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Sampling For Airborne Fungal Spores

Reasons for Conducting Air Sampling For Fungal Spores

Air sampling pump
Air sampling

Sampling for airborne fungal spores may be conducted for a number of reasons including assessing the air quality, detection of pathogenic organisms, epidemiological surveys and predictions, detection of mycotoxin producing fungi, or detection and measurement of exposure to allergenic fungi and actinomycetes. Before sampling for airborne fungal spores it’s important to have a clear objective and the data that would meet that objective. Some of these objectives require counting and identification of the airborne fungal particulates. A well calibrated pump is therefore required. The method of sampling, the equipment and the media are determined by the data required. For example if one is interested in species identification, then they would collect culturable air samples using an Andersen or RCS sampler.

Methods for Sampling for Airborne Fungal Spores

Culturable Air Samples

If the air was sampled by impaction onto a growth media, then the samples are first incubated at suitable temperature followed by counting and identification of resulting colonies (if any). A number of factors may affect the reliability of the colony counts data. These include the suitability of the agar media used for sampling, colony density, and presence of fast growing isolates. Some agar media are highly selective and therefore would not suitable when the objective was to determine the diversity of fungal species in the air. If the colony density is very high, then counting becomes difficult. In the presence of fast growing isolates, slow growing isolates are masked and hence difficult to count.

Non-culturable Air Samples

The second method of air sampling is where the air is impacted on inert medium, usually a filter membrane or adhesive-coated slide. The collection medium is then analyzed by transmitted light microscopy (popularly known as direct microscopic examination), typically at 600–1000 × magnification. A number of different collection devices may be used for spore trap sampling of which the most common are slit or circular impactors such as the Air-O-Cell®, Allergenco D, Micro 5, Cyclex D and other similar cassettes. Mixed cellulose ester membrane (MCEM) filters are also occasionally used.

Choose Your Spore Trap Analytical Labs Wisely

Identification of airborne fungal spores to species can only be accomplished by an experienced mycologist. Similarly, spore trap analysis requires considerable skill and experience on the part of the analyst to identify spores accurately, and to differentiate them from other airborne particulate. In most cases identification of airborne fungal spores by direct microscopic examination is limited to genus. In some cases identification of spores to specific genus is difficult. A good spore trap analyst requires several years of experience. A recent multi-laboratory comparative study of spore trap analyses found that only 75% of commercial accredited labs could consistently identify correctly Cladosporium spores and only 50% could identify Aspergillus/Penicillium-like spores consistently. The level of experience required for species identification or spore trap analysis cannot be attained in a short time, and it cannot easily be acquired by individuals lacking advanced training in mycology or plant pathology.

Mold & Bacteria Consulting Laboratories is accredited by CALA to the Internationally recognized ISO/IEC 17025:2005. 

MBL Is Accredited To ISO/IEC 17025:2005

Mold & Bacteria Consulting Laboratories is accredited by the Canadian Association for Laboratory Accreditation (CALA) to the internationally recognized ISO/IEC 17025:2005 standard. 

ISO/IEC 17025:2005 Standard

When a laboratory is accredited to ISO/IEC 17025:2005, the laboratory and its clients are assured that the lab has met defined standards for performance based on examination of a variety of criteria.  CALA assess participating laboratories to the ISO/IEC 17025 standard in accordance with the ISO/IEC 17011 standard. Granting of CALA accreditation requires a laboratory to successfully complete an initial site assessment and to maintain accreditation the laboratory must successfully complete a site visit a year following the initial visit and every two years thereafter.

Scope of Accreditation

MBL is accredited for specific analyses of fungi and bacteria in culturable and non-culturable air samples, water samples, surface samples, and bulk samples. We’re also accredited for Legionella testing. 

Canadian Accrediting Bodies

There are two Canadian based accrediting bodies, the Canadian Association for Laboratory Accreditation Inc.(CALA) and the Standards Council of Canada (SCC). Both of these accrediting bodies are recognized by the International Laboratory Accreditation Cooperation (ILAC) as equally competent accreditors of testing and/or calibration laboratories.

