伊朗的空气质量

How polluted is Iran?

Iran is a country located in western Asia, bordering other countries such as Iraq, Turkey, Afghanistan and Pakistan. Its capital city, Tehran, is an important economic and cultural center, being one of the largest cities in west Asia with over 8.8 million inhabitants. Iran as a country has 83.2 million people living there, as of 2018.

In terms of its levels of pollution, Iran has its own fair share of issues that lead to a decline in air quality, with many of its major cities seeing instances of smoke, haze and fumes blanketing the air during certain times of the year, due to massive vehicular and factory emissions, as well as from other sources such as construction sites and the burning of fossil fuels.

When observing the numbers, in 2019 Iran came in with a PM2.5 reading of 24.27 μg/m³, putting it in the ‘moderate’ pollution bracket, requiring a reading of 12.1 to 35.4 μg/m³ to be classified as moderate. This PM2.5 count also placed it in 27^th place out of all countries ranked worldwide, coming in just behind South Korea and Sri Lanka, which both had readings of 24.78 μg/m³ and 25.20 μg/m³ respectively.

PM2.5 refers to fine particulate matter that is 2.5 micrometers or less in diameter. It’s extremely small size makes it a very important gauge in pollution levels, and as such PM2.5 is a major component in calculating the overall air quality. It has a larger cousin, PM10, which has many damaging effects on human health, but due to being the bigger size of 10 micrometers or less in diameter, does far less damage to human health, and as such PM2.5 is the main unit of measurement that will be used to discuss pollution levels in Iran.

Looking at some of the bigger cities, it becomes apparent that a large amount of them suffer from fairly elevated levels of pollution and thus would be of concern for their citizens. Ones such as Hendijan, which came in at first place out of the most polluted cities in Iran in 2019, had PM2.5 readings going up to 45.6 μg/m³, as well as having a yearly average of 38.2 μg/m³.

This average reading places it into the ‘unhealthy for sensitive groups’ bracket, and as the name implies, a large amount of the population would be at risk when exposed to air of such low quality, such as children, pregnant mothers, the elderly as well as the sick or immunocompromised. Those with sensitivities towards chemicals and pollution in general can also see a reduced quality of life, with chronic conditions such as sore throats, chest infections and skin allergies afflicting them throughout the year.

Hendijan’s reading of 38.2 μg/m³ also placed it into the 261^st place out of all cities ranked worldwide. So, to recap, whilst Iran does not suffer from the disastrous levels of pollution that its neighboring countries such as Afghanistan and Pakistan do, it certainly has its own problems that need addressing if it is to improve its US AQI rating and reduce PM2.5 levels in the air.

What are the main causes of pollution in Iran?

Iran sees a wide range of pollution coming from different sources. It is common for many cities in Asia, as indeed the rest of the world to have the same sources of pollution, but with varying levels coming from each source depending on a number of conditions such as topography, elevation, meteorological conditions and such all playing a part. Iran as a country mostly consists of many mountainous regions and plateaus. It is subject to a wide variety of weather conditions, ranging from arid to semi-arid, and even sub-tropical along the coast and northern regions.

It is of importance to mention geographical features, including that of urban geography, because they play a large part in the accumulation of pollutants. Urban geography such as large amounts of high-rise buildings can cause pollution build ups, accumulating and finding themselves unable to disperse due to lack of winds, creating a pollution sink. The same can be said of mountain ranges, with countries like Nepal also being subject to pollution accumulations due to being in a valley surrounded by many mountains.

In regards to Iran's main causes of pollution, they would include sources such as vehicular fumes, including both basic motor vehicles such as cars and motorbikes, as well as heavy duty vehicles such as trucks, lorries and buses above a certain weight that typically are powered by diesel engines. With many older models of these heavy-duty vehicles still found populating the roads across Iran, their emissions are far greater than that of newer vehicles that runs on cleaner fuel sources.

In the capital city Tehran, approximately 80% of all pollution stems from vehicular emission, a worryingly high number given the fact the number of vehicles only increases each year. Other sources of pollution include factory emissions, as well as the improper disposal of garbage or refuse material, with vehicular and factory pollution being the most prominent.

When is pollution at its worst in Iran?

Observing the data taken in years past from a majority of cities in Iran, it is apparent that a trend emerges. This trend shows that pollution is always higher towards the end of the year, although there are sporadic differences between the cities that step outside of the normal readings. To use several cities as examples, the capital Tehran will be used, as well as the cities of Shooshtar and Varamin.

Tehran's highest readings were in November and December, with a yearly average of 25.9 μg/m³, putting it into the moderate pollution bracket. Looking at the numbers at the end of the year, they step fairly far outside of what the yearly average was, going up to 43.9 μg/m³ and 41.1 μg/m³, both of which are in the ‘unhealthy for sensitive groups’ bracket.

