Tehran Times - Tehran air quality reached a level which was unhealthy for sensitive groups for about 7 days due to ozone pollutant; as the statistics show concentration of this pollutant increases in the capital mostly during summer, so, ground level ozone became the main contributor to pollution in the capital�s hot seasons.

Ozone in the lower atmosphere is formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides (NOX) that react to form ozone directly at the source of the pollution namely, cars, industry, gas vapors, chemical solvents, fuel combustion.

According to the statistics published by Air Quality Control Company, the concentration of other pollutants in Tehran has decreased in the last month of spring compared to the same period last year, however, during the last month, ozone reached up to a level which is unprecedented in the past 17 years.

In fact, polluted summer phenomenon has haunted the metropolis of Tehran since 3 years ago which has been compounded this year; last year Tehraners experienced 15 days of polluted air quality contaminated by ozone, thus, this was much less compared to the previous years.

Hossein Shahidzadeh, the caretaker for Air Quality Control Company told Khabaronline news agency that regarding the current situation, ozone pollution inevitably rises during summer this year.

Several reasons might be behind the emergence and intensification of such environmental issue over the past few years, he noted, adding, for one, ozone measurement devices have changed in recent years, so that is possible to notice ozone pollution due to the precision of measurements.

Heavy rainfall in spring has reduced the amount of particulate matter in the air, which also resulted in ozone emission raise, as sunlight intensifies in hot months, he added.

Based on the latest data published by National Drought Warning and Monitoring Center affiliated to Iran�s Meteorological Organization, since the current crop year (September 23, 2018), precipitation in the country increased to 310.2 millimeters from 159.2 millimeters in the previous water year, demonstrating a 94.9 percent rise. The amount also raised in comparison to the long-term average of 222.3 mm, amounting to 39.5 percent.

�Of course, this is not the only reason for the increase of ozone-infected days, there is also a second reason, which shows that human involvement is not negligible,� he further stated.

He also noted that ozone is a secondary pollutant, as it is produced when two primary pollutants react in sunlight and stagnant air, so, cars are not emitting ozone directly, but is produced by the reaction of certain gases produced by cars, motorcycles and diesel vehicles.

�All of these reasons together led to an unexpected increase of low level ozone in Tehran's air over the past few years, but some measures could come efficient to mitigate the pollution, which did not take place in the past few years.

Curbing ozone emission can come up with several solutions, one of which is the implementation of a scheme for vapor recovery through which a system was installed to separate organic vapors from air and off-gases in the stations, however, the scheme is developing at a low pace,� he explained.

Another way to improve the situation is clunker cars scrappage, which means discarding the old cars and motorcycles, he stated, highlighting that over 60 percent of motorcycles amounting to 1.5 million are extremely old which must be scrapped.

According to the Clean Air Act, car manufacturing companies are supposed to turn 10 percent of its production to electronic ones throughout the year, or remove clunker cars from operation, he added.

Not employing these solutions may make this situation more dangerous in the summer in near future, and summers turn into a new season for air pollution, he lamented.

How climate change affects ozone pollution?

The past three years were the hottest on record, as the UN World Meteorological Organization (WMO) wrote in its annual report on the global climate. 2016 was the warmest year in records dating back to the 19th century, with 2017 and 2015 tied for second place in a warming trend the WMO blames on man-made emissions of greenhouse gases.

According to data from the National Oceanic and Atmospheric Administration (NOAA), 2018 is on pace to be the fourth hottest year on record due to climate change.

Climate change has led Iran's temperature to raise over the past decades, an increase of 2 times the world's average; this rise in temperature in the summer can make the ozone pollutant more easily produced.

When temperature rises, wildfires will diminish the forests or oxygen producing areas and spew smoke into the air forming more smog, or ozone, on warmer days, which can cause million deaths if not prevented.

According to World Health Organization, 4.2 million deaths every year is the result of exposure to ambient (outdoor) air pollution and 91% of the world�s population lives in places where air quality exceeds WHO guideline limits.

Can clunker cars elimination curb ozone pollution?

Shahidzadeh also noted that due to an increased concern about the influence of ozone emissions on human health and on the capital�s air quality, notably clunker cars should be scrapped and diesel vehicles also have to be discarded.

This is while an Iranian automaker has undertaken a study on manufacturing diesel cars.

Diesel fuel contains slightly more carbon than petrol, however, it involves toxic emissions which threaten public health, during fuel combustion in an engine nitrogen is released and combines with oxygen atoms to create nitric oxide (NO), which is further combined with oxygen and create nitrogen dioxide (NO2), both are referred to together as NOx.

Navab Hosseini-Manesh, an official with Tehran Vehicle Inspection Company affiliated to Tehran Municipality said that currently, over 100,000 diesel vehicles are plying the capital�s roads which means that smoke amounting to 87 cubic kilometers is choking in the capital per day.

He further regretted that there are 4 million cars moving across the metropolis of Tehran contributing to numerous days of unhealthy air quality, warning that once pollutant diesel cars join the capital�s fleet the pollution will soar.

When solutions become effective?

All the solutions have ever been proposed whether by the officials or the experts might be effective to mitigate air pollution haunting the capital and imposing serious threats to the lives of thousands of residents, the certain solution is only strict implementation of the solutions and obliging the responsible devices to employ the rules and regulations.

Otherwise, none of the aforesaid solutions can make a slight change in the increase of pollutants.

So, it needs public cooperation along with serious enforcement to breath clean air.