fig2
Figure 2 shows the limiting RH and temperature conditions
for six categories of moulds ranging from highly hydrophilic (water
loving) to highly xerophilic (dryness loving). Each area on the
graph represents a family of mould species with similar growth requirements
and the curves represent upper and lower limiting temperature and
relative humidity levels for each species group. Examples of mould
species present in each category are:
A:
Aspergillus repens
B: Aspergillus versicolor
C: Penicillium crhysogenum
D: Cladosporium sphaerospermum
E: Ulocladium consortiale
F: Stachybotrys atra (Stachybotrys chatarum)
The
presence of the fungus Stachybotrys atra in the upper category is
particularly important, since this mould is suspected to have caused
infant deaths, and has been linked with headaches, nose bleeds,
and sinus problems. Stachybotrys is a particularly dangerous
dark coloured mould that grows on material with high cellulose content,
such as wood, fibreboard, the paper covering of gypsum wallboard,
wallpaper, dust, and wood in conditions of very high humidity over
long periods of time. Excessive humidity resulting in condensation
on walls and window areas, water spillages and leakages through
foundations or roofs may lead to the growth of Stachybotrys.
A
and B: Moulds of the type Aspergillus.
Aspergillus is a group of moulds of worldwide distribution,
especially autumn and winter in the Northern hemisphere. Only some
of these moulds cause illness in humans, and moulds in areas A and
B on the graph largely cause adverse health effects only in susceptible
individuals. In people with healthy immune and respiratory systems,
the presence of Aspergillus can occasionally cause irritation of
the sinuses. Symptoms include a blocked nose, headache or facial
discomfort.
As previously discussed, the mould releases airborne
spores which can cause an allergic reaction in asthmatics; up to
20% of asthmatics have experienced symptoms caused by moulds of
the genus Aspergillus. The allergy is also common in cystic fibrosis
patients. Aspergilloma is another disease also caused by the Aspergillus
mould. The fungus is able to grow within a lung previously damaged
by respiratory illness such as Tuberculosis or Sarcoidosis. Any
lung cavity causing disease can leave a person open to developing
aspergilloma. The fungi are able to penetrate the lung cavity and
germinate secreting toxic and allergic products and causing symptoms
of weight loss, chronic cough and general lethargy. Coughing of
blood (haemoptysis) can occur in up to 50-80% of affected people.
Home occupants with damaged immune systems, for example people with
HIV, leukaemia or people who have undergone bone marrow transplants
can die from invasive aspergillosis where the fungus can transfer
from the lung through the blood stream to the brain and to other
organs, including the eye, the heart, the kidneys and the skin.
Even with treatment with antifungal drugs, only a third of patients
survive the disease. In addition, Aspergillus versicolor is capable
of producing mycotoxins. Mycotoxins are poisonous substances produced
by moulds which occur on spores and small mould fragments that may
be released into the air. The mycotoxin produced by Aspergillus
versicolor, Sterigmatocystin, has possible hepatotoxic (liver damaging)
and carcinogenic effects. To sum up, the presence of moulds of the
genus Aspergillus in the RH/temperature categories A and B could
be serious for vulnerable people, especially individuals with poor
respiratory of immune systems. In addition, moisture levels required
for the growth of these moulds are relatively low so the prevalence
of RH/temperature conditions in A and B should be taken seriously.
The home occupant should be made aware of remedial measures to prevent
growth of the above mould types.
C:
Moulds of the type Penicillium
The mould Penicillium chrysogenum is the responsible
for the secretion of the antibiotic Penicillin. The Scottish scientist
Alexander Flemming discovered its antibacterial effect in 1929 when
he noted that bacterial colonies on an agar plate had reduced in
size after a contamination of Penicillium chrysogenum. His discovery
saved millions and he was posthumously awarded the Nobel Prize during
the Second World War, after two other British scientists, Florey
and Chain, made large-scale production of the drug possible.
However, several moulds of the genus Penicillium are
capable of producing mycotoxins which may produce some adverse health
effect. Penicillium chrysogenum, can produce the toxins meleagrin
and chrysogin (Nielsen et al., 1999)
Penicillium polonicum can produce 3-methoxy-viridicatin,
verrucosidin and verrucofortine and Penicillium brevicompactum can
produce the toxins mycophenolic acid and asperphenamate (Nielsen
et al., 1999). These mycotoxins may have possible carcinogenic effects
over long periods of time. Similarly, Penicillium expansum, Penicillium
griseofulvum and Penicillium viridicatum produce toxins which may
have longer term carcinogenic, neurotoxic or teratogenic effects.
