Lahore has again emerged as the most polluted city in the world with its air quality being classed as “hazardous”, according to air quality monitoring platform IQAir.

In past few years, air pollution has become one of the most pressing public health and environmental crises facing Pakistan. Various cities of the country, most notably Lahore, deal with smog, especially in the winter months. The phenomenon is attributed mainly to industrial emissions, vehicular pollution, stubble burning and air movement.

Lahore was placed at the top of the list of most polluted cities globally on Wednesday morning, with an air quality index (AQI) of 452, while Karachi ranked ninth at 179, according to the IQAir live tracker.

On Tuesday, the platform issued an air quality alert for Pakistan as major cities experienced “unhealthy” to “hazardous” levels of air pollution, posing “serious health risks to residents, especially children and the elderly”.

At the time, Lahore’s air quality index (AQI) had soared to 507 — well into the “hazardous” bracket (301+). Karachi ranked sixth on the list with an “unhealthy” AQI of 178 a day earlier.

“Residents are advised to limit outdoor activity, keep windows closed, wear masks when outside, and use air purifiers indoors,” the alert said.

Punjab authorities have made efforts to tackle the smog in Lahore, including via the use of water sprinklers and rapid response initiatives to curb stubble-burning. However, despite claiming an improvement in the air quality, the pollution persists.