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

  1. Deborah Edwards
  2. Judit Csontos
  3. Elizabeth Gillen
  4. Ruth Lewis
  5. Alison Cooper
  6. Micaela Gal
  7. Rebecca-Jane Law
  8. Adrian Edwards

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Abstract

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 statement

The 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 SUMMARY

What is a Rapid Evidence Summary?

This 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 Summary

Several 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:

  • What is the evidence for the surface survival of SARS-CoV-2?

  • What 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?

  • What are the potential health effects of ozone, in particular for children and young people and the benefits and harms of using ozone machines?

Key Findings

Extent of the evidence base

A total of 82 tertiary, secondary and primary evidence sources was included

Recency of the evidence base

Most studies were published 2020-21 , indirect evidence was included from earlier work from 2006 onwards

Summary of findings

  • SARS-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

  • When 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

  • There is evidence from experimental settings that ozone machines, light-based technologies and hydrogen peroxide do inactivate coronaviruses, including SARS-CoV-2

  • There is a lack of evidence for the effectiveness of ozone machines, light- based technologies and hydrogen peroxide in real-world settings

  • There are uncertainties about training requirements for staff, methods for assurance of ozone removal and monitoring of occupational exposure

  • There 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

  • Rooms using ozone machines need to be sealed off to avoid leakage of the ozone gas which is toxic at high concentrations

  • Ozone may react with materials in the room to form secondary pollutants (e.g. formaldehyde)

The best quality evidence

  • The 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).

Policy implications

  • There 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

  • There 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

Strength of Evidence to date

  • moderate evidence for the surface survival of SARS-CoV-2

  • strong evidence of causal relationship between short term ozone exposure and respiratory health issues

Article activity feed

  1. ScreenIT

    SciScore for 10.1101/2022.02.21.22271281: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    COVID-19 specific and general repositories of evidence reviews; the reference databases PubMed, Medline, Embase and Web of Science; and websites of key originations were searched on 8th to 10th September 2021.
    PubMed
    suggested: (PubMed, RRID:SCR_004846)
    Medline
    suggested: (MEDLINE, RRID:SCR_002185)
    Embase
    suggested: (EMBASE, RRID:SCR_001650)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2022.02.21.22271281 on medRxiv