Background: In recent years, Tehran has faced major problems with air pollution for many reasons, and this issue has become a critical point in most of the days. However, less attention has been paid to the indoor air pollutants in exercise centers and their possible health effects. In this research, it was tried to briefly describe the characteristics and chemical composition of the aerosols present in the exercise centers of Tehran. Methods: Sampling was carried out by a high volume sampler with a value of 1.5 m3/min. Fiberglass filters were used to sample aerosol particles. The samples were then studied by scanning electron micrograph (SEM) method. Results: The results showed that average concentration of aerosol particles in the indoor and outdoor sports halls was 125 and 162 μg/m3, respectively. Therefore, there was a minor difference in the aerosols concentration inside and outside the sports venues during the competition period and in the presence of athletes. Also, chemical composition and morphology of the aerosol particles showed that there was a minor difference between the atmospheric particles inside and outside the exercise centers. Major elements found in the PM2.5 aerosol were Si, O, C, Mg, Ca, Mn and K. In general, common major crustal elements found in the atmospheric particles over all the sites were Si, Al, and Fe. Conclusion: It seems that many citizens of the polluted cities exercise indoor because of causes other than outdoor air pollution such as lack of time or appropriate facilities. Thus, it is necessary for all students, athletes, people and other health workers involved in sports and exercise medicine to know briefly about indoor air pollutants and its possible health effects on athletes who exercise in these environments.
