What type of mould do I have? The Primary, Secondary and Tertiary Colonizers If a water problem in a building is not repaired and the water dried out within 48 hours, growth of mould and other micro-organisms would naturally occur. The types of moulds predominant at anyone time would be determined by the level of moisture in the building material. This level of moisture is usually referred to as the water activity and it determines the order in which different categories of moulds appear. The first group of moulds to appear (at water activities less than 0.85) is referred to as the primary colonizers, the second group (at water activities of 0.85-0.90) is secondary colonizers and the third group (at water activities greater than 0.90) is the tertiary colonizers.
Primary Colonizers The primary colonizers are capable of growing at water activities below 0.85. This group may include Alternaria citri, Eurotium amstelodami, Aspergillus candidus, Aspergillus glaucus, Aspergillus niger, Aspergillus penicillioides, Aspergillus repens, Aspergillus restrictus, Aspergillus versicolor, Paecilomyces variotii, Penicillium aurantiogriseum, Penicillium brevicompactum, Penicillium chrysogenum, Penicillium commune, Penicillium expansum, Penicillium griseofulvum, and Wallemia sebi.
Secondary Colonizers Secondary colonizers grow best at water activities of 0.85 to 0.90. Secondary colonizers may include Aspergillus flavus, Cladosporium cladosporioides, Cladosporium herbarum, Cladosporium sphaerospermum, Mucor circinelloides, and Rhizopus oryzae.
Tertiary Colonizers At water activities greater than 0.90, tertiary colonizers appear. These may include Alternaria alternata, Aspergillus fumigatus, Epicoccum spp., Exophiala spp., Fusarium moniliforme, Mucor plumbeus, Phoma herbarum, Phialophora spp., Rhizopus spp., Stachybotrys chartarum, Trichoderma spp., Ulocladium spp., Rhodotorula spp., Sporobolomyces spp., and Actinomycetes.
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.
Common Building Moulds and Their Hazard Classes In some countries indoor moulds have been grouped into 3 hazard classes based on associated health risk. These classes are similar to risk groups assigned to microorganisms handled in laboratory environments.
Hazard Class A: includes fungi or their metabolic products that are highly hazardous to health. These fungi or metabolites should not be present in occupied dwellings. Presence of these fungi in occupied building requires immediate attention.
Hazard class B: includes those fungi which may cause allergic reactions to occupants if present indoors over a long period.
Hazard Class C: includes fungi not known to be a hazard to health. Growth of these fungi indoors, however, may cause economic damage and therefore should not be allowed.
Mould Types in Homes and Their Hazard Classes Hazard Classes of Indoor Mould In some countries indoor fungi have been grouped into 3 hazard classes based on associated health risk. These classes are similar to risk groups assigned to microorganisms handled in laboratory environments.
Level A is the highest level and typically Aspergillus fumigatus is a recognised by the HSE as requiring level A protection in laboratories dealing with it and typical other level A hazards include Ebola and Legionella
Hazard Class A: includes fungi or their metabolic products that are highly hazardous to health. These fungi or metabolites should not be present in occupied dwellings. Presence of these fungi in occupied buildings requires immediate attention.
Hazard class B: includes those fungi which may cause allergic reactions to occupants if present indoors over a long period.
Hazard Class C: includes fungi not known to be a hazard to health. Growth of these fungi indoors, however, may cause economic damage and therefore should not be allowed.
The following moulds are commonly found on water damaged or damp surfaces in kitchens, basements, bathrooms, ceilings, and other drywalls. Occurrence of some of these moulds such as Stachybotrys, Fusarium, Ulocladium and Trichoderma in a building is an indication of serious water damage.
Mould Genus
Mould species
Hazard
Typical location
Aspergillus
Fumigatus &Versicolor & niger& flavus
A
Kitchen,bathroom, mattresses and carpets,basements and cellars, soil
Chaetomium
globosum
C
Kitchen ,bathroom, mattresses and carpets ,wallpaper/plasterboard
Cladosporium
cladosporioides
B
Kitchens ,bathrooms window frames
Cladosporium
sphaerospermum
C
Wallpaper/Plasterboard
Fusarium
spp
A
Basement & cellars
Penicillium
Chrysogenum & aurantiogriseum
B
Mattresses and carpets
Scopulaiopsis
spp
B
Wallpaper /Plasterboard, mattresses andcarpet
Stachybotrys
chartarum
A
Wallpapers/Plasterboard
Tricoderma
spp
B
Wallpapers/Plasterboard
Ucladium
botrys
C
Kitchens and bathrooms
Points to be used in the assessment of exposure or health risk: Air sampling is the main route to identifying risk and hazard unless visible mould has been identified in which case it should be assumed airborne contamination is present. ir sampling should follow British Standard BSEN 16000-19 which specifically requires dead and live mould to be measured, this is because both represent potential health hazards especially where attempts to kill mould have been made. Level A hazards are invariably below detection levels in outside (ambient) air. Even low levels of level A may be an indicator of very serious indoor air quality hazards. Tertiary spores often have poor air buoyancy making identification difficult unless sampled close to the contamination point. Air may also contain other biological hazards including bacteria and various endotoxins all of which are potentially hazardous. While the allergic or toxic effects of single moulds are relatively unknown, the combination of different genus or symbiotic effects between mould and bacteria are completely unknown. Health deterioration is the major indictor of post water damage biological activity.
