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

Abstract and Introduction


Objectives: Many studies have shown consistent associations between evident indoor dampness or mold and respiratory or allergic health effects, but causal links remain unclear. Findings on measured microbiologic factors have received little review. We conducted an updated, comprehensive review on these topics.
Data sources We reviewed eligible peer-reviewed epidemiologic studies or quantitative meta-analyses, up to late 2009, on dampness, mold, or other microbiologic agents and respiratory or allergic effects.
Data extraction: We evaluated evidence for causation or association between qualitative/subjective assessments of dampness or mold (considered together) and specific health outcomes. We separately considered evidence for associations between specific quantitative measurements of microbiologic factors and each health outcome.
Data synthesis: Evidence from epidemiologic studies and meta-analyses showed indoor dampness or mold to be associated consistently with increased asthma development and exacerbation, current and ever diagnosis of asthma, dyspnea, wheeze, cough, respiratory infections, bronchitis, allergic rhinitis, eczema, and upper respiratory tract symptoms. Associations were found in allergic and nonallergic individuals. Evidence strongly suggested causation of asthma exacerbation in children. Suggestive evidence was available for only a few specific measured microbiologic factors and was in part equivocal, suggesting both adverse and protective associations with health.
Conclusions: Evident dampness or mold had consistent positive associations with multiple allergic and respiratory effects. Measured microbiologic agents in dust had limited suggestive associations, including both positive and negative associations for some agents. Thus, prevention and remediation of indoor dampness and mold are likely to reduce health risks, but current evidence does not support measuring specific indoor microbiologic factors to guide health-protective actions.


Dampness and mold exposures in buildings are common, with estimates ranging from 18% to 50% of buildings (Gunnbjornsdottir et al. 2006; Mudarri and Fisk 2007). A large number of studies in many geographical regions have found consistent associations between evident indoor dampness or mold and respiratory or allergic health effects in infants, children, and adults [Institute of Medicine (IOM) 2004; World Health Organization (WHO) Europe 2009]. A review by the IOM (2004) reported documented associations, but not documented causal relationships, between indoor dampness and upper respiratory tract symptoms, cough, wheeze, and asthma symptoms in sensitized persons, but not for asthma development. A more recent review by WHO up to 2007 expanded the observed associations to include asthma development, current asthma, dyspnea, and respiratory infections (WHO Europe 2009). Associations were found in both atopic and nonatopic individuals. Other published reviews or opinion pieces on this topic are available (e.g., Bornehag et al. 2004; Douwes 2005; Mudarri and Fisk 2007).

The consistent associations between evident dampness or mold and health may represent underlying causal relationships between fungal exposures and health. However, conventional quantitative measurements of fungi or other microbiologic exposures, such as counts of culturable airborne fungi, have shown less consistent associations with health effects than have qualitative assessments of visible dampness or water damage, visible mold, or mold odor. Thus, although a causal role for microbiologic exposures is plausible and likely, the evidence for this is still weak (Douwes and Pearce 2003). This is likely attributable in part to the lack of valid exposure assessment methods for the still unknown causal agents, microbial and possibly nonmicrobial, that increase with dampness and directly cause adverse respiratory and allergic effects.

Much additional epidemiologic research on qualitative and quantitative assessments of dampness and dampness-related agents has become available in the last few years. The present review combines findings of the IOM review of findings up to 2003 (IOM 2004) and a new assessment of later published studies. In this review we provide a) an updated, comprehensive review of available epidemiologic evidence on qualitative assessments of dampness or mold factors, and b) a new synthesis of evidence on quantitative measurements of microbiologic factors. Earlier work on this review (summarizing literature through 2007) was originally done to support the WHO Guidelines for Indoor Air Quality related to dampness and mold (2009).


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