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Indoor Mould: The Mould Fusarium

Fusarium species exist as plant pathogens or saprophytes on plant debris and in soil. Plant parasitic Fusarium cause wilting of many plants including crops such tomatoes, bananas, sweet potatoes, pigeon peas, and pears. Some species of Fusarium are commonly isolated from seeds especially those of cereals. Species of Fusarium also produce a number of different mycotoxins which include trichothecenes (T-2 toxin, HT-2 toxin, deoxynivalenol (DON) and nivalenol), zearalenone and fumonisins. The Fusarium species are probably the most prevalent toxin-producing fungi of the northern temperate regions and are commonly found on cereals grown in the temperate regions of America, Europe and Asia. These toxins have been shown to cause a variety of toxic effects in both experimental animals and livestock and are also suspected to cause toxicity in humans.

In indoor environment Fusarium species are commonly found under very wet conditions. They are commonly isolated from carpet and mattress dust; damp walls, wallpaper; polyester polyurethane foam; humidifier pans and other areas where stagnant water occurs in HVAC systems. Some species cause keratitis in man, and infects eyes and finger nails. Fusarium species are also an inhalation hazard.

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Mould Allergies

Moulds have a protein and polysaccharide components that make them potentially allergenic to sensitized individuals. Due to their small size, mould spores are able to penetrate deep into the respiratory tract where they can elicit allergic reactions. There are 2 types of respiratory allergy, the type I allergy (immediate hay-fever or asthma) and the type III (delayed farmer’s lung). Type I allergy occurs only in atopic (allergic) individuals.

Type I allergy may be caused by plant pathogens such as Tilletia caries, Fulvia fulva, and Leptosphaeria nodorum. Saprophytic moulds such as Cladosporium herbarum and Alternaria spp occurring in indoor environment or from rotting vegetation can also cause type 1 allergy. Mouldy straw, hay and decaying leaves are important sources of allergenic moulds such as Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, and Penicillium spp.

There are occupational pulmonary and epidermal allergies. The former occur in the cheese industry (Penicillium roquefortii), the breweries (Aspergillus clavatus), mushroom farms (Doratomyces sp) and compositing sites (various moulds). An example of epidermal or skin allergies is the cane harvesters allergy caused by Arthrinium sp.

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Indoor Mould: Do Not Panic!

Phrases like toxic mould or black mould are common on advertisements and the media. These phrases create fear, panic and confusion. It is a fact that exposure to mould can result to ill-health. However, some decisions on mould are based on fear rather than facts.

What You Should Know About Mould

  • Mould is found everywhere. However, growth of mould at 60% relative humidity is highly restricted. We can therefore, control indoor mould growth by providing adequate ventilation and maintaining indoor humidity levels at 60% or less. When excessive moisture or water accumulates indoors, mould growth will often occur, if the moisture problem remains unnoticed or un-addressed for more than 48 hours. The key to mould control is timely maintenance and prompt repairs.
  • About 150 different types of moulds occur in indoor environment. But not all these are harmful though to be safe it is better to treat all moulds as potentially harmful. The colour of the mould does not determine whether it is harmful or not. Therefore black mould is not necessarily bad mould. Mould related health effects depend on:
    • types of mould present,
    • amount of mould one is exposed to and for how long,
    • individual health status or sensitivity. Children, elderly and sick people are more vulnerable to mould.
  • It is difficult to eliminate all mould and mould spores in the indoor environment. However, the levels can be minimised by controlling growth. Monitor mould growth by looking for water stains or discoloration on the ceiling, walls, floors, and windowsills.

What You Should NOT Do When You Find Mould

  • Disturb the mould without proper personal protection and the protection of occupants.
  • Try to clean more than 10 square feet of mould contamination if you are not trained to handle mould.
  • Cause panic among the building occupants.
  • Use a chemical to control indoor mould if such a chemical is not registered for mould control in indoor environment.Do you have a question on mould? Send it to My Question.

Occurrence of the Mould Chaetomium in Indoor Environment: What Are the Implications?

Chaetomium is a cellulose degrading mould commonly found in soil, air, and decaying plant material. There are several species of Chaetomium. The most common ones are Chaetomium atrobrunneum, Chaetomium funicola, Chaetomium globosum, and Chaetomium murorum. In indoor environment the most common species of Chaetomium is Chaetomium globosum. Presence of Chaetomium species in indoor environment is a sign of serious water problem. Chaetomium may occur together with other water-loving moulds such Fusarium, Stachybotrys and Ulocladium. Species of Chaetomium are known to produce mycotoxins but to what extent these toxins contribute to poor indoor air quality or affect human health is not documented. In the medical literature some species have been reported to cause disease in immuno-compromised individuals.

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Moulds: How Are They Named?

Non-biologists often find names given to moulds difficult. The current system of naming fungi (the kingdom to which moulds belong) and other living organisms including plants and animals was introduced by Linnaeus in 1753. In this system (referred to as binomial nomenclature) an organism is identified by 2 names, i.e., the generic name and a specific name. For example, for Aspergillus niger, the generic name is Aspergillus and the specific name (or epithet) is niger. These names may be descriptive or given to commemorate the work of researchers or benefactors, or the place where the fungus was found; thus Aspergillus chevalieri is named after the French mycologist F.F. Chevallier (1796-1840), and Aspergillus amstelodami was originally discovered in Amsterdam. Aspergillus niger is descriptive. It refers to a mould with conidiophores (spore bearing structures) which are swollen at the apex, which produces chains of conidia (spores) and that the fungus is black (Latin: niger), and that it has the appearance of a mop (Latin: aspergillum).

Sometimes a fungus (plural is fungi) may have more than one name. For example Stachybotrys chartarum is still called by some people as Stachybotrys atra. This happens when the name of a fungus is changed. Name changing occurs if the original description of the fungus was inadequate so that the fungus is not recognizable to others and subsequently given new name(s) or through recognizing spurious differences between individuals as taxonomically significant. Much of the duplication is due simply to the enormous body of literature which must be searched through to find previously-published names which may be applied to apparently new species. A fungus may also be referred by more than one name if it exists in different forms (or states). Each form may have a different name.

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Salmonella food poisoning and symptoms

Salmonella food poisoning has been a growing concern in recent news. It has frequently lead to recalls of beef, salads and organic products and, even peanut butter products. Salmonella food poisoning occurs when one eats raw or undercooked foods such meat, poultry, eggs or egg products. Properly cooked food can get contaminated with Salmonella if […]

Legionella pneumophila – Guidelines for Laboratory Interpretation

Legionella pneumophila is a Gram negative, aerobic bacteria that is characterized as an opportunistic pathogen. It is the cause of Legionnaires’ Disease, a severe form of pneumonia and, it is the cause of Pontiac fever, a non-pneumonic form of L. pneumophila infection. Legionella spp.’s mode of transmission is through aerosols or aspiration of contaminated water. The Public Health […]

The Indoor Mold Is An Early Warning Device

The mold (or mould, in the Queen’s English) has been the victim of a bad press. Mention the word and it conjures up an image of something rotting or in the process of decomposition. And yet, were it not for the mold that inspired the discovery of penicillin millions of lives would have been lost. […]