Research increasingly shows just how much more infectious and dangerous coronaviruses are to those impacted by air pollution.

Research on air pollution and viruses goes back many years. 

In 2003, scientists found that people exposed to high air pollution levels were twice as likely to die from SARS, as those with less exposure – an 8.9% mortality rate for polluted areas versus 4.08% for less polluted areas.1

It's worth noting that the SARS-CoV-1 virus responsible for the 2003 SARS outbreak has been found to be 80% similar to the SARS-CoV-2 coronavirus responsible for the COVID-19 outbreak that began in late 2019. 

This suggests that research on coronaviruses and air pollution may already have a deep well of research to draw from. 

The mortality rate of people infected with the SARS coronavirus living in heavily polluted areas was about 8.9%, while those infected who lived in less polluted areas faced a mortality rate of 4.08%.

COVID-19 and air pollution

Researchers have since dug deeper into why air pollution may increase the risk of death from COVID-19 and other coronavirus infections.
A groundbreaking 2020 study looked at three cell receptors in the lungs that the virus uses as entryways into your lungs: the enzyme ACE2 and the proteins DC-SIGN and L-SIGN.2

These receptors keep your basic bodily functions working normally by turning amino acids and sugars into fuel for important processes as follows:

  • ACE2 helps regulate blood pressure
  • DC-SIGN and L-SIGN support immune system responses to disease.

Researchers compared how the lungs of smokers and non-smokers responded to COVID-19 infections. They found that ACE2 receptors in smokers’ lungs were more vulnerable to SARS-CoV-2 coronavirus infections than non-smokers.

ACE2 receptors in smokers’ lungs were more vulnerable to COVID-19 infections than non-smokers.

Lung damage in smokers is very similar to lung damage in people who have breathed air pollution for long periods of time.

A 2019 study in the Journal of the American Medical Association found that regular exposure to pollutants like ozone was like smoking a pack of cigarettes a day in terms of lung damage.3

Even areas with relatively low levels of long-term air pollution can be susceptible to higher risks of severe or deadly COVID-19 symptoms from poor air quality. 

A team of researchers from the Harvard T.H. Chan School of Public Health wanted to find out just how deep the relationship between air pollution and the coronavirus goes.4

So they looked at COVID-19 deaths and average particulate matter, or PM2.5 pollution in over 3,000 U.S. counties that represented 98% of the U.S. population. The researchers found that a PM2.5 increase of 1 microgram per cubic meter (𝜇g/m3) increased the risk of severe or deadly COVID-19 symptoms by 8%.

A PM2.5 increase of 1 microgram per cubic meter (𝜇g/m3) increased the risk of severe or deadly COVID-19 symptoms by 8%.

That may not sound like a big increase – but let’s put this number into perspective.

According to the World Health Organization (WHO), the highest “safe” concentration that air pollution should ever reach (including PM2.5) is 10 𝜇g/m3.5

Even if local air pollution levels go from 1 𝜇g/m3 in the morning to 11 𝜇g/m3 after morning and evening rush hour (still below the WHO “acceptable” threshold), your chances of a severe or deadly COVID-19 infection increase by up to 80%.

COVID-19 and PM2.5

Let’s look more closely at how the coronavirus interacts with PM2.5. PM2.5 pollution, made up of inhalable fine particles, is considered one of the most dangerous air pollutants

A group of researchers looked at nearly 25,000 COVID-19 cases across 72 cities in China and found a statistically significant link between increases of 10 𝜇g/m3 for PM2.5, even for a single day, and the amount of COVID-19 cases reported for the next two weeks.6

Researchers in China found a significant link between increases of 10 𝜇g/m3 in PM2.5 for a single day and the amount of COVID-19 cases reported for the next two weeks.

This study suggests that even temporary spikes in air pollution can increase the mortality rate for as long as two weeks after the spike.

Another study released by the World Bank in collaboration with Vrije Universiteit supported the notion that there’s a dangerous link between PM2.5 and COVID-19.7

Examining COVID-19 cases from over 355 cities in the Netherlands, the study noted that for every 20% rise in air pollution, COVID-19 cases could be expected to rise by nearly 100%.

For every 20% increase in PM2.5, COVID-19 cases can rise by nearly 100%.

According to the study, this huge increase was found even when not considering the previous health or the demographics (i.e., race, income) of those infected by the SARS-CoV-2 coronavirus.

This means that the relationship between PM2.5 and COVID-19 could be even more drastic than the study found when taking pre-existing conditions and other risk factors into account.

Using data from previous air pollution and coronavirus studies, a research team estimated that 15% of covid-19 deaths were a result of long-term air pollution exposure. The 2020 study, published in Cardiovascular Research, analyzed mortality from the 2003 SARS outbreak and early 2020 COVID-19 cases and found that increase in case severity and frequency was connected to ambient air pollution.8

Percentage estimates were even greater in several regions. 

  • North America - 17%
  • Europe - 19%
  • East Asia - 27%

In another study, Italian and Danish researchers also looked at the unequal impact of COVID-19 among various cities in Italy, showing the effect that air pollution could have on COVID-19 outcomes.9

To do so, the researchers compared air pollution and COVID-19 cases from cities throughout Italy using public data from Italian Civil Protection, Italy’s national emergency services.

Their analysis suggests that the COVID-19 death rate in Lombardy and Emilia Romagna, in northern Italy, was about 12%, compared to an average of 4% elsewhere in Italy.

Three times as many people died from COVID-19 in northern Italy, where air pollution levels are some of the highest in Europe, than in the rest of Italy.

Three times as many people died from COVID-19 in parts of northern Italy, where air pollution levels are some of the highest in Europe, than in the rest of Italy.10

These COVID-19 studies build on the clear link that past research has drawn between particle pollution and respiratory conditions that lead to worse outcomes from viral infections.

A 2013 study from the University of Montana found that exposure to PM2.5 in wildfire smoke can make it harder for your body to fight viral infections for up to a week after exposure.11

Exposure to PM2.5 from wildfire smoke can make it harder for your immune system to fight viral infections for up to a week.

This is because PM2.5 can stop immune cells called macrophages from being activated – cells that are on the front lines of infection control in your body.

A 2014 study in BMC Pulmonary Medicine found that simply having pollutant particles in the lungs could result in:12

  • viruses reproducing and spreading more quickly within the lungs and the body
  • white blood cells losing their ability to attack and destroy the virus 
  • viral material being cleared much more slowly from the lungs 

These studies reveal the unequal impact that COVID-19 can have on communities already suffering from poor air pollution.

The takeaway

Healthy people exposed even briefly to high concentrations of PM2.5 face a higher risk of severe or deadly infections caused by the SARS-CoV-2 coronavirus.

This means that communities exposed to long-term PM2.5 face risks far beyond that. The impact of air pollution can further widen the gap between the impact of COVID-19 within different communities. 

Throughout the world, much of the air pollution unequally affects poorer communities – further worsening the impact of COVID-19 in poorer communities.13,14,15