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Frequently Asked
Questions About Mold By: Dr. Nathan Yost, MD. Building
Sciences Corporation
What causes mold to develop?
Mold requires nutrients, water, oxygen and favorable
temperatures to grow. Nutrients for mold are present in dead
organic material such as wood, paper or fabrics; mold can also
derive nutrients from some synthetic products such as paints
and adhesives. Mold requires moisture, although some mold
species can obtain that moisture from moist air when the
relative humidity is above 70 per cent. Many molds thrive at
normal indoor temperatures; few if any molds are able to grow
below 40 F or above 100 F. Outside this range molds may remain
dormant or inactive; they may begin to grow again when the
temperature is more favorable. Temperatures well above 100 F
will kill mold and mold spores, but the exact temperature
required to kill specific species is not well
established.
How does mold get into a
building?
Molds are decomposers of
organic material such as wood, plants and animals. Mold and
mold spores are found in high concentrations wherever there is
dead matter such as a pile of leaves, manure or compost. Mold
spores enter buildings through the air or on people, animals
and objects that are brought into the building. Spores are
small bundles of genetic material and chemicals (similar to
seeds) that molds make under certain
conditions.
Are there harmful and non-harmful
molds?
There are only a few molds that
can cause infection in healthy humans. Some molds cause
infections only in people with compromised immune systems. The
biggest health problem from exposure to mold is allergy and
asthma in susceptible people. There are more than 100,000
types of mold. Good information has been developed for only a
small number of these molds – at least in terms of their
effects on human health. Most people tolerate exposure to
moderate levels of many different molds without any apparent
adverse health effects.
Some molds
produce powerful chemicals called "mycotoxins" that can
produce illness in animals and people. Scientific knowledge
about the health effects of these toxins on humans is quite
limited.
Does mold affect everyone the same
way?
No. Some individuals have a
genetic makeup that puts them at risk for developing allergies
to mold. People who have an allergy to mold, especially if
they also have asthma, can become ill from exposure to a small
amount of mold. Individuals also seem to be quite different in
their response to exposure to the toxic chemicals that some
molds release. These differences between individuals
contribute to the difficult question of determining safe
exposure limits for mold.
How much mold
exposure is harmful?
No one knows the
answer to this question for several reasons. Individuals are
very different with respect to the amount of mold exposure
they can tolerate. Children under the age of one year may be
more susceptible to the effects of some molds than older
individuals. Measuring or estimating "exposure" levels is very
difficult. "Exposure" means the amount of mold (microscopic
spores and mold fragments) that gets into a person usually by
breathing, but also by eating or absorption through the skin.
For example, a building may have a lot of mold in the walls
but very little of that mold is getting into the air stream.
In that case the people working or living in that building
would have little mold exposure.
Can mold
exposure cause brain damage or death?
Although some "experts" claim that individuals have
brain damage or have died because of exposure to mold and
especially mold toxins, there is no good science at this time
to support these claims. Consequently it is prudent to
minimize one's exposure to really moldy environments. By
"really moldy" we mean where there are large visible areas of
mold (more than a few square feet) or the building has a
"musty" odor because of hidden mold growth. There are many
epidemiological studies showing that people who live in houses
with dampness have many more health problems, especially
respiratory, than do people who live in dry houses. This
association does not "prove" that it is the mold that is
responsible for the increase in illness. However, it does
support the assertion that it is not wise to live in damp,
moldy buildings.
Does tighter building
construction promote mold development?
Tighter building construction does not by itself
promote mold growth, but tight construction combined with some
poor choices in design, building materials or operations can
increase the probability of mold growth. What do we mean? The
tighter the building construction the less air exchange there
is between the inside air and the outside air. Whatever gets
into the inside air stays there longer than it would in a
house with loose construction. Moisture that gets into the air
from activities such as cooking, bathing and even breathing
will remain in a tight house longer than it would in a loose
house. That's why exhaust fans should be installed in
bathrooms and kitchens and vented to the outside. Clothes dryers should also
be vented to the outside.
Tight
construction permits control of the air exchange between the
inside and the outside and can prevent the deposition of
moisture in walls and roofs. Controlling moisture, including
indoor relative humidity is the key to preventing mold growth.
Tight building construction when combined with source control
of moisture (exhaust fans) and controlled ventilation
(intentional introduction of outside air) reduces the
probability of mold growth in a building. Controlled
ventilation can be provided by a duct that brings outside air
to the return side of the air handler of a forced air system.
A timing device or fan cycler can be programmed to have the
air handler turn on for a specified number of minutes each
hour even when there is no call for heating or cooling. In
cold climates controlled ventilation is frequently provided by
a heat recovery ventilator (HRV).
Do new
building materials (e.g. drywall or paper faced gypsum board)
promote mold growth?
Mold needs water,
a nutrient source, oxygen and favorable temperature to grow.
Many species of mold love paper faced gypsum board. Why?
