Inactivation Times from 290-320 nm UVB in Sunlight for SARS Coronaviruses CoV and CoV-2 using Satellite Data for the Sunlit Earth

Abstract:

UVB in sunlight, 290 – 320 nm, can inactivate SARS CoV and SARS CoV-2 viruses on surfaces and in the air. Laboratory exposure to ultraviolet irradiance in the UVC range inactivates many viruses and bacteria in times less than 30 minutes. Estimated UVB doses from sunlight in J/m², weighted by a virus action spectrum, are obtained from radiative transfer calculations using OMI satellite atmospheric data for ozone, clouds, and aerosols. For SARS CoV, using an assumed UVC dose near the middle of the range of measured values, D₉₀ = 40 J/m², 90% inactivation times T₉₀ are estimated for exposure to midday 10:00 – 14:00 direct plus diffuse sunlight and for nearby locations in the shade (diffuse UVB only). Recent direct measurements of UVB sunlight inactivation of the SARS CoV-2 virus that causes COVID-19 show much shorter inactivation times on the order of less than 10 minutes depending on latitude, season, and time of the day. The equivalent UVC 254 nm D₉₀ dose for SARS CoV-2 is estimated as 3.2 J/m² for viruses on a steel mesh surface and 6.5 J/m² for viruses in a growth medium. For the assumed D₉₀ = 40 J/m² model applicable to SARS CoV viruses, calculated estimates show that near noon 11:00 – 13:00 clear-sky direct sunlight gives values of T₉₀ < 90 minutes for mid-latitude sites between March and September and less than 60 minutes for many equatorial sites for all 12 months of the year. For SARS CoV-2 D₉₀=3.2 J/m², clear-sky T₉₀ on a surface ranges from 4 minutes in the equatorial zone to less than 30 minutes in a geographic area forming a near-circle with solar zenith angle < 60^O centered on the subsolar point for local solar times from 09:00 to 15:00 hours.