Mold Bacteria Consulting Services

Serving Ontario and British Columbia

You are here: Home / Archives for Fungi

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.

Alternaria And Other Mould Spores As Causes Of Allergy

As far back as 1924 Prof Dr Willem Storm van Leeuwen from The Netherlands suggested that inhaled mould spores such as those of Alternaria could cause asthma. The types of moulds widely known to cause respiratory allergy in humans include Aspergillus, Penicillium, Cladosporium and Alternaria. The allergic responses are mainly due to the inhalation of spores rather than mycelial/hyphal fragments. Allergic reactions to each spore type differ between individuals. Mould allergens also vary in the severity of the allergic reactions they induce. More people, for example, are more sensitive to Alternaria than to Cladosporium. Alternaria also produces more severe reactions, while Cladosporium generally only produces a mild reaction. Cladosporium and in particular Cladosporium herbarum, are often the major contributors to outdoor air-spora. Due to their high concentrations they are a major cause of inhalant allergy and allergic asthma in humans. Occupational pulmonary diseases are common in cheese industry (Penicillium roquefortii), breweries (Aspergillus clavatus) and in mushroom farms (Doratomyces sp).

Alternaria is cosmopolitan and ubiquitous in nature. It is currently comprised of about 40-50 species. Alternaria is a well recognized plant disease causing agent. Species of Alternaria are commonly isolated from dead plant materials, soil, food, and indoor air. Alternaria alternata has been isolated from numerous kinds of organic materials in damp situations, including textiles, stored food, canvas, cardboard and paper, electric cables, polyurethane, jet fuel, sewage and effluents. Airborne spores of Altenaria alternata and A. tenuissima are found in very high numbers in the outdoor environment during fall.

Spores of Alternaria alternata as seen under a microscopeAlternaria alternata is a well recognized allergen with airborne spores and mycelial fragments being responsible for the allergic symptoms in individuals with rhinitis or bronchial asthma. Alternaria sensitivity can also lead to severe and potentially fatal asthma. Studies have shown that up to 70 % of mould-allergic patients have skin test reactivity to Alternaria. It has also been shown that prolonged heavy exposure to Alternaria alternata spores and mycelial fragments mimics that of other allergens such as cat dander and dust mites. Since Alternaria is a seasonal mould then this type of allergy is more prevalent in the fall. A. alternata has also been recorded as an opportunistic pathogen causing skin diseases particularly in immunocompromised patients such as the bone marrow transplant patients.

The presence of Alternaria together with other moulds such as Ulocladium spp and Phoma spp, in indoor environment is indicative of humid conditions. Alternaria alternata is not commonly isolated from indoor building materials and in most instances spores found in indoor air environment may have originated from outdoor sources. A closely related mould, Ulocladium chartarum, which is very common in indoor environment is frequently misidentified in labs as Alternaria alternata. U. chartarum is common on wallpaper and drywall, and has been isolated from emulsion paint, polyurethane, plywood and manila fibre.

Should you have a question on Alternaria or any other mould, please send it to My Question.

What Are Some Of The Mycotoxins Producing Indoor Moulds?

Growth of mould on building materials is determined by the water activity (aw) among other factors. The aw is a measure of the moistness of the material. Some moulds are capable of growing over a wide range of aw but there is always an optimal range. While these moulds grow, they reach a stage when they produce mycotoxins depending on the growth conditions. Some of the indoor moulds that produce mycotoxins are discussed below.

Stachybotrys chartarum
Stachybotrys chartarum is cosmopolitan and grows naturally on straw and other cellulose containing materials in soil. In the indoor environment, this mould is commonly found together with other water-loving moulds on cellulose containing materials including paper, canvas and jute which are wetted to a water activity > 0.98. Stachybotrys chartarum produces a number of mycotoxins inclduding macrocyclic trichothecenes, satratoxins and roridins when growing on building materials. The optimum temperature for growth of Stachybotrys chartarum is 23 oC with a minimum and maximum temperature of 2 and 37 oC respectively. The optimal water activity is 0.98 with a minimum at 0.89.

