Delhi world’s most polluted capital for fourth year in row

Among the most polluted cities, Rajasthan’s Bhiwadi fared the worst followed by Uttar Pradesh’s Ghaziabad, on the outskirts of Delhi.

Delhi has been ranked as the most polluted capital city in the world for the fourth consecutive year in an annual air quality report by a Swiss group released on Tuesday.

Annual average PM2.5 levels in Delhi increased by almost 15% in 2021 compared to the previous year. (HT Photo)

Annual average PM2.5 levels in Delhi increased by almost 15% in 2021 compared to the previous year — from 84.1 micrograms per cubic metre (mcm) to 96.4 mcm, the report said

The IQAir World Air Quality Report 2021 analysed data on PM2.5 levels from 6,475 cities in 117 countries and regions across the world. The level of PM2.5, or particulate matter less than 2.5 microns thick, is a key measure of air pollution because these particles enter the bloodstream and cause lasting health damage.

The prescribed annual average limit for PM2.5 in India is 40 mcm, according to ambient air quality standards of the Central Pollution Control Board. The World Health Organization standard for the pollutant is 5 mcm.

Dhaka in Bangladesh, N’Djamena in Chad, Dushanbe in Tajikistan and Muscat in Oman followed New Delhi on the list of most polluted national capitals. No country met the WHO standard and of the 6,475 cities, only 3.4% met the WHO limit.

Among the most polluted cities, Rajasthan’s Bhiwadi fared the worst followed by Uttar Pradesh’s Ghaziabad, on the outskirts of Delhi.

As many as 35 of the 50 topmost polluted cities in the world are in India, the report said. It also showed India’s annual average PM 2.5 levels rose to 58.1 mcm in 2021 — ending a three-year trend of declining concentration of the ultra-fine matter in the country’s air. In 2020, India’s average annual PM2.5 level was 51.9.

“India’s annual PM2.5 averages have now returned to pre-quarantine concentrations measured in 2019. India is also home to 11 of the 15 most polluted cities in Central and South Asia in 2021, with 48% of India’s cities exceeding the 50 micrograms per cubic metre mark, which is over 10 times the WHO guidelines,” said the report released by IQAir, a Switzerland -based air quality technology company.

Delhi also ranked third in the 15 most polluted regional cities in central and southeast Asia -- overall, it was fourth, with Chinese city Hotan recording worse figures. Rajasthan’s Bhiwadi topped this list with 106.2 average annual PM 2.5 levels. Besides Delhi, five more cities in the national capital region (NCR) made it to this list.

Ghaziabad was ranked two with average annual PM2.5 levels of 102 mcm; Noida ranked sixth with PM2.5 levels of 91.4; Baghpat ranked nine, Greater Noida 12, and Rohtak was number 13.

The average annual figures mask what has been an acute air quality crisis that hits much of north India, including Delhi and the National Capital Region cities entirely, during winter. Beginning somewhere around late October, a spell of bad air pushes the PM2.5 concentration to over 300mcm as smoke from farm fires in upwind states descend, choking millions of people in toxic smog.Pre-winter weather conditions of low wind speeds exacerbates the problem by trapping local pollutions along with the farm fire smoke.

The report is a wake-up call to governments and corporations because it once again highlights dangerously high levels of polluted air people are breathing across the country, said Avinash Chanchal, campaign manager at Greenpeace India, an advocacy group.

“We don’t need to invest in science to find the solutions to the air pollution crisis. We already know the solution, which includes promoting renewable energy for transportation and building infrastructure that encourages cycling, public transport usage and walking,” said Chanchal.

The increase in PM2.5 levels in 2021 over 2020 was inevitable since the country was in a lockdown during 2020 due to the Covid-19 pandemic, said Anumita Roy Chowdhury, executive director, research and advocacy at the Centre for Science and Environment, an advocacy group.

“We have seen that both in 2020 and 2021 that the problem has mostly been the winter months, which tips the average several times over the safe limit,” Roy Chowdhury said. “Looking at the data, three out of top four most polluted cities are in NCR, which once again highlights the need to have a regional action plan to curb pollution.”

Globally, only 3% of the cities and no country met the latest WHO standard for PM2.5.

“It is a shocking fact that no major city or country is providing safe and healthy air to their citizens according to the latest World Health Organization air quality guidelines,” said Frank Hammes, chief executive of IQAir. The report showed how much more work is required to provide clean air around the world, Hammes said.