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The purpose of this study is to investigate the effect of air pollutants and noise on the prevalence of childhood asthma in Tehran, Iran. The standardized questionnaire was completed by one of the parents of children aged 6-7 years or by adolescents aged 13-14 years. The asthma prevalence in ages 6-7 and 13-14 was found to be 8.8% and 17.44%, respectively. A significant positive association was observed between "ever wheezing" and monoxide carbon (CO) concentration (OR=1.84, 1.05-3.25 in 13-14 years), the occurrence of 4 to 12 wheezing attacks and sulfur dioxide (SO2) concentration (Odds Ratio (OR)=1.39, 1.04-1.91) and particulate matter less than 2.5 micron (PM2.5) concentration (OR=1.38, 1.05-1.98 and OR=1.13, 0.98-1.39 in 6-7 and 13-14 years, respectively), as well as one night per week of sleep disturbances and nitrogen dioxide (NO2) concentration (OR=1.09, 1.03-1.16 in 6-7 years, respectively). It was also found that there was a significant interaction between the noise level and particulate matter less than 10 micron (PM10) level. Based on the findings, exposure to certain outdoor air pollutants and noise can affect prevalence of asthma symptoms in residence of Tehran. The simultaneous presence of air pollutants and noise has an aggravating effect on the prevalence of asthma symptoms. Therefore, controlling sources of pollutants for reducing asthma symptoms is suggested.