|28 November 03|
|NewScientist.com news service|
Zapping bugs which flourish in office ventilation systems with ultraviolet radiation could cut the sickness suffered by millions of office workers, suggests a new study.
"Sick building syndrome," recognized as a medical condition in the 1980s, results in symptoms such as a stuffy nose, itchy eyes and throat, and respiratory problems like asthma. The symptoms are especially common in people who work in air-conditioned offices, where heavy growth of bacteria and fungi is common within the ventilation systems.
Dick Menzies, McGill University in Montreal, Canada, and colleagues found that by installing UV germicidal irradiation (UVGI) lamps in the air-conditioning systems of three office blocks, they could cut all such symptoms by 20 percent.
"Installation of UVGI in most North American offices could resolve work-related symptoms in about 4 million employees," he says.
"A lot of people think sick building syndrome is all in people's heads," Menzies told the Toronto Star newspaper. "The fact that you can install UV lights and a susceptible subgroup get biologically plausible improvements tells me that at least some of the problem is clearly not in their head."
The team had UVGI lamps installed in the cooling coils and drip pans of the ventilation systems of three office blocks in Montreal. Resistant bugs sitting on the surfaces were predicted to have a survival time of less than four minutes.
The lamps were switched off for the first 12 weeks of the study, while 771 office workers were quizzed on the specific symptoms they suffered. The lamps were then switched on for four weeks, and off again for 12. In total, three on/off cycles were tested over 48 weeks.
In workers reporting symptoms, switching on the UVGI lamps resulted in a 20 percent overall reduction. It also slashed respiratory symptoms by 40 percent, and mucosal symptoms by 30 percent.
These effects were greatest in people with known allergies and in workers who had never smoked. Muscular complaints were halved in people who never smoked.
Microbes and endotoxins
The team says the UVGI lamps resulted in a 99 percent cut in the concentrations of microbes and of endotoxins - poisons in the cell walls of certain bacteria. Endotoxins have been associated with flu-like symptoms.
As 70 percent of employees in North America and Western Europe now work in offices, the researchers suggest that installing UVGI may be a cost-effective way of reducing employee absence due to sick building syndrome.
Other methods of cleaning office ventilators are being developed, including ones that use filters or ionisation to stop the microbes reaching workers.
However, Roy Anderson, an infectious diseases expert at Imperial College in London, UK, cautions that disinfecting ventilation systems alone is unlikely to stop outbreaks of all contagious respiratory diseases.
"You've got multiple methods of transmission and for control, you need to address all of them," he told Associated Press.