The presence of moulds of the genus Penicillium in
the RH/temperature category C may result in long-term adverse health
effects. Moisture levels should be reduced to below 75%RH to prevent
the further growth of mould types with a lower limiting relative
humidity. The home occupant should be made aware of remedial measures
to prevent growth conditions and any existing mould should be removed.
D:
Moulds of the type Cladosporium
Cladosporium is a relatively common mould in limiting
air moisture content of around 85% relative humidity. The mould
is more common outdoors but may still be found on food, surfaces
of fibreglass duct liner, refrigerators, moist window frames, paper,
and textiles. Moulds of the genus Cladosporium are not capable of
producing mycotoxins but because the mould produces an extremely
large number of spores of a very buoyant nature it is most important
airway allergens that cause asthma and hay fever.
For immune compromised patients the presence of the
mould can cause additional problems. In these cases, skin abscesses,
the eye infection mycotic keratitis and pulmonary fungus ball have
been recorded. It may also cause corneal infections and mycetoma,
again, usually in immune compromised hosts.
The presence of moulds of the genus Cladosporium in
the RH/temperature category D is of special significance for individuals
with asthmatics or other respiratory conditions. Individuals with
depleted immune systems should be warned about the moisture/temperature
conditions. Again, moisture levels should be reduced to below 75%RH
to prevent the further growth of mould types with a lower limiting
relative humidity. Given the higher humidity levels, the home occupant
should be advised to perform remedial measures to remove the mould
colonies.
E:
Moulds of the type Ulocladium
Isolated from dead plants, cellulose materials and
found on textiles. The genus does not produce mycotoxins but
is reported to be allergenic in nature. The higher relative humidity
levels present in band E could also cause structural damage to building
materials and furniture and affect the comfort level of building
occupants. Remedial measures should be taken to drastically reduce
air moisture levels.
F:
Moulds of the type Stachybotrys
Found on very damp cellulosic materials including
wallboard, wallpaper, ceiling tiles and insulation backing.
The strain grows slowly under a gelatinous mass which often preventing
aerosolize of its spores. As a result, moulds of the type do not
compete well with other rapidly growing fungi, and require an unusually
high relative humidity or moisture content. The strain is relatively
rare compared to Penicillium and Aspergillus, and is normally only
found in homes with chronic moisture problems.
However, moulds of the genus Stachybotrys are capable
of producing one or more mycotoxins, which can have adverse effects
on even healthy individuals, and some strains of the mould are capable
of producing an extremely potent toxin. The pathogenic potential
of this mould is great and increases upon cell death, where the
mould dries and air movement can cause the spores to become airborne.
Several strains of this fungus may produce a mycotoxin
called Satratoxin H, which is poisonous by inhalation. Individuals
with chronic exposure to the toxin produced by this fungus report
cold and flu symptoms, sore throats, diarrhea, headaches, fatigue,
dermatitis, intermittent hair loss, and generalized malaise.
The toxins produced by this fungus are immunosuppressants effecting
the lymphoid tissue and bone marrow.
The concern about toxin-producing moulds of the type
Stachybotrys can be traced back to mid 1990’s America where its
presence in a Cleveland home was suspected to have caused an unusual
form of lung bleeding in its infant occupants. The original
investigation, by the U.S. Centres for Disease Control and Prevention
(CDC) suggested that homes with high humidity and Stachybotrys presence
played a role in these lung haemorrhage cases. However, after
a review of the methods used to conduct the original study, the
CDC concluded in May 2000 that a possible association between the
lung bleeding in the infants and exposure to moulds, specifically
Stachybotrys atra, could not be made. Research into the health effects
of exposure to mycotoxins produced by Stachybotrys is presently
continuing. Animals injected with the toxin exhibited symptoms of
necrosis and hemorrhage within the brain, thymus, spleen, intestine,
lung, heart, lymph note, liver and kidney. Effects by absorption
of the toxin in the human lung are known as pneumomycosis.
