People who contract Covid-19 are more likely to suffer severe symptoms if they have been exposed to air pollution for long periods.
A study found that people who live in places where there are high levels of the atmospheric pollutant nitrogen dioxide had higher chances of ending up in intensive care units (ICUs) or of needing mechanical ventilation after they had caught Covid.
Nitrogen dioxide is released into the atmosphere when fossil fuels are burned, and the gas is known to have harmful effects on people’s lungs. In particular, endothelial cells – which form a thin membrane lining the inside of the heart and blood vessels – become damaged, and this inhibits the transfer of oxygen from inhaled breath to a person’s blood.
“Our results show a positive association between long-term nitrogen dioxide exposure and Covid-19 fatality and Covid-19 incidence rate,” said the team of German researchers, who were led by Susanne Koch, of Universitätsmedizin Berlin, a large teaching hospital.
Scientists had previously made links between Covid and air pollution, but few studies have concentrated on cases that were particularly severe or on underlying health conditions in those affected by the disease.
Koch and her team used air pollution data to calculate average levels of nitrogen dioxide for each county in Germany. The highest was found in Frankfurt, while the lowest was experienced in Suhl, a small county in Thuringia, the group revealed in its report, which was presented last week to Euroanaesthesia, the annual meeting of the European Society of Anaesthesiology and Intensive Care in Milan.
The group also studied data on how many Covid patients in German hospitals had required ICU treatment and mechanical ventilation during one month in 2020. These figures were adjusted for other factors, such as pre-existing health conditions.
After analysing their results, the team reported that on average, 28 ICU beds and 19 ventilators were needed for Covid patients in each of the 10 counties that had the lowest long-term nitrogen dioxide exposure. These figures contrasted with an average of 144 ICU beds and 102 ventilators needed in the 10 counties with the highest long-term exposure.
The research has worrying implications. In the UK, 75% of urban areas in 2019 had illegal levels of air pollution, underscoring the fact that the British government has made almost no progress on legal obligations that should have been met in 2010. During lockdown, there was a temporary decrease in nitrogen in some areas. However, traffic and pollution are returning to past levels in many towns and cities.
According to the Royal College of Physicians, air pollution causes the equivalent of 40,000 early deaths a year, and has been linked to cancer, asthma, stroke and heart disease, diabetes, obesity and changes linked to dementia. Now evidence is mounting that Covid should be added to this list.
The German study did not prove a causative relationship between air pollution and severe Covid, the researchers admitted. However, they did suggest a plausible causal link that could explain the relationship between severe Covid and levels of nitrogen dioxide in the atmosphere.
Coronavirus is known to bind to the Ace-2 receptor when it enters cells after infecting a person. This receptor has many key roles, one of which involves helping the body to regulate levels of angiotensin II, a protein that increases inflammation. In other words, Ace-2 helps to put the brakes on inflammation.
However, when Covid binds to Ace-2, these brakes are removed. It is also known that air pollution causes a similar release of controls over angiotensin II. So the combination of Covid and long-term air pollution exposure would lead to more severe inflammation, more severe Covid and more need for ICUs and mechanical ventilation, the team argued.
“Exposure to ambient air pollution can contribute a range of other conditions, including heart attacks, strokes, asthma and lung cancer, and will continue to harm health long after the Covid-19 pandemic ends,” added Koch. “A transition to renewable energy, clean transportation and sustainable agriculture is urgently needed to improve air quality. Reducing emissions won’t just help to limit climate crisis, it will improve the health and the quality of life of people around the world.”