Delhi continues to rank among India’s most polluted cities for the seventh consecutive year. With an average PM 2.5 concentration of 91.8 micrograms per cubic metre, the World Air Quality Report 2024 from Swiss air quality technology firm IQAir identified Delhi’s status as the most polluted capital city globally, while India ranked fifth in 2024, down from third in 2023.
The report released on Tuesday has painted a grim picture for India as 13 of the world’s top 20 most-polluted cities are within the country. The report has picked Byrnihat in Assam as the most polluted city in the world.
The 13 Indian cities in the world’s top 20 most polluted cities are Byrnihat in Meghalaya, Delhi, Mullanpur (Punjab), Faridabad, Loni, New Delhi, Gurugram, Ganganagar, Greater Noida, Bhiwadi, Muzaffarnagar, Hanumangarh and Noida. Another four are in neighboring Pakistan, with one in China and Kazakhstan, respectively.
Delhi’s air pollution is a result of various factors, including high vehicular emissions, industrial discharges, construction dust, and seasonal stubble burning.
These sources, combined with geographical factors and rapid urbanization, create severe air quality problems that affect health and the environment. Delhi recorded consistently high pollution levels, with an annual average PM2.5 concentration of 91.6 micrograms per cubic metre, nearly unchanged from 92.7 micrograms per cubic metre in 2023. Delhi grapples with high air pollution year-round and the problem worsens in winter when unfavourable meteorological conditions, combined with vehicular emissions, paddy-straw burning, firecrackers and other local pollution sources, make the air quality hazardous.
According to the report, the country saw a 7 per cent decline in PM2.5 concentrations in 2024, averaging 50.6 micrograms per cubic metre, compared to 54.4 micrograms per cubic metre in 2023.
With all those improvements, six of the world’s 10 most polluted cities are still in India. Overall, 35 per cent of the Indian cities reported annual PM2.5 levels exceeding 10 times the WHO limit of 5 micrograms per cubic metre. Air pollution remains a serious health risk in India, reducing life expectancy by an estimated 5.2 years.
The only city outside of Asia featured on the list is N’Djamena, the capital of Chad in central Africa - which was named the country with the worst air pollution. Meanwhile the cities with the worst pollution in North America were all in California.
The report has relied on data from over 40,000 air quality monitoring stations at 8,954 locations in 138 countries, territories and regions. It was analysed by IQAir’s air quality scientists. Only seven countries have achieved the World Health Organisation’s (WHO) stringent air quality standards for 2024, and India is not one of them. These countries include Australia, New Zealand, the Bahamas, Barbados, Grenada, Estonia, and Iceland, according to data compiled by IQAir, a Swiss air quality monitoring firm.
Former WHO chief scientist and health ministry advisor Soumya Swaminathan said India has made progress in air quality data collection but lacks sufficient action.
“We have the data; we need action now. Some solutions are easy like replacing biomass with LPG. India already has a scheme for this, but we must further subsidise additional cylinders. The first cylinder is free, but the poorest families, especially women, should receive higher subsidies. This will improve their health and reduce outdoor air pollution,” she said.
In its monthly report, the Centre for Research on Energy and Clean Air (CREA) highlighted the severity of winter air pollution in India, revealing that 173 out of 238 cities recorded PM2.5 levels exceeding the National Ambient Air Quality Standards (NAAQS) of 40 µg/m³.
Aizawl, Mizoram recorded the lowest winter-average PM2.5 level at 7 µg/m³, making it the cleanest city in the analysis. Moreover, none of the 238 cities analysed met the World Health Organisation’s (WHO) guideline of 5 µg/m³, emphasising the scale of air quality challenges. ‘Winter’ refers to the period from October 1, 2024, to February 28, 2025 (winter 2024-25).
