Tehran University of Medical Sciences Journal of Air Pollution and Health 2476-3071 1 1 2015 11 13 1 6 EN Majid Kermani Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran Hossein Arfaeinia Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran Ramin Nabizadeh Center for Air Pollution Research (CAPR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran Mahmoud Alimohammadi Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AliAsghar Aalamolhoda Institute of Water and Energy, Sharif University of Technology, Tehran, Iran 2015 11 10 2015 11 10 Introduction: A broad spectrum of adverse health endpoint has been reported because of short- and long-term exposure to particles. Furthermore, various studies which have been indicated correlation between health effects and par- ticle matter characterization such as chemical composition and heavy metals. Materials and methods: PM 2.5 samples were collected in the ambient air of Sina hospital in Tehran, Iran, during the springtime 2013. The concentra-tions of target heavy metals (Pb, Cd, Cr, Ni, Hg, As and Zn) in PM 2.5 particles were quantified. The PM 2.5 levels were determined by gravimetric analysis and sample analysis for their heavy metals was done by ICP-AES (Arcous model, Germany) after total digestion. Results : The results showed that PM2.5 levels with an average of 41.19 μg/m3 were higher than outdoor PM2.5 standard of 35 μg/m3 recommended by USEPA. Total target heavy metals accounted for 0.3 % of PM 2.5 by mass. The mean values in 31 PM 2.5 particles samples also were found to be: Pb: 38.05 ng/m3, Cd: 18.2 ng/m3, Cr:4.24 ng/m3, Ni:4.19 ng/m3 , Hg: Not detection, As:1.34 ng/m3 and Zn:69:92 ng/m3. Correlations between PM 2.5 concentrations and toxic elements in various days of the week including: holidays, 1 day after holidays, and the other days have been extracted. Conclusions: This work describes the levels of PM2.5 and their heavy metals. The average concentration of PM2.5 were higher than PM2.5 standard that recommended by USEPA. The mean concentrations of PM 2.5 and heavy metals in 1 day after holidays were found higher in comparison with other two groups.  https://japh.tums.ac.ir/index.php/japh/article/view/3 https://japh.tums.ac.ir/index.php/japh/article/download/3/17