Nearly three months after Newslaundry’s investigation revealed that almost every air pollution monitoring station in Delhi is either blocked by trees and buildings or too close to busy roads, leading to faulty data, a report by the Comptroller and Auditor General of India has confirmed our findings.
The report, tabled today, revealed that Delhi’s air quality index was “unreliable” because these stations’ locations were not in line with the siting criteria of the Central Pollution Control Board.
“The location of Continuous Ambient Air Quality Monitoring Stations (CAAQMS) did not fulfill the requirements laid down by the CPCB, indicating possible inaccuracies in the data generated by them, rendering the AQI values unreliable,” read the report.
CPCB guidelines indicate that the stations should be more than 20 metres away from nearby trees and unpaved roads/streets; and 200 metres away from pollution sources such roads or vehicular pollution.
During our investigation, Newlaundry physically verified 25 monitoring stations, which also included those of the CPCB, and found that 88 percent of them flouted the CPCB’s siting criteria. Newslaundry calculated the distance of each station from nearby barriers (trees or buildings) with a measuring tape, and detailed violations.
According to the report, the CAG in September 2020 physically verified 13 of the 24 stations under the Delhi Pollution Control Committee. All 13 were close to trees on multiple sides. “As per the CPCB guidelines, trees may also be sources of particulate matter in the form of detritus, pollen or insect parts,” read the report.
The CAG recommended that these stations either get suitably relocated or the barriers removed.
“The location of CAAQMS should be representative of average exposure over a geographic area. If the location of the instrument is such that it does not satisfy the physical requirements of monitoring stations, the data generated may be incorrect and thus, not be of much use in determining status and trends of level of pollutants,” the report said.
During its inspection, CAG officials found that stations at Anand Vihar and Wazirpur were located close to roads “catering to heavy vehicular traffic”. On the other hand, those at Civil Lines, Wazirpur, and Okhla were blocked by high-rise buildings and construction sites.
One of the oldest stations installed by the DPCC at the RK Puram site is surrounded by a full-grown banyan tree and other trees from multiple sides.
Experts had earlier explained that relocating these stations won’t be easy. A CPCB official told Newslaundry: “When [relocation] proposals are debated, then the next question emerges: Where can we find a new and better place for installation? Considering this, such discussions die down. Across the world, it’s impossible to ensure that stations fully comply with siting guidelines. Once you get the land for stations, you have to compromise with air quality data.”
Another official told Newlaundry that discussions on relocation kept happening but nothing concrete had materialised.
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