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​​​​Mould

​Do you think you have mould in your home? Here's what you need to know.

What is it?

Moulds like mushrooms and yeast are part of the fungus family. They look like a light to dark-coloured fine woolly growth. Some are helpful and some are potentially harmful if inhaled or swallowed.

Where is it found?

Ideally, there should be no mould in the home. Moulds can be found indoors and outdoors. They can potentially grow on any moist surface, such as damp bathrooms and basements. The types of moulds that are associated with indoor air quality problems prefer to grow on wood products or building materials covered with wood products, such as paper coated drywall.​

How can I be exposed to mould?

Exposing or disturbing mould-covered materials can release seeds of mould, called spores, into the air. Exposure occurs if people inhale or accidentally ingest these spores. 

How can I find it in my home?

Mould can grow anywhere there is water damage, high humidity or dampness. Look for the following signs that you may have a problem.

Musty smell: Sometimes moulds are hidden and cannot be seen. A musty or earthy smell often points to their presence. Even when a smell is not noticed, wet spots, dampness or evidence of a water leak are signs of moisture problems and mould may follow.

Discolouration: Discolouration can signal a problem. Mould can be any colour: black, white, red, orange, yellow, blue or violet. Dab a drop of household bleach onto a suspected spot. If the stain loses its colour or disappears, it may be mould, if there is no change, it probably isn’t.​

Is it a​ health hazard?

The majority of common moulds are not hazardous to healthy individuals. The health risk depends on the type of mould you are exposed to and the level of your exposure; some types can produce toxic chemicals known as mycotoxins. Mycotoxins can cause illness in persons who are sensitive to them or when persons are exposed to large amounts in the air. 

Those more at risk are:

  • Pregnant women

  • Infants

  • Older adults

  • People with health problems, such as asthma, allergies or a weakened immune system

​What are the potential health effects?

Short term: The effects can range from being insignificant, to causing allergic reactions and illness. The effects depend on the type of mould present in a home, the amount and degree of exposure as well as the health condition of the occupant. Symptoms will usually disappear when you leave the contaminated environment.

Long term: Long term exposures have been associated with re-occurring flu-like symptoms, headaches, rashes and impaired immunity. Some moulds can cause more serious health problems, but these are uncommon.

If you or someone in your home is experiencing suspected mould-related symptoms, see your physician. Keep in mind that your symptoms may be caused by many other illnesses. ​​

How do I remove It?

In many cases, moulds are confined to areas near a water source. Removing the cause of the water problem is critical. All roof, window, plumbing or foundation leaks must be repaired in order to eliminate the problem.

Protect yourself first. While cleaning, always wear:

  • Mask

  • Safety goggles

  • Rubber gloves

Bleach is NOT recommended for clean-up

Small area (no larger than one square metre, and less than three patches): use soap and water and proper protective equipment

Moderate area (more than three patches each smaller than one square metre OR larger than one square metre but smaller than three metres or the size of a 4' x 8' sheet of plywood): professional help recommended but you can also clean up on your own using soap and water and proper protective equipment

Large area (larger than a piece of 4' x 8' plywood): professional help required. If you are a tenant of a rental property you can contact your local City Property Standards office for assistance in working with the landlord to have the necessary repairs completed.


Environmental Health

519-753-4937 ext. 470