Health Effects and
Symptoms Associated with Mold Exposure
Health Effects and Symptoms Associated with Mold Exposure
When moisture problems occur and mold growth results, building
occupants may begin to report odors and a variety of health
problems, such as headaches, breathing difficulties, skin
irritation, allergic reactions, and aggravation of asthma symptoms;
all of these symptoms could potentially be associated with mold
exposure.
All molds have the potential to cause health effects. Molds produce
allergens, irritants, and in some cases, toxins that may cause
reactions in humans. The types and severity of symptoms depend, in
part, on the types of mold present, the extent of an individual's
exposure, the ages of the individuals, and their existing
sensitivities or allergies.
Research on mold and health effects is ongoing. This list is not
intended to be all-inclusive.
The health effects listed above are well documented in humans.
Evidence for other health effects in humans is less substantial and
is primarily based on case reports or occupational studies.
Specific reactions to mold growth can include the following:
-
Allergic Reactions
Inhaling or touching mold or mold spores may cause allergic
reactions in sensitive individuals. Allergic reactions to mold
are common - these reactions can be immediate or delayed.
Allergic responses include hay fever-type symptoms, such as
sneezing, runny nose, red eyes, and skin rash (dermatitis). Mold
spores and fragments can produce allergic reactions in sensitive
individuals regardless of whether the mold is dead or alive.
Repeated or single exposure to mold or mold spores may cause
previously non-sensitive individuals to become sensitive.
Repeated exposure has the potential to increase sensitivity.
-
Asthma
Molds can trigger asthma attacks in persons who are allergic
(sensitized) to molds. The irritants produced by molds may also
worsen asthma in non-allergic (non-sensitized) people.
-
Hypersensitivity Pneumonitis
Hypersensitivity pneumonitis may develop following either
short-term (acute) or long-term (chronic) exposure to molds. The
disease resembles bacterial pneumonia and is uncommon.
-
Irritant Effects
Mold exposure can cause irritation of the eyes, skin, nose,
throat, and lungs, and sometimes can create a burning sensation
in these areas.
-
Opportunistic Infections
People with weakened immune systems (i.e., immune-compromised or
immune-suppressed individuals) may be more vulnerable to
infections by molds (as well as more vulnerable than healthy
persons to mold toxins). Aspergillus fumigatus, for
example, has been known to infect the lungs of
immune-compromised individuals. These individuals inhale the
mold spores which then start growing in their lungs.
Trichoderma has also been known to infect immune-compromised
children.
Healthy individuals are usually not vulnerable to opportunistic
infections from airborne mold exposure. However, molds can cause
common skin diseases, such as athlete's foot, as well as other
infections such as yeast infections.
Why is there
controversy about the health effects of exposure to mold growth?
Not all health effects of molds are controversial. Fungal infections
are well known. Fungal allergies are also well known and accepted
among medical experts, although the allergens themselves are poorly
characterized. Infections and allergies have objective and
well-established clinical effects. These effects can be measured and
reproducibly demonstrated, and the mechanisms are fully understood.
The health effects caused by consuming moldy food or feed that
contains mycotoxins are also well known. Regardless of these
controversies, mold growth in the built environment is unacceptable
from the perspectives of potential adverse health effects and
building performance.
Other health effects have been proposed for mold metabolites that
are irritants or mycotoxins, and plausible mechanisms exist for
health effects due to these mold metabolites. However, the clinical
relevance of these mycotoxins and irritants under realistic airborne
exposure levels is not fully established. Further, supporting
evidence for other health effects is based on case studies rather
than controlled studies, nonreproduced studies, or subjective
symptoms.
Case studies do indicate the possibility or plausibility of an
effect. Unfortunately, such studies cannot address whether an effect
is common or widespread among building occupants. Results from
nonreproduced studies may be false or are not confirmed by
well-designed follow-up studies. In large epidemiological studies,
general symptoms have been associated with moisture-damaged and
presumably moldy buildings. Many of the reported symptoms are
subjective and difficult to quantify. Results are confounded by the
fact that the association is general, and mold is not the only
possible cause of the symptoms. Neither condition proves that mold
is not a cause.
Since much remains unproven, controversy has developed around the
presumed health effects attributed to mycotoxins. This controversy
is intensified since the health effects are often serious and
sometimes are claimed to be permanent. Dampness in buildings is
associated with respiratory effects, but the extent to which mold
contributes to these effects is unknown. Some health effects from
mold exposure remain controversial because of the potentially
significant consequences; yet crucial and legitimate scientific
questions remain unanswered. Our incomplete knowledge of
noninfectious health effects related to mold exposure is due to
limited research support and lack of documented health effects in
the context of well-defined exposures. Bear in mind that
environmental investigations must also be interpreted in context
with medical and epidemiological information for infectious diseases
from environmental sources. For example, finding Legionella
colonization of a water supply serving an immunocompromised
population would have potential health significance whether or not
there were cases of infection, but finding mold spores in ambient
air has little significance unless people are getting sick from
direct exposure.
Why are there
no standards for mold exposure? Health
hazards from exposure to environmental molds and their metabolites
relate to four broad categories of chemical/biological attributes.
These materials may be: 1) irritants, 2) allergens, 3) toxins, and
rarely 4) pathogens. Different mold species may be more or less
hazardous with respect to any or all of these categories. However,
risks from exposure to a particular mold species may vary depending
on a number of factors. Uncertainty is complicated further by a lack
of information on specific human responses to well-defined mold
contaminant exposures. In combination, these knowledge gaps make it
impossible to set simple exposure standards for molds and related
contaminants.
What are the
knowledge gaps concerning mold exposure and its health effects? Chief
among our knowledge gaps are: (1) defining how mycotoxins affect
human health and (2) the health risks associated with mycotoxin,
microbial volatile organic compound, allergen, and glucan exposures,
particularly the proposed response to Stachybotrys mycotoxins
associated with hemosiderosis.
However, the etiology of infectious fungi is relatively well
understood. Conversely, mechanisms responsible for allergic
sensitization, contact dermatitis, hypersensitivity pneumonitis, and
inhalation fevers vary from incompletely characterized to entirely
unknown. Predisposing host factors, presumably under genetic
control, influence individual susceptibility to environmental
exposures. The psychogenic/psychosocial contribution to mold-related
illness remains elusive.
The lack of meaningful exposure limits for most indoor air quality
contaminants is a major obstacle to establishing regulatory
standards for individual exposure to airborne contaminants. The same
is certainly true for molds. Until microbiological methods for
demonstrating mold concentrations in the environment are
standardized and reproducible, epidemiological studies necessary to
determine dose-response can only suggest association, not cause and
effect, with respect to mold exposures and health effects.