Making paper involves the mechanical and chemical processing
of wood. Paper is largely pre-digested so it is easy for mold
to get nutrients from the paper. But unless there is enough
moisture present mold can't grow on the paper. If paper faced
gypsum board is kept dry, it can be used and still not have
mold. This material is kept dry by controlling the interior
relative humidity, keeping rain from entering roofs and walls,
and NOT using paper faced gypsum in areas that are likely to
get wet. This means no
paper faced gypsum board in shower and tub areas. Cement
board, mortar or non-paper faced gypsum can safely be used in
these damp areas because these products do not contain
nutrients to support mold growth.
Are there
reliable tests to indicate the presence of
mold?
Almost all of us already have
two effective mold detectors: our eyes and our noses. If black
or green discoloration is noticed that is fuzzy in appearance
and is in a location that is damp or had been damp, it is
almost certainly mold. If a building smells musty, there
probably is mold somewhere; the mold may be on boxes stored in
a basement or in walls or in the crawl space. If you want to
find mold, look for the presence of water or a location where
water was likely to have been. If there is still any question
about whether the black stuff is mold, have a reliable
laboratory examine the material. All you need to know is
whether mold is seen when the material is examined under the
microscope.
An increasing number
of companies are offering "air testing for mold." On the
surface this seems like a reasonable thing to do. The problem,
however, is that the results of most air sampling for mold are
meaningless for two reasons. Air sampling for mold was not
developed to determine if an environment was safe or had a
dangerous level of mold in the air. Air sampling was developed
to help identify the location of a hidden reservoir of mold.
If the source of mold is already identified, air sampling does
not provide additional meaningful information. Furthermore,
safe or toxic levels of air borne mold have not been
established. An individual air sample for mold provides a
"snapshot" of what was in the air during the few minutes of
sampling. The results may not be indicative of the amount of
mold that is in the air during most of the
day.
Air sampling for mold should
be done either to obtain an answer to a question that cannot
be answered without the air sampling or to obtain data as part
of a research project. The Center for Disease Control (CDC),
the U.S. Environmental Protection Agency (EPA) and the
American Conference of Governmental Industrial Hygienists do
not recommend routine air testing for
mold.
If mold is present, what's the best way
to get rid of it?
The answer depends
on how much mold is present and where it is located. If the
mold is on furnishings or boxes simply discard the materials.
Moldy materials are not considered hazardous waste; they can
be sent to a regular landfill. However, it is smart to seal
the mold material in heavy plastic to protect the people who
handle it in transit and prevent spreading large amounts of
the mold into the building as you carry the material out of
it.
If the mold is on a hard
surface but occupies less than 10 square feet wash the area
with soapy water (scrubbing with a brush may be necessary),
rinse and allow the area to dry before repainting. If you have
asthma, severe allergies and a weaken immune system get
someone else to do the clean up.
Larger areas (greater than 10 square feet in area)
should be cleaned by someone with experience in doing this
type of work. Remember, determine what caused the moisture
problem and correct that problem. Otherwise, mold is likely to
recur.
Is it possible to completely eliminate
mold from the inside of a home or office
building?
The answer depends upon what
is meant by "completely eliminate mold." To keep a building
completely free of mold spores requires very efficient air
filtration and is only accomplished in special situations such
as hospital operating rooms and manufacturing "clean rooms."
Remember, mold spores are in the outside air virtually all the
time and some of them will get inside
buildings.
However, it is possible
to keep mold from growing inside a building. Moisture control
is the key to controlling mold in interior spaces. Air
filtration can contribute to lowering mold spores in the air
but is secondary to moisture control.
Should
I use bleach to get rid of mold?
No.
Although bleach will kill and decolorize mold, it does not
remove mold. Dead mold can still cause allergic reactions. It
is not necessary to kill mold to remove mold. Soap and water
and scrubbing can remove mold from hard surfaces. The
Environmental Protection Agency (EPA), the Center for Disease
Control (CDC) and the New York City Health Department agree
that bleach or other biocides should not routinely be used to
clean up mold.
How do I know when the mold
clean up is finished?
The mold cleanup
is finished when there is no visible mold remaining and there
is no dust or dirt remaining that could contain large amounts
of mold and mold spores. Routine clearance testing for mold is
not necessary. Leaving a few mold spores behind is not a
problem if the underlying moisture problem
has been corrected. Remember that mold
spores are virtually everywhere. Even if all mold and mold
spores are removed as part of the cleanup, spores from outside
will re-enter that space. The spores won't be able to grow
unless water is also present.
Where can I
get more information about mold?
Environmental Protection Agency
Information on
Mold/Moisture/Mildew. Available in HTML and PDF.
Center for Disease Control Information on
Mold. Various topics on mold including
information about strains.
About the Author
Dr.
