Impact of High Solar UV Radiant Exposures in Spring 2020 on SARS-CoV-2 Viral Inactivation in the UK.

Potential for SARS-CoV-2 viral inactivation by solar UV radiation in outdoor spaces in the UK has been assessed. Average erythema effective and UV-A daily radiant exposures per month were higher (statistically significant, P < 0.05) in spring 2020 in comparison with spring 2015-2019 across most of the UK, while irradiance generally appeared to be in the normal expected range of 2015-2019. It was found that these higher radiant exposures may have increased the potential for SARS-CoV-2 viral inactivation outdoors in April and May 2020. Assessment of the 6-year period 2015-2020 in the UK found that for 50-60% of the year, that is most of October to March, solar UV is unlikely to have a significant (at least 90% inactivation) impact on viral inactivation outdoors. Minimum times to reach 90% and 99% inactivation in the UK are of the order of tens of minutes and of the order of hours, respectively. However, these times are best case scenarios and should be treated with caution.