The latest air quality and pollution city ranking shows Lahore to be the most polluted with a ranking of 327.

The list is updated every few minutes, but a snapshot earlier on Monday showed Lahore topped the list, way ahead of the next-worst city.

As per the air pollution data by the US Air Quality Index (AQI) on Monday morning, India’s Delhi is ranked second, Croatia's Zagreb third, while Kolkata and Mumbai have been ranked fourth and fifth, respectively.

Meanwhile, Karachi is ranked 14 and has an AQI of 156, classified as unhealthy.

An AQI ranking between 301-500 or above is classified as hazardous. "AQI greater than 300 would trigger health warnings of emergency conditions. The entire population is more likely to be affected," Air Now said.

Air quality in Lahore usually worsens during the winter season from October to February when farmers in the wider Punjab province set light to the remnants of crops, producing smoke that adds to smog. At the same time, weather changes mean pollutants remain trapped in the air for longer.

Punjab govt decides to take action against those burning crop residue

The city suffers from high levels of air pollution and regularly ranks at the top of the live pollution rankings of major global cities.

The Punjab government has decided to take action against those causing air and environmental pollution through the burning of crop stubble, garbage, and industrial and vehicular emissions.

Directions have also been issued to authorities concerned to enforce section 144 throughout the province as part of efforts to combat the smog. Under section 144, burning of crop residue and garbage has been banned across the province for one month from October 6.