigenic S.
chartarum and other atypical fungi was associated with reported disorders of the respiratory and central nervous
systems.
9. Removal of exposure to mould
Successful removal of obvious fungal growth or mould will remove one reservoir of fungal allergens, but other
reservoirs such as carpets and soft furnishings will remain untouched. Fungal spores may continue to enter the
home environment from outdoors. The mould spores will not grow unless they reside on a surface where
moisture or damp is present. Thus, control of moisture levels indoors can go some way to preventing indoor
mould growth, e.g. not drying clothes indoors, prevent formation of condensation using suitable ventilation. Mould
is clearly recognised as a concern, for example the US Environmental Protection Agency (EPA 2003) has
produced a guide for the home on how to clean up residential mould problems and prevent mould growth, and a
guide on mould remediation in schools and commercial buildings (EPA 2001).
Several studies have shown that on removal of visible mould contamination from the environment or removal of
the people from exposure to the mould, their symptoms have ceased. If the mould growth is removed, the source
of the moisture/damp must also be resolved where possible. The CDC suggests that eliminating mould
throughout the home can help control asthma attacks (CDC 2003b).
In one report, some patients suffered severe respiratory symptoms after returning home from hospital (Fergusson
et al. 1984). Mould growth was found on a floor and the underside of linoleum. The patients only recovered fully
after treatment of the mouldy area and the house was thoroughly cleaned of contaminated material. Several
highly toxic tricothene mycotoxins were isolated from extracts of the contaminated material.
In a case report, five occupants of a house reported a number of illnesses over five years (Croft et al. 1986). In
the home it was found that a cold air return duct and some wood fibreboard were contaminated with
Stachybotrys. When the mould was cleaned up, the occupants symptoms subsided.
In Germany, an investigation of fungal contamination of indoor air in homes of patients with asthma bronchiale
found their homes had spore counts 4 to 40 times higher than that measured outdoors (Senkpiel et al. 1996). The
health complaints of the people decreased after their homes were renovated to remove mould problems or they
moved to another residence.
Stachybotrys was implicated as the cause of pulmonary hemosiderosis in a 7-year old boy following its isolation
from his home. When the boy was re-housed elsewhere and his symptoms resolved within a month (Elidemir et
al. 1999).
In a sentinel case, Johanning et al. (1999) reported that all the subjects showed a marked improvement and
partial resolution of their health problems after leaving their home (with a mould problem) for a time. When they
returned the symptoms and illnesses recurred or worsened.
When exposure to moulds was reduced in the day care centres, Koskinen et al. (1995) found there was a lower
frequency of respiratory infections amongst the children.
One study has assessed the effects of cleaning on indoor air quality. Air, surface and dust data obtained prior to
the cleaning program were compared with that obtained while the improved housekeeping program was in place
(Franke et al. 1997). Following improved housekeeping, airborne dust mass was 43-56% lower, airborne fungi
levels decreased by 57-67%, non-floor surface fungi were reduced by 25%, and carpet dust fungi decreased by
40%. The results of the study indicate that an improved cleaning program contributed to measurable
improvements in the indoor air quality.
10. Efficacy of chemicals against fungi
Unlike bacteria or viruses, fungi are often a visible problem. In their study, Garrett et al. (1998) found that 60% of
households removed mould growth in the house on a regular basis. Mould may be removed by cleaning but the
spores can survive and regrowth may occur. Regrowth may also be due to release of viable spores into the air
during removal and cleaning of mould from surfaces, which after some time may resettle on surfaces and reestablish new growth. Thus, chemical disinfection is usually required to kill the spores or chemicals required to
inhibit further growth. Fungal spores are usually more resistant to disinfectants than vegetative bacteria but more
susceptible than bacterial spores. The bactericidal efficacy of disinfectants has been extensively reported.
However, there is less published data on the fungicidal efficacy of disinfectants, especially in relation to the
home. Studies have tended to focus on disinfectants used in food processing, hospitals or pharmaceutical
applications.
Akamatsu et al. (1996) investigated the antimicrobial effect of benzalkonium chloride, chlorhexidine gluconate,
povidone-iodine and ethanol against the yeast C. albicans and filamentous fungi (Mucor racemosus, Rhizopus
nigricans, A. niger, A. terreus). C. albicans was rapidly killed by all disinfectants within 1 minute in absence of
organic matter. In contrast, the other fungi were moderately resistant, requiring between 15 and 120 minutes
contact for complete kill, depending on the disinfectant concentration and presence of organic matter.
