Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the ... Read more at: https://www.deccanherald.com/national/north-and-central/pm25-delhi-pollution-during-july-sept-quarter-second-lowest-in-5-years-cse-1155654.html
The Centre for Science and Environment (CSE) assessment captured seven successive winters and pre-winter trends, starting from January 1, 2015 in Delhi and NCR The average PM2.5 pollution in Delhi in the winter season has declined by about 20 per cent as compared to the pre-pandemic period, according to a new report released by the Centre for Science and Environment (CSE) on Thursday (October 20). It also said Diwali this year is being observed early in the season “which means the warmer and windier conditions will help dilute the pollution that is staple of Diwali night celebrations”. However, concentrated stubble burning due to prolonged rains (in September end and October) may compound the problem. Also Read: Delhi Government Starts Spraying Bio-Decomposer To Avoid Stubble Burning The assessment captured seven successive winters and pre-winter trends, starting from January 1, 2015 in Delhi and the National Capital Region (NCR). It is based on real time data available from the 81 operational air quality monitoring stations in the region. The PM2.5 concentration for winter (October 1 to February 28) used to hover around 180-190 microgram per cubic metre before the pandemic. It has come down to 150-160 microgram per cubic metre since then, the report said. Anumita Roychowdhury, executive director of research and advocacy at the CSE, said the objective of the report is to understand the trend and “the starting line of the onset of the winter pollution season or pre-winter levels in this region”. The seasonal average is still over 150 per cent above the 24-hour standard (60 microgram per cubic metre) and almost four times the annual standard (40 microgram per cubic metre) despite the improvement, the green thinktank noted. Also Read: Commission For Air Quality Management Discuss Action Plan To Tackle Growing Air Pollution In Delhi-NCR It said peak pollution showed a similar trend as the seasonal average. The report said, Peak pollution (worst 24-hour average) used to cross 800 microgram per cubic metre at individual stations pre-pandemic. It has been hovering in the 700-800 microgram per cubic metre range during the last three winters. The CSE, however, said the peak pollution numbers did not project the actual level as the Central Pollution Control Board (CPCB) had capped it at 1,000 microgram per cubic metre in 2016-17, greatly compromising the assessment of peak pollution level. Researchers said the winter of 2021-22 was less polluted as compared to 2020-21 for most NCR cities. Ghaziabad registered a 30 per cent improvement, the highest among all major cities, but its PM2.5 level was still about 2.5 times the 24-hour standard, they said. “Greater Noida (28 per cent), Noida (23 per cent) and Faridabad (16 per cent) also registered improvement in excess of Delhi (12 per cent),” the report said. Also Read: 1,695 Farm Fires Reported In Delhi, Its Adjoining States, Punjab: Commission For Air Quality Management Gurugram, with 11 per cent improvement, was the worst performer among the core NCR cities. In absolute concentration terms, Faridabad, with an average of 159 microgram per cubic metre, was the most polluted city of the NCR last winter. Unlike previous two years, the smoke from the farm stubble fires has not overwhelmed the air quality of the region yet and rains in early October have also kept the air relatively clean so far. Also, previous years’ data shows that Diwali night can add 300-600 microgram per cubic metre of PM2.5 to Delhi’s air if the business-as-usual scenario continues.
Centre for Science and Environment (CSE) said on Thursday. The air quality in De .. Read more at: https://energy.economictimes.indiatimes.com/news/oil-and-gas/concentrated-stubble-burning-around-diwali-may-compound-problem-cse/94999239
Pollution levels in the July-August-September quarter were preceded by one of the most polluted summers this year, unlike in 2020 when the trimester followed the cleanest ever summer (March-May) due to extraordinary conditions created because of hard pandemic lockdowns, the green think tank said. Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the Centre for Science and Environment (CSE). Pollution levels in the July-August-September quarter were preceded by one of the most polluted summers this year, unlike in 2020 when the trimester followed the cleanest ever summer (March-May) due to extraordinary conditions created because of hard pandemic lockdowns, the green think tank said. "Therefore, it is important to understand what aided in cleaning up the Delhi air. Looking at the rainfall data it becomes evident that distribution of rainfall has a relatively higher impact on seasonal air quality than the absolute quantity of rainfall," it said. There have been 45 rainy days in July, August and September this year as compared to just 39 rainy days in the quarter last year. Powered By VDO.AI "These six extra rainy days helped keep the seasonal average low despite total rainfall this monsoon having been just one-third of the previous monsoon," the CSE said.
