I have a specific question that I would be grateful if you could address.  I regularly encounter condensation mould in dwellings and have successfully required remedial action based on the accepted risk to health.  Recently I have been challenged to prove that the mould was viable and emitting spores at the time of the inspection.  I have countered, arguing that the environmental conditions necessary to produce the mould and the heat loss associated with the damp dwelling are in themselves prejudicial to health.  Can you advise me if there is a reliable method of identifying if a condensation mould is emitting spores without air sampling?  Does the vegetative state of the mould prove it is spore forming and active?- Chris , United Kingdom 

 

            There are numerous studies that link dampness parameters to respiratory illness in residential buildings.  A number of have been conducted and published in the U.K.  These are summarized in the publication “Damp Indoor Spaces and Health” by the Committee on Damp Indoor Spaces and Health, Board on Health Promotion and Disease Prevention, Institute of Medicine of the National Academies, The National Academies Press, Washington, D.C. (www.nap.edu). The relationship between damp environments and human health effects is reviewed in chapter 5 of this publication. 

            The relationship between respiratory symptoms and dampness parameters such as water damage, visible mold growth and very high relative humidity is epidemiologically very strong.

            On the other hand only a few studies have been able to show a relationship between respiratory health symptoms and airborne mold concentrations.  As a consequence, indoor air quality scientists as well as public health authorities place emphases on correcting “dampness” problems in mitigating respiratory health problems experienced by building occupants.

            Airborne mold concentrations in buildings vary considerably over a course of a single day and of course seasonably.  In addition a variety of species may be present which also vary considerably.  It is this variability that makes it difficult to demonstrate a dose-response relationship between respiratory symptoms and airborne mold.

            Airborne mold sampling methods are problematic in that some methods only quantify airborne mold particles that are viable and culturable on the media used.  These viable/culturable methods lend themselves to identification of genera and species. However, most airborne mold particles are no longer viable and thus cannot be quantified.  Nevertheless, non-viable mold particles are allergenic and thus can cause health effects.

            Total mold spore methods can in theory provide a better characterization of mold exposure risks.  However, they are limited by the fact that major mold genera and their associated species (i.e., Aspergillus, Penicillium, Aureobasidium, yeast, etc.) cannot be easily differentiated and are usually only reported as Aspergillus/Penicillium spores or amerospores.  In addition many laboratories use optical magnifications (400 or 600X) that are not adequate to even see many of the small spores in this group.

            Many fungal species grow rapidly when environmental conditions are optimal.  Under such conditions they primarily produce vegetative hyphae.  However, as soon as they are subject to some environmental stress (such as decreasing moisture levels, the presence of ultraviolet light, etc.) they begin to produce reproductive spores which are designed to move via air currents to new substrates.

            One can use a tape lift sample from visible mold growth area to determine whether mold spores are present and in many cases identify mold present to the genus level.  One can press the tape lift sample onto a culture media to determine whether vegetative mold structures or spores present can grow and by inference release spores into the indoor environment.

            The consensus in the mold scientific community is that the presence of visible mold growth indicates that a potential mold exposure problem exists that requires remediation to protect the health and well-being of building occupants. As such, you are correct in your approach in conducting building evaluations and making remediation recommendations. In the US we tend to want test results because it reflects common practices in medicine and a need to show that that is a potential causal association exists between airborne mold and health effects particularly as it relates to litigation.

 March 24, 2005