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What Is Deemed Acceptable Indoor Airborne Mold Spore Levels In Ontario?

Question: Is there any government or industry standard as to what is deemed an acceptable indoor airborne mold spore levels in Ontario? The electrical inspector refuses to come on our property even though we have had several air test performed. The qualified tester says we have samples of mold but found them to be acceptable. I was hoping for some clarity on this matter.

Answer: Currently there is no government or industry standard as to what is deemed acceptable indoor airborne mold spore levels. However, it’s generally agreed that mold in indoor environments is a health hazard. However, the higher the airborne mold spore levels in a building the higher the health risk. In 2007 Health Canada published the Residential Indoor Air Quality Guidelines: Moulds.

This is what Health Canada’s Residential Indoor Air Quality Guidelines say about exposure limits:

Health Canada considers that mold growth in residential buildings may pose a health hazard.
Health risks depend on exposure and, for asthma symptoms, on allergic sensitization. However, the
large number of mold species and strains growing in buildings and the large inter-individual variability
in human response to mold exposure preclude the derivation of exposure limits. Therefore, Health Canada recommends:

  • to control humidity and diligently repair any water damage in residences to prevent mold growth; and
  • to clean thoroughly any visible or concealed mold growing in residential buildings.

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

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

So currently there is no acceptable or unacceptable indoor airborne mold Spore levels in Ontario.

Could These Illnesses Be Related To Mold Spores?

Question: My question regards mold spores. Our basement was flooded about 2 weeks ago. Most if not all of the exterior concrete walls and floor were affected as well as an inside wall. Although we have tried to clean everything up as best as we could, we noted a musty smell shortly afterwards. All four family members have been sick with what seems to be various allergic symptoms ever since. Could these illnesses be related to the flood? Could mold spores be the reason and should we have the air quality of our duplex tested?

Answer: It’s possible that your allergic symptoms are linked to dampness in your home. Excessive dampness is a health problem by itself. Indoor dampness also indirectly contributes to health problems by supporting the growth of molds and other microbial agents in addition to initiating the release of chemical emissions from damaged building materials and furnishings. Mold spores are also known to cause allergic reactions in some people.

Research has shown that living in damp homes not only increases the risk of asthma, but also leaves residents with a greater chance of repeated colds and skin allergies. People living in damp houses have been found to require more antibiotics than others and are more likely to suffer from pneumonia, bronchitis or tonsillitis.

You may want to test the air quality in your home to determine the levels of airborne mold spores. I would suggest you hire a professional to assess the situation in your home and give recommendations on remediation.

Testing For Airborne Mold Spore Concentration

Testing for airborne mold spore concentration is achieved by impacting a known volume of air onto a surface coated with sticky material. As the air hits the sticky surface the spores and any other particulates in the air are trapped. In the laboratory the spores are identified under a microscope, categorised into various groups and counted. This method is excellent for estimating how contaminated the air is but it does not tell us what proportion of the counted spores are still viable. If an estimate of the proportion of viable mold spores is needed, then the air has also to be impacted onto some growth agar media. Viable mold spores would then grow on the media and appear as mold colonies, usually referred to as colony forming units (CFU). CFU is not a very accurate way of measuring the viable proportion of airborne mold spores. This is because a single colony can develop from one spore or a group of spores. Secondly, fast growing colonies tend to overgrow slow growing colonies. Also, the agar media used may not support the growth of all categories of viable spores present in the air.

Taking Air Samples For Mold Testing: Settle Plate Method

A number of methods can be used to test air for mold or other microbial contamination. One of the oldest methods of testing air for microbial contamination is the settle plates method. Though the method is semi-quantitative, it is still considered a useful method. In industries such as food, pharmaceutical and cosmetics the method is used to assess the likely number of microorganisms depositing onto the product or surface in a given time. The method involves opening and exposing petri dishes containing agar medium suitable for growth of microorganisms of interest. If one is interested in testing for mold, agar plates containing malt extract agar (MEA) supplemented with some antibiotics to suppress bacterial growth would be used. The agar plates are left open at table-top level at selected points in the room for half-hour to 4 hours. This allows mold spores and fragments to settle onto agar media by gravity. Mold test kits (involving growth media) are settle plates.

Settle Plates Results

The number of microorganisms deposited onto the agar surface of the plate over the period of exposure is determined by incubation of the agar plates at 25ºC for 5- 7 days and counting colonies that develop. The results can be expressed as number of colony forming units (CFUs) per unit time. The counted colonies can then be further characterised to genera or species. Higher numbers of CFUs and/or presence of potential pathogenic or toxigenic molds such Aspergillus fumigatus and Stachybotyrs chartarum are indicators of a problem.

Disadvantages of Settle Plates

Settle plate method is an extremely useful method for assessing air contamination by microorganisms. It is easy to conduct and very cost effective. However, only viable microorganisms would be detected by this method and hence it may give a false impression that the air is “clean” if most of the airborne microorgainisms are dead. False negatives may also be obtained from buildings with:

  • very restricted mold growths.
  • very still air in undisturbed rooms.
  • species of poorly culturable molds (e.g., Stachybotrys chartarum).
  • molds consisting of species with poor airborne dissemination (e.g., Aureobasidium on windowsills, Cladosporium on painted cold air vents, Fusarium and many other wet-spored fungi).

House Mold

House mold is not only unsightly but also a potential health hazard. People with allergies, asthma or other respiratory problems can have serious reactions to house mold spores. Also, molds produce digestive enzymes that help them utilize building materials as food. Therefore, apart from being a health hazard, house mold will also compromise the integrity of the materials it is growing on (see the picture on the right) such as wood, wallpaper, ceiling tiles, carpet, and baseboard.

White house mold growing from a basement ceiling
Photo courtesy of One Day Mold Removal

There are a number of factors that encourage house mold growth. By controlling these factors, we can subsequently control mold growth. The factors include: indoor humidity and moisture content of materials, temperature, air circulation, light, and the chemical composition of building materials. For an existing house we cannot change the chemical composition of building materials. Light and temperature would also not be practically possible to control in that we need light and warm temperatures in our houses. However, we can effectively control house mold by maintaining the levels of relative humidity indoors below 60% and also ensuring proper ventilation. Air circulation helps control moisture levels through evaporation.

What do you do if you see or suspect house mold growth?

If you see or suspect house mold growth do not panic. You may submit mold samples to a qualified mold laboratory to determine whether the mold present is hazardous or only a cosmetic concern. The MOLD TAPE SLIDE™ is a straightforward, inexpensive and effective method to sample visible mold found on any surface. From it you get information and guidance on what to do next. It is an easy way to determine if the mold is toxic and if it will require a professional to conduct more intensive investigation and remediation. Click MOLD TAPE SLIDE™ for details.

Peel off seal from slide to expose adhesive (see the words “Peel Here”)
Place sticky side of slide onto the surface with visible mold growth and press gently.

Place slide back into plastic snap-case.

 

If you can’t see mold growth but can smell “musty” or “earthy” odours you can also perform a preliminary air test (call 905-290-9101 for details) before calling in a professional.

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