The efficacy, effectiveness and safety of SARS-CoV-2 disinfection methods (including ozone machines) in educational settings for children and young people

While evidence for the importance of transmission of SARS-CoV-2 from contaminated surfaces is limited, ozone disinfection methods have been considered for surface cleaning as a response to stopping the spread of the virus in educational settings. This rapid evidence summary aimed to search the available literature and summarise findings on the surface survival of SARS-CoV-2, efficacy and effectiveness of ozone machines against SARS-CoV-2, and benefits and harms caused by using these cleaning technologies, including their impact on health. Alternative cleaning technologies, such as light-based technologies and hydrogen peroxide vapour, were also investigated. Findings indicate that gaseous ozone can inactivate different bacteria and viruses, although there is a lack of direct evidence investigating the effect of these cleaning methods on SARS-CoV-2 in real-world settings, specifically in schools. However, regarding harm, ozone is a highly reactive oxidising agent, and high concentrations can contribute to decay of building materials, and health issues (mainly respiratory) by direct exposure or by-product formation. Therefore, leading environmental health organisations do not recommend the use of ozone cleaning technologies in real-world settings, such as schools. Research and policy focus may need to shift towards other interventions that could help reduce transmission, and consequently minimise disruption to education. Funding statementThe Wales Centre for Evidence Based Care was funded for this work by the Wales Covid-19 Evidence Centre, itself funded by Health & Care Research Wales on behalf of Welsh Government. TOPLINE SUMMARYO_ST_ABSWhat is a Rapid Evidence Summary?C_ST_ABSThis Rapid Evidence Summary was completed in two weeks to inform policy- decision making. It is based on a systematic search of the literature, conducted in September 2021. Priority is given to studies representing robust evidence synthesis. No quality appraisal or evidence synthesis are conducted, and the summary should be interpreted with caution. Background / Aim of Rapid Evidence SummarySeveral non-touch disinfectant methods including ozone, light-based technologies, and hydrogen peroxide are being considered to reduce the risk of SARS-CoV-2 virus transmission to children and young people in educational settings. Concerns have been raised about the evidence of efficacy, effectiveness and safety of these technologies in these settings. We aimed to address the following research questions: O_LIWhat is the evidence for the surface survival of SARS-CoV-2? C_LIO_LIWhat is the evidence for the efficacy (in vitro) and real-life effectiveness (in situ) of ozone machines, light-based technologies and hydrogen peroxide vapour as air or surface disinfectants against SARS-CoV-2? C_LIO_LIWhat are the potential health effects of ozone, in particular for children and young people and the benefits and harms of using ozone machines? C_LI Key FindingsO_ST_ABSExtent of the evidence baseC_ST_ABSA total of 82 tertiary, secondary and primary evidence sources was included Recency of the evidence baseMost studies were published 2020-21, indirect evidence was included from earlier work from 2006 onwards Summary of findingsO_LISARS-CoV-2 fragments can be found on surfaces up to seven days later in the community but there is a lack of evidence whether these are viable C_LIO_LIWhen accounting for both surface survival data and real-world transmission factors, the risk of surface transmission after a person with COVID-19 has been in an indoor space is minor after 72 hours, regardless of last clean C_LIO_LIThere is evidence from experimental settings that ozone machines, light-based technologies and hydrogen peroxide do inactivate coronaviruses, including SARS-CoV-2 C_LIO_LIThere is a lack of evidence for the effectiveness of ozone machines, light- based technologies and hydrogen peroxide in real-world settings C_LIO_LIThere are uncertainties about training requirements for staff, methods for assurance of ozone removal and monitoring of occupational exposure C_LIO_LIThere is strong evidence of a causal relationship between short term ozone exposure and respiratory health issues; these can occur at very low concentrations of ozone; children with asthma are more at risk C_LIO_LIRooms using ozone machines need to be sealed off to avoid leakage of the ozone gas which is toxic at high concentrations C_LIO_LIOzone may react with materials in the room to form secondary pollutants (e.g. formaldehyde) C_LI The best quality evidenceO_LIThe US EPA 2021 does not recommend ozone for air cleaning and the UK SAGE EMG 2020a does not recommend technologies that "may generate undesirable secondary chemical products that could lead to health effects such as respiratory or skin irritation (medium confidence). These devices are therefore not recommended unless their safety and efficacy can be unequivocally and scientifically demonstrated by relevant test data" (SAGE EMG 2020a). C_LI Policy implicationsO_LIThere is no direct evidence for the effectiveness and safety of using ozone machines to deactivate SARS-CoV-2 in real-world educational settings for children, young people and staff C_LIO_LIThere is evidence for the risk of potential harm to children and young people of ozone machines from either ozone or secondary pollutants, in particular but not only, if used in uncontrolled ways in educational settings C_LI Strength of Evidence to dateO_LImoderate evidence for the surface survival of SARS-CoV-2 C_LIO_LIstrong evidence of causal relationship between short term ozone exposure and respiratory health issues C_LI