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Mold Exposure Standards
Levels of allergenic or toxic mold & how much mold means a problem?
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• Mold exposure limits, mold exposure standards, definitions of mold contamination levels
• Variation in mold toxicity
• Mold exposure standards - various U.S. and other Countries standards for allowable mold exposure
• Effects of mycotoxins, toxicity of Stachybotrys, Penicillium, Aspergillus
• How toxic is black mold? which black molds are harmless?

What mold spore levels indicate contamination in buildings ?

Mold spore counts and mold culture results are not reliable alone for evaluating a mold problem

Warning: fungal spore counts in indoor air, whether "viable" or "non-viable" counts, as well as swab and culture methods to identify just what mold is present in a building are questionable methods to characterize the presence or absence of a mold problem indoors.

From experience carefully inspecting many buildings for mold problems and simultaneously collecting many types of field samples and examining them in our lab, our view is that anyone who makes one or a few indoor air measurements or relies on culture plates or swabs to "characterize" the mold level and mold species in a building is risking being way off target, particularly if the "test results" show low numbers.

This document provides information about airborne mold spore counts, surface density, and other measures of the exposure level of allergenic, infectious, and levels of toxic mold in residential buildings: At what level is allergenic or toxic mold considered a problem in buildings? How do we obtain an accurate and meaningful measurement of mold exposure indoors? Also see MOLD RELATED ILLNESS GUIDE and MOLD RELATED ILLNESS SYMPTOMS.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Reasons Simple Airborne Mold Counts Alone Are Not Good Indicators of Risk

"Mold Levels" warning: single number "mold levels" are unreliable as a measure of health risk in buildings for several reasons including at least the following:

1. Particle levels vary: the actual level of indoor particles in air varies by several orders of magnitude over very short few-minute intervals, making reliance on any single measurement questionable, particularly if the measurement does not show evidence of a problem. Simple mechanical disturbance like turning on or off a fan can completely change individual measurement results. Short term measurements are therefore inaccurate.
2. Human sensitivity varies: because of wide variation in individual human reaction and risk to mold, variation in allergenicity, pathogenicity, and toxicity among mold genera and individual species, and even additional variation in these levels depending on specific environmental conditions such as the substrate upon which a mold is growing (its food), quantitative risk-levels are better used as an overall indication of building cleanliness before and after a mold cleanup, and not as an absolute level of risk to building occupants.
3. Particle toxicity varies: There is very wide variance among the toxicity of individual mold species, ranging from none to probably highly toxic, pathogenic, or even carcinogenic.
4. Spore size or mass varies widely from less than 1 u to over 200u, so a large spore contains potentially more harmful material than a small spore of the same "toxicity," making a "count" that does not identify the particle and particle size ambiguous
5. Mold spore toxicity vary, even within an individual species, depending on what substrate the species is growing on in a particular instance, e.g. wood vs. drywall.
6. Viable vs. non-viable "spore counts" vary in significance: procedures that use cultures to identify "viable" spores may omit high levels of non-viable spores which nonetheless remain highly toxic. Methods that rely on culturing have a high risk of identifying a mold which is present but is not the dominant or even the most problematic mold in the building, while completely failing to disclose a problem mold which is present but which simply does not grow in the culture media used, or is overgrown by another species in that media. For more details see Mold Spore Counts: are indoor fungal spore counts valid? for further explanation.

See ACCURACY OF AIRBORNE MOLD SPORE COUNTS for more details about these issues. That said, here is a sampling of some indoor air mold spore exposure level criteria and comments

Contamination levels of non-specific allergenic, pathogenic, or toxic fungal spores

1. Baxter et als: Mold contamination is considered present in a building when the total mold spore concentration per cubic meter is above 10,000. Our own field and lab experience confirms this view. However in special cases, even low quantitative levels of certain particles or particle types (such as Pen/Asp spore chains in an un-treated building) may be diagnostic and may indicate a hidden mold reservoir that at least merits further investigation.

