Allergen
An allergen is a substance that
elicits an IgE antibody response
and is responsible for producing allergic reactions. Chemicals are
released when IgE on certain cells come into contact with an allergen.
These chemicals can cause injury to surrounding tissue - the visible
signs of an allergy. Only a few fungal allergens have been characterized
but all fungi are thought to be potentially allergenic. Click Here for More Information. . .
Biocide/Fungicide
Biocides and fungicides are chemicals that limit the growth
of or kill microorganisms such as fungi.
"Black
mold"
The poorly defined
term “black mold” or “toxic black mold” has
usually been associated with the mold Stachybotrys chartarum. While
there are only a few molds that are truly black, there are many that
can appear black. Not all mold that appears to be black
is Stachybotrys.
Fungi
Fungi are neither
animals nor plants and are classified in a kingdom of their own – the
Kingdom of Fungi. Fungi include a very large group of organisms,
including molds, yeasts, mushrooms and puffballs. There are >100,000
accepted fungal species but current estimates range to 1.5 million
species. Mycologists (people who study fungi) have grouped
fungi into four large groups according to their method of reproduction.
Hidden
mold
This refers to visible
mold growth on building structures that is not easily seen, including
the areas above drop ceilings, within a wall cavity (the space between
the inner and outer structure of a wall), inside air handlers, or within
the ducting of a heating/ventilation system. Click Here for More Information. . .
Microbial
Volatile Organic Compounds (MVOCs)
Fungi produce chemicals
as a result of their metabolism. Some of these chemicals, MVOCs,
are responsible for the characteristic moldy, musty, or earthy smell
of fungi, whether mushrooms or molds. Some MVOCs are considered
offensive or annoying. Specific MVOCs are thought to be characteristic
of wood rot and mold growth on building materials. The
human nose is very sensitive to mold odors and sometimes more
so than current analytical instruments. Click Here for More Information. . .
Mold
Molds are a group
of organisms that belong to the Kingdom of Fungi (see Fungi). Even
though the terms mold and fungi had been commonly referred to
interchangeably, all molds are fungi, but not all fungi are molds.
Mycotoxin
Mycotoxins are
compounds produced by some fungi that are toxic to humans or
animals. By
convention, the term “mycotoxin” excludes mushroom toxins. Fungi
that produce mycotoxins are called "toxigenic fungi”. Click Here for More Information. . .
Remediate
The term "remediate" simply means to fix a
problem. Related to mold contamination, remediation includes
fixing the water/moisture problem, and the cleaning, removal
and/or replacement of damaged or contaminated materials.
Spore
General term for
a reproductive structure in fungi, bacteria and some plants. In
fungi, the spore is the structure which may be used for dissemination
and may be resistant to adverse environmental conditions.
Stachybotrys
Stachybotrys is
a genus that includes approximately 10 species. These species
occur mainly on dead plant materials. Of these, Stachybotrys
chartarum is the most common. This species is cosmopolitan
and one of its natural substrates is straw. In the indoor
environment, it is commonly found on cellulosic materials including
paper, canvas and jute which are wetted to a water activity > 0.98. This
is a toxigenic mold Antigens to S. chartarum have been
identified. Click
Here for More Information...
“Toxic
mold”
The term “toxic
mold" has no scientific meaning since the mold itself is not toxic. The
metabolic byproducts of some molds may be toxic (see mycotoxin).
Toxigenic
fungi
These are fungi
that can produce mycotoxins (see above).
More Fungal Terms:
Conidium
(plural, conidia)
An asexual spore of mold (Hyphomycetes), produced on
the external surface of mycelium, not in a sporangium.
Conidiophore
A simple or branched
hyphal structure bearing or consisting of cells that produce conidia/spores.
Fruiting
structure
A general name for a spore-bearing organ both in macro-fungi
(e.g. mushroom) or microfungi (e.g. a mold).
Hypha
(plural, hyphae)
An individual fungal
thread or filament of connected cells; the thread that represents the
individual parts of the fungal body.
Mycelium
A mass of hyphae;
not in the form of large spore producing parts such as mushroom.
Common Indoor Fungi:
Alternaria
Alternaria is
a genus comprising approximately 50 species of which most are saprophytes
or plant pathogens. Alternaria alternata is an extremely
common saprophyte found on plants, wood, wood pulp, textiles
and food. It
is cosmopolitan in distribution [grows worldwide]. A. alternata grows
on the surfaces of leaves [phylloplane] and occurs in outdoor air at
modest levels peaking in July or August depending on the location (reaching
perhaps 500 spores/m3). The allergens of A. alternata can
induce reactions at very low concentrations in sensitized individuals. Phylloplane
strains of A. alternata i.e. those found in air, do not
produce AAL toxin. Some produce the phytotoxin [compound
toxic to plants] alternariol and related metabolites.
Aspergillus
Aspergillus is
the asexual stage of a number of ascomycetes. Species of Aspergillus are
distributed worldwide although they are somewhat more common
in warmer climates. These species grow on a vast array of organic materials. Many
species are cosmopolitan. There are 182 accepted species although
only 40 occur with any frequency. Species of Aspergillus include
several of considerable economic importance: A. flavus is
the main producer of the potent carcinogen aflatoxin and A. fumigatus is
an important cause of the invasive disease aspergillosis. Several
species are common on building materials including A. versicolor. A.
fumigatus is common in outdoor air in some regions in the fall,
occurring on composting leaves and other materials.
