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Sampling for Airborne Mould: When Should One Use Viable, Non-viable or Both Methods?

An air quality investigation may require determining airborne mould (spores and hyphal fragments) concentration. Air can either be sampled onto some growth media for culture analysis or on a sticky surface or a filter membrane for direct microscopic examination. It is sometimes debated as to whether one should take non-viable samples, viable samples or a combination of the two. Either method can be used without the other or both can be used together (at the same time) depending on the objectives of the investigation.

Due to lack of standardization some terminologies used in air sampling are technically incorrect or misleading. Let’s discuss these terms first.

Non-viable Air Samples
“Non-viable air samples” refer to samples that are taken on some sticky media or on a filter membrane or tape and subsequently examined directly under a microscope for enumeration and identification of mould spores and hyphal fragments without culturing. In other words, the samples are taken for analyses by direct microscopic examination (DME). Results are presented as a listing of various categories of moulds and the corresponding number of spores or hyphal fragments per cubic meter of air (Spores/m3). This term is technically inaccurate since viable and non-viable propagules are indistinguishable under the microscope and hence both are enumerated.

Viable Air Samples
“Viable air samples” refer to samples that are taken on some growth media and subsequently incubated for mould propagules (spores and/or hyphal fragments) to germinate and form colonies. The resulting colonies are then enumerated and/or transferred to other media for identification to genus or species. Results are presented as a listing of the recovered moulds and their corresponding number of colony forming units per cubic meter of air (CFU/m3). That is, the analysis of viable air samples involves culturing. The term is also technically inaccurate because some (sometimes most) of the propagules impacted on the growth media may not germinate not because they are not viable but because of the selectivity of the growth media used, competition from fast growing moulds or that some moulds can only grow on living hosts.

Spore traps
“Spore traps” is commonly used to refer to non-viable air samples. However, whether sampling is done for culture analysis with an RCS, Andersen or for DME with Air-O-Cell or other similar cassettes it involves spore trapping. “Spore traps” is therefore applicable to both viable and non-viable samples.

When should one use viable, non-viable or both sampling methods?

The easiest way to decide on this is first to define the objectives of air sampling, data required from sample analysis and the questions these data are meant to answer. The objective might be broad or very specific.

  • When to use non-viable sampling

If the objective of air sampling was to have an idea of how contaminated the air is, then the data required would be total counts. Non-viable samples would then be the best to take because counting includes both those propagules that can grow on laboratory media and those which cannot grow either because they are dead or would not grow on the selected media. Non-viable sampling may also be selected when the objective of air sampling is to determine the total counts for airborne spores prior to and after remediation to assess the effectiveness of remediation. In this case viable air samples would not be necessary.

  • When to use viable sampling

If the objective of air sampling was to find whether the air contains a specific species of mould e.g., Aspergillus fumigatus, then identification to species would be required. Since non-viable analysis would not distinguish A. fumigatus from other Aspergillus species and not even from Penicillium species and related genera, then sampling for viable analysis would be selected. For detecting a specific species, a selective media that would support the growth of the mould of interest would also be selected. If identification to species was required for a broad range of moulds, then media that support growth of a wide range of moulds would be selected.

  • When to use both non-viable and viable sampling

If the objective of air sampling was to determine the total airborne mould concentration and at the same time determine the proportion of viable propagules, then both sampling methods would be used. This would possibly be the case in hospitals where concern is not only the total concentration of airborne mould but also the viable species present.

Conclusion
These are not the only reasons why one may sample for non-viable, viable or both non-viable and viable analysis. It all depends on the objectives of air sampling, the data required and the questions these data are intended to answer. Read Interpreting Numerical Data of Viable Airborne Mould Samples and Guidelines for Interpreting Numerical Data of Non-viable (Spore Traps) and Viable Airborne Mould Samples.

To get hands-on experience on the application of these guidelines register for our Mould Training Seminars today!

Do you have a question on mould? Send it to us at Contact US.

Mold in Homes Doubles Risk of Asthma

Exposure to dampness and mold in homes as much as doubles the risk of asthma development in children, according to a study published today in the March issue of the peer-reviewed journal Environmental Health Perspectives (EHP). Researchers studied 1,984 Finnish children aged 1 to 7 years over a six-year period to see if they developed asthma. Data collection included a baseline survey administered in March 1991, as well as a follow-up survey in March 1997, asking questions about the child’s health, parents’ health, parent’s highest education level, and details of the child’s environment including exposure to environmental tobacco smoke and presence of feathery or furry pets.

The study focused particularly on four indicators or moisture or mold in homes, including mold odor, visible mold, visible moisture, and history of water damage. The presence of mold odor proved to be the only significant indicator of asthma development.

A a total of 138 children, or 7.2% of the study population, developed asthma during the study period. Having a parent with a history of allergies increased susceptibility in children. Mold odor increased the risk, the study found, independent of parents’ medical histories. In fact, children living in homes with mold odor during the initial study period were more than twice as likely to develop asthma in the following 6 years.

