COVID-19 Pandemic as an Environmental Health Indicator: Lessons Learned from Air Pollution Changes and Climate Implications

The most crucial environmental issue threatening public health is air pollution, which is strongly associated with respiratory, cardiovascular, and infectious diseases. Increased concentrations of air pollutants, particularly from industrial activities, fossil fuel combustion, and transportation, have become a major global concern. Fine particulate matter emitted from diesel vehicles, biomass burning, and coal combustion has been identified as one of the most important contributors to adverse health outcomes. Previous studies have demonstrated that meteorological conditions and air pollutant concentrations may influence the transmission dynamics and severity of respiratory viral infections, including COVID-19. The COVID-19 pandemic provided a unique global-scale environmental experiment by temporarily reducing anthropogenic activities, including transportation and industrial processes, through lockdown measures. These restrictions resulted in short-term improvements in outdoor air quality and reductions in greenhouse gas emissions in many regions. However, these temporary improvements also highlighted the need for long-term structural strategies rather than short-term reductions in human activities to mitigate climate change. In this critical narrative review, peer-reviewed original research and review articles, with particular emphasis on studies published during and following the COVID-19 period, were critically evaluated to examine the interactions among air pollution, climatological parameters, and COVID-19 transmission, as well as the effects of COVID-19-related lockdown measures on outdoor air quality. Furthermore, the implications of the pandemic for climate change mitigation and future environmental health preparedness are discussed, with particular attention to healthcare capacity, technological and surveillance infrastructure, public education, and integrated environmental and public health monitoring. Methodological limitations related to spatial mismatch between environmental exposure and epidemiological data, as well as delayed and nonlinear exposure–response relationships, are also critically considered. Overall, the evidence highlights the need to translate the temporary environmental improvements observed during the pandemic into long-term strategies integrating environmental monitoring, public health preparedness, technological capacity, and climate action.