I hope you're doing well and enjoying the summer. I also hope that you'll find the following article about
optional supporting fungal information and data by Dr. Harriet Burge both interesting and useful.
With best wishes,
Dave Gallup
A Discussion of Optional Supporting Fungal Information and Data from the Laboratory
By Dr. Harriet Burge, EMLab P&K Chief Aerobiologist and Director of Scientific Advisory Board
Air sampling for fungal spores to help evaluate allergen load in homes and buildings has been
common for over half a century. Originally, only a few experts were involved, and they were
all trained mycologists and aerobiologists, or acted in conjunction with such experts, usually
in research efforts. The data from these studies was generally analyzed quantitatively if the
data sets were large enough, or qualitatively by these few experienced investigators.
Investigations of single homes or buildings included intensive on-site inspections, and air
sample results were interpreted in light of the visual findings.
One of the reasons mycologists and aerobiologists continue to be important members of the
investigative team is to aid in putting the fungal information into context with the other sets
of data. Fungal data is often difficult to interpret due to many factors. These include that
fungi are naturally occurring, their concentrations can vary widely and rapidly, and the multitude
of fungal species comprising a diverse set of characteristics that affect how the results should
be interpreted. This fungal complexity, combined with simplistic rules of thumb and a lack of
consensus about standards has led to a range of interpretations that is incredibly broad, as
many of you have no doubt personally observed.
As an entity that generates sets of data that require mycological expertise to be interpreted
correctly, we feel an obligation to provide data about fungi that may make it easier, in some
situations, for investigative experts to put the fungal sampling results into context with the
rest of the investigation. Consequently, in conjunction with several of the original mycologists
and aerobiologists that essentially founded the field, along with other engineers and scientists,
EMLab P&K has developed two tools to assist investigators in the interpretation of air sampling
data. These tools, both optional and free of charge, are the
MoldRange and the
MoldScore.
MoldRange was designed to demonstrate the range over which outdoor spore concentrations can
vary by season and geography. The outdoor aerosol is an extremely important background variable
against which indoor air sample data must be compared. However, no single outdoor sample is
sufficient to characterize the outdoor aerosol at any one place and time. Precipitation, wind,
local sources, and many other factors affect the outdoor aerosol, causing it to change from
minute to minute. The MoldRange analyzes the largest outdoor fungal aerosol database currently
in existence. Using it, one can evaluate outdoor air sampling data for representativeness
compared to many other samples collected in a similar area or during the same season. The data
set we use is compiled data from well over one hundred thousand outdoor spore trap samples that
have been analyzed by our certified and highly proficient analysts. Although there will be
occasional atypical or faulty outside samples submitted to our database, its large size ensures
that the data resulting from these events appear as outliers, and do not significantly affect
the reported medians or reported recovery frequency. MoldRange is not a substitute for on-site
outdoor samples, which is why the report cannot be generated without an actual outside sample
from the project in question. Nor is MoldRange a substitute for expert observations of the site.
It does, however, provide additional information about typical outdoor spore concentrations,
and allows more informed judgments about individual outdoor sampling data means. Further,
there are going to be those times when the outside concentration of 'normal' spore types, such
as Cladosporium, is below the detection limit. In these cases, simplistic interpretation
of inside to outside ratios may well lead to inappropriate conclusions, especially by the
partially informed home owner. In these cases, where the expert onsite knows that the data is
being interpreted incorrectly, MoldRange can provide unbiased data to aid in communicating this
fact to the homeowner and be an important tool in preventing thousands of dollars of unnecessary
remediation.
MoldScore was designed to quantify the way our experts compare indoor and outdoor spore
populations. It is a calculation that takes into account indoor/outdoor concentrations of
specific fungal spore types, weighting each spore type for the probability of having an indoor
source. It allows for errors due to low indoor and outdoor spore concentrations and to extremely
high outdoor concentrations. The resulting score represents the likelihood that a given set of
sampling data indicates an indoor source for the sampled aerosols. In the process of developing
the MoldScore we evaluated the many variations of indoor/outdoor ratios that are recommended
and used by many. We compared all of these methods to the MoldScore, and to the scores generated
directly by our mold experts. None of the indoor/outdoor ratio approaches performed as well as
the MoldScore with respect to false positives and false negatives.
MoldScore is not meant to be used by itself, since, as many investigators know, both false
positive and false negative results are possible with fungal air sampling data. Rather, the
MoldScore is intended to serve as a valuable adjunct to a carefully conducted visual inspection
and a well-designed sampling strategy. In many cases, the data collected using these steps will
lead to obvious conclusions by the experienced investigator. In more difficult cases, the
MoldScore may be helpful by adding unbiased, mycological experience to the interpretation. In
addition, it is an objective measure that will generally support the conclusions of experienced
investigators. Where the MoldScore differs from the investigator's conclusion, the comparison
may lead either to a reassessment by the investigator, or to a reassessment of the MoldScore.
Both of these events have occurred with the latter serving as a basis for continued development
of the MoldScore.
In addition to these tools, EMLab P&K provides statistical calculations based on the methods
proposed in the ACGIH Bioaerosols book.
Although a study we performed of 100 data sets interpreted by mycologists, engineers, and
professional IAQ investigators did not find these methods as representative of an expert's
opinion as is the MoldScore, we offer them because they are recommended in such a prestigious
publication. EMLab P&K also offers other optional reports such as graphs in a variety of
formats to aid in communicating the results to your client, and exports that can be imported into
text editing, spreadsheet, or database programs.
Finally, the claim has been made that use of these tools increases liability risk. However,
the truth is quite the contrary. The best protection from liability is to do the very best
and most complete possible mold investigation. The use of all of the available tools is an
important part of that mold investigation. For many mold investigators, the MoldRange is not
necessary since they have accumulated their own large databases specific to the region in
which they work. For others it is essential if indoor/outdoor air sampling is to be used.
Likewise, the MoldScore can be an important adjunct in mold investigations, but would never
be used in isolation. It is meant to supplement the experienced observations of a good mold
investigator, for whom it will almost always provide confirmatory data. If the MoldScore is
not confirmatory, the mold investigator has the option of questioning the reliability of the
MoldScore, and/or questioning his/her own observations. There are no simple answers to fungal
aerosol data interpretation, and the use of air sampling and adjunct interpretation approaches
should be restricted to those occasions where it is essential to test a specific hypothesis.