Is There a Difference Between Total Microbe Test and Total Coliform Test?

Question: Is there a difference between total microbe test and a total coliform test. What do the following results mean as far as safe drinking water is concerned, (5-10)(10-20)(400-500) (800-1000) Colony forming units(CFUs) of aerobic bacteria?

Thank you.

Answer: There is a difference between total microbes test and total coliform test. The former is a non-specific test for everything including the coliforms (if they are present). This test is commonly referred to as Heterotrophic Plate Count (HPC) or Total Aerobic Plate Count. HPC does not give an indication of the types of organisms present or their sources. The total coliform test is designed to detect bacteria belonging to the coliform group.

I am not sure whether the results above were CFUs per litre or per 100 mL. Assuming these were per 100 mL of water the first set of results would be considered insignificant provided coliforms were not present. The second two sets of results suggests the water is either not properly treated or is getting contaminated after treatment.

Below are the Health Canada Microbiological Guidelines for Canadian Drinking Water Quality.

Guidelines for microbiological parameters

Currently available detection methods do not allow for the routine analysis of all microorganisms that could be present in inadequately treated drinking water. Instead, microbiological quality is determined by testing drinking water for Escherichia coli, a bacterium that is always present in the intestines of humans and other animals and whose presence in drinking water would indicate faecal contamination of the water.

Bacteriological guidelines

Escherichia coli

The maximum acceptable concentration (MAC) of Escherichia coli in public, semi-public, and private drinking water systems is none detectable per 100 mL.

Testing for E. coli should be carried out in all drinking water systems. The number, frequency, and location of samples for E. coli testing will vary according to the type and size of the system and jurisdictional requirements.

Total coliforms

The MAC of total coliforms in water leaving a treatment plant in a public system and throughout semi-public and private supply systems is none detectable per 100 mL.

For distribution systems in public supplies where fewer than 10 samples are collected in a given sampling period, no sample should contain total coliform bacteria. In distribution systems where greater than 10 samples are collected in a given sampling period, no consecutive samples from the same site or not more than 10% of samples should show the presence of total coliform bacteria.

Testing for total coliforms should be carried out in all drinking water systems. The number, frequency, and location of samples for total coliform testing will vary according to the type and size of the system and jurisdictional requirements.

Heterotrophic plate count

No MAC is specified for heterotrophic plate count (HPC) bacteria in water supplied by public, semipublic, or private drinking water systems. Instead, increases in HPC concentrations above baseline levels are considered undesirable.

Emerging pathogens

No MAC for current or emerging bacterial waterborne pathogens has been established. Current bacterial waterborne pathogens include those that have been previously linked to gastrointestinal illness in human populations. Emerging bacterial waterborne pathogens include, but are not limited to, Legionella, Mycobacterium avium complex, Aeromonas hydrophila, and Helicobacter pylori.

Protozoa

Although Giardia and Cryptosporidium can be responsible for severe and, in some cases, fatal gastrointestinal illness, it is not possible to establish MACs for these protozoa in drinking water at this time. Routine methods available for the detection of cysts and oocysts suffer from low recovery rates and do not provide any information on their viability or human infectivity. Nevertheless, until better monitoring data and information on the viability and infectivity of cysts and oocysts present in drinking water are available, measures should be implemented to reduce the risk of illness as much as possible. If the presence of viable, human-infectious cysts or oocysts is known or suspected in source waters, or if Giardia or Cryptosporidium has been responsible for past waterborne outbreaks in a community, a treatment and distribution regime and a watershed or wellhead protection plan (where feasible) or other measures known to reduce the risk of illness should be implemented. Treatment technologies in place should achieve at least a 3-log reduction in and/or inactivation of cysts and oocysts, unless source water quality requires a greater log reduction and/or inactivation.

