New Delhi has been ranked as the world's most polluted capital city for a second consecutive year, followed by Dhaka (Bangladesh), N'Djamena (Chad), Dushanbe (Tajikistan), and Muscat (Oman).
Of the 15 most polluted cities in Central and South Asia in 2021, 12 were in India.
New Delhi saw a 14.6 percent increase in PM2.5 concentration in 2021, 96.4 Ig/m3, up from 84 Ig/m3 in 2020.
The annual PM2.5 concentration averages in 48 per cent of India's cities, exceeded 50 Ig/m3 or more than 10 times the World Health Organization's (WHO) air quality guidelines.
Crop burning is common in India, especially in the rice farms near Delhi during the winter months.
During crop burning season, smoke is responsible for up to 45 percent of pollution in the city.
These startling facts came to light on Tuesday, 22 March, in the 2021 World Air Quality Report according to which only three percent of cities and no single country has met the latest WHO PM2.5 annual air quality guidelines.
The report analyses PM2.5 air pollution measurements from air monitoring stations in 6,475 cities in 117 countries, regions, and territories.
IQAir's 2021 World Air Quality Report is the first major global air quality report based on updated annual WHO air quality guidelines for PM2.5.
The new guidelines were released in September 2021 and cut existing annual PM2.5 guideline values from 10 Aug/m 3 to 5 Aug/m 3.
Fine particle pollution, known as PM2.5, is commonly accepted to be the most harmful, widely-monitored air pollutant and has been found to be a major contributing factor to health effects such as asthma, stroke, heart and lung diseases.
PM2.5 leads to millions of premature deaths every year. The key findings include no country met the latest WHO air quality guidelines for PM2.5 in 2021.
Only the territories of New Caledonia, US Virgin Islands and Puerto Rico met the updated WHO PM2.5 air quality guidelines.
Only 222 out of 6,475 global cities in the report met the updated WHO PM2.5 guidelines.
At least 93 cities in the report had annual PM2.5 concentrations exceeding 10 times the WHO PM2.5 guidelines.
Of 174 Latin America and the Caribbean cities, only 12 (seven percent) have met the WHO PM2.5 guidelines.
Of 1,887 Asian cities, only four (0.2 percent) have met the updated WHO PM2.5 guidelines.
Of the 1,588 cities in Europe, only 55 (three percent) have met the WHO PM2.5 guidelines.
The report covered 2,406 cities in the US and found that an average PM2.5 concentrations rose from 9.6 Aug/m 3 to 10.3 Aug/m 3 in 2021 compared to 2020.
"It is a shocking fact that no major city or country is providing safe and healthy air to their citizens according to the latest WHO air quality guidelines," said Frank Hammes, CEO of IQAir.
"This report underscores just how much work remains to be done to ensure that everyone has safe, clean and healthy air to breathe. The time for action is now," he added.
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