MOLD CULTURE TEST KIT VALIDITY - CONTENTS: Are indoor air quality "mold test kits" that rely on culture plates accurate as a building screening test for mold contamination? Advice on how to test or screen for problem mold indoors
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Mold culture test kit accuracy:
Are culture plates a reliable method to screen buildings for indoor mold contamination? This article discusses building mold tests that rely only on settlement plates or swabs to find toxic mold in buildings. Before you buy any "mold home test kit" for mold you
should read this article.
This article explains the limited accuracy of mold cultures when used as "mold test kits" to examine
indoor air quality as an investigation methodology in searching for possible causes of respiratory illness, asthma, immune system disorders, rashes, skin
disease, psychological and neurological disorders, eye infections, or other symptoms that may have a physiological and environmental component.
Problems With Relying on cultured mold samples to evaluate a building
Why don't we use readily-available mass-marketed cultures, settlement plates, and swab kits such as those available at the local hardware store?
While all "mold tests" and "mold test kits" or mold sampling methods have their limitations, the usefulness of mold culture plates as a general screen for harmful indoor mold contamination is particularly limited.
OPINION: because most mold genera / species simply will not grow in any culture. So even if the culture does successfully grow mold we don't know if this accurately represents what mold contaminants are in the building tested.
The underlying methodology of this test may be seriously flawed if you're relying on the results of culturing
to characterize just what problematic fungal spores are present in a building.
Mold cultures, typically taken using settlement plates, Anderson-type samplers, and sterile swabs, can be quite unreliable as indicators of what's really present
in an indoor environment. This is especially true if the test does not detect a mold problem (one may be present but was not detected by this method) and it might be true even if the test does seem to detect a problem as it may detect molds other than the largest or most serious mold contamination reservoir that's present.
As another test limitation example, a dead spore in the air may be toxic but may not grow at all in a culture medium.
In addition, variations in building indoor air movement, activity, humidity, temperature, and other conditions causes an enormous variation in the level in air of all sorts of indoor particles. I have found as much as four orders of magnitude in the level of airborne mold spores as these conditions in buildings were changed.
And individual mold spores, varying by size, mass, toxicity, and preference for mold culture, find very different rates of first settlement out of the air onto any building surface (including a culture plate) and second rates of growing within any given culture medium (including a range of growth from abundant to zero).
In our mold culture photo at above right you see a "home test kit" for mold collected in a Washington DC apartment in the Watergate. Apparently there are about seven different mold genera/species appearing on this "overgrown" culture plate.
But the fastest growing molds (those who most like the media) will of course overgrow and hide other mold spores that may have landed on the media. And then, heavier larger spores tend to settle out of air sooner than smaller lighter spores. So the culture plate may over-represent heavy large molds compared with the actual molds present in the building.
Use of cultures as building screens for the presence or absence problematic mold is unreliable - only 10% of all molds of any genera will grow on any culture
under any circumstances, so a mold culture screening test for mold is 90% wrong at the outset. More so if one considers that certain molds that can be grown in culture
only respond to specific culture media.
Even if a mold is grown on a culture, given these constraints one cannot reliably infer that the mold grown is the problem
material in a building. Therefore no screening test by air or culture is an adequate substitute for nor superior to the value of a careful visual inspection by an experienced inspector who knows where mold is likely to grow and what it looks like on or in building surfaces and cavities.
Other serious flaws include inconsistent presence of problematic particles in building air, variations in particle settling rate out of air, variations in
growth rates on different media of different mold species (fast growing spore A over-grows and hides the presence of slow growing spore B) and the fact that
some problematic spores which could be hazardous to building occupants simply do not grow at all in the culture medium. There is indeed a valid place for
cultures (air or swab) in the arsenal of building investigation tools (cross check on visual inspection and bulk sampling, cross check on clearance
inspection and sampling, and elaboration of dormant particles).
Culture methods for fungal spore determination are an important tool, but these methods should not be relied-upon as the principal means for determining
what problematic particles are in indoor air.