2. The National Allergy Bureau, reporting the NAB SCALE (National Allergy Bureau) of mold and pollen counts, considers mold counts in outdoor air of 0-6499 spores per cubic meter of air as low, to 6500 to 12,999 spores per cubic meter of air as moderate, to 13,000 to 49,999 spores per cubic meter of air as high, and above 50,000 as very high. At "high" levels most individuals with any sensitivity will experience symptoms. AAAAI also provides absent, low, moderate, high, and very-high level level definitions for grass, tree, and weed pollen grains counted per cubic meter of outdoor air.

Acceptable levels for individual species vary since species toxicity varies widely as does spore size, weight, and other features which affect risk to building occupants. E.g. Aspergillus/Penicillium in a "clean" residential building study was at a mean of 230, in buildings known to have a moisture or flooding problem it was at 2235 and in mold contaminated buildings the figure was 36,037.

AAAAI provides an important qualification about mold and pollen counts as reported by that agency which we quote just below:

"These mold levels were determined based on outdoor exposure to natural occurring spores in the environment and should not be applied to indoor exposure which may represent an entirely different spectrum of spore types.

These definitions would allow comparison between sites across the country. They are based on ecological measurements, not health effects. However, assuming dose/response relationships are the same across the country, the definitions are probably more appropriate than a definition based on local numbers. This does mean that, for some stations, some categories will never be high." - AAAAI.

3. The University of Minnesota data presents this table for mold levels expressed in colony forming units per gram. WARNING: mold spores may be not viable (dead), wrong culture media may be used, or one species can overgrow another, etc. - so don't produce any colonies, but may be toxic if inhaled (such as some species of Penicillium). So we would not rely on culture data. But here it is:

Concentration Qualitative Assessment of Mold Contamination Levels

Colony Forming Units/gram - cultured mold samples as indicators of mold level in buildings

• less than 10,000 CFUs of mold per gram in a culture sample plate = low mold contamination level
• 10,000 to 100,000 CFUs of mold per gram in a culture sample plate = medium mold contamination level
• 100,000 to 1,000,000 CFUs of mold per gram in a culture sample plate = medium to heavy mold contamination level
• > 1,000,000 CFUs of mold per gram in a culture sample plate = heavy

WARNING: about interpreting mold cultures: this is a very very inaccurate method for screening buildings for the level of mold contamination for many reasons, including that only 10% of all molds will grow on any culture under any condition. So this approach begins as 90% "wrong".

Other mold level variables include the differences in settlement rate out of air as a function of particle size and weight, proximity to a mold contamination reservoir, and the problem that a serious toxic mold may be overgrown (if it grows at all) in the culture by a second mold species which hides the first one. See INDOOR AIR QUALITY METHODS COMPARED for details of these issues.

4.The American Conference of Government Industrial Hygienists (ACGIH) stated (Harriet Burge et. al) stated in 1987 that indoor mold levels are generally less than 1/3 the outdoor level and that when indoor mold is at more than this level remedial action should betaken to find the source of the elevated counts and to clean it up.

WARNING: this is an inaccurate and unreliable method for screening buildings for mold for many reasons, including:

• the airborne level of particles varies enormously moment to moment - opening a door or closing a window, waving a notebook at a table, or walking across a carpet completely change the particle level
• at most of our detailed investigations we find that unless all of the building windows are open and wind is blowing through the building, the air exchange rate between indoor and outdoor air confounds a comparison with outdoor air
• outdoor air particle levels and mold levels vary enormously as a function of weather conditions; with snow cover there is little airborne mold outdoors; after a rain or at certain other weather conditions there can be an explosion in the level of outdoor spores, confounding the indoor measurement
• nearly all indoor/outdoor airborne mold level comparisons fail to focus on differences in genera and species between indoors and outside; even relatively low indoor airborne or dust-borne mold levels might indicate a problem in the building, depending on just what is identified in the sample
• indoor and outdoor basidiomycetes are often mistaken for and compared with Penicillium/Aspergillus levels - a serious error

See INDOOR AIR QUALITY METHODS COMPARED for details of these issues.

5. Other proposals for Mold Exposure Standards have included a limit of 500 CFU/ of mold spores per cubic meter of air in winter indoors in sub arctic climates (Reponen et al.1990). CFU means "colony forming units" of mold.

