Delhi becomes the world's most polluted city as toxic smog covers the capital

New Delhi overtook Lahore on Friday to become the world's most polluted city as thick smog reduced visibility for its 20 million residents. Swiss air quality group IQAir recorded Delhi's air quality index at 334, placing it in the hazardous category. India's Central Pollution Control Board reported an even higher AQI reading of 403, classifying the air as severe. The difference between the Swiss and Indian numbers comes from the use of separate scales and methods to measure toxins. Dense smog forced cars and motorcycles to move slowly through major streets, often making it hard to see street lights.

Context

Air pollution worsens across northern India and neighbouring Pakistan during the winter months because cold, heavy air traps vehicle exhaust, construction dust, and smoke from crop burning near the ground. Official monitoring boards track these toxic particles daily to measure health risks for the public.