Air pollution and COVID-19 mortality

Not everyone's risk of dying of COVID-19 is the same, and now a new paper has linked long-term exposure to air pollution to a much higher risk of death. The paper authors have estimated, for the first time, the proportion of deaths from coronavirus that could be attributed to air pollution in every country in the world. Andrea Pozzer, a scientist in ICTP's Earth System Physics section, led the collaboration with scientists at the Max Planck Institute for Chemistry and the University Medical Centre Mainz.

The study, published in the 26 October edition of the scientific journal Cardiovascular Research, estimated that approximately fifteen percent of deaths worldwide from COVID-19 could be attributed to long-term exposure to air pollution. In Europe the proportion was about 19%, in North America it was 17%, and in East Asia 27%.

These proportions are an estimate of “the fraction of COVID-19 deaths that could be avoided if the population were exposed to lower counterfactual air pollution levels without fossil fuel-related and other anthropogenic emissions," write the paper authors. 

Pozzer explains that this finding does not demonstrate a direct cause-effect relationship between air pollution and COVID-19 mortality. It is rather an indirect effect: “Our estimates show the importance of pollution on fatal health outcomes of the virus infection, i.e. by aggravating co-morbidities [other health conditions]”.

Estimates show a very diverse picture for individual countries, for example, that anthropogenic air pollution contributed to 29% of coronavirus deaths in the Czech Republic, 27% in China, 26% in Germany. The proportion is lower for instance in Italy (15%) or Brazil (12%). Single figures are estimated for Israel (6%), Australia (3%) and New Zealand (1%).

“Although our results have significant uncertainties, we can clearly distinguish the contribution of air pollution to COVID-19 mortality," says Pozzer. "Nevertheless, the actual mortality is influenced by many additional factors such as the country's health system.”

Thomas Münzel, a co-author from Cardiology Center at the University Medical Center Mainz, explained the health effects of air pollution: “When people inhale polluted air, the very small polluting particles, migrate from the lungs to the blood and blood vessels, causing inflammation and severe oxidative stress, which is an imbalance between free radicals and oxidants in the body that normally repair damage to cells.” This causes damage to the inner lining of arteries, the endothelium, and leads to the narrowing and stiffening of the arteries. The COVID-19 virus also enters the body via the lungs, causing similar damage to blood vessels.

“If both long-term exposure to air pollution and infection with the COVID-19 virus come together," Münzel added, "then we have an additive adverse effect on health, particularly with respect to the heart and blood vessels, which leads to greater vulnerability and less resilience to COVID-19. If you already have a heart disease, then both air pollution and coronavirus infection will aggravate disorders that can lead to heart attacks, heart failure and strokes. Particulate matter seems to increase the activity of a receptor on cell surfaces, called ACE-2, that is known to be involved in the way COVID-19 infects cells. Hence, we have a ‘double hit’: air pollution damages the lungs and increases the activity of ACE-2, which in turn leads to enhanced uptake of the virus by the lungs and probably by the blood vessels and the heart.”

Using data from a number of recently published epidemiological studies, the researchers confirmed that in areas with moderate air pollution, the risk of dying from the disease compared to areas with relatively clean air was more than 80% higher, while in heavily polluted regions the risk was twice as high. Thanks to global fine particulate air pollution data obtained from satellite data, ground-based air pollution networks and a numerical model, the authors determined the regional proportion of COVID-19 deaths attributable to air pollution. 

In their paper, the authors end with a clear message to decision makers: “Our results suggest the potential for substantial benefits from reducing air pollution exposure, even at relatively low fine particulate air pollution levels. A lesson from our environmental perspective of the COVID-19 pandemic is that the quest for effective policies to reduce anthropogenic emissions, which cause both air pollution and climate change, needs to be accelerated. The COVID-19 pandemic ends with the vaccination of the population or with herd immunity through extensive infection. However, there are no vaccines against poor air quality and climate change. The remedy is to mitigate emissions. The transition to a green economy with clean, renewable energy sources will further both environmental and public health locally through improved air quality and globally by limiting climate change.”

“Regional and global contributions of air pollution to risk of death from COVID-19” Andrea Pozzer, Francesca Dominici, Andy Haines, Christian Witt, Thomas Münzel, and Jos Lelieveld Cardiovascular Research, cvaa288, https://doi.org/10.1093/cvr/cvaa288