The California Healthy Building Study, Phase 1: A Summary

Increasing our understanding of the building and environmental factors that result in healthy and productive office workers is the long-term goal of the California Healthy Building Study. The primary objectives of the Phase-1 study were to: (1) test hypotheses about associations between health symptoms and features of the buildings, indoor environments, and jobs; (2) obtain background data on health symptom prevalences and indoor air quality; and (3) gain experience with this type of study. Primary hypotheses were that symptom prevalences, after adjustment for confounders, would be: (a) higher in sealed air conditioned buildings than in naturally ventilated buildings; (b) not related to the total concentrations of volatile organic compounds (VOC), fungi, or bacteria; and (c) higher as the measured thermal comfort decreased. For the study, we selected three naturally ventilated (NV) office buildings; three mechanically ventilated (MV) office buildings; and six air conditioned (AC) office buildings. Information on the prevalences of work-related symptoms, demographics, and work and job factors were determined via a questionnaire completed by 880 occupants. Several indoor environmental parameters were measured. Logistic regression models were used to assess associations between symptom prevalences and features of the buildings, indoor environments, jobs, and occupants. Although symptom prevalences varied within each group of buildings, the occupants of the MV and AC buildings had significantly more symptoms than occupants of the NV buildings. Based on preliminary analyses of the data, none of the measured environmental parameters were clearly associated with symptom prevalence; however, increased prevalences of some symptoms were associated with several job and workspace factors including: presence of carpet , increased use of carbonless copies and photocopiers, space sharing, and distance from a window.