Relying on over-the-counter home test kits for mold to evaluate a building
Home test kits for mold are inexpensive, easily available, and easy to use. Therefore we
wish we could say they could be an OK place to start, but we don't think this is the most accurate approach to screening a building for mold.
recent field experiment we used an over-the-counter "mold test kit" according to its instructions while we also performed a professional inspection
of the building.
Among problems which our inspection discovered in the building the settlement-plate culture "toxic mold test kit" successfully found
an Aspergillus sp. presence. It also found some nice Alternaria sp. spores, as well as the usual other collection of common Cladosporium species found in air.
What the mold test kit failed to find was what was probably making the occupants in the building sick. Our visual inspection identified various
area of mold on surfaces and in the building cavities.
We collected bulk (tape) samples (as well as vacuum samples (such as vacuum samples of fiberglass building insulation)
and we also collected some air samples used as a cross-check screen).
A strategic examination of these samples identified a very extensive Stachybotrys
chartarum infection in the building, Penicillium, and an extensive Chaetomium globosum colony as well as the Aspergillus and the less troublesome Alternaria and its buddies.
The first two mold species are toxic, the last, allergenic. They were totally missed by the "test kit." Why did the home test kit for mold fail to find the actual problem in the building?
In addition to our bulk samples (which found the mold missed by the "home test kit") we also used two different types of air sampling
machines as well as pulling some vacuum samples of suspect carpeting in an area which looked pretty clean.
Remarkably, our air samples confirmed the Stachybotrys chartarum presence, a spore not so easily found in air, despite the fact that we did nothing more than walk across a carpeted room during the
Mold spores may appear or fail to appear in an air test or "spore trap" for mold because of significant variations in particle disturbance during activity in the building, though there is a huge number of
other factors which affect air and particle movement inside.
In this building the owner had begun a do-it-yourself demolition and repair of a water-damaged bathroom. Extensive mold contamination was on the exposed side of bathroom drywall and more extensive mold was growing on the cavity side of these walls.
As the owner used a hammer and hatchet to smash and remove drywall, considerable levels of airborne mold were produced - a condition probably more hazardous to the occupants
than when the mold was simply growing on and in surfaces and cavities.
We are often able to spot a building where there has been a previous demolition of moldy materials by examining
dust from remote surfaces. The actual exposure level of the building occupants to this mold is not something one can immediately infer from finding leftover traces in a building, but if professional
containment and remediation measures were not followed, there is at least a risk that for a time the occupants may have been breathing some pretty moldy air.
In the case described here, the owner who performed the demolition developed a rather ugly skin rash that appeared to be mold-related, and which abated after a combination of treatment and some proper housecleaning.
Personal Field Experience Finds Wide Variation of Airborne Mold Spores over Short Time Intervals
Really? While Pasanen (1991) found that
The relative humidity of air had no direct influence on the growth of fungi.
By repeated measurements of airborne mold levels of a species of Aspergillus sp. at the same location on successive days during a process of dehumidification in a moldy library basement, I found that the level of airborne Aspergillus sp. spores ranged from barely detected (counts in the tens of spores per liter of air) to very high (tens of thousands of spores per liter of air) as the indoor relative humidity fell.
I posit that the very thick mold visible on books in this historically very damp space consisted in, among others, Aspergillus sp. that began to release its spores at dramatically increased levels as the area began to dry.
Most mold species have not been named nor studied
Of over 5 million mold genera/species currently estimated to be growing away on earth, less than 100,000 individuals have been named and studied at all.
Less than two percent of all molds have been studied. (Blackwell 2011)
And mold is everywhere, even inside the U.S. Laboratory module of the International Space Station, (Vesper 2008).
Happily for people cleaning up a mold problem or diagnosing a medical or allergenic mold problem, we can do a little better.
There are probably about 200 common mold genera/species that are often found indoors growing in or on building materials.
While there are many others who may make an occasional appearance, even as a large area of mold growth, most often it's one of these 200 or so molds.