Other measures to prevent air quality from worsening include vacuum-based sweeping of roads every day, water sprinkling to prevent dust pollution, and strict enforcement of dust control measures at construction and demolition sites. The air quality in Delhi-NCR will worsen to "very poor" by Saturday, Commission for Air Quality Management (CAQM) said, directing authorities to ban the use of coal and firewood in hotels, restaurants, and open eateries, as well as diesel generators except for essential services. Other measures to prevent air quality from worsening include vacuum-based sweeping of roads every day, water sprinkling to prevent dust pollution, and strict enforcement of dust control measures at construction and demolition sites. A report by the Centre for Science and Environment (CSE) on Thursday suggests that despite the threat of air quality worsening, the air quality has improved over pre-Covid levels as a decline of 20% was witnessed in the pollution levels. The report by the CSE emphasised that the air has been much cleaner this year due to the rainfall in September and October. However, the intensity of the early winter pollution will depend a lot on the trend in the crop fires along with the impact of Diwali. The PM2.5 concentration for winter (October 1 to February 28) used to hover around 180-190 microgram per cubic metre before the pandemic. It has, however, come down to 150-160 microgram per cubic metre since then, the report said. BJP MP Manoj Tiwari demanded a lifting of the cracker ban by filing a plea in the Supreme Court. However, the Supreme Court on Thursday refused an urgent hearing of a plea seeking the removal of a complete ban on firecrackers in the national capital, saying "let the people of Delhi breathe clean air". "Let the people of Delhi breathe clean air. People should not spend money on firecrackers instead they should eat sweets," the bench said and added that the plea will be coming up for hearing along with the main matter pending before the court. A report by Zee News from November 2021 suggests that stubble burning contributes to 36 percent, construction work makes for 30 per cent of pollution and emissions from vehicles cause 28 per cent. The remaining six percent is perhaps then caused by firecrackers burnt on Diwali. The Centre on Wednesday said incidents of stubble burning have started increasing rapidly, especially in Punjab, and the state government has not taken adequate steps to prevent farm fires.
Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the Centre for Science and Environment (CSE). Pollution levels in the July-August-September quarter were preceded by one of the most polluted summers this year, unlike in 2020 when the trimester followed the cleanest ever summer (March-May) due to extraordinary conditions created because of hard pandemic lockdowns, the green think tank said. ''Therefore, it is important to understand what aided in cleaning up the Delhi air. Looking at the rainfall data it becomes evident that distribution of rainfall has a relatively higher impact on seasonal air quality than the absolute quantity of rainfall,'' it said. There have been 45 rainy days in July, August and September this year as compared to just 39 rainy days in the quarter last year. ''These six extra rainy days helped keep the seasonal average low despite total rainfall this monsoon having been just one-third of the previous monsoon,'' the CSE said. These additional rainy days also pushed the regular start of bad air quality days further down the month of October, it said. The PM2.5 average for the quarter stood at 38 microgram per cubic metre in 2021, 41 microgram per cubic metre in 2019 and 43 microgram per cubic metre in 2018. The CSE had on Thursday said the average PM2.5 pollution in Delhi in the winter season has declined by about 20 per cent as compared to the pre-pandemic period. The PM2.5 concentration for winter (October 1 to February 28) used to hover around 180-190 microgram per cubic metre before the pandemic. It has come down to 150-160 microgram per cubic metre since then, it said. However, the seasonal average is still over 150 per cent above the 24-hour standard (60 microgram per cubic metre) and almost four times the annual standard (40 microgram per cubic metre) despite the improvement, the green think tank noted. (This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)
PM2.5 pollution in Delhi during July-Sept quarter 2nd lowest in 5 years: CSE Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020. Read more at: https://www.etvbharat.com/english/national/bharat/pm2-dot-5-pollution-in-delhi-during-july-sept-quarter-2nd-lowest-in-5-years-cse/na20221021132639421421288
Delhi’s PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the Centre for Science and Environment (CSE).
Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the Centre for Science and Environment (CSE). Pollution levels in the July-August-September quarter were preceded by one of the most polluted summers this year, unlike in 2020 when the trimester followed the cleanest ever summer (March-May) due to extraordinary conditions created because of hard pandemic lockdowns, the green think tank said. "Therefore, it is important to understand what aided in cleaning up the Delhi air. Looking at the rainfall data it becomes evident that distribution of rainfall has a relatively higher impact on seasonal air quality than the absolute quantity of rainfall," it said.
Though Diwali this year will be observed during the "warmer part of the early winter", concentrated stubble burning in Delhi's neighbouring states may compound the problem, the Centre for Science and Environment (CSE) said on Thursday. The air quality in Delhi-NCR starts worsening in October due to unfavourable meteorological factors such as low temperatures and wind speed, which do not allow dispersion of pollutants. A cocktail of emissions from firecrackers and stubble burning in neighbouring states further deplete the air quality. The CSE said Diwali this year is being observed early in the season "which means the warmer and windier conditions will help dilute the pollution that is staple of Diwali night celebrations". Unlike previous two years, the smoke from the farm stubble fires has not overwhelmed the air quality of the region yet and rains in early October have also kept the air relatively clean so far. However, a prolonged spell of rains in early October has delayed paddy harvesting in parts of Punjab and Haryana that could lead to a spike in stubble burning incidents as farmers would be in a race against time to prepare their fields for the next crop.
Though Diwali this year will be observed during the warmer part of the early winter, concentrated stubble burning in Delhis neighbouring states may compound the problem, the Centre for Science and Environment CSE said on Thursday.The air quality in Delhi-NCR starts worsening in October due to unfavourable meteorological factors such as low temperatures and wind speed, which do not allow dispersion of pollutants.A cocktail of emissions from firecrackers and stubble burning in neighbouring states further deplete the air quality.
The average PM2.5 pollution in Delhi in the winter season has declined by about 20 per cent as compared to the pre-pandemic period, according to a new report released by the Centre for Science and Environment (CSE) on Thursday. It also said Diwali this year is being observed early in the season "which means the warmer and windier conditions will help dilute the pollution that is staple of Diwali night celebrations". However, concentrated stubble burning due to prolonged rains (in September end and October) may compound the problem. http://www.millenniumpost.in/delhi/delhi-pm25-pollution-in-winters-has-dipped-20-compared-to-pre-pandemic-period-cse-496589
Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the Centre for Science and Environment (CSE). Pollution levels in the July-August-September quarter were preceded by one of the most polluted summers this year, unlike in 2020 when the trimester followed the cleanest ever summer (March-May) due to extraordinary conditions created because of hard pandemic lockdowns, the green think tank said. "Therefore, it is important to understand what aided in cleaning up the Delhi air. Looking at the rainfall data it becomes evident that distribution of rainfall has a relatively higher impact on seasonal air quality than the absolute quantity of rainfall," it said. There have been 45 rainy days in July, August and September this year as compared to just 39 rainy days in the quarter last year. "These six extra rainy days helped keep the seasonal average low despite total rainfall this monsoon having been just one-third of the previous monsoon," the CSE said. These additional rainy days also pushed the regular start of bad air quality days further down the month of October, it said. The PM2.5 average