Where Does Tehran's Air Pollution Come From?

Tehran's emission inventory shows that other sources, including agriculture, industries and power plants, also contribute significantly to particulate matter, the main air pollutant in Tehran, during the cold days of the year.

According to Ambassador Arjan, with the return of air pollution to Tehran in the cold days of the year, attention has once again been drawn to the sources of pollutant emissions; Sources that although cars and vehicles still have a significant contribution to the air pollution of the capital city, Tehran's emission list shows that the contribution of other sources such as agriculture, industries and power plants is also significant in the emission of suspended particles as the main pollutant of Tehran's air on cold days of the year.

Ambassador Arjan wrote: The list of emissions is one of the scientific tools for identifying polluting sources and determining the contribution of each to air pollution; A tool that can be the basis for decision-making and developing executive plans to reduce pollution. With the help of these studies, it is possible to determine which sources contribute the most to the emission of pollutants and which areas should be focused on for control measures?

According to the latest emission list of Tehran published in 1404 and its data is related to 1401, mobile sources account for about 46% of the emission of suspended particles. After that, agriculture sector with 21% share, industries with 18% and power plants with 14%. The share of the residential sector in this estimate is 1% and the share of the commercial sector is 0%.

Of course, it is not possible to directly compare these results with the publication list of 2016, because in the new study, in addition to updating the data and calculation method, new sources and steps have also been added to the investigations. In the previous list, the share of cars from gaseous pollutants was estimated at 83% and from suspended particles at 61%; Figures that cannot be directly compared with the new results due to the difference in the scope and method of the studies.

Fatemeh Karimi - Managing Director of Tehran Air Quality Control Company - referring to the process of preparing a new publication list, has explained that the data of this study is from 1401, but it was completed and published in 1404.

According to him, compared to the list of 2016, the methodology, input data and review procedures have been improved, and some sources have been considered for the first time in the new study.

One of the significant points in the new list is the investigation of the contribution of agriculture in the emission of suspended particles. This sector with a share of 21% is placed after mobile sources and it shows that the investigation of air pollution in Tehran should not be limited only to the sources inside the city. The use of chemical fertilizers and the release of ammonia in agricultural lands and even urban green spaces can contribute to the formation of pollutants. Also, agricultural activities in areas such as Shahryar, Shahreri, Islamshahr and Varamin, depending on the weather conditions and wind direction, can affect the air quality in Tehran.

In this study, the scope of investigation of emission sources up to a radius of 50 kilometers from the center of Tehran has been considered. Also, for the first time, some precursors of suspended particles, including volatile organic compounds, nitrogen oxides, and ammonia, have been considered; Substances that can play a role in the chemical reactions of the atmosphere and the formation of secondary pollutants. Waste burning and activities related to sand are also other sources that have been investigated in the new phases.

Despite this, mobile sources are still one of the most important centers of pollutant emission in Tehran. According to the results of the emission list, these sources account for about 97% of carbon monoxide emissions. On the other hand, power plants with a share of about 63% are the most important source of sulfur dioxide emission in the presented estimate. The difference in the contribution of sources in the emission of different pollutants shows that to deal with air pollution, it is not possible to focus on only one source or a control policy.

In Tehran, there are 19 active air pollution measurement stations and 35 noise pollution measurement stations. Also, with the launch of six new air quality monitoring stations, the monitoring capacity has increased by about 30%. Tehran Air Quality Control Company also pursues the possibility of predicting the state of air pollution for the next 72 hours by using information from the emission list, meteorological data and models of chemistry and transfer of pollutants.

Investigating and implementing solutions such as creating low-emission areas, developing electric and hybrid taxis, and using electric buses and motorcycles are among the measures that have been proposed in the way of reducing air pollution. However, the effectiveness of these measures depends on their compliance with the main sources of emission and the continuous implementation of control policies.

On the other hand, the publication list is not limited to Tehran. Ahmad Taheri - the head of the National Center for Air and Climate Change of the Environmental Protection Organization - has announced that the country's emission list based on the data of 1403 will be unveiled in 1405. This study is supposed to examine the main sources of pollutant emissions on a national scale and, in addition to megacities, sources such as agriculture, waste burning, transportation patterns and the effect of pollution transfer between cities are also considered.

In this approach, attention to secondary pollutants is also important; Pollutants that are not emitted directly from a source but are formed by chemical reactions in the atmosphere. Ozone in the hot season of the year and fine suspended particles in the cold season are among the cases that the investigation of their precursors can help to know more precisely the factors affecting air pollution.

Saeed Mahmoudi - Vice President of Human Environment of the Environmental Protection Organization - has also announced the preparation of emission lists for cities with air pollution problems, including smaller cities.

According to him, public access to air quality information and monitoring status can help increase environmental awareness and education. In this regard, the design of a system or an application to display the state of pollution in different areas is on the agenda; A tool that can provide people with information about winter pollution and summer dust and provide the context for public participation in reducing pollution.

Sediqeh Torabi - the former vice president of human environment of the Environmental Protection Organization - has also stressed the need to use its results in policy-making and executive programs, emphasizing that the preparation of the release list is the starting point. In this way, the value of the emission inventory is not limited to the identification of the contribution of sources, but will become apparent when its data lead to concrete decisions, measurable actions and real reductions of pollutants.

Finally, with the return of air pollution in the cold days of the year, the results of the emission list show once again that the management of this problem requires a look beyond cars; A view that, in addition to controlling mobile resources, also considers the contribution of industries, power plants, agriculture and other resources and defines a clear and evaluable plan for each one based on scientific data.