We suspect that focusing only on "colony-forming-units" (that is, viable mold that will grow) is not a very reliable way to check out a building. That's because

• 90% of mold species will not grow on culture media
• Even if a particular mold species will grow on culture media, it may be overgrown and thus under-represented by a another mold that was present in the same sample at a much lower rate but which happens to like the culture media better than the more frequent spore or even a more toxic mold spore
• Spores settle out of air at very different rates depending on spore size and mass. Just as some very small snakes are more venomous and potentially dangerous than some very big snakes, size, and thus settlement rate out of air, and thus occurrence on a mold culture settlement plate, does not accurately represent what building occupants are breathing.

At MOLD CULTURE PLATE TEST ERRORS we have cited the range of errors and limitations of using cultures to check for viable mold, and we point out that depending on the particular mold genera and species present in a building, even non-viable mold may be allergenic or toxic. That is why experts in mold testing and remediation advise that the object is to remove mold or clean up mold in a moldy indoor environment, rather than attempting to "kill" mold indoors.

Also see INDOOR AIR QUALITY METHODS COMPARED for details of these issues.

Mold Exposure Levels - Sources of Variation in Mold Toxicity - a warning about single numbers

Single number "mold levels" are very unreliable as a measure of health risk in buildings for several reasons including at least the following:

Particle levels vary widely over short time periods: The actual level of indoor particles in air varies by several orders of magnitude over very short few-minute intervals, making reliance on any single measurement questionable, particularly if the measurement does not show evidence of a problem.

The absolute level of airborne particles in buildings varies enormously, possibly by a factor of hundreds to thousands, over intervals as short as a few minutes. Simple mechanical disturbance like turning on or off a fan can completely change individual measurement results. Short term measurements are therefore inaccurate and even longer term measurements are inaccurate if they do not consider the in-use variations in dust disturbance in a building.

Human sensitivity to mold varies: Individual susceptibility to mold/mycotoxin/aflatoxin-related or allergy-related illness varies widely and human exposure is complex because people move among a variety of environments

Finally, because of wide variation in individual human reaction and risk to mold, variation in allergenicity, pathogenicity, and toxicity among mold genera and individual species, and even additional variation in these levels depending on specific environmental conditions such as the substrate upon which a mold is growing (its food), quantitative risk-levels are better used as an overall indication of building cleanliness before and after a mold cleanup, and not as an absolute level of risk to building occupants.

Mold Spore - Particle toxicity varies for many reasons

There is very wide variance among the toxicity of individual mold species, ranging from none to probably highly toxic, pathogenic, or even carcinogenic

Mold Spore size varies widely from less than 1 u to over 200u, so a large spore contains potentially more harmful material than a small spore of the same "toxicity," making a "count" that does not identify the particle and particle size ambiguous

Mold spore toxicity may vary, even within an individual species, depending on what substrate the species is growing on in a particular instance, e.g. wood vs. drywall.

Viable vs. non-viable toxic mold "spore counts"

These mold spores vary in significance: procedures that use cultures to identify "viable" spores may omit high levels of non-viable spores which nonetheless remain highly toxic. Methods that rely on culturing have a high risk of identifying a mold which is present but is not the dominant or even the most problematic mold in the building. For more details see Mold Spore Counts: are indoor fungal spore counts valid? for further explanation.

Other U.S. & World Government Mold Exposure Standards

For the standards and references below, numbers are spores per cubic meter of air and do not consider individual or viable/non-viable or genera-species specific levels. There is a serious limitation of the standards since the spores of different genera and species vary widely in total size, mass, and toxicity.

The level of airborne particles indoors varies enormously, by orders of magnitude, from moment to moment, making the strict interpretation of any "indoor air mold test" unreliable, as we discuss at ACCURACY OF AIRBORNE MOLD SPORE COUNTS. -DF

• Australian Mold Standards: See Australian Mould Guideline AMG-2005-1 (PDF)
• Brazil Mold Standards: See Occurrence of airborne bacteria and fungi in bayside offices in Rio de Janeiro, Brazil, by Brickus, L. S. R., Siqueira, L. F. G., Neto, F. R. D. and Cardoso, J. N., 1998)
• Canadian Mold Standards: see this Canadian Mould Guidelines Document: Hazard Alert on Mould in Workplace, 2000, Also see:
  • Mould Guidelines for the Canadian Construction Industry
  • Fungal Contamination in Buildings: Health Effects & Investigation Methods, Health Canada, Minister of Health
  • Canadian Mortgage and Housing Corporation - see Canadian National Toxic Mold Centre, and also see Moldy Houses: Why They Are and Why We Care & Additional Analysis of Wallaceburg Data: the Wallaceburg Health and Housing Studies) CNTMC has adopted the New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments - updated in 2008.
    
