A six-year reversal: Here’s how Delhi overtook neighbouring cities in pollution

With an annual average PM 2.5 concentration of 108.3 µg/m³, Delhi was second only to Meghalaya’s Byrnihat, which had a PM 2.5 concentration of 128.2 µg/m³, in the list of regional cities of South Asia in 2024. (see box). As per WHO standards, PM 2.5 levels should not exceed 5 µg/m3.

According to the report, the Capital fared worst in 2018 with average PM 2.5 levels at 113.5 µg/m³. But even then, the IQ Air report had noted, “Of the cities included in South Asia, it is interesting to note that although Delhi typically receives most media coverage as one of the world’s ‘polluted capitals, ’ the Indian capital ‘only’ ranks 10th for annual PM 2.5 concentration. Other cities across Northern India and Pakistan have a higher recorded annual PM 2.5 level, with nearby Gurugram (Gurgaon) narrowly resulting in the highest annual concentration of any global city recorded here during 2018.”

From 2018 to 2019, even as pollution levels decreased from 113.5 µg/m³ to 98.6 µg/m³, Delhi ranked as the fourth most polluted regional city in Central and South Asia among 147 locations, implying that other NCR cities — including Gurgaon, Faridabad and Bhiwadi — were ahead in terms of improvement in air quality.

While Ghaziabad fared worse and emerged as the most polluted city in the region in 2019, the number of Delhi-NCR cities in the top 15 most polluted regional cities also increased from seven to ten. India doubled its monitoring network and introduced the National Clean Air Programme (NCAP) — a long-term strategy to reduce air pollution — the same year.

Delhi ranked ninth on this list in 2020 and was at the third spot in 2021, 2022, and 2023.

In 2023, Delhi overtook other NCR cities to emerge as the most polluted in the region. The other NCR cities on the list were Greater Noida, Muzaffarnagar, Gurgaon, and Dadri. In 2024, Bhiwadi and Faridabad were among the NCR cities on the list.

In 2019, IQ Air, in its report, had called the NCAP “promising”. However, the latest report noted that despite such a programme, challenges to reduce pollution levels persisted. It said this was because of “inconsistent policy implementation and inadequate infrastructure”.

Air pollution experts have also noted this disparity, urging for better implementation of NCAP.

Sunil Dahiya, lead analyst and founder of Envirocatalysts, a Delhi-based think tank, said, “While Delhi has consistently made headlines as one of the most polluted cities globally over the past years, systematic actions to reduce emission loads at the source have largely remained confined to drafts within various action plans. These plans have suffered from poor implementation and a lack of long-term, systematic approaches. This is evident in persistently high air pollution levels in the city and surrounding regions, despite significant steps like the introduction of BS-VI fuel and advanced technologies in the transportation sector.”

“This winter, however, has shown a shift, with regulatory bodies like the Commission for Air Quality Management (CAQM) and the Honourable Supreme Court taking steps to fix accountability and demonstrate intent to reduce emissions at the source. While this marks a small but positive start, achieving significant and lasting improvements will require a drastic overhaul in how air pollution is regulated and governed. This includes strengthening initiatives like the National Clean Air Programme (NCAP) to ensure sustained and impactful action,” he added.