Air pollution in some Iranian cities has reached alarming levels, according to Hossain Shahidzadeh, deputy director at the Air Quality Control Company (AQCC).

The Air Quality Index (AQI) indicates air pollution levels have reached 145. Index between 101 and 150 is considered unhealthy for sensitive groups. Particulate matter (PM) of more than 2.5 microns has the most adverse effects on air quality.

The three main sources of air pollution in Iran are motorcycle carburetors (a device that blends air and fuel for an internal combustion engine), diesel cars without filters and gasoline gas guzzlers.

Particulate matter can come in almost any shape or size, and can be solid particles or very tiny liquid droplets. Big particles can be between 2.5 and 10 micrometers (about 25 to 100 times thinner than a human hair). Small particles are smaller than 2.5 micrometers.

During the cold months, when temperature inversion takes place, air pollution is trapped closer to the ground blanketing the city, Shahidzadeh said ISNA reported.

An inversion can lead to pollution such as�smog�being trapped close to the ground, with possible adverse effects on health. It can also suppress�convection�by acting as a �cap.� If this cap is broken for any of several reasons, convection of moisture present can erupt into violent�thunderstorms. Temperature inversion is notorious for freezing rain�in cold climates.

Following a significant drop in Tehran�s air quality last Monday after torrential rains, the Education Ministry temporarily prohibited all physical activity in schools. �Any type of physical activity in schools is banned until the air quality index of Tehran decreases considerably,� said Masoud Saqafi, head of the information center and public relations office at the ministry.

A temperature inversion occurred in the capital after heavy rainfall in various parts of the country last week. Air pollution monitoring stations reported that air pollutant particles had increased to above the safety level particularly for susceptible groups.

�LEZ System
Eight tons of fine particulates (82%) are generated daily from Tehran�s torturous traffic. Carburetor motorcycles dominate the city and are a far cry from the Euro 2 and Euro 3 standards. At present, motorcycles, trucks and outdated vehicles are said to be the main reason for Tehran�s worsening air pollution.

Pointing to the Low Emission Zone system where� cars are categorized under four colors: blue, green, yellow and red, according to the vehicle emission standards, Shahidzadeh said once enforced it will have great impact in reducing exhaust emissions since only vehicles that conform to high emission standards will be allowed to enter the zones.

Additionally, if 10% of the old, clunker and high pollutant emission cars are removed from the streets, it will help reduce vehicular pollution by 48%, he said. Hence, instead of daily prevention of half the vehicles from plying the streets under the even-odd license plate system, phasing out 10% of the dilapidated vehicles will achieve the same outcome.

AQI between 0-50 is good and air quality is considered satisfactory; 51-100 is acceptable; 101-150 is unhealthy for sensitive groups; 151-200 is unhealthy where everyone may begin to experience health effects; 201-300 is very unhealthy and health warnings of emergency conditions are issued since the entire population is more likely to be affected, and at 300 plus, it is hazardous.

By Financial Tribune