en مديريت خدمات بهداشتي و درماني Management of health care services پژوهشي Original Article <p>Background and purpose: In this study, the air quality index and concentration of particles such as PM10 and PM2.5 were investigated in Arak. Materials and Methods: To determine the concentration of PM10 and PM2.5, 60 samples were collected by laser TSI model 8520 in summer and winter 2012. The collection site was around Arak city center. Results: during the sampling period, as a matter of PM10, the cleanest and the most polluted month were December and June with the average of 34.33 &micro;g m-3 and 100.1 &micro;g m-3, respectively. The concentration of PM2.5 was 12.93 and 53.17 &micro;g m-3 for December and June, respectively. Meanwhile, in terms of air quality index (AQI), in 98.3% and 70% of cases, the concentrations of PM10 and PM2.5, respectively were less than normal (AQI100). Conclusion: The concentration of PM10 in the study period was less than Environmental Protection Agency (EPA) 2006 guideline. Meanwhile, the concentrations of PM2.5 in 30% of air samples were greater than EPA guideline. The average PM2.5/PM10 ratio during the sampling period was 0.41 compared to range 0.15 to 0.25 reported by EPA.</p> Air, PM2.5/PM10, Particles, AQI, Iran 12 17 http://jhs.mazums.ac.ir/browse.php?a_code=A-10-343-10&slc_lang=en&sid=1 Fatemeh Fazelinia 10031947532846003865 10031947532846003865 No Arak University of Medical Sciences Ali Akbar Khodabandehlou 10031947532846003866 10031947532846003866 No Khoramabad University of Medical Sciences Lida Rafati 10031947532846003867 10031947532846003867 No Yazd University of Medical Sciences Amir Hossein Mahvi ahmahvi@yahoo.com 10031947532846003868 10031947532846003868 Yes School of Public Health, National Institute of Health Research, Center for Solid Waste Research, Tehran University of Medical Sciences