Dr Jackson Kung'u- Mold Specialist

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Dr. Jackson Kung’u (PhD)- Mold Specialist.
Phone: 905-290-9101
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Standard Test Method for Categorization and Quantification of Airborne Fungal Structures in an Inertial Impaction Sample by Optical Microscopy

The ASTM International has published the first standard method for enumeration and identification of spores collected on inertial impactors. Currently, there are significant differences in the methods used by labs to analyse spore traps. These differences have made comparison of results from various labs difficult. The method “ASTM D7391 – 09 Standard Test Method for Categorization and Quantification of Airborne Fungal Structures in an Inertial Impaction Sample by Optical Microscopy” will help the labs using this method to analyse samples in a similar manner.

However, the standard is unlikely to overcome the limitations of spore traps but it is a good start in developing scientifically sound standard methods for analysis of spore traps. The standard also leaves the interpretation of results to the individual consultants. For details about the standard, visit http://www.astm.org/Standards/D7391.htm.

Calgary Health Region Mould Guideline

Question: My house just got tested for mould. The outside test was 67 spores per cubic meter of air. The inside was 24,000 spores per cubic meter of air for Aspergillus/Penicillium type.

I heard the city of Calgary has a standard that says you double the counts for control/outside and add a hundred for acceptable limits of the inside. Do you have a link for this?

What health problems can this be associated with in the long term?

Thanks.

 

Answer: Yes, the Calgary Health Region has developed a mould guideline entitled “Fungal Air Testing, Investigation and Reporting Requirements for Residential Marihuana Grow Operations” which provides guidelines on how to interpret air sample results. They have also developed “MARIHUANA GROW OPERATION REMEDIATION GUIDELINES.”

The long term effects of mould exposure varies with individuals. Some people may develop sensitivity to mould.

Mould Growth

Dampness and mould growth are recognised as major problems affecting a
significant proportion of houses in the North America. Apart from health problems associated with dampness and mould growth, wood decay is also significant problem.

Mould growth in houses is unsightly. But most important, there is considerable evidence to support the view that mouldy housing has a detrimental effect on the health of occupants residing in such environments. This is a cause for concern, considering that many individuals spend most of their time indoors especially during winter. Respiratory problems and allergic reactions are the common health problems associated with mould. Generally, indoor moulds affect people through inhalation of airborne spores. High levels of airborne spores may occur due to growth of mould on walls and furnishings.

Requirements For Mould Growth
Requirements for mould growth in buildings include:

  • nutrients: found in the materials which make up or are deposited on indoor surfaces
  • oxygen. Like most other living things, common indoor moulds require air (oxygen) for growth.
  • suitable temperature (around 25 degrees Celcius)
  • moisture: the relative humidity (RH) at a surface is the best indicator of moisture available for mould growth.

In most cases, mould growth in homes is caused by condensation. Condensation in buildings occurs where moist air meets a cold surface. For example if air meets cold water pipes, window glasses or other cold surfaces and is cooled below its dew point temperature, the vapour close to the surface becomes saturated and excess vapour turns to liquid.

There are two types of condensation:

  • Surface condensation. Surface condensation occurs at the surface of the material.
  • Interstitial condensation. Interstitial condensation occurs inside a material. If vapour passes through porous building materials and the dew point temperature occurs within that material then the vapour will condense. Interstitial condensation is responsible for mould growth in building envelopes.

The major factors influencing condensation in buildings include:

  • Moisture production from sources inside the building. Moisture sources include respiration, cooking, washing and drying of clothes.
  • Air and structural temperatures
  • Ventilation. Proper ventilation helps to reduce condensation. 

Spore Trapping And Counting

Spore trapping and counting is extensively used in crop protection to:

  • determine the concentration of pathogenic spores carried by wind
  • forecast a disease outbreak
  • get facts about periodicity of spore showers on crops as one of several infection requirements
  • determine correct timing of protectant sprays and other control measures. 

Spore trapping and counting also provide useful information about airborne spores that cause respiratory allergies such as rhinitis, asthma, and farmers’ lung disease. In building environments, spore counting and trapping can be used for detecting dry rot or other hidden mould. Although there are no acceptable levels of airborne fungal concentration in indoor environment, spore trapping and counting can also help in determining if occupants were potentially exposed to high levels of allergenic fungal spores.