Delhi’s AQI row: At Anand Vihar, water sprinklers circle air quality monitors

Around 1.30 pm on Monday, the mud-covered ground near the Anand Vihar air quality monitoring station was damp and freshly watered. A faint dampness hung in the air as tankers moved around the roads near the bus terminal. This is one of Delhi’s most polluted zones, classified as a “severe” hotspot by the Central Pollution Control Board (CPCB). But this week, it is not just the pollution levels that are under scrutiny, it’s how they are being recorded.

A viral video shared by AAP leader Saurabh Bharadwaj has triggered controversy over the Delhi Government and Municipal Corporation of Delhi (MCD)’s air quality management practices. The clip shows MCD water tankers spraying mist directly around the Anand Vihar monitoring station. Bharadwaj alleged that this was “deliberate data management” to artificially bring down air quality index (AQI) readings, calling it “pollution data fraud.”

When The Tribune visited the ground on Monday, sprinkling was indeed taking place close to the monitoring equipment. Manoj Kumar, an e-rickshaw driver who parks near the Metro exit adjoining the station, said, “A vehicle was here some time ago. Water is being sprinkled at regular intervals.”

A water supplier in the area confirmed that “four to five vehicles” have been operating in and around the bus terminal over the past week. Vinay, a Rapido driver, said the activity has been ongoing since mid-October.

Data from the CPCB station shows a noticeable variation in particulate matter levels during the day. Between 11 am and noon, PM2.5 levels were 172 µg/m³ and PM10 levels 351 µg/m³, both in the “very poor” range.

By the next hour, when sprinklers were reportedly active, readings dropped to 120 µg/m³ and 263 µg/m³, respectively. Later in the afternoon, levels rose again to 132 µg/m³ (PM2.5) and 315 µg/m³ (PM10).

While fluctuations in pollution data are common due to weather and traffic changes, experts say sprinkling water near monitors can distort real-time air quality readings.

“Water sprinkling reduces air pollution levels in that limited geography for a few minutes or hours,” explained Sunil Dahiya, lead analyst and founder of Envirocatalysts, a Delhi-based think tank.

BJP and MCD officials have rejected the charge, saying water sprinkling is part of routine dust-control measures under the Graded Response Action Plan (GRAP), which mandates steps such as mechanical sweeping and water spraying when air pollution levels rise.

“GRAP does not say sprinkling should be done around monitors. If you sprinkle too close, the readings are manipulated — it gives a false sense of cleaner air,” Dahiya said.

Dahiya said while daytime pollution tends to be lower due to higher temperature and wind speed, water spraying further reduces measured particulate levels by increasing moisture content in the air.

Experts warn that such manipulation can have serious implications.

“It is dangerous because people rely on AQI data to take health precautions — whether to step out, wear masks or keep children indoors. If the readings are artificially lowered, it can mislead the public and downplay the real health risk,” Dahiya said.

Though Dahiya said this is the first known instance in Delhi, he recalled reports from Loni in Ghaziabad last year, where the local authorities allegedly used “smoke guns” to spray water near monitoring sites. Similar claim was reported in Agra last year after the city’s air quality data showed “unexpectedly good readings” post-Diwali.