The actual magnitude of toxic smog and air pollution that engulfed the country's capital Delhi after Diwali was much more serious than the levels recorded in government data. A recent and scientific analysis by 'Centre for Research on Energy and Clean Air' (CREA), a prestigious independent organization doing research on environment and clean air, has revealed very shocking things. According to this detailed report of CREA, due to missing data of very fine pollutant particles i.e. PM 2.5 from many major air quality monitoring stations of the capital on Diwali night, the average pollution level of Delhi appeared much lower than the reality. If these missing data had been recorded, the city's average pollution level would actually have been 49 percent higher. CREA researchers explained that if these missing readings from the monitoring stations had been recorded even at the upper limit of just 1,000 micrograms per cubic metre, Delhi's 24-hour average PM 2.5 level would have jumped from 269 to 400 micrograms per cubic metre. This figure is almost seven times higher than India's national daily standard (60 micrograms per cubic metre) and more than 26 times the safe health limit set by the World Health Organization (WHO) (only 15 micrograms per cubic metre), indicating extremely lethal conditions for human lungs. The system's 1000 microgram limit became a technical hurdle: CREA opened layers of data after CPCB's statement. This important analysis has come just a day after the official clarification given by the Central Pollution Control Board (CPCB), in which the board had accepted its technical limitations. CPCB had said that the sensors and systems installed in their monitoring stations are set (calibrated) to measure particulate matter up to a maximum of 1,000 micrograms per cubic meter. Due to this technical reason, when the pollution due to smoke from fireworks crossed this limit on Diwali night, the systems were not able to record readings above this limit for several hours and the Board excluded these missing readings while calculating the Average Air Quality Index (AQI). CREA experts say that if these average levels of 400 micrograms per cubic meter had also been included in the calculations, Delhi's official AQI, which was recorded at 344 i.e. 'very poor' category on Monday, would have jumped straight to very close to the 'severe' category. It is noteworthy that the AQI of any city is calculated on the basis of a total of eight major pollutants including PM 2.5 and PM 10, and after the pollution peaked on Diwali night, the data remained missing from the CPCB portal for several hours. Pollution crossed 3000 at DPCC stations, a frightening level of 3,744 was recorded at 2 pm in Mundka. On one hand, there was lack of data in the central bulletin of CPCB, on the other hand, the raw data of Delhi Pollution Control Committee (DPCC), which directly operates 43 stations out of total 60 monitoring stations in the capital, exposed the real picture of pollution. DPCC stations also recorded data on Diwali night that crossed the limit of 1,000 micrograms per cubic metre. These data show that in at least 11 areas of Delhi, the hourly level of PM 2.5 had gone above 2,000 micrograms per cubic meter, while in four highly sensitive areas this figure even crossed 3,000. According to the report of the English newspaper 'The Times of India' (TOI), the DPCC data has revealed the sensational fact that at 2 am on Monday night, the level of PM 2.5 in Mundka area of West Delhi had reached an incredible 3,744 micrograms per cubic meter. This level was no less than that of a gas chamber, but surprisingly, CPCB did not share the PM 2.5 data of Mundka from 12 midnight to 4 am in its public bulletin. Out of 1416 hours of data, 255 readings were missing: Understand the complete mathematics of CREA's 'Sensitivity Analysis'. CPCB releases daily AQI by collecting data from all 60 monitoring stations of Delhi, one of which has been closed due to technical reasons for the last few months. In its study, CREA closely examined the hourly PM 2.5 data of the remaining 59 active stations between 4 pm on November 8 and 4 pm on November 9, which directly matches the CPCB's 24-hour average bulletin of November 9. A total of 1,416 hours of potential data (24 hours × 59 stations) were analyzed during this period, which revealed the shocking fact that out of the total 1,416 data, 255 data i.e. 18 percent of the data were completely missing. In its 'sensitivity analysis', CREA replaced these 255 missing data points with CPCB's maximum prescribed limit of 1,000 micrograms per cubic metre, resulting in a massive increase of 49 per cent in the average level. The report said that based on the available data at 1 am on November 9, the maximum level was seen to be 584, but after replacing the missing data with 1,000, the level reached 825 at 2 am and 824 micrograms per cubic meter at 3 am. However, the researchers also clarified that this analysis does not prove that all 255 missing data were missed simply because of crossing the threshold of 1,000, but that the model was designed to understand how missing data can alter the actual picture of a city's air quality.
