WHO Findings and Recommendations Re: Damp Indoor Spaces and Health

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_http://www.euro.who.int/Document/E91146.pdf_

(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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