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 [↩]

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. (more…)

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: (more…)

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!). (more…)

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. (more…)

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! (more…)

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: (more…)

Mold Spores

Taking air samples for mold spores is easy. Knowing how to interpret the laboratory results is another matter.

There is no one level of mold that can distinguish a clean and moldy building. Outdoor spore types and concentrations have an important influence on the indoors. Unfortunately, the outdoor types and concentrations of mold vary quite widely over time and space.  In other words, some climates during certain times of year will have extremely high concentrations, and other climates at other times of year will have extremely low levels.  We can compare the indoors to outdoors, but realize that the outdoor concentration is a moving target! (more…)