The Supreme court’s ban on sale of firecrackers in the National Capital Region (NCR) to lessen health risks this year had some impact as Delhi had its cleanest Diwali in three years, but pollution levels still peaked to dangerous levels on Thursday night and on Friday morning. Air pollution in Delhi hit several times the healthy limit on Friday. A thick, toxic haze engulfed Delhi that ranks among the world's most polluted cities the next morning. People clearly managed to procure crackers both from inside and outside NCR or used old stocks. PM 2.5, particulate matter, less than 2.5 micrometers in diameter, which can be inhaled and become lodged in the lungs and blood cells, soared dangerously. Its level, in micrograms per cubic meters, was recorded at 574. As per Indian standards, PM 2.5 levels must not be above 60. However, this was much better in comparison to last year's post-Diwali smog when the air quality index (AQI) recorded PM 2.5 level as 999, beyond which no readings are available The alarmingly high pollution was despite a Graded Response Action Plan (GRAP) coming into force from 15 October. The eight monitoring stations under the System of Air Quality and Weather Forecasting and Research (SAFAR) showed the city's air as severe: Mathura Road (709), Pusa (686), IGI Airport (560), Lodhi Road (563), Delhi University (475), Pitampura (518), Dhirpur (404) and Noida (448). SAFAR works under the union Ministry of Earth Sciences. It was a difficult Diwali evening for six-year-old Riya who has bronchitis. "She was coughing all through the night. We shut all our doors and windows. However, there was no relief. We plan to go out of the city from next year around Diwali," said Namrata Tyagi, her mother, who lives in Gole Market. Similar problems of coughing, watery eyes and difficulty in breathing were experienced, in particular, by children and the elderly. An analysis by the Centre for Science and Environment (CSE) has shown that despite the cracker sale ban, air pollution levels breached the emergency standards on Diwali night. But it is also clear that without the ban on the sale of firecrackers, the levels would have been far worse. Calm wind and more moisture in the air on the post-Diwali morning worsened the pollution build-up. According to a pre- and post-Diwali analysis report prepared by the Central Pollution Control Board (CPCB) and the CSE, air quality data collected from 13 monitoring stations showed 'very poor' quality during the day while pollution built up rapidly during the night, hitting the emergency level. The Capital showed relatively higher levels, as compared to NCR towns of Ghaziabad and Gurugram. "It is clear that Delhi-NCR requires a longer-term and systemic action than a one-off ban. The Supreme Court has already ordered a phase-down strategy with the help of regulation of chemicals, standards, reduced quantum of crackers, controlled bursting of crackers through community events, locational controls, etc. This must be implemented without delay for a longer-term solution to the problem," said Anumita Roychowdhury, executive director-research and advocacy, CSE