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Mould News - Axiom Mould Experts

Mould News

Below is a copy of the regulation proposed on December 13, 2006 by the Minister or the Governor in Council under the Canadian Environmental Protection Act, 1999 is published by the Minister in Part I of the Canada Gazette, Canada’s official parliamentary journal.



Proposed residential indoor air quality guideline for moulds

Pursuant to subsection 55(3) of the Canadian Environmental Protection Act, 1999, the Minister of Health hereby gives notice of a proposed residential indoor air quality guideline for moulds. After reviewing the most recent scientific evidence regarding moulds and its effects on health, the Minister recommends to control humidity and diligently repair any water damage in residences to prevent mould growth; and to clean thoroughly any mould growing in residential buildings.

These recommendations apply regardless of the mould species found to be growing in the building.

Any person may, within 60 days after publication of this notice, file with the Minister of Health written comments on the proposed guidelines. All written comments will be made available upon request to all interested parties. All comments, requests for copies of the proposal, and information requests must cite the Canada Gazette, Part I, and the date of publication of this notice and be sent to the Air Health Effects Division, Health Canada, 269 Laurier Avenue W, 3rd Floor, PL 4903C, Ottawa, Ontario K1A 0K9, 613-957-1876 (telephone), 613-954-7612 (fax), air@hc-sc.gc.ca (email).

December 13, 2006
Director General
Safe Environments Programme

On behalf of the Minister of Health



Physical and chemical properties

The word “mould” is a common term referring to fungi that can grow on building materials in homes or other buildings. Mould growth can influence air quality because both spores and mycelial fragments are dispersed into the air and can be inhaled. Their penetration into the bronchial tree depends on their size. The smaller particles penetrate deeper into the lungs.

Three features of mould biochemistry are of special interest in terms of human health:
Mould cell walls contain (1->3)-ß-D-glucan, a compound with inflammatory properties;
Mould spores and mycelial fragments contain allergens; and
The spores of some species contain low molecular weight chemicals that are cytotoxic or have other toxic properties (e.g. satratoxins and atranones produced by Stachybotrys chartarum).

Causes of mould growth

Mould growth in a house requires the presence of nutrients, an adequate temperature, and a sufficient amount of water. The first two requirements being usually met in indoor environments, fungal growth usually results from a moisture problem (CMHC 2003). Major causes of mould growth are:

  • excess humidity resulting in condensation on surfaces;
  • water leakage, e.g. from a broken pipe;
  • infiltration of water from the outside, e.g. from a leaking roof or a cracked basement; and a flood.

Health effects

Health Canada has carried out two reviews of the scientific literature pertaining to the health effects of indoor moulds (Health Canada 1995; 2004). The Institut national de santé publique du Québec also published a review on this subject (d’Halewyn et al. 2003). The following conclusions were drawn:
Exposure to indoor mould is associated with an increased prevalence of asthma-related symptoms such as chronic wheezing, irritative, and non-specific symptoms; and

In laboratory animal studies, instillation of fungal antigens (Penicillium sp. and Aspergillus sp.) and fungal cell components [(1->3)-ß-D-glucan] resulted in an inflammatory response in the lungs of rodents, while instillation of Stachbotrys chartarum spores resulted in severe biochemical and ultrastructural changes.

These conclusions have been supported by more recent findings. In two cohort studies (Wickman et al. 2003; Jaakkola et al. 2005), significant associations were found between home dampness and the risk of developing asthma. In experimental studies, asthma-like responses were observed in mice following exposure to a typical building-associated fungus, Penicillium chrysogenum (Chung et al. 2005), and inflammatory responses were seen in rats exposed to low doses of toxins from the same species (Rand et al. 2005).

Residential Indoor Air Quality Guideline

Health Canada considers that mould growth in residential buildings may pose a health hazard. Health risks depend on exposure and, for asthma symptoms, on allergic sensitization. Therefore, Health Canada recommends

  • to control humidity and diligently repair any water damage in residences to prevent mould growth; and
  • to clean thoroughly any mould growing in residential buildings.
  • These recommendations apply regardless of the mould species found to be growing in the building.

Further, results from tests for the presence of fungi in air cannot be used to assess risks to the health of building occupants.


CHMC 2003. Clean-up Procedures for Mold in Houses. Revised ed. Ottawa: Canada Mortgage and Housing Corporation. ISBN: 0-660-19227-6.

Chung, Y. J., Coates, N. H., Viana, M. E., Copeland, L., Vesper, S. J., Selgrade, M. K., Ward, M. D. W. 2005. Dose-dependent allergic responses to an extract of Penicillium chrysogenum in BALB/c mice. Toxicology 209: 77-89.

d’Halewyn, M. A., Leclerc, J. M., King, N., Bélanger, M., Legris, M. and Frenette, Y., 2002. Les risques à la santé associés à la présence de moisissures en milieu intérieur. Québec : Institut national de santé publique du Québec. 105 p. + appendices.

Health Canada 1995. Fungal Contamination in Public Buildings: a Guide to Recognition and Management. Ottawa: Health Canada.

Health Canada 2004. Fungal Contamination in Public Buildings: Health Effects and Investigation Methods. Ottawa: Health Canada. ISBN 0-662-37432-0. 47 p.Jaakkola, J. J. K., Hwang, B. F., Jaakkola, N. 2005. Home dampness and molds, parental atopy, and asthma in childhood: a six-year population-based cohort study. Environmental Health Perspectives. 113: 357-361.

Rand, T. G., Giles, S., Flemming, J., Miller, J. D., Puniani, E. 2005. Inflammatory and cytotoxic responses in mouse lungs exposed to purified toxins from building isolated Penicillium brevicompactum Dierckx and P. chrysogenum Thom. Toxicological Sciences 87: 213-222.

Wickman, M., Melen, E., Berglind, N., Lennart Nordvall, S., Almqvist, C., Kull, I., Svartengren, M., Pershagen, G. 2003. Strategies for preventing wheezing and asthma in small children. Allergy 58: 742-747.