  • Facts About Mold. New York City Department of Health. February 2001. www.nyc.gov/html/doh/html/epi/epimold.shtml
  • Health Canada: Fungal Contamination in Public Buildings 
    www.hc-sc.gc.ca/ewh-semt/pubs/air/fungal-fongique/index_e.html
  • Fighting Mold. Canada Mortgage and Housing Corporation. 1999
    www.cmhc-schl.gc.ca/en/burema/gesein/abhose/abhose_ce08.cfm
  • After the Flood. Canada Mortgage and Housing Corporation.
    www.cmhc-schl.gc.ca/en/burema/gesein/abhose/abhose_ce07.cfm
  • Moulds: Controlling Exposure is Essential. Construction Safety Association of Ontario.
    www.csao.org/uploadfiles/magazine/vol10no2/moulds.htm
• California Energy Commission See the California Mold Disclosure Law, and the California Department of Health Service / Environmental Health Investigations Branch report on whether it is feasible to adopt permissible exposure limits (PELs) for indoor mold - see SB 732 (Toxic Mold Protection Act of 2001, Implementation Update (August 2006) California enacted its original Toxic Mold Protection Act in 2001.
• European Union mold exposure standards: for apartments the E.U. uses these mold level designations
  • Indoor mold spore counts of < 50/m³ very low
  • Indoor mold spore counts of < 200/m³ low
  • Indoor mold spore counts of < 1000/m³ medium
  • Indoor mold spore counts of < 10000/m³ high
  • Indoor mold spore counts of > 10000/m³ very high -- Building Biology Evaluation Guidelines
  • Former building biology reference values for molds, SBM-1998 through SBM-2003 (using YM Baubiologie Agar at a culture temperature of 20-24 °C, colony forming units CFU): in the air < 200 no, 200-500 slight, 500-1000 strong, > 1000/m³ extreme anomaly (values refer for indoor air when outdoor reference levels are relatively low, below 500/m³); on surfaces: < 20 no, 20-50 slight, 50-100 strong, > 100/dm² extreme anomaly (values refer to surfaces that are subject to common and regular cleaning practices)
  • WHO: pathogenic and toxigenic fungi are not acceptable in indoor air; from 50/m³ of a single fungal species, the source(s) needs to be identi-fied; a mixture of common fungi typical for a given location (e.g. cladosporium) can be tolerated up to 500/m³. Senkpiel/Ohgke: Indoor concen-trations that are over 100/m³ above the outdoor air indicate a problem. EU statistics for apartments: < 50/m³ very low, < 200/m³ low, < 1000/m³ medium, < 10000/m³ high, > 10000/m³ very high. See 'Schimmelpilz-Leitfaden' by Environment Agency (Germany) for assessment details.
• France mold exposure standards: see Building Biology Evaluation Guidelines
• Germany mold exposure standards: see Building Biology Evaluation Guidelines
• Massachussetts mold legislation: Massachusetts, Michigan, New Jersey, New Mexico and New York, either have or are considering similar or modified mold protection acts similar to California's Toxic Mold Protection Act.
• Montana and other U.S. States mold disclosure legislation: requires building seller disclosure of mold during real estate transactions: Louisiana, Michigan, Montana, Nevada, New York, Oregon, Texas, & Washington either have mold disclosure laws or mold disclosure bills in committe. A California disclosure bill failed to pass in 2002.
• New York City Department of Health Mold Severity Levels: - see the New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments - updated in 2008. The New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments, 2000, issued by the New York City Department of Health, have are been widely accepted and quoted by public health departments in various U.S. states, Canadian povinces, and other regulatory agencies in other countries. The Ontario Ministry of Labour incorporates these guidelines in
  a Hazard Alert on Mould in Workplace Buildings issued in 2000
• U.S. CDC mold standards - Mold Questions and Answers: Questions and Answers on Stachybotrys chartarum and other molds, Questions and Answers on Stachybotrys Chartarum and Other Molds. Centers for Disease Control and Prevention, National Center for Environmental Health. March 9, 2000.
• U.S. EPA mold exposure standards - See Mold Remediation in Schools and Commercial Buildings
• U.S. OSHA mold exposure standards - see OSHA's Policies Regarding Mold and OSHA's Brief Guide to Mold in the Workplace and
• WHO - World Health Organization mold exposure standards- see World Health Organization Mold Bulletin. World Health Organization mold exposure guidelines specify that pathogenic and toxigenic fungi are not acceptable in indoor air as follows:
  • Mold spore counts of over 50/m³: for a single mold species, identify the source of mold
  • Mold spore count sup to 500/m³: a mixture of common fungi typical for a given location is acceptable - an example would be the most common mold genera found outdoors, Cladosporium sp.
  • According to Senkpiel/Ohgke: Indoor concentrations that are over 100/m³ above the outdoor air indicate a problem (we would argue that this standard is inappropriately tight) -- 'Schimmelpilz-Leitfaden', German Environmental Protection Agency
  • Source: Building Biology Evaluation Guidelines for the E.U.

