Exposure to air pollution could be responsible for 15% of global COVID-19 cases, a new study published on Tuesday in the Cardiovascular Research Journal found. 

The research, conducted by Andrea Pozzer, Francesca Dominici, Andy Haines, Christian Witt, Thomas Münzel, and Jos Leliveld, analyzed the respiratory viruses SARS and COVID-19 to understand the effects of air pollution. 

By comparing the number of positive SARS and COVID-19 cases to satellite data and air pollution monitoring networks, the researchers were able to investigate how air pollution increases the likelihood and severity of respiratory viruses.

When people inhale polluted air, the chemicals travel from the lungs and can cause severe oxidate stress on the blood and blood vessels, according to the study. Oxidants in the body usually repair damage to cells, so when they are under stress the entire body can be affected. 

This can cause damage to the arteries and endothelium (tissue in the blood vessels, heart, and lymphatic vessels) which puts people at risk of serious diseases or health complications. 

“Air pollution, especially by fine particulate matter, is responsible for pulmonary and cardiovascular diseases, leading to excess mortality from COPD [chronic obstructive pulmonary disease], lung cancer, pneumonia, heart attacks, and strokes,” Leliveld told Global Citizen.

These conditions make people more at risk of COVID-19 and increase the threat of mortality if people test positive.

Another researcher, Pozzer, clarified to Global Citizen that it is “therefore not clear if air pollution increases the chance of being infected [with COVID-19] but for sure increases the chances of a fatal outcome, possibly due to pre-existing conditions.”

The authors were able to calculate the percentage of COVID-19 cases that could be influenced by air pollution for every country in the world. 

Estimates show that air pollution was responsible for 29% of COVID-19 deaths in the Czech Republic; 27% in China; 26% in Germany; 22% in Switzerland; 21% in Belgium; 19% in The Netherlands; 18% in France; 16% in Sweden; 15% in Italy; 14% in the UK; 12% in Brazil; 11% in Portugal; 8% in the Republic of Ireland; 6% in Israel; 3% in Australia; and just 1% in New Zealand.

The researchers explained in a press release that since the number of COVID-19 cases around the world is constantly increasing, is it not possible to give an exact or final number of COVID-19 cases that can be attributed to air pollution. 

“We hope to show (again) that air pollution is a serious health risk factor that needs to be controlled, and that clean air is a fundamental human need,” Leliveld said about the motivation for the study. 

Even without the COVID-19 pandemic, air pollution is a serious threat to the respiratory health of people around the world. The World Health Organization estimates that 7 million people die from exposure to air pollution every year. 

Low and middle-income countries typically have less clean air, which puts people in developing countries more at risk of being exposed to polluted air. 

Both Pozzer and Leliveld emphasized the importance of finding solutions to lower human emissions. 

“The pandemic ends with the vaccination of the population or with herd immunity through extensive infection of the population,” the authors wrote in the conclusion of their research. “However, there are no vaccines against poor air quality and climate change. The remedy is to mitigate emissions.”