The effect of COVID-19 lockdown on air pollution matter in Iranian cities, especially Tehran: A systematic review.

Abstract

Background: Major cities in Iran have experienced significant air pollution problems. Air pollution in Iran is a complex issue with various contributing factors, including industrial activities, vehicular emissions, power plants, and dust storms. The Iranian government has recognized the severity of the air pollution problem and taken measures to address it. Traffic control plans and raising citizen awareness are among these measures. However, despite these efforts, challenges remain in combating air pollution. The COVID-19 pandemic had already caused significant impacts on air pollution levels around the world. These lockdowns reduced industrial, transportation, and human activities. It was an excellent opportunity to determine whether it could be effective to reduce air pollution or not.

Methods: To investigate the effectiveness of COVID-19 Lockdown on air pollution in Iran, a systematic review was conducted in January 2023. Inclusion criteria consisted of quantitative studies, from 2020, which assessed air pollution in different cities in Iran during COVID-19 Lockdown.

Results: Thirteen studies were finalized for analysis, with seven common outcome measures (AQI, NO2, CO, O3, SO2, PM 2.5, PM 10). NO2 and CO decreased in all studies as a direct result of vehicle transport, while AQI showed minimal differences. O3 and PM 2.5 levels increased in most conditions due to their formation processes. It was found that PM 10 decreased in most circumstances, but in varying degrees.

Conclusion: The COVID-19 Lockdown had positive effects on air pollution in most cities of Iran, but the effects were not as significant as expected due to partially applied Lockdown and to other sources of air pollution in Iran. However, the results suggest that an appropriate traffic control plan as a similar effect of COVID-19 Lockdown can help control traffic in large cities in Iran, especially in Tehran megacity, along with other factors including improving public transport, reducing fossil fuel usage, and using electrical vehicles.