Dampness, Mould and Indoor Air

The Issue

There are a number of factors that can lead to unhealthy air in your home or workplace, including lack of ventilation, too much humidity, and water infiltration or leakage, among others. Poor indoor air quality can cause a number of health problems such as breathing difficulties and allergies.

Background

Because Canadians spend about 90% of their time indoors, the quality of indoor air is very important. Humid or damp conditions in your home can encourage the growth of mould and the proliferation of dust mites. In addition, unless you use a vacuum cleaner with high efficiency filters, mould spores, bacteria, and other microbial contaminants can build up on floors, carpets, and upholstery.

Moulds are fungi that grow in damp environments. Their spores contain allergens and irritants. Mould can develop anywhere there is moisture, such as on walls where there is water condensation, or in buildings that experience leakages or flooding. Mouldy smells from carpets, wood, and gypsum board are a sign that they contain fungi. Stale water in humidifiers and air conditioners can also lead to the growth of bacteria and fungi. Air filters also collect dust and contaminants and should be cleaned and replaced as the manufacturer advises.

A major cause of poor indoor air quality is a lack of fresh air - that is, not enough exchange of air between the outside and inside, which can lead to excessive humidity. Mechanical ventilation such as a fan or dehumidifier may be needed in parts of the home that are particularly damp.

The Health Risks of Poor Air Quality

Health Canada considers mould growth in residential buildings to be a potential health hazard.

People living in buildings where mould grows are more likely to suffer from health problems, especially symptoms such as coughing, wheezing, and headaches. Asthmatics are especially at risk as mould may trigger asthma attacks.

Minimizing Your Risk

Improving indoor air quality is fairly simple. Here are several steps you can take:

• Control the humidity and let more air into your home by ensuring sufficient ventilation. This will prevent moisture from building up on walls and windows. Where there is a lot of water vapor, mechanical ventilation such as a fan may be needed to get rid of it.
• Measure humidity by using a hygrometer (an inexpensive tool available at most hardware stores), to see if you need a de-humidifier. You are advised to keep the relative humidity in your home below 50% in summer and 30% in winter.
• Repair leaky roofs, walls, and basements.
• Clean mouldy surfaces with a detergent.
• Keep your home clean and dust-free.
• Regularly clean and disinfect humidifiers, de-humidifiers, and air conditioners.

If there is dampness or a mould problem in your home, contact the Canada Mortgage and Housing Corporation (CMHC) for advice or contact your regional health department. Talk to your doctor if you think anyone in your family suffers from health problems caused by poor indoor air quality.

Government of Canada's Role

Health Canada has issued residential air quality guidelines on moulds. In addition, Health Canada has published a number of pamphlets and reports about indoor air quality. The Canada Mortgage and Housing Corporation (CMHC) also has several publications on ways to avoid excess humidity in your home and improve indoor air quality.

Health Canada and CMHC are currently working on joint research projects on air quality in homes. These studies are aimed at measuring concentrations of chemical and biological contaminants in indoor air and identifying their sources.

Need More Info?

For further information, please see these publications available from Health Canada and CMHC:

Health Canada - Publications on health and air quality
Or contact:
Health Canada
Air Health Effects Division
269 Laurier Avenue W., A.L.. 4903-C
Ottawa ONON K1A 0K9
Tel: (613) 957-1876
E-mail: air@hc-sc.gc.ca

Related documents:

Health Canada's guidelines on moulds in residential indoor air

Fungal contamination in public buildings: health effects and investigation methods

For more information on humidifiers please see the It's Your Health article on cool mist humidifiers.

For more information on moisture and mould in your home visit the Canada Mortgage and Housing Corporation series “About your House”
Or call : 1-800-668-2642

For more information on hygrometers.

For additional articles on health and safety issues go to the It's Your Health Web site.
You can also call toll free at 1-866-225-0709 or TTY at 1-800-267-1245*.

Updated : April 2007
Original : September 2002
© Her Majesty the Queen in Right of Canada, represented by the Minister of Health, 2007