There can be no doubt as to the dangerous nature of
moulds of the genus Stachybotrys., especially with highly hydrophilic
types such as Stachybotrys atra and other species of high limiting
humidity. Presently there are no commercial laboratory tests currently
available that can detect mycotoxins in a building where moulds
are present, therefore the only method of preventing illness caused
by the presence of this mould species is to monitor the conditions
that limit their growth. Most people who experience the associated
health effects fully recover after identification of the cause and
subsequent removal of the mold contamination.
Additional
Service: Dust Mites
According to the American Academy of Allergy, Asthma
and Immunology (AAAAI), relative humidity levels act as limiting
growth factor for dust mites. These mites are found throughout the
home, and especially thrive in areas of high humidity and warm temperature.
Dust mites are one of the most important allergic triggers in respiratory
conditions such as asthma. Studies have shown the limiting factor
for dust mite growth is 50% relative humidity. Therefore as an additional
service for asthmatic individuals information will provided to ensure
humidity levels are maintained below 50%RH. This effectively reduces
exposure to one of the most potent allergic trigger for asthmatics.
To keep RH levels below 50% a dehumidifier will be needed. The device
consists of condensing coils through which moisture is removed from
the air. The RH monitoring service will inform the home owner how
long the dehumidifier needs to be in operation to maintain humidity
levels below the limiting humidity for dust mite growth.
Advice
for homeowners
Information will be provided to the homeowner on the
basis of measured RH and temperature conditions. If these parameters
are below the limiting RH for any mould growth, a “default” message
will be displayed on the “homeowners view” webpage informing the
occupant of the measured RH and temperature values, the maximum
safe value and that mould growth will not occur if the conditions
are maintained. If the measured parameters are above the limiting
values for mould growth, new information will be displayed informing
the occupant of the new humidity and temperature levels, and how
much these values must be decreased to reach a safe value. The service
will have four elements:
1). To advise the homeowner to undertake remedial
measures to ensure home humidity levels are below growth limiting
levels.
2). To provide information for people with respiratory
or other illnesses
3). To advise measures for removing any existing mould.
4). To dispatch a trained inspector if there is a
chronic moisture problem.
1.
Control of humidity levels.
The initial service will involve information
regarding the moisture levels in the house and what this might mean
to the customer. The service will tell the customer when the humidity
should be reduced and the remedial measures which can be undertaken.
The following measures will all help to reduce relative humidity
in the home:
· Increase air circulation, by running a fan
at or near the coldest part of the room, e.g. the window. This will
reduce convective heat transfer and moisture build up near the window.
· When weather outside is dry, increase air
circulation by opening a window and allowing air to move through
the building.
· During cooking, cover pots, vent stove bonnets
and dishwashers to the outside and drain any water.
· Wherever possible, do not leave moisture
sources such as bathwater lying. Drain after use.
· Clear up any water of liquid spillages.
· Use a dehumidifier to remove moisture from
air.
· To prevent stale, dry air, install an air-to-air
heat exchanger to vent moist air outside. This provides a reduction
of indoor humidity without a loss in heat or home efficiency at
some initial cost (Some air quality systems recover up to 97% of
the existing warmth and energy to heat incoming fresh air.)
· Reduce moisture levels in the bathroom by
running an exhaust fan during and after showers.
· Fix plumbing leaks and seepage from outside
to prevent the build-up of moisture.
· Fit windows which are better sealed from
outside conditions.
· Store clothing dry and clean to prevent the
growth of mould on clothes.
· Do not use a humidifier if humidity conditions
are over 40% RH, and use dehumidifiers and air conditioners when
levels of humidity are high.
· Increase the flow of air within your home
by opening interior doors.
· Move furniture away from walls and open cupboards
to permit air circulation in enclosed spaces.
· Reduce condensation. Fitting double or triple
glazed windows will reduce the inside surface temperature thus limiting
the formation of condensation.
· Providing walls with better insulation also
limits condensation formation.
· Place sealing around indoor light fixtures
to prevent warm, moist air rising into the attic.
· Install soffit vents to prevent attic rot.
Make sure to vents are kept clear of dirt and debris.
· Use dry sources of heat such as a gas or
electric fire.
· Dry clothes on an outside line wherever possible.
· If homeowner has a laundry room, use an extractor
fan to prevent moisture build-up.
· Check sinks and under-sink cabinets to make
sure there are no leaks.
