Evaluation of individual-based and group-based exposure estimation of microbial agents in health effects associated with a damp building

Abstract

We evaluated attenuation in linear associations between microbial exposure and respiratory symptoms occurring when individual measurements of microbial agents were used for estimating employees' exposure compared with group means. Symptoms, which improved when away from the building (building-related, BR), and measurements of culturable fungi, ergosterol, and endotoxin in floor dust were obtained between 2001 and 2007 from four cross-sectional studies on occupants of a water-damaged building. We compared odds ratios from longitudinal health effect models using individual measurements at employees' workstations with those using floor (group) means. Estimated odds for BR respiratory symptoms in group-based analyses increased by 2 to 5 times compared with those from individual-based analyses for culturable fungi and ergosterol, although they were less precise. For endotoxin, we found substantially increased and significant odds in group-based analyses, while we found no associations in individual-based analyses for various symptoms. Our study suggested that the building floor was useful in constructing exposure groups for microbial agents in this water-damaged building for epidemiologic analysis. Our study showed that group-average exposure estimation provides less attenuated associations between exposures to microbial agents and health in damp indoor environments where measurement error and intrinsic temporal variability are often large.

Determinants, reproducibility, and seasonal variation of ergosterol levels in house dust

“…Fungal exposure can be estimated through several means, including cultivation of viable spores and determination of chemical markers for fungi, typically cell wall components, such β ‐1,3 glucans and ergosterol. Ergosterol is a fungal membrane lipid that has been used as a chemical marker to determine fungal biomass from various environments, including indoors (Cho et al., ; Hyvärinen et al., ; Sordillo et al., ; Zhang et al., ).…”

Changes in respiratory and non-respiratory symptoms in occupants of a large office building over a period of moisture damage remediation attempts

“…Thus, we cannot exclude the possibility that the lack of remediation effects on occupants’ health in our study might have resulted from persistent exposures in the building even after the various remediation activities. However, because we adjusted our statistical models for microbial exposures to endotoxin, ergosterol, and culturable fungi as time-varying covariates that were significant risk factors for various respiratory and non-respiratory symptoms in the same population [ 19 ], the potential confounding effects of these persistent exposures were likely to be minimized. A potential explanation of our findings might be that once respiratory or severe non-respiratory symptoms have developed in occupants of moisture-damaged buildings, physiological recovery in the affected employees might be compromised.…”

The Fort Collins commuter study: Variability in personal exposure to air pollutants by microenvironment

“…Mean con- and microenvironment means between each pair of pollutants (see Table S2; results were similar for Spearman's correlation coefficients). 44 Rappaport and Kupper used a nested design with person nested within city (no person is in both cities) to examine 24-hour VOC exposures in the United States and found that typically half or more of the variance was within-person. The highest correlation observed was between PM 2.5 and BC at Eateries and weakest be- analysis.…”

“…Recent studies have examined the variance components for daily averaged PM 2.5, microbial agents, and volatile organic carbon. [44][45][46][47] In a study in Gothenburg, Sweden, 45 daily PM 2.5 concentrations measured among 29 subjects (<2 samples per participant, total n = 43) and variance was partitioned within and between participants and resulted in an ICC value equal to 0.62. ICC values tended to be less than 0.5 and approached zero for some elements, in PM 2.5 trace analysis.…”

“…45 ICC values (with variance partitioned within and between participants) less than 0.5 were also observed for 24-hour PM 2.5 exposures among adults in Hong Kong 47 and for exposure to microbial agents in buildings. 44 Rappaport and Kupper used a nested design with person nested within city (no person is in both cities) to examine 24-hour VOC exposures in the United States and found that typically half or more of the variance was within-person. 46 Denmark.…”