Schools remain closed as smog covers Tehran

Schools remain closed in Tehran and several other cities on Wednesday as severe air pollution continued to hit Iran.Thick smog has blanketed the capital for more than a week, prompting authorities to urge residents to stay home.
The air pollution index stood at 162 on Wednesday.Tehran's air is among the most polluted in the world and school closures because of poor air quality are a regular occurrence.The smog is mostly caused by heavy traffic as well as factory pollution and typically worsens during the cold season.