Millions of firecrackers lit up Delhi’s skies overnight on Thursday, covering the city in a thick blanket of toxic smog, despite a ban on Diwali fireworks in the city. Toxic emissions from factories, vehicles, construction sites and agricultural fires regularly turn the Indian capital into one of the most polluted cities globally, but every year a frenzied night of fireworks aggravates the air pollution crisis. Residents woke up to the sharp smell of fireworks in the air and neighbourhoods were covered in a putrid yellow toxic mix of fog and pollutants across the megacity of 20 million people. Many complained of itchy burning eyes, headaches and breathing issues. Levels of PM 2.5 – the fine particles linked to chronic bronchitis, lung cancer and heart disease – breached the safe limits by nearly 11 times at 680, according to the government-run System of Air Quality Weather Forecasting and Research (Safar). The figures are nearly 14 times higher than the World Health Organisation’s safe limits. 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. At the beginning of the week, the city’s air quality plummeted to the “very poor” category, but the unending flurry of fireworks during the biggest festival turned it to an alarming “severe”. Delhi’s overall Air Quality Index hovered around 700, Safar said, as it advised residents to avoid outdoor activities and wear masks. A score of 200 is considered severe. The health risks of such a bad smog are many, and those recovering from Covid-19 are particularly at risk, doctors said. "Air pollution can have acute and chronic effects when there is a long-term exposure. It can cause acute bronchitis, lower and upper respiratory tract infections, burning eyes, nasal issues and pneumonia," said Dr Vikas Maurya, Director of Pulmonology at the Fortis Hospital in Delhi. "Patients who have asthma can have acute attacks. There are chronic effects which one feels after many years...effects on heart, cardiovascular issues, plaques, heart attacks, brain strokes due to subsequent exposure." The capital had banned all fireworks over concerns of a pollution spike but residents showed mass disregard. Police in recent days seized more than 5,000 tonnes of firecrackers and arrested dozens to enforce the ban opposed by many Hindus over claims it hurts their religious sentiments. Delhi’s satellite cities like Gurugram and Noida had restricted displays of less toxic “green crackers” to a two-hour window. The Supreme Court had banned crackers in 2018 that contain substances like lead, arsenic and barium but allowed use of less polluting varieties. It called Delhi a “gas chamber” in 2019 over its deteriorating air and reiterated its ban on toxic firecrackers on Monday, while noting the right to health was supreme. A 2020 report by Swiss organisation IQAir named 22 Indian cities in the world’s 30 most polluted cities, with Delhi ranking as the most polluted capital city. Last year, international medical journal <i>The Lancet</i> said India lost 1.67 million people to toxic air in 2019. Delhi is typically gripped by the smog crisis at the onset of winter season when temperature dips and air moisture rises. It is further aggravated by northwest winds that bring smoke from India’s northern breadbasket states of Punjab and Haryana. Farmers use the earth scorching method to clear their fields of crop residue to prepare their land for the next planting season. Stubble burning was outlawed in 2015 but it continues unabated, with Safar reporting more than 2,300 farm fires on Thursday. The pollution monitoring agency said smoke from crop fires contributed 35 per cent to the city’s polluted air on Friday, while the overnight fireworks further pushed the pollution levels 10 times over.