Aspergillus flavus
Aspergillus flavus is widely distributed in soil. It is associated with a wide range of stored products such as maize and nuts. In indoor environment it is commonly found on damp walls, wallpaper, floor and carpet dust, tarred wooden flooring, humidifiers and HVAC fans, bakeries, shoes, leather, and bird droppings. Strains of this mould may produce mycotoxins such as aflatoxin, a class 1 carcinogen. The minimum and maximum temperatures for growth are 6 and 45 oC, with an optimum at 40 oC. The minimum water activity is 0.78 and an optimum at 0.98.

Aspergillus fumigatus
Aspergillus fumigatus is common in composting plant material, woodchips and garbage. Also common in dust infiltrating from outdoor air, carpet and mattress dust, wet building and finishing material, HVAC insulations, fans, filters, humidifier water and potted plant soil. A. fumigatus is a producer of various mycotoxins including gliotoxin, verrucologen, fumitremorgin A & B and fumigaclavines among others. A. fumigatus has an optimum growth temperature at 43 oC and minimum and maximum at 10 and 57 oC respectively. Minimum water activity for A. fumigatus is 0.82 and the optimum is 0.97.

Aspergillus niger
Aspergillus niger is found worldwide in soil and plant litter. In indoor environment A. niger is common in floor, carpet and mattress dust, acrylic paint, UFFI, leather, HVAC filters and fans, and potted plant soil. A. niger produces mycotoxins such as malformins and a few strains also produce ochratoxin A. A. niger requires a minimum temperature for growth of 6 and maximum of 47 oC with an optimum at 37 oC.

Aspergillus versicolor
Aspergillus versicolor is very common on gypsum board, floor, carpet, mattress and upholstered-furniture dust, and damp walls. A. versicolor produces high quantities of the carcinogenic mycotoxin, sterigmatocystin at water activities (aw) above 0.95. A. versicolor is generally xerophilic- meaning that it can grow at low water activity (< 0.8). The minimum and maximum growth temperatures for A. versicolor are 4 and 40 oC with an optimum at 30 oC. Its optimal water activity is 0.95 with a minimum at 0.75.

Penicillium chrysogenum
Penicillium chrysogenum is one of the most common indoor moulds. It’s not known to produce highly potent mycotoxins. It is extremely common on damp building materials, walls and wallpaper; floor, carpet mattress and upholstered-furniture dust. P. chrysogenum produces few detectable metabolites and often none when growing on building materials. Lack of observed effects on persons exposed to high quantities of spores and the production of few metabolites suggest this species may not be an important health hazard. However, some strains may cause allergenic reactions to susceptible individuals. P. chrysogenum can grow at a minimum temperature of -4 oC, an optimum of 28 oC, and a maximum of 38 oC. It has minimum water activity of 0.79 and an optimum at 0.98

Penicillium brevicompactum
Penicillium brevicompactum is common on damp walls and building materials e.g., gypsum board; floor, carpet, mattress and upholstered-furniture dust. P. brevicompactum produces mycophenolic acid. P. brevicompactum can grow at -2 and 30 oC with an optimum at 25 oC. Its water activity requirements are a minimum of 0.75 and an optimum at 0.96.

Chaetomium globosum
Chaetomium globosum is common on cellulose containing building materials that has been very wet such as gypsum board, cellulose board and wood. Species of the genus Chaetomium are known to produce mycotoxins. C. globosum produces high quantities of chaetoglobosins. C. globosum requires a water activity of >0.90.

Trichoderma species
Trichderma species are frequently found on gypsum board and water saturated wood; floor, carpet and mattress dust; paint; domestic water supply, and HVAC system air. In one study, Trichoderma species were not found to produce detectable quantities of trichothecenes when growing on building materials. Less than 1% of the isolates produced trichodermol or its esters.

References
Kuhn, D. M. and Ghannoum, M. A. (2003). Indoor Mold, Toxigenic Fungi, and Stachybotrys chartarum: Infectious Disease Perspective. Clinical Microbiology Reviews, 16(1):144–172.Nielsen, K.F, (2002).

Mould growth on building materials: Secondary metabolites, mycotoxins and biomarkers, Dissertation, The Mycology Group, Technical University of Denmark. 116p

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

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. […]