Moulds and Health
Review by Independent Consultant George McGill
Part 2 Remediation-
What do we need to do about moulds?
part 1 of this series of articles we considered the nature of moulds, and some
of the health problems that can be (but are not necessarily) caused by moulds.
It’s important to remember that there are a great many substances within the
air we breathe, both within buildings and outside. Mould spores, mould VOC’s (volatile organic compounds) and other
fragments that might be derived from moulds are only one very small part of
this extremely complex environmental mix.
is well understood that some moulds can (but don’t always) produce harmful substances
as well as beneficial ones. There is a great deal of information about this.
Most of it has been obtained from the food industries, from studies of plant
pathology and crop diseases, and from medical mycologists and microbiologists who
study the effects of fungal infections on health, and manufacture antibiotics
from fungal metabolites and their chemical analogues.
fungi are so widespread in the environmment it is practically impossible to
exclude fungal contamination from foodstuffs. As a result. many countries have
established what are considered to be safe levels of contamination. For example,
for Aflatoxin B1, a well known and very potent fungal toxin, and
carcinogen found in fungal contaminated peanuts, these were internationally set
at around 5 microgrames per kilogram of material. ( 5 *10-6
g/Kg) (Commission of European
is quite a different consideration from fungal spores that might be blowing
around in the air, and where fungal toxins contained in spores might be
inhaled. For example a fungal spore might contain 3 femtograms of a toxic
substance (3*10-18 Kg). Miller
R.V; Martinez-Miller, C; Bolin, V A. AeroTech
Monitor, Vol. 3 No. 1, 2000.This an extremely small amount and so the exposure, even when
large numbers of spores are present is (undetectably) low.
most practical situations the quantity of fungal spores present within a
building is very low by comparison (100 – 10000 spores or cfu/m3)
and not close (by a factor of billions) to a level that would be necessary to
deliver a toxic dose. They are also usually lower than the numbers present in
the air outside.
are of course issues other than toxicity, and allergic responses attributed to
moulds are experienced by sensitive
individualls. These are the same responses that might arise in sensitive
individuals exposed to pollen, dust, house mite faeces or animal hair. If it becomes known that a sensitive
individual might suffer harm from such environmental conditions then
professional medical advice should be immediately sought by those individuals.
those involved with moulds within buildings, the levels of harmful substances
produced by moulds growing on wallpaper, plasterboard and domestic items are
many many times less than the levels
that might accumulate within contaminated foodstuffs. Consequently, the risk of
harm is is very much reduced.
moulds can be a problem, and steps must be taken to minimise their presence, and to remove them when they
Prevention is Better than
All moulds require moisture, free moisture, not water that is a structural component of the substrate, or the natural or hygroscopic moisture a material might absorb from its environment. There is always a dampness problem responsible for mould growth in a building and this dampness problem needs to be the primary focus of any investigation.
Moulds vary in their requirements for moisture. Some will grow and develop at high levels of moisture, others, the xerophilic types require less.
It must be established therefore, what are the levels of free moisture and where they came from.
In cases of flood damage, or where there is a single incident like a burst pipe, the source of moisture might be obvious. If this is dealt with quickly and efficiently, a mould problem need not arise.
In most cases in the UK the problems of mould are related to indoor climate issues of high internal humidity and condensation. The relationship between temperature, relative humidity and vapour pressure must be clearly understood. A thorough and detailed moisture examination of the building must be carried out to establish what all the sources of moisture are and how they can be eliminated and the building quickly dried out.
When the sources of moisture have been removed then so has most of the problem. When moisture conditions have returned to normal then conditions for fungal growth will no longer be present, and the mould will not recur.
If it is not possible, for whatever reason, to eliminate the source of moisture then the mould problem will recur. This often in encountered in houses that have a persistent condensation problem.
Digital dataloggers are now available at low cost. These allow monitoring of internal climate conditions continuously, and enable an assessment of the type of occupancy (dry moist or wet) to be made with reference to the British Standard on Condensation BS5250. Such an analysis of internal conditions allows an informed decision to be made about the most effective way to alter the internal environment. It is often the case that guidance is provided to tenants that may be wholly inappropriate to the individual conditions within that property. As a result the dampness problems persist, and the mould grows back.
How should the clean-up
The approach taken will depend on what caused the problem, and what damage has been done by the sources(s) of moisture. In some instances, for example in the aftermath of flooding, plasterboard and furnishings may have become so damaged that they need to be removed and replaced.
In other instances the damage may be more limited, and after drying they might be retained after cleaning.
Since the first priority will always be to eliminate the source of moisture, what ought to be achieved after cleaning up is a clean decorative surface. There are a number of ways that this can be done, and it is not normally necessary to use anything other than what would commonly be found under the typical kitchen sink.
Whatever is used one must always follow the manufacturers’ guidance and it is never a good idea to mix cleaning products since this can sometimes result in toxic gases being produced.
In some cases it will not be practicable to completely eliminate the source of moisture. In such cases we may wish to supplement our cleaning with a fungicidal paint. There are a number of products available which can assist.
