Air pollutants, such as particulate matter and nitrogen oxides, are released into the air by – among other things – road traffic, agriculture and industry. These substances contribute to poorer air quality. They enter the body through inhalation, leading to various health effects, such as cardiovascular and respiratory diseases. Also, people exposed to air pollution may be more susceptible to respiratory infections. 

Study results: cleaner air can prevent infections and severe illness

We investigated the effect of particulate matter (PM10 and PM2.5) and nitrogen dioxide (NO2) on SARS-CoV-2 infection rates and the severity of the disease. The results below focus on the effect of long-term exposure to these pollutants in the three years before the pandemic. 

• Positive SARS-CoV-2 test results:
  Over 760,000 positive SARS-CoV-2 test results were recorded in Dutch test lanes between 1 June 2020 and 31 January 2021. Air pollution played a role in some of these infections. In the regions where the air quality was worse than average in the Netherlands, a total of 6,000 to 13,500 positive test results could have been prevented if the air had been as clean as average. 

• Hospital admissions:
  Between 1 February 2020 and 31 December 2020, over 31,000 people were hospitalised nationwide due to COVID-19. In the regions where the air quality was worse than average in the Netherlands, a total of around 1,100 hospital admissions could have been prevented if the air had been as clean as average. 

• Deaths:
  Between 1 February 2020 and 31 January 2021, nearly 22,500 people in the Netherlands died from COVID-19. In the regions where the air quality was worse than average in the Netherlands, a total of 400 to 800 deaths could have been prevented if the air had been as clean as average. 

We also investigated whether daily variation in air quality plays a role. Indeed, the quality of the air varies widely. The weather in particular plays an important role here. Temporarily higher or lower emissions also matter. When the air quality is temporarily worse, people are more likely to contract SARS-CoV-2. Also, more people end up in hospital or die. 

Specific relationship between air quality and COVID-19

It was already known that air pollution increases the risk of respiratory diseases and infections. This study shows that the effect of poor air quality is similar for COVID-19: poorer air quality can lead to respiratory diseases, and in this case COVID-19. 

Sources of particulate matter

Especially at the beginning of the COVID-19 pandemic, people in several regions had questions about the impact of air pollution on the number of people who became infected with SARS-CoV-2. For this reason,  RIVM studied the contributions of several major sources of particulate matter in the Netherlands, such as livestock farming, road traffic and industry. In addition, the composition of particulate matter and therefore its harmfulness differ per source.

The study shows that particulate matter emissions from livestock farming affect both the risk of infection and severity of the disease. The researchers also found that particulate matter emissions from road traffic have a greater effect on the severity of the disease, but less of an effect on the risk of infection with SARS-CoV-2. They found no specific influence on the risk of infection with SARS-CoV-2 or the severity of the disease for particulate matter emissions from industry.

Read the news item or the full report.