Schools have been closed since Saturday and will remain shut until Wednesday The smog is mostly caused by heavy traffic as well as factory pollution, according to Tehran"s provincial governor TEHRAN: Dangerously poor air quality forced Iran’s government on Monday to extend school closures in the capital Tehran, a city home to over 10 million people. Schools have been closed since Saturday and will remain shut until Wednesday, the end of Iran"s workweek, according to the official IRNA news agency. Nearby mountains were completely obscured by the a thick layer of air pollution called an inversion that"s been hovering over the capital since last month. The smog is mostly caused by heavy traffic as well as factory pollution, according to Tehran"s provincial governor. It"s been worsened by a lack of wind and rain. Tehran’s air is among the most polluted in the world. Similar school closures were in effect in other cities as well. Still, despite the pollution, many students seemed to be enjoying their extended vacation, according to one schoolteacher in Tehran, Maryam Lavasani. But the smog doesn"t only affect children. Zahra Alipour, a 60-year-old homemaker with a chronic lung condition, told The Associated Press that she has trouble just going outside. "Breathing is really difficult for me. What can I do? If I don"t leave home, how can I take care of my daily jobs? And when I come out of the house, the air pollution really hurts me,” she said. Rahim Gharabaghi, a 54-year old taxi driver, wore a surgical mask while navigating Tehran"s traffic. He blamed the smog on older, deficient cars and problems with the fuel they burn, saying air pollution is present in smaller cities and towns as well. The data seems to back him up. Tehran"s provincial governor, Anoushirvan Bandpay, said Monday that cars are responsible for 60% of air pollution in Tehran, with diesel trucks playing a major role. Factories account for 18%, while electricity-generating plants are responsible for 12%, he told state TV. However, authorities have rejected claims about low-quality gasoline, saying it conforms to the "Euro 5" emissions standard. Inversions commonly hover over Tehran in the winter. The city is surrounded by tall hills and mountains on three sides. As cold, stagnant air settles in the valley, it traps automotive and other emissions that have no way of escaping. Mohsen Pourbagheri, 70, is a retired auto mechanic who says most birds have abandoned the capital. “When I was young there was a variety of birds, like starlings, fluttering over the city. Nowadays I only see crows in the sky."