Linkages between COVID-19, solar UV radiation, and the Montreal Protocol

Abstract

There are several connections between coronavirus disease 2019 (COVID-19), solar UV radiation, and the Montreal Protocol. Exposure to ambient solar UV radiation inactivates SARS-CoV-2, the virus responsible for COVID-19. An action spectrum describing the wavelength dependence of the inactivation of SARS-CoV-2 by UV and visible radiation has recently been published. In contrast to action spectra that have been assumed in the past for estimating the effect of UV radiation on SARS-CoV-2, the new action spectrum has a large sensitivity in the UV-A (315–400 nm) range. If this “UV-A tail” is correct, solar UV radiation could be much more efficient in inactivating the virus responsible for COVID-19 than previously thought. Furthermore, the sensitivity of inactivation rates to the total column ozone would be reduced because ozone absorbs only a small amount of UV-A radiation. Using solar simulators, the times for inactivating SARS-CoV-2 have been determined by several groups; however, many measurements are affected by poorly defined experimental setups. The most reliable data suggest that 90% of viral particles embedded in saliva are inactivated within ~ 7 min by solar radiation for a solar zenith angle (SZA) of 16.5° and within ~ 13 min for a SZA of 63.4°. Slightly longer inactivation times were found for aerosolised virus particles. These times can become considerably longer during cloudy conditions or if virus particles are shielded from solar radiation. Many publications have provided evidence of an inverse relationship between ambient solar UV radiation and the incidence or severity of COVID-19, but the reasons for these negative correlations have not been unambiguously identified and could also be explained by confounders, such as ambient temperature, humidity, visible radiation, daylength, temporal changes in risk and disease management, and the proximity of people to other people. Meta-analyses of observational studies indicate inverse associations between serum 25-hydroxy vitamin D (25(OH)D) concentration and the risk of SARS-CoV-2 positivity or severity of COVID-19, although the quality of these studies is largely low. Mendelian randomisation studies have not found statistically significant evidence of a causal effect of 25(OH)D concentration on COVID-19 susceptibility or severity, but a potential link between vitamin D status and disease severity cannot be excluded as some randomised trials suggest that vitamin D supplementation is beneficial for people admitted to a hospital. Several studies indicate significant positive associations between air pollution and COVID-19 incidence and fatality rates. Conversely, well-established cohort studies indicate no association between long-term exposure to air pollution and infection with SARS-CoV-2. By limiting increases in UV radiation, the Montreal Protocol has also suppressed the inactivation rates of pathogens exposed to UV radiation. However, there is insufficient evidence to conclude that the expected larger inactivation rates without the Montreal Protocol would have had tangible consequences on the progress of the COVID-19 pandemic. Graphical abstract

Stratospheric ozone, UV radiation, and climate interactions

“…An action spectrum for the inhibition of SARS-CoV-2 (the virus responsible for the COVID-19 disease) was recently measured. This spectrum is discussed by Bernhard et al [ 2 ].…”

“…It focuses on the effects of changes in the ozone layer on climate and ultraviolet (UV) radiation at the Earth’s surface, the interactions between UV radiation and climate, and on the influence of other geophysical parameters affecting UV radiation. This assessment sets the stage for subsequent assessments in this series that address the consequences of the interconnected effects of stratospheric ozone depletion, UV radiation, and climate change on human health [ 1 ] (including the COVID-19 pandemic [ 2 ]), terrestrial [ 3 ] and aquatic [ 4 ] ecosystems, the carbon cycle [ 3 , 4 ], air quality [ 5 ], natural and synthetic materials [ 6 ], and the fate of environmental plastic debris [ 7 ]. These assessments focus on new scientific knowledge that has accumulated since our last comprehensive assessment ( Photochem.…”

The response of aquatic ecosystems to the interactive effects of stratospheric ozone depletion, UV radiation, and climate change

“…The action spectrum of inactivation by UV radiation of SARS-CoV-2 in the air [ 88 ] is somewhat different from other viruses (either DNA or RNA based) in that it shows some sensitivity to UV-A radiation (see Bernhard et al . [ 89 ] , this issue). This suggests that the inactivation of SARS-CoV-2 by solar UV radiation in water could be faster than for other viruses, but more study is needed.…”

“…For both Daphnia and the ciliate, short-wavelength UV-B radiation is the most effective at causing mortality, similar to the wavelengths most effective for damaging DNA and RNA (see action spectra discussion in the COVID assessment, Bernhard et al . [ 89 ], this issue). Collectively, these experiments illustrate that UV-B radiation is detrimental to zooplankton and exposure leads to reduced fitness.…”