Environmental Engineering Reference
In-Depth Information
are characteristically microbial or fungal in the sense that they are responsible
for the musty, mildewy, earthy, or mushroomy odors associated with mold
infestations. Commonly reported fungal VOCs include: 3-methylfuran, hep-
tanone, 1-octen-3-ol, octan-3-ol, 2-octen-1-ol, octen-3-one, octan-3-ol, 2-
methyl-1-butanol, 2-hexanone, geosmin (1,10-dimethyl-
-9-decalol), ace-
tone, 2-butanol, dimethyl trisulfide, methanol, 1-propanol, 4-decanol, 2-
methylisoborneol, trimethylhexane, 3,3-dimethyl-2-oxetanone, 3,3-dimethyl-
1-octene, ethyl 2,4-dimethylpentone, and 2-methoxy-3-isopropylpyrizine. As
can be seen, most fungal MVOCs are alcohols and ketones.
Microbial VOCs produced by mold colonies vary with individual species
as well as substrates colonized. The most frequently reported MVOC in
building investigations is 2-octen-1-ol. This compound, as well as 1-octen-
3-ol, 2-hexanone, and light alcohols, tends to be associated with water-
damaged materials. Fungal VOCs, reported as total MVOCs, range in con-
centration from 50 to 126
trans
µ
g/m
in problem buildings, while outdoor levels
3
average 8.6
. Their odor is readily detectable despite relatively low
concentrations (even in mold-infested buildings), indicating a relatively low
odor threshold.
µ
g/m
3
B.
Fungal toxins
Many fungal species produce toxins which, on exposure, adversely affect
the physiological functioning of other organisms. Toxins such as antibiotics
inhibit the growth of bacteria and provide a competitive advantage to the
organism producing the antibiotic. Other toxins may inhibit the growth of
fungal species in a somewhat similar fashion.
Fungal toxins can adversely affect humans and other animals. These
include the highly poisonous toxins formed in the fruiting structure of a
variety of mushroom species and mycotoxins produced by the mycelia of
many common fungi.
1.
Mycotoxins
Mycotoxins are generally produced when fungal mycelia are subject to nutri-
ent limitation. Well-known mycotoxins and species producing them are sum-
Penicillium
and
Aspergillus,
commonly produce mycotoxins. Best known of these are ochra-
toxin A and aflatoxin B, both relatively large molecules. Ochratoxin A is a
colorless crystalline compound with a dihydroisocoumarin moiety linked to
the amino acid phenylalanine and an atom of chlorine attached to the iso-
coumarin ring. The aflatoxins are a family of substituted coumarins contain-
ing a dihydrofuran moiety.
Of particular note are mycotoxins produced by
,
a species of fungi that grows well on substrates containing cellulose (such
as hay, straw and, in buildings, ceiling tile and gypsum board).
Stachybotrys chartarum
S. chartarum
has a characteristically dark mycelium and large, initially sticky asexual
spores. Mycotoxins produced by
S. chartarum
include highly toxic members
