Indoor air quality and human health and comfort in large, mechanically ventilated office buildings: Longitudinal studies

The objectives of this research were to investigate methods to assess indoor environmental quality and the health symptoms and perceptions of building occupants, and to utilize such measurements in epidemiological investigations aimed at understanding causes of sick building syndrome (SBS) and other sources of occupant complaints.; Two experimental interventions and a longitudinal cohort investigation were used to study 49 workers on four floors of a large “non-problem” office building. Eight surveys addressing occupant health, comfort and perceptions of the indoor environment, including a comprehensive initial survey, were administered to study participants over a 17-month period. Simultaneously, indoor air quality parameters were measured using continuous and integrated sampling techniques. Interventions included cleaning the building's heating, ventilating and air conditioning (HVAC) systems, and distributing a document to participants describing the indoor environment. The longitudinal cohort study tested the association between symptomology and perceptions to HVAC operational modes.; Continuous measurements of air quality provided useful trend and peak information, superior to that obtained in “grab” and integrated sampling. Several pollutants showed diurnal and/or weekly patterns that were correlated to indoor and outdoor emissions. Levels of bioaerosols, particulate matter, volatile organic compounds, ozone, carbon dioxide and nitrogen oxides fell below standards and guidelines. Many participants experienced SBS symptoms (e.g., 32% for eye symptoms, 12% headache) at rates similar to those found in other large building surveys. Operating the HVAC system in economizer mode (spring and fall), as compared to high recirculation (winter and summer), reduced some adverse health and comfort outcomes. However, changes were small and seasonal factors, among others, could not be completely controlled. No significant differences in symptoms and perceptions due to the information document or the cleaning intervention were observed, the latter possibly because contaminant levels were already low and not significantly altered.; This study demonstrates methodological improvements for investigating the indoor environment and occupant health, including the use of continuous instrumentation to assess pollutant exposures, psychosocial stress measures (found to be a significant co-factor), repeated measures on occupants, and standardization of questionnaires. These and other recommendations should improve the understanding of the effect of the indoor environment on health and comfort.