LAHORE: Amid restricted visibility in the morning owing to foggy conditions, Lahore ranked first among top ten most polluted cities in the world on the Air Quality Index (AQI), according to a report on Saturday.

Average air quality index reading of Lahore recorded 264, while Karachi remained third from the top of the list. Lahore’s Garhi Shahu locality measured maximum 466 reading, while Gulbarg had 379 reading on the index. The AQI around the Canal Road was recorded 419. It is to be mentioned here that AQI as high as 151-200 is considered unhealthy, while an AQI reading between 201 to 300 is more harmful and AQI rate over 300 mark is extremely hazardous.

According to experts, the air becomes heavier in the winter as compared to summer, causing poisonous particles in the atmosphere to move downwards and making the atmosphere polluted. As a result, a layer of polluted particles, including large amounts of carbon and smoke, covers a city. The smoke produced by factories and by burning coal, garbage, oil or tyres enters the atmosphere and the impact of it appears at the onset of winter and remains till the season’s end, experts said.

Thus, air pollution reaches to extremely dangerous levels in cold weather, severely compromising air quality. Healthy atmosphere in such a situation is subject to rainfall, which washes off all hazardous particles. The AQI calculation is based on five categories of pollution: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.