Delhi Air 'Very Poor' Ahead of Diwali: AQI Hits 377 as Stage II Curbs Enter Force

As winter sets in, India's capital Delhi is once again battling a deterioration in air quality. On Wednesday morning the city's air quality index (AQI) stood at 377, in the 'very poor' category, raising health concerns for millions of residents.

The AQI measures PM2.5 — fine particulate matter about 30 times smaller than the width of a human hair, which can penetrate deep into the lungs. Breathing such polluted air over prolonged periods can cause respiratory problems and worsen existing illnesses, with children and older people particularly vulnerable.

India's pollution watchdog classifies AQI readings between 301 and 400 as 'very poor', while anything above 400 is considered 'severe'. The index takes into account eight major pollutants, including PM2.5.

Authorities have responded by invoking Stage II of the Graded Response Action Plan (GRAP), a set of emergency measures that become progressively stricter as pollution levels rise, introducing steps to curb dust, vehicle emissions and other sources of pollution.

The latest restrictions include more intensive road cleaning, higher parking charges to discourage private vehicle use and increased public transport services. Delhi Metro has introduced 20 additional weekday train trips, while authorities have been directed to stagger government office timings to ease traffic congestion. Officials said the measures were introduced after forecasts suggested air quality would remain very poor over the coming days.

Delhi and neighbouring parts of northern India grapple with hazardous air every winter, particularly around Diwali, one of India's biggest festivals, which is just days away. The festival is celebrated with lights, lamps and fireworks, which often worsen the city's already poor air quality by releasing fine particles and harmful gases into the atmosphere.

The annual pollution crisis is driven by a combination of factors, including vehicle exhaust, industrial emissions, falling temperatures, low wind speeds and the burning of crop stubble in neighbouring states. 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, northwesterly winds returned, carrying smoke from burning fields towards the capital.

The sharp rise in pollution follows an unusually clean October, when Delhi recorded its lowest average AQI for the month in eight years.

Authorities have imposed restrictions on firecrackers over the years, including outright bans on their manufacture, sale and use, but enforcing them has proved difficult. 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 they must carry QR codes allowing buyers and authorities to verify the manufacturer and certification details.