Microbial contamination in ventilation systems of modern office buildings has been documented to result in illness among workers. This study was conducted to test whether germicidal ultraviolet (GUV) irradiation of drip pans and cooling coils within ventilation systems of office buildings would reduce occupants work-related symptoms. A double-blind multiple crossover design was used. Within three consecutive trials, GUV was off for 12 consecutive weeks, then on for the next four weeks. In the last week with GUV off, or on, workers completed self-administered questionnaires regarding presence of symptoms and environmental satisfaction. Simultaneously, thermal, chemical and microbial parameters including endotoxin were measured outdoors, within ventilation systems and in occupied spaces. Operation of GUV lights resulted in significant reduction of microbial and endotoxin concentrations on irradiated surfaces within the ventilation systems, although airborne concentrations of these substances were unchanged. The 771 participants, who appeared to remain blinded, reported significantly fewer work-related overall (within-subject adjusted odds ratio 0.8: [95% confidence interval (0.7,0.99)], respiratory [0.6, (0.4, 0.9)] and mucosal [0.7; (0.6, 0.9)] symptoms, when the GUV were operating. Reduction of mucosal symptoms was greatest among atopic workers [0.6, (0.5, 0.8)], and neversmokers [0.7, (0.5, 0.9)]. Never-smokers also had greater reduction of respiratory [0.4, (0.2,0.9)], and musculo-skeletal symptoms [0.5 (0.3, 0.9)], with GUV on. GUV was safe, effective in reducing ventilation system surface microbial contamination as well as endotoxin, and associated with significant reduction in respirator, mucosal and overall symptoms. This effect was greater among workers at risk for allergic or hypersensitivity response to microbial antigens.
Respiratory Epidemiology Unit, McGill University, 1110 Pine Avenue West, Room 103, Montreal, QC, H3A 1A3