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Do You Have Normal Mold Levels For Various Types Of Mold?

Question: Do you have the normal mold levels for various types of mold, i.e. Cladosporium cladosporioides? Thank you.

Answer: Currently there are no widely accepted normal airborne mold levels. Although no exposure standards have been established that relate health effects to specific airborne mold levels, there are concerns from public health agencies regarding exposure to mold. Much evidence exists indicating that indoor exposures to molds contribute to occupant respiratory disease and symptoms. Mold levels are used to give us an indication of whether the occupants are exposed to mold originating from indoor environment. According to the American Conference of Government Industrial Hygienists (ACGIH), indoor mold levels should be less than 1/3 of outdoors levels.  If indoor levels are above this amount, action should be taken to identify the source or location of mold growth and remove it.  It’s important to note that the outdoor levels of mold can vary quite a lot over the different seasons and even week to week and the same is reflected indoors.

In the literature, 3000 spores per cubic meter of air is quoted as the allergenic threshold for Cladosporium. More recently a figure of 4000 spores per cubic meter of air has been cited. For Alternaria, 100 spores per cubic meter of air is cited in the literature as the allergenic threshold.

It is normal to find mold spores in any indoor environment in the air and surfaces such as clothes, walls, and furniture.  Most of the time mold spores found indoors during a mold inspection is from outside sources and do not pose a hazard. Regular housekeeping cleaning helps keep mold levels low. Cleaning small areas of visible mold, like the mold around your shower, is important to maintain sanitary conditions.

References

  • Hollins, P.D., P.S. Kettlewell, M.D. Atkinson, D.B. Stephenson, J.M. Corden, W.M. Millington and J. Mullins. Relationships between airborne fungal spore concentration of Cladosporium and the summer climate at two sites in Britain. International Journal of Biometeorology Volume 48, Number 3, 137-141.

Moulds commonly found in carpet and mattress dust

A number of moulds are frequently found in carpet and mattress dust. Eurotium repens is the most frequently detected mould in mattress dust. Others include Aureobasidium pullulans, Alternaria alternata, Penicillium chrysogenum, Aspergillus penicilloides and Aspergillus restrictus.

More than 100 species of moulds have been recorded from carpet dust. As with mattress dust, the most frequently isolated mould in carpet dust is Eurotium repens. The others are Penicillium chrysogenum, Alternaria alternata, Aureobasidium pullulans and Phoma herbarum.

Concentrations of these moulds in carpet and mattress dust can be as high as 70 million colony forming units per gram of dust. Such high concentrations of moulds are likely to cause respiratory allergy or irritating symptoms. Therefore, it is import to regularly HEPA vacuum the carpets, mattresses and upholstered furniture to reduce the dust and spore concentration. If people are suffering from reoccurring respiratory allergy or irritating symptoms in a building where there is no visible mould, it is suggested that dust be tested for the types and concentrations of mould present.

It’s The Allergy Season!

While we are enjoying the summer, it can be a tough time for allergy sufferers. The concentrations of pollen and mold spores in outdoor environment is highest in summer months. Since mold spores and pollen tend to infiltrate into indoor environment their concentration indoors can also be very high in summer. Molds and pollen capable of causing allergic reactions in sensitive individuals are said to be allergenic. Allergy follows inhalation of large amounts of spores or pollen grains. The amounts capable of triggering allergy depends on the specific allergen and the sensitivity of the individual.

Types Of Mold Allergy
Molds as causative agents of respiratory allergy and asthma have been known since the 18th century. Allergic reactions to molds may be either immediate, developing within minutes of exposure (Type I), or delayed, occurring 4 – 8 h later (Type 111). Two of the most important allergenic molds are Alternaria alternata and Cladosporium herbarum. Concentration of these two molds are usually highest outdoors from June to October.

Fungi produce huge amounts of spores. In his book, “The Fifth Kingdom”, Dr. Bryce Kendrick, gives the following examples:

  • One specimen of the common bracket fungus discharges 30,000,000,000 spores per day every day from beginning of May to the end of September
  • A 2.5 cm diameter colony of the green mold, Penicillium, can produce 400,000,000 spores.

Fortunately, these huge numbers are diluted by air and we inhale far much less spore concentrations.

Allergenic Pollen
Among the well known allergenic pollen is the ragweed pollen. Individuals sensitive to ragweed pollen are also sensitive to other pollen grains such as those of poverty weed and false ragweed. Concentrations of these pollens are highest within the months of June to September depending on the flowering time of the particular weed.

Alternaria alternata

Alternaria alternata spores, picture

Alternaria alternata is one of the fungal species referred to as “leaf fungi” (phylloplane). It has a worldwide distribution and is frequently isolated from a wide range of plants, soil, food, and indoor air. In indoor environments, Alternaria alternata has been isolated from dust on floors, carpet and mattresses. It is occasionally found on damp walls, gypsum board and wallpaper. Alternaria alternata is closely related to Ulocladium chartarum.

Ulocladium spores, picture

It is possible that Ulocladium chartatum is commonly misidentified as Alternaria alternata in commercial microbiology laboratories.

Alternaria alternata has been associated with a number of respiratory problems such as rhinitis, asthma, allergic dermatitis and allergic sinusitis. The spores and the hyphal fragments are the cause of the allergic reactions.

If you have any question related to mould or bacteria, feel free ro contact us at 905-290-9101.

What are the common types of indoor mould?

Often we get questions from homeowners who want know what the black mould growing in their bathrooms, baseboard, window sills or drywall is likely to be. Black mould is often erroneously thought to be Stachybotrys and also to be the most dangerous mould. However, not every mould that appears black is Stachybotrys. There are a number of other moulds that may appear black. These include Pithomyces, Stemphylium, Ulocladium, Aureobasidium, Alternaria, Memnoniella and even some species of Aspergillus for example Aspergillus niger.

Some mould species may be very common in the bathroom, kitchen, basement or on certain building materials such as the drywall, damp paint, carpet, wood, etc. Moulds that produce large amounts of the enzyme cellulase are commonly found growing on wet cellulose containing material. The best examples of moulds in this category are Chaetomium spp and Stachybotrys spp.

Generally the type of mould growing on any substrate (material) is determined by the composition of the substrate and the water activity of the substrate. For some more details on common indoor moulds visit the web page http://www.moldbacteria.com/mold/common-building-moulds-their-hazard-classes.html.

Do you have a mould problem? Call (905)290-9101.

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