To Order
Toxic Effects of Some Common Indoor Fungi
--by Chin S. Yang, Ph.D., printed in Enviros,
The Healthy Building Newsletter, Volume 4, Number 9, September 1994
In the September 1994 (Vol. 4, Number 9) edition of Enviros
entitled "Aerobiology of the Office Environment," the issue of
mycotoxins in indoor environments was briefly mentioned. An explosion of
cases related to toxigenic fungi and mycotoxins have been reported or discovered
throughout the United States and Canada over the last three years.
Courthouses in Florida were closed for extensive decontamination, with costs as
much as the price of the original building. Recently, an old school
building in Canada, infested with toxigenic fungi, had to be burned. This
extreme measure underscored the importance of indoor fungal problems.
Furthermore, the unusual weather conditions in many parts of the U.S.A. over the
last three years have provided conditions for the growth of toxigenic fungi and
potential human exposure to mycotoxins and other secondary fungal metabolites.
What are toxigenic fungi and mycotoxins?
Some fungi have been known to produce toxins that are
harmful to animals and humans when ingested, inhaled or in contact with the
skin. The fungi that produce toxins are known as toxigenic fungi.
The earliest known toxigenic fungi, primarily Claviceps purpurea,
produce the substance ergot. The ergot fungi infect rye, grains and
other grasses. Ingestion of ergot contaminated rye or other cereals causes
ergotism. There are two types of ergotism recognized clinically:
gangrenous and convulsive. Gangrenous ergotism affects the extremities as
well as causes gastrointestinal symptoms. Convulsive ergotism affects the
nerve system causing brain and spinal lesions which can lead to death or
permanent mental impairment.
Many fungi in addition to ergot fungi produce secondary
toxic metabolites, such as alkaloids, cyclopeptides, and coumarins.
Metabolites that can produce adverse health effects (mycotoxicoses) in animals
and humans are collectively known as mycotoxins. The latest World Health
Organization (WHO) publication on mycotoxins, available in 1990, indicated that
there are more than 200 mycotoxins produced by a variety of common fungi.
Historically, mycotoxins are a problem to farmers and food industries and in
Eastern European and third world countries. However, many toxigenic
fungi, such as Stachybotrys chartarum (also known as Stachybotrys
atra) and species of Aspergillus and Penicillium, have
been found to infest buildings with known indoor air and building-related
problems.
In addition to mycotoxins, volatile organic compounds
(moldy odors) released from actively growing fungi may also pose a health risk.
What are the common toxigenic fungi found indoors?
Many species in the genera Aspergillus, Penicillium
and Cladosporium are known to produce mycotoxins. These three
groups of fungi are also very common indoors. Other toxigenic fungi
frequently found indoors are Alternaria, Trichoderma, Fusarium,
Paecilomyces, Chaetomium, Acremonium.
Another fungus that has increasingly been linked to
building-related problems is Stachybotrys chartarum. It is common
in nature and grows on cellulose-rich plant materials. It has frequently
been found to grow on water-damaged cellulose-containing materials, such as
dropped ceiling tiles, wall paper and sheet-rock wall board, in residential and
commercial buildings. Many indoor air quality related problems have been
traced to the growth of this fungus in buildings. Almost without
exception, these buildings have usually had chronic water or moisture problems.
When discussing mycotoxins, species of Aspergillus
deserve special attention. Species of Aspergillus produce such
well known toxins as aflatoxins, ochratoxins, and sterigmatocystin.
Aflatoxins that are produced by Aspergillus flavus and Asp.
parasiticus are detected in stored peanut and grains. Ochratoxins are
produced by many species of Aspergillus as well as Penicillium.
Sterigmatocystin is produced by Asp. versicolor.
These fungi grow well on many common building materials soiled or damaged by
water. Their ability to grow on common building materials makes them a
significant problem in buildings where maintenance is poor or non-existent.
What are the health effects of mycotoxins?
