Contamination of air and surfaces in workplaces with SARS-CoV-2 virus: a systematic review

Objectives

This systematic review aimed to evaluate the evidence for air and surface contamination of workplace environments with SARS-CoV-2 RNA and the quality of the methods used to identify actions necessary to improve the quality of the data.

Methods

We searched Web of Science and Google Scholar until 24^th December 2020 for relevant articles and extracted data on methodology and results.

Results

The vast majority of data come from healthcare settings, with typically around 6 % of samples having detectable concentrations of SARS-CoV-2 RNA and almost none of the samples collected had viable virus. There were a wide variety of methods used to measure airborne virus, although surface sampling was generally undertaken using nylon flocked swabs. Overall, the quality of the measurements was poor. Only a small number of studies reported the airborne concentration of SARS-CoV-2 virus RNA, mostly just reporting the detectable concentration values without reference to the detection limit. Imputing the geometric mean air concentration assuming the limit of detection was the lowest reported value, suggests typical concentrations in health care settings may be around 0.01 SARS-CoV-2 virus RNA copies/m³. Data on surface virus loading per unit area were mostly unavailable.

Conclusion

The reliability of the reported data is uncertain. The methods used for measuring SARS-CoV-2 and other respiratory viruses in work environments should be standardised to facilitate more consistent interpretation of contamination and to help reliably estimate worker exposure.

Key messages

• What is already known about this subject?

  • Low level contamination of air and surfaces in hospitals with SARS-CoV-2 RNA have been reported during the Covid-19 pandemic.

  • Limited data have published from non-healthcare settings.

• What are the new findings?

  • Typically, around 6% of air and surface samples in hospitals were positive for SARS-COV-2 RNA, although there is very limited data for non-healthcare settings.

  • The quality of the available measurement studies is generally poor, with little consistency in the sampling and analytical methods used.

  • Few studies report the concentration of SARS-CoV-2 in air or as surface loading of virus RNA, and very few studies have reported culture of the virus.

  • The best estimate of typical air concentrations in health care settings is around 0.01 SARS-CoV-2 virus RNA copies/m³

• How might this impact on policy or clinical practice in the foreseeable future?

  • There should be concerted efforts to standardise the methods used for measuring SARS-CoV-2 and other respiratory viruses in work environments.