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From a human health standpoint, the COVID-19 pandemic has emerged as a major challenge. The alarming exponential increase in the disease's transmission and fatality rates has brought the entire world to a halt in order to deal with its dire consequences. As a result, lockdown has been imposed around the world to prevent the disease from spreading further. The ensuing lockdown had far-reaching social and economic consequences. However, it had some positive effects on the environment, particularly in the context of air quality, as evidenced by reductions in particulate matter (PM), NO2, and CO concentrations across the world's major cities, as reported by several research organizations. There was a 20–30% reduction in NO2 emissions in China, Italy, France, and Spain, and a 30% reduction in NO2 emissions in the United States. In comparison to the previous year, China's air quality improved by 11.4 percent. In Brazil, during partial lockdown, NO, NO2, and CO concentrations dropped dramatically compared to the five-year monthly average. PM10, PM2.5, SO2, NO2, CO, O3, and NH3 concentrations were reduced by about 12.33 percent in India, respectively. This article discusses the environmental impact of lockdown as well as the pre- and post-lockdown air pollution scenarios in major cities around the world. Several aspects of the environment, including air, water, noise pollution, and waste management, were thoroughly studied and evaluated during, before, and after the lockdown scenario. As a result, this study will serve as a guide for environmentalists, administrators, and frontline warriors in their quest to find a way to defeat this deadly disease while minimising its long-term health and environmental consequences.