en Biostatistics Biostatistics پژوهشي Research <div><strong>Introduction: </strong>Air pollution is one of the prime public health concerns influencing infectious diseases. From May 13 to July 29, 2020(77 days), Tehran experienced unhealthy conditions caused by high levels of O₃ and PM2.5, whereas other pollutants remained at safe levels. This study, for the first time, sought to investigate the linkage between not only PM pollutants, but also O₃ and the number of daily confirmed new cases of COVID-19 in Tehran, Iran.<br> <strong>Materials and Methods: </strong>In this experimental study, the data on air pollution were obtained from an average of 23 air quality monitoring stations scattered in 20 districts of Tehran municipality during the 77days. Pearson&rsquo;s correlation and log-linear generalized additive model (GAM) were used to examine the association of the daily numbers of confirmed cases of COVID-19 and levels of O₃ and PM2.5. Also, effective degrees of freedom (edf) used to determine the structural relationship between independent and dependent variables. GAM was performed by R software (version 3.5.3) with the &ldquo;mgcv&rdquo; package (version 1.8-27).<br> <a name="_Hlk83282040"><strong>Results</strong></a><strong>: </strong>The results show a significant relationship betweenO₃, PM2.5, and COVID-19 (P <0.001), while other pollutants such as NO₂, PM10, CO, and SO₂ remain at healthy levels during the study period. Besides, O₃ and PM2.5 with edfs greater than 1 had significant nonlinear effects on the daily number of COVID-19 cases (P < 0.001). <span dir="RTL"></span><br> <a name="_Hlk85713844"><strong>Conclusion</strong></a><strong>: </strong>Considering the results of this study, there is a positive nonlinear association between O₃, PM2.5, and daily confirmed cases of COVID-19. These findings suggest that O₃ and PM2.5 levels should be considered as influential factors that can aggravate coronavirus infection.</div> COVID-19, Air pollution, GAM, Tehran 62 68 http://jbrms.medilam.ac.ir/browse.php?a_code=A-10-355-3&slc_lang=en&sid=1 Mehdi Omidi m.omidi@ilam.ac.ir 10031947532846004780 10031947532846004780 Yes Department of Mathematics‎, ‎Ilam University‎, ‎Ilam‎, ‎Iran Rahebeh Abedi Rahebeabedi2000@gmail.com 10031947532846004781 10031947532846004781 No Faculty of Geodesy and Geomatics Eng., K.N.Toosi University of Technology, Tehran, Iran Elham Sobati E.sobati@ilam.ac.ir 10031947532846004782 10031947532846004782 No Department of English Language, Faculty of Literature and Humanities, Ilam University, Ilam, Iran Ali Sohrabnejad asnsohrabi@gmail.com 10031947532846004783 10031947532846004783 No Department of Management Health Service, Iran University, Tehran, Iran