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revised April 01, 2020

Health Protection

At Home


Moulds are a type of fungus that can be found indoors and outdoors. They usually grow where there is moisture, warmth (2° to 40°C), and a food supply (such as clothing, wood or drywall).

Mould spores and the toxins produced by certain moulds may be harmful to vulnerable people.

How could my family and I be exposed?

Mould spores can be released into the air when mouldy material is damaged or disturbed. You could be exposed to mould if you breathe in mould spores, breathe in the toxins that certain moulds produce, swallow mouldy material or directly handle mouldy material.

People who work in certain occupations may have higher exposures to mould.

Is mould harmful to my health?

Exposure to mould does not always have negative effects. However, the following individuals may be more sensitive to mould:

  • children
  • pregnant women
  • the elderly
  • those with asthma, hay fever or other allergies
  • those with weak immune system due to other medical conditions
  • people with specific illnesses such as diabetes or cancer may be more susceptible to infections caused by certain types of mould

What are the symptoms and health effects?

Most symptoms from mould exposure are not serious or long-lasting. Common symptoms may include:

  • runny nose
  • nasal and throat irritation
  • cough
  • wheezing
  • aggravation of asthma
  • allergic reaction

People with asthma, hay fever or other allergies could experience temporary respiratory symptoms when exposed to low amounts of common moulds.

People with weakened immune systems (e.g., from HIV infection, cancer treatment, kidney failure or diabetes) could develop lung infections when exposed to certain moulds, such as Aspergillus.

I am concerned about the health impacts of mould. What should I do?

If you are experiencing any of the symptoms listed above, you should contact your health care provider.

What should I do if I find mould?

If you find small amounts of mould, (fewer than three visible patches, each patch smaller than 1 metre), you should clean the area and try to prevent the mould from returning. If you have more than three patches or the areas are larger, you need a trained professional to assess your home.

How to address moisture and mould in your home.

To clean mould:

  1. Use personal protective equipment such as safety glasses, gloves and an N95 mask capable of filtering fine particles
  2. Mix detergent with warm water, according to the instructions on the label
  3. Use a sponge or rag to apply the detergent solution to the mouldy surface. Scrub the area
  4. Thoroughly dry the surface by using a dehumidifier or fan
  5. Dispose of used sponges or rags

To prevent mould from growing:

  • Fix any water leaks as quickly as possible
  • If you experience water damage in your home, remove all water-soaked materials (e.g., carpets)
  • Use a dehumidifier or air conditioner during humid months
  • Keep the humidity in your home below 50 per cent
  • Use exhaust fans in washrooms and kitchens when steam is being generated e.g., during or after taking a bath or shower
  • Avoid carpeting in washrooms and basements
  • Add mould inhibitors to paint before applying

If you find mould on porous materials e.g. boxes, ceiling tiles, carpets, they should be discarded.

If you find mould on non-porous materials such as metal, glass, hard plastics, these items can be cleaned and re-used if they are structurally sound.

Mould and school portables

School portables tend to be sources of mould because they are susceptible to water leaks and they often have poor ventilation or humidity control.

Peel Public Health provides advice to the Peel District School Board and the Dufferin-Peel Catholic District School Board on inspecting, cleaning and maintaining portable classrooms. It is the responsibility of each school board to inspect, clean and maintain school buildings and portables for the health and safety of all occupants.

If you have concerns about mould in your child's school, Peel Public Health recommends that you contact the school principal or a member of the School Council. Although the low level of mould exposure at school is unlikely to cause serious health problems, you should take your child to see a doctor if they have nose or eye irritation, coughing, congestion or aggravated asthma.

Resources and links

Information on mould

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Revised: April 01, 2020

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