Delhi ranked world's most polluted capital in 2024: How cleaner air turned out to be hot gas

NEW DELHI: Delhi's skies are not always azure. They are more likely to be grey. And the air too is almost touchable, saturated as it is with pollutants. There appeared hope when the breathable PM2.5 pollutants and the larger PM10 showed a consistent decline but the trend was bucked in 2023.
The Central Pollution Control Board data shows that the annual average PM10 concentration in 2024 was 212.1 micrograms per cubic metre, the highest since 2019 when it was 217.9.Last year, the average annual PM10 level was also 3.5 times higher than the national ambient air quality standard (NAAQS) for PM10 and 14 times higher than the WHO safe guideline.
Average annual PM2.5 concentrations also declined from 2017 onward. But it rose from 98.3 micrograms per cubic metre in 2022 to 100.5 in 2023 and further to 104.5 in 2024. The annual average last year was 2.6 times the NAAQS norm for PM2.5 and 20.9 times the WHO safe standard.
Other pollutants such as nitrogen dioxide and ground-level ozone, which are severely harmful to human health, were measured to be beyond the permissible limits in several studies.
For most Delhiites, it is no surprise that the city occupied the first place as the most polluted capital in the world, as ranked by in the 6th Annual World Air Quality Report released in March last year. Another report on the Air Quality Life Index (AQLI) released in Aug last year by Energy Policy Institute at the University of Chicago revealed that Delhi residents were losing 7.8 years of their life to higher PM2.5 levels.
The problem with the city's fight for clean air is the lack of a long-term plan to reduce emissions at the source level. Delhi govt launches summer and winter action plans to deal with pollution, focusing on enforcement of norms on construction and transport sectors, ban on firecrackers, increase of green cover and dialogues with neighbouring states and the central govt. The plans also included emergency measures restricting vehicles on the road based on their number plate. In winters, govt relies on the Graded Response Action Plan, which bans construction and demolition and vehicles using non-cleaner fuels in the city, among other measures.
Asked about the frustrating air situation, AAP said in a statement, "Under Arvind Kejriwal's leadership, pollution levels have been steadily declining and Delhi's green cover has seen a remarkable transformation. From 20% in 2013, the green cover surged to 23.1% by 2021, making Delhi the national leader in per capita forest cover among cities. Fulfilling our promise to Delhiites, govt set an ambitious target of planting two crore saplings in five years — and achieved it within just four years. This is the Delhi model: action, results, and a greener future."
Among other measures, AAP said the various long-term and short-term interventions it initiated were "free spraying of stubble-decomposer, implementation of a strict EV Policy, onboarding of e-buses, deployment of electric autos and running online and offline public awareness campaigns".
Despite the plantation efforts, the city's forest cover reduced marginally from 195.4 sq km in 2021 to 195.3 sq km in 2023, according to India State Forest Report 2023, released in Dec 2024.
Sunil Dahiya, founder and lead analyst at think tank Envirocatalysts, agreed that over the past five years, there was some momentum in addressing air pollution in Delhi. "However," he added, "most of the measures were reactionary and what is still missing is a long-term, systematic and comprehensive approach to reducing the emission load. Isolated actions without a robust action plan are simply not enough." He added that the only way to systematically reduce air pollution is by targeting emissions at source, not just in Delhi but across the airshed through effective regional coordination.
With the burning of rice harvest stubble in the neighbouring states a big contributing factor to heavy pollution in the winter months, AAP, which now holds the helms in Punjab, claimed it was working "relentlessly" to tackle the crisis, noting that Punjab govt had reduced the number of farm fires from 71,000 in 2022, when it assumed power in the state, to 8,404 throughout the crop season in 2024. "Punjab's success was even acknowledged by Union agriculture minister Shivraj Singh Chouhan in the high-level multi-state ministerial on stubble burning in Oct 2024. At the same time, stubble burning surged in Uttar Pradesh, Rajasthan and Madhya Pradesh," the party said.
Professor Sachchida Nand Tripathi, dean, Kotak School of Sustainability, Indian Institute of Technology, Kanpur, said, "Delhi has a good number of continuous air quality monitoring stations, and the data from these stations should guide dynamic policymaking. But this hasn't happened. Apart from local sources, there are some pollution sources outside Delhi in the adjacent geography. However, these NCR districts lack an adequate number of monitoring stations. To assess the impact of nearby geography on air quality in Delhi, there is a need to complement data from the capital and adjacent districts with sensors."
Tripathi also pointed out that despite several studies proportioning the contribution of various sources in total pollution, the authorities were unable to take preventive and mitigating actions across the sectors. "Not much was done to plug the sources. However, we spent time, money and resources on optics like smog towers, mechanised road sweeping machines and anti-smog guns, which have very little impact on air quality," he said.
To deal with air pollution, there is a need to continuously refine research and develop technologies, said Tripathi, citing China, which he said "invested heavily in capacity building with the addition of modern laboratories and a high number of air quality monitoring stations and low-cost sensors".
A recent analysis of pollution in winter carried out by the Centre for Science and Environment concluded that the annual pollution trends had risen for two consecutive years despite the decline in stubble burning in the winter showed deeper systemic changes were required to cut the year-round emissions in Delhi and the surrounding region.