In practice it is sensible to follow a step by step approach. This will help in selecting the most appropriate procedure.
Step 1 Identify and eliminate the source of
There are six principal sources of moisture to consider:
Direct Rain Penetration
Faulty Rainwater goods
Rising Dampness and Hygroscopic Salts
Lateral Water Ingress and Flooding
Condensation and High Internal Humidity
It is important to consider that there may be more than one source of moisture present at the same time, and that all sources must be dealt with.
Step 2 Determine the extent of water damage.
This requires a little investigative work, some knowledge of building construction, and the careful use of a moisture meter., together with other diagnostic tools, for example dataloggers.
Step 3 Assess
the materials damaged and determine which require disposal and which can be
retained after drying.
Depending on the source of moisture some materials and building finishes may have become contaminated or structurally damaged such that they will require to be replaced.
Step 4 Select an appropriate cleaning
This might involve vacuum cleaning, household detergents, bleach, steam cleaning or the use of a commercial mould removing product containing a fungicide.
Step 5 Monitor to ensure normal conditions
have been restored.
This will involve repeating the steps taken in step 2 together with monitoring the internal air conditions, preferably over a continuous period using dataloggers.
This type of systematic approach, especially towards identifying the source or sources of moisture, will help to determine the most appropriate procedure for removing the mould, and datalogger monitoring will help in ensuring the success of the procedure adopted.
What are the
relative merits of the cleaning procedures?
Having established the source(s) of moisture, corrected them, implemented a drying regime and identified the contaminated surfaces to be remediated, a choice must be made about how to clean up the contaminated materials and surfaces.
The procedure adopted, including the materials and methods will normally be determined by the location, the extent of the contamination and the safe working practices decided.
There is no particular risk associated with mould clean up in the vast majority of situations however the CoSHH regulations require a risk assessment to be made and appropriate steps taken to control any risks involved. In most instances this will require that any individuals who might be harmed by any of the operations involved are removed or protected until the risks are no longer present.
In some instances it may be necessary to remove sensitive individuals to a place of safety to ensure they come to no harm, either from the fungal spores or the product about to be used. Similarly it may be necessary to protect operatives, using suitable personal protective equipment.
For contaminated furnishings:
is effective for cleaning contaminated items such as clothes and curtains. Ordinary household detergents are sufficient for this purpose. However some types of mould produce cellulose degrading enzymes, and these can destroy the fabrics on which they grow. Such affected items will normally need to be replaced in whole or in part.
will be required for heavier household items like upholstery and carpets. A decision will be required to be made whether such cost is justified compared to the cost of replacement.
For contaminated surfaces:
can be an effective way of removing fungal spores mycelial fragments and general dust from contaminated areas. However it is essential that a suitable filter is incorporated otherwise the spores and dust will simply be distributed about the air in which the appliance is being used.
Soap or detergent and water
will effectively remove lose mould spores and mycelial fragments from contaminated surfaces. A little scrubbing might be required depending on the type of surface.
Bleach and water
is an effective way of removing surface moulds, and leaves a clean and partially (not completely) sterile surface. However bleach is an irritant. Care should be taken to protect skin and eyes, and to ensure that good ventilation is maintained.
will effectively clean spores and mycelial fragments from affected surfaces. However these are pesticide products and must be used in accordance with manufacturers’ labelled instructions.
is a very effective way of removing and killing mould spores and mycelial fragments from surfaces.. However the effectiveness depends on the temperature of the steam, which will depend on the quality of the apparatus. Not all are equally effective, and the depth of effective penetration below the surface is low.
No matter what cleaning procedure is adopted, if the conditions for mould growth return then the mould will return. None of the cleaning procedures will provide a long-term preventative solution to mould growth.
It can be difficult to maintain environmental conditions that prevent mould growth, especially in buildings that have a long-term problem with condensation or high internal humidity. Many buildings in the UK are affected by condensation and high internal humidity. This seems likely to continue and will perhaps increase as a result of recent large increases in fuel prices.
There are a number of positive pressure air management systems currently being marketed that operate by introducing dry warm air to the internal environment, allowing the humid internal air to be deposited outside. These have the potential to be successful provided they have sufficient capacity to deal with the individual conditions within which they are installed.
It is normally beneficial to monitor the internal conditions before and after installation to ensure that success is achieved.
In an environment where it has proved difficult to sufficiently control the conditions for moulds, then it may be appropriate to apply a paint containing a fungicide. Some products have been reported to provide a clean decorative surface for a number of years, even in a persistently humid environment.
are a common problem in dampness-affected buildings, and because there might be
a potential for health-related problems for some, it is important to deal with
them quickly and in a way that minimises the risk to anyone who might come into
contact with them, especially at higher than normal levels.
who would like to read more about the subject are encouraged to read the World
Health Organisation Report published in 2009.
can be downloaded for free from:
George McGill PCA Independent Consultant
35 Cleveden Rd
Glasgow G12 0PH