Surface Dust & Tape Sampling: An Alternative to Mold Cultures & Speciation for Building Screening Tests
We prefer collecting physical samples of representative settled dust as that will collect both viable and non-viable mold spores. We cannot perform accurate quantitative analysis of a surface or tape sample but we can recognize when there is an unusual level of a particular problem particle, mold or otherwise.
See TAPE SAMPLING PROCEDURES
Keep in mind that except for special circumstances (medical need, need to prove that other building dust is due to improper dust containment during a mold remediation) we do not need to know the mold's name to clean it up. Except for cosmetic (harmless) black mold that we sometimes find on framing lumber, we want the indoor mold to be cleaned-up (removed) and we want the cause for its growth to be corrected.
See also COSMETIC MOLD, RECOGNIZE
Research on Accuracy of Mold Culture Testing for Indoor Mold Contamination
Blackwell, Meredith. "The Fungi: 1, 2, 3… 5.1 million species?." American journal of botany 98, no. 3 (2011): 426-438.
Abstract excerpt: Premise of the study: Fungi are major decomposers in certain ecosystems and essential associates of many organisms. They provide enzymes and drugs and serve as experimental organisms. In 1991, a landmark paper estimated that there are 1.5 million fungi on the Earth. Because only 70000 fungi had been described at that time, the estimate has been the impetus to search for previously unknown fungi. Fungal habitats include soil, water, and organisms that may harbor large numbers of understudied fungi, estimated to outnumber plants by at least 6 to 1. More recent estimates based on high-throughput sequencing methods suggest that as many as 5.1 million fungal species exist.
... Fungi are essential to the survival of many groups of organisms with which they form associations. They also attract attention as predators of invertebrate animals, pathogens of potatoes and rice and humans and bats, killers of frogs and crayfish, producers of secondary metabolites to lower cholesterol, and subjects of prize-winning research. Molecular tools in use and under development can be used to discover the world’s unknown fungi in less than 1000 years predicted at current new species acquisition rates.
Burge, Harriet A., William R. Solomon, and Michael L. Muilenberg. "Evaluation of indoor plantings as allergen exposure sources." Journal of Allergy and Clinical Immunology 70, no. 2 (1982): 101-108.
Buttner, Mark P., and LINDA D. Stetzenbach. "Monitoring airborne fungal spores in an experimental indoor environment to evaluate sampling methods and the effects of human activity on air sampling." Applied and environmental microbiology 59, no. 1 (1993): 219-226.
Abstrac: Aerobiological monitoring was conducted in an experimental room to aid in the development of standardized sampling protocols for airborne microorganisms in the indoor environment. The objectives of this research were to evaluate the relative efficiencies of selected sampling methods for the retrieval of airborne fungal spores and to determine the effect of human activity on air sampling.
Dry aerosols containing known concentrations of Penicillium chrysogenum spores were generated, and air samples were taken by using Andersen six-stage, Surface Air System, Burkard, and depositional samplers.
The Andersen and Burkard samplers retrieved the highest numbers of spores compared with the measurement standard, an aerodynamic particle sizer located inside the room. Data from paired samplers demonstrated that the Andersen sampler had the highest levels of sensitivity and repeatability. With a carpet as the source of P. chrysogenum spores, the effects of human activity (walking or vacuuming near the sampling site) on air sampling were also examined.
Air samples were taken under undisturbed conditions and after human activity in the room. Human activity resulted in retrieval of significantly higher concentrations of airborne spores. Surface sampling of the carpet revealed moderate to heavy contamination despite relatively low airborne counts. Therefore, in certain situations, air sampling without concomitant surface sampling may not adequately reflect the level of microbial contamination in indoor environments.
Haines, J., Dr. [personal communication to DJF] 11/17/2016 An American Journal of Botany article in 2011 gives a new estimate of 5.1 million fungi. But the Dictionary of Fungi 2008 reveals that a mere 97,330 species have been described. I put that discrepancy on the NSF funding shift from taxonomy to experimental decades ago.
Pasanen, A-L., P. Kalliokoski, P. Pasanen, M. J. Jantunen, and A. Nevalainen. "Laboratory studies on the relationship between fungal growth and atmospheric temperature and humidity." Environment International 17, no. 4 (1991): 225-228.
