http:// www. euro. who.int /Document /E91146 . pdf
Summary of the health risk evaluation
1. Sufficient epidemiological evidence from studies
conducted in different countries and climatic conditions
shows that occupants of damp or mouldy buildings, both
homes and public buildings, are at increased risk of
experiencing respiratory symptoms, respiratory infections
and exacerbations of asthma. Some evidence suggests an
increased risk of developing allergic rhinitis and asthma.
Although not many intervention studies are available, their
results show that remediation of dampness problems leads to
a reduction in adverse health outcomes.
2. There is clinical evidence that exposures to moulds and
other dampness-related microbial agents increase the risk
of rare conditions, such as hypersensitivity
pneumonitis/allergic alveolitis, chronic rhinosinusitis and
allergic fungal sinusitis.
3. Toxicological evidence in vivo and in vitro supports
these findings by showing diverse inflammatory and toxic
responses after exposure to specific microorganisms
isolated from damp buildings, including their spores,
metabolites and components.
4. While groups such as atopic and allergic individuals are
particularly susceptible to exposures to biological and
chemical agents in damp indoor environments, adverse health
effects have also been widely demonstrated in non-atopic
populations.
5. The increased prevalence of asthma and allergies in many
countries increases the number of people susceptible to the
effects of dampness and mould in buildings.
6. The prevalence of indoor dampness ranges widely within
and among countries, continents and climate zones. It is
estimated to be in the order of 10–50% of the indoor
environments in Europe and North America, as well as in
Australia, India and Japan. In some specific settings, such
as river valleys or coastal areas, conditions of dampness
are substantially higher than national averages.
7. The amount of water available on/in materials is the
most important factor triggering the growth of
microorganisms, including fungi, actinomycetes and other
bacteria.
8. Microorganisms in general are ubiquitous in all general
environments. Microbes propagate rapidly whenever water is
available. The dust and dirt normally present in most
indoor spaces provide sufficient nutrients to support
extensive microbial growth. While mould growth is possible
on all materials, appropriate material selection is
nevertheless important to prevent dirt accumulation,
moisture penetration and mould growth.
9. Microbial growth may result in elevated levels of
spores, cell fragments, allergens, mycotoxins, endotoxins,
ß-glucans, and microbial volatile organic compounds (MVOCs)
in indoor air. The causative agents of adverse health
effects have not been conclusively identified, but
excessive levels of any of these in the indoor environment
indicates a potential health hazard.
10. Microbial interactions and moisture-related physical
and chemical emissions from building materials may also
play a role in dampness-related health issues.
11. Building standards and regulations on comfort and
health do not sufficiently emphasize requirements to
prevent and control excess moisture and dampness.
12. Besides occasional events – such as water leaks, excess
rain, floods, etc. – most moisture enters buildings through
incoming air, including that infiltrating though the
envelope, or is due to occupants’ activities.
13. Allowing surfaces to become cooler than the surrounding
air may result in unwanted condensation. Thermal bridges
(such as metal window frames), inadequate insulation and
unplanned air pathways, or cold water plumbing and cool
parts of air conditioning units can result in surface
temperatures below the dew point of the air that contribute
to dampness problems.
14. The problem of excess moisture and dampness can be
tackled by controlling the quality of the building envelope
regarding air infiltration, exfiltration, and pathways of
water intrusion, by ensuring adequate thermal insulation
and by avoiding condensation indoors through the control of
moisture sources and of temperature, humidity and velocity
of the air in the proximity of the surfaces.
Recommendations
1. Persistent dampness and microbial growth on interior
surfaces and in building structures
should be avoided or minimized, as they may lead to adverse
health effects.
2. Indicators of dampness and microbial growth include the
presence of condensation on
surfaces or in structures, visible mould, perceived mould
odour and a history of water
damage, leakage or penetration. Thorough inspection and –
if needed – appropriate
measurements may be used to confirm indoor problems related
to moisture and microbial
growth.
3. Currently, the relationship between dampness, microbial
exposure and health effects cannot
be precisely quantified, so no quantitative health-based
guideline values or thresholds can be
recommended for acceptable levels of specific microorganism
contamination. Instead, it is
recommended that dampness and mould-related problems be
prevented. When they occur,
they should be remediated because of the increased risk of
hazardous microbial and chemical exposures.
4. Well-designed, -constructed and -maintained building
envelopes are critical to the prevention and control of
excess moisture and microbial growth by avoiding thermal
bridges and preventing intrusion by liquid or vapour-phase
water. Management of moisture requires proper control of
temperatures and ventilation to avoid high humidity,
condensation on surfaces and excess moisture in materials.
Ventilation should be distributed effectively in spaces,
and stagnant air zones should be avoided.
5. Building owners are responsible for providing a
healthful workplaces or living environments free of
excessive moisture and mould problems by ensuring proper
building construction and maintenance. Occupants are
responsible for managing water use, heating, ventilation,
appliances, etc. in a proper manner that does not lead to
dampness and mould growth.
6. Local recommendations in different climatic regions
should be updated to control dampness mediated microbial
growth in buildings and to ensure the achievement of
desirable indoor air quality.
7. Dampness and mould may be particularly prevalent in
poorly maintained housing for low income people.
Remediation of conditions related to adverse exposures
should be given priority to prevent additional
contributions to poor health in populations already living
with an increased burden of disease.
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