A study by the Barcelona Institute for Global Health (ISGlobal) found that long-term exposure to air pollution can increase the severity of COVID-19 outcomes, including hospital admissions, intensive care unit (ICU) admissions, and death.
The study was based on data from more than 4.6 million adults living in Catalonia in 2020, a region in Spain severely affected by COVID-19.
The Impact of Air Pollution on COVID-19 Severity
Researchers analyzed the annual average levels of fine particulate matter (PM2.5), nitrogen dioxide (NO2), black carbon (BC), and ozone (O3) at each participant’s residential address.
They also gathered data on severe COVID-19 cases, including hospital and ICU admissions, length of hospital stay, and COVID-19-related deaths.
Analysis of the data showed that increases in exposure to these pollutants were linked to significant increases in severe COVID-19 outcomes.
A rise in PM2.5 exposure was associated with a 19% increase in hospital admissions, while an increase in NO2 exposure was linked to a 42% rise in ICU admissions.
An increase in BC exposure was associated with a 6% rise in COVID-19-related mortality.
“These findings add to the evidence highlighting the importance of reducing air pollution levels to improve population health and reduce the incidence of severe respiratory infections,” said Otavio Ranzani, an ISGlobal researcher and the study’s first author.
Understanding the Connection
Several biological mechanisms might explain why long-term air pollution exposure increases the risk of severe COVID-19.
One theory is that air pollution exposure could increase an individual’s risk of developing chronic comorbidities associated with severe COVID-19, like hypertension.
There’s also evidence suggesting that exposure to fine particulate matter may increase the expression of receptors that the SARS-CoV-2 virus binds to, particularly in the lungs.
Additionally, previous studies have linked air pollution exposure with changes in immune defenses essential for mitigating SARS-CoV-2, such as a decrease in the type II interferon response and the antibody response.
Study Methodology
The study was based on data from the Catalan public health system and included primary care, emergency care, and hospital discharge data for acute patients.
The researchers also utilized data from a SARS-CoV-2 surveillance system that tracked PCR and rapid antigen test results.
According to the study’s data, over 340,000 people were diagnosed with COVID-19 in Catalonia in 2020, with 14% requiring hospital admission and 1.4% needing ICU care. In total, there were 10,001 COVID-19-related deaths.
The Takeaway
The researchers believe that their study provides robust evidence of the link between long-term exposure to ambient air pollution and severe COVID-19.
However, they urge that more research is needed to fully understand the main biological pathways involved.
“One of the strengths of our analysis is the population representation,” said Cathryn Tonne, an ISGlobal researcher.
“Our study covers both urban and rural areas, and we were able to obtain detailed data on individual exposure to ambient air pollution in a country heavily affected by the pandemic in 2020.”
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The study was published in Nature Communications.
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