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Dr. Jackson Kung’u (PhD)- Mold Specialist.
Phone: 905-290-9101
Mobile: 437-556-0254

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Bacteria As Contaminants In Indoor Environments

People spend around 80 and 90% of their time in indoor environments (office, school, home, etc) and there is increased awareness of the potential health effects of indoor biological contaminants such as bacteria. Therefore, when considering work or indoor living conditions, the air quality requires special attention.

In indoor environments, biological contaminants are often found in areas that provide conducive conditions for microbial growth. These include damp or wet areas such as cooling coils, humidifiers, condensate pans, draperies, bedding, carpet, and other areas where dust collects.

Bacteria are an important component of indoor biological contaminants. Some of them are pathogenic (that’s they are capable of causing disease) and are involved in respiratory diseases. If the environmental and nutritional conditions are favourable bacteria can colonize and grow on many surfaces (including standing water) from where they and their by-products can become airborne. A number of diverse activities can result in the dispersion and generation of bacterial aerosols indoors, for example, the operation of heating-ventilation-air conditioning systems, hot water systems and water spray devices.

Health Effects Associated With Indoor Bacteria
There are several health effects associated with exposures to bacterial aerosols. Some of them include irritative and nonspecific respiratory symptoms, respiratory infections, and allergic reactions such as alveolitis and chronic bronchitis.

Some of the infectious bacteria include Mycobacterium tuberculosis, Legionella pneumophila, Bacillus anthracis. These bacteria cause pulmonary tuberculosis,  legionellosis (Legionnaire’s disease) and anthrax respectively. Infection is primarily through inhalation.

Bacteria As Causes Of  Bioderioration
Bacteria are rarely thought of as biodeterioration agents. However, they are involved in biodeterioration of various types of materials. Bacillus sp, Nitrosomonas sp, Nocardia sp and Streptomyces are involved in biodeterioration of diverse materials in several regions. They cause physical damage and some are capable of producing acids that cause biochemical deterioration.

Conclusion
In general, several microorganisms including bacteria are present in indoor environments. They can contaminate indoor air and pose health risks especially when certain species are present or when they are in high numbers. Apart from the health effects microorganisms have the ability to cause damage to materials they are growing on.

Biodeterioration

Biodeterioration is a terminology used to describe any undesirable change in the properties of a material caused by the vital activities of organisms.

Fungal growth requires suitable temperature, moisture and air (oxygen). Fungi are heterotrophs that acquire nutrients by absorption. They secrete hydrolytic enzymes (exoenzymes) and acids to decompose complex molecules into simpler ones that can be absorbed and used as nutrients. Hence, they are believed to be potential contributors to biodeterioration of different kinds of materials containing cellulose, silicate mineral (mica and orthoclase), iron and magnesium-bearing minerals (biotite, olivine, pyroxene) etc.

Fungi cause biodeterioration to many materials including:

  • building materials
  • animal feeds
  • electrical equipment
  • food including meat, fruits and grains
  • fuel including jet fuel
  • glass and optical equipments
  • gunpowder
  • leather
  • monuments
  • paint
  • paper
  • tobacco etc.

 How are Fungi involved in biodeterioration?

The rate of biodeterioration depend on prevailing environmental conditions and the fungus involved. There are different mechanisms of biodegradation. These include microbial corrosion, hydrocarbon degradation and biodegradation of cellulose.  Aspergillus niger, Chaetomium globosum, Scopulariopsis brevicaulis, Trichoderma koningii, Trichothecium roseum and Eurotium chevalieri are cellulolytic fungi. Their efficiency to degradate cellulosic (cellulose containing) materials is due to their ability to produce large amounts of cellulase enzymes. 

Stachybotrys chartarum is a common fungus growing on paper (such as that covering gypsum wallboard) in damp buildings.

Some fungi cause blue stain and soft rot of wood, discolouration and loss of strength of cotton materials.  Many fungi spoil food in storage. Aspergillus flavus grows on peanuts and many other substrates, producing a mycotoxin called aflatoxin, which contaminate food and causes liver damage. Fusarium graminearum grows on feed corn and produces the  mycotoxin zearalenone that causes oestrogenic syndrome in animals.

Through the action of excreted oxalic and citric acids fungi can deteriorate marble, limestone, granite and basalt. Several species of fungi are involved in biodeterioration of stone monuments in different countries. Some of these fungi are Aspergillus elegans, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger, Aspergillus versicolor, Alternaria sp, Cladosporium cladosporioides, Cladosporium sphaerospermum, Cunninghamella  echinulata, Curvularia lunata, Fusarium roseum,  Gliocladium virens, Penicillium crustosum, Penicillium glabrum, Penicillium chrysogenum (=Penicillium notatum), Rhizopus arrhizus.

Biodeterioration is a problem worldwide. Several control measures have been applied to prevent the biodeterioration. These include use of fungicides, biological control, prevention of biodeterioration by control of environmental conditions, periodic cleaning of dirt, dust and spores, and use of radiation.

Testing Carpets For Mold

Carpets are reservoirs of health hazard particulates including mold spores, dust mites, and animal hair. These particulates are allergenic to some people when inhaled. Mold spores are very tiny and easily become airborne when the carpet is disturbed as people walk in the house or when the carpet is being cleaned.

Cleaning the carpet with a good vacuum cleaner on regular basis significantly reduces the number of settled mold spores and other particulates. In fact there is no need to test carpets for mold if they are well maintained.

Carpets can be tested for:

  • Settled mold spores
  • Mold growth.

To test a carpet for settled spores a dust sample is required. Dust can be collected from an area of 1 square meter. It’s important to ensure that enough dust is collected to enable the laboratory perform both culture analysis and direct microscopic examination of the dust.  

When is it necessary to test a carpet for mold growth? You can test a carpet for mold growth following water damage if the carpet was not completely dried within 48 hours. This test may involve cutting a piece of carpet from the affected area and sending it to the laboratory for testing.