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This document is also available as a PDF. Fungi and the indoor environment. Fungi can lead to health problems ranging from hay fever to cancer.
It is important to know when and how to sample for these organisms,
as well as how to interpret the results. Fungi are eukaryotic organisms and include yeasts, molds and mildews,
as well as large mushrooms and puffballs. Fungi can exist as single
cells, such as yeast, but are more commonly found as thread-like hyphae.
Hyphae usually branch out extensively ,with the collective mass of
interwoven filaments being referred to as mycelium. Fungi normally
reproduce by forming spores which may result from either sexual or
asexual processes. The spores can range in size from less than 2 microns
([[micro]meter]) to more than 100 [[micro]meter]. Most fungal spores
disperse through the air, although some are specialized for other
forms of dispersion, such as via water or insects. Allergic Reactions to Fungi The health effects noted from fungi are typically a result of their
spores. Repeated heavy exposures to fungal spores may result in two
different types of allergic reactions, Type I and Type III. in Type
I, or "immediate reaction," repeated exposures to the offending agent(s),
over a period ranging from months to years, may eventually result
in an overreaction of the immune system. Once the immune system has
been triggered, even minute amounts of the specific allergen can elicit
an allergic reaction. An estimated 8 percent of the adult allergic
patients and 20 to 25 percent of children in the population suffer
Type 1 allergic reactions to fungi, which implies some type of genetic
predisposition. Patients with this disposition produce immunoglobulin
E (IgE) antibodies in larger amounts than "normal" people. The overstimulated
production of these antibodies then creates a hyperreaction which
induces allergic reactions, such as rhinitis, hay fever or asthma,
within a matter of minutes after exposure. Type III, or "Arhus" reactions, are mediated by IgG and IgM antibodies,
not IgE. The resultant immune complexes will initiate different inflammatory
responses, which may result in asthma. This condition is typically
associated with occupational diseases, including farmer's lung and
wood trimmer's disease, and is frequently referred to as "hypersensitivity
pneumonitis" or "extrinsic allergic alveolitis." In this case, the
symptoms occur approximately 4 to 8 hours after exposure, and include
general malaise, flu-like symptoms, fever and muscle and joint pains.
Physical findings can often include signs of severe oxygen deficit
and abnormal crackling sounds in the lungs, called "rales." Long-term
exposure can lead to fibrosis of the lung tissue. Fungi and Mycotoxins Several mold species, including Aspergillus, Fusarium, Penicillium
and Stachybotrys, can produce a wide variety of nonvolatile chemicals,
commonly referred to as "mycotoxins." Even in low concentrations,
these chemicals can cause adverse health effects, including skin
irritation, pathogenic disease, cancer and immune disorders. Unlike
allergens, mycotoxins elicit toxic responses in virtually all individuals
who come in contact with them. Aspergillus flavus, a common indoor
fungus, produces aflatoxins, notoriously potent animal carcinogens.
However, A. flavus is capable of producing other toxins, as well.
Penicillium, while unable to produce aflatoxin, may produce 100 or
more different classes of mycotoxins. Stachybotrys, one of the more famous mycotoxin producers, has been 1 of 4 7/25/99 3:27 PM Printable Document-Electric Library Personal Edition http://business.elibrary.com/s/elbe/getd...ydocid=120586@library_i&dtype=0~0&dinst= implicated in a number of health-related cases, including the hospitalization
of 10 infants in Cleveland in the fall of 1994 for pulmonary hemorrhaging.
