Clean Air Act

Airborne pathogens, such as the bacterium that causes Legionnaire's Disease and the virus responsible for avian flu, as well as putative biological agents that may be released deliberately, have led to an increased awareness of the need for sophisticated air purification. According to Valérie Keller and colleagues from Louis Pasteur University, one solution might lie in the use of heterogeneous photocatalysts. These materials have already been exploited in water purification processes because of their strong oxidizing power under ultraviolet irradiation.


Marie-Claire Lett

Now, Keller and her colleagues, Nicolas Keller, Marc Ledoux, and Marie-Claire Lett, have investigated the ability of titania (TiO₂) to destroy microorganisms, such as Escherichia coli, in an airstream. E. coli is similar in size to the Legionnella pneumophila bacterium and so acted as a model microbe for their proof of principle experiments. The team combined a purpose-built photocatalytic aero-decontamination device with a commercially available titania photocatalyst. They have now demonstrated that the system can remove the bacteria from the air stream with 99.1-99.8 % efficiency. The researchers are now working towards treating larger volumes of flowing air in order to meet industrial requirements.


	Nicolas Keller

In an accompanying highlight to the research paper, the publisher claims that, "This achievement has major repercussions for public health as it shows it is feasible to decontaminate the air in high risk infection areas such as hospitals and commercial aircrafts." While the purification results are commendable, two concerns remain regarding the efficiency and efficacy of the system at its current state of development. First, a highly contagious bacterium even at 0.9% contamination could be sufficient to have an impact on health. Secondly, the current research does not address the more pressing issue of decontaminating airstreams of viruses, such as putative mutants of avian flu that might nevertheless enter a sealed emergency room environment.


Credit: RSC/Keller

The researchers allude to the photocatalyst being active in destroying SARS but present no results in this paper. Nevertheless, the system does demonstrate for the first time the decontamination of a bacteria-containing air stream by photocatalysis at room temperature. The researchers say that this, "opens new routes for inactivating biological species in flowing air by a soft, practical, non-restrictive, and easy to use technique."

"We will test the system on pathogenic bacteria in forthcoming work," Nicolas Keller told Reactive Reports. "Viruses are only a future development of the story, as they are smaller than bacteria," and he adds, "We think titania could be active in destroying SARS, but no results are reported here."