According to a survey conducted in nearly 6,500 worldwide cities, no country managed to meet the World Health Organization's (WHO) air quality standard in the year 2021. Even after experiencing a sharp drop in pollution levels due to lockdowns during the pandemic, most cities have begun to see a turnaround in smog levels.

For those unaware, WHO guidelines recommend that the annual readings of hazardous particles in the air, known as PM2.5, can reach up to five micrograms per cubic meter. However, this was changed last year after the agency announced that even low concentrations can be harmful to health.

The recent probe cites that only 3.4% of the surveyed cities met the air quality standard in 2021, while 93 cities had PM2.5 levels that were 10 times higher than the permissible scale.

With a 14.6% increase in PM2.5 levels rising to 96.4 g/m3, India's capital New Delhi continued to top the ranking as the most polluted city in the world, with the country's pollution levels surpassing even that of last year.

Other Indian cities of Bhiwadi (Rajasthan) and Ghaziabad (Uttar Pradesh) are also claimed to be some of the world's most polluted cities, followed by Hotan, the northwestern region of Xinjiang, China, with average PM2.5 readings of more than 100 micrograms, primarily induced by sandstorms.

While Bangladesh remained the most polluted country in the world, as it had the previous year, African country Chad ranked second for the first time.

Notably, despite being home to the world's third most polluted city, China's national pollution ranking has fallen to 22nd from 14th the previous year. Its average readings also demonstrated significant improvement, with 32.6 micrograms, given that the country has been actively fighting a battle against pollution and pushing for sustainability.

Source credits –

https://www.asiaone.com/world/no-country-met-who-air-quality-standards-2021-data