Pertubuhan Sains & Kesejahteraan
Science & Wellness Organisation
(PPM-013-05-16022012)
Special Consultative Status with the United Nations Economic and Social Council
Air pollution is commonly understood as an outdoor problem linked to traffic, industry, or haze. However, the World Health Organization (WHO) recognizes that indoor air pollution, including microbial contamination of indoor air, is a major and often overlooked public health concern. Mold is one of the microbial agents that can contaminate indoor air and affect indoor air quality.
​
People spend a substantial portion of their lives indoors, particularly in homes, schools, workplaces, and care facilities. As a result, contaminants released into indoor air can lead to prolonged and repeated exposure. WHO identifies microbial contamination of indoor air, including mold, as an important contributor to poor indoor air quality worldwide.
Why Mold is an Indoor Air Pollution Issue
Image source: Unsplash - Photo by Zoltan Tasi
WHO defines indoor air pollution as contamination of indoor air by chemical, physical, or biological agents that alter its natural characteristics. Mold falls under this definition because it contaminates indoor air through biological emissions.
​
When mold grows indoors, it releases:
​
-
spores
-
microbial cells and fragments
-
metabolites
-
volatile organic compounds
These substances become airborne and can be inhaled. For this reason, WHO treats mold exposure as an air quality issue, not merely a surface or structural problem.
​
WHO emphasizes that mold-related air pollution is closely linked to dampness and excess moisture, rather than cleanliness or housekeeping practices alone.​
How Mold Develops Indoors
Image source: Unsplash - Photo by Jessica
WHO explains that mold growth indoors is closely linked to excess moisture and dampness, which allow microorganisms to grow on indoor materials. While mold can grow on nearly all materials, it develops only when sufficient moisture is present.
​
Common contributing conditions include:
​
-
water leaks or water damage
-
high indoor humidity
-
condensation on cold surfaces
-
inadequate ventilation
-
poor building maintenance
WHO emphasizes that mold growth is not primarily caused by poor cleanliness, but by environmental conditions that allow moisture to persist
Health Effects Associated With Mold Exposure
WHO’s evaluation of scientific evidence shows consistent associations between damp or mold-affected indoor environments and adverse health outcomes.
​
People exposed to indoor mold have increased risks of:
​
-
respiratory symptoms such as coughing and wheezing
-
upper and lower respiratory infections
-
worsening of asthma
-
allergic rhinitis
WHO also reports links to less common but more severe conditions, including hypersensitivity pneumonitis, allergic alveolitis, chronic rhinosinusitis, and allergic fungal sinusitis. These effects have been observed in different populations and climates, and are not limited to individuals with pre-existing allergies or asthma.
No Safe Level of Indoor Mold
WHO concludes that it is not possible to define a safe or acceptable level of mold contamination indoors. Because people are exposed to complex mixtures of microbial agents and responses vary, WHO does not recommend numerical exposure limits.
​
Instead, WHO states that persistent mold growth and conditions that support it should be avoided or minimized, as they increase the risk of adverse health effects.
​
Visible mold, moldy odors, or signs of dampness are therefore considered indicators of increased health risk, rather than cosmetic issues.
Preventing Mold to Protect Indoor Air Quality
According to WHO, mold-related indoor air pollution is largely preventable. Prevention focuses on maintaining indoor environments that do not support microbial growth.
​
Key measures include:
​
-
preventing water intrusion and leaks
-
managing indoor humidity
-
ensuring adequate ventilation
-
maintaining buildings and indoor spaces
WHO assigns responsibility to building owners to provide healthy indoor environments, and to occupants to manage water use and ventilation in ways that do not promote mold growth
Preventing Mold to Protect Indoor Air Quality
Image source: Unsplash - Photo by Howen
According to WHO, mold-related indoor air pollution is largely preventable. Prevention focuses on maintaining indoor environments that do not support microbial growth.
​
Key measures include:
​
-
preventing water intrusion and leaks
-
managing indoor humidity
-
ensuring adequate ventilation
-
maintaining buildings and indoor spaces
WHO assigns responsibility to building owners to provide healthy indoor environments, and to occupants to manage water use and ventilation in ways that do not promote mold growth.
Public Health Relevance
WHO estimates that 10–50% of buildings in many regions are affected by dampness, making mold exposure a widespread issue, particularly in humid climates and poorly maintained housing. Recognizing mold as a form of indoor air pollution highlights its importance as a preventable environmental health risk.
Health Implications of Indoor Mold Exposure
Mold is a form of microbial contamination of indoor air that affects indoor air quality. Indoor air pollution is increasingly recognized by the World Health Organization (WHO) as a significant public health issue. While outdoor air pollution receives greater attention, WHO emphasizes that indoor environments can also contain harmful contaminants, including microbial agents that degrade air quality and affect health.
Because people spend a substantial proportion of their time indoors, in homes, workplaces, schools, and care facilities, exposure to polluted indoor air can be prolonged and repeated. WHO identifies microbial contamination of indoor air, including mold, as an important contributor to adverse health outcomes worldwide.