Note: Previous data provided at this web article had been obtained from a presentation by J.R. Tucker, EMS-sales, who presented data at the NC/SC Environmental Information Association 2005 Conference, Myrtle Beach, SC citing mold exposure standards from Brazil, mold exposure standards for Czechoslovakia, Mold exposure guidelines for Finland, Mold exposure standards set by the Nordic Council, mold standards cited by the World Health Organization WHO, and mold exposure standards for the Netherlands and lastly, mold exposure standards for Poland. Those figures were quoted in this article from the material provided at that conference. Mold exposure standard numbers were expressed spores per cubic meter of air and did not consider individual or viable/non-viable or genera-species specific levels. We have removed those data points at the request of Dr. Robert Brandys who informed us that he was and remains the original author.

The Toxic Effects of Mycotoxins on Humans, Sheep, & Possibly on Pets

Mycotoxins are produced by some common molds found in buildings, including Aspergillus, Penicillium, Fusarium, Stachybotrys, and even Alternaria. Common classification groups of mycotoxins include aflatoxins, fumonisins, trichothecens, and ergot alkaloids. Arora has pointed out that the following conditions are necessary for mycotoxins to affect humans:

1. The right environment must be present for mycotoxin-producing molds to actually produce mycotoxins. [I have pointed out elsewhere that a given mold may produce or not product mycotoxins as a function of varying environmental conditions including the presence or absence of particular nutrients available to the mold -- i.e. it may depend on just what material is supporting the mold growth, not simply on the presence of mold and moisture.]
2. The mycotoxin(s) must have a pathway from the source to a susceptible person.
   
   The pathway may be direct contact with moldy material, inhalation of airborne spores or fungal fragments or of contaminated building materials. Important in understanding this pathway and the significance of "moldy odors" which We ascribe to volatile organic compounds given off by some molds under some conditions, mycotoxins are not volatile.
   
   Therefore, as Arora explains, airborne mycotoxin transmission has to be by inhalation of aerosolized mold or mold-contaminated materials. We point out elsewhere that the particle levels in air in a building vary widely over time for many reasons. However it should be no surprise to find airborne mold or mold-contaminated debris in a moldy building, particularly if demolition or improper "mold remediation" is going on.
3. The person has to absorb a toxic dose of the mycotoxin(s) over a sufficiently short time period. "Very little is known about what constitutes a toxic dose for humans -- see Stachybotrys chartarum mycotoxin discussion below.

Human Health Complaints on Exposure to Problematic Mold, possibly including Mycotoxins

Given even these stringent criteria, field investigations of moldy buildings that we have conducted from 1986 to present, included both human building occupants and in some cases pets who appeared exhibit complaints or symptoms consistent with mycotoxin exposure. Some of these clients and their physicians confirmed that exposure by appropriate medical tests.

