Environmental Engineering Reference
In-Depth Information
2.
Fungal glucans
Glucans are polyglucose polymers present in the cell walls of mold hyphae
and spores and certain bacteria. They are very soluble in water and retain
their biological activity when mold spores are no longer viable.
Because of their macromolecular size and diversity, glucans are not easily
measured in environmental samples except by bioassay procedures. Though
they are likely to be ubiquitous in suspended aerosols both in indoor and
outdoor air, little information is available on the range of airborne glucan
concentrations indoors.
III. Exposure assessments
Numerous studies have been conducted to assess airborne mold levels in
both outdoor and indoor environments. These studies have attempted to
characterize the presence and prevalence of genera (and in some cases, spe-
cies) present in airborne samples as well as total mold spore concentrations.
Most studies have been based on the use of culturable/viable sampling
methods, wherein airborne mold spores/particles are impacted onto spe-
cially-formulated nutrient agar media. Such sampling is used to identify and
describe the dominant types that grow on the culture media used and pro-
vide a relative measurement of their abundance. It has the advantage of
providing investigators with the opportunity to identify mold colonies to
the species level. However, culturable/viable sampling methods have sig-
nificant limitations. Media used differ in their ability to support the growth
of different species and genera. In addition, an often high percentage of
airborne mold spores is not viable and cannot grow on any culture media.
As a consequence, levels determined from airborne sampling are only a
measure of the abundance of viable spores present and their culturability
on the sampling media used.
Compared to culturable/viable sampling, total mold sampling methods
which collect mold spores and other particles on greased microscope slides
have been little used to assess airborne mold concentrations. However,
because these sample values potentially represent most mold spores and
hyphal fragments, including both viable and nonviable mold structures, they
are a better indicator of airborne mold concentrations. Since allergenicity is
independent of viability, total mold spore sampling is also a better indicator
of potential health risks. It is not possible at this time to identify spores to
species, nor in many cases to genus either, using total mold spore sampling.
Despite limitations associated with airborne mold sampling, studies
conducted to date can be used (to a limited degree) to describe dominant
mold types present in outdoor and indoor air and their relative abundance.
A. Outdoor prevalence
Significant differences in mold types present and total colony counts have
been reported in comparison studies of outdoor and indoor airborne mold