for the quarter stood at 38 microgram per cubic metre in 2021, 41 microgram per cubic metre in 2019 and 43 microgram per cubic metre in 2018. The CSE had on Thursday said the average PM2.5 pollution in Delhi in the winter season has declined by about 20 per cent as compared to the pre-pandemic period. The PM2.5 concentration for winter (October 1 to February 28) used to hover around 180-190 microgram per cubic metre before the pandemic. It has come down to 150-160 microgram per cubic metre since then, it said. However, the seasonal average is still over 150 per cent above the 24-hour standard (60 microgram per cubic metre) and almost four times the annual standard (40 microgram per cubic metre) despite the improvement, the green think tank noted. PTI GVS CK
The average PM2.5 pollution in Delhi in the winter season has declined by about 20 per cent as compared to the pre-pandemic period, according to a new report released by the Centre for Science and Environment (CSE) on Thursday. It also said Diwali this year is being observed early in the season "which means the warmer and windier conditions will help dilute the pollution that is staple of Diwali night celebrations". However, concentrated stubble burning due to prolonged rains (in September end and October) may compound the problem. The assessment captured seven successive winters and pre-winter trends, starting from January 1, 2015 in Delhi and the National Capital Region (NCR). It is based on real time data available from the 81 operational air quality monitoring stations in the region. The PM2.5 concentration for winter (October 1 to February 28) used to hover around 180-190 microgram per cubic metre before the pandemic. It has come down to 150-160 microgram per cubic metre since then, the report said. Anumita Roychowdhury, executive director of research and advocacy at the CSE, said the objective of the report is to understand the trend and "the starting line of the onset of the winter pollution season or pre-winter levels in this region". The seasonal average is still over 150 per cent above the 24-hour standard (60 microgram per cubic metre) and almost four times the annual standard (40 microgram per cubic metre) despite the improvement, the green thinktank noted. It said peak pollution showed a similar trend as the seasonal average. "Peak pollution (worst 24-hour average) used to cross 800 microgram per cubic metre at individual stations pre-pandemic. It has been hovering in the 700-800 microgram per cubic metre range during the last three winters," the report said. The CSE, however, said the peak pollution numbers did not project the actual level as the Central Pollution Control Board (CPCB) had capped it at 1,000 microgram per cubic metre in 2016-17, greatly compromising the assessment of peak pollution level. Researchers said the winter of 2021-22 was less polluted as compared to 2020-21 for most NCR cities. Ghaziabad registered a 30 per cent improvement, the highest among all major cities, but its PM2.5 level was still about 2.5 times the 24-hour standard, they said. "Greater Noida (28 per cent), Noida (23 per cent) and Faridabad (16 per cent) also registered improvement in excess of Delhi (12 per cent)," the report said. Gurugram, with 11 per cent improvement, was the worst performer among the core NCR cities. In absolute concentration terms, Faridabad, with an average of 159 microgram per cubic metre, was the most polluted city of the NCR last winter. Unlike previous two years, the smoke from the farm stubble fires has not overwhelmed the air quality of the region yet and rains in early October have also kept the air relatively clean so far. Also, previous years' data shows that Diwali night can add 300-600 microgram per cubic metre of PM2.5 to Delhi's air if the business-as-usual scenario continues. PTI GVS RCJ
Delhi's PM2.5 pollution average for the July-August-September quarter this year stood at 37 microgram per cubic metre, only marginally higher than the five-year low of 36 microgram per cubic metre recorded during 2020, according to an analysis by the Centre for Science and Environment (CSE).
