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").

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


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