Fungi as Indoor
Contaminants
by
Dr. Nenad Vidovic, PhD., B.Sc.
Health
& Well Being
Preventing illness associated with in-house microbial
attacks should be a prime consideration in choosing and protecting
construction materials.
iNSERT
Figure 1 photo
with Caption:
After the cradle was removed, The Sansin Corporation discovered the
culprit causing the babyıs ailments. They applied antiseptic treatment to
the area infected with toxic moulds and advised the customer to place
better insulation the bungalow foundations.
PHOTO: The Sansin Corporation
Case Study #1: A bungalow owner told The Sansin Corporation
that he "found ants everywhere in the house" and asked the
company how to get rid of them. During an in-house inspection, he
also mentioned that his son was having problems. "My child looks
overtired and constantly exhausted, his cough won't quit and he is apt to
cry until his nose bleeds," the customer said. Sansin had reported
information on treating the ant problem in The Sansin Report of October
2000 (SEE
"Making a Bee Line for Lumber").
The diagnosis
of the lad's troubles: it was found hidden behind his cradle as shown in
the above photo.
Case
Study #2: The Sansin Research Centre received for laboratory
evaluation five zip-lock bags filled with damp, mouldy wood shavings that
were scratched from the surfaces of I-profile beams in the basement of a
residential building. The area had been subject to intense flooding and
leaking that had resulted in an increase in moisture content as well as
considerable surface discoloration. Multiple micro-organisms were isolated
from the suspect materials. Most were identified as toxic mould fungi that
are known to contribute to numerous health problems.
Case Study #3: Several compartments in a professional building in
Victoria, BC were considerably damaged due to exposure to high humidity.
Water intrusion through cracks and window gaps created excellent
conditions for microbial development.
The environment was so unsafe that most of the inhabitants had to be
evacuated. The Sansin R&D Center was retained as a consultant to
evaluate the problem and recommend remedial treatments. Accordingly, they
obtained samples of damp, mouldy, ligno cellulosic material. They secured
the suspect material in double-walled plastic containers and kept it
refrigerated. Upon evaluating the samples under sterile conditions, they
found that they harbored multiple, mouldy microorganisms. The cultures
differed in colour (white to pale orange, yellowish green, darkish green
and black) as well as in mat appearance (powdery and/or slimy). The
predominant ingredients of this "culture collection" were
Aspergillus sp. (the dark green mould), Chaetomium sp. (the olive green
mould) and Stachybotrys sp. (at first light brown, but turned to black
green, sometimes fully black). Additional laboratory tests were undertaken
to evaluate the effectiveness of two antiseptic chemicals for destroying
the kind of toxic moulds that are typically found in damp buildings.
Test
Results
Laboratory
experiments showed that household bleach (chlorine) is highly toxic
against moulds in damp buildings. A concentration of 1% or a little higher
is a good remedial treatment (Figure 2 A). Hydrogen peroxide is another
efficient treatment for most but not all moulds (Figure 2 B). Some species
died after treatment with this chemical but revived a few days later by a
process called hyphal multiplication. It seems that hydrogen peroxide is
effective in killing the spores (reproductive organs) but not the hyphae
(vegetative organs) of fungi.
They
are everywhere around us
Most
of the above-mentioned fungal microorganisms are known to have adverse
health effects on the inhabitants of damp structures. The moulds attack
virtually any damp organic material (wood, drywall, wallpaper, fabric
materials, as well as paints and latexes containing no anti-fungal
additives). The spores of these fungi are invisible (5 to 25 microns in
diameter). They are everywhere around us in the form of air-borne
organisms. When widely dispersed in the air, they are not significantly
hazardous, but as soon as the spores settle down on damp surfaces, they
"return to life" making an invisible mycellial network that acts
as a carrier for billions of spores.
When generated in huge masses, the spores are dark (black, green, etc.),
hence the discolouration of construction materials. When sporulation
(spore release) begins, the air can quickly become thick with spores,
creating a hazardous environment. Like any living organism, moulds
permanently release their products of metabolism (the fungal equivalent of
urine and fecal matter), most often in the form of mycotoxins (gases
produced by fungi that are toxic to humans and animals). If multiple
organisms infect the same substrate, moulds release extra toxic
metabolites in order to inhibit competitors. A number of studies have
confirmed that these compounds can harm human health. For example, Indoor
Air Solution Inc. reports that living in a mouldy environment can cause
eye and skin irritation, respiratory difficulties, headaches and chronic
fatigue. In recent years, other research projects have investigated a
possible link between toxigenic moulds and some cases of Sudden Infant
Death Syndrome (IMNG/Pediatric News 1999). Most authors agree that the
Stachybotrys and Aspergillus species of fungi are most often involved in
home contamination.
When
Moulds Attack
Mould cleanup in the
case of small-scale contamination is fairly easy, providing the
contaminated surfaces are easily accessible. A simple water solution of 1%
chlorine is sufficient to wash away the mould. At the same time, steps
should be taken to cut sources of excessive humidity (such as leaky roofs
and walls and plumbing; condensation; washing-machine flooding; and sewer
backups). Once the cleaned surface is dry, any remaining dead and
surviving fungal remnants can be eliminated by vacuuming the suspect
surfaces with vacuum cleaners equipped with a High Efficiency Particulate
Air (HEPA) filter that can eliminate particulates down to 0.3 microns with
an efficiency of 99.99%. Workers performing these tasks should wear
appropriate respiratory protection to avoid inhalation of clouds of toxic
spores and dust. As an additional safeguard, contaminated material should
be packed in plastic bags and discarded. For premises that are permanently
damp, air cleaning devices are an excellent means of keeping air-borne
spores to minimum concentrations. The cleaners must also be equipped with
HEPA filters that are regularly removed for cleaning and/or replacement.
INSERT Figure 2 photo
with caption:
Getting rid of
moulds in the case of large-scale contamination is more difficult as there
is little chance of killing contaminants on hard-to-reach surfaces and in
hidden cavities. Places that are not well ventilated are prime targets for
more severe contamination. In such cases, considerable demolition and
reconstruction work, followed by antimicrobial treatment, is required.
Only qualified experts should perform large-scale toxic-mould abatements.
During clean-up, contaminated sites must be isolated from clean areas to
minimize the spread of dust laden with fungal spores.
Preventative Measures
To prevent microbial contamination, it is best to perform
antimicrobial treatment during the construction process. At the last,
treatment should be applied to locations that are hard to reach or hidden
behind regular walls.
The Sansin Corporation's experiments suggest that the application of
environmentally safe fungistatic compounds are an effective means of
providing permanent microbial control in premises inhabited by humans.
They believe that the problems associated with the "Sick Building
Syndrome" can be greatly reduced by using construction materials that
have been treated with mould-resisting formulations based on Boron
compounds such as Boracol 10-2 BD (SEE "Wood
Preservatives").
NOTICE
The above text is based on The Sansin Corporation's knowledge of routine
mycological work, literature studies and results gained through tests at
their laboratory facilities. However, they are not registered in the field
of microbial identification and abatement and they assume no
responsibility for the consequences of following any part of the given
guidelines.
Reprinted with permission.
All rights reserved.
The Sansin Corporation
3377 Egremont Drive
Strathroy, Ontario
N7G 3H6 Canada
519/245-4623 bus
519/245-4759 fax
www.sansin.com
info@sansin.com
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