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Air pollution link in 15% of global Covid-19 deaths

About 15% of global deaths from Covid-19 could be attributed to long-term exposure to ambient fine particulate air pollution, a landmark new study has found.

A team of researchers from Germany and Cyprus have, for the first time, estimated the proportion of deaths from the novel coronavirus that could be ascribed to the health effects of poor air quality. The findings were published in the journal Cardiovascular Research.

In Europe, the proportion of deaths amounted to about 19%; North America, 17%; and East Asia, 27%.

The “attributable fraction”’ does not imply a direct cause and effect relationship between air pollution and Covid-19 mortality (although it is possible).

Instead, it refers to the relationship between the two — direct and indirect — by aggravating comorbidities that could lead to fatal health outcomes from being infected with the virus.

The researchers used epidemiological data from the previous United States and Chinese studies of air pollution and Covid-19 and the severe acute respiratory syndrome outbreak in 2003, supported by additional data from Italy. This was combined with satellite data showing global exposure to polluting fine particles (PM2.5) information on atmospheric conditions and ground-based pollution monitoring networks.

This was used to create a model to calculate the fraction of coronavirus deaths that could be attributable to long-term exposure to PM2.5. 

Their results are based on epidemiological data collected up to the third week in June this year.

Particulate matter, the researchers found, seems to increase the activity of a receptor on cell surfaces, called ACE-2, which is known to be involved in the way Covid-19 infects cells. 

“So 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,” says co-author, professor Thomas Münzel from the University Medical Center of the Johannes Gutenberg University, Mainz, in a statement.

A new, although preliminary finding, is that a significant fraction of worldwide Covid-19 mortality is attributable to air pollution, of which up to 60% is related to the use of fossil fuels. “This represents potentially avoidable, excess mortality,” the authors write.

Münzel explains that when people inhale polluted air, very small polluting particles, “the PM2.5, migrates 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 damages the inner lining of arteries, the endothelium, leading 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, and it is now considered to be an endothelial disease. If both long-term exposure to air pollution and infection with the Covid-19 virus come together then we have an additive adverse effect on health, particularly concerning the heart and blood vessels, which leads to greater vulnerability and less resilience to Covid-19. If you already have heart disease, then air pollution and coronavirus infection will cause trouble that can lead to heart attacks, heart failure and stroke.”

The researchers emphasise that the data in the study are from upper-middle and high-income countries, and the representativeness of results for low-income countries may be limited. 

“It is expected that in countries with high levels of aeolian dust, for example in Africa and West Asia, PM2.5 pollution is also a co-factor but with less contribution from human activities. Household air pollution is also likely to be important, being of particular relevance in low-income countries. 

“It will be critical to collect epidemiological evidence from many regions with different socioeconomic and environmental conditions, to support analyses of the Covid-19 pandemic and investigate the role of environmental factors,” the authors note.

The researchers say that a lesson from the environmental perspective of the Covid-19 pandemic is that the quest for effective policies to reduce human-caused emissions, which result in both air pollution and climate change, need to be accelerated. 

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

The transition to a green economy with clean, renewable energy sources, they write, will further both environmental and public health locally. 

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Sheree Bega
Sheree Bega is an environment reporter at the Mail & Guardian.

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