Tehran University of Medical Sciences Journal of Air Pollution and Health 2476-3071 5 3 2020 09 29 153 162 Masoumeh Rahmatinia Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran Anooshiravan Mohseni Bandpey Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran Abbas Shahsavani Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran AND Environmental and Occupational Hazards Control Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mostafa Hadei Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Ahmad Jonidi Jafari Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran Alireza Raeisi Department of Internal Medicine, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Vajeh Hasanzadeh Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran Alireza Zali Department of Neurosurgery, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran Maryam Yarahmadi Environmental and Occupational Health Center, Ministry of Health and Medical Education, Tehran, Iran Majid Kermani Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran Mehdi Amouei Torkmahalleh Chemical and Aerosol Research Team, School of Engineering, Nazarbayev University, Nur‐Sultan, Kazakhstan Zahra Namvar Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran Shahriyar Bazzazpour Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2020 11 29 2020 12 26 Introduction: The novel coronavirus disease 2019, namely COVID-19, has been known as a global pandemic by the World Health Organization (WHO). To prevent of COVID-19 spread, most countries including Iran have implemented many preventive measures. This study aimed to evaluate the effect of implementation /non- implementation of the traffic plan on confirmed cases, suspected cases, and mortality cases by COVID-19 as well as on air quality in Tehran. Materials and methods: Daily data of confirmed COVID-19 cases, suspected COVID-19 cases, mortality COVID-19 cases, air pollutants concentration and meteorological variables were obtained from 26 February, 2020 to 5August, 2020 in Tehran megacity and data were compared during the period’s implementation / non-implementation of traffic plan in Tehran. Results: Our results showed that the non-implementation of traffic plan has been effective in reducing the number of daily confirmed cases, suspected cases and mortality by COVID-19. Also, the average concentration of PM10, PM2.5, NO2, O3, SO2 and CO have reduced significantly during non-implementation traffic plan phase. Conclusion: Our findings indicate that there is a significant association between non-implementation traffic plan and reduce risk of COVID-19 infection. https://japh.tums.ac.ir/index.php/japh/article/view/261 https://japh.tums.ac.ir/index.php/japh/article/download/261/250