Abstract: The effect of air temperature (4–30°C) and relative humidity (RH 11–96%) on the growth of two common fungi Aspergillus fumigatus and Penicillium sp. was studied in the laboratory. A short period of favorable conditions was sufficient to start fungal growth. Temperature was not a limiting factor for fungal growth on building materials, because fungi grew at even below 10°C.
The relative humidity of air had no direct influence on the growth of fungi. Fungi may grow at very low levels of air humidity if water is available on the surface. Thus, repeated or persistent moisture condensation or water leakage is sufficient for fungal germination and growth on building materials.
Sayer, William J., Dudley B. Shean, and Jamshid Ghosseiri. "Estimation of airborne fungal flora by the Andersen sampler versus the gravity settling culture plate: I. Isolation frequency and numbers of colonies." Journal of Allergy 44, no. 4 (1969): 214-227.
Abstract: The gravity settling culture (GSC) plate and the sequential impaction cascade sieve volumetric air (SICSVA) sampler devised by Andersen were critically compared in the estimation of airborne fungal flora. One hundred twenty-seven side-by-side simultaneous 15 minute samples were obtained on Mehrlich's medium in Northern California. The SICSVA sampler collected 25 fungal types totaling 14,300 colonies, and the adjacent GSC plates displayed 18 genera in 1,091 colonies.
Statistically significant differences in total colonies and frequency of isolation were noted for Penicillium, Alternaria, Aspergillus, Gliocladium, Pullularia, Rhizopus, Saccharomyces, Stemphilium, Ustilago zeae, and other (unidentified) fungi. The capability of the SICSVA sampler to isolate volumetrically in a reproducible fashion numbers of airborne fungal spores was demonstrated.
It is suggested that these colonies can be logically grouped into a fraction that generally would lodge in the upper respiratory tract and another fraction which, because of the small spore sizes, would largely be capable of lung penetrance. Both methods demonstrated a capacity to produce falsely negative data, but this was especially true for the GSC plate. The GSC plate method cannot be endorsed for the quantitative evaluation of airborne fungal spores.
Solomon, William R., and H. A. Burge. "Allergens and pathogens." In Indoor Air Quality, pp. 174-175. Boca Raton, Fla.: CRC Press, 1984.
Solomon, William R. "A volumetric study of winter fungus prevalence in the air of midwestern homes." Journal of Allergy and Clinical Immunology 57, no. 1 (1976): 46-55.
Abstract: Volumetric recoveries of airborne, mesophilic microfungi were made during winter months at three specific points in 150 single-family dwellings in southeastern Michigan. Mean levels of total isolates/m3 comprised a range of from less than 10 to over 20,000, although concurrent outdoor levels never exceeded 230/m3. Form species of Penicillium, Aspergillus, Cladosporium, and Rhodotorula as well as non-pigmented yeasts were the types encountered most widely indoors.
Certain homes showed high recoveries of other types, including Cephalosporium, Sporobolomyces, Verticillium, and Sporothrix form species. A positive association between indoor fungus prevalence and bedroom relative humidity was strongly suggested, and high levels were observed in well-humidified homes despite the presence of electrostatic air cleaners.
The data indicate characteristic patterns of (winter) air spora in specific homes and suggest that humidifying devices may serve as dispersion sources in addition to their permissive role in facilitating fungus growth.
Solomon, William R. "Assessing fungus prevalence in domestic interiors." Journal of allergy and clinical immunology 56, no. 3 (1975): 235-242.
Abstract: Single-plate, Andersen sampler collections of mesophilic imperfect fungi were made at three points in and immediately outside a series of midwestern homes. During frost-free periods, emanations of dark-spored form genera predominated at both points with indoor levels averaging 25% of those in outside air. At these times, volumetric recoveries and those by 30-min exposure of open culture plates have correlated tenuously (r = 0.29) in bedroom air of 20 homes.
