Mold: Indoor Fungal Infestations and Mycotoxicity
Guidance for Medical and Public
Key Messages for Health Care Providers
Mold particles are complex mixtures of biological chemicals, some
having allergenic or toxigenic properties. Although it is
scientifically necessary to understand the pharmacological effect of
fungal compounds in isolation, exposure occurs in concert.
In theory, there are four ways in which molds could produce or
aggravate human illness:1) Type I immune reactions, including allergic
rhinitis or asthma; 2) Type III immune reactions, such as
hypersensitivity pneumonitis and allergic aspergillosis; 3) Toxic
reactions to mold products (mycotoxins); and 4) Irritation to mucous
membranes through mold-produced volatile organic compounds (VOCs).
There are no confirmed cases of mycotoxicity, via inhalational
exposure, in residential or office settings. In contrast, toxic
effects following the ingestion of moldy food by livestock and people
are well documented. Allergy is the health effect normally ascribed to
inhaled molds. A few cases have correlated, but not confirmed,
pulmonary hemosiderosis and pulmonary pneumonitis to the presence of
mold in the home. Documented cases of non-allergic health effects
to humans following inhalation of molds have occurred in occupational
settings, primarily in the handling of grain and animal feed. In
these and other occupations involving the generation of biological
particulates, there is a risk of chronic exposure to inhaled mycotoxins
greater than that expected in residential or office settings.
Evaluating a health effect from mold requires both a medical diagnosis
and an environmental assessment. The presence of mold in
a building does not in itself constitute a health threat. The
control of indoor mold infestation, by cleaning and resolving moisture
problems, is usually sufficient to protect public health. In some
cases, a health-based assessment of the indoor environment and occupants
may be preferred to verify the degree and extent of the problem.
Such a determination is critical in deciding upon a potentially disruptive
and expensive course of action in a large commercial or public
building. The health assessment should include:
Potential for exposure: An evaluation of health effects from
mold exposure should be made within the context of molds prevalent in
the environment, including the quantity and profile of fungi present in
bulk and air samples. Airborne mold, measured by colony-forming
units (CFUs), is normally more abundant outdoors than indoors during the
growing season, while the representation of mold species is normally
proportional indoors and out. In the case of indoor infestation, the
relative representation of mold species changes. For example,
Cooley, et al.,1 based on a study of 48 schools,
report that in outdoor air in mild temperate regions of North America,
five fungal genera predominate: Cladosporium (81.5%), Penicillium
(5.2%), Chrysoporium (4.9%), Alternaria (2.8%), and Aspergillus
(1.1%). In outdoor air samples Cladosporium were about
24-fold more predominant than the next-most common mold, Penicillium.
Indoors, Cladosporium predominated over Penicillium in
similar proportion, although total CFU counts were 3-4 fold
lower. Inside mold complaint buildings, Penicillium sp.
were much more common, Cladosporium being only about 3-fold more
predominant. Furthermore, in 20 of 48 schools with indoor air
complaints, Penicillium sp. were dominant, being 4.7-fold more
abundant in air than Cladosporium. Such changes in species
representation are diagnostic of indoor mold infestation, but not of
actual exposure. Similarly, changes in species profiles do not
necessarily indicate an imminent health threat.
Medical diagnosis, to determine if health complaints are consistent
with mold exposure: Health complaints may be
related to other indoor air quality problems, such as other sources of
allergens, carbon monoxide, or volatile organic compounds.
Exposure to these contaminants must also be considered and ruled out
with respect to the patientís symptoms/condition.
Verification of exposure: Strict criteria, such as
those suggested in the sidebar, should be adopted in order to accurately
establish links between the presence of molds having potential health
effects and occupantís health complaints. These criteria should
include evidence of exposure ("abundant" allergen in indoor
air; serum IgE to same allergen), and symptoms of allergy following
clinical exposure to the allergen.
- The presence of mold in a building does not in itself constitute a
health threat. Therefore, the remediation of mold and water damage
in buildings should be based on non-clinical factors, unless otherwise
indicated medically. Usually, controlling water leaks and humidity
in the building is the main public health recommendation.
- The perception of indoor mold as a pervasive public health threat
often leads to costly environmental assessments, monitoring, and
remediation. To avoid unwarranted remedies, there is a need for
improved communication and education between public health, the medical
profession, environmental professionals, elected officials, and the
public. The key messages are: the ubiquitous distribution of fungi
in the environment, the types and amount of fungi normally found
indoors, the risks posed by the molds detected, and options for
confronting the problem.
|Evaluating the role of molds in
"sick building syndrome."
Bernstein has suggested an approach to
suspected building-related illness that includes:2
- a thorough history (duration and nature of symptoms, home
environmental and workplace history, past medical history,
- a physical exam;
- exclusion of more common infectious causes;
- phenotyping the patient as atopic versus non-atopic (skin
testing to seasonal and perennial allergens including a mold
panel [or corresponding serologic testing], spirometry
- chest x-ray or high-resolution CT of chest (to determine if
pulmonary findings consistent with hypersensitivity pneumonitis
are present and require additional evaluation);
- supportive testing including serologic testing for specific
IgG, IgE, or IgA to mold (including Stachybotrys),
hypersensitivity pneumonitis screen (precipitating antibodies),
and consideration of humoral and cell-mediated immune system
- environmental assessment including walkthrough, air sampling,
and measurement of known perennial allergens, irritants (VOCs
and chemicals [nitrous dioxide, sulfur dioxide, ozone]), dew
point, and mycotoxins;
- measurement of total symptom scores in and out of the
- measurement of peak expiratory flow rates in and out of the
environment event every 2-3 hours while awake and correlation
with environmental exposure measurements; and
- consideration of specific provocation test (nasal challenge
preferred to the more risky bronchoprovocation).
1Cooley DJ, Wong WC, Jumper CA, Straus DC.
1998. Correlation between the prevalence of certain fungi and sick
building syndrome. Occup. Env. Med. 55: 579.
2 Bernstein JA. The
role of the allergist in building related illness. In: AAAAI (American
Academy of Allergy, Asthma, and Immunology) 58th Annual
Meeting. Handouts on CD-ROM [CD-ROM]. AAAAI; 2002.
PPH 45051 8/2003
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August 12, 2014