Fungal Toxins

Fungal toxins, or mycotoxins, are biomolucules produced by fungi which can be toxic to animals and humans. Many fungal toxins interfere with RNA synthesis and can damage DNA. Aspergillus Flavus and Aspergillus parasiticus are strong carcinogens. Trichothecenes produced by Stachybotrys chartarium and Asperigullus versicolor were present in most samples of tested material and dust from buildings with current or past water damage. Of fifteen samples, nine of these came from buildings without visible damage or mould.

Aspergillus mold culture.



(Photo available through Environmental Health Perspectives)


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Fungal Allergens

Fungal species produce Type I allergens. Common indoor/outdoor species such as Alternaria, Pen icillian, Aspgillus, and Cladosporium cause allergic repertory disease, especially asthma.  Pencillian and Aspgillus are also well-known causes of Type III allergens. And in high concentrations, Type IV allergens, hypersensitivity pneumonitius,  are seen.  Inside airways, germination and mycelia growth occur most which release greater amounts of spores, hyphae, and fungal fragments. Because these are well adapt at airborne dispersal, these are the most harmful fungal issues.

More Information available at World Health Organization.

Guidelines from World Health Organization

Review from Executive Summary of The World Health Organization’s publication, The Guidelines for Indoor Air Quality: Dampness and Mould:

On the basis of this review, the following guidelines were formulated. Persistent dampness and microbial growth on interior surfaces and in building structures should be avoided or minimized, as they may lead to adverse health effects.

  • Indicators of dampness and microbial growth include the presence of condensation on surfaces or in structures, visible mould, perceived mouldy odour and a history of water damage, leakage or penetration. Thorough inspection and, if necessary, appropriate measurements can be used to confirm indoor moisture and microbial growth.
  • As the relations between dampness, microbial exposure and health effects cannot be quantified precisely, no quantitative health-based guideline values or thresholds can be recommended for acceptable levels of contamination with microorganisms. Instead, it is recommended that dampness and mould-related problems be prevented. When they occur, they should be remediated because they increase the risk of hazardous exposure to microbes and chemicals.
  • Well-designed, well-constructed, well-maintained building envelopes are critical to the prevention and control of excess moisture and microbial growth, as they prevent thermal bridges and the entry of liquid or vapour-phase water.
  • Management of moisture requires proper control of temperatures and ventilation to avoid excess humidity, condensation on surfaces and excess moisture in materials. Ventilation should be distributed effectively throughout spaces, and stagnant air zones should be avoided.
  • Building owners are responsible for providing a healthy workplace or living environment free of excess moisture and mould, by ensuring proper building construction and maintenance. The occupants are responsible for managing the use of water, heating, ventilation and appliances in a manner that does not lead to dampness and mould growth. Local recommendations for different climatic regions should be updated to control dampness-mediated microbial growth in buildings and to ensure desirable indoor air quality.
  • Dampness and mould may be particularly prevalent in poorly maintained housing for low-income people. Remediation of the conditions that lead to adverse exposure should be given priority to prevent an additional contribution to poor health in populations who are already living with an increased burden of disease.

Schild – Vereinte Nationen-Campus (UN-Campus) Görresstr. 15 in Bonn. United Nations Educational Scientific and Cultural Organization (UNESCO-UNEVOC), World Health Organization (WHO-ECEH), United Nations University (UNU-EHS). (Photo by Michael Z.)

Full publication available at World Health Organization.

Health Risk Summary from World Health Organization

Review from Executive Summary of The World Health Organization’s publication, The Guidelines for Indoor Air Quality: Dampness and Mould:

The conditions that contribute to the health risk were summarized as follows.

