Background: Damp building–related respiratory illnesses are an important public health issue. Objective: We compared three respiratory case groups defined by questionnaire responses [200 respiratory cases, 123 of the respiratory cases who met the epidemiologic asthma definition, and 49 of the epidemiologic asthma cases who had current physician-diagnosed asthma with post-occupancy onset] to a comparison group of 152 asymptomatic employees in an office building with a history of water damage. Methods: We analyzed dust samples collected from floors and chairs of 323 cases and comparisons for culturable fungi, ergosterol, endotoxin, and cat and dog allergens. We examined associations of total fungi, hydrophilic fungi (requiring water activity ≥ 0.9), and ergosterol with the health outcomes using logistic regression models. Results: In models adjusted for demographics, respiratory illnesses showed significant linear exposure–response relationships to total culturable fungi [interquartile range odds ratios (IQR-OR) = 1.37–1.72], hydrophilic fungi (IQR-OR = 1.45–2.19), and ergosterol (IQR-OR = 1.54–1.60) in floor and chair dusts. Of three outcomes analyzed, current asthma with postoccupancy physician diagnosis was most strongly associated with exposure to hydrophilic fungi in models adjusted for ergosterol, endotoxin, and demographics (IQR-OR = 2.09 for floor and 1.79 for chair dusts). Ergosterol levels in floor dust were significantly associated with epidemiologic asthma independent of culturable fungi (IQR-OR = 1.54–1.55). Conclusions: Our findings extend the 2004 conclusions of the Institute of Medicine [Human health effects associated with damp indoor environments. In: Damp Indoor Spaces and Health. Washington DC:National Academies Press, 183–269] by showing that mold levels in dust were associated with new-onset asthma in this damp indoor environment. Hydrophilic fungi and ergosterol as measures of fungal biomass may have promise as markers of risk of building-related respiratory diseases in damp indoor environments.

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Almost all modern buildings experience at least minor, and sometimes serious, water damage during their life span. Excess moisture in buildings becomes a critical factor for mold (fungal) proliferation in nutrient-rich environments. As a result, building occupants may be exposed to increased levels of microbial agents such as fungal spores, cell fragments, cell wall components, or toxins. Such exposures may result in various diseases and symptoms, both respiratory and non-respiratory. Respiratory health complaints are common in damp buildings and have been more thoroughly studied than non-respiratory complaints. Respiratory diseases and symptoms which may be produced by exposure to indoor fungi include asthma development, exacerbation of asthma, hypersensitivity pneumonitis, cough, wheeze, dyspnea (shortness of breath), nasal and throat symptoms, and respiratory infections. In addition to these illnesses, rhinosinusitis and sarcoidosis in water-damaged building occupants are also drawing more scientific attention. In this article, we explore the evidence for adverse effects of fungal exposure on respiratory health in damp indoor environments and potential disease mechanisms related to the exposure.