Lahore has once again topped the list of world’s most polluted cities, as its Air Quality Index on Thursday morning was recorded at ‘Unhealthy’.

According to IQAir, a Swiss air quality monitor, Lahore had the highest level of pollution in its air in the world, which has been categorized as ‘Unhealthy’ with its air quality index measured at 175 around noon on Thursday.

The PM2.5 (particulate matter) concentration in the capital city of Punjab was recorded at 14.1 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.

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According to the IQAir data, the second most polluted city in the world is New Delhi in India, with an air quality index of 166 (Unhealthy) and the main pollutant being PM2.5.

The monitor reported that the concentration of PM2.5 in the Indian capital is 16.8 times more than WHO guideline value.

Interestingly, around this time every year, Lahore and New Delhi keep switching positions to remain at the top of the list of most polluted cities in the world.

The third most polluted city in the world around Thursday noon was Dubai in the United Arab Emirates with an air quality index of 157 and categorized as ‘Unhealthy’.

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.

On Wednesday also, the average air quality index of the city was recorded at 175, which was 178 a day before; the level has been hovering above 160 since last month.

Moreover, after Lahore, the second most polluted city of Pakistan on Thursday was Peshawar with an air quality index of 157 at Thursday noon.

As per IQAir, the world’s cleanest city was Nagoya, Japan.