Crypto mining is responsible for the air pollution at Iran.

Iran is the city with the most bitcoin's crypto mining farms.

According to a Bloomberg report,despite the cold winter they have in Iran bitcoin mining farms coupled the demand for heat that it has as result to use low grade fuel oils like plants because of natural gas shortage. Because of this hit in many Iranian cities it was possible to see "thick layers of toxic smog"

And before some days 1600 bitcoin mining farms were closed at Iran.

PS The photo was taken from https://ifpnews.com/irans-power-plants-allowed-to-mine-cryptocurrencies