Shooshtar had its highest reading of the year in November, with a very high reading of 55.9 μg/m³, the highest monthly recording in the entire year of 2019 in Iran. This was enough to put Shooshtar’s November reading into the ‘unhealthy’ bracket, a highly undesirable rating that requires a PM2.5 reading of anywhere between 55.5 to 150.4 μg/m³ to be classed as such, and once again as the name would imply, means that the air quality can have a number of highly negative consequences on those unfortunate enough to be breathing it, particularly over longer periods of time.

The city of Varamin came in with a yearly average of 33 μg/m³, putting it in 3^rd place out of all cities in Iran. Its most polluted months were once again November and December, by quite a significant margin. Varamin’s cleanest month was April, with a reading of 23.7 μg/m³. In contrast, the last two months of the year came in with PM2.5 readings of 48.8 μg/m³ and 50.6 μg/m³ respectively.

This pertains to many cities throughout Iran, with a majority of them demonstrating the highest levels of pollution in the latter months. In a few cases that showed exception to this, the mid-year period, particular June and July, came in with some particularly elevated readings, with the cities of Shiraz, Sejzi, Meybod and Qazvin all coming in with their highest readings in the mid-year.

With this information in mind, preventative measures can be taken for Iran's inhabitants at these times of the year, when levels of smoke, haze and pollution would be permeating the atmosphere. People can stay up to date in real time via the use of air visual maps, available on the IQAir website as well as on the AirVisual app. Preventative measures during heightened months of pollution such as avoiding outdoor activities, or the wearing of high-quality particle filtering masks would be of great benefit in avoiding the highly negative side effects of elevated pollution levels.

What are the main pollutants found in the air in Iran?

With pollution sources being mainly found in vehicular emissions as well as smoke and fumes given off by factories, the pollutants found on both ground level and in the upper atmosphere via satellite would be quite straightforward in terms of prediction.

Heavy use of vehicles and areas that see high volumes of traffic often have elevated levels of pollutants such as nitrogen dioxide (NO_2­) and sulfur dioxide (SO₂) in the air, with nitrogen dioxide being particularly prominent in its release from vehicles, often being a somewhat helpful indicator of how much pollution is being generated by vehicles alone.

With high levels of nitrogen dioxide present in the atmosphere, there is more often than not a high volume of vehicles moving through that particular area. Sulfur dioxide can also be found in larger quantities in areas that see ships or cargo freights, such as those that would be docking in the coastal side of Iran near the Persian Gulf. Ship fuels often have different regulations on the chemical composition, and tend to have elevated amounts of sulfur in them, leading to larger emissions of sulfur dioxide, which besides being a dangerous gas to respire can also have knock on effects on the environment due to its ability to cause instances of acid rain to occur.

Other pollutants that would be present in the air would be ones such as black carbon and volatile organic compounds (VOC’s), both of which are produced from the incomplete combustion of fossil fuels as well as organic matter, and as such would find their origin from both vehicles (particularly heavy-duty ones that rely on diesel fuels) as well as the industrial sector, with factories running on coal powered machinery.

Examples of VOC’s include benzene and formaldehyde, known as being volatile due to their chemical makeup causing them to become gases at much lower temperatures, thus becoming respirable and subsequently more dangerous to human health. Black carbon is a major component of soot and is often found in high quantities in areas that see large volumes of traffic, in the form of both dangerous and visually unappealing black dust coating roadside surfaces.

Besides being highly carcinogenic as well as small enough to penetrate into the bloodstream, black carbon can also cause a heating effect to the environment due to its property of absorbing solar radiation and converting it directly into heat, thus affecting not only human health but the climate.

Other materials found in abundance in the atmosphere in pollution hotspots (industrial zones or areas of high traffic) would include carbon monoxide (CO) and ozone (O₃). Lastly, other polluting causes such as construction sites or poorly maintained roads would give off large amounts of finely ground gravel or silica dust, as well as the release of microplastics and toxic metals such as lead, mercury and cadmium. All of the aforementioned compounds and materials have a host of terrible effects on the health of people exposed to them, and should be taken into consideration when entering into periods of higher air pollution, particularly for vulnerable portions of the population.

What can Iran do to improve its pollution levels?

With a large increase in respiratory related diseases in more recent times, it has come to the countries attention that some action needs to be taken against polluting sources. Some steps that have been taken, or are being planned to put into action, include initiatives such as the eventual removal of older buses and cars and replacing them with newer models that run on natural gas, a step that would put a massive dent into pollution levels, particularly in cities such as Tehran where traffic related pollution figures so highly.

The introduction of vehicle inspections is planned as well, something that if enforced efficiently would see widespread removal of outdated and pollution causing monsters off the road, in particular referencing the heavy-duty trucks that are a common sight still in many parts of the road, putting out vast black clouds in their wake.

Other improvements are coming in the form of increased spending in public transport infrastructure, as well as the introduction of electric bicycles for public use. Lastly, the introduction of air pollution control plans, which could see the closer monitoring of offending factories that exceed safe levels of pollution in the surrounding atmosphere, and the subsequent charging or fining of such offenders. With many initiatives such as these being planned and some already coming into play, Iran can hopefully see a reduction in its pollution levels in years to come.