The Iranian capital’s residents inhaled less polluted air in October compared with the same period of last year, data from Tehran Municipality show.
Charts regularly published by Tehran Air Quality Control Company’s website, Airnow.tehran.ir, indicate that the “good” quality status was not recorded even for a day and has become a thing of the past.
Mostly “moderate” status dominated the month, keeping Air Quality Index between 51 and 100 for 26 days. Oct. 31 is also forecast by TAQCC to have a moderate air quality.
AQI categorizes conditions dictated by a measure of polluting matters into good (0-50), moderate (51-100), unhealthy for sensitive groups (101-150), unhealthy (151-200), very unhealthy (201-300) and hazardous (301-500).
Carbon monoxide, nitrogen dioxide, sulfur dioxide, ground-level ozone, PM2.5 and PM10 are measured to determine air quality. AQI figures are calculated as per the concentration of pollutants.
According to the data, air quality was unhealthy for the sensitive group for the remaining four days of October, with the AQI hovering between 101 and 150.
This vulnerable group of people, including the elderly, cardiovascular and respiratory patients, pregnant women and children, was advised to limit their outdoor activities and stay home.
Analyses illustrate that the pollutant responsible for the toxic index recorded in the four polluted days was PM2.5—particulate matters smaller than 2.5 micrometers.
The AQI review during the previous month shows air quality in Tehran is improving, at least in the short run.
In September, pollutants pushed AQI to the “unhealthy” threshold for the sensitive group on six days and the remaining 24 days passed with the index remaining in the “moderate” range.
With the dilution of ground-level ozone, becoming a usual phenomenon in Tehran’s hot season, the main culprits for the September’s polluted days were PM2.5 and PM10.
Annual Overview
The AQI review in the month over the past few years shows air quality in Tehran has gotten worse.
In October of last year, Air Quality Index was unhealthy for the sensitive group on 14 days, hovering between 101 and 150.
In the 17 remaining days, the index remained in moderate state. Analyses illustrate that the pollutant responsible for the toxic index recorded in the 14 polluted days was PM2.5.
In October 2019, "moderate" status was recorded on all 31 days. A year earlier, the rarely-seen good air quality was recorded on three days of October. The remaining 28 days were moderate.
Health Risks and Culprits
Poor air quality has long troubled all residents of Iranian cities.
In the capital city, the mortality figure has surpassed the shocking 5,000 a year, while the road traffic accidents take the lives of around 500 in Tehran, Traffic Police Chief for Roads Brigadier General Mohammad Hossein Hamidi said.
While there are various debates on the causes of poor air quality in the metropolis, the head of TAQCC earlier blamed 100,000 dilapidated passenger cars in Tehran.
Hossein Shahidzadeh added that over 3.43 million passenger cars ply the capital’s streets every day, 100,000 of which are over 18 years old and have outlived their usefulness.
He noted that these old cars emit 579,000 tons of toxins into the air annually, which means 1,586 tons per day.
Elaborating further, Shahidzadeh said of all the pollutants spewed into Tehran’s air annually, these dilapidated cars are responsible for 82% of sulfur oxide, 23% of PM2.5 and PM 10, 46% of carbon monoxide and 45% of nitrogen monoxide.
He also said PM2.5 is the most harmful pollutant due to its ability to penetrate deep into the lungs and bloodstreams unfiltered, causing heart attacks, respiratory disease and premature death.
Shahidzadeh called the officials in charge to more seriously monitor the technical efficiency of cars plying Tehran’s streets. He also warned urban managers on the danger of canceling traffic rules for any reason.
However, comparisons have shown that the implementation of traffic schemes has not had much effect on curbing air pollution in the city.
With the outbreak of Covid-19 in the country, municipal bodies in Tehran lifted traffic restrictions in late March and early August, to discourage people from using public transportation to curb the spread of the virus. But the measure led to clogged roads and heavy traffic in the city.
According to Mohammad Rastegari, the head of the Department of Environment, in both rounds, the resumption of traffic schemes in the capital has had close to zero effect on air pollution.
“Air quality data recorded daily by TAQCC show no decline in air pollution levels even after the resumption of traffic restrictions in the city,” he said.
Pointing to the decisive effect of environmental phenomena, such as wind, on air quality, the DOE official said wind can be much more effective than the most stringent traffic schemes, for it can disperse pollution and change air stability within a few hours.
This is why, Rastegari said, traffic schemes alone cannot reduce air pollution levels and can only cause minor alterations.
