An indoor mold
assessment states “Total fungal spore and mycelial fragment indicated
presence of several fungi types, however, these levels were not found
to be elevated when compared to the outside sample.” In addition, the
report states that several wall cavities “indicate presence of
slightly-elevated-to-elevated levels of Aspergillus/Penicillium-like
fungi and/or Cladosporium”. We have had all windows resealed
from the outside and have taken every precaution to prevent moisture
from entering. Since the quality of air has been deemed safe, do I
have to do anything with the wall cavities? Will an indoor air
quality check be sufficient maintenance?-Evelyn ,Texas
One of the most problematic things
that a homeowner has to deal with when they have mold testing
conducted is to interpret results received from laboratories (which
are often limited in trying to interpret the results themselves).
Many if not most mold-testing
laboratories compare indoor and outdoor mold levels to provide
guidance to their customers, and most experts in the field believe
that such comparisons are essential. However, such comparisons have
limitations which in many cases result in erroneous conclusions.
Outdoor levels significantly higher than those indoors do not mean
that mold levels indoors are safe. There are a variety of reasons why
this may be the case.
Except in the winter months when snow
is covering the ground, outdoor air levels are almost always higher
than those indoors. At this time of year as annual, perennial, and
crop plants mature and die, one can expect high to very high outdoor
mold levels (since fungal species are doing what they have evolved to
do, that is decay dead organic matter). Indoor/outdoor comparisons
made during Autumn can be particularly misleading.
In houses that are climate-controlled
(do not open windows much) the spectrum of mold types indoors is very
different from that outdoors. At this time of year outdoor mold
genera are dominated by dematacious (dark colored) genera including
Cladosporium, Alternaria, Dresclera, Epicoccum, Basideospores.
Fusarium is common as well. Though Cladosporium is common
indoors in climate-controlled houses, indoor mold, particularly when
there is an infestation problem, has a much higher percentage of
Aspergillus and Penicillium-type spores. When the
Aspergillus/Penicillium count indoors is elevated above that
outdoors, one can interpret such results as indicating a potentially
significant infestation and exposure source indoors. In such
situations total spore count comparisons can easily result in
erroneous conclusions.
Indoor/outdoor comparisons may not be
reliable when one opens windows a lot. In such cases outdoor mold
enters the building environment where spores can go through many
cycles of deposition and re-suspension. Indeed my experience is that
outdoor mold deposited on indoor surfaces influences indoor air
concentrations for months after houses are “closed up” for the heating
season (This can be seen in air and dust comparisons in several
recently published studies).
The fact that slight-to-elevated mold
levels were found in the exterior side wall of your house indicates
that an infestation has occurred as a result of water intrusion .As
such there is a strong possibility that indoor levels will be affected
by such an infestation, particularly on breezy, windy days.
In interpreting your test results the
finding of elevated mold levels in wall cavities is more significant
than results of indoor/outdoor comparisons. Reported test results do
not indicate that your house is “safe”, nor do they indicate any
particularly danger. You appear to have a mold problem in your wall
that needs remediation to protect the structural integrity of the wall
and family members who may be mold sensitive.
September 24, 2004
Indoor Environmental Quality (2000), Thad Godish Ph.D.,
C.I.H
Direct E-mail
00tjgodish@bsu.edu
Indoor Environmental Quality (2000), Thad Godish Ph.D.,
C.I.H
Direct E-mail
00tjgodish@bsu.edu
