Health & Safety

Information Bulletins · The Fungus Among Us



The Fungus Among Us

Moulds are found everywhere, both indoors and outdoors, particularly in decomposing leaves and wood. Due to several years of inadequate funding, our schools have seen little preventative maintenance and now have many water sources which allow for mould growth: roof leaks, plumbing leaks, condensation from uninsulated pipes, flooding and high humidity levels.

Moulds also need a cellulose source of nutrients so they can be found on paper and paper products, cardboard, ceiling tiles, wall panels, wood, insulation, carpet, fabrics, foods, and indoor plant life. Although fungi need water to grow, they release their spores and bioaerosols when conditions are dry and unfavourable for life.

The most common indoor moulds are Cladosporium, Penicillium, AspergillusAlternaria Stachybotrys, which many refer to as "black mould" is less common. The American Industrial Hygiene Association (AIHA) lists Stachybotrys chartarum, Aspergillus flavus/parasiticus, Aspergillus fumigatus, Aspergillus versicolor and Fusarium monoliforme as requiring "Urgent Risk Management". Several moulds are classified as Risk Group 2 Pathogens by Health Canada and are infectious substances under the Transport of Dangerous Goods (TDG) Regulations which has a significant impact for transport and disposal.

Health Effects

Until the early 90s, moulds were considered a mild health hazard for most people. Only those people with allergies or asthma were seriously concerned with moulds which cause hay fever-like allergic symptoms: nasal stuffiness, eye irritation, wheezing, or skin irritation. Symptoms can disappear when exposure stops.

Often times only a small number of staff members will complain of these symptoms and since they have other health problems, their concerns are often ignored. Yet these individuals could be like the "canary in the coal mine" or "indicator species" so it is important to investigate all complaints.

Absorption of fungal spores through the skin, particularly in immuno-suppressed individuals, can cause mild symptoms, opportunistic infections, dermatitis and even intermittent local hair loss.
Indoor air quality studies indicate that volatile organic compounds (VOCs) are produced by moulds in the form of metabolic gases and could contribute to "sick building syndrome."

Recent research has shown that some of these fungi also produce mycotoxins, a natural but toxic chemical linked with cancer and heart disease. Inhalation of the spores containing the mycotoxins can produce cold and flu symptoms, sore throats, diarrhea, headaches, fatigue, general malaise and difficulty concentrating. Effects of absorption of the toxins in the lungs are called pneumomycosis.

Stachybotrys can produce a poisonous mycotoxin which will suppress the immune system affecting the lymphatic system and bone marrow. It has been reported to be a liver and kidney carcinogen. There have also been unproven links to unique or rare health conditions such as pulmonary hemorrhage or memory loss.

What should be done?


If you suspect this mould exists in your workplace, immediately inform both your supervisor and your OSSTF Health & Safety Officer.

Visit a doctor about your symptoms, preferably a specialist, an allergist or a respirologist. If an Occupational Health Clinic for Ontario Workers (OHCOW) is located in your community, they have experience in making the link between the symptoms and the workplace, which would be necessary for a WSIB claim or if you need to prove there is a problem to your employer.

Your employer should be encouraged to maintain open lines of communication since public relations will become more difficult if occupants perceive they are not being fully informed.

Evacuation is rare, but if necessary, the local health unit and the Medical Officer of Health would become involved.


Large mould problems can usually be seen or smelled. Do NOT go looking for mould which could damage or disturb it. If it is necessary to look inside of walls a portable boroscope can be used.

Testing for the presence of mould is not recommended since it is difficult and expensive. Any mould growth or potential source of mould growth found indoors should be remediated regardless of what type of mould is present.

Testing is not reliable in determining health risk, yet some employers insist on testing to "prove" there is a problem. Stachybotrys spores are in a gelatinous mass and are rarely airborne unless physically disturbed so there can be false negative tests. "Bulk samples" or "smear/swipe" samples of a visible mould source would be taken for microscopic examination. If air sampling is done, mould is measured in CFU (colony forming units)/m3. Any level of mould growth higher indoors than outdoors is a cause for a concern. Health Canada has guidelines of acceptable levels, some of which are species specific.

Indoor Air Quality in Office Buildings: A Technical Guide, Health Canada, 1993 (Pages 48–49)

"- More than 50 CFU/m3 of a single species (other than Cladosporium or Alternaria) may be reason for concern present. Further investigation is necessary.

- Up to 150 CFU/m3 is acceptable if there is a mixture of species reflective of the outdoor air spores. Higher counts suggest dirty or low efficiency air filters or other problems.

- Up to 500 CFU/m3 is acceptable in summer if the species present are primarily Cladosporium or other tree and leaf fungi. Values higher than this may indicate failure of the filters or contamination in the building."


Disinfection with a mild bleach solution destroys only surface mould. After disinfection, removal of any porous infected materials is the best action and should be done with the prescribed precautions and procedures similar to asbestos removal. The larger the area, the more precautions necessary.

No inspection, disinfection or removal should be done in occupied buildings. Disinfection and/or removal should only be done by persons trained in the handling and removal of hazardous materials, using proper personal protective equipment with respirators if necessary.


Every Joint Health and Safety Committee should be involved in designing and implementing their board’s inspection program, with particular attention to portables and basements. Monitoring devices such as moisture meters can be used to determine moisture content of drywall.

All water sources/leaks must be fixed and adequate ventilation provided to keep humidity levels low enough to prevent future mould growth. Any porous materials which were wet for more than 24 hours must be removed. Additional precautions are necessary if the water may have also contained sewage.

Many facilities are now avoiding the use of carpeting and fabric draperies. Dispose of any old, unused books and paper products. Most importantly, ask to see preventative maintenance records for ventilation units, plumbing fixtures, etc. since preventative maintenance is the key to avoiding mould growth.