As Delhi and the National Capital Region (NCR) brace for the upcoming winter, it remains to be seen if the seasonal average of PM2.5 during winter — that had improved during the pandemic but had stagnated post-pandemic — will further bend or increase. This winter season is also starting from a much cleaner benchmark due to rains in September and October. Centre for Science and Environment’s (CSE) Urban Lab has released its winter pollution assessment – the objective, says Anumita Roychowdhury, executive director, research and advocacy, CSE, has been “to understand the trend and the starting line of the onset of the winter pollution season or pre-winter levels in this region. This would also capture the longer term context of seasonal variation and annual trends in particulate pollution.” This is the first analysis of the third edition of Urban Lab’s Air Quality Tracker Initiative which was started in the 2020-21 winter to study the impact of pandemic lockdown on the air quality of Delhi-NCR. “The intensity of winter pollution and severity of smog episodes will depend on the effectiveness of the long term multi-sector action so far in the entire region of Delhi and NCR and also on the enforceability of the short term emergency action. Only the effectiveness of the air pollution control measures targeting all key sources will determine if the winter pollution trend that had stabilised post pandemic, will continue to hold and improve or worsen further,” says Roychowdhury. “The onset of the winter has been much cleaner this year due to the rains. But the intensity of the early winter pollution will depend a lot on the trend in the crop fires and also the impact of Diwali. Though Diwali is happening during the warmer part of the early winter, prolonged rains can delay and lead to concentrated burning later compounding the problem,” says Avikal Somvanshi, analytic expert at the Urban Lab. This is an assessment of annual and seasonal trends in PM2.5 concentration for the period 1 January 2015 to 17 October 2022 (winter is defined as from October 1 to February 28). This captures seven successive winter seasons and pre-winter trends in Delhi and the National Capital Region. This analysis is based on the real time data available from the current working air quality monitoring stations in Delhi-NCR. A huge volume of data points have been cleaned and data gaps have been addressed based on the USEPA method for this analysis. This analysis covers 81 continuous ambient air quality monitoring stations (CAAQMS) spread across cities of Delhi-NCR. Meteorological data for the analysis is sourced from the Palam weather station of India Meteorological Department (IMD). Fire count data is sourced from NASA’s Fire Information for Resource Management System, specifically Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) product. Estimate of contribution of farm stubble fire smoke to Delhi’s air quality is sourced from Ministry of Earth Science’s System of Air Quality and Weather Forecasting and Research (SAFAR). Key findings This winter has started on the cleanest note with five “good” AQI days (for PM2.5) in the first two weeks of October. This happened due to an extended rainfall period but effects of it have started to wane as PM2.5 levels have risen above 90 µg/m3 (“poor” AQI breakpoint)on October 16. This pollution level is still low compared to previous years but it is expected to rise quickly. This rise is being driven by smoke from the farm stubble fires starting to enter the region. As per SAFAR, this smoke contributed about 3 per cent to Delhi’s PM2.5 level on 17th October. This is happening now because burning activities have picked up in Punjab-Haryana-Delhi. The total radiative fire power of these fires in Punjab-Haryana-Delhi breached 2,000 Watt on 16th October. This is less than half of the value recorded in 2020 and 2021 for the same period, implying massive burning is in store in the coming few days. Based on previous years’ observations it can be said that the situation can worsen if the business as usual scenario continues. Seasonal PM2.5 average for the winter (post-pandemic) shows about 20 per cent improvement compared to the winters of 2015-18; but the progress has stagnated: Overall, long term data shows that improvement made in reducing pollution levels during the winter season has stagnated in last three years. Smog episodes are again starting to get longer and pose a dire threat to public health not just in Delhi but the whole of NCR. Delhi’s seasonal air quality for winter (1 Oct to 28 Feb) used to hover around 180-190 µg/m3 before pandemic and for the last three winters it has come down to 150-160 µg/m3. Despite the improvement the seasonal average is still over 150 per cent above the 24-hr standard and almost four times the annual standard. Peak pollution shows a similar trend as seasonal average. Peak pollution (worst 24-hr average) used to cross 800 µg/m3 at individual stations pre-pandemic, it has been hovering in 700-800 µg/m3 range during the last three winters. These peak pollution numbers should be taken with caution as CPCB introduced a 1,000 µg/m3 capon reported real-time data in 2016-17, which has