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EghtesadOnline: Concentration of bad ozone as a known secondary air pollutant is gradually reaching critical levels in Tehran, director of Tehran's Air Quality Control Company was quoted as saying.

"Bad ozone, aka ground level ozone, concentration has been recorded at unhealthy levels for all groups, especially those suffering from respiratory problems," Hossein Shahidzadeh told ISNA Wednesday.

Ozone is a natural gas with a strong odor. Environmental scientists have classified the gas into good and bad. 

Elaborating on ground level ozone, Shaidzadeh noted that bad ozone does not exist naturally. Human action causes chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC), according to Financial Tribune.

He maintained that motor vehicle exhausts, gasoline vapors in and around gas stations and chemical solvents are among the major sources of NOx and VOC.

Bad ozone contaminates the air and contributes to what is typically known as "smog" or haze.

Referring to measures to fight this type of pollution, he stressed that at the outset toxic gasoline vapor at filling stations must be collected.

"Diesel engines in buses and trucks as well as carburetor-equipped motorcycles are known producers of toxic emissions that cause ground level ozone," Shahidzadeh said. 

This type of contaminant has turned into a serious issue in mega cities like Tehran because of which measures are necessary to prevent it from aggravating Tehran's poor air quality problem, he was quoted as saying. 

Air pollution in Tehran often reaches unhealthy levels in winter due to inversion, but in the hot summers ozone and dust particles are to be blamed for high levels of pollution. 

Further information on the sources of NOx and VOC is available in Tehran's first emission inventory report (2015), provided by researchers at the Fuel, Combustion and Emission group at Sharif University of Technology in collaboration with AQCC experts.


Iran Tehran Bad Ozone Critical Level secondary air pollutant