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1) What is mildew and is it
different than mold?
"What is mildew?"
The answer depends on whether you ask a scientist or a nonexpert. Mycologists, who study
fungi, use the term "mildew" only for fungi that grow on plants. When
mycologists say "Mildew," they mean the white growth that causes diseases in
plants.
People who are not
scientists use the term "mildew" differently. For them, mildew is the
discoloration caused by mold in buildings. The molds that grow around windows or in
bathrooms are called "mildew."
Is mildew different than
mold? The mycologist would say they are different. Mildew only grows on plants outdoors.
The nonexpert, however, sees the effects of mold growing indoors and calls it
"mildew."
2) How long does it take mold to
grow?
To be more specific, we
should ask, "How long does it take for a mold spore to germinate?" Then
we should ask, "How long does it take growing mold to colonize?"
To grow, molds need a food
source, a certain temperature and moisture. Where these conditions are present, molds can
germinate and colonize. How fast growth occurs depends on the combination of conditions.
Spores can germinate after only 12 hours in some conditions and some grow in 24 to 48
hours. Houses offer an ample food supply—drywall, wood, insulation, paper. When these
materials become damp or wet, settled spores can become growing molds.
Molds may colonize in 1 to
12 days depending on the type of mold. Following are several types of molds and the number
of days in which colonization may take place:
- Mucor sp. colonizes between 1 and 2
days.
- Rhizopus sp. colonizes between 1 and 2
days.
- Aspergillus sp. colonizes between 2
and 3 days.
- Penicillium sp. colonizes between 2
and 3 days.
- Stachybotrys chartarum colonizes
between 8 and 12 days.
3) Why do molds give off musty
odors?
The musty odors produced by
molds are known by scientists as Microbial Volatile Organic Compounds. (These compounds
are abbreviated as mVOCs.) Some mVOCs produce musty and moldy odors, which result from the
chemical changes taking place during the mold life process. They are waste products given
off by actively growing molds. Health effects such as headaches, dizziness and nausea have
been linked to exposure to mVOCs, but research is only beginning. Odors from mVOCs are a
sign that mold is actively growing and so may indicate a level of mold contamination
requiring remediation.
4) What are mycotoxins and are
they dangerous to humans?
Mycotoxins are poisonous
substances. "Myco" means fungus, so think of mycotoxins as "fungi
toxins." They are designed for chemical warfare against other organisms, even against
other types of molds. Living molds may produce mycotoxins to discourage other molds or
bacteria from growing in the same territory. Unfortunately, humans who inhale, ingest or
touch mycotoxins may have a toxic reaction. Some mycotoxins have been shown to produce
human health effects, while little is known about the possible harmful affects of some
other mycotoxins.
We should not panic over
mold toxins. Not all molds produce mycotoxins; furthermore, molds that can produce
mycotoxins do not produce them in all situations. EPA cautions that finding molds in a
building does not mean that mycotoxins are also in the building, and even when
mycotoxins are present in a building, the quantities may not be large and thus health
threatening.
5) How do you prevent mold from
spreading?
To prevent mold spores from
spreading to clean areas of a building, a remediation contractor must control air
movement. Two important procedures are (1) erecting critical barriers and (2) establishing
negative pressurization in the work area.
Critical barriers block the
paths that airborne mold spores might follow. Contractors construct critical barriers by
placing two layers of polyethylene over any air pathways through which spores might travel
(i.e, air vents, wall plates, recessed lighting, doors and other openings).
To establish negative
pressure, a contractor creates low air pressure in the work area. The result is
that rooms and areas surrounding the work area will have higher air pressure than
the work area. Maintaining negative air pressure prevents mold spores from being carried
by air movement from the work area to uncontaminated rooms of the job site.
6) Will ozone kill mold and the
mycotoxins produced by mold?
The American Conference of
Governmental Industrial Hygienists do not recommend using ozone on visible mold
growth. Due to various factors, ozone has not been found effective against molds. One
problem is the elements that cause ozone to be less effective. Ozone can be affected by
temperature and pH, decreasing its impact on mold. Organic materials in the structure can
also affect ozone.
A second problem is that
ozone does not kill what it does not reach. No method of application can ensure that the
ozone contacts every surface where mold contamination exists.
The last problem is
mycotoxins. Even if ozone did affect mold, the toxins on mold spores and mold fragments
still remain on surfaces and can still cause allergenic reactions in people. To remediate
a mycotoxin problem, you must reduce the concentrations of mycotoxins in the structure.
In summary, ozone does not
work with molds. In addition, molds are usually found in wet environments. Using ozone on
wet materials in a wet environment may result in the bleaching of surfaces.
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