The effectiveness of commercial disinfectants against clinical fungal isolates was investigated by Terleckyj and
Axler (1993). Both dermatophytes (T. mentagrophtes, E. floccusum) and opportunistic fungi (A. fumigatus, A.
versicolor) were exposed to agents such as quaternary ammonium and phenolic formulations. The quaternary
ammonium formulations were unable to completely kill all four fungi within 15 minutes, and still had no effect on
the Aspergillus species after 60 minutes. The phenolic formulation was not fungicidal for the opportunistic fungi
within 15 minutes. However, Ohta et al. 1996 demonstrated that 0.2% benzalkonium chloride (BAC) completely
killed clinical fungal isolates including C. albicans, C. tropicalis and C. parapsilosis within 15 minutes at 25ºC. At
0.2%, BAC also killed A. niger in 1 hour, and A. terreus and Trichophyton rubrum in 30 mins. BAC is also very
effective at inhibiting mould growth and can give long lasting protection to treated surfaces, and is therefore often
present in domestic anti-mould treatments.
Virkon, a disinfectant containing peroxygen compounds, was ineffective at 1% after 15mins contact against mould
spores (Penicillium verrucosum and Absidia corymbifera) in a basic suspension test (i.e. no organic soil or water
hardness present) in accordance with AFNOR guidelines (Hernandez et al. 2000). The manufacturer
recommends the product for high-level disinfection on surfaces and equipment in hospitals at 1% for 10mins.
The activity of hospital disinfectants was measured against T. mentagrophytes, A. niger and C. albicans (Scott et
al. 1996). Hypochlorite at 0.2%, gave 99.99% kill in 10mins of all species, whilst Andrews (1996) found that
0.37% hypochlorite efficiently killed A. flavus, A. niger and P. chrysogenum within 2 minutes.
Huang et al. (1998) examined the effects on 9 commercial disinfectants against 34 fungi relevant to food
manufacturing. The fungi tested included Penicillium, Aspergillus, Alternaria, Fusarium and Cladosporium, which
are relevant to the mouldy home environment. Only ethanol at 70% concentration inactivated all fungi (within 10
minutes). Sodium hypochlorite (200µg/ml) was effective against 25 of the fungi within <0.5mins and 7 fungi within
5-10mins. In the presence of 0.1% yeast extract, sodium hypochlorite was only effective against Fusarium solani
and Cladosporium cladosporioides within 5-10mins.
Mould is characteristically coloured, for example Cladosporium has characteristically black hyphae and spores
pigmented with melanins. Other moulds found in the home environment produce colourless hyphae but melanin
pigmented spores. Pigmented yeasts such as pink Rhodotorula spp. may also colonise damp surfaces, alone or
co-existing with mould. The chemical stability of melanins means that surface staining may persist even when the
fungi have been killed (Jacobsen et al. 1994). Due to the colouration of mouldy surfaces, sodium hypochlorite is
one of the most widely used chemicals against mould, in order to bleach the colour. However, sodium
hypochlorite does not leave any residual activity on surfaces, so regrowth is a problem soon after cleaning. Thus,
chemicals such as benzalkonium chloride, which is effective at inhibiting mould growth, are used in preventative
products and detergents.
11. Conclusions
In homes without damp or high levels of moisture, the levels of airborne fungi will tend to be the same as
outdoors. Outdoor concentrations will depend on location and will vary depending on the season, temperature,
humidity, weather, etc. However, the presence of houseplants, pets and moulds brought indoors on footwear or
clothing, as well as dust will affect the levels indoors. However, there is no uniform agreement on the acceptable
levels of mould in the indoor environment.
This paper has looked at the evidence for associations between presence of fungi (mould) and/or damp in
domestic or community settings and reported health effects in occupants of those settings. It has not evaluated
the evidence in occupational settings known to have high levels of fungal spores such as agricultural settings.
There is a large amount of evidence to suggest that several health affects, primarily affecting the upper and lower
respiratory tract, are associated with exposure to mould within the domestic and community settings. These
health effects include respiratory symptoms, non-respiratory symptoms, asthma, allergies, infections and
pulmonary disease.
When indoor fungi has been associated with infections rather than allergies or respiratory symptoms, this has
been in people with suppressed immune systems such as hospital patients or patients recently discharged from
hospital. Only a few fungal species are capable of causing infections in healthy people, and this is usually due to
skin being moist and/or damaged or broken.
There is no doubt that fungi produce allergens. As exposure to mould does occur indoors and outdoors it is
sometimes difficult to determine where the initial sensitivity arose. However, subsequent allergic symptoms may
be related to presence of mould in the home.
There is substantial evidence for an association between home dampness and/or mould exposure and lower
respiratory symptoms in children. Studies on children’s health are the most reliable because the effects of
smoking and occupational exposures are absent. Studies on adults’ health have also shown that damp and or
presence of mould is associated with increased prevalence of respiratory symptoms and/or asthma. However, it
is important to highlight that in some studies, the relationship may have been enhanced because of the increased
awareness of such associations by respondents of surveys. Exposure to mould does not always result in health
problems. However, measures should be taken to prevent mould growth indoors because some people are, or
may become, allergic to it.
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