Interpreting Mold Tests

Interpreting the results of mold sampling is no easy task.  That’s why many mold inspectors merely hand off some unintelligible lab report and run for it.  Why is it that so many people email me through this blog asking for help to interpret mold test results?  The reason is a failure on the part of the mold inspector to properly understand what they are doing.

You, dear homeowner, deserve more from a mold inspection.

In the comments section of this blog post, feel free to post your question related to mold testing.   However, here are the rules:


Exposure limit for fungal spores?

I was doing some reading today and I came across a paper looking at the dose-response relationship between fungal spores and various health effects.

Here is a quote from their conclusions:

“In conclusion, the combined evidence from human challenge and epidemiological studies support fairly consistent LOELs [lowest observed effect levels] of approximately [100,000] spores/m3 for diverse fungal species in non-sensitised populations. However, identification of the fungal biota is required in order to document the occurrence of the more toxic mycotoxin containing species and pathogenic species before measurements are evaluated.”

Here is a link to the document:

The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals 139. Fungal spores by Wijnand Eduard.

I have seen their LOEL value of 100,000 spores/m3 quoted in other published papers.  I’ll be interested to see if future research supports these findings for non-sensitive populations.  When it comes to sensitive populations, all the rules change!


California Statement on Building Dampness, Mold, and Health

Do people, especially children, get sick in damp buildings? Is it because of the mold? Or is it the bacteria, insects and rodents attracted to the moisture causing the problems? Or is it a combination of these exposures having a negative synergistic effect?

Although the answers to these questions are not well understood, the California Department of Public Health (CDPH) just released a 2-page statement to clarify some issues.

To the question, “Do people get sick in damp buildings?” here is what the statement says…

CDPH has concluded that the presence of water damage, dampness, visible mold, or mold odor
in schools, workplaces, residences, and other indoor environments is unhealthy.
Now that we’ve established it’s unhealthy, how should we as professionals diagnose these problems?  Here is what the statement says…
We recommend against measuring indoor microorganisms or using the presence of specific microorganisms to determine the level of health hazard or the need for urgent remediation.
This advice is contrary to current practice in the field of indoor air quality.  The truth probably lies somewhere between never measuring for microorganisms and always measuring for them.  In place of sampling for mold, the statement strongly recommends visually identifying the source of moisture causing the growth and correcting the problem.  The statement indirectly suggests that money is best spend fixing the water problem and drying, cleaning or removing impacted materials, rather than taking more samples.

The statement specifically recommends against “traditional methods” of sampling.  I presume they are specifically referring to air sampling for mold.  It seems like they are leaving the window open for other types of sampling, such as dust samples analyzed by PCR for the ERMI method (Environmental Relative Moldiness Index).  A recent study showed a correlation between ERMI levels at 1 year of age and developing asthma at 7 years of age (High environmental relative moldiness index during infancy as a predictor of asthma at 7 years of age, Reponen et al).

Although this advice is contrary to what many readers actually practice, I think we can learn something from the statement.  We need to double our efforts at solving moisture problems and spend less time chasing spores.  I recommend you download and read the 2-page document: Statement on Building Dampness, Mold, and Health.
allergies mold

Dampness, Dust Mites and Mold

When travelling this week, I was reading the latest Indoor Air journal and there were two interesting articles that both studied the relationship between mold and dust mites.

The first article was titled, A comparison of the allergic responses induced by Penicillium chrysogenum and house dust mite extracts in a mouse model _1.  Lab mice were exposed to varying concentrations of extracts from house dust mites and the mold Penicillium chrysogenum.  Here is a quote from the article,

“Our data suggest that Penicillium chrysogenum is a robust allergen and may be a more potent allergen source than house dust mite in this mouse model…   P. chrysogenum as well as other molds may play an important role in asthma development in our society.”

Although the article doesn’t address setting acceptable exposure levels for humans, the article shows the dose response figures for mice based on several health outcomes.

The second article I read that addressed mold and dust mites was A dose-dependent relationship between the severity of visible mold growth and IgE levels of pre-school-aged resident children in Taiwan _2.  I found this to be a fascinating article that wonderfully illustrates the point that it’s not exclusively mold that causes health effects in damp environments.

The study found a statistically significant dose-dependent relationship between severity of indoor visible mold growth and total serum antibody (IgE) levels.  So far, so good.  But when they looked at the specific type of antibodies (as opposed to the total), they didn’t find a correlation with fungal allergens.  They did however, find that dust mite antibodies corresponded with the indoor visible mold growth.

So what was going on?  The authors suspect that the degree of visible mold growth is an indicator of dampness.  The mold itself may not be affecting the children’s health, but the dampness leads to elevated concentrations of other exposures, such as dust mite colonies, that do affect health.  They recommend that studies done on the health effects of mold should control for these other exposures.

