en Epidemiology Epidemiology Original Research Original Research <p><strong>Background: </strong>Urban air pollutants may affect respiratory mortality. This study was conducted to investigate this effect in Ahvaz, one of the most polluted cities in the world.<br> <strong>Methods:</strong> The impact of 7 major air pollutants including O₃, PM₁₀, NO₂, CO, and SO₂ were evaluated on respiratory mortality in different gender and age groups using a quasi-Poisson, second degree polynomial constrained, distributed lag model, with single and cumulative lag structures adjusted by trend, seasonality, temperature, relative humidity, weekdays, and holiday. Data were analyzed using the dlnm package in R x64 3.2.5 software. Significance level was set at less than 0.05.<br> <strong>Results: </strong>In adjusted models, for each IQR increase of O₃ in the total population, the risk ratio (RR) for respiratory deaths in 0 to 14- day lags was, respectively, 1.009 (95% CI:1.001-1.016) and 1.009 (95% CI:1.002-1.017), and it was 1.021 (95% CI: 1.002-1.040) in cumulative 0 to 14- day lags. For PM₁₀, in the total population and in adjusted models after 0 to 14- day lags and in cumulative lags of 0 to 14 for an IQR increase in the mean concentration of PM₁₀, the RR for respiratory deaths increased significantly and was, respectively, 1.027 (95% CI:1.002-1.051), 1.029 (95% CI:1.006-1.052), and 1.065 (95% CI:1.005-1.128). NO₂ showed a significant association with respiratory deaths only in the 18 to 60 year- old age group and in 9- day lags (RR= 1.318, 95% CI:1.002-1.733). Finally, the results showed that for an IQR increase in the mean concentration of CO and SO₂, the adjusted RR for respiratory deaths in 9- day lags in the total population was, respectively, RR= 1.058 (95% CI:1.008-1.111) and 1.126 (95% CI:1.034-1.220).&nbsp;&nbsp;<br> <strong>Conclusion: </strong>Air pollution in Ahvaz is probably causing increased respiratory mortality.<br> &nbsp;<br> &nbsp;</p> Short-term effects, Air pollution, Respiratory mortality, Ahvaz 173 181 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-922-8&slc_lang=en&sid=1 Maryam Dastoorpoor mdastoorpour@yahoo.com 200319475328460037497 200319475328460037497 No Neurology Research Center, Kerman University of Medical Sciences, Kerman, Iran. Narges Khanjani nkhanjani@kmu.ac.ir 200319475328460037498 200319475328460037498 No Environmental Health Engineering Research Center, Kerman University of Medical Sciences, Kerman, Iran. Abbas Bahrampour 200319475328460037499 200319475328460037499 No Physiology Research Center, Kerman University of Medical Sciences, Kerman, Iran. Gholamreza Goudarzi gh.goodarzi@ajums.ac.ir 200319475328460037500 200319475328460037500 No Air Pollution and Respiratory Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran & Environmental Technologies Research Center (ETRC), Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran. Hamidreza Aghababaeian hamidrezaaghababaeian@yahoo.com 200319475328460037501 200319475328460037501 No Nursing and Emergency Department, Dezful University of Medical Sciences, Dezful, Iran. Esmaeil Idani esmaileidani@gmail.com 200319475328460037502 200319475328460037502 Yes Air Pollution and Respiratory Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.