Mycotoxins may cause a variety of short-term as well as
long-term adverse health effects. This ranges from immediate toxic
response and immune-suppression to the potential long-term carcinogenic effect.
Symptoms due to mycotoxins or toxins-containing airborne spores (particularly
those of Stachybotrys chartarum) include dermatitis, recurring cold and
flu-like symptoms, burning sore throat, headaches and excessive fatigue,
diarrhea, and impaired or altered immune function. The ability of the body
to fight off infectious diseases may be weakened resulting in opportunistic
infections. Certain mycotoxins, such as zearalenone (F2 toxin), can cause
infertility and stillbirths in pigs. Because these symptoms may also be
caused by many other diseases, misdiagnoses of mycotoxin exposures are
common. There are very few physicians with the experience or
expertise in correctly diagnosing mycotoxin exposures or mycotoxicoses.
Occupational or building-related exposures to mycotoxins through inhalation are
slowly being recognized as a major indoor air quality problem. Generally,
removal of causative agents is necessary. Treatment for symptomatic
mycotoxicosis may be required. If exposure to fungi and mycotoxins is
suspected, consult an occupational health professional.
What are the options to avoid toxigenic fungi and
mycotoxin related problems?
Fungal growth in an indoor environment is often related to
the availability of nutrient, water/moisture, proper temperature range and the
presence of inoculum (often fungal spores). The key factor is
water/moisture. Moisture control to reduce condensation and free
water will prevent or control fungal growth.
In an environment where water/moisture-related problems
often lead to fungal growth, rapid response to the problem is the key
solution. Fungi-infested materials should be removed and replaced
(see also below). Materials that can not be replaced should be
decontaminated or treated. Consult an environmental microbiologist
for such decontamination treatments. Proper project design and
procedures are an important factor in a successful decontamination project.
Biocidal application may be necessary under certain conditions. More
importantly, before any decontamination is performed, water and excessive
moisture must be controlled and eliminated.
Most importantly, fungal infestation may be directly
correlated with building operation and maintenance. Spores of Stachybotrys
chartarum are wet and slimy. They do not easily become airborne.
Their dissemination is likely through insects (such as cockroaches), rodents,
water incursion or air stream. Without the assistance of insects, rodents
and free running water, the likelihood of Stachybotrys chartarum
spreading from one location to the other requires the disturbance of a dried
slimy spore mass. Spores and hyphae of S. chartarum have been
detected in air samples. Any detection of S. chartarum spores in
indoor air should be considered significant.
To prevent or eliminate fungal infestation in
buildings, the following procedures should be observed:
- Heating, ventilating and air-conditioning systems must
be properly filtered and maintained.
- Water intrusion must be taken care of within 24 hours.
Never overlook small leaks. Ignored small leaks are much more
problematic than a properly handled major flood. For additional
information on the proper handling of water intrusion, please see Enviros
Vol. 3, No. 8 (August 1993); back issues are available.
- Proper handling and storage of food to keep insects and
rodents away from buildings.
- In a warm, humid climate, a building engineer should be
consulted to make sure that a moisture barrier is properly installed and
that no condensation will occur.
- Install dehumidifiers in areas where humidity is
constantly high. Keep relative humidity below 60% or ideally at or
near 50%.
- (print is unreadable)
- If large areas of contamination are determined,
asbestos-like remediation procedures are necessary. Consult an
industrial hygienist with experience in asbestos remediation procedures, as
well as in biohazard remediation.
If a building is known to have extensive fungal growth,
consult an industrial hygienist with training and experience in microbiological
control. Human and environmental protection must be observed when removing
and handling fungal contaminated materials.
For further information contact:
Frank A. Lewis, Director
Office of Environmental Hygiene
U.S. Public Health Service
Division of Federal Occupational Health
Region III
Mailing Address: 3535 Market Street, Room 1310
Philadelphia, PA 19104
