Air we breathe: Delhi tops list of most polluted capitals for 3rd year

Delhi was also ranked the 10th most polluted of the 50 cities from where data was analysed. Of the top 30, 22 were located in India.

Delhi was the most polluted capital city in the world in 2020 for the third consecutive year, according to a report by a Swiss group that ranked cities based on their air quality measured in terms of the levels of ultrafine particulate matter (PM 2.5) that can enter the organs and cause lasting damage.

A commuter crossing Vande Mataram Marg on a foggy morning in New Delhi. (Sanchit Khanna/ Hindustan Times)

The World Air Quality Report, 2020 by IQAir that was released globally on Tuesday showed that Delhi recorded an annual average PM 2.5 concentration of 84.1ug/m3.

Delhi was also ranked the 10th most polluted of the 50 cities from where data was analysed. Of the top 30, 22 were located in India. In the overall city ranking, China’s Hotan topped the list while Ghaziabad in NCR was ranked second. All cities between rank 2 and 14 were Indian.

The WHO states that while no level of PM2.5 exposure is free from adverse health effects, annual average exposure below 10 μg/m³ minimises risks. The ambient air quality standards in India prescribes an annual average of 40ug/m3 as the safer limit for PM 2.5.

According to the report, data was sourced from government monitoring and privately owned stations.

Delhi has been at the centre of India’s air pollution crisis for years now, which particularly worsens every winter season. The landlocked demography of the national capital also puts it at a disadvantage, as winds carrying pollutants from neighbouring states also impacts its air. Experts have time and again pointed out that sharing a common air shed with the Indo-Gangetic Plains, the issue of Delhi’s pollution cannot be tackled in isolation, and the governments will have to come up with a holistic plan to bring down emissions in the entire region.

According to the region wise analysis for central and south Asia, the report showed that top 14 of the 15 most polluted cities were in India with Ghaziabad ranked one and Delhi ninth. Ten of the top 14 most polluted cities in the region were in Delhi-NCR.

The report said improvement in air quality during the Covid-19 lockdown was only short-lived.

“Cities with higher average PM2.5 levels and denser populations tended to observe the most significant PM2.5 reductions from Covid-19 lockdown measures. Delhi (-60%), Seoul (-54%) and Wuhan (-44%), for example, all observed substantial drops during their respective lockdown periods as compared to the same time frame in 2019,” the report that was released on Tuesday said.

“By the end of 2020, rebounds in industry and transport resulted in smaller average annual reductions. In Delhi, the overall reduction after the Covid-19 lockdown reopening was 15%, Seoul (South Korea) it was 16%, in Wuhan it was 18%. In Los Angeles, there was an overall increase was 15%,” it said.

Air pollution caused an estimated 54,000 premature deaths in New Delhi in 2020, according to another study by IQAir and Greenpeace Southeast Asia released recently.

The report released Tuesday also highlighted how Delhi’s air quality during the onset of winters, starting October, worsens because of external factors such as crop residue burning carried out in the neighbouring states of Punjab, Haryana and Uttar Pradesh. As the burning of crop stubble peaked last year, Delhi’s PM2.5 levels averaged 144 ug/m3 in November, and 157 ug/m3 in December, the findings show.

“Delhi’s most polluted months correlate with the agricultural burning season, which spans October through December. During these months, the average pollution exposure often exceeds the WHO (World Health Organization) annual target 10 ug/m3) by more than 14 times,” the report said.

Anumita Roychowdhury, executive director (research and advocacy), Centre for Science and Environment (CSE), said most cities in the world saw an unprecedented reduction in the pollution levels last year because of the global Covid-19 pandemic.

“We are reducing pollution concentrations, but Delhi still has a long way to go. Cities bouncing back from the lockdown is an indicator of the high impacts of local and regional pollution. We need to strengthen our reform strategy to address vehicular pollution, emissions from industry and power plants, etc.,” Roychowdhury said.

IQAir is a Swiss air quality technology company that specialises in developing air quality monitoring and air cleaning products. It also operates AirVisual, a real-time air quality information platform.

The report acknowledged contributions by Greenpeace, the Centre for Research on Energy and Clean Air (CREA) and the UN environment programme.