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Topics: Indoor Air

Mould is a ubiquitous fungus in outdoor environments that inevitably makes its way indoors. The general population is commonly exposed to mould through inhalation, and less commonly through direct contact, with no adverse effects. However, individuals with asthma or other underlying respiratory ailments may show sensitivity to mould or its cellular components that may trigger respiratory tract irritations (coughing, shortness of breath) or exacerbate existing respiratory symptoms. If an indoor condition such as excess moisture results in mould growth, elevated concentrations in the indoor environment can increase the risk of exposure to mould. Mould growth in an indoor environment is a supporting indicator of deteriorating building integrity and indoor air quality.

The assessment of mould exposure is complicated, requiring investigations that include qualitative observations and, when the presence of mould is uncertain but suspected, quantitative measurements. With varying responsibility and policies across Canada, public health inspectors and other environmental health professionals may respond to public inquiries about mould in indoor environments by providing information, conducting walk-through investigations, and/or reviewing microbial laboratory reports from surface or air sampling. Evidence of mould growth in an indoor environment generally prompts action to remove the mould and remediate the conditions that promote its growth. Complex cases may require the involvement of professionals with specific knowledge, training, and experience in mould assessment and remediation.

Evidence reviews:


  • BCCDC Environmental Health Seminar – A Microbial Investigation Toolkit for Environmental Health Practitioners - available upon request
  • Indoor Air Quality Workshop – Mould

Additional resources:

  • Canada Mortgage and Housing Corporation - Mould in Housing
    • This series developed in partnership between CMHC and Health Canada provides First Nation communities with basic information on mould in the home, how to identify it, clean small areas and prevent future growth.

This list is not intended to be exhaustive. Omission of a resource does not preclude it from having value.

Last updatedFeb 12, 2015