Ggm’s AQI data dubious: Experts
GURUGRAM: The city’s air quality deteriorated drastically on Monday, with a thick haze shrouding it and reducing visibility to under 2km in most areas. However, according to the Central Pollution Control Board (CPCB), Gurugram’s air quality was ‘moderate’, with a reading of 174 on the daily air quality index (AQI) bulletin. Experts called the figure dubious.
According to a senior CPCB official, “Heavy, stagnant air, low temperatures and low wind speeds have collectively driven up pollution levels in the National Capital Region over the past week.” Delhi, Faridabad, Noida and Ghaziabad all recorded ‘severe’ air on Monday, exceeding 400 on the AQI. On Sunday too, while Delhi’s air was ‘very poor’ and Noida, Faridabad and Ghaziabad’s was in the ‘severe’ category, Gurugram recorded a reading of just 205 (‘poor’) on the AQI bulletin.
According to the only official air quality monitor at Vikas Sadan, data from which is used by the CPCB while publishing the AQI bulletin, the average PM2.5 level in the city stood at 174ug/m3 on Monday, the same numeric value as the day’s AQI bulletin. On Sunday, the average PM2.5 level over 24 hours was 205ug/ m3, also the same numeric value as the day’s AQI reading.
An accurate AQI is supposed to consider, in addition to PM2.5, concentrations of PM10, sulphur and nitrogen oxides, carbon monoxide and ozone. Moreover, the levels of PM2.5 recorded are discrepant with data from other sources. A second air quality monitor in Gwal Pahari, operated by the India Meteorological Department, recorded PM2.5 levels of 399ug/m3 and PM10 levels of 326ug/m3 on Monday. At least four other private monitors in the city, whose data was accessed by Hindustan Times, showed hazardous air quality on Monday. In Sector 44, PM2.5 levels touched 260ug/m3, while in DLF 2 they stood at 282ug/m3.
VK Shukla, head of the CPCB’S air quality lab, said he would look into the matter. “It is entirely a technical issue. There is no human intervention in the process, and the issue of fixing Gurugram’s air quality monitor has also been raised officially. I will take this up with the IT department,” he said on Monday.
Kuldip Singh, regional officer, Haryana State Pollution Control Board (HSPCB), did not provide an explanation for the disparate readings. Meeta Sarin, a scientist at the HSPCB who oversees the monitoring equipment, did not respond to multiple calls for comment. Sachin Panwar, an air quality expert who has been closely mapping the current pollution cycle, said, “According to our equipment, concentration of PM2.5 in the city was as high as 500ug/m3 in some areas on Monday, putting its air in the ‘severe’ category, same as other NCR cities.” This isn’t the first time that the air quality monitor in Vikas Sadan has given trouble. Hindustan Times has previously reported on a data transmission issue being faced by the monitor, due to which Gurugram was left out of the CPCB’S AQI bulletin on multiple days in September and October, at a time when air quality was worsening rapidly.
According to Namita Gupta, a city-based atmospheric pollution modeller and consultant, “The Vikas Sadan monitor has never been trustworthy. Instead, we use Delhi data as a reference point and other factors, such as weather, to triangulate the situation in Gurugram.” This derivative method is often more accurate than the monitor, she said.
Gupta added that it was irresponsible for the government agencies to publish data from this monitor, which was clearly inaccurate. “Government data should be trustworthy because it is what the majority of the population tends to believe,” she said.
LIGHT RAIN COULD WORSEN AQI IN DELHI
The air quality of Delhi breached the ‘severe’ mark once again on Monday, after a gap of nearly a month. The AQI of Delhi, as recorded by the CPCB, was 403 around 4pm Monday. It worsened to 411 by 7pm. Even though Delhi could receive light rain on Tuesday, experts warned that inadequate rain would push up moisture level, which in turn could make the air fouler.
“Inadequate rain — too little and too sporadic — won’t be able to wash away pollutants. Instead, increase in moisture level would push up pollution by increasing the holding capacity of the air and making it heavier,” D Saha, former head of the CPCB’S air quality lab, said.