Hydrophilic Fungi and Ergosterol Associated with Respiratory Illness in a Water-Damaged Building

Ju-Hyeong Park; Jean M. Cox-Ganser; Kathleen Kreiss; Sandra K. White; Carol Y. Rao

Disclosures

Environ Health Perspect. 2008;116(1):45-50. 

In This Article

Abstract and Introduction

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 postoccupancy 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.

Mold is ubiquitous in normal indoor and outdoor environments; thus, some exposure is inevitable in everyday life. However, exposure to increased levels of mold and other microbial agents has been implicated in diseases associated with damp indoor environments (Menzies and Kreiss 2006; Park et al. 2006). In the absence of indoor amplification, the fungal profiles inside buildings should be similar to those outdoors (Flannigan and Miller 2001). Increased moisture levels due to water intrusion can support mold growth and may change the profile of fungal populations in a building. Hydrophilic (water-loving) fungi requiring ≥ 0.9 water activity (Aw ; the amount of free or available water in substrates) will overgrow mesophilic (0.8 ≤Aw < 0.9) and xerophilic fungi (Aw < 0.8) in damp conditions (Flannigan and Miller 2001; Grant et al. 1989). The presence of hydrophilic fungi is considered an indicator of building dampness (Flannigan and Miller 2001), yet quantitative measures of hydrophilic fungi in damp buildings have not had been studied in relation to health effects.

The analytical method most frequently applied for fungi, a culture technique, is not likely to measure the relevant microbial exposures accurately, because any selected medium grows only a small proportion of the viable spores and because culture counts do not account for nonviable spores and fungal fragments. However, ergosterol, a principal sterol in the fungal membrane, has been suggested as a good measure for fungal biomass (Newell 1994; Sebastian and Larsson 2003; Szponar and Larsson 2000) since it is analyzed by a chemical technique which measures viable and nonviable spores and fungal fragments. However, only a few researchers have attempted to measure ergosterol in environmental samples for assessing exposure to fungi in epidemiologic studies (Dales 1998; Dales et al. 1999; Dharmage et al. 2001, 2002; Matheson et al. 2005; Mendell et al. 2002). More research using ergosterol measurements for fungal exposure assessment would be useful to better understand the association of fungal exposure with health.

In this study we focused on examining associations of hydrophilic fungi and ergosterol with respiratory health outcomes among employees in a 20-story office building in the northeastern United States. Within a few months of building occupancy in 1994, employees perceived new-onset respiratory conditions to be building-related and complained of a further increase in symptom severity and frequency beginning in the fall of 2000. Sentinel cases of postoccupancy-onset asthma, hypersensitivity pneumonitis (HP), and sarcoidosis had been diagnosed. A building-wide self-administered questionnaire survey in September 2001 (67% participation rate; 888 of 1,327) documented an excess of respiratory symptoms and asthma prevalence, and a 7.5-fold increased incidence density of adult posthire-onset asthma (Cox-Ganser et al. 2005; Park et al. 2006) compared with preoccupancy incidence.

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