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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.

Cryptococcus gattii: What is It?

An alert has been issued on the spreading of Cryptococcus gattii from the Vancouver Island to Mainland British Columbia (CBC News, Friday, June 03). What is this Cryptococcus gattii? It is a yeast-like fungus belonging to a group of fungi called Basidiomycetes (where mushrooms also belong!). This fungus was thought to have a restricted geographic distribution in the tropics and subtropics. It is has been reported in Australia, Papua New Guinea, parts of Africa, the Mediterranean region, India, south-east Asia, Mexico, Brazil, Paraguay and Southern California. The BC report was the first outside the tropics and subtropics.

Cryptococcus gattii has an unusual association with trees. In Australia it is associated with some Eucalyptus trees. In British Columbia, however, Cryptococcus gattii has been recovered from multiple species of native trees, but not from any of the introduced Eucalyptus species. It has been isolated from soil, barks of trees and from the air.

Unlike indoor moulds and yeasts, Cryptococcus gattii is a true pathogen and therefore can infect even healthy people. It has a preference for respiratory and nervous systems of humans and animals. Exposure to humans is mainly through inhalation of airborne spores into the lungs.

Should you have a question on mould, send it to us at My Question.

Mould from Your Neighbour’s House: How Can It Affect Your Health?

In one community a family purchased a mobile home. Shortly after they moved in, their 2 kids got sick. It was determined that the home was contaminated with some black mould. For over 2 years nobody had entered the home after the family moved out. Some neighbours were wondering if there was any health risk to them given that the mould was not cleaned up and the windows and garage door of this house were partially open.

Mould from a house is unlikely to affect the health of the people living in the neighbourhood. The concentrations of biological material escaping from such a house would be highly diluted by the outdoor air to have any significant effect on the majority of the population. Outdoor moulds growing on dead organic material and on plants release into the air huge amounts of spores daily. Only on some occasions do the outdoor spores reach levels that affect some people.

Should you have a question concerning mould, send it to us at My Question.

Mold and Mildew

The terms mold and mildew confuse some non-biologists. Mold and mildew are common names used to refer to those fungi whose body is made of a network of filaments (referred to as mycelium; plural, mycelia). Mold and mildew are the same thing. Although, the term mildew is occasionally used to refer to fungi that grow in indoor environment and on fabrics, it strictly refers to a plant disease where the fungus causing the disease is seen as a growth on the surface of the host; for example, powdery mild and downy mildew.

Mold is sometimes combined with adjectives to refer to some common molds. For example: black-mold (Aspergillus niger), blue-mold of citrus (Penicillium italicum), blue-mold of apple (Penicillium expansum); green-mold of citrus (Penicillium digitatum), bread-mold (Chrysonillia sitophila, Rhizopus, Mucor), grey-mold of snowdrop (Botrytis cinerea), white-mold of sweet pea (Hyalodendron album), tomato leaf-mold (Fulvia fulva), and pin-mold (Mucor and other related moulds). The term mold can be spelt with or without a “u” depending on whether one is using British or American English.

Mildew can also be combined with other terms to refer to plant diseases for example, powdery mildew or downy mildew.

Fungi include yeasts (which are non-filamentous and therefore not molds), molds/mildew, tree bracket fungi, the truffles and the mushrooms.

Should you have a question on mold and mildew, please send it to My Question.

Mould in Your Home Or Office: What You Should Know

As you read this article there could be some mould growing silently somewhere in your house or in the office where you work. This thought may not have bothered you if you had not heard in the media phrases like “toxic mould” or “black mould”! These phrases create fear, panic and confusion. The objective of this article is to provide the reader with some basic facts about mould and the associated health effects.

Should One Be Concerned About Indoor Mould Growth?

Yes. Apart from mould being unsightly in a building there are 3 good reasons why people should be concerned about mould growth.

Health Risk

As mould grows indoors, it produces spores and/or chemical compounds that easily become airborne. The health effects associated with inhaling or getting into contact with these spores and chemicals may include runny nose, eye irritation, cough, congestion, aggravation of asthma and respiratory problems, headache, flu-like symptoms, fatigue, skin rash and other allergic reactions. Individuals with weak immune systems may also get infected by certain moulds as a result of exposure.

Legal Issues

Those responsible for building maintenance or health and safety of building occupants, contractors and other professionals involved in the building operations are at risk of being sued if occupants get sick from mould growth.

Material Damage and Impairment of Processes

Mould if allowed to grow, can impair the functioning of many processes from air conditioning units to electrical circuits. Surfaces of materials on which mould is growing get stained or discoloured and may disintegrate over time. Wood-rotting moulds are capable of weakening wooden structures.

Three Things You Should Know About Mould

  • Mould growth is a fact of life for almost all industrial and indoor environments. However, mould growth can be controlled by providing adequate ventilation and maintaining indoor humidity at levels below 65%. When excessive moisture or water accumulates indoors, mould growth will often occur, particularly if the moisture problem remains unnoticed or unaddressed for more than 48 hours. The key to mould control is keeping the building dry and clean, timely maintenance and prompt repairs.
  • Not all moulds are harmful but 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 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, baseboards, floors, and window sills. Pay particular attention to the basement and the attic.

What Should You Do When You Find Mould?

If you are an indoor mould consultant

  • Assess the extent of the mould problem.
  • Discuss the problem with your client and reassure them.
  • Have the dominant moulds identified preferably to species level. However, before sampling, prepare a sampling plan that details how and when samples
    would be collected, the type of samples to collect, collection requirements for each type of samples, the criteria to use to interpret results, and the benefits expected from sampling, i.e., what question(s) would be answered by the laboratory results and what actions would be taken. Share the sampling plan with the client.
  • Discuss the lab results with the client. If the client is concerned about their health, advise them to seek medical opinion from their family doctors.
  • Discuss the remediation plan (or options if any), the remediation costs and the expected results with your client.

If you Are a Property Manager or Homeowner

  • Do not panic! The presence of mould does not necessarily mean that you or the building occupants could have adverse health effects or that they have even been exposed.
  • Do not disturb the mould since this could help the mould in shedding more spores into the air.
  • If what you suspect to be mould covers more than 10 square feet, seek the advice of a qualified consultant immediately. If unsure of how to handle mould covering less than 10 square feet, seek professional advice. Avoid exposing yourself or others to mould.
  • Ask for the mould to be identified to reassure yourself or the building occupants that it is not among those that cause serious health effects.
  • Discuss the problem with your family doctor or if you are the property manager reassure the occupants and let them know the actions you are taking.
  • If you find a professional who seem to concentrate more on how the mould could or have affected you or the building occupants, seek a second opinion. A good professional should provide facts and avoid causing fear.

 

Should you have a question concerning indoor moulds, please send your question to My Question.

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