“These findings strengthen evidence that exposure to molds increases the risk of developing asthma in childhood,” says lead author Jouni Jaakkola, director of the University of Birmingham’s Institute for Occupational and Environmental Medicine. “They also show the importance of heredity-children of parents with asthma have a two-fold risk of asthma compared with children of nonasthmatic parents.”

Children who were exposed to moisture or mold in homes were also slightly more likely to be exposed to environmental tobacco smoke, to have feathery or furry pets, and to have parents with a lower education level. The study adds to the body of evidence linking asthma with exposure to cigarette smoke.

“This study is important for families everywhere,” says Dr. Jim Burkhart, science editor for EHP. “Anyone with young children in the home should be aware of the potentially harmful effects of long-term exposure to mold and this potential link to asthma in children.”

In addition to Jaakkola, contributing authors included Bing-Fang Hwang of the Environmental Epidemiology Unit at the University of Helsinki in Finland, and Niina Jaakkola of the Department of Health Care Administration at Diwan College of Management in Taiwan.

Funding sources for the research as reported by the authors included the Ministry of the Environment, the National Agency for Welfare and Health, the Medical Research Council of the Academy of Finland, and The Yrjö Jahnsson Foundation.

EHP is published by the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. EHP is an Open Access journal. More information is available online at http://www.ehponline.org.

Environmental Health Perspectives (NIEHS)
PO Box 12233, MD EC-15
Research Triangle Park, NC 27709-2233
USA
Phone 919-541-2359
niehs.nih.gov/drcpt/ehpb/home.htm

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Indoor Marijuana Growing Operations: Questions from Home Buyers

Use of residential houses for marijuana growing operations (simply referred to as grow ops) is increasing at an alarming rate. Buyers of houses across the country want to know if their potential properties were ever used for grow ops. The question I have been asked several times is, “if a house was renovated after these operations, is there a simple test that can be conducted to tell if the house was ever used for these operations?” Their major concern is mould. Unfortunately there is no mould test that I know of that can tell whether a property was ever used for marijuana growing. As a potential buyer my concern would not be whether the property was used for grow ops or not, unless the fact that it was ever used for grow ops would bother me or my family. I would be concerned about 2 things:

  1. Whether the property was structurally sound and met all the building codes. Grow ops may involve tempering with some of the building systems thus violating the building codes. Also, due to high humidity, mould growth may damage and weaken the wooden structure of the building.
  2. Whether there were abnormally high concentrations of hazardous contaminants such as pesticides, biological contaminants (mould, bacteria, mites, etc.), and other well known indoor contaminants.

If I am happy with 1 & 2 above, only other considerations would stop me from buying the property if I liked it.

Do you have a mould question? Send it to My Question.

Indoor Mould Infection: Can Mould Cause Bad Breath?

A person was exposed to mould in an office and they have developed bad breath which they didn’t have before. Could the bad breath be due to mould infection in their lungs? This is not a ‘yes/no’ question because whatever answer one gives should be supported with facts derived from documented evidence or tests conducted to such as person by a qualified person. The first answer that came to my mind was to say no. But then I realized there is still a lot that is not known about mould and their health effects. I was imagining that if the person had mould infection and the mould was actively growing in their lungs to the level of causing or producing odour, such a person would be critically ill. But my thinking is not based on any facts. It is just thinking.

The most well known lung mould infection is aspergillosis caused by some species of Aspergillus (hence the name aspergillosis). Moulds that are known to cause aspergillosis are Aspergillus fumigatus, Aspergillus flavus and occasionally Aspergillus terreus, Aspergillus nidulans, and Aspergillus niger. These moulds are widespread in the environment. They are found in soil, decomposing organic matter, household dust, building materials, and air. The people at risk of infection by these moulds are mainly those undergoing certain medical treatments that affect their immune system. In these people the disease is manifested as invasive pulmonary infection, usually with fever, cough, and chest pain. In healthy people, the disease is manifested as localized pulmonary infection. Aspergillus species also cause allergic reactions.

Do you have a mould question? Send it to us.

Indoor Moulds: The Penicillium Species

Penicillium species are very common moulds. About 200 species have been described. They are commonly called the blue or green moulds because they produce enormous quantities of greenish, bluish or yellowish spores which give them their characteristic colours. Their spores are found everywhere in the air and soil. They are the most common causes of spoilage of fruits and vegetables. For example, Penicillium italicum and Penicillium digitatum are common causes of rot of citrus fruits, while Penicillium expansum is known to spoil apples. Most species are active producer of toxins.

Mould identified as Penicillium chrysogenumThe most common Penicillium species in indoor environment is Penicillium chrysogenum. It is widespread and has a wide range of habitats. In indoor environment, it is extremely common on damp building materials, walls and wallpaper, floor, carpet mattress and upholstered furniture dust. It produces a number of toxins of moderate toxicity. It is allergenic and can infect immuno-compromised patients.

Do you have a question on mould? Send it 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. […]