New Delhi emerged as the world’s most polluted Capital for the third straight year in 2020, according to IQAir, a Swiss group that measures air quality levels based on the concentration of PM2.5 (particulate matter with a diameter of less than 2.5 micrometres, which can enter the lungs and the bloodstream).

The report is based on PM2.5 data from 106 countries and uses ground-based monitoring stations operated by governmental agencies, local residents, non-profit organisations and companies.

However, the report suggested that air quality in India improved in 2020 due to the countrywide lockdown, which led to a substantial decrease in traffic and industry activities.

“The year 2020 brought an unexpected dip in air pollution,” Frank Hammes, Chief Executive Officer of IQAir said. “In 2021, we will likely see an increase in air pollution due to human activity again. We hope this report will highlight that urgent action is both possible and necessary to combat air pollution, which remains the world’s greatest environmental health threat.”

In 2020, New Delhi’s average annual concentration of PM2.5 in a cubic meter of air was 84.1, the study said, making it the 10th most polluted city in the world. Among capitals in the world, Dhaka ranked second with a PM2.5 concentration of 77.1. Nine out of the 10 capitals were of Asian countries, the report showed.

Most polluted Capitals in the world. (Image source: IQAir 2020 World Air Quality Report)

India also accounted for 35 of the 50 most polluted cities in the world, with all major cities of the National Capital Region, featuring on the list.

IQAir said that 63% of Indian cities reported an improvement in air quality, as compared to 2019, but the data also showed that PM2.5 levels witnessed a sharp rise as the coronavirus lockdown was relaxed. For example, in Delhi the PM2.5 levels dipped to as low as 35.5 in August, but rose to 157.3 in December.

Month-wise PM2.5 levels in major Indian cities (Image source: IQAir 2020 World Air Quality Report)