Is it the gasoline?

What is exactly causing all these pollution in Iran?
Usually a layer of smug covers Tehran, the capitol of Iran and most of the other great cities. The great Alborz mountains go underneath a blanket of soot. Eyes burn and its hard to breathe. There are a couple of major contributing factors to air pollution in Iran. The greatest factor is the traffic. There are more cars in the streets than there is room in the narrow streets. Most of the time, the highways look like parking lots when you look at them from above; not moving for hours in the evening times. Therefore, pumping a ton of exhaust into the air. Iran is under US sanctions and has to produce its own cheap gasoline and produce toxic formulations to keep the millions number of vehicles going. In addition to the low fuel quality, there is not much regulation and inspection going on over the older cars.

The other factor is the population growth. Each family member usually has their own car and when you drive in the streets you can see there's usually only one person in each car.
According to the discussion above, traffic and fuel are the most important elements of air pollution crisis in Iran and politicians keep arguing with each other about whether it is about lack of laws and standards or if it is about implementation of the laws.

Read more https://news.vice.com/article/air-pollution-is-causing-iran-to-cancel-soccer-games-and-keep-kids-home-from-school