A Review of the Impacts of COVID-19 on Air Pollution in the World

Introduction: The COVID-19 epidemic has polluted millions of people and has caused millions of deaths worldwide. Therefore, this study aims to review the effects of COVID-19 on global air pollution. Materials and Methods: In this narrative review, articles related to the objectives of the study were selected in reliable scientific databases such as Web of Science, Ovid, Google Scholar, PubMed, and Scopus. A total of 294 browsing sources and ultimately 90 sources were selected. Results: In the COVID-19 pandemic, NO2 dropped from 53 to 11% in most countries, and PM2.5 and PM10 from 91 to 6% in some countries. CO dropped from 92 to 5% and SO2 had a decreasing trend from 77 to 7% in most countries, except for the largest cities in Britain, Poland, Taiwan, and Iran. Unlike other pollutants, O3 in most countries increased from 0.3 to 63%, but O3 decreased in some countries. Conclusion: In the lockdown period, the reduction of most air pollutants except O3 was observed in many countries. But after restarting, polluting activities have incresed again. Therefore, the rules implemented during lockdown time can be introduced as an appropriate option in emergencies to reduce air pollution.