Respiratory and Allergic Health Effects of Dampness, Mold, and Dampness-related Agents

A Review of the Epidemiologic Evidence

Mark J. Mendell; Anna G. Mirer; Kerry Cheung; My Tong; Jeroen Douwes


Environ Health Perspect. 2011;119(6):748-756. 

In This Article


Based on the material reviewed here, there is sufficient evidence of an association between indoor dampness-related factors and a wide range of respiratory or allergic health effects (Table 3), including asthma development, asthma exacerbation, current asthma, ever asthma, dyspnea, wheeze, cough, respiratory infections, bronchitis, allergic rhinitis, eczema, and upper respiratory tract symptoms. There is suggestive evidence of associations with health effects for several non-culture-based measurements related to fungi and bacteria in dust, although some of these associations seem equivocal. No evidence suggests protective effects of evident dampness and mold. Mechanisms seem likely to be both allergic and nonallergic. Available quantitative meta-analyses have estimated consistently and significantly increased risks for multiple outcomes associated with dampness or mold, including OR ranges of 1.30–1.75.

Substantial increases in a number of important respiratory health outcomes, including a 50% increase in current asthma, are associated with dampness-related risk factors in residences (Fisk et al. 2007). These estimates, based on limited data, broad lumping of diverse risk factors, and multiple unverified assumptions, should be interpreted cautiously; however, they indicate that dampness-related risk factors may contribute substantially, but preventably, to the burden of respiratory disease.

In agreement with the IOM report (2004), we consider that there is not sufficient epidemiologic evidence of a causal relationship for any of the reviewed health outcomes, although for asthma exacerbation in children we consider the evidence strongly suggestive of causality by dampness-related agents. Although it is plausible that microbial exposures may play a causal role, specific causative agents have not been established. In fact, limited and inconsistent evidence suggests that moderate exposures to certain microbial agents, especially at early ages, may prevent allergies and allergic asthma.

Based on available evidence, the presence of dampness, water damage, visible mold or mold odors or a history of water damage provides more reliable indicators of dampness- or mold-related health risks than do current quantitative microbiologic assessments. As reduction of indoor dampness and mold is likely to have benefits for respiratory and allergic health of occupants, this level of knowledge should guide practical prevention and remediation now. Still, available research does not yet indicate the amount of water damage, mold, or mold odor meriting concern nor document the relative magnitude of health benefits from different environmental remediations.

Although Williamson et al. (1997) published findings of strong, dose-related associations of asthma severity with systematic moisture measurements in walls 13 years ago, research use of quantified dampness metrics has not been reported since. Future research, generally, should develop objective metrics for dampness-related and microbial (or nonmicrobial) risk factors that predict health effects. This will help in identifying specific causal dampness-related agents and characterizing exposure–response relationships.

Challenges to progress include the wide variety of currently plausible microorganisms (fungi, bacteria, amoebae/protozoans) and microbial components and products eligible to be causal factors; the potentially nonmonotonic effects of some of these components (e.g., glucans and endotoxin); the potential synergistic actions of some organisms, including actinomycetes and amoebae; the possible involvement of nonbiological, chemical agents released from damp indoor materials; and the modification of microbial effects by human age at exposure or by genetic or other host susceptibility factors. However, although their effectiveness may ultimately be improved, prevention and remediation actions to reduce indoor dampness are important and urgently needed in a large proportion of our building stock. These measures are likely to significantly reduce the current global burden of respiratory and allergic disease.


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