Delhi has become the world’s most polluted city, with Kolkata a close second.

According to a new report, Air Pollution and Health in Cities, released by the Health Effects Institute’s (HEI) State of Global Air Initiative, in terms of average annual population-weighted PM 2.5 exposure, Delhi and Kolkata are the world’s two most polluted cities.

Five Chinese cities were among the top twenty. Mumbai came in 14th place. There are no other Indian cities in the top 20. However, Beijing had the highest disease burden from a PM 2.5-related ailment, with 124 attributable deaths per 100,000 people. Delhi ranked sixth, with 106 deaths per 100,000 people, and Kolkata ranked eighth, with 99.

Many global cities exceeded World Health Organization (WHO) standards for both PM 2.5 and NO2. According to the report, Delhi’s average PM 2.5 exposure in 2019 was 110 micrograms per cubic meter, 22 times the WHO benchmark of 5 micrograms per cubic meter. The moderate exposure in Kolkata was 84 micrograms per cubic meter.

According to the report, in 2019, exposure to pollutants exceeded WHO’s standard in 86% of the more than 7,000 cities included in the report, affecting approximately 2.6 billion people. The average NO2 exposure in Shanghai was 41.6 micrograms per cubic meter, followed by Moscow in Russia (40.2 micrograms per cubic meter). The WHO recommends a NO2 exposure level of 10 micrograms per cubic meter.

In terms of absolute numbers, the study determined that PM 2.5 exposure caused 29,900 deaths in Delhi in 2019, 21,380 deaths in Kolkata, and 16,020 deaths in Mumbai. In comparison, PM 2.5 exposure caused 26,270 deaths in Beijing in 2019.