An indoor air cleaning system originally developed to zap dust mites and mold spores also destroys airborne anthrax and other pathogenic microbes, says the University of Florida engineering professor who pioneered the technology.

The system has been successfully tested against a close cousin of the anthrax bacteria and could be installed relatively inexpensively and quickly in office and home heating and air conditioning systems, says Yogi Goswami, a UF professor of mechanical engineering and director of UF's Solar Energy and Energy Conversion Laboratory. "There are other technologies for air cleaning, but for air disinfection, there is no more effective system," Goswami said.

The photocatalytic air cleaning system relies on the interaction between light and titanium dioxide, a simple and widely available chemical. When light is absorbed into the titanium dioxide, it acts as a catalyst to produce an oxidizing agent. The agent, called a hydroxyl radical, "is like a bullet for the bacteria," Goswami said, destroying dust mites, mold spores and pathogens by disrupting or disintegrating their DNA.

Goswami came up with the system in the mid-1990s as a cure for so-called "sick building syndrome," when poor ventilation and a build-up of mold or mildew cause illnesses for people who work inside. Initial research proved that the system kills the mold spore, aspergillus niger, considered to be one of nature's hardiest spores, he said.

More recent research has shown that the system also destroys bacillus subtilis, a spore that causes food spoilage and is a cousin of the anthrax spore, bacillus anthracis. "In the laboratory, we normally test with nonpathogenic bacteria that are closely related to pathogenic bacteria, so there's no risk to people," Goswami said. "As we expected, our tests showed the system was effective against bacillus subtilis."

The technology is an improvement over traditional filter-based systems in part because there is no opportunity for bacteria to collect and multiply on the filters that clear it from the air, he said. "Filters can actually increase the danger because they concentrate the bacteria," he said. The system is also an improvement over systems that use ultraviolet light, which do not consistently kill all the bacteria, he said.

Goswami said the technology could be installed in central ventilation systems to decontaminate buildings or homes or used in specific locations where contamination is feared. Given the incidents of anthrax contamination within the U.S. Postal Service, one application would be to install it in mail sorting or collection areas, he said.

"This is affordable for people. A central system for a single-family house would probably be in the range of $1,000 to $1,500," he said. As part of UF's technology transfer mission, the technology was patented and licensed to Universal Air Technologies (Gainesville, FL). The company, which got its start at UF's biotech incubator, the Biotechnology Development Institute (Alachua, FL), sells a variety of portable and central air purification systems based on the technology.