Delhi air quality deteriorates ahead of Diwali as pollution controls tightened

Delhi is once again battling worsening air pollution as the onset of winter brings a familiar deterioration in air quality to the Indian capital and much of northern India. The city's Air Quality Index (AQI), which measures PM2.5 fine particulate matter capable of clogging lungs, has crossed 300, entering the "very poor" category and raising health concerns for millions of residents. India's pollution watchdog classifies readings between 301 and 400 as "very poor", while anything above 400 is considered "severe". On Wednesday morning, Delhi's AQI stood at 377. Prolonged exposure to such polluted air can cause respiratory problems and worsen existing illnesses, with children and older people particularly vulnerable. Authorities have responded by invoking Stage II of the Graded Response Action Plan (GRAP), introducing measures to curb dust, vehicle emissions and other pollution sources. During more severe episodes in the past, Delhi authorities have also introduced hybrid schooling, work-from-home arrangements and restrictions on certain vehicles. The sharp rise follows an unusually clean October, when Delhi recorded its lowest average AQI for the month in eight years. Experts have attributed the sudden deterioration to falling temperatures, slow winds and an increase in crop-residue burning in the neighbouring states of Punjab and Haryana. A recent storm had brought rain and stronger winds that helped clear the air, but as the weather settled, north-westerly winds returned, carrying smoke from burning fields towards the capital. With Diwali, one of India's biggest festivals, just days away, there are concerns that fireworks could push pollution levels even higher. Last year, Delhi woke up to a toxic haze the morning after the festival despite a court directive to use less-polluting firecrackers. On Monday, India's Supreme Court allowed the manufacture, sale and use of certified green firecrackers in Delhi and neighbouring areas for a limited period. The court said the crackers could be set off only between 06:00 and 07:00 local time and between 20:00 and 22:00 on 7 and 8 November, during the Diwali weekend. It also banned fireworks within 300 metres of hospitals, care homes, schools and other designated silence zones. Green firecrackers use modified chemical formulations designed to produce fewer emissions than conventional fireworks, and must carry QR codes allowing buyers and authorities to verify details of their manufacturer and certification. Enforcement, however, remains a major challenge. In its latest order, the Supreme Court acknowledged that conventional firecrackers had continued to be sold as green alternatives even when a complete ban was in place, and it has directed police to patrol designated sales areas, carry out random QR-code checks and seize illegal firecrackers. The problem is not confined to the capital. Mumbai, India's financial hub, has also recorded elevated pollution levels over the past month despite coastal winds that typically help disperse pollutants. On 24 October, Mumbai's AQI reached 322, placing it in the "very poor" category, a spike attributed to low wind speeds, construction dust, garbage burning, firecracker emissions and pollutants carried from neighbouring regions. The city's air quality has since improved, recording an AQI of 89, classified as "satisfactory", on Wednesday, while neighbouring Navi Mumbai recorded a "moderate" reading of 118. The improvement follows nearly two weeks of smoggy conditions, during which residents shared photos and videos of the haze on social media.