NEW YORK (Reuters) -- Installing ultraviolet germicidal lights in office buildings' ventilation systems kills microorganisms and relieves workers' sniffles, headaches, and other unexplained health problems, according to a report published in today's issue of The Lancet.

Many people who work in office buildings have what are called "non-specific building-related illnesses or symptoms," lead author Dr. Dick Menzies, from McGill University in Montreal, and colleagues note. These include irritation of eyes, nose or throat, fatigue, difficulty concentrating, and pain in the muscles, joints or back.

Although UV light has proven safe, effective, and inexpensive in controlling contamination in a variety of settings, it has not been tested in office buildings.

In a crossover trial involving 771 participants, the researchers tested germicidal lights installed in the ventilation systems of three office buildings in Montreal. The lights were aimed at cooling coils and drip pans. During a 48-week period, the lights alternated between being off for 12 weeks and on 4 weeks.

Use of the UV lights was associated with a 99-percent reduction in bacteria, yeast and other fungus, as well as endotoxin levels on ventilation surfaces, the researchers note. Airborne levels were also reduced.

Compared with off-light periods, on-light periods were linked to significantly fewer overall work-related symptoms, respiratory symptoms, and mucosal symptoms. Among workers who had never smoked, improvements in musculoskeletal symptoms were also noted during on-light periods.

Women, non-smokers, and subjects with atopic disease (allergy-induced sneezing, coughing, and scratching) experienced a greater reduction in mucosal symptoms than other subjects.

No adverse effects were reported by any of the subjects, the investigators point out. "To install UV germicidal irradiation in the ventilation systems of an 11,148 meters-squared office building with 1000 occupants would cost $52,000, and $14,000 per year for energy, maintenance, and bulb replacement," the authors note. "For every worker, the estimated $52 for initial and $14 for yearly operating costs, compare favorably with the estimated yearly losses from absence caused by building-related sickness."