Online data show that the air quality index has surpassed critical levels in some neighborhoods of Tehran, while the air quality has been declared “unhealthy for all groups” in almost the entire city.
Officials shut the schools for the second day and have warned people to avoid outdoor activities and physical exertion.
Municipal officials have also imposed traffic restrictions in Tehran, letting cars into the streets in alternating shifts, depending on their number plates.
Average concentrations of the finest and most hazardous airborne particles in Tehran has far exceeded the World Health Organization's recommended maximum.
Every year, Iran's populous capital suffers severe air pollution when cold temperatures cause an effect known as inversion, during which a layer of warm air above the city traps in the pollution produced inside.
