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Delhi: Most Polluted Capital in World Says 2021 World Air Quality Report 

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For fourth consecutive year in 2021, Delhi world's most polluted capital in world

The 2021 World Air Quality Report released by the Swiss organization IQAir reveals that the National Capital Territory (NCT) of Delhi, India, is the most polluted capital in the world for the fourth consecutive year in 2021.

The report finds that only 3% of cities and no single country met the latest World Health Organization’s (WHO) Particulate Matter (PM) 2.5 annual air quality guidelines. The new guideline was released in September 2021 and cut the existing annual PM2.5 guideline value from 10 µg/m3 to 5 µg/m3.

  • Dhaka, the capital of Bangladesh was second on the list of capital cities in terms of annual average PM2.5 concentrations, while N’Djamena, the capital of Chad, was third.
  • Previously, Delhi topped a list in 2020, 2019, and 2018.
  • India was placed 5th in the Most Polluted countries in the word whereas Bangladesh was placed in 1st followed by Chad and Pakistan.
  • No country met the latest WHO air quality guideline for PM2.5 in 2021.

Note: Sources of PM2.5 – include internal combustion engines, power generation, industrial processes, agricultural processes, construction, and residential wood and coal burning. The most common natural sources for PM2.5 are dust storms, sandstorms, and wildfires.

Key Facts of the Report:

i.According to the report, data from publicly accessible air quality monitoring stations increased in 2021. Significant increases were seen in India, New Zealand, and Canada, in particular.

ii.In the Central and South Asia region, including India, Iran, Nepal, Pakistan, Sri Lanka, Bangladesh, Afghanistan, and Tajikistan, around 50 cities were ranked in terms of PM2.5 levels on the list of the “World’s Most Polluted Cities” in 2021.

  • It revealed that the region together housed for 46 of the top 50 polluted cities, in which Bhiwadi, Alwar district (Rajasthan)in India topped the list of the ‘world’s most polluted cities’ in 2021; Ghaziabad (Uttar Pradesh),India – second; and Hotan, China – came third. 
  • The only two cities that met updated WHO PM2.5 guideline were Zhezqazghan and Chu (Kazakhstan).

iii. India houses 11 of the 15 most polluted cities in Central and South Asia in 2021. 

iv.Delhi saw a 14.6% increase in PM2.5 concentrations in 2021 with levels rising to 96.4 µg/m3 (micrograms per cubic meter) from 84 µg/m3 in 2020. 

v.No cities in India met the WHO air quality guideline of 5 µg/m3.

vi.In 2021, 48% of India’s cities exceeded 50 µg/m3, or more than 10 times the WHO guideline.

  • Researchers discovered that being exposed to PM2.5 increases the likelihood of catching the virus as well as experiencing more severe symptoms, including death, if infected. 
  • Researchers also revealed that India’s annual average PM2.5 levels reached 58.1 µg /m3 in 2021, ending a three-year trend of improving air quality. India’s annual PM2.5 averages have now returned to pre-quarantine concentrations measured in 2019.

For fourth consecutive year in 2021

Top 10 countries with worst air quality- 2021

RankCountryAverage Air Quality Index (AQI)


About the World Air Quality Report:

i.The 2021 World Air Quality Report is based on PM2.5 air pollution data from ground-based air quality monitoring stations in 6,475 cities in 117 countries, regions and territories.
ii.Of the air quality monitoring stations included in this report, 44% were operated by governmental agencies, while the remainder represent monitoring stations managed by citizen scientists, non-profit organizations and companies.