As mould grows, it releases airborne spores and fragments of hyphe (filaments) that can affect a worker's health. People with allergies, asthma, or a weak immune system are most at risk. Mould grows quickly on almost any damp material.

How workers are exposed

Moulds are everywhere. All they need to grow is water and a source of food, such as cardboard or wood. As mould grows it releases spores. Workers could inhale the airborne spores and hyphae (filaments).

Mould thrives where there is prolonged dampness. Bathrooms, basements, ceilings, and water-damaged walls are all potential hosts for mould.

The risks

For most people, exposure to mould doesn't cause any significant health effects. However, if a worker has a weakened immune system, the health effects can be severe. Mould can cause allergic reactions, asthma, pneumonitis, infections of the upper airway, sinusitis, or other lung infections.

How to reduce the risks

Prevention is the key to avoiding mould exposure. Always make sure that water leaks on the job site are fixed and standing water is mopped up.

If a worker complains about indoor air quality, the employer must investigate. If significant mould contamination is found, appropriate measures must be taken to remove it. A trained abatement team is usually needed to safely remove the mould. Once the site is cleaned, locate the source of the water to prevent mould from growing again.

The best way to reduce the risk of exposure to mould is to eliminate the source of exposure and control water leakage and moisture. When choosing controls, start by asking the questions in the following steps, which are listed in order of effectiveness.

  1. 1

    Elimination or substitution

    Eliminating the hazard by substituting a safer process or material, where possible, is the most effective control. A question to consider:

    • Can you use building materials that are resistant to mould growth in areas where water leaks may occur (e.g., in kitchens and bathrooms)?
  2. 2

    Engineering controls

    Making physical modifications to facilities, equipment, and processes can reduce exposure. Some questions to consider:

    • Can mouldy materials be encapsulated or enclosed in the short term?
    • How can mould removal work areas be enclosed and the air filtered to prevent the escape of spores and hyphae?
    • How will worker exposure to moulds be monitored?
  3. 3

    Administrative controls

    These involve changing work practices and work policies. Providing awareness tools and training also count as administrative controls. All can limit the risk of exposure to mould. Some questions to consider:

    • Have you developed a written exposure control plan for mould?
    • How can signs be posted to give unprotected workers effective warning when mould is being removed?
    • Where can written safe work procedures be posted?
    • How will you train workers regarding the hazards of mould exposure and how to protect themselves?
  4. 4

    Personal protective equipment

    This is the least effective control. It must always be used in addition to at least one other control. Some questions to consider:

    • Do workers have the proper respirators, eye wear, and protective clothing for use during mould cleanup?
    • Have respirators been checked and fit tested to make sure they will work properly?