Context

Twenty-one of the world's 30 cities with the worst air pollution are in India, according to data compiled in IQAirAirVisual's 2019 World Air Quality Report, with six in the top ten.

About:

• The ranking is based on levels of "fine particulate matter," known as PM2.5, which pose the greatest risk to human health. These tiny particles are 2.5 micrometres or smaller.
• The WHO warns, however, that the microscopically smaller particles of PM2.5 are even more dangerous to human health because they have the ability to "penetrate the lung barrier and enter the blood system."

Mapping the most polluted cities:

• • Ghaziabad, a satellite city of the capital New Delhi in northern Uttar Pradesh state, is ranked as the world's most polluted city, with an average PM 2.5 concentration measurement of 110.2 in 2019.
  • Hotan in China was the second most polluted. Delhi, the poster city of pollution, stood at the sixth position for 2019. All six most polluted cities of India that feature in the top 10 are from the National Capital Region.
  • Noida, Gurugram, Greater Noida and Bandhwari are the other cities in the top 10 list. 
  • Total 21:In total, 21 out of 30 world's most polluted cities of 2019 are from India. The 21 Indian cities, in the order of their ranking, are, Ghaziabad, Delhi, Noida, Gurugram, Greater Noida, Bandhwari, Lucknow, Bulandshahr, Muzaffarnagar, Baghpat, Jind, Faridabad, Coraut, Bhiwadi, Patna, Palwal, Muzaffarpur, Hisar, Kutail, Jodhpur and
  • Capital cities:Among capital cities, Delhi remains the world's most polluted capital city, with an annual average PM2.5 of 98.6 ppm in 2019.

Country-wise data:

• • According to country-wise data, India ranked fifth in the world's most polluted countries with Bangladesh on top of the list followed by Pakistan, Mongolia and Afghanistan.
  • Bangladesh was the most polluted country with an average PM2.5 concentration of 83.3 ppm.
  • In terms of most polluted cities, however, Indian and Chinese cities occupy almost all the spots.
  • Among the top 200 most polluted cities, 178 are from these two countries comprising nearly 90% of the list.
  • All 30 most polluted cities are from the Asian continent.

Has India improved?

• • There seems to be a silver lining in the appalling levels of pollution reported for 2019.
  • Except for Nagpur, every other city in India registered a decrease in pollution levels in 2019 compared to 2018 levels.
  • India saw widespread improvements in PM2.5 levels in 2019, compared to the year prior as a result of economic slowdown, favourable meteorological conditions, as well as more dedicated efforts towards cleaning the air.
  • As a weighted average based on the available data, national air pollution decreased by a remarkable 20% from 2018 to 2019.
  • India stands fifth in the most polluted countries list with average pollution levels of 58.1 ppm. Pakistan was the second most polluted, followed by Mongolia in the third spot.
  • Mainland China stood at the 11 positions in the polluted countries list.
  • Regionally, South Asia, Southeast Asia, and Western Asia carry the highest burden of fine particulate matter pollution overall.

What is Particulate Matter?

Particulate matter is categorized as PM 2.5 and PM 10.

The report revealed that India still has a relatively limited air quality monitoring network given its population size, with many communities and highly populated cities without access to real-time information. There is a need for some urgent actions and steps to correct the situation now, otherwise, it will be too late to manage anything.