Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 42 10 2013 10 15 1167 1173 Masoud Mehrpour 1. Dept. of Neurology, Iran University of Medical Sciences , Tehran, Iran. Narges Sadat Shams-Hosseini 2. Dept. of Occupational and Environmental Medicine, Center Research of Occupational Disease; Firoozgar Clinical Research Developmental Center, Tehran University of Medical Sciences , Tehran, Iran. Saeed Rezaali 3. Sina MS Research Center, Sina Hospital, Islamic Azad University, Tehran Medical Branch , Tehran, Iran. Mohammad Ali Sahraiian 4. Dept. of Neurology, Sina Hospital, Tehran University of Medical Sciences , Tehran, Iran. Sara Taki 5. Firoozgar Clinical Research Developmental Center, Iran University of Medical Sciences , Tehran, Iran. 2015 10 15 Multiple Sclerosis (MS) is one of the autoimmune diseases with an unknown cause. The aim of this study was to explore the link between air quality and MS relapses in patients who suffer from MS.This time-series study was conducted on patients registered at the Iranian Multiple Sclerosis Society in 2011-2012. They were randomly selected from patients lived in Tehran in the last five years, and had at least one relapse in the last three years. The link between monthly mean air pollutant levels and the relapses of MS in the participants was studied.Among the registered 160 participants, at least 150 had one attack during 2009 and 2012. Most air pollutants such as NO2, NO and CO are in high levels in the rainy season. Others like Pm10 and Nox are in high levels in the dry season. The correlation between NO2 levels of all markers of air quality and MS relapses (P=0.03, r=0.27) is weak. Best ARIMA model (p,d,q; 1,0,1) was determined between number of monthly relapses and living place, although this model was not significant (P=0.3) (AR; P=0.000, MA;P=0.4).Air pollutants might be regarded as a risk factor for MS relapse. https://ijph.tums.ac.ir/index.php/ijph/article/view/4381 https://ijph.tums.ac.ir/index.php/ijph/article/download/4381/4030