Sheep Circling Disease and Toxic Mold Exposure

A fellow aerobiologist who also has experience raising sheep, Larry Syzdek (PAAA member) informed us of a mold-related illness well known to occur in sheep which Syzdek explained has occurred in his experience in sheep exposed to moldy straw, called in lay terms, "sheep circling disease" (Listeriosis, however Listeria moncytogenes is the specific bacterium - not a mold - known to cause listeriosis, a disease which can affect both other animals and also humans, particularly pregnant women who are 20 times more likely than other healthy adults to get listeriosis).

The author of this web article, (Friedman) has described field observations of dogs appearing to exhibit strange behavior (running in circles, falling down, disorientation, and occasional uncharacteristic aggressive behavior, and in one case, fatal internal bleeding after severe exposure to S. chartarum during a building demolition. These animals were pets of clients whose homes were severely mold-contaminated. With Syzdek, we have speculated on the possibility that other animals than sheep may be similar affected by exposure to some indoor molds and may be exhibiting behavior similar to that caused by Listgeriosis though the etiology of this disease is suspected to be different.

These hypothetical remarks presented here intend to solicit additional field reports and data, possibly in support of future controlled studies. Readers should not assume that we have drawn conclusions from the suggestive anecdotal data currently at hand.

Contamination levels of specific allergenic or toxic mold spores

Some species specific acceptable levels have been addressed and vary considerably by species, environmental conditions, and proponent.

REFERENCE:A number of resources cited here are reviewed more carefully in "Comparisons of seasonal fungal prevalence in indoor and outdoor air and in house dusts of dwellings in one Northeast American County," Ping Ren, Thomas M. Jaunkun and Brian P. Leaderer, Division of Environmental Health Sciences, Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven Ct. and appearing in the Journal of Exposure Analysis and Environmental Epidemiology (1999) 9, 560-568. http://www.stockton-press.co.uk

See references below for important additional information such as mold testing, cleanup and mold remediation guideline resources.

Stachybotrys chartarum in air

According to A.S. Arora: Stachybotrys chartarum strain s72 contains 1.0x10-4 nanograms of satratoxin H per spore. 10 billion spores of s72 S. chartarum must be present in a single cubic meter of air to produce one milligram of satratoxin H per meter of air. Dr. Arora continues: "... it was calculated that a no-effect dose [in rats] corresponds to a 24-hour exposure to 3 billion spores per cubic meter of air for an infant [human], 9.5 billions spores per meter for school-age children, and 22 billion spores per cubic meter for adults."

Dr. Arora did not expand his discussion to address any potential cumulative toxicity of longer term exposure to lower levels of mycotoxins in buildings.

This "toxic black mold," Stachybotrys chartarum, infamous thanks to media attention, is not designed for airborne transmission, being large and sticky.

Indeed we often find S. chartarum mold spores present in air samples when a dense colony of such mold is being mechanically disturbed, such as during demolition. But we have never seen it in air anywhere close to the levels cited as the "no-effect dose." We believe that we've been barking up the wrong mold-tree, and that one would be smarter to look in buildings for the Penicillium and Aspergillus families which spread throughout a building easily by airborne transmission

REFERENCE: Content of this section paraphrased and others quoted from a guest column, "Understanding the Health Effects of Mold," by Dr. Ajit S. Arora, MD, PhD, appearing in AIHA's magazine "The Synergist," September 2003, in the AIH Diplomate section, Pages vi-vii. Dr. Arora is a forensic medical examiner and medical toxicologist in Los Angeles. see partheniamedical.com.

Penicillium sp.

"Clean" residential buildings are typically 230/m3 +/- 630.
Buildings with evidence of flooding are typically much higher: 2200/m3 and
mold-damaged buildings are typically extremely high in comparison: 36,000/m3.

We usually find only trace levels of Penicillium/Aspergillus indoors in residential buildings and offices, so counts even close to the "clean" level may make further investigation a reasonable course of action, particularly where the building houses occupants have complaints possibly due to mold, or occupants who may be at extra risk.

Aspergillus sp.

Holmberg (1987) associated Aspergillus spore levels over 50 CFU / cubic meter with sick building syndrome. We comment elsewhere that depending on culturing mold in buildings is unreliable since toxic or allergenic particles may be present but may be of a species or genera which either does not grow on a culture medium, or which is overgrown by something else on the medium.

