New Delhi: Post-Diwali, several Indian cities have shown a peak in fine particulate matter (an air pollutant), as per a preliminary analysis by the National Clean Air Programme (NCAP) Tracker, which tracks India’s air quality data and the government’s NCAP.Fine particulate matter or PM2.5 are fine, inhalable particles – around 2.5 mm in diameter – are produced due to the emission of fossil fuels such as coal. Fireworks are also known to temporarily increase levels of PM2.5 in the atmosphere along with other pollutants such as sulfur dioxide in high concentrations. Such particulate matter can cause health concerns including respiratory ailments.Higher PM2.5 post-DiwaliFine particulate matter, therefore, is considered a significant public health concern. Hence, PM2.5 is also one of the pollutants that India’s government-run air quality monitoring stations measure. According to India’s Central Pollution Control Board, and under the National Ambient Air Quality Standard (NAAQS), the safe level of annual PM2.5 is set as 40 μg/m3 and the 24-hour average as 60 μg/m3. The National Air Quality Index also lists a “good limit” for daily average PM2.5: 0-30 μg/m3. The revised global air quality guidelines by the World Health Organization in 2021, however, set a stricter standard: 5 μg/m3 for an annual average and 15 μg/m3 for a 24-hour average.The NCAP Tracker, a policy tracker that keeps tabs on the implementation of the government’s National Clean Air Programme and its effectiveness, and also analyses air quality data compiled from government-run monitoring stations, analysed the daily average PM2.5 levels across 11 cities in the country over three days – a day before Diwali (November 11), the day of Diwali (November 12) and a day after Diwali (November 13). The 11 cities are Bengaluru, Bhopal, Chandigarh, Chennai, Delhi, Gandhinagar, Hyderabad, Lucknow, Mumbai and Patna. The festival of Diwali is marked by aerial fireworks in most parts of the country. Studies such as this one in 2020 have shown that fireworks during the festival days “contribute to an increase of PM2.5 loading in Delhi significantly”.According to the NCAP Tracker’s preliminary analyses for this year, PM 2.5 levels on this Diwali and for the 12 hours after (till noon on November 13) were above the CPCB’s daily average ‘good’ limit of 30 ug/m3 in all the cities analysed. Patna in Bihar showed the highest average PM 2.5 level on the day of Diwali 2023 (November 12), at 206.1 ug/m3. This is around 13.7 times more than the WHO’s daily safe limit of 15 ug/m3.Delhi leads in spikeOn November 13 (from midnight to 12 pm), Delhi recorded the highest PM2.5 average of 300.9 ug/m3. Per the report, Delhi also witnessed the highest spike (recorded at 15-minute intervals) – at 999.5 ug/m3 at Pusa on November 13 at 1:30 am). Several other capital cities also experienced extremely high PM2.5 levels on this year’s Diwali and the following day (November 13), the report noted. However, it is difficult to compare levels of PM2.5 – or any other pollutant across years – unless other confounding factors that are at play such as wind speed and rainfall (which will affect PM2.5 levels and make it vary from year to year in each city) are accounted for. Aarti Khosla, director of Climate Trends, which runs NCAP Tracker along with Respirer Living Sciences, suggests a drastic step: phasing out the firecracker industry itself over the next 2-3 years. “Stemming supply,” she said, in a press release, “is the only way to asphyxiate demand in this case.”“A Supreme Court ban in Delhi NCR was flouted fully and shows that a different approach where the centre and state must work together is needed,” she added. Phasing out firecrackers may seem an extreme step for many while “environment-friendly” fireworks are now available. These, according to researchers, emit 15-65% less particulate matter. However, the researchers also found that such fireworks still deteriorate air quality rather significantly.Three Indian cities among the most pollutedAs per Swiss technology company IQAir, which measures live air quality (PM2.5 levels) using data from monitoring stations and sensors operated by a range of organizations including governmental bodies and research institutions, three Indian cities are among the top ten cities across the world that have the most polluted air.As of 3 pm on November 14, Delhi was leading as the most polluted city (highest PM2.5 levels across the world), with an Air Quality Index (AQI) of 306. The AQI here is measured based on WHO standards and the ideal limit is an annual PM2.5 level of 5 μg/m3. The IQAir lists an AQI of more than 300 as “Hazardous”. “At this extreme, there’s a health warning of emergency conditions. The entire population is likely to be severely affected,” per IQAir.Mumbai, the capital of Maharashtra, was in fourth place, with an AQI of 156 – which falls in the “unhealthy” category. Kolkata came ninth, with an AQI of 127, which is termed as “unhealthy for sensitive groups”.