The Air and Viruses We Breathe: Assessing the Effect the PM2.5 Air Pollutant Has on the Burden of COVID-19

Evidence suggests an association between air pollutant exposure and worse outcomes for respiratory viral diseases, like COVID-19. However, does breathing polluted air over many years affect the susceptibility to SARS-CoV-2 infection or severity of COVID-19 disease, and how intense are these effects? As climate change intensifies, air pollutant levels may rise, which might further affect the burden of respiratory viral diseases. We assessed the effect of increasing exposure to PM2.5 (particulate matter = 2.5 microns in diameter) on SARS-CoV-2 susceptibility or COVID-19 severity and projected the impact on infections and hospitalisations over two years. Simulations in a hypothetical, representative population show that if exposure affects severity, then hospital admissions are projected to increase by 5-10% for a one-unit exposure increase. However, if exposure affects susceptibility, then infections would increase with the potential for onward transmission and hospital admissions could increase by over 60%. Implications of this study highlight the importance of considering this potential additional health and health system burden as part of strategic planning to mitigate and respond to changing air pollution levels. It is also important to better understand at which point PM2.5 exposure affects SARS-CoV-2 infection through to COVID-19 disease progression, to enable improved protection and better support of those most vulnerable.

What Impact Will Worsening Air Pollution Have on the Burden of Covid-19?

Background: Evidence suggests association between long-term exposure to air pollutants and increased risk of becoming infected with SARS-CoV- 2, the causative agent of COVID-19, and increased severity of COVID-19. However, it remains unclear whether breathing more polluted air over many years affects susceptibility to infection or only affects disease severity, with uncertainty around the intensity of these associations. It has been estimated that anthropogenic emissions have contributed to over 10% of the over 660 million cases of SARS-CoV-2 and the over 7.5 million COVID-19 deaths reported worldwide over the course of the pandemic. Furthermore, as the world continues to warm and if air pollution levels increase, then so might the burden of respiratory infectious disease, including COVID-19. Method(s): Here we explore the potential impact of long-term exposure to increasing levels of particulate matter 2.5 microns or less in diameter (PM2.5) (+1 to +5 mug/m3) assuming an association on either (1) SARS-CoV-2 susceptibility or (2) COVID-19 disease severity by projecting SARS-CoV-2 infections and COVID-19-related hospital admissions over a two-year period. Simulations were conducted using a SARS-CoV-2 transmission model in a global setting capturing age and comorbidity risk, considering seasonality, emerging variants, and vaccination and treatment options. We model linear, log, and log10 relationships between these associations. Result(s): We show that if long-term exposure to higher levels of air pollution only affects COVID-19 severity, then as expected, the projected number of COVID-19-related hospitalisations would proportionally increase. However, if exposure directly affects the susceptibility of becoming infected, then while infections would be higher, hospitalizations would also be even higher due to the potential for onward transmission. This aligns with associations between air pollution and other respiratory infections and their associated health outcomes. Conclusion(s): The anticipated additional impact air pollution is having on the public health burden of respiratory infectious disease, like COVID-19, should be considered in strategic action plans to mitigate and adapt to changing levels of air pollution. It is important to better understand at which point air pollution affects SARS-CoV-2 infection acquisition through to disease progression, to enable improved protection and to better support those most vulnerable. Modelled impact of air pollution on COVID-19. The projected cumulative impact of long-term exposure to incrementally higher PM2.5 levels (+1 to +5 mug/m3) affecting either SARS-CoV-2 susceptibility or COVID-19 disease severity on cumulative SARS-CoV-2 infections and COVID-19-related hospital admissions over a two-year period in a global setting of 100,000 people. Age and comorbidity risk are captured, seasonality considered, and it is assumed SARS-CoV-2 variants of concern (with 10% more infectious and 20% more immune-evading than the previous variant, and Omicron-level severity) emerge every six months, and COVID-19 vaccination and treatment (monoclonalantibody PrEP and antivirals) are implemented for all those eligible. While the associations between PM2.5 exposure and either SARS-CoV-2 susceptibility or COVID-19 disease severity remains unclear and there is much uncertainty around estimated assumptions, here we show a modelled log10 relationship between these two potential associations. COVID-19: coronavirus disease 2019. PM2.5: particulate matter 2.5 microns or less in diameter. PrEP: pre-exposure prophylaxis. SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.