Cladosporium
Cladosporium is
a genus comprising approximately 500 species most of which are saprophytes
or plant pathogens of which perhaps 20 are common. Cladosporium
sphaerosphermum, C. cladosporoioides and C. herbarum are
the most common species. All are found on plants, wood,
wood pulp, textiles and food. Of the three, C. sphaerospermum is
the species typically found on building materials. The other
two are phylloplane species that occur in outdoor air at high levels,
peaking in June, July or August depending on the location (reaching
perhaps 10,000 spores/m3). Cladosporium herbarum produces
a wide variety of allergens and approximately 10% of the population
is sensitized to Cladosporium. Phylloplane strains of Cladosporium do
not produce metabolites with material toxicity.
Penicillium
Penicillium is
the asexual stage of a number of ascomycetes and species of Penicillium are
distributed worldwide although they are somewhat more common
in temperate climates. These species grow on a vast array of organic materials. Many
species are cosmopolitan. There are 225 accepted species although
only 70 occur with any frequency. Species of Penicillium include
several of considerable economic importance: P. verrucosum produces
ochratoxin on cereals and P. chrysogenum produces penicillin. Many Penicillium species
cause damage in damp building materials including the toxigenic species P.
aurantiogriseum.
Additional Facts:
Allergen
An allergen is a substance
that elicits an antibody response
and is responsible for producing allergic reactions by inducing
IgE formation, one of a group of immune system mediators. IgE antibodies
when bound to basophiles in circulation or mast cells in tissue,
cause these cells to release chemicals when they come into contact
with an allergen. These chemicals can cause injury to surrounding tissue
- the visible signs of an allergy. Fungal allergens are proteins
found in either the mycelium or spores. Only a few fungal
allergens have been characterized but all fungi are thought to
be potentially allergenic.
Fruiting
structure
A general name for a spore-bearing organ both in macro-fungi
(e.g. mushroom) or microfungus (e.g. a mold). More specific
terms have been use for fruiting structures, such as ascocarp,
basidiocarp, perithecium, sporocarp, etc.
Hidden
mold
This refers to visible
mold growth on building structures not easily seen including
for example, above drop ceilings, within a wall cavity [the space
between the inner and outer structure of a wall], inside air handlers,
or within the ducting of a ventilation system. Visible mold within a ventilation
duct is in immediate contact with the occupied space and release of
spores from such growth are known to be affected by air-movement and
air relative humidity. Spores of mold growth in wall cavities
are released as a function of air exchange between the wall cavity
and the occupied space. The rate of spore movement between such
spaces is typically slow. Volatile gases produced by visible
mold growth in wall cavities is also known to occur including
through air barriers.
Microbial
Volatile Organic Compounds (MVOCs)
Bacteria and fungi
produce odors as a consequence of their metabolism. More is
known about fungal volatiles which are involved in inter specific
competition especially amongst the fungi resulting in wood decay. Fungi
produce many metabolites that have boiling points around room temperature,
the most common of which is ethanol but the list is long including
many chemicals that arise also from man-made materials. These
compounds are responsible for the characteristic smell of fungi whether
mushrooms or molds. Some molds have characteristic odors. Particular
patterns of fungal volatiles are somewhat diagnostic for wood rot
and mold growth on building materials. The human nose is
very sensitive to mold odors and sometimes more so than current
analytical instruments.
Mycotoxin
Mycotoxins are
low molecular weight compounds produced by fungi that are toxic
to humans or animals. By convention, the term “mycotoxin” excludes
mushroom toxins. The ordinary use of the term mycotoxin refers
to compounds of importance in agriculture and includes a small number
of very potent compounds. This includes deoxynivalenol,
aflatoxin, fumonisin, ochratoxin, zearalenone and the much less
common nivalenol, T-2/HT-2 toxins, as well as some other Penicillium and Aspergillus toxins
and toxins from S. chartarum and Pithomycetes chartarum. By
convention, the term does not include compounds of low potency
or toxicity only in in vitro systems. The biochemical
targets of mycotoxins are usually many but the mechanism of toxicity,
even within families of toxins are typically different.
The genetic property to produce
mycotoxins is particular to given species. Fungi that produce
mycotoxins as defined here are called "toxigenic" fungi. Some
species including Fusarium graminearum and S. chartarum have
genetic sub-populations called chemotypes that produce different
mixtures of compounds. In the case of F. gramineaum,
these chemotypes are distributed by continent. In the case
of S. chartarum, both chemotypes occur together. The
occurrence of fungi on different substrates including building materials
is determined by the composition, water content, and temperature. Should
a toxigenic fungus grow in nature, one or more of the toxins
for which it has the genetic potential are typically produced.
Stachybotrys
Stachybotrys is a genus
that includes approximately 10 species. These species occur mainly
on dead plant materials. Of these, Stachybotrys chartarum is
the most common. This species is cosmopolitan and one of its natural
substrates is straw. In the indoor environment, it is commonly
found on cellulosic materials including paper, canvas and jute which
are wetted to a water activity > 0.98. This is a toxigenic mold. There
are two chemotypes of this species that produce either trichothecenes
plus spirolactones or atranones plus spirolactones; these toxins have
been demonstrated on mold-damaged building materials. The
closely related species Memnoniella echinata occurs on the
same materials but does not produce potent trichothecenes. Both
chemotypes of S.
charatum and M. echinata typically occur together on samples
of very wet cellulosic materials with M. echinata being
more important in warmer climates. This fungus does not cause invasive disease. Antigens
to S. chartarum have been identified.
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of Columbia, the Washington, DC Metro Area of Maryland and Virginia
Regions.
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