greatly compromised the assessment of peak pollution level. Actual peak levels must be higher than what CPCB data shows. It must also be noted that the worst station for peak pollution has changed seven times in the last seven winters. Shadipur, DTU, CRRI Mathura Road, JLN Stadium, Alipur, ITO and Rohini have occupied the worst peak pollution title in the last seven winters. These are spread across the city with no clear pattern. This indicates that the winter pollution is regional in nature and short-term peak build-up can happen anywhere based on local meteorology and pollution sources. Seasonal PM2.5 average for 2021-22 winter was 10-30 per cent lower compared to 2020-21 winter for most major NCR cities — but Ghaziabad and Faridabad fared worse among these cities: Winter of 2021-22 was relatively less polluted compared to winter of 2020-21 for most NCR cities. Ghaziabad registered a 30 per cent improvement that was highest among major cities, but its PM2.5 level was still about 2.5-times the 24-hr standard. Greater Noida (28 per cent), Noida (23 per cent) and Faridabad (16 per cent) also registered improvement in excess of Delhi that registered a 12 per cent improvement. Gurugram with 11 per cent improvement was the worst performer among the core NCR cities. In absolute concentration terms, Faridabad with a seasonal average of 159 µg/m3 was the most polluted city of NCR last winter. Across the larger NCR, Muzaffarnagar was the worst performer as it registered a 1 per cent increase in winter level. Bulandshahr with 28 per cent improvement was the best performer among major non-core NCR cities. Baghpat with seasonal average of 142 µg/m3 was the most polluted city outside the core-NCR. Alwar with a winter average of 50 µg/m3 was the only major city in NCR that registered a seasonal level lower than the 24-hr standard. Intensity and duration of smog episodes remain worrisome: A smog episode is defined for the purpose of emergency action under Delhi’s Graded Response Action Plan when the levels of PM2.5 remain in “severe” category for three consecutive days. In this study, if two consecutive smog episodes are separated by only one day and the PM2.5 level of that day doesn’t drop below 200 µg/m3 then the whole period is considered a single extended smog episode. Last winter season, there were three distinct smog episodes counting 20 smog days (see Table in full report). This was more than the previous two winters. 2020-21 winter had 14 smog days while 2019-20 winter had 19. Most smog days were observed in the 2018-19 winter when four smog episodes were recorded with a total of 31 smog days. Average intensity of smog episode last winter was 306 µg/m3 which was lower than that of previous two episodes, but this marginally lower intensity is negated by the longer duration of the smog episodes. It must also be noted that winters with relatively lower seasonal averages have longer and more smog episodes. This requires deeper investigation. Impact of rain and farm stubble fire smoke on the air quality is highly pronounced: Each year, the air in October and November becomes unbreathable due to the clustering of pollution-causing and compounding events. The festive season leads to increases in local pollution due to traffic chaos and firecrackers, which is compounded by the cooling of the weather that lowers the mixing height and sets inversion. Burning of crop waste in Punjab and Haryana further adds to the pollution load, which is compounded by the retreating monsoons, which transport the smoke down the Gangetic Plains. Only sobering element during these two months is rain, which can wash down the pollution if the downpour is strong and prolonged – but it is only a temporary relief. This relationship is evident from the data. Farm stubble fires of Punjab-Haryana-Delhi are increasing both in numbers and intensity: Last year registered highest instances of farm stubble fire in the last seven years — 2021 October-November saw a 10 per cent jump in observed fire count by MODIS and 5 per cent increase by VIIRS compared to 2020 October-November. Similarly, the total fire radiative power from these fires were 13 per cent and 7 per cent higher compared to the 2020 fires as observed by MODIS and VIIRS respectively. In fact, there is a consistent increase in fire instances and intensity since 2019. It remains to be seen what will happen this year. Diwali night pollution continued to remain high in previous years: PM2.5 concentration on Diwali night (8pm to 8am) last year stood at 747 µg/m3, 22 per cent higher than that in the 2020 Diwali night. The levels on 2021 Diwali night were 4.5 times the average night-time levels recorded in the week preceding Diwali. It is noted that hourly concentrations can go beyond 1,000 µg/m3. In the 2021 Diwali, 26 of 38 operational monitoring stations hit the 1,000 µg/m3 mark. In 2020, 23 out of 38 stations had hit the 1,000 µg/m3 mark, while in 2019 the number stood at 22 stations. 