A severe wave of toxic smog enveloped India’s capital city on Wednesday, plunging air quality to hazardous levels and reducing visibility to as low as 100 meters in some areas. As winter settles in, the city faces worsening pollution, compounded by colder temperatures that trap dust, emissions, and smoke from farm fires in neighboring Punjab and Haryana.

According to real-time data from Swiss group IQAir, Delhi now holds the grim title of the world’s most polluted city, surpassing Lahore, Pakistan. IQAir recorded an air quality index (AQI) of over 1,000, far exceeding the hazardous threshold of 301. The particulate matter concentration (PM2.5) in Delhi’s air was more than 120 times the safe levels recommended by the World Health Organization, with PM2.5 particles small enough to penetrate the lungs and contribute to deadly respiratory and cardiac conditions.

Meanwhile, India’s Central Pollution Control Board (CPCB) reported an AQI of 350, which falls below India’s “severe” pollution threshold of 400. The discrepancy, experts say, arises from differences in the scale used for AQI conversion. Gufran Beig, a climate expert and Chair Professor at the National Institute of Advanced Studies, explained that the variation reflects distinct scales applied to pollutant concentrations.

The toxic air has prompted low visibility procedures at Indira Gandhi International Airport, where flights may be impacted. The India Meteorological Department (IMD) reported an average temperature drop from 17.9°C to 17°C on Wednesday morning, a decline expected to continue as the smog blocks sunlight.

Delhi’s government has indicated plans to use artificial rain as a potential countermeasure. Similar restrictions have been enforced in neighboring Pakistan’s Punjab province, where authorities have closed schools, banned outdoor activities, and implemented early closing hours for businesses in an effort to reduce exposure to hazardous air.