A. TL;DR. The relationship between COVID-19 and air pollution likely goes in both directions.
First, air pollution is linked with higher COVID-19 mortality risk. Second, the lockdowns associated with the pandemic initially resulted in a large reduction in air pollution in some regions, with more modest and temporary reductions in other regions.
The Nerdy Girls love a question that allows us to talk about bidirectionality! The relationship between COVID-19 and air pollution likely goes in both directions: 1.) Air pollution may increase COVID-19 mortality, and 2.) the quarantine or lockdown policies around COVID-19 temporarily reduced air pollution in some regions. Let’s dig in.
1.) AIR POLLUTION IS LINKED WITH HIGHER COVID-19 MORTALITY RISK
Air pollution has long been linked with increased health risks, and COVID-19 is no exception. For example, one study of 3089 counties found that those with higher particulate matter (PM2.5 – fine particles with diameter ≤2.5µm) have higher COVID-19 mortality rates (each 1 microgram per cubic meter increase in exposure is associated with an 11% increase in COVID-19 death rate for that county). Another study of 66 administrative regions in Italy, Spain, Germany, and France found that long-term exposure to NO2 (nitrogen dioxide) is positively associated with higher COVID-19 mortality rates. Nearly 80% of COVID-19 deaths occurred in the regions with top 5 highest concentrations of tropospheric NO2. These are ecological studies that don’t allow for adjustment by individual characteristics, but they suggest that air pollution plays in a role in COVID-19 infection and mortality.
2.) LOCKDOWN POLICIES AND LOWER MOBILITY DURING THE PANDEMIC REDUCE AIR POLLUTION
Lower levels of mobility during the pandemic reduced pollution in many but not all parts of the world. For example, urban areas in both China and India showed substantial declines in particulate matter leading to some of the cleanest air ever recorded. Other big cities such as Los Angeles, London, and Madrid, also saw drops in air pollution during lockdown. However, one study from the US did not show large changes in PM2.5, and changes in ozone, NO2, CO, and PM10 had only modest and temporary reductions. While the effects of the lockdowns on air pollution were geographically inconsistent, they provide a hopeful reminder of the power of the people to change their behaviors and make the air we breathe at least a little bit cleaner.