What are Moulds?

Moulds are microorganisms that can grow on virtually any substance, indoor and outdoor, if moisture, oxygen, and an organic source are present. Some moulds and yeast cause disease or food spoilage; others play a key role, for example, in nature where it is responsible for the breakdown of organic matter, like fallen leaves, plants and dead animals. Mould that is actively growing usually appears woolly or slimy. It can show in a range of colours such as: white, brown, black, green, blue and red. In our workplaces, moulds can be a significant health hazard. 

There are over 1.5 million species of mould in the world. However, only about 100,000 have been identified, and about 1,000 species can be found in Canada. 

How do moulds affect the health of workers?

Moulds produce thousands of tiny particles called spores as part of their reproductive cycle. When disturbed by air movement or contact, moulds release these spores into the air. The inhalation of spores, moulds or mould fragments can affect your health or make certain health conditions worse. 

Lack of moisture causes moulds to become dormant. Dormant moulds still have the capacity to spread spores and fragments into the air and can become active again when moisture returns. 

Some moulds create and release mycotoxins, which slowly wear down the immune system and can lead to allergic or respiratory problems. 

Potential exposure to toxic spores is a particular risk to those working in an environment that has been affected by water damage, or where still water may be present.  

Workers exposed to mould can have different symptoms. Some may have no reaction at all. The most common effects of mould exposure are: 

  • Irritation to the skin, eyes, nose, throat
  • Burning in the nose, nosebleeds 
  • Difficulty breathing, asthmatic attacks 
  • Cough or congestion 
  • Watery eyes, runny nose  
  • Headache 
  • Fatigue, difficulty concentrating 
  • Impairment of the immune system 

In some cases, lung and liver cancer can result from long-term exposure to aflatoxin, a toxic compound produced by certain moulds. 

Individuals with weakened immune systems are particularly susceptible to mould-related illness and should avoid being exposed to it whenever possible. 

How are mould hazards identified?

A combination of methods can be used in the detection and identification of mould hazards. A moulds hazard survey can be done in cooperation with the employer, in which case the union should approve the survey and be involved in collecting and assessing the information generated. If the employer resists the idea or denies the existence of mould, the union should conduct its own hazard survey. 

Visual inspections are the most reliable method of identifying mould problems. When conducting a visual inspection, look for signs of water damage such as discolouration and staining. Be sure to look at carpeting and floor coverings, fabric on and underneath furniture, ceiling tiles and drywall, behind furniture, and areas where there is standing water like sinks, kitchens, air conditioners, etc. 

Moulds can appear as dark spots or patches of any colour. They can have a variety of textures from woolly to slimy. They thrive in dark, moist environments, so they may be hidden from view. Dormant moulds often have a dry, powdery or crusty appearance. 

Air sampling, surface sampling and bulk sampling (taking bits of drywall, flooring, etc.) are also methods used to identify the presence of moulds. The person taking the samples must be properly trained to do so and wear appropriate personal protective equipment

How to prevent moulds from forming in your workplace

It is your employer’s responsibility to provide you with a healthy and safe workplace. 

Mould hazards often arise as a result of cutbacks or employer neglect. The sustained and/or extensive growth of any visible mould on the interior surfaces of a building is unacceptable. 

The following can help prevent mould growth in your workplace: 

  • Keep relative humidity in the workplace between 30 and 60 per cent  
  • Monitoring devices can be used to measure the moisture level in wood, carpets, drywall, etc. This can help indicate whether the material’s condition can promote the growth of mould. 
  • Conduct regular inspections and be diligent, particularly if you work in a sewage treatment plant or composting facility. 
  • Make sure landscaping and eavestrough downspouts direct water away from buildings. 
  • Ensure any high moisture areas are properly ventilated with local exhaust ventilation that captures the moisture and directs it out of the building. 
  • Get employers to insulate cold surfaces to prevent condensation on pipes, windows, walls, roofs and floors. 
  • Perform regular maintenance and cleaning of heating, ventilation and air conditioning systems. 
  • Perform regular maintenance of buildings, especially roofs, basements, and other locations where leaks occur. 
  • Maintain proper staffing to conduct maintenance procedures, such as fixing and maintaining plumbing systems and fixing building leaks to prevent mould growth and other workplace hazards. 

The Occupational Health and Safety Act places a responsibility on constructors, employers, and supervisors to take all reasonable precautions to protect the health and safety of employees. This includes protecting workers from the health risks of mould in workplace buildings 

CUPE recommends that members negotiate contract language for specific controls, monitoring, or access to information about moulds. 

What should you do if there is mould in your workplace?

If mould is discovered in your workplace, it should be reported to management immediately. If the problem is not immediately rectified, report it to your health and safety committee, so that they can assist until the problem is fixed. 

Fixing a mould problem includes identification and correction of the condition that allows the mould to grow, and safe removal of materials damaged by mould. Appropriate personal protective equipment should be used during remediation. The cleaning and removal process depends on the size and type of mould growth, the extent of the damage, and the location. 

Trained professionals should carry out mould remediation. In workplaces where staff are expected to participate in mould removal, workers must be properly trained in mould remediation and the hazards associated with working around mould. Staff should be provided with appropriate personal protective equipment.  

If your employer refuses to deal with mould, you may need to initiate a work refusal to protect your own health. Find out about your right to refuse at cupe.ca/health-and-safety/righttorefuse 

For more information about other health and safety concerns related to air quality, including a sample workplace health survey, please refer to the CUPE Indoor Air Quality Guideline, or contact: 

CUPE National Health and Safety Branch
1375 St-Laurent Boulevard

Tel: (613) 237-1590
Fax: (613) 237-5508
Email: health_safety@cupe.ca

Fact Sheet: Moulds