The Punjab government blamed poor air quality this week on pollution drifting from India, where firecrackers set off during the Hindu festival of Diwali over the weekend blanketed much of the north in toxic smog. Lahore topped Swiss group IQAir's ranking of the world's most polluted major cities for a second day on Tuesday, with an air quality index (AQI) of 263, categorised as "very unhealthy". The city's concentration of PM2.5, harmful airborne particles small enough to penetrate deep into the lungs, was 37.2 times above the World Health Organisation's annual guideline, IQAir said. Punjab Senior Minister Marriyum Aurangzeb said pollutants had been carried into the region by light winds and air drifting from India in the aftermath of Diwali. "However, air pollution is expected to gradually decrease from early afternoon as weather conditions improve and winds shift direction," she said. Read More: Indian capital chokes with pollution after Diwali fireworks. IQAir ranked Delhi the world's second-most polluted major city on Tuesday, with an AQI of 188. Indian government data showed that firecrackers were responsible for nearly 55 per cent of the PM2.5 in the Indian capital a day earlier. Vehicle emissions, construction dust and smoke from crop-waste burning are also major contributors to winter pollution on both sides of the border. Pakistan had similarly attributed its toxic air in 2024 to crop-waste burning in Indian Punjab, but officials from India's weather department had said at the time that the wind direction meant the airflow was actually from Pakistan into India. Indian Prime Minister Narendra Modi's Bharatiya Janata Party has also blamed crop-waste burning in Indian Punjab — governed by a regional opposition party — for Delhi's poor air quality this month. Local media reported a sevenfold increase in farm fires in the state on Sunday, when Diwali was celebrated. Indian Punjab's state government, however, says incidents of crop-waste burning have fallen compared with previous years.