Every year, Delhi and northern states battle hazardous air during the winter months of October to January due to plummeting temperatures, smoke, dust, low wind speed, vehicular emissions and crop stubble burning. This time, experts say that the condition is likely to get worse in the coming days.

A study published in June found that air pollution killed 135 million people over the last four decades around the world, with India and China accounting for the bulk of the fatalities. In 2023, Delhi’s AQI was recorded between 445 and 520 just a day after Diwali, placing it firmly in the “severe” category.

Delhi overtook Pakistan ’s Lahore as the world’s most polluted city in Swiss group IQAir’s live rankings, with an air quality index (AQI) score of more than 1,000, which is considered “hazardous”, but India ’s pollution authority said the AQI was around 350.