PREVALENCE OF THE SICK BUILDING SYNDROME SYMPTOMS IN OFFICE WORKERS BEFORE AND 6 MONTHS AND 3 YEARS AFTER BEING EXPOSED TO A BUILDING WITH AN IMPROVED VENTILATION SYSTEM

Objective--The prevalence of symptoms associated with the sick buildin g syndrome (SBS) has recently been shown to decrease by 40% to 50% amo ng office workers six months after they were exposed to a building wit h an improved ventilation system. The objective of the present study w as to find whether the decrease in the prevalence of symptoms was main tained three years later. Methods--Workers from the same organisation occupied five buildings in 1991 and moved during that year to a single building with an improved ventilation system. All buildings had seale d windows with mechanical ventilation, air conditioning, and humidific ation. Workers completed a self administered questionnaire during norm al working hours in February 1991 before moving, in February 1992 six months after moving, and in February 1995, three years after moving. T he questionnaire encompassed symptoms of the eyes, nose and throat, re spiratory system, skin, fatigue, and headache, as well as difficulty c oncentrating, personal, psychosocial, and workstation factors. During normal office hours of the same weeks, environmental variables were me asured. Results--The study population comprised 1390 workers in 1991, 1371 in 1993, and 1359 in 1995, which represents 80% of the population eligible each year. The prevalence of most symptoms decreased by 40% to 50% in 1992 compared with 1991. This was similar in 1995. These fin dings were significant and remained generally similar after controllin g for personal, psychosocial, and work related factors. Conclusion--In this study, the decrease of 40% to 50% in the prevalence of most symp toms investigated six months after workers were exposed to a new build ing with an improved ventilation system was maintained three years lat er. The results of the present follow up study provide further support for a real effect of exposure to a new building with an improved vent ilation system on the prevalence of symptoms associated with the SBS.