Title image source: Smart Air

The streets are empty, and pictures of clear blue skies above Delhi and Beijing have gone viral (no pun intended). It is obvious that the Coronavirus has been dramatically beneficial to air quality around the world. In fact, the Centre for Research on Energy and Clean Air (CREA) calculated that the various lockdowns due to Covid-19 have resulted in 11,000 fewer deaths from air pollution across Europe. But perhaps less obvious is the fact that the inverse is also true – poor air quality drastically increases the spread and severity of the Coronavirus. This is partially because air pollutants weaken hearts and lungs. However, more recently, it has become apparent that particles of air pollution may be aiding the spread of Coronavirus by carrying it further afield. 

Several studies have investigated how far the virus can travel, and what the risk of catching it is at different distances away from an infected person. Scientists think that the large droplets containing the virus from coughs and sneezes fall to the ground within two meters. This has informed the social distancing guidelines of staying 2m apart. However, some small particles may travel further and for longer. Scientists state that droplets from coughs and sneezes less than 5 µm in diameter could remain in the air for many minutes, even hours, and thus travel further. In addition, new studies are showing that small airborne particles of pollution, such as PM2.5 particulates (<2.5 µm in diameter), are transporting the virus on their surfaces. These scientists discovered Coronavirus attached to particles of air pollution in Bergamo in Italy and proposed that air pollution might be the reason that Coronavirus spread much faster in the more industrial north of Italy than in other parts of the country. (See the graph below, which indicates northern Italy’s high levels of PM 2.5) 

Source: European Environment Agency

It is widely believed that Influenza viruses, Respiratory Syncytial viruses and Measles viruses can spread by “hitching” lifts on pollution particles. Hence, the researchers hypothesized that this may be the case for the novel Coronavirus too. They looked at infection rates in the Po valley in China, which is more industrial than the surrounding areas and was hit harder by the Coronavirus. They also compared the infection levels to day-to-day levels of pollution, and found that, allowing for the delay from the virus’ incubation period, the rates of new infections correlated quite closely to changing pollution levels. While this is not accepted as sufficient proof by the scientific community, it is backed up by other studies. Airly’s data from Wuhan suggests that even a minor increase in particulate levels at the beginning of the pandemic is associated with a faster spread of Coronavirus.  

As well as increasing the rate of spread, poor air quality can also increase death rates. The European Public Health Alliance (EPHA) issued a warning that people who were already affected by air pollution would be in greater danger from the virus. They pointed to a 2003 study of SARS, which found that patients in moderately polluted areas were 84% more likely to die than those in less polluted regions. The same conclusion was reached by researchers at Harvard University’s T.H. Chan School of Public Health. Their study found that “long term exposure to just 1 µg/m3 more of PM2.5 was associated with an 8% increase in the Coronavirus death rate in a given city”.  

The reason that bad air quality increases the death rate from the Coronavirus is that, as well as pollution weakening hearts and lungs, the immune system appears to respond in similar ways to both the threats of air pollution and the virus. Both trigger cytokine-related inflammation, during which the immune system releases cytokine molecules to fight the threat in the lungs. This means that a patient is more likely to experience a “cytokine storm” that can attack healthy tissue, thus weakening the body further and often resulting in death.  

Overall, we can see that the Coronavirus is spread more easily where air quality is poor. It seems that there is a strange dynamic in play. As these two global crises, namely Coronavirus and Air Pollution are linked, would making changes to deal with one help to deal with the other? And finally, will we seize the opportunity to make these changes last? 

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