Chlorine dioxide is a broad spectrum biocide with proven activity against bacteria, viruses, yeasts, mycobacteria and bacterial spores when tested against European test norms. It is widely used in medical and pharmaceutical environments. It is also used in various applications such as drinking water treatment and the washing and treatment of food stuffs. Chlorine dioxide is favoured over non-oxidising disinfectants due to its greater efficacy. Alcohols and quaternary ammonium compounds provide reasonable efficacy against bacteria and fungi. However, they are less (or not) effective against viruses and mycobacteria and have no credible efficacy against bacterial spores inacceptable contact times. In contrast, chlorine dioxide has a proven public record of being a high-level sporicidal disinfectant in contact times as short as 30 seconds.
As chlorine dioxide is an oxidising agent, the primary mode of kill is via electron exchange within the microorganism’s molecular structure. This mode of action means it is not possible for the organism to develop resistance. Although all oxidising agents are capable, at suitable concentrations, of providing sporicidal disinfection, they have several drawbacks when compared to chlorine dioxide. Hydrogen peroxide and peracetic acid are known to be corrosive and can be a hazard to operators. Ozone generators are expensive and chlorine based disinfectants have short shelf lives. Chlorine is also known to form potentially hazardous by-products.
Chlorine dioxide is known to be compatible with the majority of materials commonly found in medical and pharmaceutical equipment and environments, and has an excellent health and safety record when used at recommended levels. Chlorine dioxide is not transported as an active and is generated at point-of-use from sodium chlorite and a suitable acid. This gives the product a very long shelf life when compared to other oxidisers. The point-of-use generation ensures that the activated solution provides peak efficacy without the requirement for test kits to ensure that the product is fit for purpose.
Although a halogenated disinfectant, chlorine dioxide does not readily form halogenated by-products (trihalomethanes) due to the nature of the molecular bonding. The most widely accepted structure for chlorine dioxide is a double bonded oxygen atom and a single bonded oxygen atom to the chlorine atom. The structure resonates, with the effect that the double and single bonds alternate between the two oxygen atoms. Chlorine dioxide is supported through the Biocidal Product Regulation for use in product types 2, 3, 4, 5, 11 and 12 and is also approved by the United States Environmental Protection Agency.