Shiraz的空气质量

Is Shiraz a polluted city?

Shiraz is the capital city of the Fars province in Iran, being the fifth most populous city in the whole country. A recent census showed the population to be around 1.86 million, a number that would have undoubtedly grown since this number was taken (in 2016), adding to the levels of pollution as is typical with any city undergoing an expansion of its population, along with added urbanization or industrialization.

Shiraz is considered to be one the oldest cities in ancient Persia (now modern day Iran), and for millennia it has been known as a trading center, with this still continuing on till today, with production and exportation of metals such as silver, carpets, cement and other industrial materials, as well as sugar and textile products. Whilst these are all great for a growing economy, they can bring with them some fair amounts of pollutive issues, which are displayed in Shiraz’s PM2.5 readings recorded over 2019.

In 2019, its yearly average of PM2.5 came in at 25.1 μg/m³, putting shiraz into the ‘moderate’ pollution bracket, one which requires a PM2.5 score of anywhere between 12.1 to 35.4 μg/m³ to be classified as such. As the name suggests, whilst the air quality is not overtly dangerous or hazardous, it is still present for a majority of the year, and could cause many issues for sensitive demographics such as young children or pregnant mothers, with pollution causing a whole host of issues for those who are still developing.

In terms of ranking, with its reading of 25.1 μg/m³, Shiraz came in at 616^th place out of all cities ranked worldwide, as well as being 12^th place out of all cities in Iran. As mentioned, whilst not disastrous, it still stands to reason that the pollution levels are still far from perfect and may present some issues for many of its citizens.

What are the main causes of pollution in Shiraz?

Being a large and highly populated city with an economy based around material production as well as export and trade, there would thus be subsequent rises in pollution levels related to these matters, with the large scale movement of people coupled with the manufacturing and shipping of goods all requiring the use of vehicles and factories.

Following on, with this in mind, one of the leading factors of pollution in Shiraz would be that of vehicular fumes, with hundreds of thousands of cars and motorbikes populating the roads, ferrying people back and forth on their daily commutes. Many of these vehicles would use lower quality fuels, leaded fuels as well as diesel, all of which can contribute massively to pollution levels when compared to any cleaner counterparts on an international scale.

This is just taking into account personal vehicles as well, with industrial ‘heavy duty’ vehicles such as lorries, trucks and buses all moving around and out of the city, carrying with them industrial loads. These heavy duty vehicles will often run on diesel fuels, and sometimes lack the proper maintenance to ensure that their engines are not too old or in too poor of a condition for road use.

Other forms of pollution would of course be the aforementioned factory emissions, with widescale production often utilizing coal as its main fuel source, as well as outputting any industrial effluence associated with whatever material is being produced (such as any factory that deals in plastic goods inevitably putting out plastic fumes of some form or another). Other forms of pollution would include sandstorms (introducing massive amounts of fine particulate matter into the air) as well as the improper disposal of refuse and waste, being burnt in open fires. Construction sites and road repairs would also contribute heavily, with many of them releasing dangerous materials such as silica dust, microplastics and even heavy metals such as lead, mercury and cadmium.

What are some health issues associated with breathing polluted air in Shiraz?

Whilst Shiraz may lack the disastrous levels of pollution as seen in other neighboring countries (with countries such as Afghanistan coming in with yearly averages of 58.80 μg/m³), it still stands to reason that any pollution or PM2.5 reading over the World Health Organizations (WHO's) target goal of 0 to 10 μg/m³ may have unhealthy consequences, and with the readings present in Shiraz being far in excess of this, there would undoubtably be related health issues, especially for vulnerable groups.

Some of these would include instances of rapid aging or scarring of the lungs, with fine particulate matter and chemical compounds such as nitrogen dioxide (NO₂) causing a reduction in lung capacity, as well as long term damage that can not only drive up the mortality rate but also make those affected more susceptible to respiratory illnesses such as pneumonia, bronchitis, emphysema and asthma.

Other issues would be increased rates of lung and throat cancer, as well as ischemic heart disease, damage to the kidneys and liver, as well as reduced function of the reproductive system. Expectant mothers who are exposed to excessive levels of pollution may find themselves having miscarriages, or babies born prematurely with a low birth weight or cognitive or physical defects present.

When is pollution at its worst in Shiraz?

Going off of the data in 2019, the months that came in with the visibly worst readings of pollution were July and December. These are very sporadic and spread out readings of pollution, indicating that Shiraz may not be subject to year round patterns in its pollution levels that other cities or countries see (for example in India nearly every city has a clear and sometimes massive increase in pollution levels at the beginning and end of the year).

December came in with a PM2.5 reading of 35.3 μg/m³, putting it still within the moderate bracket, albeit at the absolute highest end. The most polluted month was July, with a reading of 35.6 μg/m³, making it the only month of the year to move up a notch into the ‘unhealthy for sensitive groups’ bracket, a reading nearly three times that of the cleanest month of the year.

When is the air quality at its best in Shiraz?

To contrast with the previous question and thus give people the best information on when the air quality is at its best and free from smoke, haze, smog and other unwanted contaminants, it appears that February, June and November came in with the best readings. Once again these are extremely sporadic and follow little patterns, sometimes having adjacent months with vastly different pollution readings, showing the random nature of pollution occurring in Shiraz.

For the previously mentioned months, the PM2.5 readings were 19.6 μg/m³, 18.2 μg/m³ and 11 μg/m³ respectively, making November by far the cleanest month of the year. With its reading of 11 μg/m³ it finds itself in the ‘good’ ratings bracket (10 to 12 μg/m³ required for classification), the only month of the year to do so and one that would have a considerably safer level of air quality than is seem for much of the year.