Case Study of an Epidemiological and Microbiological Investigation

James Craner, M.D., M.P.H., Linda d. Stetzenbach, Ph.D. Consultant in Occupational & Environmental Medicine, Verdi, Nevada Director, Department of Microbiology, Harry Reid Center for Environmental Studies, University of Nevada-Las Vegas, Las Vegas, Nevada

This report describes the methods and outcome of a physician-led investigation of occupants' prolonged, unexplained illnesses associated with working inside a large, modern office building. Occupants (cases) complained of building-related symptoms including eye, nose, and throat mucous membrane irritation; rashes; respiratory symptoms; profound, unexplained fatigue; and neuro-cognitive symptoms, including difficulty concentrating and short-term memory impairment. No functional ventilation problems or chemical contamination were detected in a walk-through evaluation and basic air quality testing. An epidemiological survey of the building's 700 occupants was then conducted. With 86% of the occupants responding to the survey, there was an average case prevalence of health-related complaints of nearly 25%, evenly distributed among floors. Cases were geographically distributed in a pattern which coincided with the location of the ceiling-mounted variable air volume (VAV) boxes which distributed ventilated air to the occupied spaces. Re-inspection revealed previously undetected, focal water-staining of 40% of ceiling tiles located underneath the VAV boxes throughout the building. Active growth of Stachybotrys chartarum (atra) and other fungi was detected on many of the damaged tiles. All water-damaged tiles were replaced and VAV hot water valves were tightened. Occupants reported significant improvement of symptoms within weeks after these changes