Air pollution: A driver of COVID-19 morbidity and mortality

The COVID-19 pandemic further emphasises the adverse health impacts of air pollution. Particulate pollution contributes to about 15% of COVID-19 mortality worldwide. As many people around the globe live in places with unhealthy levels of air pollution, improvement of air quality can be a potential means to improve health.

The best data on air pollution exists for particulate matter (PM), nitrogen dioxide (NO₂), ozone (O₃), and sulphur dioxide (SO₂). The deposition of PM in the lungs can cause pulmonary injuries such as asthma, pulmonary dysfunction, pneumonia, and lung cancer. As Prof. Meredith McCormack (John Hopkins University, Baltimore, USA) pointed out, the size of particles is directly linked to their potential for causing harm to the airways: particles that are smaller than 2.5 μm (PM2.5) can reach the terminal bronchioles and enter alveoli [1].

Air pollutants do not only impair the health of the respiratory system directly but can also increase the fatality of viral infections. Target organs of both COVID-19 and air pollution are the central nervous system, the lungs, and the heart. Prof. McCormack commented that different mechanisms can explain the detrimental effect of air pollution on a SARS-CoV-2 infection. Air pollutants impair the immune response, thus facilitating viral penetration and replication. Furthermore, they exaggerate the inflammatory and oxidative stress response. “In addition, PM and NO₂ exposure in vitro leads to overexpression of angiotensin-converting enzyme (ACE)2, which is a cellular target of SARS-CoV-2 that can lead to enhanced entry, infection, and replication,” Prof. McCormick elaborated. There are estimates that particulate pollution from anthropogenic sources contributes to about 15% of COVID-19 mortality worldwide [2].

“We will see more studies like this, and air pollutants do not only influence mortality, but also morbidity,” Prof. McCormack said. Only recently the American Lung Association published the report “State of the air 2021”; according to this statement, even in a highly industrialised nation such as the USA, more than 4 in 10 inhabitants live in places with unhealthy levels of air pollution.

Vice versa, cleaner air is a strategy to improve outcomes and reduce the impact of COVID-19. “Areas of improvement in air quality are opportunities to address health disparities around the globe and COVID-19 brings a lens for us to reconsider air quality as a potential means to improve health,” concluded Prof. McCormack.

1. McCormack M, et al. Learning from our past and forging new frontiers in the COVID 19 era.... air pollution exposure as a susceptibility factor for COVID 19 infection. Session A009: From dawn to dusk: pollutant exposures and susceptibility to respiratory infections. ATS 2021 International conference, 14-19 May 2021.
2. Pozzar A, et al. Cardiovasc Res 2020;116(14):2247-53.

 



Posted on 20 May 20214 August 2021