Nathan Yost, MD is a Principal with the Building Science
Corporation, a building and construction consulting firm. Over
the last twenty years, Dr. Yost has been a home builder, and a
medical doctor specializing in respiratory illness. NAR has
hired Dr. Yost on a contractual basis to provide its members
with information and analysis on the scientific aspects of
mold and moisture issues. The information contained in this
FAQ is strictly the opinion of Dr. Yost, does not reflect NAR
policy, and should not be construed as medical
advice.
Reprinted from National Association of Realtors online
update - November 20, 2002
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Ethical Mold Inspector in the San Francisco Bay
Area By: Clayton Barry
There is much misinformation about mold in
today's media. Many people are turning mold into gold by
telling lies, or half-truths and playing off of our fears. In
the modern scientific times in which we live,
black-mold is as feared as yesterday's bogeyman. We
must dispell the myths.
What is the truth about Mold?
Who can you trust? How do you find someone who is ethical to
inspect a possible mold problem?
The fear of mold and the
high costs charged by restoration companies have caused
insurance carriers to cancel policies, raise rates, add
no-mold clauses, or lower clean-up limits. Some insurance
companies won't take on any new home policies in certain
mold crazy states. The situation is out of hand. Our
Federal government has not yet established any mold clean-up
standards. The medical world is still out to lunch on the
effects of mold. Is mold harmful or not?
There are no Federal
guidelines concerning mold contamination levels. There are no
proven medical reports that show mold is deadly to anyone
except persons with advanced HIV, or a few other medical
conditions. There are a few restoration trade associations who
are busy trying to set standards for clean-up. Within the
remediation industry prices for service are coming down.
Marketing and advertising pieces are reflecting a more
sensible no-panic message. The U. S. Environmental Protection
Agency (EPA) offers some advice. They walk the middle of the
road with their overall approach. Its better than nothing, at
least the EPA advises to use eye protection, respirator masks
and rubber gloves when cleaning mold. They indicate that
anything under ten-square feet of mold can be self cleaned,
over that they tell you to consult with an expert restoration
company.
 an example of black
mold
There are more than 60,000
molds that have been studied and more than 25,000 have been
named. Only a few produce spores small enough to work their
way into our blood stream. These are the ones that pose a
potential threat to humans. These are the ones that are called
toxic molds. The truth is that these molds are only
toxic under certain circumstances. They are not toxic all the
time. What seems to be agreed upon by all experts is that mold
is an allergen, similar to pollens, or dust mites. Most
experts agree that if you see mold growing in your home, solve
the moisture problem and clean-up the mold. Mold does not need
to be a mysterious frightful or thing.
Before you invite an
inspector or a mold remediator to visit your home there are a
number of questions to ask.
- The first question,
"How dangerous is mold?" If the person starts talking
about serious health risks, life endangering conditions and
doesn't present a more calm and balanced approach, pass this
person up.
- Another question to ask,
"What causes mold in my home?" If the answer is much
more complicated than explaining the cause is ALWAYS
excessive moisture, you have a person who is over
complicating matters.
- Ask this, " Does the
moisture problem need to be solved before mold clean-up is
started?"( There are times when moisture problems and
mold clean-up are addressed at the same time. Usually
moisture should be addressed first.) If the person answering
your question seems really eager to launch into the mold
clean-up work, you may be talking to a "mold is gold hound."
You may want to ask the
inspector or mold remediater to describe their typical report
and typical mold project. Asking for business and client
references is always a smart idea. If he doesn't provide
references by all means pass this person up.
An ethical moisture and mold
inspector will tell you that the majority of molds are not
harmful. They should explain that the few harmful types of
mold need to be present in large amounts to be of concern to
persons with specific health conditions. The molds also need
to be producing mycrotoxins to be considered dangerous.
The honest expert will explain that the source of moisture
must be stopped, otherwise the mold will be back within days
or weeks. THE MOISTURE PROBLEM MUST BE SOLVED. Anyone who
downplays the simple cause of mold and plays on your fears is
not truely interested in helping you.
Any and all service plans
for moisture drying and mold clean-up should be presented in
writing with the prices clearly noted as per-item charges.
(The costs of mold clean-up are coming down in the restoration
industry because the public is becoming aware of the truth
about molds. Mold scams are going away as people learn most
molds aren't harmful. The insurance companies are closing
their deep pockets making it less attractive to work in this
arena.)
In the
San Francisco Bay Area an ethical moisture and mold
inspector is the author of this article, Clayton
Barry. He can be contacted at: servpro9332@gmail.com
Note:
Joanne recommends
Clayton Barry and his Servepro company as she has done
business with Mr. Barry for many years and finds him
to be the best at what he
does!
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Joanne L. Gardiner, Broker, e-PRO
Realtor "For Old-Fashioned Service
in Cyberspace"
Advantage Realty Advantage
Mortgage Associates 3205 Whipple Road - Union City,
California 94587
(510)
429-4800
San Francisco Bay
Area San Francisco East Bay Real
Estate
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