The global death toll from COVID-19 has now passed half a million. To slow the spread of the disease, we need to better understand why some places have higher numbers of cases and deaths than others.
One factor that could partially explain this is air pollution. Research has shown that long term exposure to pollutants such as fine particulate matter (often called PM2.5, as these are particles smaller than 2.5 micrometres), nitrogen dioxide (NO₂) and sulphur dioxide (SO₂) can reduce lung function and cause respiratory illness. These pollutants have also been shown to cause a persistent inflammatory response even in the relatively young and to increase the risk of infection by viruses that target the respiratory tract.
The pathogen that causes COVID-19 – SARS-CoV-2 – is one such virus. Several studies have already suggested that poor air quality can leave people at greater risk of contracting the virus, and at greater risk of serious illness and death. A study of the US found that even a small increase in PM2.5 concentrations of 1 microgram per cubic metre is associated with an 8% increase in the COVID-19 death rate. Our new research looked at the relationship between COVID-19 cases and exposure to air pollution in the Netherlands and found that the equivalent figure for that country could be up to 16.6%.