· Insulate cold water pipes in the basement
and under-sink cabinets to prevent condensation.
· Ensure dryers and gas burning furnaces are
vented to the outside.
· Use dry sources of heat such as electric
fires or radiators.
2.
Additional Information for Susceptible individuals.
The service will provide information for the
homeowner regarding the possible growth of mould species and the
possible associated health effects, as previously discussed.
3.
Removal of Existing Mould.
The service will provide advice on remedial
measure to tackle an existing mould problem after the humidity levels
have been reduced and the moisture problem solved. In the interests
of safety, homeowners will only be advised to take remedial action
where humidity levels suitable for growth of the more dangerous
mould types have NOT been observed. Where observed levels are suitable
for growth of dangerous mould species, such as Stachybotrys atra,
over a sufficient period of time, the service will recommend the
dispatch of a trained inspector.
Additionally remedial measures for the removal
of mould can be dangerous because the homeowner may be exposed to
mould, strong detergents, and disinfectants. During cleaning, spore
counts may be 10 to 1,000 times higher than background levels because
the disturbance of mould contaminated materials causes the distribution
of spores and mould particles. For this reason the homeowner should
use a respirator for protection against the inhalation of airborne
spores. The respirator should be effective for particle removal
(e.g. an N-95 particle respirator) and good ventilation should be
maintained in the room to protect the homeowner from bleach or disinfectant
fumes. Rubber gloves, eye protection and overalls which can be cleaned
or discarded afterwards should be worn.
The information provided is as follows:
1. Using cleaning detergent directly on areas
of mould growth.
Use non-ammonia soap or detergent, or a commercial
cleaner, in hot water, and scrub the entire area that is affected
by the mould. Use a stiff brush or cleaning pad on cement-block
walls or other uneven surfaces.
2.
Rinsing cleaned items with water and drying.
Use a damp cloth to rinse any residual detergent off
the treated surface. A wet/dry vacuum cleaner can be helpful for
removing water and cleaning items.
3.
Disinfection of Contaminated Materials
Disinfectants are intended to be applied to
thoroughly cleaned materials and are used to ensure that most microorganisms
have been killed. Therefore, do not use disinfectants instead of,
or before, cleaning materials with soap or detergent. Removal of
mould growth from nonporous materials usually is sufficient.
After thoroughly cleaning and rinsing contaminated
materials, a solution of 10% household bleach (1½ cup household
bleach per gallon of water) can be used as a disinfectant.
Using bleach straight from the bottle is less
effective than diluted bleach.
Keep the disinfectant on the treated material
for the prescribed time before rinsing or drying; typically 10 minutes
is recommended for a bleach solution
When disinfecting a large structure, make sure that
the entire surface is wetted (e.g, the floors, joists, and posts).
Properly collect and dispose extra disinfectant
and runoff.
WARNING: Bleach and disinfectant
should be used only when necessary and
should be handled with caution. Bleach should never
be added to ammonia; toxic fumes may be produced.
Wear gloves, mask and eye protection when using
disinfectants
Bleach fumes can irritate the eyes, nose, and
throat, and damage clothing and shoes. Make sure working areas are
well ventilated.
4. Clearing up afterwards.
Discard any loose porous materials where mould
growth cannot be removes or has become ingrained into the material
(e.g, ceiling tiles, sheetrock, carpeting, and wood products).
Bag and discard mouldy items; if properly enclosed,
items can be disposed with household refuse.
Ensure humidity levels are kept down or situate
a heater near effected area to dry out the treated materials. Dry
affected areas for 2 or 3 days.
Visually inspect the wall interior after it
has dried and remove any mould-contaminated materials.
4.
Warning for high moisture levels.
In the presence of high levels of moisture over a
long period of time, a warning message will appear to inform the
home occupant to contact a trained inspector if mould growth is
observed.
Conclusion
It is the group’s opinion that the only effective
way of avoiding adverse health effects due to mould growth in the
home is by continual monitoring. Although PM10 monitoring would
give a better indication of indoor air quality, the price and size
of the sensors means indirect monitoring through a humidity sensor
is a more viable health service. Along with providing relative humidity
information and possible health effects, the service will also enable
the homeowner to prevent the conditions for mould growth and remove
existing mould. The service will provide additional information
regarding the health effects for people with existing health problems,
and the subsequent remedial measures.
fig
1