Delhi has cleanest winter in 5 years, but is most polluted city in NCR: Study
The winter season is the most polluted time of the year, with unfavourable meteorological conditions trapping pollutants close to the surface, including calm winds, low temperature and fog.
Delhi logged its cleanest winter season in five years with respect to PM2.5 particulates, an analysis by the Centre for Science and Environment (CSE) has revealed. However, among cities in the National Capital Region (NCR), Delhi had the highest concentration of PM2.5 particulates, the study said, while Noida had the lowest.
“The city-wide winter average for Delhi stood at 160 micrograms per cubic metre (µg/m³) for the October-January period, which is the lowest level recorded since wide-scale monitoring started in 2018-19. The PM2.5 level, computed by averaging monitoring data from 36 continuous ambient air quality monitoring stations (CAAQMS) located in the city, was 17% lower compared to the seasonal average of 2018-19 winter. Based on the subset of the 10 oldest stations in Delhi, there is an improvement of almost 20%,” the analysis said.
In comparison, Delhi’s PM2.5 levels were 171 µg/m³in 2021-22, 186 µg/m³ in 2020-21, 173 µg/m³ in 2019-20 and 193 µg/m³ in 2018-19, the study said.
However, this is still considerably higher than the 24-hour standard national ambient air quality standards of 60 µg/m³, or the annual standard of 40 µg/m³.
The winter season is the most polluted time of the year, with unfavourable meteorological conditions trapping pollutants close to the surface, including calm winds, low temperature and fog. Anumita Roychowdhury, executive director, research and advocacy at CSE said this winter, the conditions were not as harsh, with Delhi also being aided by emergency-based action based on pollution forecasts.
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“There was also heavy and extended rain in the early phases of the season that prevented smog episodes from building up and also lowered the seasonal average,” she said.
The analysis, released on Monday, also found that 12 out the 13 pollution hotspots in the Capital had shown a marked improvement in PM2.5 levels compared to the average pollution levels recorded over the previous three seasons, thanks to a combination of favourable meteorology and forecast-based action, with the only outlier hotspot being RK Puram.
It said hotspots located in north and east Delhi were the most polluted locations in the city. “Jahangirpuri was the most polluted neighbourhood with October-January average PM 2.5 level of 201 µg/m³, while Okhla-Phase 2 was the least polluted, recording an average of 167 µg/m³,” it said.
To be sure, PM 2.5 is not the only criteria to measure air pollution, with Central Pollution Control Board’s Air Quality Index (AQI) including eight prominent pollutants — PM2.5, PM10, ozone, sulphur dioxide (so2), nitrogen dioxide (NO2), carbon monoxide (CO), lead (Pb) and ammonia (NH3). Experts, however, consider PM2.5 to be the most dangerous pollutant, as these tiny particles, around thirty times smaller than a human hair, can easily enter the bloodstream, and prolonged exposure to high concentrations are linked with respiratory diseases and even heart problems, as per global studies.
Across NCR, Noida was the least polluted amongst the major NCR cities, recording an average of 124 µg/m³ this winter. Greater Noida recorded an average of 143 µg/m³, Faridabad and Gurugram recorded an average PM 2.5 concentration of 133 µg/m³, while Ghaziabad’s average was a point lower at 132 µg/m³.
“Delhi continues to remain the most polluted among the cities and towns of NCR. This downward trend will have to be sustained with much stronger action on vehicles, industry, waste burning, construction, solid fuel and biomass burning to meet the clean air standard,” Roychowdhury said.
Avikal Somvanshi, senior programme manager at the Urban Lab at CSE, said while the average concentration across NCR towns varied this winter owing to the contribution of local sources differing in each region, high pollution episodes were still synchronised despite large distances. “Overall, Delhi and the neighbouring cities of Faridabad, Ghaziabad, Gurugram and Noida were relatively more polluted than other smaller NCR towns, though not significantly. This is the challenge of this landlocked region that demands even stronger action,” Somvanshi said.
The analysis also found that while Delhi only recorded a single smog episode this winter, peak pollution levels were still fairly high, touching 401 µg/m³ on November 3, 2022.
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“As is the global practice, at least three continuous days of severe AQI is considered a smog episode. In previous winters, such episodes have been recorded as lasting over 6-10 days, but this winter, only one smog episode was recorded from January 6-9, 2023. The average daily intensity of this smog stood at 287 µg/m³. This winter was the first in the last five years when both Diwali and late December (around Christmas) did not experience a smog episode,” the analysis said.