Understanding Mould

You can find a lot of information on mould online, but trying to understand it may be difficult to those who didn’t take biology and chemistry. Even after stumbling through the pronunciation of these words, not everyone can comprehend what was meant by the statement: “Satratoxin, a low-molecular weight non-volatile organically derived agent, belongs to the macrocyclic trichothecene class of mycotoxins generated from fungal microorganisms.” 

This blog attempts to explain mould in a less scientific manner. It will focus on those types of mould that have been considered as problematic to the “indoor mould issue” therefore does not address other fungal organisms which may behave differently. Analogies presented are not intended to be scientifically accurate, but rather to illustrate complex behaviours in more simple terms.

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Most people will associate mould with allergies and these reactions are certainly prevalent with most all species found indoors. In addition to causing an allergic response, mould can be irritating, infectious and even toxic to humans. Understanding the general behaviour of mould provides insight into the adverse components produced by mould.

The Organism 
Fungi can be considered nature’s garbage disposal. Without them, there would be mountains of leaves, dead trees, and other organic materials sitting so they are very important to our eco system. 

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Mould spores are floating around in the air continually, when they land on a food source, they sit there patiently waiting for water. If the item they land on should contain sufficient moisture, or water comes from another source (leaks, etc.), the spore germinates and hyphae grows. The hyphae branch out, secrete enzymes to breakdown the food, form the mycelium, and absorb nutrients to grow. As long as the food and water hold out, colonies will continue to grow. Note that individual hyphae and spores are very, very small and few can see them without a microscope. When you see visible mould, you are generally seeing that mass of mycelium.

Mould spores can intertwine into fabrics and wall substrate which they will penetrate. As it consumes the substrate, it can also create it’s own route by dissolving pathways into the material. This is one of the reasons it is so difficult to kill and/or clean up mould on organic substrates by traditional cleaning methods. If you remove the surface growth, those bits of hyphae within the substrate are ready for re-growth upon the return of moisture.

As the organism matures, it develops spores intended for reproduction. Spores vary in size, shape, weight and methods of distribution. Some are light and buoyant so they float easily through the air. Others are wet and sticky allowing them to cling to insects, rodents, etc. as a mode of travel.

Volatile Organic Compounds
As mould consumes it’s food source, the chemical reactions of enzymes, substrates and mould growth produce carbon dioxide, water, and volatile organic compounds (VOC). Because these items are a result of actions essential to the growth of the organism, they are classified as primary metabolites. 

For mould, many types of VOC are produced and typically include aldehydes, alcohols, and hydrocarbons. They have complex structures and names like “2-methyl-1-propanol”, so if you are going to dig deeper into VOC, get ready for chemistry class.

They are called volatile in that they evaporate easily at room temperature and pressure. 

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When you smell a musty-mouldy odour, it’s generally the VOC you are noticing. VOC are often considered irritants to mucus membranes, however, are also capable of both short-term and long-term adverse health effects. If you do smell these odours, it’s a sure sign the mould is consuming and growing and you need to take action. (Note that VOC may also be derived from non-mould sources including natural materials used in cleaning agents.)

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Toxins
Mould is capable of producing compounds called mycotoxins which are toxic to other organisms, including people. Mycologists believe these toxins are produced as protection against competing organisms and therefore, humans are simply caught in the cross-fire of this fight for survival.

 

Some of these toxic substances are considered extremely hazardous to people.  Lab and field studies have shown these compounds to produce severe toxic effects in both animals and humans and therefore, the general recommendation is to minimise exposure to potentially toxigenic mould. Symptoms from toxic exposure range from flu-like symptoms, skin rashes and lesions, bleeding, fatigue, difficulty breathing, depression, etc. to longer-term nerve and organ problems, altered immunity, and cancer.

Not all secondary metabolites are considered bad for people… the antibiotics such as penicillin have beneficial use. However, from the mycological standpoint, antibiotics are considered mycotoxins since they too are generated by mould to ward off microorganisms (i.e. competing bacteria).  Read more about mites

When the organism is producing toxins, the toxins are known to be present in the cell wall of spores and hyphae. It can be relatively easy to see spores on wall surfaces, however, testing for these components to see if they have migrated into fabrics can be difficult without the right equipment and experience.

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Relying on visual sightings to ascertain the existence of mould is simply an inadequate method of testing for mould or VOC's.  Further more mould cannot be eradicated by simple domestic cleaning.  BMT and fully equipped and have many years of experience in this field.