TANAKA Hiroshi : P. E. Jp, Chemical Engineering Department, Products Development Center, Corporate Research & Development SAKURAI Miei : Doctor of Engineering, Senior Researcher, Chemical Engineering Department, Products Development Center, Corporate Research & Development
ISHII Kousuke : Doctor of Engineering, Senior Researcher, Chemical Engineering Department, Products Development Center, Corporate Research & Development
MATSUZAWA Yoshiaki : Doctor of Engineering, Manager, Chemical Engineering Department, Products Development Center, Corporate Research & Development
More than 99.99% of inf luenza A virus particles attached to a plastic carrier were inactivated by exposure to 10 ppm ( V/V ) – ozone gas for 210 min at 23 to 29°Cand a relative humidity of 64 to 65%. When the virus was exposed to 20 ppm ( V/V ) – ozone gas for 150 min, more than 99.999% was inactivated. In contrast, the virus remained active after 10 hours under similar conditions without ozone gas. These data suggest that office disinfection against inf luenza viruses might be accomplished by ozone gas fumigation during night-time hours.
Cases of humans becoming infected with a particularly virulent type of the avian inf luenza (bird f lu) virus have been confirmed in recent years, and a global outbreak of human infection with a new inf luenza virus of swine origin has occurred in 2009. Now concerns are growing over the possibility of an inf luenza pandemic being caused by a highly virulent virus. In order to prevent infection, various methods for inactivating such a virus (to eliminate its infectivity) have been studied. One of the most promising of these is virus inactivation using ozone gas.
The effectiveness of ozone gas has been demonstrated in much of the literature on this matter. Shinriki et al. conducted disinfection experiments using 1 400 ppm of ozone gas and reported that ozone inactivated Bacillusspores.(1) Nakamura et al. performed inactivation examinations with MRSA (Methicillin-Resistant Staphylococcus aureus), Escherichiacoli, Pseudomonasaeruginosa, Tubercle bacillus, and Aspergillusnigerby changing the concentration of ozone gas from 5 to 400 ppm.(2) In addition, Murray et al. inactivated influenza viruses, herpes virus, vaccinia virus, adenovirus, and vesicular stomatitis virus under various ozone concentrations ranging from 800 to 1 500 ppm and demonstrated with this mechanism that ozone is effective in inactivating a broad spectrum of viruses.(3)
In most of these studies, including the above-mentioned examples, ozone gas has been used at a concentration of several hundred ppm or above. However, attention needs to be paid to the kind of materials that are to be used in the examination when applying a high concentration of ozone gas to viruses because long-term exposure to ozone gas can degrade some materials.
To prevent influenza infection, measures suited to each possible route of transmission are required. One such route is droplet transmission; that is, transmission via droplets produced by sneezing or coughing. To prevent these droplets from being dispersed in the air, it is recommended that a surgical mask or other suitable face covering be worn.(4) With contact transmission that occurs via viruses which adhere to the surface of the skin of your hands and fingers or to various objects, however, very little of the virus is dispersed in the air. Consequently, it is difficult to filter them from the air or remove them from a room using an air purifier. In addition, it has been confirmed that inf luenza viruses that adhere to the surface of a material can retain their infectivity even 24 hours after adhesion.(5) Effective preventive measures are therefore required, especially to deal with contact transmission.
In this study, we conducted ozone fumigation experiments using an inf luenza virus adhered or fixed to carriers so as to verify the effectiveness of ozone gas, envisaging that fumigation could be conducted using ozone gas at a lower concentration of about tens of ppm in living spaces such as office buildings at night, for example, when no one is present.