Pakistan ’s smog situation has gone from bad to worse as air pollution rose to a record in Lahore. Sensors tracked by the Swiss monitor IQAir recorded an air quality index of 1,300 in the country’s second-largest city at 5 p.m. local time, the highest this year and well beyond a level of 50 that is deemed safe.

The crisis has prompted a flurry of responses from local authorities, as the country grapples with its most severe air pollution event in years. According to several Pakistani media reports the Punjab Provincial Disaster Management Authority had declared smog a “calamity” and instituted emergency measures.

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,

The air quality index is alarmingly high in Pakistan and India. This week, smog has drastically reduced visibility, obscuring views of landmarks such as the Taj Mahal in Agra. Consequently, many flights have been delayed.