What you need to know about the different types of household molds and why spore trap sampling is highly questionable science at best...

So what if spore traps can't tell species' differences?

Since many water-intrusion molds look the same in a microscope, a spore trap analysis can't  provide species differentiation.  Thus, a comparison of indoor and outdoor samples won't provide information on the real differences between samples, only TOTAL counts of spores that appear similar.  Therefore, if a given indoor sample has the same total counts as a outdoor sample but the species are different, the inspection would likely miss a moisture-related mold problem. This is because a spore traps ASSUMES that the species variations are the same from a given set of indoor and outdoor samples.  Remember: A spore trap count will not identify different species of Aspergillus or Penicillium in a set of indoor and outdoor samples. 

Don't spore traps collect spores in the size range of most water-intrusion molds?

No. The spore trap is an impaction collector.  The collection efficiency of a spore trap is depending upon both the air flow rate and the physics of impaction.   In short, spore traps do not capture fungal spores below 3 to 4 microns in diameter.  This means that most species of molds of Aspergillus and Penicillium are collected at very low rates in standard spore traps compared to larger molds.  This phenomenon is a widely-known but little-discussed fact in the laboratory community.   

So how can we optimize collection?

To collect virtually all mold spores, the collection method must collect spores of all sizes.  Ideally, a filter type collector where air is collected and sampled through a porous medium should be used. The SporeLock™ System makes this option practical. In a SporeLock cartridge, the air sample is pulled through a membrane filter with 0.8 micron nominal pore size.  Thus, unlike for spore traps, almost all intact spores collected through the filter will be captured.

But can I order a standard direct examination spore count from a SporeLock™?

Absolutely.   The filter from a SporeLock can be removed in the laboratory and studied  by direct examination, just like a spore trap.  In fact, for most labs, counting a SporeLock filter is even easier than counting a spore trap!

So if SporeLock™ solves the "small spore size" issue,  why would I need to perform the more expensive MSQPCR analysis? 

Remember that a spore count is not the same as a spore species identification.  Whether we count spores in a standard spore trap or a SporeLock, we still cannot determine the species as in a MSQPCR.

Ok, but why should I quantify and determine the species for 36 different molds: The EPA Relative Moldiness Index and Group 1 versus Group 2 molds

Extensive research conducted by the U.S. EPA has established the EPA Relative Moldiness Index, otherwise known by the acronym ERMI. The ERMI score narrows down the total number of critical mold species to 36 indoor-indicator mold species. The 36 species are subdivided into two very different groups of mold (fungal) species, referred to as Group 1 and Group 2 molds. The Group 2 molds are found to be common in most homes and in low concentrations. Occupants living and working in indoor environments that contain predominantly Group 2 molds were healthy and suffered few respiratory related illnesses, nor did the building structures suffer leaks and water intrusion. However, Group 1 molds were much less benign, and occupants of these homes and environments suffered significant respiratory and asthma related illnesses. Moreover, Group 1 molds were significantly correlated to water intrusion due to poor construction or leaking pipes. Furthermore, EPA scientists and other reputable scientific investigators have amassed a body of published scientific research that conveys a major paradigm shift in the way mold samples are both collected and analyzed.

Is dust sampling really superior to air sampling?

Yes, in some ways.  EPA researchers have found that molds collected by air sampling are a poor indicator of the level of contamination for the worst household molds (the Group 1 or water intrusion/asthma molds). So they looked elsewhere, and found that every indoor environment harbors a stable mold reservoir; that reservoir was dust. Moreover, the dust held an historical account of indoor mold. Conversely, air samples collected by spore traps, although widely used, show weak correlation with unhealthy environments. Hence, indoor dust has a historical moldy tale to tell, which is read from the mold DNA. Sometimes that tale is the sorrowful account of leaky roofs, windows or pipes (the DNA identifies many group 1 mold species), other times it is a story of a happy dry home (common group 2 mold species). All buildings have dust and by analyzing the DNA in that dust for mold, all skeletons come out of the closet. And those skeletons, whether good or bad, are reflected in the EPA's ERMI index.

Read more details from Dr. Ed Sobek of Assured Biotechnology Corporation.

Read a Technical Brief on the disadvantages of spore trap analysis.