Serious health problems from toxic mould

By Barb Bayer, Manager of the Limnology and Air Services Division of EnviroTest Laboratories,
Winnipeg, Manitoba

Aspergillus spores

During the past decade, moulds have emerged as an important, and previously overlooked, environmental health hazard. It is now a well-known fact that moulds can and do cause serious health problems in humans. To protect our health and maintain our quality of life, we must ensure that our indoor air quality is generally free of these common and highly mobile contaminants.

Moulds are microscopic organisms that belong to the phylum mycophyta (fungi). They are closely related to mildews, mushrooms and puffballs. Moulds lack chlorophyll and are, therefore, heterotrophic. They often look like black soot, but their colours can vary from green to brown or even pink. They can exist in either a terrestrial or aquatic environment and they survive both indoors and out.

Moulds are one of the fungi responsible for the conversion of complex organic matter into basic nutrients. This conversion is an absolutely critical and beneficial function of moulds. Some moulds aid in the production of food for man and, in the case of specific moulds such as Penicillium, antibiotics are derived.

All moulds require both a source of nutrients and humidity to survive and flourish. Generally, nutrients are not a limiting factor and, when moisture is high, mould will grow on carpets, furniture, dry wall, insulation, ceiling tiles, etc. Sources of moisture that can support growth include leaky roofs, plumbing leaks, sewer back-ups, a build-up of condensation, etc., or just high humidity (e.g. a shower).

Virtually all moulds produce spores that are easily dispersed in the environment. A single spore can establish a colony of moulds and this colony can produce millions of spores. It is only when a large number of mould spores are produced and bioaccumulate that a health problem typically occurs.

In general, it is the very young, the elderly, and immune-compromised individuals who are most at risk. It is also important to note that sensitivity to mould varies dramatically from individual to individual. The mould concentration that causes a severe reaction by one person may be readily tolerated by another.

Mould can often be hidden from view and cannot be seen or smelt. As a consequence, individuals may experience health effects without ever knowing the cause. It is imperative that investigators diligently search for mould in walls, in attics and crawl spaces or anywhere a damp environment may exist.

Mould exposure from homes or workplaces can cause a variety of symptoms ranging from minor allergic reactions to extremely severe, life threatening disease. Documented health effects from mould exposure include headache, fatigue, cough, shortness of breath, congestion, fever, nausea, and eye, ear and throat irritation.

Mould on air strip	Stachybotrys atra

Certain moulds can be extremely toxic. The most toxigenic include Stachybotrys, Aspergillus and Penicillium. These moulds have been responsible for the closure ofschools, day care centres, hospitals and numerous buildings in both Canada and the United States. Due to their toxicity, even small numbers of these moulds require thorough investigation and remediation.

Because of the vast number of moulds in the environment, and the large potential health risk, it is critical to confirm and identify the type of mould present. The use of an accredited laboratory for this purpose helps to ensure that a proper course of corrective action is followed based on the moulds identified. Accreditation agencies include the Standards Council of Canada (SCC) and the American Industrial Hygiene Association (AIHA).

Analysis can be performed on bulk samples, swabs and/or air samples for viable or living moulds. Air-O-Cell cassettes and tape samples can be analyzed for non viable or dead organisms. Health Canada has published guidelines to assist with the interpretation of mould analyses and individual provinces such as Manitoba have recently developed their own provincial Mould Guidelines.

There is no doubt that concern over exposure to moulds in our homes, in our schools and in our workplace will broaden as our understanding of the short-term and long-term health risks increases.

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