|星期四, 1月 21|
中等 78 美国 AQI
|星期五, 1月 22|
中等 79 美国 AQI
|星期六, 1月 23|
对敏感人群不健康 129 美国 AQI
不健康 157 美国 AQI
|星期一, 1月 25|
中等 83 美国 AQI
|星期二, 1月 26|
中等 65 美国 AQI
|星期三, 1月 27|
中等 66 美国 AQI
|星期四, 1月 28|
中等 67 美国 AQI
|星期五, 1月 29|
中等 65 美国 AQI
|星期六, 1月 30|
中等 52 美国 AQI
Isfahan is a city located in the province of the same name in Iran, being the capital of said province as well as being counted as a major city, being the third largest in the country after Tehran and Mashhad. It finds itself located some 406km away from the capital city of Tehran, and is sitting in a geographically important location at the intersection between the various north-south and east-west routes in Iran. It has been the capital city of Iran twice in the past, and still today retains much of its past splendor, having one of the largest city squares in the world located within its limits, designated as a UNESCO world heritage site.
Regarding its levels of pollution, Isfahan came in with a PM2.5 reading of 26.4 μg/m³ over the course of 2019, as its yearly average. This reading put it into the ‘moderate’ pollution bracket, albeit in the mid to high end of it, as the moderate rating requires a PM2.5 number of anywhere between 12.1 to 35.4 μg/m³ to be classified as such. Whilst not catastrophic and nowhere near as elevated as some other cities of neighboring countries such as Afghanistan or Pakistan, it certainly shows that the city has some pollutive issues, with a few months going up a notch into the next group rating, showing that the air quality in Isfahan could have a detrimental effect on many of its citizens.
This 2019 reading of 26.4 μg/m³ put Isfahan in 561st place out of all cities ranked worldwide, as well as in 8th place out of all cities ranked in Iran, coming in as more polluted than the capital city of Tehran.
Much like the rest of Iran, Isfahan sees its pollution arising from multiple sources and being compounded further by other issues such as meteorological occurrences, as well as geographical features playing a part (including urban geography, with mountain ranges as well as a plethora of tall buildings all able to trap haze and pollution within the city and stop it from being cleared out by prevailing winds).
One of these causes would be emissions from vehicles, with many personal ones such as cars and motorbikes populating the roads, driving up the PM2.5 readings around the year, particularly those that run on diesel fuels as well as lower quality fuels, often not subject to the same stringent control measures that are seen on the international circuit, although this is rapidly changing as countries like Iran become more open in their race towards cleaning up their air quality.
Heavy duty vehicles such as trucks and lorries can also put out large amounts of pollution, often running on diesel fuels as well, with engines that may be well past their expiry date in terms of safe usage, providing poor combustion of fuels that leads to leakage of dangerous chemicals and pollutants, all of which makes its way into the air and atmosphere.
Other causes would be factory emissions, sandstorms, dust and pollution given off by construction sites and road repairs, with many dangerous materials such as heavy metals and microplastics also finding themselves released from such sites.
Observing the data taken over the course of 2019 as an accurate gauge of how polluted the air in Isfahan is, there is a pattern that starts to emerge, although with a slight degree of randomness in its nature, as is present in all cities in Iran, lacking the prominently distinct low and high pollution seasons seen in other countries such as India or Bangladesh.
Looking at the data recorded, it appears that the pollution levels are at their worst at the very beginning and end of the year, with an unusual rise in PM2.5 levels during the months of June and July, making beginning, middle and end of the year the most polluted times, somewhat of an anomaly when it comes to worldwide pollution readings.
Pollution levels start to take a turn for the worst around May, with a PM2.5 reading of 19.5 μg/m³ present. This quickly jumps to 37.1 μg/m³ in June, and then 30.6 μg/m³ in July. From here until the end of the year the pollution levels stay at a consistently high level in the mid 20’s, until November when the pollution level spikes again, with a reading of 39.4 μg/m³ and then a reading of 39.3 μg/m³ in December.
This shows that November is the most polluted month of the entire year, with December coming in at a close second, as well as June, July and January all having their own poor ratings of air quality.
Following on directly from the sporadic periods of heightened pollution in the previous question (although of note is that despite lacking an overtly clear pattern, the winter months tended towards higher levels of pollution), as mentioned is that January also came in with a poor reading of pollution. It is after here that the pollution levels began to abate somewhat, with a drop down to 18.1 μg/m³ witnessed in February, nearly half of the reading taken in January.
This dropped further in March, with a reading of 13.6 μg/m³, then followed by 14.4 μg/m³ in April. After April, the pollution levels start to show signs of a rise again, with a reading of 19.5 μg/m³ in May as mentioned. So, it can be considered that the period of time between February to May is when the air quality is at its best, with the month of March coming in as the cleanest, with a reading of 13.6 μg/m³, only 1.6 units away from moving down to the ‘good’ ratings bracket.
With pollution readings that break into the unhealthy for sensitive groups bracket, and a year round reading that is on the higher end of the moderate spectrum, although there would not be disastrous consequences for Isfahan’s citizens, it should be noted that any reading above the WHO's target goal of 10 μg/m³ or less may present some health issues, rising in occurrence and risk as the PM2.5 levels also go up.
Some of these issues would be irritation to the throat, skin, eyes and nose, as well as heightened instances of infections of the throat and lungs. A broad range of respiratory disorders may also present themselves, with one such as pneumonia and bronchitis being of note.
Rates of cancers can go up, particularly of the lungs and throat, as well damage to the blood vessels and circulatory system occurring, due to the ability of fine particulate matter (such as black carbon) being able to enter the blood stream through the small air sacs in the lungs.