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Indoor Air Quality: 7 Basic Questions about Moulds

By Kurina Baksh
Published: October 27, 2016 | Last updated: January 10, 2017 01:55:17
Key Takeaways

Moulds can have an adverse effect on human health. Consult the answers to these seven questions to learn how to identify and eliminate mould in your home or workplace.

Source: Dtje/

The American Society for Microbiology estimates that 90 percent of Americans spend most of their time indoor, where the concentration of biological contaminants in the air are much higher compared to outdoor air.

Additionally, research has indicated that hundreds of species of bacteria and fungi grow indoors when sufficient moisture is available, making microbial pollution a key element of indoor air pollution.

Furthermore, exposures to high levels of indoor moisture have been associated with upper respiratory symptoms, such as asthma, coughing, and wheezing. Therefore, although it may be invisible and largely unnoticeable, the United States Environmental Protection Agency (EPA) has ranked poor indoor air quality (IAQ) as one of the top environmental risks to public health.


What are Biological Contaminants?

Biological contaminants are either living things or produced by living things. This may include bacteria, fungi (moulds), viruses, pollen, and dust. Moulds are considered the number one biological contaminant affecting indoor air quality. Moulds are a type of fungus that reproduces by releasing tiny spores into the air (to read more about indoor air quality, check out Indoor Air Quality: The Invisible Hazard in Every Workplace).

What Causes Moulds to Grow?

High levels of air moisture or humidity indoors are optimum conditions for moulds to grow. For instance, differences between inside and outside temperatures can cause water to condense on windows, which can result in the growth of mould. Additionally, toxic moulds can grow on building materials that have accumulated moisture such as wood, leaking pipes, upholstery, ceiling tiles and carpet.

What are the Most Common Types of Moulds Affecting IAQ?

Some of the most common types of mould found in buildings include:

  • Stachybotrys chartarum
  • Aspergillus sp.
  • Penicillium sp.
  • Fusarium sp.
  • Trichoderma sp.
  • Memnoniella sp.
  • Cladosporum sp.
  • Alternaria sp.

What are the Health Concerns Associated with Moulds?

The inhalation of mould spores can exacerbate existing health problems, as well as create new ones. Moulds produce mycotoxins, which are metabolities or by-products from moulds. Mycotoxins have been identified as being toxic to humans, slowly wearing down the immune system, which can result in respiratory problems or allergies. The most common symptoms include:

  • Headaches
  • Difficulty concentrating
  • Fatigue
  • Cough or congestion
  • Eye, nose and throat irritation
  • Aggravation of asthma

Additionally, moulds can make the following symptoms of allergies worse:

  • Chest tightness
  • Wheezing
  • Shortness of breath
  • Eye irritation
  • Nasal congestion

How Can We Detect Moulds in the Home or at the Office?

Moulds are capable of growing on any surface once moisture is present. However, different levels of moisture are needed for the growth of different moulds. The most reliable method to identify the presence of moulds is to conduct a thorough visual inspection of the indoor environment. Here are some tips to follow when visually inspecting for mould:

  • Look for signs of water damage, such as discolouration or staining
  • Look for signs of moulds, such as dark spots or patches
  • Check the following areas for signs of water damage or the presence of moulds: ceiling tiles; walls, including wallpaper and drywall; floors; window sills; carpets; furniture; and insulation
  • Check for puddles of water around sinks, tubs, air conditioners, refrigerators, and humidifiers

Additionally, surface sampling can be conducted by a trained professional to detect the presence of moulds in the home or at the office. Surface sampling involves scrapping suspected spots for laboratory evaluation.

Once Detected, How Can Moulds be Removed or Cleaned?


For small areas (less than one metre square), the moulds can be cleaned using detergent and water. Please sure to wear the appropriate personal protective equipment (PPE), such as gloves and mask, when cleaning moulds. For larger areas, enlist the help of commercial cleaners.

Additionally, all water-damaged carpet should be cleaned within 24 hours. If this is not possible, consider throwing them away. Contaminated building materials, such as mould-infected ceiling tiles or mildew dry wall should be disposed of immediately.

How Can the Presence of Moulds in IAQ be Controlled?

Due to the fact that moulds can grow anywhere once moisture is present, the best method of prevention is to reduce the amount of moisture. This can be done by:

  • Determining the source of the moisture then eliminating it
  • Keeping the relative humidity of the indoor environment per 30 to 50 percent; humidity can be controlled with air-conditioners or humidifiers
  • Installing exhaust fans vented to the outside in areas such as the bathroom and kitchen
  • Insulating cold surfaces to prevent condensation on pipes, windows, walls, roofs, and floors
  • Keeping the building and the heating, ventilation, and air conditioning (HVAC) systems in good working order
  • Cleaning up any floods or spills immediately (within 24 to 48 hours)
  • Repairing all internal and external water leaks immediately
  • Keeping stagnant water sources clean and disinfected

Research Needs and Issues

All moulds are capable of adversely affecting human health. Reducing and preventing mould exposure is, therefore, crucial in decreasing the risk of damage to human health. Unfortunately, due to the vast types of mould species present, as well as individuals’ sensitivities, setting a specific exposure limit for moulds is nearly impossible. While data exist regarding moulds that can be ingested, there is none for moulds that can be inhaled. This may be attributed to the fact that biomarkers (chemicals in the body that measure if an individual has been exposed to a disease-causing organism) specific to mould are absent.

Each home or work environment has unique contributors to air quality. For workers, poor indoor air quality can put their well-being at risk. For employers, this means poor quality of work and low productivity. Hence, maintaining good indoor air quality, as it relates to the presence of moulds, can help everyone to breathe easier.


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Written by Kurina Baksh

Kurina Baksh is a Health, Safety and Environment Professional from Trinidad and Tobago. As a recent graduate in the field, she is trained to analyze and advise on a wide range of issues related to her area of expertise. Currently, she is an independent consultant who develops public outreach and education programmes for an international clientele. She strongly believes that increasing public outreach and education can promote hazard awareness and ultimately save lives.

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