title: Long-term trends of Nitrogen oxides and surface ozone concentrations in Tehran city, 2002-2011.
abstract: OBJECTIVE
  Tropospheric ozone is a problem with multi aspects - hazard to human health, plant, and welfare and a key factor to climate change, air pollution and atmosphere chemistry, as well. Behavior of ozone and nitrogen oxides (NO, and NO2) concentration is highly complex and variable; therefore, their trends as short and long-term were significantly attended. Most of the studies were carried out on the behavior of pollutant concentrations in North America, Europe, and East Asia, but few studies have been conducted in west Asia. The aim of this study was to assess daily changes and long-term trend of ozone and nitrogen oxides concentrations in Tehran city, Iran from March 2002 to September 2011.
  
  
  METHODS
  Data were collected from 18 air quality monitoring stations. The data were sorted as daily mean of 10 years (daily changes) and annual mean for each year (long-term trend). One-sample test was used to assess the statistical significance.
  
  
  RESULTS
  Current findings indicated that changes of ozone, NO, and NO2 concentrations are dependent from job shifts and photochemical reactions. Annual mean concentrations of ozone and NO2 were gradually increased, long-term trend of ozone and NO2 concentration indicated. The correlation between long term trend of ozone and NO2 was significant (p < 0.05).
  
  
  CONCLUSIONS
  The controlling program was the most important factor in long-term concentration of ozone, and nitrogen oxides, but some problems and difficulties were accounted to perform controlling program.
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Motesaddi Zarandi
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mahmood
authors.initials: M
authors.lastname: Alimohammadi
authors.affiliation: Student Research Committee, Sabzevar University of Medical Sciences, Sabzevar, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Kazemi Moghaddam
authors.affiliation: Department of Environmental Health Engineering, School of Public Health and Air Pollution Research Center, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Sadegh
authors.initials: MS
authors.lastname: Hasanvand
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Mohammad Bagher
authors.initials: MB
authors.lastname: Miranzadeh
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Davarkhah
authors.initials: D
authors.lastname: Rabbani
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Gholam Reza
authors.initials: GR
authors.lastname: Mostafaii
authors.affiliation: Social Determinants in Health Promotion Research Center, Hormozgan University of Medical Sciences, Bandar Abbas, Iran.
authors.forename: Vali
authors.initials: V
authors.lastname: Sarsangi
authors.affiliation: Student Research Committee, Jiroft university of medical science, Jiroft, Iran.
authors.forename: Sajjad
authors.initials: S
authors.lastname: Hajiketabi
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Ashraf
authors.initials: A
authors.lastname: Mazaheri Tehrani
keywords: Daily changes; Long-term trends; Nitrogen oxides; Tropospheric ozone