Viruses

Although enteric viruses can be responsible for severe and, in some cases, fatal illnesses, it is not possible to establish MACs for enteric viruses in drinking water at this time. Treatment technologies and watershed or wellhead protection measures known to reduce the risk of waterborne outbreaks should be implemented and maintained if source water is subject to faecal contamination or if enteric viruses have been responsible for past waterborne outbreaks. Where treatment is required, treatment technologies should achieve at least a 4-log reduction and/or inactivation of viruses.

For more details on Canadian Guidelines for drinking water click Guidelines for Canadian Drinking Water Quality.

What Is Deemed Acceptable Indoor Airborne Mold Spore Levels In Ontario?

Question: Is there any government or industry standard as to what is deemed an acceptable indoor airborne mold spore levels in Ontario? The electrical inspector refuses to come on our property even though we have had several air test performed. The qualified tester says we have samples of mold but found them to be acceptable. I was hoping for some clarity on this matter.

Answer: Currently there is no government or industry standard as to what is deemed acceptable indoor airborne mold spore levels. However, it’s generally agreed that mold in indoor environments is a health hazard. However, the higher the airborne mold spore levels in a building the higher the health risk. In 2007 Health Canada published the Residential Indoor Air Quality Guidelines: Moulds.

This is what Health Canada’s Residential Indoor Air Quality Guidelines say about exposure limits:

Health Canada considers that mold growth in residential buildings may pose a health hazard.
Health risks depend on exposure and, for asthma symptoms, on allergic sensitization. However, the
large number of mold species and strains growing in buildings and the large inter-individual variability
in human response to mold exposure preclude the derivation of exposure limits. Therefore, Health Canada recommends:

  • to control humidity and diligently repair any water damage in residences to prevent mold growth; and
  • to clean thoroughly any visible or concealed mold growing in residential buildings.

These recommendations apply regardless of the mold species found to be growing in the building.

Further, in the absence of exposure limits, results from tests for the presence of fungi in air cannot be used to assess risks to the health of building occupants.

So currently there is no acceptable or unacceptable indoor airborne mold Spore levels in Ontario.

What’s The Chance Of Getting A Positive Result For Legionella Tests?

Legionella Tests Question: Hi, I am a student working on an environmental research project on Legionella tests. I’m considering to have some water sample tested for Legionella species especially Legionella pneumophila. From your experience, what is the chance of getting a positive result for the Legionella tests? How much does the tests cost, for both PCR and culturable methods?

Thank you for your attention.

Answer: Legionella species are ubiquitous in natural and artificial water environments worldwide. They survive in a wide range of environmental conditions. Chances of getting positive results for Legionella tests from water depends on the following:

  • The Source of water. Legionella species thrive at temperatures between 20 °C and 50 °C. Therefore, the bacteria are rarely found in municipal water supplies. They tend to colonize warm water systems and point-of-use devices, particularly hot-water systems.
  • Isolation method. Legionella species are usually a very minor component of the total bacterial population in environmental samples and are rarely present in high numbers. Thus, it’s possible to get negative Legionella tests results if the bacteria in the sample were not concentrated prior to analysis.
  • Concentration: Legionella may be present in concentrations too low to be detected using culture methods.
Legionella tests
Legionella test

The cost of Legionella tests depends on the level of identification required. There are many labs that carry out Legionella tests but some if not most are not accredited.  To minimize false-positive results for Legionella tests, it’s important to use a qualified accredited laboratory.

Mold & Bacteria Consulting Laboratories (MBL) performs several Legionella tests every year. Currently we use cultural methods for Legionella identification. We’re accredited by the Canadian Association for Laboratory Accreditation (CALA) to ISO/IEC 17025:2005. MBL is also certified in the analysis of Legionella bacteria by the prestigious Environmental Legionella Isolation Techniques Evaluation (ELITE) program of the US Centers for Disease Control and Prevention (CDC).

For pricing please call 905-290-9101 in Ontario.

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