Toxic smog has shrouded Pakistan's eastern city of Lahore for days as surging pollution spurs authorities to curb activities and set up a panel to oversee preventive efforts. Here is a look at what causes the hazardous air,

Delhi surpassed Lahore as the world's most polluted city, with its air quality index reaching a 'severe' 418. The smog, a mix of fog and smoke, reduced visibility, causing flight diversions. Low wind speed,

Delhi overtook Pakistan ’s Lahore as the world’s most polluted city in Swiss group IQAir’s live rankings, with an air quality index (AQI) score of more than 1,000, which is considered “hazardous”, but India ’s pollution authority said the AQI was around 350.