Mold Information

Learn More About Mold and Bacteria

Common Building Molds (also called Mildew or Black Mold) and Their Associated Health Effects

People often talk of black mold or mildew in their bathroom, ceiling, basement and kitchen.
The question you may ask, is it a single type of mold? No. In most cases, more than one type of mold will be growing on the same surface. At least 150 mold species have been reported from residential and commercial buildings. Fortunately, not all of these are harmful to most people, so even if you suspect mold growth, don’t panic; but make you have it tested at the earliest.

If you want to know more about specific molds, visit the Mold Library.

If you are looking for a professional to help you with mold testing or remediation, check out our professional directory.

What Are the Health Effects Of Indoor Mold?

Exposure to indoor mold has been associated with the following health problems:

  • Lower respiratory symptoms such as coughing and wheezing
  • Respiratory infections such as aspergilloses
  • Allergic diseases, including allergic asthma and bronchitis
  • Non-inflammatory, unspecific symptoms, such as eye and skin irritation, fatigue, headache, nausea, and vomiting



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Which Molds and Why Do They Grow Indoors?

The level of moisture (usually referred to as water activity) in building material determines not only whether mold will grow or not but also the types that colonize the material. Damp materials with a water activity value equal to or greater than 0.90 are usually colonized by strains of Aspergillus fumigatus, Trichoderma spp., Exophiala spp., Stachybotrys spp., Phialophora spp., Fusarium spp., Ulocladium spp., and yeasts such as Rhodotorula spp. Materials with a water activity value ranging from 0.90 – 0.85 are colonized by Aspergillus versicolor while those with water activity values of 0.85 or slightly less are colonized by Aspergillus versicolor, Eurotium spp., Wallemia spp., and Penicillium spp., such as Penicillium chrysogenum and Penicillium aurantiogriseum.

A study conducted in Denmark found that water leakage through roofs, rising damp, and defective plumbing installations were the main sources for water damage with subsequent mold growth.

The building materials most susceptible to mold attacks were water damaged, aged organic cellulose containing materials such as wood, jute, wallpaper, and cardboard. In this study, the molds that were most frequently encountered were Penicillium (68%), Aspergillus (56%), Chaetomium (22%), Ulocladium (21%), Stachybotrys (19%), Cladosporium (15%), Acremonium (14%), Mucor (14%), Paecilomyces (10%), Alternaria (8%), Verticillium (8%), and Trichoderma (7%). These molds are all known to cause different types of inhalation allergy. The species most frequently encountered were Stachybotrys chartarum, Penicillium chrysogenum, and Aspergillus versicolor.

If you’re interested in learning more about mold and bacteria, you can explore the links above to the left. If you’re curious or concerned about anything not covered here, please use the Question Form.

Interested in having an in-depth understanding? Check our Resources page which will provide you with links to other educational materials.


Mold & Bacteria Consulting Laboratories (MBL) Inc
1020 Brevik Place, Unit 1A • Mississauga, ON   L4W 4N7 • Canada • phone: 905-290-9101 • toll-free: 1-866-813-0648 • fax: 905-290-0499.

204 – 4475 Wayburne Drive • Burnaby, BC  V5G 4X4 • Canada • phone: 604-435-6555 • fax:604-435-6553.