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Indoor Mould And Bacteria

Proliferation of indoor mould and bacteria in dwelling places could lead to ill-health of the occupants. Indoor microbial growth and dampness has been associated with a number of respiratory problems including:

  • Respiratory symptoms such as coughing and wheezing.
  • Respiratory infections such as aspergillosis.
  • Allergic diseases, including allergic asthma and bronchitis.
  • Non-inflammatory, unspecific symptoms, e.g., eye and skin irritation, fatigue, headache, nausea, and vomiting.

The best way to control microbial growth in a building is to ensure the building is well maintained and any water leaks are repaired promptly.

Once mould has grown in a building, the solution to the problem is to have the water source identified and repaired and the mould removed. This can be expensive especially if the work is to be performed by professionals.

To avoid expensive mould investigation and removal, the homeowners and property managers should:

  • Continuously monitor for any water leaks and have them repaired promptly.
  • Continuously monitor for mould growth so as to detect it before it spreads.

Do you have a mould question? Send it to My Question.

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.

Do you have a mould question? Send it to My Question.

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.

Indoor Mould Infection: Can Mould Cause Bad Breath?

A person was exposed to mould in an office and they have developed bad breath which they didn’t have before. Could the bad breath be due to mould infection in their lungs? This is not a ‘yes/no’ question because whatever answer one gives should be supported with facts derived from documented evidence or tests conducted to such as person by a qualified person. The first answer that came to my mind was to say no. But then I realized there is still a lot that is not known about mould and their health effects. I was imagining that if the person had mould infection and the mould was actively growing in their lungs to the level of causing or producing odour, such a person would be critically ill. But my thinking is not based on any facts. It is just thinking.

The most well known lung mould infection is aspergillosis caused by some species of Aspergillus (hence the name aspergillosis). Moulds that are known to cause aspergillosis are Aspergillus fumigatus, Aspergillus flavus and occasionally Aspergillus terreus, Aspergillus nidulans, and Aspergillus niger. These moulds are widespread in the environment. They are found in soil, decomposing organic matter, household dust, building materials, and air. The people at risk of infection by these moulds are mainly those undergoing certain medical treatments that affect their immune system. In these people the disease is manifested as invasive pulmonary infection, usually with fever, cough, and chest pain. In healthy people, the disease is manifested as localized pulmonary infection. Aspergillus species also cause allergic reactions.

Do you have a mould question? Send it to us.

How Old Is The Mould In My House?

Often, people wonder if it was possible to tell how old mould growing in a house was and/or whether the mould was actively growing and what the source of the mould was. The answers to these questions would help in situations where say somebody buys a house and some months later they discover mould. If they would tell the mould was there before buying the property, they would follow it up with the seller for not disclosing the mould problem. Unfortunately there are no simple tests that can tell us the age of mould growing in a house, whether it is actively growing and the source. We can only speculate on a range of number of days since the current growth appeared and whether it was likely to be actively growing. It would be difficult to tell the source of the mould and how long it has been there before the growth was seen.

How moulds interact in nature

Mould propagules are ubiquitous in indoor environments and are well adapted to inhabit this ecological niche if just sufficient water is available. Based on the water activity (or equilibrium relative humidity) requirements, moulds can be divided into 3 broad groups:

  • Primary colonizers

Primary colonizers (also referred to as xerophiles) are the first to appear. They are capable of growing in relatively dry conditions at water activities of between 0.6-0.8. These kinds of conditions can be achieved through slow leaking pipes, condensation or other sources of moisture. At this low water activity viable propagules (spores and mycelial fragments) of species of Wallemia, Penicillium, Aspergillus and Eurotium would germinate and form growth.

  • Secondary colonizers.

As the water activity of the building material increases to between 0.8 and 0.9, the secondary colonizers would proliferate. Secondary colonizers include species of Cladosporium, Phoma, Ulocladium, Alternaria and also some species of Aspergillus such as A. flavus and A. versicolor. If nutrients are still available on the substrate and the water activity remains unchanged the secondary colonizers would gradually become the dominant moulds.

  • Tertiary colonizers.

At water activity of 0.9 and above, the water loving moulds (also called hydrophiles) would dominate as the tertiary colonizers. These levels of water activity are generally only met by incoming water as under flooding conditions and not just high humidity or condensation on indoor surfaces. Immediately after the flooding or serious water leakage, for example, all types of moulds would colonize the wet building material but with those that require higher water activity dominating. Presence of tertiary colonizers in a building is an indication of a serious water problem. Tertiary colonizers include moulds such as Stachybotrys, Chaetomium, Ulocladium, Trichoderma, Aureobasidium as well as actinomycetes and other bacteria.

 

Do you have a mould question? Send to My Question.

Salmonella food poisoning and symptoms

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Legionella pneumophila – Guidelines for Laboratory Interpretation

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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. […]