So to sum up, the first study found that a common type of mold was a more potent allergen than dust mites.  The second study found dust mites to be causing greater allergic responses than mold.  How can we explain the difference in these conclusions?

1. The first study was done on mice, the second on children.  Mice are different than children (one notable difference… my children are much LOUDER than mice!)

2. The first study exposed mice to equal amounts of Penicillium chrysogenum allergen and dust mite allergen.  But in a typical home, are there really an equal amount?  We can say that Penicillium chrysogenum is more potent gram for gram, but exposure to dust mite allergen may be several orders of magnitude greater.

3. In the second study, although total IgE antibodies were more closely correlated to dust mites, they could not establish solid statistical significance.  Also, they didn’t control for many other common indoor allergens like cockroach, which can be found in damp indoor environments.

Do these studies have anything in common?  Yes! They share the conviction that exposures to contaminants found in damp buildings can illicit a measurable affect on health.  That is a powerful message.

  1. Ward, M. D. W., Chung, Y. J., Copeland, L. B. and Doerfler, D. L. (2010), A comparison of the allergic responses induced by Penicillium chrysogenum and house dust mite extracts in a mouse model. Indoor Air, 20: 380–391. doi: 10.1111/j.1600-0668.2010.00660.x []
  2. Hsu, N.-Y., Wang, J.-Y. and Su, H.-J. (2010), A dose-dependent relationship between the severity of visible mold growth and IgE levels of pre-school-aged resident children in Taiwan. Indoor Air, 20: 392–398. doi: 10.1111/j.1600-0668.2010.00663.x []
Assessments mold

Federal Agency’s Checklist for Mold

The National Institute for Occupational Safety and Health (NIOSH) is conducting a pilot study to establish a standardized checklist for a mold and moisture inspection. This checklist is more designed for building owners and operators rather than for experienced consultants. First let me explain the background of the checklist and how it works, then I’ll later provide some commentary.

Ju-Hyeong Park and Michelle Martin at NIOSH are the developers of this checklist. The pilot project was unveiled at the Federal Interagency Committee on Indoor Air Quality (CIAQ) on October 13, 2010 in Washington DC. The information in this blog post is based on that presentation.


Mold: More than a Number

Viable Air Sample for Mold

You may take air samples when trying to identify a hidden mold problem.  The total number of spores in the complaint area should be compared to indoor and outdoor controls, or more accurately, “references”.  For example, if you find 10,000 spores per cubic meter in the complaint area, and only 1,000 in the reference samples, there is a high likelihood of indoor amplification.

Although it’s important to look at the total numbers, it’s critical to also make comparisons of the types of mold.  Each type of mold is unique.  There are some types that will predominantly grow on leaves outdoors.  These don’t have an apetite for building materials and will rarely be found growing indoors.  Other types, however, do have the enzymes needed to digest common building materials in its quest for more food.

A few references can help you make a distinction between types of mold typically found outdoors and those that can grow on building materials.  I’ll summarize a few of these references below:

allergies mold

Increased mold levels coming?

Alternaria spores

Can increased levels of atmospheric carbon dioxide (CO2) have an effect on mold spore levels? A new study suggests that increased CO2 will, in fact, lead to a greater number of mold spores outdoors with a resulting effect on allergies. As CO2 levels rise, can we expect to see more allergies to mold?

The article describing the research is titled “Elevated Atmospheric Carbon Dioxide Concentrations Amplify Alternaria alternata Sporulation and Total Antigen Production” and is found in this month’s Environmental Health Perspectives. The researchers were looking at just one species, Alternaria alternata, so we need to be cautious about drawing big conclusions from such a small study (sorry about the sensationalist blog title!).


Mycotoxins Indoors

This week I read a great blog post on mycotoxins from the Aspergillus Website. There has been considerable debate regarding the health effects of airborne mycotoxins through the years. In this post I will hit the main points related to mycotoxins indoors.


Mold and Health

Mold can be a touchy subject. There is a hot debate over what exact health problems can result from an excessive exposure to mold. In fact, a lot of the research and interest has shifted to damp buildings in general to include other microorganisms and their byproducts.

The current issue of the journal Indoor Air has an interesting article, “Culturable mold in indoor air and its association with moisture-related problems and asthma and allergy among Swedish children” by authors J. Holme et al.

Air samples for mold were taken in 382 homes in Sweden and compared to parental reports of asthma/allergy in children. The spore concentrations were also compared to inspector observations of mold odors and visual signs of moisture. The homes were almost evenly divided into symptomatic children and non-symptomatic controls.

The results of the study may be surprising!


Florida Mold Licensing

I’m teaching an IAQ and mold course in Florida this week, where legislation was recently passed to license mold professionals. The state law requires both assessors (inspectors) and remediation contractors to obtain a state license. The precise requirements have been slow to be released, with many questions still remaining. Here are some of the facts we do know: