Respiratory Safety Evaluation in Mice and Inhibition of Adenoviral Amplification in Human Bronchial Endothelial Cells Using a Novel Type of Chlorine Dioxide Gas Reactor

Since the onset of the COVID-19 pandemic, there has been a growing demand for effective and safe disinfectants. A novel use of chlorine dioxide (ClO2) gas, which can satisfy such demand, has been reported. However, its efficacy and safety remain unclear. For the safe use of this gas, the stable release of specific concentrations is a must. A new type of ClO2 generator called Dr.CLOTM has recently been introduced. This study aimed to investigate: (1) the effects of Dr.CLOTM on inhibiting adenoviral amplification on human bronchial epithelial (HBE) cells; and (2) the acute inhalation safety of using Dr.CLOTM in animal models. After infecting HBE cells with a recombinant adenovirus, the inhibitory power of Dr.CLOTM on the virus was expressed as IFU/mL in comparison with the control group. The safety of ClO2 gas was indirectly predicted using mice by measuring single-dose inhalation toxicity in specially designed chambers. Dr.CLOTM was found to evaporate in a very constant concentration range at 0–0.011 ppm/m3 for 42 days. In addition, 36–100% of adenoviral amplification was suppressed by Dr.CLOTM, depending on the conditions. The LC50 of ClO2 gas to mice was approximately 68 ppm for males and 141 ppm for females. Histopathological evaluation showed that the lungs of female mice were more resistant to the toxicity from higher ClO2 gas concentrations than those of male mice. Taken together, these results indicate that Dr.CLOTM can be used to provide a safe indoor environment due to its technology that maintains the stable concentration and release of ClO2 gas, which could suppress viral amplification and may prevent viral infections.

Examination of preventive effect and safety of chlorine dioxide on nosocomial pneumonia

Nosocomial infections originate in hospitals. An example of this nosocomial pneumonia, which develops in patients around 48 hours after admission. It has a high mortality rate and occurs in a large number of patients. Professor Kaoru Obinata, Department of Pediatrics, Juntendo University Urayasu Hospital, Japan, is exploring a novel technique to combat nosocomial pneumonia and other nosocomial infections. This involves the safe and effective application of chlorine dioxide in medical settings and is particularly novel given that, in high doses, chlorine dioxide is toxic and can cause severe irritation and burns. Obinata and the team are looking at the use of chlorine dioxide gas in conventional induction countermeasures. The researchers believed that, used in combination with a high-efficiency particulate air (HEPA) filter, this method will be highly safe and boast high prevention effect and cost effectiveness. The team has found that chlorine dioxide aqueous solution is effective against various bacteria, viruses and fungi at a lower concentration than sodium hypochlorite solution and that that low-concentration of chlorine dioxide gas is effective against airborne bacteria and viruses, as well as adherent bacteria and viruses. Using mouse models, they have shown it to be effective against aerosol infection for the influenza virus and against influenza-like illness in humans. Next, the researchers will find a means of ensuring that the concentration of chlorine dioxide can be kept to safe and constant levels to ensure the effects are beneficial and not harmful.

Development of sustained release formulations of chlorine dioxide gas for inactivation of foodborne pathogens on produce

Formulations for the sustained release of chlorine dioxide (ClO2) gas were developed, and their gas-producing profiles and antimicrobial effects against Escherichia coli O157:H7 and Salmonella Typhimurium were evaluated in spinach leaves and tomatoes under different relative humidity (RH) conditions. Sodium chlorite (NaClO2) and citric acid were used to generate ClO2 gas, and the generation rate and maximum ClO2 gas concentration were controlled using diatomaceous earth (DE) and calcium chloride (CaCl2). Under 90% RH conditions, sustained release of ClO2 gas was achieved in presence of DE. When 12 g of DE was added to the mixture, the ClO2 gas concentration remained constant at 18 ± 1 ppmv for approximately 28 h. At 50% RH, addition of CaCl2 was effective in maintaining a constant ClO2 gas concentration. When 0.05 g of CaCl2 was added to mixtures containing 0.5 g of DE, ClO2 gas concentration remained constant at 11 ± 1 ppmv for approximately 26 h. Treatment with 30 ppmv of ClO2 gas at 90% RH achieved more than 6.16 and 5.48 log reductions of E. coli O157:H7 and S. Typhimurium on spinach leaves (in 15 min), and more than 6.78 and 6.34 log reductions of the same in tomatoes (in 10 min). The sustained release formulations for ClO2 gas, developed in this study, could facilitate the use of ClO2 gas as an antimicrobial agent in the food industry.