Various species of Stachybotrys, as well as Fusarium, can produce
marcocyclic trichothecenes, which have potent adverse effects on the
immune system, as well as with protein synthesis. Stachybotrys chartarum
produces at least five different trichothecenes, which are both dermotoxic
and cytotoxic. In one study, an extract of the various Stachybotrys-
produced trichothecenes was given to rats. It resulted in their deaths
within 24 hours. Reported health symptoms of exposure to S. chartarum
include signs of cold and flu, sore throat, diarrhea, headaches, chronic
fatigue and dermatitis. The toxic effects of ingesting moldy foodstuffs can include acute
and chronic damage to the liver, kidneys, gastrointestinal tract,
heart, central nervous system and the immune system. There have been
numerous documented cases of fatalities due to ingestion of fungal
contaminated food. Mycotoxins also can enter the body via inhalation or contact with
the skin. Inhalation of mycotoxins is a much more potent route of
exposure, compared with ingestion. In most cases, the dose required
can be an order of magnitude less when inhaled. Adverse health effects
have been noted in individuals who came in contact with Stachybotrys,
suggesting that the toxins were absorbed through the skin. In one
study, a majority of the workers exposed to airborne dust from straw
on the floor of a room developed acute symptoms indicative of mycotoxicoses. Fungi also produce a wide range of volatile organic compounds (VOCs),
consisting mainly of alcohols, ketones, hydrocarbons and aromatics,
many of which have distinct odors. These VOCs, which are sometimes
referred to as microbial VOCs or MVOCs, are typically what cause the
characteristic musty or dank smell which people associate with mold
growth. The most common compounds include 3-methyl-1-butanol, 3-octanol,
3-octanone and 1-octen-3-ol. Odor thresholds for some MVOCs are very
low, as low as 1 part per trillion (1,5-octadien-3-ol). Studies are
currently being conducted to try to determine the intensity of sensory
irritation and potential adverse health effects caused by MVOCs. Conditions Necessary for Growth Without sufficient amounts of moisture, a growth substrate and some
type of organic nutrient base, microbial amplification simply will
not occur. Many fungi grow quite well on any cellulose-rich material,
such as wallboard or ceiling tiles, particularly when there is a
high level of moisture present. However, fungal growth and amplification
can occur virtually anywhere, including carpets and HVAC systems,
as long as the three elements are present. Molds have been observed
growing on a variety of unusual substrates, including fiberglass piping,
photographic paper, synthetic rubber and creosote-treated wood. Most
fungi prefer warm temperatures, although some can grow at near-freezing
temperatures, while others can grow at temperatures as high as 35
to 40 C. Moisture can be introduced to the indoor environment through a variety
of means. Water intrusion through the building envelope is a common
problem in older buildings. Lack of building maintenance can often
result in roof leaks and/or water leaking through the outer walls.
Numerous cases of poor or misguided construction in the humid South
has resulted in vapor barriers being installed on the wrong side of
the exterior wall. This, in turn, results in condensation occurring
on the interior walls, which are typically constructed of cellulose-
rich wallboard. Bathrooms, which by nature are humid environments,
frequently are not properly vented, resulting in moisture accumulating
on the walls. 2 of 4 7/25/99 3:27 PM Printable Document-Electric Library Personal Edition http://business.elibrary.com/s/elbe/getd...ydocid=120586@library_i&dtype=0~0&dinst= Too often, damage caused by water is discounted or treated lightly
until microbial growth and its associated odors have become a problem.
Microbial amplification can occur within a relatively short period
of time after water infiltration. Fungi may start to grow and produce
new spores within 24 hours, if sufficient air is also present. These
microcolonies are not visible to the naked eye; however, if humid
conditions continue, fungal growth on indoor surfaces may become rapidly
visible. Once fungal growth and amplification have begun, it is often
difficult to eradicate the problem without having to completely abate
the infected materials. Inspecting and Sampling for Fungi When performing an investigation, the inspector should not arbitrarily
take air samples for fungi. Results from air samples can be confounding
and may inaccurately represent conditions within the indoor environment.
Fungal spore levels often fluctuate widely over the course of a day,
and a single air sample reflects only a momentary situation. In addition,
the origin of the spores often remains unknown. Certain fungi, such
as Stachybotrys, have sticky spores and are very rarely airborne.
In these cases, air sampling methods will be prone to false negative
results and should not be used to rule out contamination. Surface sampling of building materials often provides more reliable
information about contamination, since other sources of fungal spores
do not confuse the results. Swab, tape or bulk samples can be collected
wherever there is visible growth to determine the actual species present.
When taking bulk samples of water-damaged wall board, always take
a core sample, since fungi are often found growing on both the front
and back sides. A boroscopic examination of the back side can be invaluable
when trying to verify the presence or absence of visible growth and
to assist in determining sampling locations. Both variable and nonviable fungal particles are important in relation
to health effects. Therefore, when performing air sampling, collect
both types of particles. A variety of techniques have been developed
for volumetric sampling of fungi in the environment. Viable sampling
is usually performed using an Andersen or similar impaction sampler
which pulls air across an agar plate at a flow rate of 28.3 1/min.
