Indoor Air Quality

8. Why is dampness in buildings a health concern?

The SCHER opinion states:

3.3.3. Concerns in relation to building dampness/moisture and microbial growth

Adverse health effects associated with building dampness and moisture problems have been reported since the 1980ies but are a poorly understood phenomenon. The available data about details of this subject have recently been reviewed and summarised as a panel work (IOM 2004).

An association has been shown in numerous epidemiological studies in different environments, and in a number of countries (Bornehag et al., 2001, 2004b). Intervention studies have indicated that renovation of the building either decreases or abolishes the symptoms (Sudakin 1998, Meklin et al., 2005). Furthermore, a dose-response relationship between the extent of damage and health effects has been shown (Haverinen 2002). Dampness and moisture problems in buildings are common in countries where comprehensive studies have been done, and are likely to be an underestimated indoor air problem in EU and should be evaluated more thoroughly.

The associated adverse health effects range from irritation of mucous membranes, respiratory symptoms and infections to permanent diseases, such as asthma and allergy (IOM 2004). However, only a fraction of the symptoms appear to be caused by IgE- mediated allergy, allergic alveolitis (hypersensitivity pneumonitis) or organic dust toxic syndrome, and other, still poorly known patho-physiological mechanisms are involved. General symptoms, such as fever, fatigue, headache and difficulties to concentrate have also been reported. Clusters of cases of sarcoidosis, rheumatoid diseases as well as pulmonary haemorrhage among infants have also been associated with indoor dampness (Nevalainen and Seuri, 2005).

The majority of the health effects associated with dampness and moisture of buildings are those of the respiratory system. Therefore, it is likely that the major route of the exposure to the causative agents is via the airways. There are many types of emission from a microbial growth e.g., particles of microbial origin including spores, vegetative cells and submicron-size fragments (Gorny, 2004) that carry structural components, such as endotoxin and 1,3-beta-glucan, and non-volatile secondary metabolites, e.g. toxins (Croft et al., 1986). Volatile organic compounds emitted from microbial growth include those that are known as odour of mould. Dampness and moisture may initiate chemical degradation of material which may contribute to emissions of degradation products into the indoor air and inadequate ventilation may increase the level (Bornehag et al., 2005b).

Although the association between moisture problems and adverse health effects has been demonstrated, the causative agents/exposures are not defined. This is likely to be due to great complexity and variability of the contributing factors but also due to lack of basic knowledge. Respiratory inflammation, the most typical symptom, has been verified in laboratory animals by a few microbes typical for moisture problems (Jussila et al., 2001, Huttunen et al., 2003). Still, even in those cases, the principal components causing the effects are not known.

Dampness or moisture may accumulate into the building structures or finishing materials via leaks in roofs, windows or piping; due to condensation as a result of insufficient ventilation or faulty construction, or moisture from the ground may penetrate into the building structure by capillary movement. Attempts to improve the energy efficiency of the building e.g. by adding thermal insulation may alter the functioning of the construction, if not done properly. This may lead to moisture and mould problems. Excess water stimulates microbial growth, usually fungi and bacteria, and in a more advanced damage, also protozoa, nematodes and higher organisms such as mites and insects. The substrate (material) in question and its moisture content regulate the microbial profile that will develop, and also their toxicity (Hyvärinen et al., 2002, Roponen et al., 2001, Murtoniemi et al., 2001). Many of the bacteria and fungal species detected in damp environments are the same as detected in “normal” indoor air but their concentrations may be higher. There are also species which typically exist in water damaged environments (indicator species of the dampness problem). Microbial diversity in various dampness situations varies and one water damaged site (environment) only poorly predicts another (Nevalainen and Seuri, 2005). This may suggest that all dampness is not equally harmful. There is also likely large individual variability in sensitivity to react to those exposures, depending on e.g. the immunological status.

SCHER considers that the adverse health effects associated with building dampness and moisture are a concern. The association between building dampness and the common health effects has been documented, however several other questions, indicated as data gaps in answer to Question 2, are open and need further research before the wideness and seriousness of the problem at EU level can be assessed.

Source & ©: SCHER,  Opinion on risk assessment on indoor air quality (2007),
3.3.3. Concerns in relation to household-chemicals and other products
(e.g. decorating materials, cleaners, furnishing, etc.), p.20-21