People are today more aware of health effects associated with mould than they were 10-15 years ago. When should one be concerned with indoor mould growth? The simple answer is that mould should never be allowed to grow indoors. Apart from being unsightly and a potential health hazard, mould breaks down the materials it is growing on thus reducing their value and structural integrity.

If one happens to find mould growth in their homes or offices, my advice would be not to panic but to seek professional help. There are close to 200 mould species that have been reported from indoor environment and most of these are quite rare indoors. Also, only a few of these would be considered a health risk. The amount of mould growth, the types of mould present, individual health status and for how long one has been exposed to airborne mould (spores and hyphal fragments) are some of the factors that would determine if one is at risk or not. A professional would be able to determine some of these factors and be able to advise occupants if they were possibly at risk of mould exposure.


Should you have a mould problem or question, please call (905)290-9101.

A free online listing of mould testing and remediation companies in Canada is available at http://www.moldbacteria.com/servicelist.html. The listing is intended to help Canadians locate mould testing or remediation services near their area. All companies dealing with indoor mould and bacteria are free to list their services.

The person who asked this question probably wanted to know whether if one smells “earthy” or “musty” odours associated with mold, they would also be inhaling mold spores. The fact is we inhale some mold spores all the time. During summer, for example, we inhale more spores from outdoor air than from indoor air. However, in a building with mold growth problems airborne spores could be excessively high.

Smelling "musty" or "earthy" odours does not necessarily mean one is inhaling high levels of mold spores. While the smell could be due to microbial volatile organic compounds (usually abbreviated as MVOCs), some volatile organic compounds are not of microbial origin. Also, one of the MVOCs responsible for the "earthy" smell is geosmin. This compound is produced by not only molds but also by actinomycetes and other bacteria. Therefore, while the presence of VOCs may be an indication of hidden microbial contamination, they may not be a reliable indicator of microbial contamination or contamination by a specific microorganism.

After analysing air samples for total spore counts, we often get asked whether there are acceptable levels of mould concentrations in air and what effects mould spores have on human health. Unlike many other indoor pollutants, there are currently no set acceptable levels for mould spores. The scientific community including medical doctors is polarized on the effects of mould on human health. However, it is generally accepted that mould can:

• Elicit allergic reactions to sensitized (or atopic) individuals and that not all moulds are allergenic
• Infect humans especially those with weak immune systems
• Produce toxic metabolites (mycotoxins) that can kill or cause other complications if ingested in food.

While scientific evidence to prove that mould is the cause of some illnesses is lacking, there is enough evidence to support the need to remove mould from occupied environments.