The bioaerosols identified a Midwestern hospital pool had sickened nine lifeguards who had become ill with hypersensitivity pneumonitis, a lung condition that mimics pneumonia symptoms. This forced the pool to shut down.

Lars T. Angenent, Ph.D., Washington University assistant professor of chemical engineering, and the Colorado engineers mounted three high-efficiency particulate air (HEPA) ultraviolet (UV) air filters on the ceiling of the pool room. They compared concentrations of total bacteria, culturable bacteria and airborne endotoxin - a poison present in gram-negative bacterial cell walls that can cause severe inflammatory responses - with and without the air filters operating under similar conditions.

They compared the performance of the filters twice, one year apart, and found that the filters reduced concentrations of culturable bacteria by 69 and 80 percent during monitoring periods executed in respective years. The filters reduced concentrations of total bacteria by 12 and 76 percent, respectively, over the same span. But the filters did not affect airborne endotoxin concentrations.

"This specific filter has a blower that takes a high volume of air and puts it through a filter that screens bacteria and even smaller particles," said Angenent, a member of Washington University's Environmental Engineering Science Program. " And after the filter there is UV light; if something passes through the filter, the UV zaps it. It's a combination approach that appears very effective. The bacterium that had been causing illness was Mycobacterium avium, which can make immunocompromised people ill, and since a lot of elderly use therapy pools, that's a concern. However, since using the filters, no one has gotten sick."

The researchers also tested the hybrid filters in an environmentally controlled laboratory chamber to come up with the air-exchange rate for the therapy pool assays, among other parameters.

MEDICA.de; Source: Washington University in St. Louis