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

Disclosures

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

In This Article

Methods

The online database PubMed (National Library of Medicine 2010) was searched using three groups of keywords such as dampness, damp, "water damage," moisture, humidity, fungi, fungus, mold, mould, bacteria, or microorganisms, crossed with health, asthma, allergy, eczema, wheeze, cough, respiratory, "respiratory infection," lung, skin, nasal, nose, "hypersensitivity pneumonitis," alveolitis, bronchial, hypersensitivity, or inflammation and with building, house, home, residence, dwelling, office, school, or "day-care center." A similar search was run in the ISI/Web of Knowledge database (Thomson Reuters 2010). We identified additional publications from reference lists and personal databases. Some indoor exposures/conditions were not included, for example, humidity, mattress moisture, and dust mites.

Inclusion of a primary study required the following characteristics:

  • Publication in a peer-reviewed journal by November 2009

  • Reporting of original data from one of the following study designs: intervention (quasi-experimental intervention), prospective (prospective cohort), retrospective (retrospective cohort or nested case–control), or cross-sectional (cross-sectional or prevalence case–control)

  • No minimum study size, but if exposure was characterized only at the building level, inclusion of > 10 buildings

  • Including risk factors related to dampness or microbiologic organisms/components/products, other than allergens (dust mites, cockroaches, mice)

  • Including allergic or respiratory health effects

  • Providing adequate control, in study design or analysis, of selection bias and confounding from key variables: sex, smoking (active in adults, passive in children), and socioeconomic status (SES; control for SES not required if SES shown not to confound in study, if adjusted for race when race highly correlated with SES, if study conducted within specific occupational groups, or if study from Nordic countries or Holland).

We gave primary consideration to associations between specific health outcomes (e.g., wheeze) and one or more qualitative assessments of indoor dampness or mold (e.g., visible dampness, visible mold, water damage, or mold odor), with the latter grouped for review. We refer to this set of factors collectively as evident dampness or mold, qualitatively assessed dampness or mold, or simply dampness or mold. Each study generally reported multiple findings (for example, four findings from a study reporting estimates for associations between visible dampness and daytime wheeze, visible dampness and nighttime wheeze, mold odor and daytime wheeze, and mold odor and nighttime wheeze). Based on all currently available evidence, including studies reviewed in the IOM report, new studies included in this review, and findings from available quantitative meta-analyses, we drew conclusions about associations between specific health outcomes and qualitatively assessed dampness or mold (excluding quantitative assessments of microbiologic factors). In "Results," we generally refer to all ratio estimates of effect as odds ratios (ORs), although a few studies used other types of ratio estimates.

In this review we classified strength of evidence using the same categories as the IOM review on dampness and health (IOM 2004) (box ES-1, p. 8): sufficient evidence of a causal relationship, sufficient evidence of an association, limited or suggestive evidence of an association, and inadequate or insufficient evidence to determine whether an association exists. For each relationship considered, we classified the evidence using professional judgment on its persuasiveness, based on reported findings plus the strength, quality, diversity, and number of studies. Findings from quantitative meta-analyses were also considered. We placed increasing weight in the review on studies of stronger design. The strongest epidemiologic evidence was considered to come from individually randomized controlled experimental/intervention trials that added or removed risk factors. Studies considered next strongest were prospective (cohort), followed by retrospective (cohort or nested case–control), observational studies. We considered cross-sectional observational studies (including prevalence case–control studies) to provide the weakest evidence included. A set of strongly designed human studies of different designs and in different populations, with findings generally consistent in direction and magnitude, especially if magnitudes of effect were large or dose–response relations were found, was considered to provide the most persuasive overall evidence.

We drew separate conclusions, more preliminary because evidence was sparse, about associations between specific health outcomes and specific quantitatively assessed microbiologic factors. For findings on associations between a specific outcome and a specific measured indoor microbiologic factor, our criteria for evidence suggestive of associations required at least 80% consistency of estimates either ≤ 1.0 or > 1.0 (with no minimum change from the null required) among at least five estimates available from three or more studies. This rough tally of findings above or below the null did not consider magnitude of effects, precision, statistical significance, study design, or age of subjects.

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