Chlorine dioxide (ClO2) is a broad-spectrum biocide with proven efficacy against a range of microbial organisms such as bacteria, viruses, protozoa, yeasts, mycobacteria and bacterial spores. Originally used in water treatment and food industries, chlorine dioxide has now been adopted as the go-to high-level disinfectant in medical, pharmaceutical, veterinary and laboratory settings.
The mechanism through which ClO2 achieves its potent biocidal effect is oxidation1. Oxidation involves the oxidising agent sequestering electrons from the microorganism, which causes a molecular imbalance that inevitably leads to the microorganism’s death. The main advantage of using oxidising biocides over non-oxidising biocides (alcohols, quaternary ammonium compounds) is the inability for microorganisms to develop resistance2, as well as the broad range of efficacy1.
The comparison of ClO2 with other oxidisers, such as hydrogen peroxide is of interest. Whilst hydrogen peroxide and other oxidisers work through the same mechanisms as chlorine dioxide, they have been shown to be less effective against microbes3. This is attributed to ClO2’s unique ability to penetrate the microorganism’s 3D protein structure3 and, thus, better oxidise the molecules. Additionally, ClO2 forms no hazardous by-products4 and is less harmful to people and equipment than other common biocides such as hydrogen peroxide and chlorine2.
Chlorine dioxide generated from sodium chlorite is supported for the active substance registration under the GB and the EU Biocidal Product Regulations for Product Types 2, 3, 4, 5, and is an active substance in various pesticides registered with the United States Environmental Protection Agency (EPA).
1. Block, S., Knapp, J. and Battisti, D. (2001). Disinfection, sterilization, and preservation. Philadelphia: Lippincott Williams & Wilkins, pp.215-227.
2. Noszticzius, Z., Wittmann, M., Kály-Kullai, K., Beregvári, Z., Kiss, I., Rosivall, L. and Szegedi, J. (2013). Chlorine Dioxide Is a Size-Selective Antimicrobial Agent. PLoS ONE, 8(11), p.e79157.
3. Finnegan, M., Linley, E., Denyer, S.P., McDonnell, G., Simons, C., Maillard, J.Y. (2010) Mode of action of hydrogen peroxide and other oxidizing agents: differences between liquid and gas forms, Journal of Antimicrobial Chemotherapy, 65(10), pp. 2108–2115.
4. Al-Otoum, F., Al-Ghouti, M., Ahmed, T., Abu-Dieyeh, M. and Ali, M. (2016). Disinfection by-products of chlorine dioxide (chlorite, chlorate, and trihalomethanes): Occurrence in drinking water in Qatar. Chemosphere, 164, pp.649-656.