An innovative, software-based occupant health survey instrument and multivariate statistical analysis based on a retrospective cohort methodology was used to investigate occupant illness in a water-damaged, "sick" office building. A highly statistically significant incidence and attributable risk of respiratory, neurocognitive, and constitutional symptoms was measured among occupants in comparison with those in a control building. Logistic regression analysis demonstrated that the collective symptoms were not explained by such building-related illnesses such as asthma or hypersensitivity pneumonitis, nor by pre-existing medical conditions, smoking, or residential environmental factors. Cases were uniformly distributed among occupants throughout the building. The epidemiological findings were consistent with the known health effects of indoor mold exposure, and were not explained by either an allergic or infectious mechanism of disease.


Sick building syndrome, Epidemiology, Building related symptoms, Indoor air quality, Mold


In the past 10 years, exposure to certain types of mold in water-damaged buildings has been increasingly implicated as the cause of sick building syndrome (SBS). Epidemiological investigation of occupants of a building or workplace is a well-established scientific method used to identify and measure the nature, distribution, and cause of occupational or environmental illness within a given population. Most published, paper-based occupant health questionnaires and analysis methods have suffered from significant methodological limitations in their ability to define and measure occupant symptomatology as a multi-organ syndrome, and control for confounding variables (AIHA 12). In its publication, Bioaerosols: Assessment and Control, the American Conference of Governmental Industrial Hygienists underscored the importance of epidemiological investigation of occupant/IAQ-related health problems as a means to "clarify whether there is a building-related problem and, if so, its nature as well as possible means for resolution," and emphasized the need for improved study design and statistical analysis to conduct an inherently complex investigation (ACGIH 3.7). The study herein employed a new epidemiological instrument and approach to analysis of complex occupant symptoms in a water-damaged "sick building" that had predominantly hidden mold contamination.

Study and Control Buildings

The study building, located in northern Nevada, was a leased, 1-story, ca. 10,000 square foot office facility with central heating and air conditioning that housed a government agency since the late 1970's. Ongoing, unexplained employee health complaints among the 110 full-time government employees and an associated increase in employee absences and medical treatment occurred over a period of years. Traditional IAQ measures were normal, and inspection of the ventilation system was within acceptable operating parameters. The building was ultimately deemed to be a "sick building." An indoor air quality (IAQ) investigation in 2001 revealed a longstanding history of unrepaired roof leaks resulting in stained suspended ceiling tiles and dripping water from the ceiling onto desks and floor space throughout the building. It was learned that in 1998, two interior walls had been discovered to be saturated with water in separate corners of the building. Occupants reported musty odors in these areas.

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