Around 70% of employed people in industrialised countries work in air-conditioned offices. These workers frequently have unexplained work-related symptoms such as irritation of the mucous membranes of the eyes, throat, and nose, as well as respiratory symptoms. Dick Menzies from the Montreal Chest Institute, McGill University, Canada, and colleagues assessed whether ultraviolet germicidal irradiation (UVGI) of drip pans and cooling coils within office ventilation systems would reduce microbial contamination, and thus occupants' work-related illness.
Employees from three offices in Montreal participated in the study. UVGI was off for 12 weeks, then on for four weeks for three cycles totalling 48 weeks. Reliable data were available from 771 people. UVGI had a substantial effect in reducing reported work-related illnesses. In workers with symptoms in some, but not all weeks, UVGI resulted in a 20% overall reduction in all symptoms; a 40% reduction in respiratory symptoms; and a 30% reduction in mucosal symptoms. These benefits were greatest for workers with known allergies and for people who had never smoked. Muscular complaints were halved among never-smokers when UVGI was in use.
Dick Menzies comments: "Installation of UGVI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of heating, ventilation, and air-conditioning systems. The cost of UVGI installation could in the long run prove cost-effective compared with the yearly losses from absence because of building-related illness."
He adds: "To install UVGI in the ventilation systems of an 11 148 square-meter office building with 1000 occupants would cost US$52 000, and $14 000 per year for energy, maintenance, and bulb replacement (estimates from manufacturer). For every worker, the estimated $52 for initial and $14 for yearly operating costs compare favourably with the estimated yearly losses from absence caused by building-related sickness."