Delhi Overtakes Lahore as World’s Most Polluted CityPakistan

India’s official Central Pollution Control Board put the figure higher, at 403, and rated it “severe”. The two readings differ because the Swiss and Indian authorities use different AQI scales and methodologies to calculate and classify air pollution levels.

Videos from news agency ANI showed cars and motorcycles emerging from dense smog, with the haze also obscuring street lights on the city’s main roads, as visibility fell sharply across the capital.

The smog settled over the city of 20 million people, cutting visibility for commuters and leaving roads and buildings wrapped in a thick grey haze through the day.

A seasonal problem

Pollution is a seasonal problem in many parts of northern India and neighbouring Pakistan. As winter sets in, cold, heavy air traps vehicle emissions, construction dust and smoke from agricultural burning close to the ground, pushing pollution levels sharply higher.

The three sources behind the haze — exhaust fumes from vehicles, dust raised by construction work, and smoke from crop burning in surrounding farmland — combine each winter to leave a thick pall hanging over cities across the region.

An AQI reading of up to 50 is considered good, with little or no health risk. Delhi’s reading on Friday stood far above that level on both the Swiss and the Indian measures, underlining how poor the air had become in the Indian capital.

Lahore had earlier found some relief after rain, when its air quality index dropped to 111. But with winter approaching, both cities remain exposed to the same seasonal pattern, as cold air continues to trap pollution close to the ground.

Friday’s readings put Delhi ahead of Lahore at the top of the global ranking of major cities, with the winter smog season now under way across northern India and neighbouring Pakistan.