Small particles are deposited upon this plate,which is subsequently
incubated and the resultant colonies identified and enumerated. Counts
are then converted to the number of colony-forming units (CFU) per
cubic meter of air sampled. There are a variety of different types
of agar which can be used, depending upon the type of fungi being
sampled. No one agar is ideal for all types of fungi, although malt
extract agar (MEA) is a good general purpose agar for screening. When
sampling specifically for Stachybotrys, cornmeal agar (CMA) or Czapek
cellulose agar (CCA) are more suitable. Nonviable particles are typically collected using a spore trap sampler,
such as the Burkhard or a slit impaction device, such as the AIR-
O-CELL Bioaerosol Cassette. Air is pulled through the sampler and
particles deposited on a grease-coated glass slide. The samples are
then microscopically examined and the total number of spores per cubic
meter determined. Tentative identification of many types of spores
can also be made, though typically only the genus (i.e., Penicillium)
can be ascertained. Sampling can also be accomplished by using membrane
filters, which can then be cleared and stained with biological dyes.
When performing any type of air sampling, samples must also be collected
outside the building in order to determine background levels of both
total spore counts and specific species present. Outdoor samples should 3 of 4 7/25/99 3:27 PM Printable Document-Electric Library Personal Edition http://business.elibrary.com/s/elbe/getd...ydocid=120586@library_i&dtype=0~0&dinst= be taken in proximity to the building's fresh air intakes. It is good
practice to take at least one sample in a "noncompliant" area of the
same building to determine if an unusual exposure situation exists
in the subject area in comparison with a symptom-free environment. Interpretation of Results There are no "official" standards or guidelines for fungal or bacterial
bioaerosols. Some researchers have expressed the opinion that 100-
250 CFU/[m.sup.3] are acceptable, provided no opportunistic fungi
are identified. The same range is also used by the U.S. Public Health
Service, Federal Employee Occupational Service Region III. A range
of concentrations proposed by the World Health Organization and Health
Canada suggests that microbial concentrations below 50 CFU/[m.sup.3]
for a single species (other than common outdoor fungi), 150 CFU/[m.sup.3]
for a mixture of species reflective of the outdoor air spores, or
500 CFU/[m.sup.3] during the summer for common outdoor fungi (such
as Cladosporium) are acceptable. There are other ranges (called background
numbers or guidelines) used by organizations such as the American
Conference of Governmental Industrial Hygienists (ACGIH) and OSHA,
but for the most part, these numbers are arbitrary. Since there are no generally accepted guidelines to follow regarding
airborne fungi, indoor results must be interpreted with respect to
the control samples. In general, mechanically ventilated buildings
should have indoor fungal counts that are lower than those found outside.
In addition, the species found inside should be similar to those identified
outside the building. A situation can be considered unusual when fungal
levels in the complaint area are an order of magnitude or greater
than those found in the control areas. The presence of any slimy-spored
toxigenic fungi, such as Stachybotrys chartarum and Fusarium moniliforme,
should be considered unusual, and may suggest an indoor contamination
source. The consistent detection of some fungi, such as Aspergillus,
Paecilomyces, or various species of Penicillium, could indicate water
damage and subsequent fungal amplification. Bulk and wipe sample results can give a strong indication as to whether
or not a material is contaminated. Contaminated samples will often
result in a pure culture or a mixture of no more than two to three
types of fungi. A high fungal level which is dominated by one or two
fungi is indicative of fungal amplification. Materials which are found
to be contaminated should then be either removed or decontaminated
with some form of fungicide. John Springston, CIH, CSP, is the director of Indoor Environmental
Quality Services for Ambient Labs, Inc. and a past president of the
Metropolitan New York AIHA Local Section. Ambient Labs, a consulting
firm based in New York City, performs investigative and proactive
IAQ testing in over 55 million square feet of building space every
year. COPYRIGHT 1998 Penton Publishing Inc. Springston, John P., Fungi and the indoor environment.. Vol. 60, Occupational Hazards, 10-01-1998, pp
143(4). Copyright © 1998 Infonautics Corporation. All rights reserved. - Terms and Conditions 4 of 4 7/25/99 3:27 PM |
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