2022 monsoon was the second cleanest in the last eight years: The seasonal average for the monsoon (July, August and September) this year stood at 37 µg/m3 which is only marginally higher than lowest monsoon average of 36 µg/m3 that was recorded during the 2020 monsoon. The ultra-low pollution level recorded during the 2020 monsoon was preceded by a cleanest ever summer (March-May) due to extraordinary conditions created because of lockdowns. But this monsoon has been preceded by one of the most polluted summers – therefore, it is important to understand what aided in cleaning up the Delhi air. Looking at the rainfall data it becomes evident that distribution of rainfall has a relatively higher impact on seasonal air quality than the absolute quantity of rainfall. This monsoon, there have been 45 rainy days compared to just 39 in the previous monsoon. These six extra rainy days helped keep the seasonal average low despite the fact that the total rainfall this monsoon was just one-third of the previous monsoon. These additional rainy days also pushed the regular start of bad air quality days further down the month of October. Rains kept air quality in check during the first two weeks of October: Delhi received an unprecedented 115 mm of rainfall in the first two weeks of October this year — this translated into the cleanest start to winter since wide scale monitoring started in 2018. The PM2.5 average for the first two weeks of October stood at 43 µg/m3 which is less than half of the level recorded in 2020 for the same period. This October, so far, there have been five days of “good” AQI (PM2.5 sub-category), which is the most recorded in the last eight winter seasons. All these “good” AQI days fell on rainy days. Last year, two “good” AQI days were recorded for the entire winter season, while the previous winters had no “good” AQI days. Air quality is starting to deteriorate: Relief given by extended rainfall period has come to an end as PM2.5 levels have risen above 100 µg/m3 on October 16. This is still low compared to previous years but it is expected to rise quickly. Smoke from farm stubble fires that have started is contributing to the trend. As per SAFAR, this smoke contributed about 3 per cent to Delhi’s PM2.5 level on October 17. This is relatively low compared to contributions in previous years for this time of the year. This is happening now because burning activities have picked up in Punjab-Haryana-Delhi. The total radiative fire power of these fires in Punjab-Haryana-Delhi breached 2,000 Watt on October 16, which is less than half of the value recorded in 2020 and 2021 for the same period. Based on previous years’ observations, it can be said that the situation can worsen if a business-as-usual scenario continues. Prevent Diwali trigger of a deadly smog episode: This year Diwali is falling relatively early in the season which means the warmer and windier conditions will help dilute the pollution that is staple of Diwali night celebrations. Unlike previous two years, the smoke from the farm stubble fires has not overwhelmed the air quality of the region yet and rains in early October have also kept the air relatively clean so far. Previous years’ data shows that Diwali night can add 300-600 µg/m3 of PM2.5 to Delhi’s air if the business-as-usual scenario continues. It remains to be seen if farm stubble fires will increase during and post-Diwali. Delayed start of the burning season in the past has resulted in concentration of burning activities, which can intensify the smoke-fall in the region. The next steps Says Roychowdhury: “This early winter alert is a wake-up call for more stringent pre-emptive and preventive measures to avert the smog episodes that cause excessive exposure and health risk during winter. The enforcement of the GRAP needs to be equally stringent with zero tolerance across Delhi and NCR. This requires preparedness in all concerned departments to ensure: All waste streams are collected, segregated and transported to prevent accumulation of waste in the open. Ongoing legacy waste management needs additional measures to ensure that dumpsites do not catch fire. Access to clean fuels in industry needs to be scaled up and units without air pollution control equipment or consent to operate are not allowed to function. Intensify public transport strategies and enforce parking controls and pricing as a demand management measure to reduce vehicle usage. Incentivise use of electric vehicles. Identify key commercial areas in Delhi and NCR towns that can be pedestrianized and be declared low emission zones. Dust control in construction sites and management of construction and demolition waste should be implemented with zero tolerance. Disclose information on truck movement based on the RFID data set to inform and control the intensity of the heavy duty traffic in the city. Identify all unpaved roads and dust hotspots for immediate action and paving. Stringent measures are needed to control fugitive dust and industrial waste burning and the mechanism needs to be put in place for all industrial areas. Step up action to provide access to LPG and electricity to all eateries and households to prevent burning of solid fuels. Ensure access to reliable electricity supply in all residential and commercial/industrial areas to minimise use of diesel generator sets. Make DISCOMS liable and accountable for the outages in Delhi-NCR.