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Analysis of health effects associated with indoor environmental quality in a sample of U.S. office buildings.

Mendell-MJ; Apte-MG; Cozen-M; Gomez-Lei-Q; Mirer-A; Buchanan-A
Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R01-OH-008117, 2008 Nov; :1-29
Episodes of nonspecific health complaints from workers in office and commercial buildings have been reported for over 30 years. Yet the factors responsible for these symptom complaints, sometimes called sick building syndrome (SBS) or building-related symptoms (BRS), have not been clearly identified. It is now clear that the publicized buildings with such complaints are only the visible part of a larger phenomenon - studies of representative U.S. office buildings show that over 40% of indoor workers experience one or more frequent work-related symptoms in their buildings (Brightman, Wallace et al. 1999). These potential adverse effects of indoor work environments are of public health importance because the population potentially exposed is large. Approximately 89 million workers in the U.S., almost 70% of the workforce, work in indoor environments (Mendell, Fisk et al. 2002). Researchers have estimated that among the 35-60 million workers experiencing one or more weekly building-related symptoms, improved indoor environmental conditions could prevent this in 8-30 million workers each year (Mendell, Fisk et al. 2002). To learn more about risk factors for BRS, we analyzed data from the largest available study of U.S. office workers, the Building Assessment and Survey Evaluation (BASE) Study from the U.S. Environmental Protection Agency, which involved a representative sample of 100 buildings and 4,326 workers. Analyses used separate multivariate logistic regression models for seven types of BRS. Specific aims included: to describe associations between BRS and outdoor air ventilation rates (VRs), assess if symptoms are associated with indoor chemical reactions of outdoor ozone and ventilation filters, estimate relationships between BRS and indoor thermal factors, combine risk factors identified in current and prior analyses into comprehensive statistical models, assess whether personal or psychosocial factors confound/distort apparent associations of BRS with environmental risk factors, and determine if data on occurrence of BRS in the BASE study buildings can be helpful in interpreting frequency of symptom reporting in other office buildings. Focused BASE analyses of environmental factors and BRS identified risk factors associated with increases in multiple symptoms, such as: lower VRs (even some VRs above the current target rates); higher occupant density; polyester ventilation filters (especially in buildings with moderate to high levels of outdoor ozone); warmer winter indoor temperatures (even within the winter thermal comfort range); and colder summer indoor temperatures (below the summer comfort range). When these risk factors were combined in larger comprehensive models with prior identified risk factors from the BASE data, the risk factors associated with multiple BRS in these models included poorly maintained humidification systems, less frequently cleaned cooling coils and drain pans, outdoor air intakes closer than 60 m to the ground; polyester ventilation filters (especially in buildings with moderate or higher outdoor ozone); warmer winter indoor temperatures (even within the winter thermal comfort range); non-carpeted floors or old carpets (relative to newer carpets); more efficient ventilation filters; and masonry external walls. Other analyses documented 1) that psychosocial stressors among indoor workers, although strongly associated with BRS among indoor symptoms, were independent of associations between symptoms and environmental risk factors and did not explain them, and 2) that personal factors differed sufficiently among buildings, and influenced BRS strongly enough, that it was impractical to use the BASE symptom data as a reference for interpreting symptoms in other office buildings, because adequate statistical adjustments were not possible due to small numbers of workers available in each BASE building. One clear descriptive finding is that most U.S. office buildings were too cold in the summer, so that less air-conditioning would bring them within the thermal comfort envelope, and might also reduce symptoms, increase thermal comfort, and decrease energy use. The analytic findings from regression models identified a set of risk factors, many not previously found, associated with increases in multiple BRS in office workers. These findings strongly suggest further research to confirm and clarify adverse effects of newly identified risk factors for BRS in office workers, and may suggest proactive changes in some design, operation, or maintenance practices in office buildings.
Air-quality; Air-quality-measurement; Environmental-factors; Environmental-health; Environmental-health-monitoring; Epidemiology; Indoor-air-pollution; Indoor-environmental-quality; Mathematical-models; Psychological-factors; Qualitative-analysis; Seasonal-factors; Statistical-analysis; Surveillance-programs; Ventilation-systems; Work-analysis; Work-environment; Worker-health; Worker-health; Worker-health; Workplace-studies
Mark J. Mendell, PhD, Indoor Environment Department, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS90-3058, Berkeley, CA 94720
Publication Date
Document Type
Final Grant Report
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Fiscal Year
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NIOSH Division
Priority Area
Work Environment and Workforce: Indoor Environment
Source Name
National Institute for Occupational Safety and Health
Performing Organization
University of California, Lawrence Berkeley Lab