Air pollution linked with more severe COVID-19: Study

Common air pollutants, such as small particulate matter and ground-level ozone, are associated with more severe outcomes after COVID-19 infection, including admission to the intensive care unit (ICU), according to a study.

The research, published on Tuesday in the Canadian Medical Association Journal, analysed data on 151,105 people aged 20 years and older with confirmed SARS-CoV-2 infection in 2020 in Ontario, Canada, not living in a long-term care facility.

The researchers modelled historical exposure to three common air pollutants before the pandemic -- fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ground-level ozone (O3).

They adjusted for date of diagnosis, sex and age, being part of an outbreak, essential worker status, neighbourhood socioeconomic status, health care access including previous influenza vaccination history, previous outpatient visits and other factors.

The study identified 8,630, 1,912 and 2,137 COVID-19-related hospital admissions, ICU admissions and deaths, respectively.

The median times between first diagnosis and hospital admission, ICU admission and death were 5 days, 8 days and 15 days, respectively, the researchers said.

"We observed that people with SARS-CoV-2 infection who lived in areas of Ontario with higher levels of common air pollutants were at elevated risk of being admitted to the ICU after we adjusted for individual and contextual confounding factors, even when the air pollution level was relatively low," said Hong Chen from Health Canada, the department of the Government of Canada.

The researchers also found an elevated risk of hospitalisation with chronic exposure to PM2.5 and O3, and an increased risk of death from COVID-19 with chronic exposure to O3.

These results add to the growing reports linking air pollution to COVID-19 severity from other countries, including Spain and Mexico, they said.

"Given the ongoing pandemic, our findings that underscore the link between chronic exposure to air pollution and more severe COVID-19 could have important implications for public health and health systems," the authors of the study noted.

They call for more research to find the mechanisms of how long-term exposure to air pollution may be influencing severity of COVID-19.