During winter, form species of Penicillium, Aspergillus, Oospora, Sporothrix, yeasts, etc. predominated indoors, with levels exceeding 1,000 particles/M3 noted in over 18% of homes; outdoor concentrations never exceeded 230 particles/M3. Comparisons of volumetric and open-plate recoveries from 50 homes during winter have revealed an almost random relationship (r = 0.06).
These findings reflect the ease with which outdoor spore clouds may penetrate structures and obscure evidence of internal fungus sources. The data also imply that, because of size-related undersampling, open plates often seriously misrepresent prevalence levels and occasionally can exclude abundant types from recovery. The fungus flora of enclosed spaces merits further critical study by volumetric techniques of calculable efficiency in a setting that minimizes contamination from without.
Vesper, Stephen J., Wing Wong, C. Mike Kuo, and Duane L. Pierson. "Mold species in dust from the International Space Station identified and quantified by mold-specific quantitative PCR." Research in microbiology 159, no. 6 (2008): 432-435.
Abstract: Dust was collected over a period of several weeks in 2007 from HEPA filters in the U.S. Laboratory Module of the International Space Station (ISS). The dust was returned on the Space Shuttle Atlantis, mixed, sieved and the DNA was extracted. Using a DNA-based method called mold-specific quantitative PCR (MSQPCR), 39 molds were measured in the dust. Potential opportunistic pathogens Aspergillus flavus and Aspergillus niger and potential moderate toxin producers Penicillium chrysogenum and Penicillium brevicompactum were noteworthy. No cells of the potential opportunistic pathogens Aspergillus fumigatus, Aspergillus terreus, Fusarium solani or Candida albicans were detected.
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Where Can I Buy Mold Test Kits for do-it-yourself testing?
I will be calling one of the testing inspectors that you list at MOLD & ENVIRONMENTAL INSPECTORS . In addition, is there any device I can purchase which would allow me to make an independent test?
- Thanks J.O.
Do-it-yourself mold tests are widely available at hardware stores and building suppliers as well as online. The tests usually fall into one of two groups:
Adhesive tape collection surface particles: particle or surface debris or suspected mold on a surface - see http://www.inspectapedia.com/sickhouse/Adhesive_Tape_Particle_Test.php for detailed procedures on how this test sort is used (to avoid any conflict of interest, or even an apparent conflict, don't sent your sample to us)
Mold culture kits: a plastic petri dish of growth medium is exposed to air, re-sealed, and you or the lab gets to see what grows. Since 95% of molds won't grow on any culture, this is an unreliable way to screen a building for problem mold, though cultures do have widespread and valid use in the lab. MOLD CULTURE TEST KIT VALIDITY has details.
And frankly, for serious mold or water damage investigation cases, using any of these "mold test" methods to produce useful results needs to be combined with an expert building inspection and case history as well as occupant interview.
The reliance on mold "tests" without a thorough, expert onsite inspection, history taking, etc. is simply unjustified. And that may be why whomever you paid to do these tests can't be more helpful to you.
Properly, and providing an onsite investigation was justified in the first place (see MOLD / ENVIRONMENTAL EXPERT, HIRE ?- when to hire a mold expert)
then the person who inspected the site, took its history, understands the building, its occupants, its environment, should be able to make a meaningful interpretation of various tests done in the building that supplement the more thorough site investigation.
Relying on a mold "test" is profitable for the test company and lab but by itself, can be misleading, especially where low numbers or low mold-level findings were the results found in the test. Even high mold level findings can be misleading as the test may not have detected the most problematic mold present.
All of that said, you can hire someone to read and interpret and discuss your report, and then to suggest further investigative steps that could be helpful. (See MOLD & ENVIRONMENTAL INSPECTORS)
Bottom line: in our experience and opinion, relying on mold tests alone to diagnose a building is a risky proposition.
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Questions & answers or comments about buying & using do-it-yourself mold test kits based on culture plates..
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Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon) - The Atlas of Clinical Fungi is also available on CD ROM
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention in Home Vegetable Gardens,"
Department of Plant Microbiology and Pathology,
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
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