DECONTAMINATION
of infectious aerosols (July, 2020) published in the Lancet, found that humans produce infectious aerosols in a wide range of particle sizes, but pathogens predominate in small particles (<5 µm) that are immediately respirable by exposed individuals.3
Also,
evidence is accumulating that SARS-CoV-2 is transmitted by both small and large particle aerosols. It would appear, therefore, that masks should be capable of intercepting even ultrafine particles and given the persistence of viable virus in aerosols, facemasks represent an important means with which to limit transmission of the virus.
The effects of temperature and light In October 2020 the Virology Journal published work by Riddell and others in Australia, in which the effect of temperature on the persistence of SARS-CoV-2 was evaluated on surfaces including glass, stainless steel and both paper and polymer banknotes.4
These surfaces were chosen
because they represent most of the major ‘touch points’ such as mobile phones, money, bank ATMs, supermarket self-serve checkouts etc.
All experiments were conducted in the dark, to negate any effects from UV light; SARS-CoV-2 has been shown to be inactivated by simulated sunlight (Ratnesar- Shumate S, et al [2020], and Schuit M, et al [2020]).5-6
Inoculated surfaces were
incubated at 20˚C, 30˚C and 40˚C and sampled at various time points. The initial viral loads were approximately equivalent to the highest titres excreted by infectious patients, and viable virus was isolated for up to 28 days at 20˚C from the surfaces. Conversely, infectious virus survived less than 24 hours at 40˚C on some surfaces. Nevertheless, this work indicates that SARS-CoV-2 survival rates are considerably longer than previously believed, so disinfection strategies should be adjusted accordingly.
Utilising hypochlorous acid The pandemic has prompted an enormous demand for disinfectant; for use as a hand sanitiser and for the disinfection of surfaces. But there is also increased interest in fogging disinfection. This dramatic growth in demand has led to the release of a large number of products, some of which have not been tested or approved for their claimed purpose. Careful attention should therefore be given to the labels of disinfectants. This is a particular concern when exaggerated claims are made, and where the product contains substances that are hazardous to health. For this reason, products containing hypochlorous acid (HOCl) are proving popular because it is one of the US EPA’s list of active ingredients for use against SARS-CoV-2, and because it does not necessitate the use of PPE. The active ingredient in Nemesis
FEBRUARY 2021
eH2O is stabilised hypochlorous acid, and is compliant with the Biocidal Products Regulations (BPR) – Product Types 1, 2, 3, 4 and 5: Product-type 1: Human hygiene biocidal products Product-type 2: Private area and public health area disinfectants and other biocidal products Product-type 3: Veterinary hygiene biocidal products Product-type 4: Food and feed area disinfectants Product-type 5: Drinking water disinfectants
Compliance with the BPR should be clearly stated on the product label, in addition (with respect to virucidal activity) to confirmation of compliance with BS EN 14476. As the manufacturer of Nemesis eH2O, we have witnessed an enormous increase in demand for both sprayable and foggable product. This is because, while hand washing can help protect individuals, effective spraying of touch points is also essential, coupled with the fogging of large spaces to decontaminate surfaces and viral aerosols. A summary of the advantages of HOCl was recently published in in the Journal of Oral and Maxillofacial Surgery.7
The paper
commented that an ideal disinfectant and sanitiser must be non-toxic, non-corrosive, effective in various forms, and relatively inexpensive. The paper reviewed the evidence for using HOCl on a daily basis and determined that it can be used with a high predictability for disinfecting against the COVID-19 virus. The US Environmental Protection Agency has recommended numerous disinfectants against COVID-19, including HOCl. The authors also addressed the method of application, assessing the evidence of successful application by surface spraying or by fogging. Interestingly, the paper claimed that the ability of a sprayer to make smaller particles may help a solution’s molecules to be suspended in the air for a longer period because of their low settling velocity, which may increase the solution’s chance of coming into contact with pathogens and deactivating them. The paper concluded that HOCl may be the disinfectant of choice for coronaviruses. In summary, it is becoming clear that
SARS-CoV-2 ‘likes’ cool temperatures with a lack of UV light, and it can spread easily in the fine particles that are emitted by infected individuals. Frequent hand washing, facemasks, social distancing and contact tracing will all help to reduce the spread of infection but, for vulnerable individuals, more effective and comprehensive disinfection is necessary. It is good news, therefore, that coronavirus is relatively easy to kill with disinfectants, such as HOCl, that are not harmful to humans and animals. CSJ
References 1 Kampf, G, et al. (January, 2020) Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. Journal of Hospital Infection.
2 van Doremalen N, et al. (March, 2020) Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. New England Journal of Medicine.
3 Fennelly K P. (July, 2020) Particle sizes of infectious aerosols: implications for infection control. The Lancet Respiratory Medicine.
4 Riddell et al. (October, 2020) The effect of temperature on persistence of SARS-CoV-2 on common surfaces. Virology Journal.
5 Ratnesar-Shumate S, et al. (July, 2020). Simulated sunlight rapidly inactivates SARS-CoV-2 on surfaces. The Journal of Infectious Diseases.
6 Schuit M, et al. (August, 2020). Airborne SARS- CoV-2 is rapidly inactivated by simulated sunlight. The Journal of Infectious Diseases.
7 Michael S, et al, Hypochlorous Acid: A Review, Journal of Oral and Maxillofacial Surgery, Volume 78, Issue 9, September 2020, Pages 1461-1466,
https://doi.org/10.1016/j.joms.2020.06.029
About the author
Adrian Gee-Turner, Dip M FCIM, spent over 30 years working in the UK and Japan with medical technologies relating to the management of aerosols. He is currently a Director of L’EAU, a consultancy specialising in bringing new technologies to market. The disinfectant Nemesis eH2O is the latest brand to benefit from his company’s assistance. The product contains hypochlorous acid, a chemical with well-established antimicrobial activity but with a reputation for poor stability and a short shelf-life. The manufacturer of Nemesis eH2O (Sterling Presentation Health) has solved this issue and offers stabilised HOCl with a 12-month shelf-life. Killing 99.9999% of harmful bacteria on contact, it is effective against a broad spectrum of pathogens including Coronaviruses, Influenza, E. coli, S. aureus, Norovirus, MRSA and C. difficile.
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