Lahore and Karachi, once again, claim two of the top three spots on the list of world's most polluted cities, as their Air Quality Index (AQI) on Tuesday morning was recorded at 'Very Unhealthy' and ‘Unhealthy’ levels, respectively.

According to IQAir, a Swiss air quality monitor, Lahore had the highest level of pollution in its air in the world, which was categorized as ‘Very Unhealthy’ with its air quality index measured at 282 in the morning.

The PM2.5 (particulate matter) concentration in the capital city of Punjab was recorded at 46.4 times higher than the WHO annual air quality guideline value.

PM2.5 refers to fine particulate matter with a diameter of less than 2.5 micrometers. The term is employed to characterize the levels of particles in both outdoor and indoor environments.

Also Read: Lahore is the most polluted city in the world

Within Lahore, the pollution levels surpassed the 'Hazardous' level, with the highest AQI of 340 recorded around the Polo Ground area in Cantt, followed by Phase 8 of DHA at 337 and The Mall road at 321.

The air quality of Lahore has consistently remained unhealthy, not just over the past couple of months, but also in the last few years with the onset of the ‘fifth season’ of smog. The air quality levels continue to dip after September until at least February.

According to the IQAir data, the second most polluted city in the world was New Delhi, India, with an air quality index of 198 (Unhealthy).

The monitor reported that the concentration of PM2.5 in the Indian capital was 29.2 times more than WHO guideline value.

The third most polluted city in the world on Tuesday morning was Karachi with an air quality index of 196 , and categorized as ‘Unhealthy’.