Azernews.Az

Tehran experienced 147 days, in which air quality was substandard based on the Pollutant Standards Index (PSI) , during the last solar year, which ended on March 21, Iranian Parliament's Environment Committee Mohammadreza Tabesh said.

The number of such days was 217 two years ago, he said, Shargh newspaper reported.

Tehran, which spans over an area of 900 square kilometers, is considered one of the world's most polluted cities. On weekends, the city's population reaches 15 million, leading to traffic jams and high pollution in the city centre.

Tehran's pollution is mainly blamed on bumper-to-bumper traffic in a city wedged between two mountains which trap fumes. But major Iranian cities also struggle with pollution on a seasonal basis.

Pollution is also exacerbated by increasing reliance on domestic production of petrol of a lower grade, and therefore more polluting, a byproduct of Western sanctions on Iran's fuel imports.

Some experts and officials say the low quality of the gasoline and diesel fuel that is used is responsible for the heavy smog in Tehran. The fact that some other big cities, like Isfahan, Mashhad, Arak, Karaj, Qom, Tabriz, and Ahvaz, are facing more or less a similar situation backs up this view.

Iran has previously had laws implemented for dealing with the problem of air pollution, however none of them worked.