Dustopia: PM10 spirals in sepia-tinted Delhi

Delhi’s pollution levels also deteriorated to the “poor” zone on Tuesday, with the average AQI at 254

The skies of the National Capital Region (NCR) were shrouded in a dusty haze on Tuesday morning, owing to westerly winds bringing in dust from Rajasthan, making for a highly polluting day for Delhi, with the average PM 10 concentration touching 941 micrograms per cubic metre (µg/m3) at 10 am — nearly 10 times the safe standard.

A thick layer of dust is seen engulfed around the city at Yamuna River, in New Delhi on Tuesday. (Sanjeev Verma/HT PHOTO)

The highest concentration of PM10 recorded in the city was 3,826 µg/m3 at Jahangirpuri at 8 am, followed by Aurobindo Marg (2,565 µg/m3 at 11 am). Delhi’s pollution levels also deteriorated to the “poor” zone on Tuesday, with the average Air Quality Index (AQI) at 254 — a spike over 80 points from Monday’s average reading of 162 (moderate).

VK Soni, scientist at the India Meteorological Department (IMD) and part of the Commission for Air Quality Management (CAQM), said the deterioration in air quality began from 4am onwards, when the PM 10 levels were 140µg/m3. Thereafter, the average hourly PM 10 concentration touched 312 µg/m3 at 5am, 637 µg/m3 at 6 am, 805µg/m3 at 7 am and 940 µg/m3 at 10 am, before dipping to 920 µg/m3 at 11 am. By 7pm, the PM 10 levels had dropped to 342 µg/m3.

“The spike in pollution levels lasted for nearly six hours, with the peak recorded at 10am. While it began to dip after that, the pollution levels were still over three times the safe limit,” said Soni.

This summer pollution episode brings back into the spotlight what is now a perennial environmental crisis for the Capital: hazardous air pollution levels. Most of it occurs in winter, when weak winds trap local pollutants and farm fires bring in toxic smoke, but it is now also routine in summers, when the city is gripped by dust storms of the sort recorded on Tuesday.

At fault is the erosion of the Aravalli range, which once acted as a natural barrier between the northwestern deserts, and rampant construction work within the city with little regard for mandatory dust mitigation compliances. And Tuesday’s occurrence serves as another reminder of why it is critical that NCR takes care of its lifeline, rather than prey on it.

Across Delhi’s 40 ambient air quality monitoring stations, the average PM 10 concentration crossed levels of over 1,000 µg/m3 at most locations before 12 pm. The peak at north Delhi’s industrial area of Bawana was 1,439 µg/m3; it was 1,530 µg/m3 at the relatively green area of south Delhi’s Dr Karni Singh Shooting Range. In east Delhi’s Patparganj, it touched 1,807 µg/m3 and was 1,881 µg/m3 at southeast Delhi’s Okhla; 1,232 µg/m3 at southwest Delhi’s Najafgarh and 1,661 µg/m3 at Dwarka’s sector 8, indicating the spread of dust was quite consistent across the Capital.

Mukesh Khare, professor at Indian Institute of Technology, Delhi, said such high levels of PM 10 for Delhi were unusual, with Jahangirpuri’s high reading likely coming from local factors, in combination with the dust-laden westerly winds.

“It is an industrial location and also sees trucks pass near the station. There is also likely to be construction dust impacting from a nearby site, however, such high levels at Aurobindo Marg are a surprise and one may have to inspect the source there,” Khare said.

A review meeting on air quality, held by the CAQM, said this spike in pollution was temporary, with the body not imposing any restrictions under the Graded Response Action Plan (Grap).

“Dust raising strong winds were flowing across Haryana and Delhi since the early hours of Tuesday morning, which increased particulate matter concentration significantly. Winds from the northwest and west direction blew with an average wind speed of 6-18 km/hr and gusty winds of 30-45 km/hr were also recorded. After comprehensively reviewing the air quality scenario, this was noted to be an exceptional episodic event, which has led to continual dispersion of dust in the ambient air over entire Delhi-NCR. This is likely to improve in the next 24 to 48 hours, with rain also expected on May 18,” CAQM said in a statement, adding that it is keeping a close tab on the air quality.

Vignesh Prabhu, senior associate at the Center for Study of Science, Technology and Policy (CSTEP), an environmental think tank, said the presence of distressing levels of dust in Delhi’s air is not unfamiliar, particularly during the summer season.

“The sudden rise in particulate pollution in the summer season is mostly due to excessive heat and the transportation of dust from arid regions. Moreover, in recent years, there has been an increase in the frequency and density of dust storms over Delhi that can be attributed to multiple factors, including an increase in land degradation, which needs immediate attention. While PM10 exposure can irritate the eyes, nose, and throat, it is PM2.5 that is of greater concern, as it can deeply penetrate the lungs, posing a very serious health risk,” he said.

“In addition, we need to creating green zones on open land and restricting cutting of trees in the Aravalli ranges around Delhi,” he said.