evaluation of 5 air criteria pollutants tehran, iran

aims: tehran’s uncontrolled expansion, which promoted housing, public utilities, industries and increase of vehicles caused the problem of air pollution. necessary information about air quality in different places and different times is the first step of combating the air pollution. the purpose of this study was to investigate the annual, monthly and hourly average of 5 criteria air pollutants (pm10, o3, no2, so2, co) of tehran city, iran. instrument & methods: the hourly concentrations of pm10, o3, no2, so2, co were obtained from 21 air quality-measuring stations of tehran city, iran, during april 2012 to march 2013. data were presented by descriptive statistics in the form of mean and standard deviation.    findings: co concentration was not changed during the period of study. nitrogen dioxide increased in spring and winter. sulfur dioxide was not changed in the first six months of the year but its concentration increased in winter. trend of changes of floating particles showed increasing the concentration of this pollutant in may 2012 and january 2013. ozone concentration increased in the warm seasons and decreased in the cold seasons. conclusion: pm10, o3, no2, so2 and co has high concentrations and cold periods of the year are more polluted than the warm periods in tehran city, iran.