TEHRAN – Tehran's air quality index (AQI) has been unhealthy for sensitive groups for four days during the fifth Iranian calendar month of Mordad (July 23-August 22), ISNA reported on Friday.

During the aforesaid period, Tehran has experienced healthy air quality for 27 days, while being unhealthy for sensitive groups for 4 days due to high rate of particulate matter smaller than 2.5 microns in diameter (PM 2.5), and increase in ozone gas index (O3), the report added.

PM 2.5 is produced mainly by cars and motorcycles. PM 2.5 is especially dangerous because it can get lodged in the lungs and cause long-term health problems like asthma and chronic lung disease. O3 is produced by cars, industry, gas vapors, chemical solvents, fuel combustion.

Ozone in the lower atmosphere is formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind.

However, Tehran's air pollutants were not limited to O3 and PM 2.5, the capital's residents experienced an unhealthy day last month due to high level of particulate matter less than 10 micrometers in diameter (PM 10).

According to Tehran's air quality control company, due to strong winds and dust rises, concentration of PM 10 has raised during the second month of summer.

Tehran's AQI within past 4 years

Moreover, Tehraners have experienced five days of unhealthy air in the second month of last summer (July 23, 2017- August 22, 2017).

Three days of unhealthy air hit the capital due to PM 2.5, in the month of Mordad two years ago, as well.

Furthermore, in the month of Mordad three years ago, PM 10 and PM 2.5 have put Tehran's air in unhealthy conditions for two days, which is increased by strong wind and dust rise.

On top of that, some 15 days of Mordad four years ago, Tehran's air has reached a level which was unhealthy for sensitive groups.

World Health Organization (WHO) asserts that Tehran is one of the most air polluted cities in the world. Tehran is ranked 12th among 26 megacities in terms of ambient PM10 levels. After Cairo, Tehran is the most polluted non-Asian megacity. In 2016, the annual ambient level of PM10 was estimated at 77 micrograms per cubic meter. This is almost four times the WHO’s recommended threshold of 20 micrograms per cubic meter.

FB/MQ/MG