Severe Covid cases more likely in places with high air pollution, study finds

Long-term exposure to pollution is linked to a greater risk of severe Covid-19, according to new research that calls for an urgent transition to clean energy to improve air quality.

The yet-to-be peer-reviewed research, to be presented at Euroanaesthesia – the annual meeting of the European Society of Anaesthesiology and Intensive Care (ESAIC) in Milan – says people in counties with higher levels of the pollutant nitrogen dioxide (NO₂) are more likely to need ICU care and mechanical ventilation if they contract Covid.

The findings point to the need for an immediate transition to renewable energy, clean transportation, and sustainable agriculture to improve air quality across the world, say researchers from Charite – Universitatsmedizin Berlin.

Previous research, even before the onset of the Covid-19 pandemic, has linked air pollution exposure to a range of other conditions such as heart attacks, strokes, asthma and lung cancer.

Since the pandemic began in December 2019 in Wuhan, China, several studies across the world have assessed the link between air quality and Covid.

However, scientists say few of these have focused on disease severity, taking into account population density, underlying health conditions, as well as other factors affecting Covid-19 impact.

In the new research, they analysed the impact of long-term air pollution on the need for ICU treatment and mechanical ventilation of COVID-19 patients.

Researchers assessed air pollution data from 2010 to 2019 to calculate the long-term annual mean level of NO₂ for each county in Germany.

They found that this ranged across the country from 4.6 microgram per cubic metre (µg/m³) to 32µg/m³, with the highest level in Frankfurt and the lowest level in Suhl, a small county in Thuringia.

Scientists also assessed how many Covid-19 patients in each of the hospitals in 392 of Germany’s 402 counties needed ICU treatment and mechanical ventilation.

Researchers also accounted for patients’ demographic factors such as population density, age, and sex distribution, as well as socio-economic factors and health parameters like pre-existing health conditions that affect COVID-19 severity.

They found that there was a greater need for ICU treatment and mechanical ventilation of COVID-19 patients in counties with higher long-term annual mean NO₂ levels.

For every 1 µg/m³ increase in long-term annual mean NO₂ concentration, there was a linked 3.2 per cent increase in the number of ICU beds occupied by Covid-19 patients and a 3.5 per cent increase in the number of patients needing mechanical ventilation, scientists said.

On average, they said 28 ICU beds and 19 ventilators were needed for Covid-19 patients in each of the ten counties with the lowest long-term NO₂ exposure, during the month studied.

In comparison, an average of 144 ICU beds and 102 ventilators were needed in the ten counties with the highest long-term NO₂ exposure.

While their findings do not prove a cause-effect relationship between pollution and Covid-19 outcomes, scientists say there is a potential biological explanation connecting the two.

They say the ACE-2 receptor protein on the surface of human cells, which the Covid-19 virus uses as entry gate to infect cells, has many key roles in the body, including the regulation of a angiotensin II – a protein that increases inflammation.

Through its regulatory action, researchers say ACE-2 helps “put the brakes” on inflammation. However, when the novel coronavirus binds to ACE-2, they say these brakes are removed.

Scientists speculate air pollution also “releases the brakes” and the combination of Covid-19 and long-term air pollution exposure could lead to more severe inflammation and more severe Covid-19.

The new findings are in line with other recent studies linking long-term NO₂ exposure with a higher Covid-19 incidence and a higher fatality rate.

A previous study from Harvard TH Chan School of Public Health in the US had found a link between long-term air pollution exposure and Covid-19 outcomes.

It found an 11 per cent increase in mortality from Covid-19 for every 1µg/m³ increase in air pollution, adding that Americans on average breathe air with about 8µg/m³ particulate matter.

“In places where air pollution is a chronic problem, we have to pay particular attention to individuals who may be more exposed or vulnerable than others to polluted air, such as the homeless and those with chronic medical problems,” Aaron Bernstein, one of the co-authors of the study, had said.

Scientists caution that people living in such places may need more support than they did “even before coronavirus came along.”

“Long-term exposure to NO₂ long before the pandemic may have made people more vulnerable to more severe Covid-19 disease,” Susanne Koch from Charite – Universitatsmedizin Berlin said in a statement.

“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,” Dr Koch added.