Did COVID-19 quarantine help resolve our global air pollution crisis?

Updated: Aug 1, 2020

After COVID-19 spread across the countless nations, billions of people were instructed to quarantine to prevent further spread of the virus. Companies shut down operation, workers were sent home to their families, the streets emptied, and cities turned to quiet ghost towns. People wonder if the lack of human activity could have improved environmental conditions. People want to hear that some good came out of the extended time in isolation with a crippling economy and many concerns to return upon them after the quarantine is lifted. Film has shown simulated many story lines exploring what would happen if humans suddenly stopped performing the day to day activities that we do on a regular basis. We have learned that many human activities contribute negative effects on the environment from the transportation infrastructure and industrial energy use to agriculture. In this article we will explore how researchers have worked to examine the question:

Did COVID-19 quarantine help resolve our global air pollution crisis?

A march study analyzed data from cities in China impacted by COVID-19 that executed social distancing and quarantine procedures from January to March. This study analyzed the concentration of the six key pollutants that affect air quality from the World Air Quality index Project. The study selected data points over the past two years in eleven cities in China that did not declare states of emergency until March. The data was compared to the change in the same data points from Wuhan and six other cities in China that declared state of emergencies by the end of February.

An analysis of the six key pollutants: PM2.5, PM10, NO2, SO2, O3, CO determined [1]:

  • In Wuhan-PM2.5, PM10 and NO2 all showed significant declines in January and February and the reductions in the pollutants increased the number of days where pollutant concentrations were categorized as ‘good’ or ‘moderate’.

  • The three other pollutants: SO2, O3 and CO, did not show significant changes; the levels have already reduced significantly over time before the COVID-19 state of emergency

  • All air pollutants except O3 show a decline in the 2020 values for the early impacted cities that went into states of emergencies earlier in the study window of time.

  • For later impacted cities, there is no overall trend in changes in the concentrations of pollutants between 2020 and 2019

The declining air pollution trends provide evidence that China’s recent non COVID-19 pollution reduction and prevention efforts are making a significant impact on improving air quality, but the cities that practice extended government-enforced restrictions further reduced pollution levels. This study raises further questions whether the trend is being observed in other countries across the globe.

A comprehensive analysis of Air Quality Index (AQI) values and pollutant data points were executed in March at Aligarh Muslim University and the results determined [2]:

  • Countries affected with COVID-19 under government-enforced restrictions show moderate to significant lowering of air pollution in most parts of the world including China, Italy, and California as well as a reduction in greenhouse gas emissions.

  • Italy observed a significant reduction in NO2 pollution.

  • Lombardy reduced PM10 levels significantly after 10 days of COVID-19 social distancing initiatives

  • France observed a reduction in NOx (Nitrogen oxide pollutant).

  • New York observed a 5-10% decline in CO2 and a significant reduction in methane.

  • In certain areas across the US, a reduction in NO2 was observed.

  • India reported a decline in air pollution in the end of second week of COVID-19 lockdown;, a 91 cities were under ‘Good’ & ‘Satisfactory’ category, 31 cities with ‘Good’ AQI values, and no city was under ‘Poor’ AQI category, as on March 29, 2020.

  • A 30% drop in PM2.5 in Delhi was observed and by 15% in Ahmedabad and Pune.

  • In Delhi, the level of PM2.5 dropped (on 20 March 2020) significantly in just a couple days of the lockdown and a significant reduction in (PM10) and (NOx).

  • Between the 22nd and 23th of March 2020, a 44 percent reduction in PM10 was observed in New Delhi

This global data provided concludes that pollutants were significantly reduced worldwide due to quarantine and social distancing regulations that were enforced during the COVID-19 outbreak. However, another study questioned the affect that the reduced pollution would have on severe pollution events observed from China due to meteorological conditions.

“Most transportation was prohibited and almost all avoidable outdoor human activities stopped all around the country. However, severe air pollution episodes still occurred in the North China Plain (NCP). It is of great concern for people who are limited to use mobile vehicles on heavy pollution days why severe air pollution events were not avoided when no one was on road.” (Wang, P., et. al, 2020)

The study simulated the air pollution emission and meteorological observations from January 1st to February 12th. Before meteorological factors were integrated, sources of pollution were analyzed, and trends were observed. When transportation and industry emissions decreased, residential emission increased, and agriculture and power remained the same. Analyst predicted and observed emission changes under meteorological events then compared the data. The changes due to emission changes were calculated as well as changes due to meteorology assuming that meteorology is the reason for severe pollution when emissions are not changing day by day. The data determined that reducing pollution over this period is not enough to avoid severe air pollution events in most areas over the course of the period .This study highlights the importance of understanding the role of chemistry and meteorology in designing methods to mediate and prevent severe pollution events.

With this evaluation, we can come to terms that decreasing human activity has significantly reduced outdoor pollution which does not account for a solution that mitigates all severe air pollution events. What we now need to consider is the indoor air quality due to increase indoor activity. A March 2020 study analyzed the effects on indoor air quality risks with the health authority recommended quarantines due to COVID-19. Data shows a concern with the increased human activities indoors, such as cooking due to the closure of dine in restaurants, resulting in a decrease in the quality of indoor air. Public advisory messages should include practices for indoor air quality management while social distancing such as opening windows for ventilation and purifying indoor air to disrupt the continuing global health risks due to air pollution including increased risks for respiratory disorders and infections during a pandemic currently attacking the respiratory system. The study reported:

“This communication is especially important for the elderly and immunocompromised, and residents of cold regions and rural areas where the wood stove is the primary source of cooking and heating.” (Afshari, 2020).

Research and data confirm that quarantine practices did significantly improve global outdoor pollutant emissions however did not significantly reduce severe air pollution events due to meteorological conditions. During the quarantine we now need to make a shift to mitigating indoor air pollution so we can continue to implement safe social distancing practices.


1. Cadotte, M. (2020, March 30). Early evidence that COVID-19 government policies reduce urban air pollution. https://doi.org/10.31223/osf.io/nhgj3

2. Anjum, N.A. (2020). Good in The Worst: COVID-19 Restrictions and Ease in Global Air Pollution. Preprints 2020, 2020040069 (doi: 10.20944/preprints202004.0069.v1).

3. Wang, P., Chen, K., Zhu, S., Wang, P., Zhang, H. (2020). Severe air pollution events not avoided by reduced anthropogenic activities during COVID-19 outbreak. Sourced from https://www.sciencedirect.com/science/article/pii/S092134492030135X

4. Afshari, R. (2020). Indoor Air Quality and Severity of COVID-19: Where Communicable and Non-communicable Preventive Measures Meet. Asia Pacific Journal of Medical Toxicology, 9(1), 1-2. doi: 10.22038/apjmt.2020.15312


Pixnio. (2019). Smoke, technology, toxic, air pollution, climate, factory. [Photograph]. https://pixnio.com/miscellaneous/smoke-technology-toxic-air-pollution-climate-factory

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