Residents in the Indian capital Delhi woke to a thick blanket of smoke as the city’s air quality worsened to “very poor” after revellers burst millions of firecrackers overnight, despite a ban, to celebrate <a href="https://www.thenationalnews.com/world/2022/10/24/india-lights-up-in-celebration-of-diwali/" target="_blank">Diwali</a>. Delhi, home to 22 million people, suffers from <a href="https://www.thenationalnews.com/world/2022/10/17/delhis-air-quality-deteriorates-to-severe-level-ahead-of-diwali/" target="_blank">pollution due to toxic emissions</a> from factories, vehicles, construction sites and agricultural fires, but every year a frenzied night of fireworks aggravates the problem. The Air Quality Index in the city — the world’s most polluted capital — was hovering at the “very poor” category with PM 2.5 breaching the 300 mark on average on Tuesday morning, according to the Central Pollution Control Board. The Particulate Matter measurement, or PM 2.5, represents the presence of the finest dust and other harmful particles measuring less than 2.5 microns (millionths of a metre). They can penetrate deep into the lungs and enter the bloodstream. The World Health Organisation considers 5 micrograms per cubic metre as the safe level of exposure when it comes to particulate pollution, compared to 300 micrograms measured overnight. On an average, five million tonnes of firecrackers are burnt during the Diwali festival in Delhi, according to a 2018 report by environmental charity Urban Emissions. Hindus for centuries have been <a href="https://www.thenationalnews.com/uae/heritage/2022/10/22/inside-the-bustling-dubai-factory-producing-50-tonnes-of-diwali-sweets/" target="_blank">celebrating Diwali to mark the return of the holy figure Lord Ram</a> to Ayodhya, his place of birth, after completing 14 years in exile, by lightening earthen lamps and candles. The use of firecrackers on Diwali began in the 18th century when Maratha rulers organised firework displays for the general public — 400 years after they were first introduced by Mongols to the country in the 14th century from China. Several state governments, including the one governing the capital Delhi, have banned firecrackers. Some have allowed only “green crackers,” which are low-emission fireworks, in stipulated hours. In 2018 the Supreme Court banned crackers that contain substances such as lead, arsenic and barium but allowed the use of less polluting varieties. It called Delhi a “gas chamber” in 2019 over its deteriorating air. The state government <a href="https://www.thenationalnews.com/world/2022/10/21/delhi-bans-firecrackers-on-diwali-to-curb-pollution/" target="_blank">banned the production, storage, sale and bursting</a> of crackers to curb air and noise pollution levels and imposed a fine of 200 rupees to 5,000 rupees ($2.50 to $60) and imprisonment of up to three years for being caught selling or bursting crackers. But the unending flurry of fireworks on the biggest festival continued, increasing the pollution levels. However, the city’s air quality was still the best for Diwali in four years, according to the Central Pollution Control Board. Delhi’s satellite city Noida registered an air quality index of 324, meaning that the air quality posed a danger to human health. Any AQI above 100 is considered unhealthy, while anything between 300 and 500 (the top of the scale) is hazardous.