  • The prevalence of indoor dampness varies widely within and among countries, continents and climate zones. It is estimated to affect 10–50% of indoor environments in Europe, North America, Australia, India and Japan. In certain settings, such as river valleys and coastal areas, the conditions of dampness are substantially more severe than the national averages for such conditions.
  • The amount of water on or in materials is the most important trigger of the growth of microorganisms, including fungi, actinomycetes and other bacteria.
  • Microorganisms are ubiquitous. Microbes propagate rapidly wherever water is available. The dust and dirt normally present in most indoor spaces provide sufficient nutrients to support extensive microbial growth. While mould can grow on all materials, selection of appropriate materials can prevent dirt accumulation, moisture penetration and mould growth.
  • Microbial growth may result in greater numbers of spores, cell fragments, allergens, mycotoxins, endotoxins, β-glucans and volatile organic compounds in indoor air. The causative agents of adverse health effects have not been identified conclusively, but an excess level of any of these agents in the indoor environment is a potential health hazard.
  • Microbial interactions and moisture-related physical and chemical emissions from building materials may also play a role in dampness-related health effects.
  • Building standards and regulations with regard to comfort and health do not sufficiently emphasize requirements for preventing and controlling excess moisture and dampness.
  • Apart from its entry during occasional events (such as water leaks, heavy rain and flooding), most moisture enters a building in incoming air, including that infiltrating through the building envelope or that resulting from the occupants’ activities.
  • Allowing surfaces to become cooler than the surrounding air may result in unwanted condensation. Thermal bridges (such as metal window frames), inadequate insulation and unplanned air pathways, or cold water plumbing and cool parts of air-conditioning units can result in surface temperatures below the dew point of the air and in dampness.

More Information available at World Health Organization.

Executive Summary of The World Health Organization

Review from Executive Summary of The  World Health Organization’s publication, The Guidelines for Indoor Air Quality: Dampness and Mould:

  • Sufficient epidemiological evidence is available from studies conducted in different countries and under different climatic conditions to show that the occupants of damp or mouldy buildings, both houses and public buildings, are at increased risk of respiratory symptoms, respiratory infections and exacerbation of asthma. Some evidence suggests increased risks of allergic rhinitis and asthma. Although few intervention studies were available, their results show that remediation of dampness can reduce adverse health outcomes.
  • There is clinical evidence that exposure to mould and other dampness-related microbial agents increases the risks of rare conditions, such as hypersensitivity pneumonitis, allergic alveolitis, chronic rhinosinusitis and allergic fungal sinusitis.
  • Toxicological evidence obtained in vivo and in vitro supports these findings, showing the occurrence of diverse inflammatory and toxic responses after exposure to microorganisms isolated from damp buildings, including their spores, metabolites and components.
  • While groups such as atopic and allergic people are particularly susceptible to biological and chemical agents in damp indoor environments, adverse health effects have also been found in nonatopic populations.
  • The increasing prevalences of asthma and allergies in many countries increase the number of people susceptible to the effects of dampness and mould in buildings.

More Information available at World Health Organization.

Indoor Dampness Levels and Fungal Allegens and Toxins

Indoor dampness levels were recorded at a level of 10-50%, prevalent in office buildings, day cares, and schools. High humidity, condensation, and water damage, either past or present, promote the survival and growth of fungi which result in higher exposure to fungal allegens, toxins, and irritants. These damp environments also cause bacteria endotoxins. The damp materials also increase their chemical degradation resulting in more emissions of volatile organic compounds, such as formaldehyde.

More Information available at World Health Organization.

The European World Health Organization

In October, 2007, European specialists met in Bonn in order to discuss the problem of microbial pollution. Indoor pollution is caused by hundreds of species of bacteria and fungi, but most particularly filamentous fungi—mould. The Guidelines for Indoor Air Quality: Dampness and Mould discusses the most recent scientific evidence on health problems caused from mould which concludes that exposure to indoor pollution causes increased respiratory problems, allergies, and asthma, as well as agitation of the immunity system. This document also discusses common conditions in which mould thrives  and ways to control it. The best way to avoid health issues due to microbial pollution is to prevent excessive moisture from accumulating visible or within walls and foundations.

European Health Minister at 60th regional meeting in Moscow (September, 2010)

More Information available at World Health Organization.