Further, relying on settlement plates to culture mold produces quantitatively skewed results since different particles settle out of air at different rates, confounding an estimate of their numbers. Anderson™ multi-stage samplers which develop culturable samples attempt to overcome the particle size problem.(C)Trap DJ Friedman

Aspergillus sp. may be the most common and serious airborne mold problems in buildings: Opinion: from the author (DJ Friedman) based on extensive field investigations and laboratory work, we suspect that several species of Aspergillus are probably the most common and widespread problem mold found indoors in buildings. These spores are small, easily airborne, grow on a variety of surface materials, and move readily throughout a building almost like a gas (due to their small size) riding on building convection currents and remaining airborne for long periods of time.

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MOLD LEVELS IN BUILDINGS
MOLD CONTAMINATION LEVELS
  MOLD CULTURES
  AIRBORNE SPORES
  CONTAMINATION LEVELS
TOXICITY VARIATION
  PARTICLE TOXICITY
  VIABLE vs NON-VIABLE
GOVERNMENT STANDARDS
WORLDWIDE STANDARDS
MYCOTOXIN EFFECTS
SPECIFIC MOLDS
  STACHYBOTRYS CHARTARUM
  PENICILLIUM SP
  ASPERGILLUS SP
also see ACCEPTABLE MOLD LEVEL
MOLD EXPOSURE RISK LEVELS
  L1: Very-Low Mold Risk
  L2: Low Mold Risk
  L3: High Mold Risk
  L4: Contaminated

• AAAAI - Asthma and Immunology's Aeroallergen Network is a national U.S. network of data gatherers that is responsible for reporting current pollen and mold spore levels to the public. American Academy of Allergy,
  Asthma and Immunology, 555 East Wells Street, Suite 110, Milwaukee, WI 53202. AAAAI can be contacted also by their website at www.aaaai.org
  AAAAI provides a table of interpretations of mold and pollen counts (of airborne particles/M3 of air) at http://www.aaaai.org/nab/index.cfm?p=reading_charts
• Bioaerosols: Assessment and Control. Janet Macher, ScD., M.P.H. American Conference of Governmental Industrial Hygienists, Cincinnati, OH. 1999
• Brazil: Occurrence of airborne bacteria and fungi in bayside offices in Rio de Janeiro, Brazil, by Brickus, L. S. R., Siqueira, L. F. G., Neto, F. R. D. and Cardoso, J. N., 1998)
• Building Biology Evaluation Guidelines, available in English Language Translation, provided by the German government, original citation: www.baubiologie.de/downloads/english/richtwerte_2008_englisch.pdf
  BAUBIOLOGIE MAES Schorlemerstr. 87 41464 Neuss Telefon 02131/43741 Fax 44127 www.maes.de
• Canada: Canadian National Toxic Mold Centre, and also see Moldy Houses: Why They Are and Why We Care & Additional Analysis of Wallaceburg Data: the Wallaceburg Health and Housing Studies)
  Fungal Contamination in Buildings: Health Effects & Investigation Methods, Health Canada, Minister of Health, original citation: www.hc-sc.gc.ca/ewh-semt/alt_formats/hecs-sesc/pdf/pubs/air/fungal-fongique/fungal-fongique-eng.pdf
  
• California: California Department of Health Service / Environmental Health Investigations Branch report on whether it is feasible to adopt permissible exposure limits (PELs) for indoor mold - see SB 732 (Toxic Mold Protection Act of 2001, Implementation Update (August 2006)
• Canada: Mould Guidelines for the Canadian Construction Industry - original source www.cca-acc.com/documents/electronic/cca82/cca82.pdf
• IICRC S520: Standard and Reference Guide for Professional Mold Remediation 2nd Edition. Institution of Inspection, Cleaning and Restoration Certification. Vancouver, WA. 2008
• IICRC S500: Standard and Reference Guide for Professional Water Damage Restoration 3rd Edition. Institution of Inspection, Cleaning and Restoration Certification. Vancouver, WA. 2006
  
• J.R. Tucker, EMS-sales, presented data at the NC/SC Environmental Information Association 2005 Conference, Myrtle Beach, SC citing mold exposure standards from Brazil, mold exposure standards for Czechoslovakia, Mold exposure guidelines for Finland, Mold exposure standards set by the Nordic Council, mold standards cited by the World Health Organization WHO, and mold exposure standards for the Netherlands and lastly, mold exposure standards for Poland.
  
