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City air clean as per CPCB data, experts sceptical

PUBLISHED ON NOV 30, 2019 07:18 PM IST

Gurugram The city recorded a reading of 78 on the Central Pollution Control Board’s (CPCB) air quality index (AQI) bulletin at 4pm, with ‘satisfactory’ air quality for the second consecutive day. However, data of 12-hour averages from private monitors in the city ranked the city’s air between ‘moderate’ and ‘poor’ levels.

The AQI reading on Friday was 84, as per the CPCB data.

Air quality monitors at Sector 30, South City, Golf Course Road and Sector 58 recorded average 12-hour readings of 180 (‘moderate’), 223 (‘poor’), 217 (‘poor’) and 200 (‘moderate’), respectively.

Air quality experts in the city said good wind speeds, averaging around 10-12 kmph during the day, were successful in dispersing accumulated pollutants. However, they said it was unlikely that the AQI was in the ‘satisfactory’ category for the whole day, considering pollution levels in the morning spiked due to the fog and low minimum temperatures.

“The CPCB data shows a 24-hour average of pollution levels and it is not real-time. Pollution levels in the evening, as per private monitors, touched the upper-end of the ‘moderate’ category,” said Sachin Panwar, an air quality expert.

However, officials of the state and central pollution boards said that the figures are indicative of the city’s pollution levels. A CPCB official said, “The data relayed from air quality monitors in different cities is reflected in the bulletin as it is.”

The monitor at Vikas Sadan measures pollution levels in the area within a five-kilometre radius, which includes Rajiv Chowk, Civil Lines and sectors 44 to 48. Experts have, several times in the past, noted that the AQI for this area is highly unlikely to be representative for all of Gurugram, which is spread across 738 square kilometres.

Experts have also doubted that the analysers of the monitor may not be calibrated often. “The particulate matter (PM) analysers of the Vikas Sadan monitor might not be calibrated often and thus, report faulty data,” said Panwar, adding that sensors need regular maintenance.

HSPCB officials, however, maintained that calibration is done every six months.

On Saturday, Delhi and Faridabad recorded ‘moderate’ rating on the CPCB’s bulletin. Noida, Greater Noida and Ghaziabad had ‘poor’ air quality, according to Saturday’s AQI bulletin.

Saturday also saw the season’s first thick fog with the visibility dropping to 200 metres around 7am, as per the India Meteorological Department (IMD). The minimum temperature on Saturday also reduced to 12 degrees Celsius from 12.5 degrees Celsius on Friday and is expected to drop further to 11 degrees Celsius on Sunday.

Experts predicted a rise in pollution levels on Sunday, predicting a reading at the upper end of the ‘moderate’ or lower-end of the ‘poor’ category, mainly due to lower wind speed.

The maximum temperature on Saturday fell to 23.7 degrees Celsius from 24 degrees Celsius on Friday. It is likely to be around 23 degrees Celsius on Sunday, as per the IMD.

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