Delhi air quality worsens to 'very poor' ahead of Diwali as firework restrictions take effect

The city's AQI, which measures PM2.5 fine particulate matter that can clog lungs, stood at 377 on Wednesday morning. Breathing such polluted air over prolonged periods can cause respiratory problems and worsen existing illnesses, with children and older people particularly vulnerable.

Delhi and neighbouring parts of northern India grapple with hazardous air every winter, particularly around Diwali, when fireworks release fine particles and harmful gases. The annual crisis is driven by vehicle exhaust, industrial emissions, falling temperatures, low wind speeds and the burning of crop stubble in neighbouring states.

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 Punjab and Haryana. A recent storm had brought rain and stronger winds, helping clear the air, but as the weather settled, north-westerly winds returned, carrying smoke from burning fields towards the capital.

The measures aim to curb dust, vehicle emissions and other sources of pollution. India's pollution watchdog classifies AQI readings between 301 and 400 as "very poor", while anything above 400 is considered "severe".

With Diwali 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, between 06:00 and 07:00 and between 20:00 and 22:00 on 7 and 8 November. The court also banned fireworks within 300m 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. But the court acknowledged that conventional firecrackers had continued to be sold as green alternatives even when a complete ban was in place, and it directed police to patrol designated sales areas, carry out random QR-code checks and seize illegal firecrackers.

Mumbai has also recorded elevated pollution levels over the past month. Its AQI reached 322 on 24 October, placing it in the "very poor" category, but improved to 89, classified as "satisfactory", on Wednesday. Neighbouring Navi Mumbai recorded a "moderate" AQI of 118. The spike was attributed to low wind speeds, construction dust, garbage burning, firecracker emissions and pollutants carried from neighbouring regions.