Indoor Mold And Bacteria and Their Health Effects

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Aspergillus spores

Indoor mold- Aspergillus spores

Indoor mold has become a household name. We have all heard or seen on advertisements phrases like toxic mold or black mold.

These phrases create fear, panic and confusion. People have spent thousands of dollars in indoor mold remediation or disposed of household items including clothes because of mold contamination.

Are these decisions based on facts or fear? It is a difficult question to answer. The objective of this article is to provide some basic facts about indoor mold and bacteria and the associated health effects to help those concerned with indoor mold and bacteria make cost-effective decisions.

Three Things you Should Know About Indoor Mold (also spelt as mould)

Do You Have an Indoor Mold Problem? Don’t Panic! Not Every Mold Is Of Health Concern!

Accurate identification of molds is important. It helps alleviate unnecessary concern and
aids in decision-making. Suitable samples for mold testing include:

  • Pieces of material with signs of mold
  • Tape lift or swab samples taken from surfaces suspected of mold
  • Air samples – This may require professional help to take. If you are not a professional we can help you or direct you to people who can.

The lab report includes health effects (where available) for each mold identified. To send samples, click here to get our Analysis Request Form.

  • Indoor mold and bacteria growth is a fact of life for almost all industrial and indoor environments. However, indoor mold growth can be controlled by providing adequate ventilation and maintaining indoor humidity levels between 30-60%. When excessive moisture or water accumulates indoors, mold growth will often occur, particularly if the moisture problem remains unnoticed or un-addressed for more than 48 hours. The key to mold control is timely maintenance and prompt repairs.
  • Not all molds are harmful but to be safe it is better to treat all molds as potentially harmful. The color of the mold does not determine whether it is harmful or not. Therefore black mold is not necessarily bad mold. Indoor mold related health effects depend on:
    • types of mold present
    • amount of mold one is exposed to and for how long
    • individual health status or sensitivity. Children, elderly and sick people are more vulnerable to mold.
  • It is difficult to eliminate all mold and mold spores in the indoor environment. However, the levels can be minimised by controlling growth. Monitor mold growth by looking for water stains or discoloration on the ceiling, walls, floors, and window sills.

Why Be Concerned About Indoor Mold and Bacteria Growth?

  • Health Risk
    Rye bread with mold growth

    Rye bread with mold growth

    Indoor mold and bacteria pose health risks. As they grow indoors, mold and bacteria produce spores and/or chemical compounds into the air. The health effects associated with these spores (see picture on the right) and chemicals may include runny nose, eye irritation, cough, congestion, aggravation of asthma and respiratory problems, headache, flu-like symptoms, fatigue, and skin rash and other allergic reactions. Individuals with weak immune systems may also get infected by molds as a result of exposure.

  • Legal Issues
    Those responsible for building maintenance or health and safety of building occupants, contractors and other professionals involved in the building operations are at risk of being sued if occupants get sick from indoor mold growth.
  • Material Damage and Impairment of Processes. Mold if allowed to grow, can impair the functioning of many processes from air conditioning units to electrical circuits. Surfaces of materials on which mold is growing get stained or discolored and may disintegrate over time. Wood-rotting molds are capable of weakening wooden structures.
  • Indoor Mold and Bacteria Contamination Can Affect Businesses
    Mold and bacteria growth in the work place can affect the productivity of employees either directly or indirectly. A business affected by microbial contamination problems can soon see its market share fall and incur huge costs in liabilities. For example in food processing plants such as bakeries, bread can develop mold even before it leaves for the market (see a slice of rye bread showing mold growth to the right).

What Should You Do When You Find Indoor Mold?

  • If you are an indoor mold and bacteria consultant
    • Assess the extent of the mold problem
    • Discuss the problem with your client and reassure them
    • Have the dominant molds identified, preferably to species level
      Note: Before sampling, prepare a sampling plan that details how and when samples will be collected, the type of samples to collect, collection requirements for each type of sample, the criteria to use to interpret results, and the benefits expected from sampling, i.e., what question(s) will be answered by the laboratory results and what actions will be taken. Share the sampling plan with the client.
    • Discuss the lab results with the client. If the client is concerned about their health, advise them to seek medical advice from their family doctor
    • Discuss the remediation plan (or options if any), the remediation costs and the expected results with your client
      Note: There are many mold guidelines with invaluable information such as:

  • If you are a Property Manager or Homeowner
    • Don’t panic! The presence of indoor mold does not necessarily mean that you or the building occupants could have adverse health effects, develop mould allergies or have even been exposed.
    • Do not disturb the mold since this could help the mold in shedding more spores into the air.
    • If what you suspect to be mold covers more than 10 square feet, seek the advice of a qualified consultant immediately. If unsure of how to handle mold covering less than 10 square feet, seek professional advice. Avoid exposing yourself or others to mold.
    • Ask for the mold to be identified to reassure yourself or the building occupants that it is not among those that cause serious health effects.
    • Discuss the problem with your family doctor, or, if you are the property manager, reassure the occupants and let them know the actions you are taking.
    • If you find a professional who seems to concentrate more on how the mold could or has affected you or the building occupants, seek a second opinion. A good professional should give facts and not create fear.

You can contact Mold & Bacteria Consulting Laboratories with any questions regarding this article or mold testing services. For free information, email us your questions or fill out our question form and submit for priority attention. Your questions will be answered within 48-72 hours. Complete confidentiality is guaranteed.

For immediate assistance call 905-290-9101.

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Dr Jackson Kung'u
Dr. Jackson Kung’u is a Microbiologist who has specialized in the field of mycology (the study of moulds and yeasts). He is a member of the Mycological Society of America. He graduated from the University of Kent at Canterbury, UK, with a Masters degree in Fungal Technology and a PhD in Microbiology. He has published several research papers in international scientific journals. Jackson has analyzed thousands of mould samples from across Canada. He also regularly teaches a course on how to recognize mould, perform effective sampling and interpret laboratory results. Jackson provides how-to advice on mould and bacteria issues. Get more information about indoor mould and bacteria at
Dr Jackson Kung'u

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