  Those figures were quoted in this article from the material provided at that conference. Mold exposure standard numbers were expressed spores per cubic meter of air and did not consider individual or viable/non-viable or genera-species specific levels. [This is a serious limitation of the standards since the spores of different genera and species vary widely in total size, mass, and toxicity. -DF]
  
  On 3/16/09 we received follow up correspondence from Dr. Robert Brandys who indicated that Mr. Tucker obtained the data from Brandys' book Worldwide exposure standards for Mold and Bacteria. Dr. Brandys requested that we remove the data from this web article out of respect for his © protected book.
  
  
• Larry Syzdek, Albany, NY. personal communication at PAAA aerobiology conferences.
• Listeriosis, Discussion of, Penn State University,, Oct 27, 2002. "Listeriosis is a bacterial infection usually of the brain. Listeriosis is common in ruminants, pigs, dogs, and cats, some wild animals, and humans. Animals infected with Listeria can show clinical signs of abortions or nervous system disorders." Cooperative Extension
  The Pennsylvania State University, University Park, Pennsylvania 16802 FAX (814) 863-6140. See this US CDC article on Listeriosis for more information.
• National Allergy Bureau, is hosted by the AAAAI and can be contacted at www.aaaai.org/nab. "The National Allergy Bureau™ (NAB™) is the section of the American Academy of Allergy, Asthma and Immunology's (AAAAI) Aeroallergen Network that is responsible for reporting current pollen and mold spore levels to the public."
  
  
• OSHA - see OSHA's Policies Regarding Mold which includes the the original citations
• OSHA: Brief Guide to Mold in the Workplace, original citation: http://www.osha.gov/dts/shib/shib101003.html
• Post-Remediation Verification and Clearance Testing for Mold and Bacteria – Risk Based Levels of Cleanliness Assurance 1st Edition. Robert C. Brandys, PhD, MPH, PE, CIH, CSP, CMR and Gail M. Brandys, MS, CSP, CMR, CIEC. OEHCS Publications. Hinsdale, IL. 2003
  
• Recognition, Evaluation and Control of Indoor Mold, American Industrial Hygiene Association. Fairfax, Va. 2008
  Fungal Contamination: A Manual for Investigation, Remediation and Control. Hollace S. Bailey, PE, CIAQP, CIE, CMR. Building Environment Consultants, Inc. Jupiter, FL. 2005
• University of Minnesota - Department of Environmental Health and Safety can be contacted at http://www.dehs.umn.edu/ The University Department's advice on mold in buildings can be found at www.health.state.mn.us/divs/eh/indoorair/mold/index.html
• U.S. CDC - Mold Questions and Answers: Questions and Answers on Stachybotrys chartarum and other molds - original source: www.cdc.gov/mold/pdfs/stachy.pdf, Questions and Answers on Stachybotrys Chartarum and Other Molds. Centers for Disease Control and Prevention, National Center for Environmental Health. March 9, 2000.
• US EPA: Mold Remediation in Schools and Commercial Buildings: original EPA source - www.epa.gov/mold/pdfs/moldremediation.pdf

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Books, Complete List of Environmental Inspection, Diagnosis, Cleanup, Air Quality & Design, Inspection, Repair Books at the InspectAPedia Bookstore
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
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More Information on Building Diagnostic Inspections and Repairs

• Mold Levels on Surfaces in Buildings This article discusses mold test report terms - one set of suggestions about how to report mold levels in mold test samples of surfaces in buildings
• Mold Investigation Methodology. Mold & air quality inspection and testing: which home test kits for mold are valid - tape, swabs, cultures & air testing.
• Mold Risk Levels in Buildings: Based on Visual Inspection.
• Mold Spore Counts: are indoor fungal spore counts valid?
• Mold Classes: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
• Validity of Bulk Surface or Tape Sampling for toxic mold inspections
• Validity of Air Sampling for toxic mold inspections
• Validity of culture methods for toxic mold inspections - home test kits, sterile swabs, settlement plates, Petri dishes
• When is it appropriate to hire a professional to inspect a building and test for toxic or allergenic mold?
• What to look for in a toxic survey report or toxic mold test lab report

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The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

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