Dampness, Mould and Human Health

Mould is a natural part of the environment, but it can become a problem if it finds a damp place to grow inside your home. Indoor mould growth can lead to breathing problems and allergy symptoms for some people. To prevent mould, fix any moisture problems right away and control humidity levels in your home.

Moulds are fungi that grow in damp environments. With enough moisture, mould can grow on many surfaces, including wood, drywall, insulation, ceiling tiles, cardboard, paper and fabric. Excess moisture can be caused by leaks and floods, too much humidity, or condensation on windows and walls. Stale water in humidifiers may also lead to growth of mould and bacteria. Not all mould is visible, so check for signs of water damage or for an earthy smell that may mean you have hidden mould growth.

The Health Risks of Poor Indoor Air Quality

The Nova Scotia Department of Health and Wellness (NSDHW) considers mould growth in residential buildings to be a potential health hazard. People living in buildings with dampness or mould are more likely to suffer from symptoms like eyes, nose and throat irritation, coughing, wheezing, shortness of breath or other allergic reactions. Being exposed to mould can also trigger asthma symptoms.

Some people are quite sensitive to mould, while others will not react at all. NSDHW recommends removing any mould found in your home and fixing the underlying moisture problem that allowed it to grow in the first place because there is no safe amount of mould.

Talk to your doctor if you think anyone in your family suffers from health problems caused by mould or poor indoor air quality.

Reduce your Risk

The key to preventing mould is preventing excessive moisture through proper home maintenance. Follow these simple steps:

• Repair any leaks right away
• Use kitchen and bathroom exhaust fans when cooking and showering
• Make sure clothes dryers are properly vented to the outside
• Make sure tubs and sinks are sealed tightly so water doesn’t leak into the walls
• Humidity in the house should be kept at or below 50% in the summer, and 30% in the winter. If needed, use a dehumidifier
• Mould can grow on fabrics, paper, wood and practically anything that holds moisture, so these items shouldn’t be stored in damp areas like basements
• Regularly clean and disinfect humidifiers and de-humidifiers
• After a flood, be sure to completely dry the wet area within 48 hours.

If you discover a small or moderate amount of mould, you can generally clean it yourself. For washable surfaces, put on some rubber gloves, wear eye protection and a dust mask, and wash the mould away with water and dish detergent. There’s no need to use bleach. If a material is heavily covered with mould, or if it is not possible to wash it, consider replacing the material.

Be sure to fix the moisture problem that allowed mould to grow in the first place.

If you have a large amount of mould (covering an entire wall or found in multiple areas), you may want to consider hiring a professional. A large amount of mould is often caused by a major moisture problem that may require professional help to fix, like a leak in your home’s exterior wall, foundation or plumbing system.

Should I test for mould?

If you have mould growing indoors, you should remove it and fix the moisture problem that allowed it to grow. All moulds can cause health problems and there is no “safe” level of indoor mould, since everybody is different in their sensitivity to mould. So testing often doesn’t tell you any more than you already know.

If you think you may have a mould problem, start with a visual inspection of your home. Look for stains or discolouration on floors, walls, window panels, fabrics and carpets. Check for a musty, “earthy” smell. Not all mould is obvious. It can grow inside walls or above ceiling tiles, so it is important to check for mould anywhere that is damp and especially where water damage has happened. If needed, contact an expert to help.

What if I rent my home?

Ideally, you can work with your landlord to clean up any mould and fix the moisture problem. Notify your landlord immediately of any problems, and if needed, provide them with information on mould available from Health Canada or the Canada Mortgage and Housing Corporation (CMHC).

Landlord and tenant issues are regulated by the Residential Tenancy Board, so if you have any questions about landlord and tenant responsibilities please contact the Residential Tenancy Board at 1-800-670-4357 or visit their website.

More Information

• Health Canada - Residential Indoor Air Quality Guideline for Moulds
• Canadian Mortgage and Housing Corporation - Moisture and Air: Householder’s Guide – Problems and Remedies